Fixed Assets and Lease Commitments [Abstract] Fixed Assets and Lease Commitments [Abstract] Schedule of Fixed Assets Property, Plant and Equipment [Table Text Block] Schedule of Aggregate Future Minimum Payments for Operating Leases Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block] Debt Disclosure [Abstract] Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Credit Facility Senior Unsecured Credit Facility [Member] Represents the senior unsecured credit facility entered into by the entity during the reporting period. Term Loan Facility Senior Unsecured Term Loan [Member] Senior Unsecured Term Loan Debt Instrument Debt Instrument [Line Items] Maximum borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity Principal Amount at Maturity Debt Instrument, Face Amount Maximum borrowing capacity, additional amount Line of Credit Facility, Maximum Borrowing Capacity, Additional Amount Line of Credit Facility, Maximum Borrowing Capacity, Additional Amount Line of credit facility amount outstanding Long-term Line of Credit Weighted average interest rate Debt, Weighted Average Interest Rate Term loan outstanding Long-term Debt Weighted average interest rate on amount outstanding Long-term Debt, Weighted Average Interest Rate, at Point in Time Commitment fee amount Line of Credit Facility, Commitment Fee Amount Noncontrolling Interest [Abstract] Noncontrolling Interest [Table] Noncontrolling Interest [Table] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Minimum Minimum [Member] Maximum Maximum [Member] Noncontrolling Interest [Line Items] Noncontrolling Interest [Line Items] Term of conditional right put interest Term Of Conditional Right to Put Interest Term Of Conditional Right to Put Interest Changes in redeemable non-controlling interests during the period Redeemable Noncontrolling Interest [Roll Forward] -- None. No documentation exists for this element. -- Balance, as of January 1, Redeemable Noncontrolling Interest, Equity, Carrying Amount Changes attributable to consolidated products Redeemable Noncontrolling Interest Change in Redemption Value Increase (decrease) in redeemable non-controlling interests during the period as a result of a change in the redemption value. Transfers to Other liabilities Noncontrolling Interest, Decrease from Transfers to Other Liabilities Noncontrolling Interest, Decrease from Transfers to Other Liabilities Transfers from non-controlling interests Payments for Repurchase of Redeemable Noncontrolling Interest Changes in redemption value Noncontrolling Interest, Decrease from Redemptions Noncontrolling Interest, Decrease from Redemptions Balance, as of December 31, Stockholders' Equity Note [Abstract] Stockholders' Equity Stockholders' Equity Note Disclosure [Text Block] Income Tax Disclosure [Abstract] Reconciliation of beginning and ending amount of unrecognized tax benefits Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward] Balance, as of January 1, Unrecognized Tax Benefits Additions based on current year tax positions Unrecognized Tax Benefits, Increase Resulting from Current Period Tax Positions Additions based on prior years’ tax positions Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions Reductions related to lapses of statutes of limitations Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations Additions (reductions) related to foreign exchange rates Unrecognized Tax Benefits, Increase (Decrease) Related to Foreign Exchange Rates The gross amount of additions (reductions) related to foreign exchange rates resulting from settlements with taxing authorities. Balance, as of December 31, Goodwill and Intangible Assets Disclosure [Abstract] Schedule of Goodwill [Table] Schedule of Goodwill [Table] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] Acquired Client Relationships (Net) Customer Relationships [Member] Goodwill Goodwill [Line Items] Goodwill impairment Goodwill, Impairment Loss Intangible amortization expense Amortization of Intangible Assets Intangible future amortization expense in 2018 Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months Intangible future amortization expense in 2019 Finite-Lived Intangible Assets, Amortization Expense, Year Two Intangible future amortization expense in 2020 Finite-Lived Intangible Assets, Amortization Expense, Year Three Intangible future amortization expense in 2021 Finite-Lived Intangible Assets, Amortization Expense, Year Four Intangible future amortization expense in 2022 Finite-Lived Intangible Assets, Amortization Expense, Year Five Definite-lived and indefinite-lived intangibles impairments Asset Impairment Charges Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Changes in goodwill Goodwill [Roll Forward] Balance, as of January 1, Goodwill Foreign currency translation Goodwill, Foreign Currency Translation Gain (Loss) Balance, as of December 31, Equity Method Investments and Joint Ventures [Abstract] Schedule of Aggregate Purchase Price Allocation for Investments Schedule of Purchase Price Allocation of Equity Method Investments [Table Text Block] Schedule of Purchase Price Allocation of Equity Method Investments [Table Text Block] Schedule of Changes in Equity Method Investments in Affiliates Equity Method Investments [Table Text Block] Schedule of Financial Information for Affiliates Accounted for Under the Equity Method Valuation and Qualifying Accounts [Abstract] Valuation and Qualifying Accounts Disclosure [Table] Valuation and Qualifying Accounts Disclosure [Table] Valuation Allowances and Reserves Type [Axis] Valuation Allowances and Reserves Type [Axis] Valuation Allowances and Reserves [Domain] Valuation Allowances and Reserves [Domain] Income Tax Valuation Allowance Valuation Allowance of Deferred Tax Assets [Member] Other Allowances Allowance for Notes Receivable [Member] Valuation and Qualifying Accounts Valuation and Qualifying Accounts Disclosure [Line Items] Reconciliation of beginning and ending balances of valuation and qualifying accounts Movement in Valuation Allowances and Reserves [Roll Forward] Balance Beginning of Period Valuation Allowances and Reserves, Balance Additions Charged to Costs and Expenses Valuation Allowances and Reserves, Additions for Charges to Cost and Expense Additions Charged to Other Accounts Valuation Allowances and Reserves, Additions for Charges to Other Accounts Deductions Valuation Allowances and Reserves, Deductions Balance End of Period Income Tax Provision [Table] Income Tax Provision [Table] Schedule reflecting information of income tax attributable to controlling and noncontrolling interests. Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Controlling interests Parent [Member] Non-Controlling Interests Noncontrolling Interest [Member] Income tax provision Income Tax [Line Items] -- None. No documentation exists for this element. -- Current tax Current Income Tax Expense (Benefit) Intangible-related deferred taxes Deferred Income Tax Expense Related to Intangibles The component of income tax expense for the period representing the tax effect of the difference between amortization of intangibles for book purposes and amortization of intangibles for tax purposes. Other deferred taxes Deferred Other Tax Expense (Benefit) Deferred taxes Deferred Income Tax Expense (Benefit) Provision for income taxes Income Tax Expense (Benefit) Income before income taxes (controlling interest) Income (Loss) from Continuing Operations before Income Taxes Attributable to Parent This element represents the income or loss from continuing operations, before income taxes, which is attributable to the controlling interest. Effective tax rate attributable to controlling interests Income Tax Expense from Controlling Interest to Pretax, Income from Continued Operations Attributable to Controlling Interest Ratio A ratio calculated by dividing the amount of income tax expense attributable to the controlling interest by pretax income from continuing operations attributable to the controlling interest. Goodwill and Acquired Client Relationships Goodwill and Intangible Assets Disclosure [Text Block] Revenue(1) Equity Method Investment, Summarized Financial Information, Revenue Net income(1) Equity Method Investment, Summarized Financial Information, Net Income (Loss) Assets Equity Method Investment, Summarized Financial Information, Current Assets Liabilities and Non-controlling interests Equity Method Investment, Summarized Financial Information, Current Liabilities Undistributed earnings from equity method affiliates Retained Earnings, Undistributed Earnings from Equity Method Investees Fair Value Disclosures [Abstract] Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Fair Value, Hierarchy [Axis] Fair Value, Hierarchy [Axis] Fair Value, Measurements, Fair Value Hierarchy [Domain] Fair Value Hierarchy [Domain] Level 2 Fair Value, Inputs, Level 2 [Member] Measurement Basis [Axis] Measurement Basis [Axis] Fair Value Measurement [Domain] Fair Value Measurement [Domain] Portion at Fair Value Measurement Portion at Fair Value Measurement [Member] Carrying Amount Reported Value Measurement [Member] Fair Value Estimate of Fair Value Measurement [Member] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Senior notes Notes Payable, Fair Value Disclosure Convertible securities Convertible Debt, Fair Value Disclosures Fair Value Measurements Fair Value Disclosures [Text Block] Schedule of Income Tax Provision Attributable to Controlling and Non-Controlling Interests Schedule of Components of Income Tax (Expense) Benefit by Controlling and Noncontrolling interests [Table Text Block] Tabular disclosure of the components of income tax expense attributable to controlling and non-controlling interests for each year presented including, income before income taxes and effective tax rate attributable to controlling interests. Schedule of Consolidated Provision for Income Taxes Schedule of Components of Income Tax Expense (Benefit) [Table Text Block] Schedule of Components of Income before Income Taxes Schedule of Income before Income Tax, Domestic and Foreign [Table Text Block] Schedule of Effective Income Tax Rate Computed Using Income before Income Taxes and Applying U.S. Federal Income Tax Rate Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Schedule of Components of Deferred Tax Assets and Liabilities Schedule of Deferred Tax Assets and Liabilities [Table Text Block] Schedule of Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits Summary of Income Tax Contingencies [Table Text Block] Affiliate Equity [Abstract] Affiliate Equity [Abstract] Affiliate Equity [Table] Affiliate Equity [Table] Affiliate Equity [Table] Related Party [Axis] Related Party [Axis] Related Party [Domain] Related Party [Domain] Controlling Interest Affiliated Entity [Member] Non- controlling Interests Affiliate Equity Expense Affiliate Equity [Line Items] [Line Items] for Affiliate Equity [Table] Controlling interest Compensation Expenses Related to Affiliate Equity Represents the compensation expenses related to Affiliate equity. Non-controlling interest Affiliate Equity Compensation Expense, Attributable to Noncontrolling Interest Affiliate Equity Compensation Expense, Attributable to Noncontrolling Interest Total Affiliate Equity Compensation Expense, Including Portion Attributable to Noncontrolling Interest Affiliate Equity Compensation Expense, Including Portion Attributable to Noncontrolling Interest Unrecognized Affiliate Equity Expense Unrecognized Affiliate Equity Expense [Abstract] Unrecognized Affiliate Equity Expense [Abstract] Controlling Interest Unrecognized Compensation Expenses Related to Affiliate Equity Attributable to Controlling Interest Unrecognized Compensation Expenses Related to Affiliate Equity Attributable to Controlling Interest Remaining Life Affiliate Equity, Unrecognized Compensation Expense, Weighted Average Period of Recognition Affiliate Equity, Unrecognized Compensation Expense, Weighted Average Period of Recognition Non-Controlling Interest Affiliate Equity Unrecognized Compensation Expense, Attributable to Noncontrolling Interest Affiliate Equity Unrecognized Compensation Expense, Attributable to Noncontrolling Interest Disclosure of Compensation Related Costs, Share-based Payments [Abstract] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Award Type [Axis] Award Type [Axis] Award Type [Domain] Equity Award [Domain] Stock Options Employee Stock Option [Member] Share-based Compensation Arrangement by Share-based Payment Award Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Assumptions used to determine fair value of options granted Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract] Dividend yield Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate Expected volatility Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate Risk-free interest rate Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate Expected life of options (in years) Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term Forfeiture rate Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions Forfeiture Rate Represents the expected rate the entity will cancel the stock option awards due to nonfulfillment of certain conditions of equity-based compensation arrangements. Segment Reporting [Abstract] Schedule of Revenue and Fixed Assets, net of the Company by Geographic Location Schedule of Revenue from External Customers and Long-Lived Assets, by Geographical Areas [Table Text Block] Retirement Benefits [Abstract] Benefit Plans Pension and Other Postretirement Benefits Disclosure [Text Block] Schedule of Changes in Goodwill Schedule of Goodwill [Table Text Block] Schedule of Changes in, and the Components of, Acquired Client Relationships Schedule of Intangible Assets by Major Class [Table Text Block] Tabular disclosure of intangibles assets, in total and by major class, including the gross carrying amount and accumulated amortization. A major class is composed of intangible assets that can be grouped together because they are similar, either by their nature or by their use in the operations of a company. Subsequent Events [Abstract] Subsequent Event [Table] Subsequent Event [Table] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Subsequent Event Subsequent Event [Member] Class of Stock [Axis] Class of Stock [Axis] Class of Stock [Domain] Class of Stock [Domain] Common Stock Common Stock [Member] Share Repurchase Program [Axis] Share Repurchase Program [Axis] Share Repurchase Program [Domain] Share Repurchase Program [Domain] January 2018 Plan January 2018 Plan [Member] January 2018 Plan Subsequent Event [Line Items] Subsequent Event [Line Items] Stock repurchase program, number of shares authorized (in shares) Stock Repurchase Program, Number of Shares Authorized to be Repurchased Stock repurchase plan, number of remaining shares to be repurchased (in shares) Stock Repurchase Program, Remaining Number of Shares Authorized to be Repurchased Shares repurchased (in shares) Treasury Stock, Shares, Acquired Average price (in usd per share) Treasury Stock Acquired, Average Cost Per Share Deferred Tax Assets Deferred Tax Assets, Net [Abstract] State net operating loss carryforwards Deferred Tax Assets, Operating Loss Carryforwards, State and Local Foreign loss carryforwards Deferred Tax Assets, Operating Loss Carryforwards, Foreign Tax benefit of uncertain tax positions Deferred Tax Assets, Tax Benefit on Uncertain Tax Positions Represents the tax benefit as of the balance sheet date of the amount of future tax deductions arising from uncertain tax positions. Deferred compensation Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits Foreign tax credits Deferred Tax Assets, Tax Credit Carryforwards, Foreign Accrued expenses Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Accrued Liabilities Total deferred tax assets Deferred Tax Assets, Gross Valuation allowance Deferred Tax Assets, Valuation Allowance Deferred tax assets, net of valuation allowance Deferred Tax Assets, Net of Valuation Allowance Deferred Tax Liabilities Deferred Tax Liabilities, Gross [Abstract] Intangible asset amortization Deferred Tax Liabilities, Intangible Assets Non-deductible intangible amortization Deferred Tax Liabilities, Nondeductible Intangible Assets, Amortization Represents the tax effect of future book amortization of intangibles that do not qualify for step-up and amortization for tax purposes. Convertible securities interest Deferred Tax Liabilities, Convertible Securities Interest The cumulative amount of the estimated future tax effects attributable to the difference between the tax basis of convertible securities interest and the basis of convertible securities interest computed in accordance with generally accepted accounting principles. Deferred income Deferred Tax Liabilities, Tax Deferred Income Other Deferred Tax Liabilities, Other Total deferred tax liabilities Deferred Tax Liabilities, Gross Deferred income tax liability (net) Deferred Tax Liabilities, Net Marketable Securities [Abstract] Investments in Marketable Securities Marketable Securities [Table Text Block] Senior Bank Debt Debt Disclosure [Text Block] Subsequent Events Subsequent Events [Text Block] Segment and Geographic Information Segment Reporting Disclosure [Text Block] Senior Notes Senior Notes [Member] Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] 2024 Senior Notes Senior Notes Four Point Two Five Percent Due 2024 [Member] [Member] Senior Notes Four Point Two Five Percent Due 2024 [Member] 2025 Senior Notes Senior Notes Three Point Five Zero Percent Due 2025 [Member] Senior Notes 3.50% Due 2025 Debt Instrument Par value (in millions) Stated coupon Debt Instrument, Interest Rate, Stated Percentage Accounting Policies [Abstract] Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Use of Estimates Use of Estimates, Policy [Policy Text Block] Principles of Consolidation Consolidation, Policy [Policy Text Block] Cash and Cash Equivalents Cash and Cash Equivalents, Policy [Policy Text Block] Receivables Receivables, Policy [Policy Text Block] Investments in Marketable Securities Marketable Securities, Policy [Policy Text Block] Fair Value Measurements Fair Value Measurement, Policy [Policy Text Block] Fixed Assets Property, Plant and Equipment, Policy [Policy Text Block] Leases Lessee, Leases [Policy Text Block] Acquired Client Relationships and Goodwill Goodwill and Intangible Assets, Policy [Policy Text Block] Issuance Costs Debt, Policy [Policy Text Block] Derivative Financial Instruments Derivatives, Policy [Policy Text Block] Contingent Payment Arrangements Business Combinations Policy [Policy Text Block] Income Taxes Income Tax, Policy [Policy Text Block] Foreign Currency Translation Foreign Currency Transactions and Translations Policy [Policy Text Block] Concentration of Credit Risk Concentration Risk, Credit Risk, Policy [Policy Text Block] Revenue Recognition Revenue Recognition, Policy [Policy Text Block] Earnings Per Share Earnings Per Share, Policy [Policy Text Block] Share-Based Compensation Plans Share-based Compensation, Option and Incentive Plans Policy [Policy Text Block] Recent Accounting Developments New Accounting Pronouncements, Policy [Policy Text Block] Fair Value of Financial Instruments Fair Value of Financial Instruments, Policy [Policy Text Block] Share-Based Compensation Expense Allocated Share-based Compensation Expense Tax Benefit Employee Service Share-based Compensation, Tax Benefit from Compensation Expense Accumulated Other Comprehensive Income (Loss) [Table] Accumulated Other Comprehensive Income (Loss) [Table] Foreign currency translation adjustment Accumulated Foreign Currency Adjustment Including Portion Attributable to Noncontrolling Interest [Member] Change in net realized and unrealized gain (loss) on derivative securities Accumulated Net Gain (Loss) from Cash Flow Hedges Including Portion Attributable to Noncontrolling Interest [Member] Change in net unrealized gain (loss) on investment securities Accumulated Net Investment Gain (Loss) Including Portion Attributable to Noncontrolling Interest [Member] Accumulated Other Comprehensive Income (Loss) Accumulated Other Comprehensive Income (Loss) [Line Items] Pre-Tax Other Comprehensive Income (Loss), before Tax Tax Benefit (Expense) Other Comprehensive Income (Loss), Tax Net of Tax Other Comprehensive Income (Loss), Net of Tax Schedule of Equity Method Investments [Table] Schedule of Equity Method Investments [Table] Investment, Name [Axis] Investment, Name [Axis] Investment, Name [Domain] Investment, Name [Domain] 2016 New Seven Equity Method Investments New Seven Equity Method Investments 2016 [Member] New Seven Equity Method Investments 2016 Equity Method Investee Equity Method Investee [Member] Acquired Client Relationships Under Equity Method Investments Acquired Client Relationships of Equity Method Investments [Member] Represent the description related to acquired client relationships of the entity's equity method investments. Schedule of Equity Method Investments [Line Items] Schedule of Equity Method Investments [Line Items] Fair value assumptions, average projected growth rate Fair Value Assumptions, Average Projected Growth Rate Fair Value Assumptions, Average Projected Growth Rate Fair value assumptions, discount rate for asset based fees Fair Value Assumptions, Discount Rate For Assets Based Fees Fair Value Assumptions, Discount Rate For Assets Based Fees Fair value assumptions, discount rate for performance based fees Fair Value Assumptions, Discount Rate For Performance Fees Fair Value Assumptions, Discount Rate For Performance Fees Fair value assumptions, market participant tax rate Fair Value Assumptions, Market Participant Tax Rate Fair Value Assumptions, Market Participant Tax Rate Impairment of equity method investment Equity Method Investment, Other than Temporary Impairment Equity method and cost method impairments Equity Method and Cost-method Investments, Other than Temporary Impairment Equity Method and Cost-method Investments, Other than Temporary Impairment Revenue of equity method investment affiliate investment Net income of equity method affiliate investment Earnings Per Share [Abstract] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Antidilutive Securities [Axis] Antidilutive Securities [Axis] Antidilutive Securities, Name [Domain] Antidilutive Securities, Name [Domain] Stock options and restricted stock units Employee Stock Options and Restricted Stock [Member] Employee Stock Options and Restricted Stock [Member] Antidilutive Securities Excluded from Computation of Earnings Per Share Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive securities excluded from computation of earnings per share (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Fair Value Inputs, Liabilities, Quantitative Information [Table] Fair Value Inputs, Liabilities, Quantitative Information [Table] Liability Class [Axis] Liability Class [Axis] Fair Value by Liability Class [Domain] Fair Value by Liability Class [Domain] Contingent payment arrangements Contingent Payment Arrangements [Member] Represents contingent payment arrangements of the entity. Affiliate equity obligations Obligations to Related Parties [Member] Represents the obligations of the entity towards related parties. Valuation Technique [Axis] Valuation Technique [Axis] Valuation Technique [Domain] Valuation Technique [Domain] Discounted cash flow Discounted Cash-Flow Valuation Technique [Member] Represents the discounted cash flow technique used to measure fair value. Quantitative information for Level 3 Fair Value Measurements Liabilities Fair Value Inputs, Liabilities, Quantitative Information [Line Items] Fair value liabilities Financial and Nonfinancial Liabilities, Fair Value Disclosure Growth rates Fair Value Inputs Growth Rates Represents percentage of assumed growth rates, used as an input to measure fair value. Discount rates Fair Value Inputs, Discount Rate Schedule of Tax Effects Allocated to each Component of Other Comprehensive Income Comprehensive Income (Loss) [Table Text Block] Schedule of Components of Accumulated Other Comprehensive Income, Net of Taxes Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Numerator Net Income (Loss) Available to Common Stockholders, Basic [Abstract] Net income (controlling interest) Net Income (Loss) Attributable to Parent Interest expense on convertible securities, net of taxes Interest on Convertible Debt, Net of Tax Net income (controlling interest), as adjusted Net Income (Loss) Available to Common Stockholders, Diluted Denominator Weighted Average Number of Shares Outstanding, Diluted [Abstract] Average shares outstanding - basic (in shares) Weighted Average Number of Shares Outstanding, Basic Effect of dilutive instruments: Incremental Weighted Average Shares Attributable to Dilutive Effect [Abstract] Stock options and restricted stock units (in shares) Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements Junior convertible securities (in shares) Incremental Common Shares Attributable to Dilutive Effect of Conversion of Debt Securities Average shares outstanding - diluted (in shares) Weighted Average Number of Shares Outstanding, Diluted Operating Loss Carryforwards [Table] Operating Loss Carryforwards [Table] Income Tax Authority [Axis] Income Tax Authority [Axis] Income Tax Authority [Domain] Income Tax Authority [Domain] State and Local Jurisdiction State and Local Jurisdiction [Member] Foreign Tax Authority Foreign Tax Authority [Member] Tax Period [Axis] Tax Period [Axis] Tax Period [Domain] Tax Period [Domain] Expire over a 20-year period Expire Over Twenty Year Period [Member] Expire Over Twenty Year Period Valuation Allowance by Deferred Tax Asset [Axis] Valuation Allowance by Deferred Tax Asset [Axis] Deferred Tax Asset [Domain] Deferred Tax Asset [Domain] Valuation Allowance, Operating Loss Carryforwards Valuation Allowance, Operating Loss Carryforwards [Member] Operating Loss Carryforwards [Line Items] Operating Loss Carryforwards [Line Items] Provisional one-time net benefit from changes in U.S. tax laws Tax Cuts And Jobs Act of 2017, Incomplete Accounting, Provisional Income Tax Expense (Benefit) Tax Cuts And Jobs Act of 2017, Incomplete Accounting, Provisional Income Tax Expense (Benefit) Net income tax benefit resulting from re-measurement of Company's deferred tax assets and liabilities Tax Cuts and Jobs Act of 2017, Change in Tax Rate, Income Tax Expense (Benefit) Tax Cuts and Jobs Act of 2017, Change in Tax Rate, Income Tax Expense (Benefit) Provisional amount for repatriation tax liability Tax Cuts And Jobs Act of 2017, Incomplete Accounting, Transition Tax For Accumulated Foreign Earnings Provisional Income Tax (Expense) Tax Cuts And Jobs Act of 2017, Incomplete Accounting, Transition Tax For Accumulated Foreign Earnings Provisional Income Tax (Expense) Operating loss carryforwards Operating Loss Carryforwards State net operating loss carryforwards, expiration period Operating Loss Carryforwards, State and Local Expiration Period The period (in years) over which the state net operating loss carryforwards included in total operating loss carryforwards shall expire. Foreign operating loss carryforwards, expiration period Operating Loss Carryforwards, Foreign, Expiration Period Operating Loss Carryforwards, Foreign, Expiration Period Operating loss carryforwards, valuation allowance Increase in valuation allowance, state net operating loss carryforward and realized deferred tax benefit Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount Amount of temporary difference due to repatriation of earnings from sale or liquidation of subsidiary Undistributed Earnings of Foreign Subsidiaries Unrecognized tax benefits that, if recognized, would affect effective tax rate Unrecognized Tax Benefits that Would Impact Effective Tax Rate Accrued income tax interest and related charges Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued Schedule of Available-for-sale Securities [Table] Schedule of Available-for-sale Securities [Table] Major Types of Debt and Equity Securities [Axis] Major Types of Debt and Equity Securities [Axis] Major Types of Debt and Equity Securities [Domain] Major Types of Debt and Equity Securities [Domain] Equity Securities Equity Securities [Member] Summary of Available-for-sale Securities Schedule of Available-for-sale Securities [Line Items] Available-for-Sale Available-for-sale Securities [Abstract] Cost Available-for-sale Equity Securities, Amortized Cost Basis Unrealized Gains Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax Unrealized Losses Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax Fair Value Available-for-sale Securities Trading Trading Securities [Abstract] Cost Trading Securities, Cost Unrealized Gains Trading Securities, Unrealized Holding Gain Unrealized Losses Trading Securities, Unrealized Holding Loss Fair Value Trading Securities Commitment and Contingencies [Table] Commitment and Contingencies [Table] Represents commitments and contingencies of the entity. Consolidated Affiliates Consolidated Entities [Member] Scenario [Axis] Scenario [Axis] Scenario, Unspecified [Domain] Scenario, Unspecified [Domain] Scenario, Forecast Scenario, Forecast [Member] Commitments and Contingencies Commitment and Contingencies [Line Items] -- None. No documentation exists for this element. -- Co-investment commitments in partnership Investment Commitment, Amount The amount that the entity agreed to co-invest in certain investment partnerships where the entity serves as the general partner. Other commitments Other Commitment Other commitment, expected payments Other Commitment Expected Payments Other Commitment Expected Payments Other commitments, present value of expected payments Other Commitment Present Value of Expected Payments Other Commitment Present Value of Expected Payments Change in Equity Method Investments in Affiliates [Roll Forward] Change in Equity Method Investments in Affiliates [Roll Forward] Change in Equity Method Investments in Affiliates Balance, January 1, Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures Equity method earnings Income (Loss) from Equity Method Investments Before Amortization of Intangibles Income (Loss) from Equity Method Investments Before Amortization of Intangibles Equity method intangible amortization and impairments Equity Method Investment, Intangible Asset Amortization Equity Method Investment, Intangible Asset Amortization Distributions of earnings from equity method investments Proceeds from Equity Method Investment, Distribution Investments Payments to Acquire Equity Method Investments Foreign currency translation Equity Method Investment, Realized Gain (Loss) on Foreign Currency Translation Equity Method Investment, Realized Gain (Loss) on Foreign Currency Translation Other Equity Method Investment, Other Increase (Decrease) Equity Method Investment, Other Increase (Decrease) Balance, December 31, Schedule of Carrying Value of Convertible Securities Schedule of Convertible Securities [Table Text Block] Tabular disclosure of the carrying amount and fair value of convertible securities. Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Table] Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Table] Investment Type [Axis] Investment Type [Axis] Investment Type Categorization [Domain] Investments [Domain] Private equity Private Equity Funds [Member] Other funds Other Funds [Member] Investments held in other funds. Other investments Other than Securities Investment [Member] Parent NAV of investments at fair value Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items] Fair Value Alternative Investment, Fair Value Disclosure Unfunded Commitments Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments Life of funds (in years) Fair Value, Investments, Entities That Calculate NAVs, Life of Fund Fair Value, Investments, Entities That Calculate NAVs, Life of Fund Quarterly Financial Information Disclosure [Abstract] Schedule of Quarterly Results of Operations Quarterly Financial Information [Table Text Block] Schedule of Property, Plant and Equipment [Table] Property, Plant and Equipment [Table] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Domain] Property, Plant and Equipment, Type [Domain] Building and leasehold improvements Building and Leasehold Improvements [Member] Represents the long lived, depreciable structure held for productive use, including office, production, storage and distribution facilities and depreciable asset that is an addition or improvement to assets held under a lease arrangement. Software Software and Software Development Costs [Member] Equipment Office Equipment [Member] Furniture and fixtures Furniture and Fixtures [Member] Land, improvements and other Land and Land Improvements [Member] Fixed assets Property, Plant and Equipment [Line Items] Fixed assets, at cost Property, Plant and Equipment, Gross Accumulated depreciation and amortization Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Fixed assets, net Property, Plant and Equipment, Net Statement of Stockholders' Equity [Abstract] Dividends paid (in dollars per share) Common Stock, Dividends, Per Share, Cash Paid Domestic Income (Loss) from Continuing Operations before Income Taxes, Domestic International Income (Loss) from Continuing Operations before Income Taxes, Foreign Total Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest Fair Value, Assets and Liabilities, Measured on Recurring Basis Unobservable Input Reconciliation [Table] Fair Value, Assets and Liabilities, Measured on Recurring Basis Unobservable Input Reconciliation [Table] Summarization of the information required and determined to be provided for purposes of reconciling beginning and ending balances of fair value measurements of assets and liabilities using significant unobservable inputs (Level 3). Such reconciliation, separately presenting changes during the period, at a minimum, may include: (1) total gains or losses for the period (realized and unrealized), segregating those gains or losses included in earnings (or changes in net assets) and gains or losses recognized in other comprehensive income, and a description of where those gains or losses included in earnings (or changes in net assets) are reported in the statement of income (or activities); (2) purchases, sales, issuances, and settlements (each type disclosed separately); and (3) transfers in and transfers out of Level 3 (for example, transfers due to changes in the observability of significant inputs), by class of asset and liability. Fair Value, by Asset and Liability Class [Axis] Fair Value, by Asset and Liability Class [Axis] Fair value information by class of asset and liability. Fair Value, Assets and Liabilities, Measured on Recurring Basis, Unobservable Input Reconciliation by Asset Class [Domain] Fair Value, Assets and Liabilities, Measured on Recurring Basis, Unobservable Input Reconciliation by Asset Class [Domain] Represents classes of assets and liabilities measured and disclosed at fair value. Contingent Payment Arrangements Affiliate Equity Obligations Level 3 reconciliation of assets and liabilities Fair Value, Assets and Liabilities, Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] -- None. No documentation exists for this element. -- Changes in level 3 assets and liabilities Fair Value, Assets and Liabilities, Measured on Recurring Basis, Unobservable Input Reconciliation Calculation [Roll Forward] -- None. No documentation exists for this element. -- Balance, beginning of period Fair Value, Measurement with Unobservable Inputs Reconciliation Recurring Basis, Asset and Liabilities Value Represents assets and liabilities measured at fair value using significant unobservable inputs (Level 3) which are required for reconciliation purposes of beginning and ending balances. Net realized and unrealized (gains) losses(1) Fair Value, Measurement with Unobservable Inputs Reconciliation Recurring Basis, Asset and Liabilities Realized Gain (Loss) Included in Earnings Represents total realized gains or losses for the period, arising from assets and liabilities measured at fair value on a recurring basis using unobservable inputs (Level 3), which are included in earnings or other comprehensive income. Purchases and issuances(2) Fair Value, Measurement with Unobservable Inputs Reconciliation Recurring Basis, Assets and Liabilities Purchases and Issuances Fair Value, Measurement with Unobservable Inputs Reconciliation Recurring Basis, Assets and Liabilities Purchases and Issuances Settlements and reductions Fair Value, Measurement with Unobservable Inputs Reconciliation Recurring Basis Assets and Liabilities Settlements and Reductions Represents settlements and reductions which have taken place during the period in relation to assets and liabilities measured at fair value on a recurring basis using unobservable inputs (Level 3). Balance, end of period Net change in unrealized (gains) losses relating to instruments still held at the reporting date Fair Value, Measurement with Unobservable Inputs Reconciliation Recurring Basis, Unrealized Asset and Liabilities Gain (Loss) Included in Earnings Represents total unrealized gains or losses for the period, arising from assets and liabilities measured at fair value on a recurring basis using unobservable inputs (Level 3), which are included in earnings or other comprehensive income. Junior convertible securities Junior Convertible Trust Preferred Securities [Member] Represents the junior convertible trust preferred securities. Carrying Value Junior Convertible Trust Preferred Debt Noncurrent Carrying amount of junior long-term convertible debt as of the balance sheet date, net of the amount due in the next twelve months. The debt is convertible, at any time, into a defined number of shares of common stock. Holders of the junior convertible trust preferred securities have no rights to put these securities. Debt instrument term Debt Instrument, Term Statement of Comprehensive Income [Abstract] Net income Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Other comprehensive income (loss): Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest [Abstract] Foreign currency translation gain (loss) Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax Change in net realized and unrealized gain (loss) on derivative securities, net of tax Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax Change in net unrealized gain (loss) on investment securities, net of tax Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax Other comprehensive income (loss) Comprehensive income Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Comprehensive income (non-controlling interests) Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest Comprehensive income (controlling interest) Comprehensive Income (Loss), Net of Tax, Attributable to Parent Selected Quarterly Financial Data (Unaudited) Quarterly Financial Information [Text Block] Current: Current Income Tax Expense (Benefit), Continuing Operations [Abstract] Federal Current Federal Tax Expense (Benefit) State Current State and Local Tax Expense (Benefit) Foreign Current Foreign Tax Expense (Benefit) Total current Deferred: Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract] Federal Deferred Federal Income Tax Expense (Benefit) State Deferred State and Local Income Tax Expense (Benefit) Foreign Deferred Foreign Income Tax Expense (Benefit) Total deferred Forward Equity Sale Agreements -- None. No documentation exists for this element. -- Schedule of Stock by Class [Table] Schedule of Stock by Class [Table] Forward Contract Indexed to Issuer's Equity, Type [Axis] Forward Contract Indexed to Issuer's Equity, Type [Axis] Forward Contract Indexed to Issuer's Equity, Type [Domain] Forward Contract Indexed to Issuer's Equity, Type [Domain] Equity Distribution Program Forward Equity Agreement [Member] Forward Equity Agreement Class of Stock Class of Stock [Line Items] Stock program, maximum amount authorized Stock Issuable, Value, Maximum Stock Issuable, Value, Maximum Proceeds from issuance of common stock Proceeds from Issuance of Common Stock Maximum number of shares available for sale under agreement (in shares) Forward Contract Indexed to Issuer's Equity, Shares Common stock price (in dollars per share) Forward Contract Indexed to Issuer's Equity, Forward Rate Per Share Number of common shares issued (in shares) Forward Contract Indexed to Issuer's Equity, Indexed Shares Number of shares net settled for cash (in shares) Forward Contract Indexed to Issuer's Equity, Settlement Alternatives, Shares, at Fair Value Average share price of shares net settled for cash (in dollars per share) Forward Contract Indexed to Issuer's Equity, Settlement Alternatives, Average Price Per Share Forward Contract Indexed to Issuer's Equity, Settlement Alternatives, Average Price Per Share Common stock, shares outstanding (in shares) Common Stock, Shares, Outstanding Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value Measurements, Recurring and Nonrecurring [Table] Measurement Frequency [Axis] Measurement Frequency [Axis] Fair Value, Measurement Frequency [Domain] Fair Value, Measurement Frequency [Domain] Fair Value Measured on a Recurring Basis Fair Value, Measurements, Recurring [Member] Level 1 Fair Value, Inputs, Level 1 [Member] Level 3 Fair Value, Inputs, Level 3 [Member] Fair Value, Assets and Liabilities Measured on a Recurring and NonrecurringBasis Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Financial Assets Assets, Fair Value Disclosure [Abstract] Cash equivalents Cash and Cash Equivalents, Fair Value Disclosure Investments in marketable securities Trading Available-for-sale securities Other investments Investments, Fair Value Disclosure Foreign currency forward contracts Foreign Currency Contract, Asset, Fair Value Disclosure Financial Liabilities Liabilities, Fair Value Disclosure [Abstract] Contingent payment arrangements Obligations, Fair Value Disclosure Affiliate equity obligations Due to Related Parties, Fair Value Disclosure Due to Related Parties, Fair Value Disclosure Foreign currency forward contracts Foreign Currency Contracts, Liability, Fair Value Disclosure Redeemable Non-Controlling Interests Noncontrolling Interest Disclosure [Text Block] Document and Entity Information -- None. No documentation exists for this element. -- Entity Registrant Name Entity Central Index Key Document Type Document Period End Date Amendment Flag Current Fiscal Year End Date Entity Well-known Seasoned Issuer Entity Voluntary Filers Entity Current Reporting Status Entity Filer Category Entity Public Float Entity Common Stock, Shares Outstanding Document Fiscal Year Focus Document Fiscal Period Focus Revenue Asset Management Fees Operating income Operating Income (Loss) Income before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Earnings per share - diluted (in dollars per share) Earnings Per Share, Diluted Schedule of Recent Share-Based Compensation Expense Schedule of Share-based Compensation Expense and Tax Benefit [Table Text Block] Tabular disclosure of share based compensation expense and the related tax benefit recorded by the entity. Schedule of Transactions of the Company's Stock Options Share-based Compensation, Activity [Table Text Block] Schedule of Assumptions Used to Determine Fair Value of Options Granted Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block] Schedule of Transactions of the Company's Restricted Stock Schedule of Nonvested Share Activity [Table Text Block] Foreign Currency Translation Adjustment Realized and Unrealized Gains (Losses) on Derivative Securities Total AOCI Including Portion Attributable to Noncontrolling Interest [Member] Accumulated Other Comprehensive Income (Loss) Net of Tax [Roll Forward] AOCI Attributable to Parent, Net of Tax [Roll Forward] Beginning Balance Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Other comprehensive gain (loss) before reclassifications Other Comprehensive Income (Loss), before Reclassifications, Net of Tax Amounts reclassified Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax Other comprehensive income (loss) Ending Balance Variable Interest Entity [Abstract] Variable Interest Entity [Abstract] Schedule of Variable Interest Entities [Table] Schedule of Variable Interest Entities [Table] Variable Interest Entities [Axis] Variable Interest Entities [Axis] Variable Interest Entity, Classification [Domain] Variable Interest Entity, Classification [Domain] Affiliates accounted for under the equity method Variable Interest Entities Previously Accounted for Under the Equity Method [Member] Variable Interest Entities Previously Accounted for Under the Equity Method Variable Interest Entity [Line Items] Variable Interest Entity [Line Items] Unconsolidated VIE Net Assets Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net Carrying Value and Maximum Exposure to Loss Variable Interest Entity, Nonconsolidated, Comparison of Carrying Amount of Assets and Liabilities to Maximum Loss Exposure Schedule of Reconciliation of the Numerator and Denominator used in the Calculation of Basic and Diluted Earnings per Share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Schedule of Diluted Earnings per Share Calculations, Excluding the Anti-dilutive Effect of Shares Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block] Payables and Accruals [Abstract] Accrued compensation Employee-related Liabilities Unsettled fund share payables Unsettled Fund Share Payables Unsettled fund share payables are created by the normal settlement periods on transactions initiated by certain clients of Affiliate funds domiciled in the United Kingdom. Accrued income taxes Accrued Income Taxes Accrued share repurchases Payables Recorded For Share Repurchases Payables Recorded For Share Repurchases Accrued professional fees Accrued Professional Fees Other Other Accrued Liabilities Payables and accrued liabilities Accounts Payable and Accrued Liabilities Comprehensive Income Comprehensive Income (Loss) Note [Text Block] Fixed Assets and Lease Commitments Fixed Assets and Lease Commitments Disclosure [Text Block] Disclosure of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale. Also includes the following disclosure for operating leases having initial or remaining non cancelable lease terms in excess of one year: (a) future minimum rental payments required as of the date of the latest balance sheet presented, in the aggregate and for each of the five succeeding fiscal years. Computer software Fixed Assets Estimated useful lives of office equipment, furniture and fixtures Property, Plant and Equipment, Useful Life Earnings Per Share Earnings Per Share [Text Block] Statutory U.S. federal tax rate Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent State income taxes, net of federal benefit Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent Effect of foreign operations Effective Income Tax Rate Reconciliation, Repatriation of Foreign Earnings, Percent Equity compensation Effective Income Tax Rate Reconciliation, Nondeductible Expense, Share-based Compensation Cost, Percent Effect of changes in tax law, rates Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Percent Other Effective Income Tax Rate Reconciliation, Other Adjustments, Percent Effective tax rate (controlling interest) Effect of income from non-controlling interests Effective Income Tax Rate Reconciliation, Noncontrolling Interest Income (Loss), Percent Effective tax rate Effective Income Tax Rate Reconciliation, Percent Statement of Cash Flows [Abstract] Cash flow from (used in) operating activities: Net Cash Provided by (Used in) Operating Activities [Abstract] Adjustments to reconcile Net income to net cash flow from operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Intangible amortization and impairments Amortization and Impairments of Intangible Assets Amortization and Impairments of Intangible Assets Depreciation and other amortization Depreciation and Other Amortization The aggregate expense charged against earnings to allocate the cost of tangible assets to periods in which the assets are used and held and to allocate the cost of issuing debt to periods in which the debt is outstanding. As a noncash expense, this element is added back to net income when calculating cash provided by (used in) operations using the indirect method. Deferred income tax provision Income from equity method investments Income (Loss) from Equity Method Investments Distributions received from equity method investments Share-based compensation and Affiliate equity expense Share-based Compensation and Affiliate Equity Expense Share-based Compensation and Affiliate Equity Expense Other non-cash items Other Noncash Income (Expense) Changes in assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] Purchases of trading securities by Affiliate sponsored consolidated products Purchases of Securities by Affiliate Sponsored Consolidated Products Purchases of Securities by Affiliate Sponsored Consolidated Products Sales of trading securities by Affiliate sponsored consolidated products Sale of Securities by Affiliate Sponsored Consolidated Products Sale of Securities by Affiliate Sponsored Consolidated Products (Increase) decrease in receivables Increase (Decrease) in Receivables (Increase) decrease in other assets Increase (Decrease) in Other Operating Assets Increase (decrease) in payables, accrued liabilities and other liabilities Increase (Decrease) in Operating Liabilities Cash flow from operating activities Net Cash Provided by (Used in) Operating Activities Cash flow from (used in) investing activities: Net Cash Provided by (Used in) Investing Activities [Abstract] Investments in Affiliates Payments to Acquire Interest in Subsidiaries and Affiliates Purchase of fixed assets Payments to Acquire Property, Plant, and Equipment Purchase of investment securities Payments to Acquire Marketable Securities Sale of investment securities Proceeds from Sale and Maturity of Marketable Securities Cash flow from (used in) investing activities Net Cash Provided by (Used in) Investing Activities Cash flow from (used in) financing activities: Net Cash Provided by (Used in) Financing Activities [Abstract] Borrowings of senior bank debt and senior notes Proceeds from Issuance of Long-term Debt Repayments of senior debt, senior notes and convertible securities Repayments of Long-term Debt Issuance of common stock Dividends paid on common stock Payments of Ordinary Dividends, Common Stock Repurchase of common stock Payments for Repurchase of Common Stock Distributions to non-controlling interests Payments of Ordinary Dividends, Noncontrolling Interest Affiliate equity issuances and repurchases Proceeds from (Payments for) Affiliate Equity Issuances and Repurchases The net cash inflow (outflow) resulting from the affiliate share transaction. Excess tax benefit from share-based compensation Excess Tax Benefit from Share-based Compensation, Financing Activities Settlement of forward equity sale agreement Payments for (Proceeds from) Derivative Instrument, Financing Activities Other financing items Proceeds from (Payments for) Other Financing Activities Cash flow from (used in) financing activities Net Cash Provided by (Used in) Financing Activities Effect of foreign exchange rate changes on cash and cash equivalents Effect of Exchange Rate on Cash and Cash Equivalents Net increase (decrease) in cash and cash equivalents Cash and Cash Equivalents, Period Increase (Decrease) Cash and cash equivalents at beginning of period Cash and Cash Equivalents, at Carrying Value Net cash outflows upon the consolidation and deconsolidation of Affiliate sponsored products Cash Divested from Deconsolidation Cash and cash equivalents at end of period Supplemental disclosure of cash flow information: Supplemental Cash Flow Information [Abstract] Interest paid Interest Paid, Net Income taxes paid Income Taxes Paid, Net Supplemental disclosure of non-cash financing activities: Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] Stock issued under incentive plans Stock Issued Under Other Incentive Plans Stock Issued Under Other Incentive Plans Stock received for tax withholdings on share-based payments Shares Received for Tax Withholding for Share Based Compensation, Value Shares Received for Tax Withholding for Share Based Compensation, Value Payables recorded for Share repurchases Payables Recorded, But Not Yet Paid, Share Repurchases Payables Recorded, But Not Yet Paid, Share Repurchases Payables recorded for Affiliate equity repurchases Payables Recorded for Affiliate Equity Purchases Payables recorded for affiliate equity purchases. Stock received for the exercise of stock options Shares Received From Stock Options Exercised, Value Shares Received From Stock Options Exercised, Value Senior Notes Long-term Debt [Text Block] Schedule of Principal Terms of Senior Notes Outstanding Schedule of Maturities of Long-term Debt [Table Text Block] Income Taxes Income Tax Disclosure [Text Block] Definite-lived acquired client relationships(1) Finite-Lived Intangible Assets, Net Indefinite-lived acquired client relationships Indefinite-Lived Intangible Assets (Excluding Goodwill) Tangible assets Tangible Assets, Net Tangible Assets, Net Deferred tax liability Goodwill Consideration paid Equity Method Investments Expected economic benefit period of acquired client relationship intangibles Finite-Lived Intangible Asset, Useful Life Business and Summary of Significant Accounting Policies Organization, Consolidation, Basis of Presentation, Business Description and Accounting Policies [Text Block] Share-Based Compensation Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Affiliate Equity -- None. No documentation exists for this element. -- Balance Sheet Location [Axis] Balance Sheet Location [Axis] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Other Assets Other Assets [Member] Other Liabilities Other Liabilities [Member] Affiliate Equity Distributions paid to affiliate partners Affiliate equity, conditional right to put interest, period Affiliate Equity, Conditional Right to Put Interest, Period Affiliate Equity, Conditional Right to Put Interest, Period Payments to acquire interest in affiliates Payments to Acquire Businesses and Interest in Affiliates Issuance of interest in affiliates Proceeds from Divestiture of Businesses and Interests in Affiliates Due from affiliates Due from Affiliates Due to affiliates Due to Affiliate Total fair value of share-based compensation awards vested Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value Excess tax benefit recognized from share-based incentive plans Excess Tax Benefit from Share-based Compensation, Operating Activities Total compensation cost not yet recognized Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized Weighted average period for recognition (in years) Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition Derivative Instruments and Hedging Activities Disclosure [Abstract] Derivative Instruments, Gain (Loss) [Table] Derivative Instruments, Gain (Loss) [Table] Affiliated Entity Derivative Instrument [Axis] Derivative Instrument [Axis] Derivative Contract [Domain] Derivative Contract [Domain] Foreign Currency Forward Contract Foreign Exchange Forward [Member] Market Based Derivative Equity Contract [Member] Derivative Instruments, Gain (Loss) [Line Items] Derivative Instruments, Gain (Loss) [Line Items] Gains realized upon settlement of foreign currency forward contracts Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion Losses realized upon settlement of foreign currency forward contract on Derivative Derivative Instruments, Loss Reclassified from Accumulated OCI into Income, Effective Portion Unrealized gains related to outstanding foreign currency contracts Derivative Instruments, Gain Recognized in Other Comprehensive Income (Loss), Effective Portion Unrealized losses related to outstanding foreign currency contracts Derivative Instruments, Loss Recognized in Other Comprehensive Income (Loss), Effective Portion Recognized expense on derivative Derivative, Loss on Derivative Schedule of Cost, Gross Unrealized Gains and Losses, and Fair Value of Investments Available-for-sale Securities [Table Text Block] Statement [Table] Statement [Table] Additional Paid-In Capital Additional Paid-in Capital [Member] Accumulated Other Comprehensive Income (Loss) AOCI Attributable to Parent [Member] Retained Earnings Retained Earnings [Member] Treasury Stock at Cost Treasury Stock [Member] Statement Statement [Line Items] Increase (Decrease) in Stockholders' Equity Increase (Decrease) in Stockholders' Equity [Roll Forward] Beginning Balance (in shares) Share-based compensation Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition Common stock issued under share-based incentive plans Stock Issued During Period, Value, Share-based Compensation, Net of Forfeitures Tax benefit from share-based incentive plans Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation Shares repurchases Treasury Stock, Value, Acquired, Cost Method Forward equity Adjustments to Additional Paid in Capital, Other Investments in Affiliates Investments in Affiliates Stock issued in connection with a purchase of a new Affiliate and the increase in non-controlling interests from new Affiliate investments. Common stock issued under forward equity agreement (in shares) Stock Issued During Period, Shares, New Issues Common stock issued under forward equity agreement Stock Issued During Period, Value, New Issues Issuance costs and other Adjustments to Additional Paid in Capital, Stock Issued, Issuance Costs and Other Adjustments to Additional Paid in Capital, Stock Issued, Issuance Costs and Other Dividends ($0.80 per share) Dividends, Common Stock, Cash Affiliate equity activity: Affiliate equity expense Issuances Noncontrolling Interest, Increase from Subsidiary Equity Issuance Repurchases Noncontrolling Interest, Increase (Decrease) from Purchase of Interests Noncontrolling Interest, Increase (Decrease) from Purchase of Interests Changes in redemption value of Redeemable non-controlling interests Transfers to Redeemable non-controlling interests Noncontrolling Interest, Decrease from Transfers to Noncontrolling Interest Holders Noncontrolling Interest, Decrease from Transfers to Noncontrolling Interest Holders Capital Contributions by Affiliate equity holders Noncontrolling Interest, Increase from Contributions from Affiliate Noncontrolling Interest, Increase from Contributions from Affiliate Distributions to non-controlling interests Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders Ending Balance (in shares) Affiliate Equity Affiliate Equity [Text Block] Disclosures related to the conditional rights and obligations the company has to acquire Affiliate equity and the redeemable non-controlling interests on the consolidated balance sheets. Disclosure of the impact on the controlling interest's equity of changes in ownership at its Affiliates. Convertible Securities Convertible Securities [Text Block] Information about convertible debt arrangements, which may include amounts of borrowings, the underlying arrangements, repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, and other matters important to users of the financial statements. Variable Interest Entities -- None. No documentation exists for this element. -- Schedule of Net Assets and Liabilities and Maximum Risk of Losses Related to Unconsolidated VIEs Schedule of Variable Interest Entities [Table Text Block] Voting Common Stock Common Class A [Member] Class B Non-Voting Common Stock Common Class B [Member] Preferred Stock Preferred Stock [Member] January 2017 Plan January 2017 Plan [Member] January 2017 Plan May 2015 Plan May 2015 Plan [Member] May 2015 Plan Stockholders' equity Common stock, shares authorized (in shares) Common Stock, Shares Authorized Share repurchase activity Treasury Stock Transactions, Excluding Value of Shares Reissued [Abstract] Preferred stock, shares authorized (in shares) Preferred Stock, Shares Authorized Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Geographical [Axis] Geographical [Axis] Geographical [Domain] Geographical [Domain] United States UNITED STATES United Kingdom UNITED KINGDOM Other OTHER [Member] OTHER Segment Reporting Information Segment Reporting Information [Line Items] Revenue Fixed Assets, Net Schedule of Accounts Payable and Accrued Liabilities Schedule of Accounts Payable and Accrued Liabilities [Table Text Block] Investments, All Other Investments [Abstract] Other Investments Investment [Text Block] Payables and Accrued Liabilities Accounts Payable, Accrued Liabilities, and Other Liabilities Disclosure, Current [Text Block] Schedule of Defined Benefit Plans Disclosures [Table] Schedule of Defined Benefit Plans Disclosures [Table] Defined Benefit Plan Disclosure [Line Items] Defined Benefit Plan Disclosure [Line Items] Expenses related to qualified defined contribution plans Defined Contribution Plan, Cost Schedule II Valuation and Qualifying Accounts Schedule of Valuation and Qualifying Accounts Disclosure [Text Block] Forward Equity and Equity Distribution Program Forward Equity Sale Agreements [Text Block] Information about forward equity sale agreements, which may include amounts outstanding and capacity to sell. Statement of Financial Position [Abstract] Assets Assets [Abstract] Cash and cash equivalents Receivables Accounts Receivable, Net Investments in marketable securities Marketable Securities Other investments Other Investments Fixed assets (net) Acquired client relationships (net) Intangible Assets, Net (Excluding Goodwill) Equity method investments in Affiliates Other assets Other Assets Total assets Assets Liabilities and Equity Liabilities and Equity [Abstract] Payables and accrued liabilities Senior bank debt Senior notes Senior Notes Convertible securities Convertible Debt Deferred income tax liability (net) Other liabilities Other Liabilities Total liabilities Liabilities Commitments and contingencies Commitments and Contingencies Redeemable non-controlling interests Equity: Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Common stock ($0.01 par value, 153.0 shares authorized; 58.5 shares outstanding in 2016 and 2017) Common Stock, Value, Issued Additional paid-in capital Additional Paid in Capital, Common Stock Accumulated other comprehensive loss Accumulated Other Comprehensive Income (Loss) Attributable to Parent, Net of Tax Accumulated change in equity applicable to the parent entity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge. Retained earnings Retained Earnings (Accumulated Deficit) Total stockholders' equity before treasury stock Stockholders' Equity before Treasury Stock Less: Treasury stock, at cost (1.8 shares in 2016 and 3.4 shares in 2017) Treasury Stock, Value Total stockholders’ equity Stockholders' Equity Attributable to Parent Non-controlling interests Other Noncontrolling Interests Total equity Total liabilities and equity Liabilities and Equity Investments in Affiliates and Affiliate Sponsored Investment Products Variable Interest Entities Disclosure [Text Block] This element represents the disclosure of variable interest entities (VIE), including, but not limited to the nature, purpose, size, and activities of the VIE, the carrying amount and classification of consolidated assets that are collateral for the VIE's obligations, lack of recourse if creditors (or beneficial interest holders) of a consolidated VIE have no recourse to the general credit of the primary beneficiary. Which also include information related to Sponsored Investment Funds and Trust Preferred Vehicles related to variable interest entities (VIE). Number of operating segments Number of Operating Segments Number of reportable segments Number of Reportable Segments Number of principal distribution channels Number of Principal Distribution Channels Number of principal distribution channels. Schedule of Intangible Assets, by Major Class [Table] Schedule of Intangible Assets, by Major Class [Table] Tabular disclosure of the major classes of acquired finite-lived and indefinite-lived intangible assets showing the amount, any significant residual value, weighted average amortization period, and other characteristics. A major class is composed of intangible assets that can be grouped together because they are similar, either by nature or by their use in the operations of the company. Intangible assets Intangible Asset [Line Items] -- None. No documentation exists for this element. -- Definite-lived Finite-lived Intangible Assets [Roll Forward] Gross book value, balance at the beginning of the period Finite-Lived Intangible Assets, Gross Accumulated amortization, balance at the beginning of the period Finite-Lived Intangible Assets, Accumulated Amortization Net book value, balance at the beginning of the period Intangible amortization and impairments Finite-Lived Amortization and Impairment Finite-Lived Amortization and Impairment Foreign currency translation Finite Lived Intangible Assets, Foreign Currency Translation Gain (Loss) Gross book value, balance at the end of the period Accumulated amortization, balance at the end of the period Net book value, balance at the end of the period Indefinite-lived Indefinite-lived Intangible Assets [Roll Forward] Net book value, balance at the beginning of the period Impairment Impairment of Intangible Assets, Indefinite-lived (Excluding Goodwill) Foreign currency translation Indefinite-lived Intangible Assets, Foreign Currency Translation Gain (Loss) Net book value, balance at the end of the period Net Book Value Intangible Assets [Roll Forward] -- None. No documentation exists for this element. -- Net book value balance at the beginning of the period Intangible amortization and impairments Foreign currency translation Intangible Assets Net Excluding Goodwill Translation Adjustments Represents the amount of increase (decrease) to assets, excluding financial assets and goodwill, for foreign currency translation adjustments. Net book value balance at the end of the period 2018 Operating Leases, Future Minimum Payments Due, Next Twelve Months 2019 Operating Leases, Future Minimum Payments, Due in Two Years 2020 Operating Leases, Future Minimum Payments, Due in Three Years 2021 Operating Leases, Future Minimum Payments, Due in Four Years 2022 Operating Leases, Future Minimum Payments, Due in Five Years Thereafter Operating Leases, Future Minimum Payments, Due Thereafter Consolidated rent expense Operating Leases, Rent Expense, Net Stock Options Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward] Stock options outstanding at the beginning of the period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number Options granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Net of Forfeitures Options exercised (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Options forfeited (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period Stock options outstanding at the end of the period (in shares) Exercisable stock options, at the end of the period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number Weighted Average Exercise Price Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract] Stock options outstanding, at the beginning of the period (in usd per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price Options granted (in usd per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price Options exercised (in usd per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price Options forfeited (in usd per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Forfeitures in Period, Weighted Average Exercise Price Stock options outstanding, at the end of the period (in usd per share) Exercisable stock options, at the end of the period (in usd per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price Weighted Average Remaining Contractual Life (years) Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract] Stock options outstanding, at the end of the period (in years) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term Exercisable stock options, at the end of the period (in years) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term Cost of investments in marketable securities, gross unrealized gains and losses Unrealized Gain (Loss) on Investments [Abstract] Proceeds from sale of investment classified as available-for-sale Available-for-sale Securities, Gross Realized Gains (Losses), Sale Proceeds Realized net gains on available-for-sale securities Available-for-sale Securities, Gross Realized Gain (Loss) Proceeds from trading securities Proceeds from Sale of Trading Securities Held-for-investment Realized net gains on trading securities Trading Securities, Realized Gain (Loss) Restricted Stock Restricted Stock [Member] Fair value of restricted stocks granted Vesting period of restricted stocks Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period Restricted stocks available for future grant under the Company's option plans (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant Income Statement [Abstract] Operating expenses: Operating Expenses [Abstract] Compensation and related expenses Labor and Related Expense Selling, general and administrative Selling, General and Administrative Expense Other operating expenses (net) Other Cost and Expense, Operating Total operating expenses Operating Expenses Operating income before income from equity method investments Operating Income (Loss) before Equity Method Investments Operating Income (Loss) before Equity Method Investments Income from equity method investments Operating income Non-operating (income) and expenses: Nonoperating Income (Expense) [Abstract] Investment and other income Investment and Other Income (Loss) The amount of income from cost method investments, foreign currency transaction gain or loss and other income recognized during the period. Interest expense Interest Expense Imputed interest expense and contingent payment arrangements Imputed Interest Expense (Income) And Contingent Payment Arrangements Imputed Interest Expense (Income) And Contingent Payment Arrangements Total other non-operating (income) and expenses Nonoperating Income (Expense) Income before income taxes Income tax expense Net income Net income (non-controlling interests) Noncontrolling Interest in Net Income (Loss) Other Noncontrolling Interests, Redeemable Net income (controlling interest) Average shares outstanding - diluted (in shares) Earnings per share - basic (in dollars per share) Earnings Per Share, Basic Dividends per share (in dollars per share) Schedule of Recent Share Repurchase Activity Class of Treasury Stock [Table Text Block] Related Party Transactions [Abstract] Schedule of Related Party Transactions, by Related Party [Table] Schedule of Related Party Transactions, by Related Party [Table] Prior Owner Prior Owner [Member] Prior Owner of entity Related Party Transactions Related Party Transaction [Line Items] Investment partnerships with prior owners Investment Partnerships with Prior Owners Investment Partnerships with Prior Owners Contingent liabilities arrangements to related parties Business Combination, Contingent Consideration, Liability Payments associated with contingent liabilities arrangements to related parties Payment for Contingent Consideration Liability, Operating Activities Imputed interest (gains) expenses of contingent payment arrangements Increase / (decrease) in controlling interest paid-in capital from purchases and sales of Affiliate equity issuances Adjustments to Additional Paid in Capital Increase in Carrying Amount of Redeemable Noncontrolling Interests Adjustments to Additional Paid in Capital Increase in Carrying Amount of Redeemable Noncontrolling Interests Decrease in controlling interest paid-in capital related to Affiliate equity repurchases Adjustments to Additional Paid in Capital Decrease in Carrying Amount of Redeemable Noncontrolling Interests Adjustments to Additional Paid in Capital Decrease in Carrying Amount of Redeemable Noncontrolling Interests Net income attributable to controlling interest and transfers from non-controlling interests Increase (Decrease) in Equity Due to Profit (Loss) and Net Transfers with Noncontrolling Interests Increase (decrease) in equity during the period due to net income attributable to the parent company and net transfers with non-controlling interests. Schedule of Affiliate Equity Expense Summary of Affiliate Equity Compensation Expense [Table Text Block] Summary of Affiliate Equity Compensation Expense [Table Text Block] Schedule of Affiliate Equity Unrecognized Expense Summary of Affiliate Equity Unrecognized Compensation Expense [Table Text Block] Summary of Affiliate Equity Unrecognized Compensation Expense [Table Text Block] Schedule of the Effect of Changes in the Company's Ownership Interest in its Affiliates on the Controlling Interest's Equity Schedule of Net Income (Loss) Attributable to Entity and Net Transfers with Noncontrolling Interest [Table Text Block] Represents a schedule of net income (loss) attributable to the entity and net transfers to non-controlling interest. Junior Convertible Securities Stated interest rate Principal amount at maturity Debt Instrument, Individual Security, Face Amount Debt Instrument, Individual Security, Face Amount Conversion ratio (in shares) Debt Instrument, Convertible, Conversion Ratio Conversion price (in usd per share) Debt Instrument, Convertible, Conversion Price Redemption closing price trigger (in usd per share) Debt Instrument, Convertible, Stock Price Trigger Number of trading days closing price has exceeded threshold Debt Instrument, Convertible, Threshold Trading Days Number of consecutive trading days Debt Instrument, Convertible, Threshold Consecutive Trading Days Deferred tax liability Deferred Tax Liability from Excess Interest Expense Calculation Represents the deferred taxes generated from the excess of the interest expense calculated under federal income tax regulations over interest expense as calculated for book purposes. 2022 Senior Notes Senior Notes Five Point Two Five Percent Due 2022 [Member] Senior Notes5.25% Due 2022 Notes redeemed, canceled and retired Extinguishment of Debt, Amount Redemption price (as percentage) Debt Instrument, Redemption Price, Percentage Number of senior notes outstanding Number of Debt Instruments, Outstanding Represents the number of debt instruments outstanding during the period. Related Party Transactions Related Party Transactions Disclosure [Text Block] Schedule of Fair Value of Financial Assets and Liabilities Measured on a Recurring Basis Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Schedule of Changes in Level 3 Financial Assets and Liabilities Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] Schedule of Quantitative Information Fair Value Inputs, Liabilities, Quantitative Information [Table Text Block] Schedule of Investments Fair Value Measurement, Inputs Based on Net Assets [Table Text Block] Tabular disclosure of investments that rely on net asset value as their fair value, including the nature of the investment and any related liquidation restrictions. Schedule of Financial Liabilities not Carried at Fair Value Summary of Other Financial Liabilities Not Carried at Fair Value [Table Text Block] Summary of Other Financial Liabilities Not Carried at Fair Value [Table Text Block] Affiliate sponsored investment products Sponsored Investment Funds [Member] Represents investment funds in to which the entity is not the primary beneficiary of these VIEs. Carrying Value and Maximum Risk of Loss Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount Equity Investments in Affiliates Equity Method Investments and Joint Ventures Disclosure [Text Block] Schedule of Changes in Redeemable Non-Controlling Interests Redeemable Noncontrolling Interest [Table Text Block] Derivative Financial Instruments Derivative Instruments and Hedging Activities Disclosure [Text Block] Fair value of stock options granted Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested in Period, Fair Value Vesting period of options Expiration period of options Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period Total intrinsic value of options exercised Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value Cash received for options exercised Proceeds from Stock Options Exercised Intrinsic value of exercisable options outstanding Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value Options available for future grant under the Company's option plans (in shares) Weighted average fair value of options granted (in usd per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Treasury stock, shares (in shares) Treasury Stock, Shares Restricted Stock Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Units outstanding at the beginning of the period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Units granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Units vested (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period Units forfeited (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period Units outstanding at the end of the period (in shares) Weighted Average Grant Date Value Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Units outstanding at the beginning of the period (in usd per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value Units granted (in usd per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value Units vested (in usd per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value Units forfeited (in usd per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value Units outstanding at the end of the period (in usd per share)