Document and Entity Information [Abstract] Document and Entity Information Statement [Table] Class of Stock [Axis] Class of Stock [Domain] Class A Common Stock [Member] Class A Common Stock (Shares) Class B Common Stock, Class B1 [Member] Class B Common Stock, Class B1 Class B Common Stock, Class B2 [Member] Class B Common Stock, Class B2 Class B Common Stock, Class B3 [Member] Class B Common Stock, Class B3 Class B Common Stock, Class B4 [Member] Class B Common Stock, Class B4 Statement [Line Items] Document Type Amendment Flag Document Period End Date Document Fiscal Period Focus Document Fiscal Year Focus Trading Symbol Entity Registrant Name Entity Central Index Key Current Fiscal Year End Date Entity Filer Category Entity Common Stock, Shares Outstanding Consolidated Balance Sheets Class B Common Stock [Member] Class B Common Stock (Shares) Assets Cash and cash equivalents Cash and Cash Equivalents, End of Period Cash and cash equivalents, beginning of period Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value, Total Marketable Securities, Current Marketable securities Marketable Securities, Current, Total Marketable securities Accounts receivable, net of allowance of $1.4 and $1.9 Accounts Receivable, Net, Current, Total Accounts receivable, net of allowance of $1.5 and $1.6 Other Assets, Current Other current assets (includes $40.0 and $0 in restricted cash) Total Total Good Faith and Margin Deposits with Broker-Dealers Total Cash performance bonds and guaranty fund contributions Total current assets Total current assets Property, net Property, Plant and Equipment, Net, Ending Balance Property, Plant and Equipment, Net, Beginning Balance Property, net Property, net Property, net of accumulated depreciation and amortization of $535.2 and $512.9 Intangible assets-trading products Trading products Intangible assets-other, net Intangible assets net, excluding goodwill Intangible Assets, Net (Excluding Goodwill), Total Net book value Goodwill Total Goodwill, ending balance Total Goodwill, beginning balance Other Assets, Noncurrent Total Other Assets, Noncurrent, Total Other assets (includes $20.0 and $0 in restricted cash) Total Assets Total Assets Liabilities and Shareholders' Equity Accounts Payable, Current Accounts Payable, Current, Total Accounts payable Short-term debt $300.0 million floating rate notes due August 2010, interest equal to 3-month LIBOR plus 0.65%, reset quarterly Other Liabilities Current Total Total Other current liabilities The amount due to other broker-dealers in the form of a deposit paid by the counterparty to demonstrate an intention to complete a purchase (good faith deposit) and also the amount due to a customer in the form of collateral deposited by the counterparty to cover the credit risk assumed by the entity (margin deposit). Cash Performance Bonds and Security Deposit Liability Cash performance bonds and guarantee fund contributions Cash performance bonds and guaranty fund contributions Total current liabilities Total current liabilities Long-term debt Long-term debt Net Non-Current Deferred Tax Liabilities Deferred tax liabilities, net Net Non-Current Deferred Tax Liabilities Deferred tax liabilities, net Other Liabilities Noncurrent Total Total Other liabilities Total Liabilities Total Liabilities Temporary Equity Carrying Amount Balance at December 31 Balance at January 1 Redeemable non-controlling interest Shareholders' Equity: Preferred Stock, Value, Issued Preferred Stock, Value, Issued, Ending Balance Preferred Stock, Value, Issued, Beginning Balance Preferred stock, $0.01 par value, 9,860 shares authorized, none issued or outstanding Preferred Stock, Value, Issued, Total Preferred stock, $0.01 par value, 9,860 shares authorized, none issued or outstanding Series A junior participating preferred stock, $0.01 par value, 140 shares authorized, none issued or outstanding Series A junior participating preferred stock, $0.01 par value, 140 shares authorized, none issued or outstanding Class A common stock, $0.01 par value, 1,000,000 shares authorized, 0 and 66,511 shares issued and outstanding as of June 30, 2010 and December 31, 2009 Class B common stock, $0.01 par value, 3 shares authorized, issued and outstanding Common stock Additional paid-in capital Additional Paid in Capital, Common Stock, Ending Balance Additional Paid in Capital, Common Stock, Beginning Balance Retained Earnings (Accumulated Deficit) Retained Earnings (Accumulated Deficit), Ending Balance Retained Earnings (Accumulated Deficit), Beginning Balance Retained Earnings (Accumulated Deficit), Total Retained earnings Accumulated Other Comprehensive Income, net of tax Accumulated Other Comprehensive Income (Loss), Net of Tax, Ending Balance Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning Balance Accumulated Other Comprehensive Income (Loss) Accumulated Other Comprehensive Income (Loss), Net of Tax, Total Accumulated other comprehensive income (loss) Total Shareholders' Equity Balance Balance Balance Balance Balance Total Shareholders' Equity Total Liabilities and Shareholders' Equity Total Liabilities and Shareholders' Equity Preferred stock [Member] Series A junior participating preferred stock [Member] Accounts receivable, allowance Allowance for Doubtful Accounts Receivable, Current, Ending Balance Allowance for Doubtful Accounts Receivable, Current, Beginning Balance Accounts receivable, allowance Restricted Cash and Cash Equivalents, Current Restricted cash, current Accumulated depreciation and Amortization, Property, Plant, and Equipment Less accumulated depreciation and amortization AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Ending Balance Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Beginning Balance Accumulated depreciation and amortization, property Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Total Less accumulated depreciation and amortization Restricted Cash and Cash Equivalents, Noncurrent Restricted cash, noncurrent Preferred stock, par value Preferred stock, shares authorized Preferred stock, issued Preferred stock, shares issued Preferred Stock, Shares Issued, Total Preferred stock, outstanding Preferred Stock, Shares Outstanding, Ending Balance Preferred Stock, Shares Outstanding, Beginning Balance Preferred stock, shares outstanding Common stock, par value Common stock, shares authorized Shares authorized Common stock, shares issued Common Stock, Shares, Issued, Total Common stock, shares outstanding Balance (in shares) Balance (in shares) Common stock Consolidated Statements of Income Revenues Clearing Fees Revenue Clearing and transaction fees Market Data And Information Services Market data and information services Revenue from providing access fees to customers for the use of electronic trading platform and revenue from telecommunication networks and communication services. Access and communication fees Other Sales Revenue, Net Other Total Revenues Total Revenues Expenses Compensation and benefits Labor and Related Expense, Total Communications Technology support services Professional fees and outside services Amortization of purchased intangibles Total amortization expense for intangible assets Amortization of Intangible Assets, Total Depreciation and amortization Depreciation, Depletion and Amortization, Nonproduction, Total Occupancy and building operations Licensing and other fee agreements Other Cost and Expense, Operating Other Cost and Expense, Operating, Total Other Total Expenses Total Expenses Operating Income Operating Income Non-Operating Income (Expense) Investment income Investment Income, Nonoperating, Total Gains (losses) on derivative investments Gains (losses) on derivative investments Gain (Loss) on Derivative Instruments, Net, Pretax, Total Net loss on derivative investments Interest and other borrowing costs Interest and other borrowing costs Interest and Debt Expense, Total Equity in net losses of unconsolidated subsidiaries Equity in net losses of unconsolidated subsidiaries Income (Loss) from Equity Method Investments, Total Equity in net losses of unconsolidated subsidiaries Total Non-Operating Total Non-Operating Non-operating income (expense) This element represents the income or loss from continuing operations attributable to the economic entity which may also be defined as revenue less expenses from ongoing operations, after income or loss from equity method investments, but before income taxes, extraordinary items, and noncontrolling interest. Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest Income before Income Taxes Total Income Tax Provision Income Tax Expense (Benefit), Total Total Income Tax Provision Income tax provision Net Income Loss Net income Net Income Net Income Less: net income attributable to redeemable non-controlling interest Net income (loss) for the period Net Income (Loss) Attributable to Noncontrolling Interest, Total Net income attributable to CME Group Net income Net Income Attributable to CME Group Net income attributable to CME Group Earnings per Common Share Attributable to CME Group: Earnings Per Share Earnings Per Share, Basic Earnings per common share, basic Earnings Per Share, Basic, Total Basic Earnings Per Share, Diluted Earnings per common share, diluted Earnings Per Share, Diluted, Total Diluted Weighted Average Number of Common Shares: Weighted Average Number Of Shares Outstanding, Basic Weighted average number of common shares, basic Weighted Average Number of Shares Outstanding, Basic, Total Basic Weighted Average Number Of Shares Outstanding, Diluted Weighted average number of common shares, diluted Diluted Diluted Consolidated Statements of Shareholders' Equity Statement, Equity Components [Axis] Equity Component [Domain] Common Stock and Additional Paid-in Capital [Member] Retained Earnings [Member] Accumulated Other Comprehensive Income (Loss) [Member] Comprehensive income attributable to CME Group: Change in net unrealized loss on securities, net of tax Change in net unrealized gain on securities, net of tax Change in net unrealized loss on securities Change in net actuarial loss on defined benefit plans, net of tax Change in net actuarial loss on defined benefit plans, net of tax Other Comprehensive Income, Defined Benefit Plans Adjustment, Net of Tax, Total Change Change in net unrealized loss on derivatives, net of tax Net change in derivative instruments, net of tax Change in net unrealized loss on derivatives, net of tax Change Change in foreign currency translation adjustment Change in foreign currency translation adjustment, net of tax Other Comprehensive Income, Foreign Currency Transaction and Translation Adjustment, Net of Tax, Total Change in foreign currency translation adjustment Total comprehensive income attributable to CME Group Total comprehensive income Total comprehensive income attributable to CME Group Cash dividend on common stock of $4.60 per share in 2009, $9.60 per share in 2008 and $3.44 per share in 2007 Cash dividends on common stock Cash dividend on common stock of $1.15 per share Cash dividends on common stock Dividends, Cash, Total Cash dividends on common stock of $9.60 per share Repurchase of Class A common stock (in shares) Number of Share Repurchased Repurchase of Class A common stock Repurchase of Class A common stock Total of Share Repurchased Exercise of stock options (in shares) Exercise of stock options Excess tax benefits from option exercises and restricted stock vesting Number of shares issued during the period as a result of the vesting of restricted stock units. Vesting Of Issued Restricted Stock Vesting of issued restricted Class A common stock (in shares) Vesting Of Issued Restricted Stock Vesting Of Issued Restricted Stock Value Vesting of issued restricted Class A common stock Stock Granted During Period, Value, Share-based Compensation Stock-based compensation Change in net unrealized loss on securities, tax Change in net unrealized gain on securities, tax Change in net actuarial loss on defined benefit plans, tax Other Comprehensive Income, Defined Benefit Plans, Tax, Total Change in net unrealized loss on derivatives, tax Net change in derivative instruments, tax Change in foreign currency translation adjustment, tax Other Comprehensive Income, Foreign Currency Translation Adjustment, Tax, Total Cash dividends on common stock, per share Consolidated Statements of Cash Flows Cash Flows from Operating Activities Adjustments to reconcile net income to net cash provided by operating activities: Share-based Compensation Share-based Compensation, Total Stock-based compensation Net accretion of discounts and amortization of debt financing costs Amortization of Financing Costs and Discounts, Total Deferred Income Tax Expense Benefit Deferred income taxes Deferred income tax provision: Total Change in assets and liabilities: Accounts receivable Accounts receivable Increase Decrease In PrepaidDeferred Expense And Other Assets Other current assets Increase (Decrease) in Prepaid, Deferred Expense and Other Assets, Total Increase Decrease In Other Operating Assets Other assets Accounts payable Increase (Decrease) in Accounts Payable, Total Accounts payable Income tax payable Income tax payable Increase Decrease In Other Accrued Liabilities Other current liabilities Increase Decrease In Other Operating Liabilities Other liabilities Adjustments Noncash Items To Reconcile Net Income Loss To Cash Provided By Used In Operating Activities Other Other Net Cash Provided by Operating Activities Net Cash Provided by Operating Activities Cash Flows from Investing Activities Proceeds from maturities of available-for-sale marketable securities Purchases of available-for-sale marketable securities Purchases of available-for-sale marketable securities Payments to Acquire Available-for-sale Securities, Total Purchases of property, net Purchases of property, net Payments to Acquire Property, Plant, and Equipment, Total Cash acquired from Index Services Cash acquired from Index Services Payments for (Proceeds from) Businesses and Interest in Affiliates, Total Contingent consideration for Liquidity Direct Technology, LLC assets Other Other Net Cash Provided by (Used in) Investing Activities Net Cash Used in Investing Activities Cash Flows from Financing Activities The net cash inflow or cash outflow from issuing (borrowing) and repaying commercial paper. Proceeds From Repayments Of Commercial Paper Proceeds (repayments) of commercial paper, net Proceeds from other borrowings, net of issuance costs Repayment of other borrowings Repayment of other borrowings Cash dividends Cash dividends Payments of Dividends, Total PaymentsForRepurchase Of Common Stock Repurchase of Class A common stock, including costs Treasury Stock, Shares Treasury Stock, Shares Treasury Stock, Value Proceeds from exercise of stock options Proceeds from exercise of stock options Distribution paid to non-controlling interest Distribution paid to non-controlling interest Excess tax benefits related to employee option exercises and restricted stock vesting Proceeds From Payments For Other Financing Activities Other Net Cash Used in Financing Activities Net Cash Used in Financing Activities Net change in cash and cash equivalents Net change in cash and cash equivalents Supplemental Disclosure of Cash Flow Information Income taxes paid Interest paid (excluding securities lending program) Interest paid Non-cash investing activities: Change in net unrealized securities gains (losses) Other Comprehensive Income, Available-for-sale Securities Adjustment, before Tax, Total Change in net unrealized derivatives gains (losses) Organization Consolidation And Presentation Of Financial Statements [Abstract] Basis of Presentation Organization Consolidation and Presentation of Financial Statements Disclosure [Text Block] Basis of Presentation Goodwill And Intangible Assets Disclosure [Abstract] Intangible Assets and Goodwill Goodwill and Intangible Assets Disclosure [Text Block] Intangible Assets and Goodwill Intangible Assets and Goodwill Debt Disclosure [Abstract] Debt Debt Disclosure [Text Block] Debt Debt Income Tax [Abstract] Income Taxes Income Tax Disclosure Test Block Income Taxes Contingencies Schedule of Loss Contingencies by Contingency [Text Block] Contingencies Guarantees [Abstract] Guarantees Schedule of Guarantee Obligations [Text Block] Guarantees Guarantees Stock-Based Payments Disclosure Of Compensation Related Costs Share Based Payments [Text Block] Stock-Based Payments Stock-Based Payments Accumulated Other Comprehensive Income (Loss) Comprehensive Income Note [Text Block] Accumulated Other Comprehensive Income (Loss) Fair Value Measurements Fair Value Disclosures Text Block Fair Value Measurements FAIR VALUE MEASUREMENTS Earnings Per Common Share [Abstract] Earnings Per Share Earnings Per Share [Text Block] Earnings Per Common Share Earnings Per Share Subsequent Events [Abstract] Subsequent Events Schedule of Subsequent Events [Text Block] Subsequent Events Subsequent Events Intangible Assets Disclosure [Text Block] Components of Intangible Assets Tabular disclosure of the amount of amortization expense expected to be recorded in succeeding fiscal years for finite-lived intangible assets. Schedule of Finite Lived Intangible Assets Future Amortization Expense [Table Text Block] Future Estimated Amortization Expense Schedule of Goodwill [Text Block] Goodwill Activity Schedule of Short-term Debt [Text Block] Schedule of Short-term Debt Schedule of Long-term Debt Instruments [Text Block] Schedule of Long-term Debt Maturities Of Long Term Debt Maturities Of Long Term Debt [Table Text Block] Maturities of Long-term Debt Fair Value Of Fixed Rate Notes By Maturity Date [Text Block] Fair Value Of Fixed Rate Notes By Maturity Date [Text Block] Fair Value of Fixed Rate Notes by Maturity Date Fair Value Measurement Inputs Disclosure [Text Block] Financial Instruments Measured at Fair Value on a Recurring Basis Basic And Diluted Earnings Per Share [Text Block] Basic And Diluted Earnings Per Share [Text Block] Basic and Diluted Earnings Per Share Legal Entity [Axis] Entity [Domain] Index Services [Member] Index Services [Member] Noncontrolling Interest, Ownership Percentage by Parent Ownership percentage Equity method investment, ownership percentage Goodwill, Impairment Loss Impairment Adjustment Impairment Adjustment Impairment adjustment Schedule of Finite-Lived Intangible Assets by Major Class [Table] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets, Major Class Name [Domain] Clearing Firm, Market Data, and Other Customer Relationships [Member] Lease-Related Intangibles [Member] Technology-Related Intellectual Property [Member] Other - Finite [Member] Other - Finite [Member] Total amortizable intangible assets [Member] Total Amortizable Intangible Assets [Member] Foreign Currency Translation Adjustments [Member] Foreign Currency Translation Adjustments [Member] Total Amortizable Intangible Assets Net [Member] Total Amortizable Intangible Assets, Net [Member] Indefinite-lived Intangible Assets by Major Class [Axis] Indefinite-lived Intangible Assets, Major Class Name [Domain] Trade Names [Member] Foreign currency translation adjustments indefinite [Member] Foreign Currency Translation Adjustments Indefinite [Member] Total Indefinite-Lived Intangible Assets [Member] Total Indefinite-Lived Intangible Assets [Member] Finite-Lived Intangible Assets, Gross Cost Cost Finite-Lived Intangible Assets, Accumulated Amortization Accumulated amortization Accumulated amortization Finite-Lived Intangible Assets, Net Net book value Finite-Lived Intangible Assets, Net, Total The amount of amortization expense expected to be recognized during the remainder of the current fiscal year. Future Amortization Expense Remainder Of Fiscal Year Remainder of 2011 Future Amortization Expense, Year One 2012 Future Amortization Expense, Year Two 2013 Future Amortization Expense, Year Three 2014 Future Amortization Expense, Year Four 2015 Future Amortization Expense, Year Five 2016 The amount of amortization expense expected to be recognized for the remainder of the finite-lived intangible asset useful life after the fifth succeeding fiscal year. Future Amortization Expense After Year Five Thereafter Schedule of Goodwill [Table] Goodwill by Segment [Axis] Goodwill, Segment [Domain] CBOT Holdings [Member] CBOT Holdings [Member] NYMEX Holdings [Member] NYMEX Holdings [Member] Goodwill, Acquired During Period Business Combinations Goodwill, Translation and Purchase Accounting Adjustments Other Activity Debt Conversion [Table] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Maximum [Member] Maximum [Member] Debt instrument, face amount New multi currency revolving senior credit facility Commercial Paper Maturity Date Range Start Commercial Paper Maturity Date Range Start Commercial paper maturity date range start, days Commercial Paper Maturity Date Range End Commercial Paper Maturity Date Range End Commercial paper maturity date range end, days Commercial Paper Weighted Average Balance At Par Value Commercial Paper Weighted Average Balance At Par Value Commercial paper weighted average balance at par value Commercial paper outstanding Commercial Paper Outstanding Commercial paper outstanding Schedule Of Debt Table Schedule Of Debt [Table] Debt Instrument [Axis] Debt Instrument, Name [Domain] Term Loan Due 2011, Interest Equal To 3-Month LIBOR Plus 1.00%, Reset Quarterly Term Loan Due 2011, Interest Equal To 3-Month LIBOR Plus 1.00%, Reset Quarterly [Member] Fixed Rate Notes Due August Two Thousand Thirteen [Member] Fixed Rate Notes Due August 2013 [Member] Fixed Rate Notes Due February Two Thousand Fourteen [Member] Fixed Rate Notes Due February 2014 [Member] Fixed Rate Notes Due March Two Thousand Eighteen [Member] Fixed Rate Notes Due March 2018 [Member] Interest Rate Swap Agreement [Member] Interest Rate Swap Agreement [Member] Forward Starting Interest Rate Swap Agreement [Member] Forward Starting Interest Rate Swap Agreement [Member] Derivative, Fixed Interest Rate Derivative, fixed interest rate Debt Instrument, Maturity Date Debt instrument, maturity date Debt instrument, interest rate, stated percentage Debt instrument, interest rate, basis for effective rate Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months 2012 Long-term Debt, Maturities, Repayments of Principal in Year Two 2013 Long-term Debt, Maturities, Repayments of Principal in Year Three 2014 Long-term Debt, Maturities, Repayments of Principal in Year Four 2015 Long-term Debt, Maturities, Repayments of Principal in Year Five 2016 Long-term Debt, Maturities, Repayments of Principal after Year Five Thereafter Debt Instrument, Fair Value Debt instrument, fair value Income Tax Disclosure [Abstract] Income Tax Disclosure Effective Tax Rate Effective tax rate Effective Income Tax Rate, Continuing Operations, Total Effective Income Tax Rate Reconciliation State Apportionment Effective Income Tax Rate Reconciliation State Apportionment Effective tax rate decrease due to a tax benefit IncomeTaxReconciliationStateApportionment Income Tax Reconciliation State Apportionment Income tax benefit Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance Increase (decrease) in domestic valuation allowance Decrease in effective tax rate due to valuation allowances Income Tax Reconciliation, Change in Deferred Tax Assets Valuation Allowance Reduction in valuation allowances Valuation Allowance, Amount Valuation allowance Loss Contingency, Range of Possible Loss, Minimum Estimated potential damages - Minimum Loss Contingency, Range of Possible Loss, Maximum Estimated potential damages - Maximum Daily Transfer Between Clearing Firms Daily Transfer Between Clearing Firms Daily transfers between clearing firms The total amount of the contingent obligation under letters of credit outstanding as of the reporting date. Letters Of Credit Outstanding Amount Contingent liability to SGX, amount of irrevocable letters of credit Percentage allocated to parent and external party of cross-margin arrangement of gains (losses) on liquidation of open position and cross-margin account Percentage Allocated To Parent And External Party Of Cross Margin Arrangement Of Gains Losses On Liquidation Of Open Position And Cross Margin Account Percentage allocated to CME and OCC of gains (losses) on liquidation of open position and cross margin account Guarantor Obligations, Current Carrying Value Guarantor obligations, current carrying value Allocated Share-based Compensation Expense Total expense for stock based payments Allocated Share-based Compensation Expense, Total Employee Service Share-based Compensation, Tax Benefit from Compensation Expense Income tax benefit for stock-based payment arrangements Share Based Compensation Arrangement By Share-based Payment Award Options Grants In Period Number of shares awarded Stock options, granted, shares Share-based Compensation Arrangement by Share-based Payment Award, Award Expiration Dating Stock options, term in years Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price Exercise price, per share Granted Fair Value Options Fair Value, Options Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Method Used Fair value assumptions, method used Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period Vesting period, years Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate Stock option valuation assumption, dividend yield Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate Stock option valuation assumption, expected volatility Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate Stock option valuation assumption, risk-free interest rate Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term Stock option valuation assumption, expected life, in years Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value Grant date weighted average fair value of options granted Granted Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Grants of restricted Class A common stock, shares Granted The minimum vesting term over which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition. Share Based Compensation Arrangement By Share Based Payment Award Award Vesting Period Minimum Share based compensation arrangement by share based payment award, award vesting period lower range, years The maximum vesting term over which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition. Share Based Compensation Arrangement By Share Based Payment Award Award Vesting Period Maximum Share based compensation arrangement by share based payment award, award vesting period upper range, years Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Total Fair Value Restricted Class A common stock, fair value of grants Accumulated Other Comprehensive Income Loss [Table] Accumulated Other Comprehensive Income Loss [Table] Reversal Accumulated Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax Reversal Accumulated Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax Reversal Accumulated Other Comprehensive Income (Loss) Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax, Ending Balance Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax, Beginning Balance Net Unrealized Gain (Loss) On Securities Investment Owned, at Fair Value Investment, Owned, at Fair Value, Ending Balance Investment, Owned, at Fair Value, Beginning Balance Market value of investment Fair Value of Investment Schedule of Defined Benefit Plans Disclosures [Table] Defined Benefit Plan, Fair Value of Plan Assets by Measurement [Axis] Fair Value Plan Asset Measurement [Domain] Fair Value, Inputs, Level 1 [Member] Fair Value, Inputs, Level 2 [Member] Fair Value, Inputs, Level 3 [Member] Restricted Cash and Cash Equivalents, Cash and Cash Equivalents [Axis] Cash and Cash Equivalents [Domain] U.S. Treasury securities [Member] Schedule of Trading Securities and Other Trading Assets, Major Types of Trading Securities and Assets [Axis] Major Types of Trading Securities and Assets [Domain] Marketable Securities [Member] Corporate Bonds [Member] Asset-backed securities [Member] U.S. Government agency securities [Member] Equity investments [Member] Fair value, measured on recurring basis, investments Total Assets at Fair Value Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Antidilutive Securities Excluded from Computation of Earnings Per Share, by Antidilutive Securities [Axis] Antidilutive Securities, Name [Domain] Stock Options [Member] Option Indexed to Issuer's Equity, Type [Axis] Option Indexed to Issuer's Equity, Type [Domain] Restricted Stock Awards [Member] Restricted Stock Awards [Member] Antidilutive Securities Excluded From Computation Of Earnings Per Share, Amount Effect of restricted grants Effect of Stock Options Effect of Stock Options Effect of stock options Incremental Common Shares Attributable To Share-Based Payment Arrangements Effect of restricted stock grants Incremental Common Shares Attributable to Share-based Payment Arrangements, Total The amount authorized by an entity's Board of Directors under a stock repurchase plan. Stock Repurchase Program, Authorized Amount Other [Member] Accumulated Other Comprehensive Income (Loss) [Axis] Accumulated Other Comprehensive Income (Loss) [Axis] Accumulated Other Comprehensive Income (Loss) [Domain] Accumulated Other Comprehensive Income (Loss) [Domain] Mutual Funds [Member] Mutual funds [Member] Municipal bonds [Member]