Investments, All Other Investments [Abstract] Investment shares sold Investment shares sold Investment shares sold Gain on Sale of Investments Gain on Sale of Investments Sale of Stock, Percentage of Ownership after Transaction Sale of Stock, Percentage of Ownership after Transaction Investment Owned, at Fair Value Investment Owned, at Fair Value Investment Owned, at Cost Investment Owned, at Cost Investment [Text Block] Investment [Text Block] Income Statement [Abstract] Revenues Revenues [Abstract] Clearing and transaction fees Clearing Fees Revenue Market data and information services Market Data Revenue Access and communication fees Access and communication fees Revenue from providing access fees to customers for the use of electronic trading platform and revenue from telecommunication networks and communication services. Other Other Revenue, Net Expenses Revenues Expenses Costs and Expenses [Abstract] Compensation and benefits Labor and Related Expense Communications Communication Technology support services Information Technology and Data Processing Professional fees and outside services Professional Fees Amortization of purchased intangibles Amortization of Intangible Assets Depreciation and amortization Depreciation, Depletion and Amortization, Nonproduction Occupancy and building operations Occupancy, Net Licensing and other fee agreements License Costs Other Other Cost and Expense, Operating Total Expenses Costs and Expenses Operating Income Operating Income (Loss) Non-Operating Income (Expense) Nonoperating Income (Expense) [Abstract] Investment income Investment Income, Nonoperating Gains (losses) on derivative investments Gain (Loss) on Derivative Instruments, Net, Pretax Interest and other borrowing costs Interest and Debt Expense Equity in net earnings (losses) of unconsolidated subsidiaries Income (Loss) from Equity Method Investments Other non-operating income (expense) Other Nonoperating Income (Expense) Total Non-Operating Nonoperating Income (Expense) Income before Income Taxes Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest Income tax provision Income Tax Expense (Benefit) Net Income Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Earnings per Common Share: Earnings Per Share [Abstract] Basic (in dollars per share) Earnings Per Share, Basic Diluted (in dollars per share) Earnings Per Share, Diluted Weighted Average Number of Common Shares: Weighted Average Number of Shares Outstanding, Diluted [Abstract] Basic (in shares) Weighted Average Number of Shares Outstanding, Basic Diluted (in shares) Weighted Average Number of Shares Outstanding, Diluted Fair Value Disclosures [Abstract] Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value by Measurement Frequency [Axis] Measurement Frequency [Axis] Fair Value, Measurement Frequency [Domain] Fair Value, Measurement Frequency [Domain] Fair Value, Measurements, Recurring [Member] Fair Value, Measurements, Recurring [Member] Fair Value, Hierarchy [Axis] Fair Value, Hierarchy [Axis] Fair Value Hierarchy [Domain] Fair Value Hierarchy [Domain] Fair Value, Inputs, Level 3 [Member] Fair Value, Inputs, Level 3 [Member] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Fair value of liability, beginning balance Business Combination, Contingent Consideration, Liability Included in other expenses Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings Fair value of liability, ending balance Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract] Schedule of Accumulated Other Comprehensive Income (Loss) Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Loss Contingency [Abstract] Accrued liability related to all outstanding legal matters Estimated Litigation Liability Property, Plant and Equipment [Abstract] Property, Plant and Equipment Disclosure Property, Plant and Equipment Disclosure [Text Block] Statement of Stockholders' Equity [Abstract] Cash dividends on common stock, per share (in dollars per share) Common Stock, Dividends, Per Share, Cash Paid Proceeds from Sale of Buildings Proceeds from Sale of Buildings Impaired Assets to be Disposed of by Method Other than Sale, Carrying Value of Asset Impaired Assets to be Disposed of by Method Other than Sale, Carrying Value of Asset Property, Plant, and Equipment, Fair Value Disclosure Property, Plant, and Equipment, Fair Value Disclosure Impairment of Real Estate Impairment of Real Estate Total Cost of Transaction Total Cost of Transaction Total Cost of Transaction Legal Fees for Sale-Leaseback Legal Fees for Sale-Leaseback Legal Fees for Sale-Leaseback Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract] Financial instruments measured at fair value on a recurring basis Fair Value, Measurement Inputs, Disclosure [Text Block] Reconciliation of assets and liabilities valued at fair value on a recurring basis using significant unobservable inputs (level 3) Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] Fair value of Debt Instruments Fair value of Debt Instruments [Table Text Block] [Table Text Block] for Fair value of Debt Instruments [Table] Performance Bonds and Guaranty Fund Contributions [Abstract] Performance Bonds and Guaranty Fund Contributions [Abstract] Schedule of Guarantor Obligations [Table] Schedule of Guarantor Obligations [Table] Investment Type [Axis] Investment Type [Axis] Investments [Domain] Investments [Domain] US Treasury Securities [Member] US Treasury Securities [Member] US Government Agencies Debt Securities [Member] US Government Agencies Debt Securities [Member] Repurchase Agreements [Member] Repurchase Agreements [Member] Guarantor Obligations [Line Items] Guarantor Obligations [Line Items] Available-for-sale Securities, Amortized Cost Basis Available-for-sale Securities, Amortized Cost Basis Available-for-sale Securities at Fair Value Available-for-sale Securities Cash and Cash Equivalents, Fair Value Disclosure Cash and Cash Equivalents, Fair Value Disclosure Average Daily Clearing Settlement Average Daily Clearing Settlement Average Daily Clearing Settlement Goodwill and Intangible Assets Disclosure [Abstract] Intangible Assets And Goodwill Goodwill and Intangible Assets Disclosure [Text Block] Debt Disclosure [Abstract] Schedule Of Short-Term And Long-Term Debt Schedule of Long-term Debt Instruments [Table Text Block] Long-term debt maturities at par value Schedule of Maturities of Long-term Debt [Table Text Block] Organization, Consolidation and Presentation of Financial Statements [Abstract] Basis Of Presentation Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Unamortized Debt Issuance Expense Unamortized Debt Issuance Expense Subsequent Events [Abstract] Subsequent Events Subsequent Events [Text Block] Components of intangible assets Intangible Assets Disclosure [Text Block] Future estimated amortization expense Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block] Statement [Table] Statement [Table] Other Comprehensive Income Location [Axis] Other Comprehensive Income Location [Axis] Other Comprehensive Income Location [Domain] Other Comprehensive Income Location [Domain] Accumulated Other Comprehensive Income (Loss) [Member] AOCI Attributable to Parent [Member] Foreign Currency Translation [Member] Foreign Currency Gain (Loss) [Member] Derivative Investments [Member] Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] Defined Benefit Plans [Member] Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] Investment Securities [Member] Accumulated Net Investment Gain (Loss) Attributable to Parent [Member] Statement [Line Items] Statement [Line Items] Balance at December 31, 2015 Stockholders' Equity Attributable to Parent Comprehensive Income Before Reclassification Adjustments Other Comprehensive Income (Loss), before Reclassifications, before Tax Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax Other Comprehensive Income (Loss), Net of Tax Other Comprehensive Income (Loss), Tax Other comprehensive income (loss), net of tax Other Comprehensive Income (Loss), Net of Tax Balance at September 30, 2016 Statement of Financial Position [Abstract] Class of Stock [Axis] Class of Stock [Axis] Class of Stock [Domain] Class of Stock [Domain] Preferred Stock [Member] Preferred Stock [Member] Series A Junior Participating Preferred Stock [Member] Series A Preferred Stock [Member] Class A Common Stock [Member] Common Class A [Member] Class B Common Stock [Member] Common Class B [Member] Accounts receivable, allowance Allowance for Doubtful Accounts Receivable, Current Restricted cash, current Restricted Cash and Cash Equivalents, Current Accumulated depreciation and amortization, property Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Restricted cash, noncurrent Restricted Cash and Cash Equivalents, Noncurrent Preferred stock, par value (in dollars per share) Preferred Stock, Par or Stated Value Per Share Preferred stock, shares authorized (in shares) Preferred Stock, Shares Authorized Preferred stock, shares issued (in shares) Preferred Stock, Shares Issued Preferred stock, shares outstanding (in shares) Preferred Stock, Shares Outstanding Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Common stock, shares authorized (in shares) Common Stock, Shares Authorized Common stock, shares issued (in shares) Common Stock, Shares, Issued Common stock, shares outstanding (in shares) Common Stock, Shares, Outstanding Debt Debt Disclosure [Text Block] Fair Value Measurements Fair Value Disclosures [Text Block] Amortization of purchased intangibles Schedule of Defined Benefit Plans Disclosures [Table] Schedule of Defined Benefit Plans Disclosures [Table] Fair Value, Inputs, Level 1 [Member] Fair Value, Inputs, Level 1 [Member] Fair Value, Inputs, Level 2 [Member] Fair Value, Inputs, Level 2 [Member] Schedule of Trading Securities and Other Trading Assets, Major Types of Trading Securities and Assets [Axis] Major Types of Debt and Equity Securities [Axis] Major Types of Trading Securities and Assets [Domain] Major Types of Debt and Equity Securities [Domain] Corporate Debt Securities [Member] Corporate Debt Securities [Member] Exchange Traded Funds [Member] Exchange Traded Funds [Member] Equity Securities [Member] Equity Securities [Member] Asset Backed Securities [Member] Asset-backed Securities [Member] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Trading Securities at Fair Value Trading Securities Marketable Securities Marketable Securities Performance bond reinvestment U.S. Treasuries Performance bond reinvestment U.S. Treasuries Performance bond reinvestment U.S. Treasuries Performance bond reinvestment U.S. Agency Securities Performance bond reinvestment U.S. Agency Securities Performance bond reinvestment U.S. Agency Securities Total Assets at Fair Value Assets, Fair Value Disclosure Subsequent Event [Table] Subsequent Event [Table] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Subsequent Event [Member] Subsequent Event [Member] Subsequent Event [Line Items] Subsequent Event [Line Items] Guarantees [Abstract] Guarantees Guarantees [Text Block] Statement of Cash Flows [Abstract] Cash Flows from Operating Activities Net Cash Provided by (Used in) Operating Activities [Abstract] Net income Adjustments to reconcile net income to net cash provided by operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Stock-based compensation Share-based Compensation Gain on sale of BM&FBOVESPA shares Gain (Loss) on Sale of Investments Debt prepayment costs Gains (Losses) on Extinguishment of Debt Loss on datacenter Asset Impairment Charges Undistributed earnings, net of losses, of unconsolidated subsidiaries Income (Loss) from Equity Method Investments, Net of Dividends or Distributions Deferred income taxes Deferred Income Tax Expense (Benefit) Change in: Increase (Decrease) in Operating Capital [Abstract] Accounts receivable Increase (Decrease) in Accounts Receivable Other current assets Increase (Decrease) in Prepaid Expense and Other Assets Other assets Increase (Decrease) in Other Operating Assets Accounts payable Increase (Decrease) in Accounts Payable Income taxes payable Increase (Decrease) in Income Taxes Payable Other current liabilities Increase (Decrease) in Other Accrued Liabilities Other liabilities Increase (Decrease) in Other Operating Liabilities Other Other Noncash Income (Expense) Net Cash Provided by Operating Activities Net Cash Provided by (Used in) Operating Activities Cash Flows from Investing Activities Net Cash Provided by (Used in) Investing Activities [Abstract] Proceeds from maturities of available-for-sale marketable securities Proceeds from Maturities, Prepayments and Calls of Available-for-sale Securities Purchases of available-for-sale marketable securities Payments to Acquire Available-for-sale Securities Purchases of available-for-sale marketable securities Payments to Acquire Property, Plant, and Equipment Investments in business ventures Payments to Acquire Investments Proceeds from Sale of Other Assets, Investing Activities Proceeds from Sale and Maturity of Other Investments Proceeds from sale of BM&FBOVESPA shares Proceeds from Sale of Available-for-sale Securities, Equity Settlement of derivative related to debt issuance Payments for (Proceeds from) Derivative Instrument, Investing Activities Net Cash Used in Investing Activities Net Cash Provided by (Used in) Investing Activities Cash Flows from Financing Activities Net Cash Provided by (Used in) Financing Activities [Abstract] Proceeds from debt, net of issuance costs Proceeds from Issuance of Long-term Debt Repayment of debt Repayments of Long-term Debt Cash dividends Payments of Dividends Proceeds from finance lease obligation Sale Leaseback Transaction, Gross Proceeds, Financing Activities Proceeds from exercise of stock options Proceeds from Stock Options Exercised Excess tax benefits related to employee option exercises and restricted stock vesting Excess Tax Benefit from Share-based Compensation, Financing Activities Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability Other Proceeds from (Payments for) Other Financing Activities Net Cash Used in Financing Activities Net Cash Provided by (Used in) Financing Activities Net change in cash and cash equivalents Cash and Cash Equivalents, Period Increase (Decrease) Cash and cash equivalents, beginning of period Cash and Cash Equivalents, at Carrying Value Cash and Cash Equivalents, End of Period Supplemental Disclosure of Cash Flow Information Supplemental Cash Flow Information [Abstract] Income taxes paid Income Taxes Paid Interest paid Interest Paid Accrued Proceeds from Sale of Investment Accrued Proceeds from Sale of Investment Accrued Proceeds from Sale of Investment Income Tax Disclosure [Abstract] Deferred Tax Assets, Gross, Current Deferred Tax Assets, Gross, Current Deferred income tax liabilities, net Deferred Tax Liabilities, Net, Noncurrent Deferred Tax Assets, Valuation Allowance, Noncurrent Deferred Tax Assets, Valuation Allowance, Noncurrent Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] $750.0 million fixed rate notes due September 2022, stated rate of 3.00% [Member] Seven Hundred Fifty Million Fixed Rate Notes Due March Two Thousand Twenty Two, Interest Equal To Three Point Zero Percent [Member] [Member] Seven Hundred Fifty Million Fixed Rate Notes Due March Two Thousand Twenty Two, Interest Equal To Three Point Zero Percent [Member] [Member] $750.0 million fixed rate notes due March 2025, stated rate of 3.00% [Member] $750.0 Million Fixed Rate Notes Due March 2025, Interest Equal To 3.00% [Member] Seven Hundred Fifty Million Fixed Rate Notes Due March Two Thousand Twenty Five, Interest Equal To Three Point Zero Percent [Member] [Member] [Member] $750.0 million fixed rate notes due September 2043, stated rate of 5.30% [Member] Seven Hundred Fifty Million Fixed Rate Notes Due March Two Thousand Forty Three, Interest Equal To Five Point Three Percent [Member] Seven Hundred Fifty Million Fixed Rate Notes Due March Two Thousand Forty Three, Interest Equal To Five Point Three Percent Debt Instrument, Fair Value Disclosure Debt Instrument, Fair Value Disclosure Debt Instrument, Face Amount Debt Instrument, Face Amount Debt Instrument, Maturity Date Debt Instrument, Maturity Date Debt Instrument, Interest Rate, Stated Percentage Debt Instrument, Interest Rate, Stated Percentage Guarantor Obligations, Nature [Axis] Guarantor Obligations, Nature [Axis] Guarantor Obligations, Nature [Domain] Guarantor Obligations, Nature [Domain] Family Farmer and Ranchers Protection Fund [Member] Family Farmer and Ranchers Protection Fund [Member] Family Farmer and Ranchers Protection Fund [Member] Agreement automatic renewal period (in years) Agreement Automatic Renewal, Period Agreement Automatic Renewal, Period Contingent liability to SGX, amount of irrevocable letters of credit Guarantee Collateral Guarantee Collateral Payment per participant PaymentPerParticipant PaymentPerParticipant Payment per cooperative PaymentPerCooperative PaymentPerCooperative FutureLosses FutureLosses FutureLosses Payments under Guarantee Payments under Guarantee Payments under Guarantee Guarantor Obligations, Maximum Exposure, Undiscounted Guarantor Obligations, Maximum Exposure, Undiscounted Remainder of 2016 Finite-Lived Intangible Assets, Amortization Expense, Remainder of Fiscal Year 2017 Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months 2018 Finite-Lived Intangible Assets, Amortization Expense, Year Two 2019 Finite-Lived Intangible Assets, Amortization Expense, Year Three 2020 Finite-Lived Intangible Assets, Amortization Expense, Year Four 2021 Finite-Lived Intangible Assets, Amortization Expense, Year Five Thereafter Finite-Lived Intangible Assets, Amortization Expense, after Year Five Schedule of Finite-Lived Intangible Assets [Table] Schedule of Finite-Lived Intangible Assets [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] Clearing Firm, Market Data And Other Customer Relationships [Member] Customer Relationships [Member] Technology-Related Intellectual Property [Member] Developed Technology Rights [Member] Other Intangible Assets [Member] Other Intangible Assets [Member] Total Amortizable Intangible Assets [Member] Finite-Lived Intangible Assets [Member] Indefinite-lived Intangible Assets by Major Class [Axis] Indefinite-lived Intangible Assets [Axis] Indefinite-lived Intangible Assets, Major Class Name [Domain] Indefinite-lived Intangible Assets, Major Class Name [Domain] Trade Names [Member] Trade Names [Member] Finite-Lived Intangible Assets [Line Items] Finite-Lived Intangible Assets [Line Items] Finite-Lived Intangible Assets, Gross Finite-Lived Intangible Assets, Gross Accumulated amortization Finite-Lived Intangible Assets, Accumulated Amortization Net book value Finite-Lived Intangible Assets, Net Indefinite-lived Intangible Assets Indefinite-Lived Intangible Assets (Excluding Goodwill) Other Indefinite-lived Intangible Assets Other Indefinite-lived Intangible Assets Other than Temporary Impairment Losses, Investments Other than Temporary Impairment Losses, Investments Earnings Per Share Earnings Per Share [Text Block] Income Tax Disclosure Income Tax Disclosure [Text Block] Statement, Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Common Stock And Additional Paid-In Capital [Member] Common Stock Including Additional Paid in Capital [Member] Retained Earnings [Member] Retained Earnings [Member] Balance (in shares) Net income Net Income (Loss) Attributable to Parent Dividends on common stock of $1.80 per share Dividends, Cash Adjustments to Additional Paid in Capital, Other Adjustments to Additional Paid in Capital, Other Exercise of stock options (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Exercise of stock options Stock Issued During Period, Value, Stock Options Exercised Excess tax benefits from option exercises and restricted stock vesting Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation Vesting of issued restricted Class A common stock, in shares Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures Vesting of issued restricted Class A common stock Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures Shares issued to Board of Directors, in shares Stock Issued To Related Parties During Period Shares Number of shares of stock issued during the period to related parties. Shares issued to Board of Directors Stock Issued To Related Parties During Period Value Value of stock issued during the period to related parties. Shares issued under Employee Stock Purchase Plan, in shares Stock Issued During Period, Shares, Employee Stock Purchase Plans Shares issued under Employee Stock Purchase Plan Stock Issued During Period, Value, Employee Stock Purchase Plan Stock-based compensation Stock Granted, Value, Share-based Compensation, Gross Balance (in shares) Debt Instrument [Line Items] Debt Instrument [Line Items] Long-term debt Unsecured Long-term Debt, Noncurrent Forward starting interest rate swap agreement fixed rate Forward starting interest rate swap agreement fixed rate Forward starting interest rate swap agreement, fixed rate Document and Entity Information [Abstract] Document and Entity Information [Abstract] Class B Common Stock, Class B-1 [Member] Class B Common Stock, Class B1 [member] Class B Common Stock, Class B1 [Member] Class B Common Stock, Class B-2 [Member] Class B Common Stock, Class B2 [member] Class B Common Stock, Class B2 [Member] Class B Common Stock, Class B-3 [Member] Class B Common Stock, Class B3 [Member] Class B Common Stock, Class B3 [Member] Class B Common Stock, Class B-4 [Member] Class B Common Stock, Class B4 [member] Class B Common Stock, Class B4 [Member] Document Type Document Type Amendment Flag Amendment Flag Document Period End Date Document Period End Date Document Fiscal Period Focus Document Fiscal Period Focus Document Fiscal Year Focus Document Fiscal Year Focus Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block] Basic And Diluted Earnings Per Share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Schedule of Accumulated Other Comprehensive Income (Loss) Comprehensive Income (Loss) Note [Text Block] Assets Assets [Abstract] Cash and cash equivalents Marketable securities Marketable Securities, Current Accounts receivable, net of allowance of $3.6 and $1.9 Accounts Receivable, Net, Current Other current assets (includes $29.5 and $32.0 in restricted cash) Other Assets, Current Performance bonds and guaranty fund contributions Good Faith and Margin Deposits with Broker-Dealers Total current assets Assets, Current Property, net of accumulated depreciation and amortization of $577.4 and $788.6 Property, Plant and Equipment, Net Intangible assets—trading products Intangible assets—other, net Intangible Assets, Net (Excluding Goodwill) Goodwill Goodwill Other assets (includes $64.4 and $70.5 in restricted cash) Other Assets, Noncurrent Total Assets Assets Liabilities and Equity Liabilities and Equity [Abstract] Accounts payable Accounts Payable, Current Other current liabilities Other Liabilities, Current Performance bonds and guaranty fund contributions Margin Deposits And Guaranty Funds Liabilities Current Margin Deposits And Guaranty Funds Liabilities Current. Total current liabilities Liabilities, Current Other liabilities Other Liabilities, Noncurrent Total Liabilities Liabilities Shareholders' Equity: Stockholders' Equity Attributable to Parent [Abstract] Preferred stock, $0.01 par value, 10,000 shares authorized at September 30, 2016 and December 31, 2015; none issued Preferred Stock, Value, Issued Common stock Common Stock, Value, Outstanding Additional paid-in capital Additional Paid in Capital, Common Stock Retained earnings Retained Earnings (Accumulated Deficit) Accumulated other comprehensive income (loss) Accumulated Other Comprehensive Income (Loss), Net of Tax Total shareholders’ equity Total Liabilities and Equity Liabilities and Equity Dilutive Securities, Effect on EPS Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements Diluted (in shares) Earnings per common share, basic (in dollars per share) Earnings per common share, diluted (in dollars per share) Other Commitments Other Commitments [Table Text Block] Remainder of 2016 Other Commitments, Future Minimum Payments, Remainder of Fiscal Year 2017 Other Commitment, Due in Second Year 2018 Other Commitment, Due in Third Year 2019 Other Commitment, Due in Fourth Year 2020 Other Commitment, Due in Fifth Year Thereafter Other Commitment, Due after Fifth Year Other Commitment Other Commitment Statement of Comprehensive Income [Abstract] Other comprehensive income (loss), net of tax: Other Comprehensive Income (Loss), Net of Tax [Abstract] Net unrealized holding gains (losses) arising during the period Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, before Tax Reclassification of net (gains) losses on sales included in investment income Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, before Tax Income tax benefit (expense) Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Tax Investment securities, net Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax Net change in defined benefit plans arising during the period Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, before Tax Amortization of net actuarial (gains) losses included in compensation and benefits expense Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Gain (Loss), before Tax Income tax benefit (expense) Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Tax Defined benefit plans, net Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax Net unrealized holding gains (losses) arising during the period Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax Ineffectiveness on cash flow hedges included in (gains) losses on derivative investments Loss on Cash Flow Hedge Ineffectiveness Amortization of effective portion of net (gains) losses on cash flow hedges included in interest expense Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, before Tax Income tax benefit (expense) Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Tax Derivative investments, net Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax Foreign currency translation adjustments Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, before Tax Income tax benefit (expense) Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax Foreign currency translation, net Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax Comprehensive Income Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Performance Bonds and Guaranty Fund Contributions Performance Bonds and Guaranty Fund Contributions [Text Block] Performance Bonds and Guaranty Fund Contributions [Text Block] Contingencies Contingencies Disclosure [Text Block] 2017 Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months 2018 Long-term Debt, Maturities, Repayments of Principal in Year Two 2019 Long-term Debt, Maturities, Repayments of Principal in Year Three 2020 Long-term Debt, Maturities, Repayments of Principal in Year Four 2021 Long-term Debt, Maturities, Repayments of Principal in Year Five Thereafter Long-term Debt, Maturities, Repayments of Principal after Year Five 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 Excluded from Computation of Earnings Per Share, by Antidilutive Securities [Axis] Antidilutive Securities [Axis] Antidilutive Securities, Name [Domain] Antidilutive Securities, Name [Domain] Stock Options [Member] Employee Stock Option [Member] Restricted Stock [Member] Restricted Stock [Member] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount