Statement of Financial Position [Abstract] Investments Investments [Abstract] Fixed Maturity Securities, Amortized Cost Available-for-sale Securities, Debt Maturities, Amortized Cost Basis Stockholders' Equity Stockholders' Equity Attributable to Parent [Abstract] Common Stock, Par Common Stock, Par or Stated Value Per Share Common Stock, Authorized Common Stock, Shares Authorized Common Stock, Issued Common Stock, Shares, Issued Treasury Stock, Shares at Cost Treasury Stock, Shares Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract] Comprehensive Income (Loss) Disclosure Comprehensive Income (Loss) Note [Text Block] Notes to Financial Statements [Abstract] Notes to Financial Statements [Abstract] Schedule of Available-for-sale Securities Reconciliation Schedule of Available-for-sale Securities Reconciliation [Table Text Block] Length of Time Fixed Maturity Securities had been in a Gross Unrealized Loss Position Schedule of Unrealized Loss on Investments [Table Text Block] Distribution of the Maturity Dates for Fixed Maturity Securities Investments Classified by Contractual Maturity Date [Table Text Block] Mortgage Loans by Property Type Mortgage Loans by Property Type Text Block Schedule Of Mortgage Loans By Property Type Text Block Mortgage Loans by Geographic Region Mortgage Loans by Geographic Region Schedule Of Mortgage Loans By Geographic Region Text Block Mortgage Loans, Sorted by Applicable Credit Quality Indicators, Internal Rating Mortgage Loans Sorted by Applicable Credit Quality Indicators Internal Rating Schedule Of Mortgage Loans By Credit Rating Text Block Mortgage Loans, Sorted by Applicable Credit Quality Indicators, Loan to Value Ratio Mortgage Loans by Applicable Credit Quality Indicators Loan to Value Ratio Schedule Of Mortgage Loans To Value Ratio Text Block Activity in the Allowance for Credit Losses Allowance for Credit Losses on Financing Receivables [Table Text Block] Impaired Mortgage Loans Impaired Financing Receivables [Table Text Block] Schedule of Financial Instrument and Derivative Offsetting Offsetting Assets and Liabilities [Table Text Block] Tabular disclosure of derivative and other financial assets that are subject to offsetting, including netting arrangements. Investment Income Investment Income [Table Text Block] Realized Investment Gains and Losses Reported in Consolidated Statements of Income Gain (Loss) on Investments [Table Text Block] Statement of Cash Flows [Abstract] Statement Statement [Table] Legal Entity Legal Entity [Axis] Entity Entity [Domain] Statement Statement [Line Items] Cash Flows from Operating Activities Net Cash Provided by (Used in) Operating Activities [Abstract] Net Income Net Income (Loss) Attributable to Parent 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] Change in Receivables Increase (Decrease) in Receivables Change in Deferred Acquisition Costs Increase (Decrease) in Deferred Policy Acquisition Costs Change in Insurance Reserves and Liabilities Increase (Decrease) in Insurance Liabilities Change in Income Taxes Increase (Decrease) in Income Taxes Payable Change in Other Accrued Liabilities Increase (Decrease) in Other Accrued Liabilities Non-cash Adjustments to Net Investment Income Increase (Decrease) in Accrued Investment Income Receivable Net Realized Investment Gain Realized Investment Gains (Losses) Depreciation Depreciation, Amortization and Accretion, Net Other, Net 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 Sales of Fixed Maturity Securities Proceeds from Sale of Available-for-sale Securities Proceeds from Maturities of Fixed Maturity Securities Proceeds from Maturities, Prepayments and Calls of Available-for-sale Securities Proceeds from Sales and Maturities of Other Investments Proceeds from Sale and Maturity of Other Investments Purchase of Fixed Maturity Securities Payments to Acquire Available-for-sale Securities Purchase of Other Investments Payments to Acquire Other Investments Net Sales (Purchases) of Short-term Investments Payments for (Proceeds from) Short-term Investments Other, Net Payments for (Proceeds from) Other Investing Activities Net Cash Provided (Used) by Investing Activities Net Cash Provided by (Used in) Investing Activities Cash Flows from Financing Activities Net Cash Provided by (Used in) Financing Activities [Abstract] Net Short-term Debt Repayments Proceeds from (Repayments of) Short-term Debt Issuance of Long-term Debt Proceeds from Debt, Net of Issuance Costs Long-term Debt Repayments Repayments of Long-term Debt Issuance of Common Stock Proceeds from Issuance of Common Stock Repurchase of Common Stock Payments for Repurchase of Common Stock Dividends Paid to Stockholders Payments of Dividends Other, Net Proceeds from (Payments for) Other Financing Activities Net Cash Provided (Used) by Financing Activities Net Cash Provided by (Used in) Financing Activities Net Increase (Decrease) in Cash and Bank Deposits Cash and Cash Equivalents, Period Increase (Decrease) Cash and Bank Deposits at Beginning of Year Cash Cash and Bank Deposits at End of Period Fair Values of Financial Instruments Fair Value Disclosures [Text Block] Commitments and Contingent Liabilities Commitments and Contingencies Disclosure [Text Block] Schedule of Segment Reporting Information, by Segment [Table] Unum U.S. Unum US [Member] Unum US [Member] Unum U.K. Unum UK [Member] Unum UK [Member] Colonial Life Colonial Life [Member] Colonial Life [Member] Closed Block Closed Block [Member] Closed Block [Member] Corporate Corporate and Other [Member] Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Assets Assets Schedule of Reclassifications from Accumulated Other Comprehensive Income to Income [Abstract] Schedule of Reclassifications from Accumulated Other Comprehensive Income to Income [Abstract] Schedule of Reclassifications from Accumulated Other Comprehensive Income to Income Schedule of Reclassifications from Accumulated Other Comprehensive Income to Income [Table] Schedule of Reclassifications from Accumulated Other Comprehensive Income to Income [Table] Income Statement Location Income Statement Location [Axis] Income Statement Location Income Statement Location [Domain] Net Realized Investments Gain Loss Net Realized Investments Gain Loss [Member] Net Realized Investments Gain (Loss) [Member] Net Investment Income Investment Income [Member] Interest and Debt Expense Interest Expense [Member] Other Expense Other Expense [Member] Income Tax Expense Income Tax Expense [Member] Income Tax Expense [Member] Derivative Instrument Risk Derivative Instrument [Axis] Derivative Contract Derivative Contract [Domain] Interest Rate Swaps Interest Rate Swap [Member] Foreign Exchange Contracts Foreign Exchange Contract [Member] Reclassifications from Accumulated Other Comprehensive Income to Income Schedule of Reclassifications from Accumulated Other Comprehensive Income to Income [Line Items] [Line Items] for Schedule of Reclassifications from Accumulated Other Comprehensive Income to Income [Table] Net Unrealized Gain on Securities Unrealized Gain (Loss) on Investments [Abstract] Before Tax Reclassification from AOCI for Sales of Securities Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, before Tax Before Tax Reclassification from AOCI for Write-down of Securities Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI for Write-down of Securities, before Tax Income Tax on Reclassifications from AOCI for Sales of Securities Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Tax After Tax Reclassifications from AOCI for Sales of Securities Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax Net Gain on Cash Flow Hedges Effect of Cash Flow Hedges on Results of Operations [Abstract] Before Tax Reclassification from AOCI on Derivatives Instruments Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, before Tax Income Tax on Reclassification from AOCI on Derivatives Instruments Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax After Tax Reclassification from AOCI on Derivatives Instruments Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax Unrecognized Pension and Postretirement Benefit Costs Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax, Portion Attributable to Parent [Abstract] Before Tax Reclassification from AOCI for Pension Net Actuarial Loss Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Gain (Loss), before Tax Before Tax Reclassification from AOCI for Pension Prior Service Credit Other Comprehensive (Income) Loss, Amortization Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Prior Service Cost (Credit), before Tax Before Tax Pension Plan Reclassification from AOCI Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, before Tax Income Tax on Pension Plan Reclassification from AOCI Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, Tax After Tax Pension Plan Reclassification from AOCI Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, Net of Tax Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Major Types of Debt and Equity Securities Major Types of Debt and Equity Securities [Axis] Major Types of Debt and Equity Securities Major Types of Debt and Equity Securities [Domain] States, Municipalities, and Political Subdivisions US States and Political Subdivisions Debt Securities [Member] Foreign Governments Foreign Government Debt Securities [Member] Public Utilities Public Utility, Bonds [Member] Mortgage/Asset-backed Securities Asset-backed Securities [Member] All Other Corporate Bonds All Other Corporate Bonds [Member] Redeemable Preferred Stocks Redeemable Preferred Stock [Member] Fixed Maturity Securities Debt Securities [Member] Equity Securites Equity Securities [Member] Embedded Derivative in Modified Coinsurance Arrangement Embedded Derivative Financial Instruments [Member] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Beginning of Period Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value Beginning of Period Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value Investment Gain (Loss) included in Earnings Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings Investment Gain (Loss) included in OCI Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss) Purchases Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases Sales Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales Level 3 Transfers Into Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3 Level 3 Transfers Out of Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3 End of Period End of Period Location and Fair Values of Derivative Financial Instruments [Abstract] Disclosure - Location and Fair Values of Derivative Financial Instruments [Abstract] Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table] Hedging Designation Hedging Designation [Axis] Hedging Designation Hedging Designation [Domain] Designated as Hedging Instrument Designated as Hedging Instrument [Member] Not Designated as Hedging Instrument Not Designated as Hedging Instrument [Member] Credit Default Swaps Credit Default Swap [Member] Derivative Instrument by Balance Sheet Location Balance Sheet Location [Axis] Balance Sheet Location Balance Sheet Location [Domain] Other Long-term Investments Other Long-term Investments [Member] Other Liability Other Liabilities [Member] Derivative Derivative [Line Items] Asset Derivatives Fair Value Derivative Asset, Fair Value, Gross Asset Liability Derivatives Fair Value Derivative Liability, Fair Value, Gross Liability Disclosure Mortgage Loans by Property Type [Abstract] Disclosure - Mortgage Loans by Property Type [Abstract] Mortgage Loans on Real Estate Schedule Mortgage Loans on Real Estate Schedule [Table] Mortgage Loan Property Type Real Estate, Type of Property [Axis] Mortgage Loan Property Type Real Estate [Domain] Apartment Apartment Building [Member] Industrial Industrial Property [Member] Office Office Building [Member] Retail Retail Site [Member] Mortgage Loans on Real Estate Mortgage Loans on Real Estate [Line Items] Mortgage Loans Mortgage Loans on Real Estate, Commercial and Consumer, Net Percent of Total Percentage of loan portfolio Percentage Of Loan Portfolio Assets Assets [Abstract] Fixed Maturity Securities - at fair value (amortized cost: $38,516.0; $38,289.6) Available-for-sale Securities Mortgage Loans Policy Loans Loans, Gross, Insurance Policy Other Long-term Investments Other Long-term Investments Short-term Investments Other Short-term Investments Total Investments Investments Other Assets Other Assets, Unclassified [Abstract] Cash and Bank Deposits Accounts and Premiums Receivable Premiums and Other Receivables, Net Reinsurance Recoverable Reinsurance Recoverables Accrued Investment Income Accrued Investment Income Receivable Deferred Acquisition Costs Deferred Policy Acquisition Costs Goodwill Goodwill Property and Equipment Property, Plant and Equipment, Net Income Tax Receivable Income Taxes Receivable Other Assets Other Assets Total Assets Liabilities and Stockholders' Equity Liabilities and Equity [Abstract] Liabilities Liabilities [Abstract] Policy and Contract Benefits Liability for Claims and Claims Adjustment Expense, Disability, Accident and Health Reserves for Future Policy and Contract Benefits Liability for Future Policy Benefits and Unpaid Claims and Claims Adjustment Expense Unearned Premiums Unearned Premiums Other Policyholders' Funds Other Policyholder Funds Income Tax Payable Taxes Payable Deferred Income Tax Deferred Tax Liabilities, Gross Short-term Debt Debt, Current Long-term Debt Long-term Debt and Capital Lease Obligations Other Liabilities Other Liabilities Total Liabilities Liabilities Commitments and Contingent Liabilities - Note 10 Commitments and Contingencies Common Stock, $0.10 par; authorized: 725,000,000 shares; issued: 361,265,467 and 360,802,426 shares Common Stock, Value, Issued Additional Paid-in Capital Additional Paid in Capital, Common Stock Accumulated Other Comprehensive Income Accumulated Other Comprehensive Income (Loss), Net of Tax Retained Earnings Retained Earnings (Accumulated Deficit) Treasury Stock - at cost: 103,703,671 and 100,785,012 shares Treasury Stock, Value Total Stockholders' Equity Stockholders' Equity Attributable to Parent Total Liabilities and Stockholders' Equity Liabilities and Equity Investments Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Segment Reporting [Abstract] Premium Income by Major Line of Business within Each Segment Revenue from External Customers by Products and Services [Table Text Block] Selected Operating Statement Data by Segment Schedule of Segment Reporting Information, by Segment [Table Text Block] Reconciliation of Operating Revenue and Operating Income by Segment to Revenue and Net Income Reconciliation of Revenue from Segments to Consolidated [Table Text Block] Assets by Segment Reconciliation of Assets from Segment to Consolidated [Table Text Block] Statement of Comprehensive Income [Abstract] Change in Net Unrealized Gain on Securities Before Adjustment, Tax Expense (Benefit) Other Comprehensive Income (Loss), Available-for-sale Securities, Tax Change in Adjustment to Deferred Acquisition Costs and Reserves for Future Policy and Contract Benefits, Net of Reinsurance, Tax Expense (Benefit) Change in Adjustment to Deferred Acquisition Costs and Reserves for Future Policy and Contract Benefits, Net of Reinsurance, Tax Expense Tax effect from the unrealized adjustment to deferred acquisition costs and reserves for future policy and contract benefits for unrealized loss on securities during the period net of the effects of contracts assumed and ceded Change in Net Gain on Cash Flow Hedges, Tax Expense (Benefit) Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Tax Change in Unrecognized Pension and Postretirement Benefit Costs, Tax Expense Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Tax Derivative Financial Instruments Additional Information [Abstract] Disclosure - Derivative Financial Instruments - Additional Information [Abstract] Derivative Derivative [Table] Foreign Currency Swap Currency Swap [Member] Receive Variable/Pay Fixed Derivative Financial Instruments Receive Variable Pay Fixed [Member] Derivative Financial Instruments, Receive Variable Pay Fixed [Member] Receive Fixed/Pay Variable Derivative Financial Instruments Receive Fixed Pay Variable [Member] Derivative Financial Instruments, Receive Fixed Pay Variable [Member] Derivative, by Nature Derivative, by Nature [Axis] Derivative Derivative, Name [Domain] Cash Flow Hedge Cash Flow Hedging [Member] Subsequent Event Type Subsequent Event Type [Axis] Subsequent Event Type Subsequent Event Type [Domain] Subsequent Event Subsequent Event [Member] Credit Exposure on Derivatives Derivative Asset, Fair Value, Amt Offset Against Collateral, including accrued interest receivable Derivative Asset, Fair Value, Amt Offset Against Collateral, including accrued interest receivable Cash collateral from counterparties Derivative, Collateral, Obligation to Return Cash Carrying value of fixed maturity securities posted as collateral to our counterparties Available-for-sale Securities Pledged as Collateral Cash Collateral to counterparties Derivative, Collateral, Right to Reclaim Cash Aggregate fair value of all derivative instruments with credit risk-related contingent features in a liability position Derivative, Net Liability Position, Aggregate Fair Value Derivative, Notional Amount Derivative, Notional Amount Material Ineffectiveness on Cash Flow Hedges Gain on Cash Flow Hedge Ineffectiveness Gain from Components Excluded from Assessment of Cash Flow Hedge Effectiveness Gain (Loss) from Components Excluded from Assessment of Cash Flow Hedge Effectiveness, Net Approximate amount of net deferred gains on derivative instruments expected to be amortized during the next twelve months Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months Change in Unrealized Gain (Loss) on Fair Value Hedging Instruments Change in Unrealized Gain (Loss) on Fair Value Hedging Instruments Material Ineffectiveness on Fair Value Hedges Gain on Fair Value Hedge Ineffectiveness Gain (Loss) from Components Excluded from Assessment of Fair Value Hedge Effectiveness, Net Gain (Loss) from Components Excluded from Assessment of Fair Value Hedge Effectiveness, Net Discontinued Hedge Accounting Due to Instrument No Longer Qualifying as FV Hedge Gain (Loss) from Hedged Firm Commitment Not Qualifying as Fair Value Hedge, Net Document Document and Entity Information [Abstract] Document - Document and Entity Information [Abstract] Entity Registrant Name Entity Registrant Name Trading Symbol Trading Symbol Entity Central Index Key Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Document Type Document Type Document Period End Date Document Period End Date Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Amendment Flag Amendment Flag Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Notional Amounts for Each Category of Derivative Activity [Abstract] Disclosure - Notional Amounts for Each Category of Derivative Activity [Abstract] Swaps Swap [Member] Forwards Forward Contracts [Member] Receive Fixed/Pay Fixed Derivative Financial Instruments Receive Fixed Pay Fixed [Member] Derivative Financial Instruments, Receive Fixed Pay Fixed [Member] Balance at beginning of period Additions Notional Amount Of Derivatives Additions Notional Amount Of Derivatives, Additions Terminations Notional Amount Of Derivatives Terminations Notional Amount Of Derivatives, Terminations Balance at ending of period Derivative Financial Instruments Derivative Instruments and Hedging Activities Disclosure [Text Block] Statement of Stockholders' Equity [Abstract] Equity Components Equity Components [Axis] Equity Component Equity Component [Domain] Retained Earnings Retained Earnings [Member] Common Stock Common Stock [Member] Dividends to Stockholders, per common share Common Stock, Dividends, Per Share, Cash Paid Stockholders' Equity Attributable to Parent Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net [Abstract] Net Realized Investment Gain (Loss) Realized Investment Gains (Losses) [Abstract] Credit Default Swap Loss Credit Default Swap Gain (Loss) The amount of gain (loss) recognized in income relating to credit default swap derivatives Gain on Embedded Derivative Embedded Derivative, Gain (Loss) on Embedded Derivative, Net Gains (Losses) on Derivatives Not Designated as Hedging Instruments Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net Schedule of Accumulated Other Comprehensive Income (Loss) Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Schedule of Components of Unrealized Gain (Loss) on Securities Unrealized Gain (Loss) on Investments [Table Text Block] Schedule of Reclassifications Out of Accumulated Other Comprehensive Income Reclassification out of Accumulated Other Comprehensive Income [Table Text Block] Accounting Policies [Abstract] Basis of Accounting, Policy Basis of Accounting, Policy [Policy Text Block] Earnings Per Share, Basic and Diluted [Abstract] Numerator Net Income (Loss) Attributable to Parent [Abstract] Denominator (000s) Weighted Average Number of Shares Outstanding Reconciliation [Abstract] Weighted Average Number of Shares Outstanding, Basic Weighted Average Number of Shares Outstanding, Basic Dilution for Assumed Exercises of Stock Options and Nonvested Stock Awards Weighted Average Number Diluted Shares Outstanding Adjustment Weighted Average Number of Shares Outstanding, Diluted Weighted Average Number of Shares Outstanding, Diluted Net Income Per Common Share Earnings Per Share [Abstract] Basic Earnings Per Share, Basic Assuming Dilution Earnings Per Share, Diluted New Accounting Pronouncements and Changes in Accounting Principles [Abstract] Accounting Changes Disclosure Accounting Changes [Text Block] Transfers of Assets between Level 1 and Level 2 [Abstract] Disclosure - Transfers of Assets between Level 1 and Level 2 [Abstract] Transfers of Securities Between Level 1 and Level 2 Fair Value Measurements, Recurring and Nonrecurring [Table] United States Government and Government Agencies and Authorities US Government and Government Agencies and Authorities [Member] Transfers Between Level 1 and Level 2 [Line Items] Transfers Between Level 1 and Level 2 [Line Items] Transfers Between Level 1 and Level 2 [Line Items] Level 1 to Level 2 Transfers Fair Value, Assets, Level 1 to Level 2 Transfers, Amount Level 2 to Level 1 Transfers Fair Value, Assets, Level 2 to Level 1 Transfers, Amount Quantitative Information Regarding Significant Unobservable Inputs [Abstract] Quantitative Information Regarding Significant Unobservable Inputs [Abstract] Quantitative Information Regarding Level 3 Inputs Fair Value Inputs, Assets and liabilities, Quantitative Information [Table] Fair Value Inputs, Assets and liabilities, Quantitative Information [Table] All Other Corporate Bonds - Private Corporate Bond Securities - Public Corporate Bond Securities [Member] Range Range [Axis] Range Range [Domain] Minimum Minimum [Member] Maximum Maximum [Member] Weighted Average Weighted Average [Member] Fair Value, Hierarchy Fair Value, Hierarchy [Axis] Fair Value Hierarchy Fair Value Hierarchy [Domain] Fair Value, Inputs, Level 3 Fair Value, Inputs, Level 3 [Member] Unobservable Input Unobservable Input [Axis] Unobservable Input [Axis] Unobservable Input Unobservable Input [Domain] [Domain] for Unobservable Input [Axis] Market Convention Market Convention [Member] Represents a decision to price based on par value, cost, or owner's equity when limited data is available Projected Cash Flows Projected Cash Flows [Member] Represents various actuarial assumptions required to derive the liability cash flows including incidence, termination, and lapse rates Quantitative Information Regarding Level 3 Inputs Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] Fair Value of Financial Instrument Using Internally Derived Unobservable Inputs Fair Value of Financial Instrument Using Internally Derived Unobservable Inputs Fair Values of Financial Instruments Using Internally Derived Unobservable Inputs Change in Benchmark Reference Fair Value Inputs, Change in Benchmark Reference Fair Value Inputs, Change in Benchmark Reference Comparability Adjustments Fair Value Inputs, Comparability Adjustments Discount for Size Fair Value Inputs, Discount for Size Fair Value Inputs, Discount for Size Lack of Marketability Fair Value Inputs, Discount for Lack of Marketability Volatility of Credit Fair Value Inputs, Entity Credit Risk Significant Assumptions to Calculating Fair Value of Level 3 Instrument Fair Value Measurements, Significant Assumptions Mortgage Loans by Applicable Credit Quality Indicators Loan to Value Ratio [Abstract] Disclosure - Mortgage Loans, Sorted by Applicable Credit Quality Indicators, Loan to Value Ratio [Abstract] Financing Receivable by Receivable Type Receivable Type [Axis] Receivable Type Receivable [Domain] Loan to Value Ratio Below or Equal to 65 Percent Loan to Value Ratio Below or Equal to 65 Percent [Member] Loan to Value Ratio Below or Equal to 65 Percent [Member] Loan To Value Ratio Above 65 To 75 Percent Loan To Value Ratio Above 65 To 75 Percent [Member] Loan To Value Ratio Above 65 To 75 Percent [Member] Loan To Value Ratio Above 75 To 85 Percent Loan To Value Ratio Above 75 To 85 Percent [Member] Loan To Value Ratio Above 75 To 85 Percent [Member] Loan To Value Ratio Above 85 Percent Loan To Value Ratio Above 85 Percent [Member] Loan To Value Ratio Above 85 Percent [Member] Length of Time Fixed Maturity Securities had been in a Gross Unrealized Loss Position [Abstract] Length of Time Fixed Maturity Securities had been in a Gross Unrealized Loss Position [Abstract] Schedule of Available-for-sale Securities Schedule of Available-for-sale Securities [Table] Schedule of Available-for-sale Securities Schedule of Available-for-sale Securities [Line Items] Fair Value of Securities in Continuous Unrealized Loss Possition for Less Than 12 Months Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value Aggregate Loss Position of Securities in Unrealized Loss Position for Less Than 12 Months Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss Fair Value of Securities in Continuous Unrealized Loss Possition for Greater Than 12 Months Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value Aggregate Loss Position of Securities in Unrealized Loss Position for Greater Than 12 Months Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss Commitments and Contingent Liabilities Additional Information [Abstract] Disclosure - Commitments and Contingent Liabilities - Additional Information [Abstract] Interest on undrawn retained asset account funds Interest on undrawn retained asset account funds Interest on undrawn retained asset account funds - Maine late payament statute Loss Contingency, Damages Awarded, Value Loss Contingency, Damages Awarded, Value Loss Contingency, Prejudgment Interest Awarded Loss Contingency, Prejudgment Interest Awarded Prejudgment interest awarded in class action lawsuit Schedule of Segment Reporting Information, by Segment Insurance Product Line Insurance Product Line [Axis] Insurance Product Line Insurance Product Line [Domain] Group Long term Disability Group Long term Disability [Member] Group Long Term Disability [Member] Group Short term Disability Group Short term Disability [Member] Group Short Term Disability [Member] Group Life Group Life [Member] Group Life [Member] Accidental Death Dismemberment Accidental Death Dismemberment [Member] Accidental Death And Dismemberment [Member] Individual Disability Recently Issued Individual Disability Recently Issued [Member] Individual Disability Recently Issued [Member] Voluntary Benefits Voluntary Benefits [Member] Voluntary Benefits [Member] Supplemental and Voluntary Insurance Supplemental and Voluntary Insurance [Member] Supplemental and Voluntary Insurance [Member] Accident and Health Insurance Segment Accident and Health Insurance Product Line [Member] Life Insurance Product Line Life Insurance Product Line [Member] Cancer and Critical Illness Colonial Cancer and Critical Illness Colonial [Member] Cancer And Critical Illness - Colonial [Member] Individual Disability Insurance Individual Disability Insurance [Member] Individual Disability Insurance [Member] Long-term Care Long term Care [Member] Long Term Care [Member] Other Insurance Product Line Other Insurance Product Line [Member] Premium Income Premiums Earned, Net Authorized share repurchase programs [Abstract] Authorized share repurchase programs [Abstract] Authorized Common Stock Repurchase Programs Authorized common stock repurchase programs [Table] Authorized common stock repurchase programs [Table] Share Repurchase Program Share Repurchase Program [Axis] Share Repurchase Program Share Repurchase Program [Domain] Repurchase Program Authorized in July 2012 Repurchase Program Authorized in July 2012 [Member] Repurchase Program Authorized in July 2012 [Member] Repurchase Program Authorized in December 2013 Repurchase Program Authorized in December 2013 [Member] Repurchase Program Authorized in December 2013 [Member] Authorized Common Stock Repurchase Programs Authorized common stock repurchase programs [Line Items] [Line Items] for Authorized common stock repurchase programs [Table] Stock Repurchase Program, Authorized Amount Stock Repurchase Program, Authorized Amount Stock Repurchase Program, Remaining Authorized Repurchase Amount Stock Repurchase Program, Remaining Authorized Repurchase Amount Carrying Amount and Fair Value of Financial Instruments Fair Value, by Balance Sheet Grouping [Table Text Block] Fair Values by Fair Value Heirarchy Input Level Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Transfers of Assets between Level 1 and Level 2 Fair Value Measurments Transfers of Assets between Level 1 and Level 2 Disclosure of the transfers between Level 1 and Level 2 during the period. Changes in Assets and Liabilities Measured at Fair Value using Significant Unobservable Inputs Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] Quantitative Information Regarding Significant Unobservable Inputs Fair Value Inputs, Assets, Quantitative Information [Table Text Block] Number of Operating Segments Number of Operating Segments Basis of Presentation Basis of Accounting [Text Block] Schedule of Impaired Financing Receivable [Table] Impaired Financing Receivable Impaired Financing Receivable [Axis] Impaired Financing Receivable [Axis] Impaired Financing Receivable Impaired Financing Receivable [Domain] Impaired Financing Receivable [Domain] Impaired Fin Receivables with Allowance Impaired Fin Receivables with Allowance [Member] Impaired Fin Receivables with Related Allowance [Member] Recorded Investment Impaired Financing Receivable, Recorded Investment Unpaid Principal Balance Impaired Financing Receivable, Unpaid Principal Balance Related Allowance Impaired Financing Receivable, Related Allowance Other Comprehensive Income (Loss) Other Comprehensive Income (Loss), Net of Tax [Abstract] Change in Net Unrealized Gain on Securities Before Adjustment (net of tax expense (benefit) of $371.1; $(159.4) Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax Change in Adjustment to Deferred Acquisition Costs and Reserves for Future Policy and Contract Benefits, Net of Reinsurance (net of tax expense (benefit) of $(272.0); $108.6 Change in Adjustment to Deferred Acquisition Costs and Reserves for Future Policy and Contract Benefits, Net of Reinsurance and Net of Tax Expense Benefit Unrealized adjustment to deferred acquisition costs and reserves for future policy and contract benefits for unrealized loss on securities during the period net of the effects of contracts assumed and ceded, net of tax. Change in Net Gain on Cash Flow Hedges (net of tax expense (benefit) of $1.0; $(0.2) Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax Change in Foreign Currency Translation Adjustment Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax Change in Unrecognized Pension and Postretirement Benefit Costs (net of tax expense of $0.3; $5.5) Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax Total Other Comprehensive Income (Loss) Other Comprehensive Income (Loss), Net of Tax Comprehensive Income Comprehensive Income (Loss), Net of Tax, Attributable to Parent Additional Paid-in Capital Additional Paid-in Capital [Member] Accumulated Other Comprehensive Income Accumulated Other Comprehensive Income (Loss) [Member] Treasury Stock Treasury Stock [Member] Balance at Beginning of Year Common Stock Activity Stock Issued During Period, Value, New Issues Other Comprehensive Income (Loss) Dividends to Stockholders (per common share: $0.145; $0.130) Dividends, Cash Purchases of Treasury Stock Treasury Stock, Value, Acquired, Cost Method Balance at End of Period Repurchases of Common Shares [Abstract] Repurchases of Common Shares [Abstract] Number of Shares Repurchased Treasury Stock, Shares, Acquired Cost of Shares Repurchased Stockholders' Equity Note [Abstract] Stockholders Equity and Earnings Per Common Share Stockholders Equity and Earnings Per Common Share The entire disclosure for stockholders equity and earnings per share Defined Benefit Pension Plans and Defined Benefit Postretirement Plans Disclosure [Abstract] Schedule of Net Benefit Costs Schedule of Net Benefit Costs [Table Text Block] Available-for-sale Securities, Amortized Cost Basis Available-for-sale Securities, Amortized Cost Basis Gross Unrealized Gain Available-for-sale Securities, Gross Unrealized Gain Gross Unrealized Loss Available-for-sale Securities, Gross Unrealized Loss Fixed Maturity Securities Location of Gains and Losses on Derivative Financial Instruments Designated as Cash Flow Hedging Instruments [Abstract] Disclosure - Location of Gains and Losses on Derivative Financial Instruments Designated as Cash Flow Hedging Instruments [Abstract] Derivative Instruments, Gain (Loss) by Hedging Relationship, by Income Statement Location, by Derivative Instrument Risk Derivative Instruments, Gain (Loss) [Table] Net Realized Investments Gain (Loss) Derivative Instruments, Gain (Loss) Derivative Instruments, Gain (Loss) [Line Items] Gain (Loss) Recognized in OCI on Derivatives (Effective Portion) Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion) Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract] Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Table] Defined Benefit Plans and Other Postretirement Benefit Plans Defined Benefit Plans and Other Postretirement Benefit Plans [Axis] Defined Benefit Plan and Other Postretirement Benefit Plan Defined Benefit Plan and Other Postretirement Benefit Plan [Domain] U.S. Plans United States Pension Plan of US Entity, Defined Benefit [Member] U.K. Plans Foreign Pension Plan, Defined Benefit [Member] OPEB Plan Other Postretirement Benefit Plan, Defined Benefit [Member] Defined Benefit Plan and Other Postretirement Benefit Plans Disclosure Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] Service Cost Defined Benefit Plan, Service Cost Interest Cost Defined Benefit Plan, Interest Cost Expected Return on Plan Assets Defined Benefit Plan, Expected Return on Plan Assets Amortization of Net Actuarial Loss Defined Benefit Plan, Amortization of Gains (Losses) Prior Service Credit Defined Benefit Plan, Amortization of Prior Service Cost (Credit) Net Periodic Benefit Cost Defined Benefit Plan, Net Periodic Benefit Cost Disclosure Mortgage Loans by Geographic Region [Abstract] Disclosure - Mortgage Loans by Geographic Region [Abstract] Region Reporting Information Investment Geographic Region [Axis] Reporting Region [Domain] Investment Geographic Region [Domain] New England New England [Member] New England [Member] Mid-Atlantic Middle Atlantic [Member] Middle Atlantic [Member] East North Central East North Central [Member] East North Central [Member] West North Central West North Central [Member] West North Central [Member] South Atlantic South Atlantic [Member] South Atlantic [Member] East South Central East South Central [Member] East South Central [Member] West South Central West South Central [Member] West South Central [Member] Mountain Mountain [Member] Mountain [Member] Pacific Pacific [Member] Pacific [Member] Operating Revenue Operating Revenue Operating Revenue Net Realized Investment Gain Total Revenue Revenues Operating Income Operating Income (Loss) Net Realized Investment Gain Non-operating Retirement-related Loss Non-operating Retirement-related Loss Non-operating Retirement-related Loss Income Before Income Tax Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest Offsetting for Derivatives and Securities Lending Balances [Abstract] Offsetting for Derivatives and Securities Lending Balances [Abstract] Offsetting Assets [Abstract] Offsetting Assets [Abstract] Offsetting Assets [Abstract] Offsetting Derivative Assets Offsetting Derivative Assets [Abstract] Gross Derivative Assets Derivative Assets, Gross Liability Offset Derivative Asset, Fair Value, Gross Liability Derivative Assets, Amount Not Offset Against Collateral Derivative Asset, Fair Value, Amount Not Offset Against Collateral Obligation to Return Securities on Derivative Assets Derivative, Collateral, Obligation to Return Securities Obligation to Return Cash on Derivative Assets Derivative Assets, Amount Offset Against Collateral Derivative Asset, Fair Value, Amount Offset Against Collateral Offsetting Securities Borrowed Offsetting Securities Borrowed [Abstract] Gross Securities Borrowed Securities Borrowed, Gross Securities Borrowed, Liability Offset Securities Borrowed, Liability Securities Borrowed Securities Borrowed Obligation to Return Securities on Securities Borrowed Securities Borrowed, Collateral, Obligation to Return Securities Obligation to Return Cash on Securities Borrowed Securities Borrowed, Collateral, Obligation to Return Cash Securities Borrowed, Amount Offset Against Collateral Securities Borrowed, Amount Offset Against Collateral Offsetting Derivative Asset, Securities Purchased under Agreements to Resell, Securities Borrowed Offsetting Derivative Asset, Securities Purchased under Agreements to Resell, Securities Borrowed [Abstract] Derivative Asset, Securities Purchased under Agreements to Resell, Securities Borrowed, Gross Derivative Asset, Securities Purchased under Agreements to Resell, Securities Borrowed, Gross Derivative Asset, Securities Purchased under Agreements to Resell, Securities Borrowed, Liability Derivative Asset, Securities Purchased under Agreements to Resell, Securities Borrowed, Liability Derivative Asset, Securities Purchased under Agreements to Resell, Securities Borrowed Derivative Asset, Securities Purchased under Agreements to Resell, Securities Borrowed Derivative Assets and Securities Lending Assets, Obligation to Return Securities Derivative Asset, Securities Purchased under Agreements to Resell, Securities Borrowed, Collateral, Obligation to Return Securities Derivative Assets and Securities Lending Assets, Obligation to Return Cash Derivative Asset, Securities Purchased under Agreements to Resell, Securities Borrowed, Collateral, Obligation to Return Cash Derivative Assets and Securities Lending Assets, Amount Offset Against Collateral Derivative Asset, Securities Purchased under Agreements to Resell, Securities Borrowed, Amount Offset Against Collateral Offsetting Liabilities Offsetting Liabilities [Abstract] Offsetting Liabilities [Abstract] Offsetting Derivative Liabilities Offsetting Derivative Liabilities [Abstract] Gross Derivative Liabilities Derivative Liabilities, Gross Asset Offset Derivative Liability, Fair Value, Gross Asset Derivative Liabilities, Amount Not Offset Against Collateral Derivative Liability, Fair Value, Amount Not Offset Against Collateral Right to Reclaim Securities on Derivative Liabilities Derivative, Collateral, Right to Reclaim Securities Right to Reclaim Cash on Derivative Liabilities Derivative Liability, Amount Offset Against Collateral Derivative Liability, Fair Value, Amount Offset Against Collateral Offsetting Securities Loaned Offsetting Securities Loaned [Abstract] Gross Securities Loaned Securities Loaned, Gross Securities Loaned, Asset Securities Loaned, Asset Securities Loaned Securities Loaned Right to Reclaim Securities on Securities Loaned Securities Loaned, Collateral, Right to Reclaim Securities Right to Reclaim Cash on Securities Loaned Securities Loaned, Collateral, Right to Reclaim Cash Securities Loaned, Amount Offset Against Collateral Securities Loaned, Amount Offset Against Collateral Derivative Liabilities and Securities Lending Liabilities Offsetting Derivative Liability, Securities Sold under Agreements to Resell, Securities Loaned [Abstract] Derivative Liability and Securities Lending Liabilities, Gross Derivative Liability, Securities Sold under Agreements to Resell, Securities Loaned, Gross Derivative Liability and Securities Lending Liabilities, Asset Offset Derivative Liability, Securities Sold under Agreements to Resell, Securities Loaned, Asset Derivative Liability and Securities Lending Liabilities, Securities Loaned Derivative Liability, Securities Sold under Agreements to Resell, Securities Loaned Derivative Liability and Securities Lending Liabilities, Right to Reclaim Securities Derivative Liability, Securities Sold under Agreements to Resell, Securities Loaned, Collateral, Right to Reclaim Securities Derivative Liability and Securities Lending Liabilities, Right to Reclaim Cash Derivative Liability, Securities Sold under Agreements to Resell, Securities Loaned, Collateral, Right to Reclaim Cash Derivative Liability and Securities Lending Liabilities, Amount Offset Against Collateral Derivative Liability, Securities Sold under Agreements to Resell, Securities Loaned, Amount Offset Against Collateral Schedule of Earnings Per Share, Basic and Diluted Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Authorized Common Stock Repurchase Programs Authorized common stock repurchase programs [Table Text Block] [Table Text Block] for Authorized common stock repurchase programs [Table] Share Repurchase Table Share Repurchase Table [Table Text Block] [Table Text Block] for Share Repurchase Table [Table] Accumulated Other Comprehensive Income Accumulated Other Comprehensive Income (Loss) [Table] Net Unrealized Gain on Securities Accumulated Net Unrealized Investment Gain (Loss) [Member] Net Gain on Cash Flow Hedges Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] Foreign Currency Translation Adjustment Accumulated Translation Adjustment [Member] Unrecognized Pension and Postretirement Benefit Costs Accumulated Defined Benefit Plans Adjustment [Member] Accumulated Other Comprehensive Income Accumulated Other Comprehensive Income (Loss) [Line Items] Balance, Beginning of Period After Tax Other Comprehensive Income Before Reclassifications Other Comprehensive Income (Loss), before Reclassifications, Net of Tax Reclassifications from Accumulated Other Comprehensive Income, Net of Tax Current Period Reclassifications From Accumulated Other Comprehensive Income, Net of Tax Current Period Reclassifications From Accumulated Other Comprehensive Income, Net of Tax Net Other Comprehensive Income (Loss) Balance, End of Period Disclosure Activity in Allowance for Credit Losses [Abstract] Disclosure - Activity in Allowance for Credit Losses [Abstract] Balance at Beginning of Year Financing Receivable, Allowance for Credit Losses Provisions Provision for Loan, Lease, and Other Losses Balance at End of Period Debt - Additional Information [Abstract] Debt - Additional Information [Abstract] Debt Narrative Detail Information Debt Narrative Detail Information [Table] Debt Narrative Detail Information Debt to be Redeemed in the Second Quarter of 2014 Debt to be Redeemed in the Second Quarter of 2014 [Member] Debt to be Redeemed in the Second Quarter of 2014 [Member] Debt Instrument Debt Instrument [Axis] Debt Instrument, Name Debt Instrument, Name [Domain] Debt Issued in the First Quarter of 2014 Debt Issued in the First Quarter of 2014 [Member] Debt Issued in the First Quarter of 2014 [Member] Long-term Debt, Type Long-term Debt, Type [Axis] Long-term Debt, Type Long-term Debt, Type [Domain] Northwind Holdings LLC Northwind Holdings LLC [Member] Northwind Holdings LLC [Member] Tailwind Holdings LLC Tailwind Holdings LLC [Member] Tailwind Holdings LLC [Member] Debt Narrative Detail Information Debt Narrative Detail Information [Line Items] [Line Items] for Debt Narrative Detail Information Amount Outstanding on Revolving Credit Facility Line of Credit Facility, Amount Outstanding Gross Proceeds from Issuance of Long-term Debt Proceeds from Issuance of Long-term Debt Interest Rate on Debt Debt Instrument, Interest Rate, Stated Percentage Periodic Principal Payments on Long-term Debt Debt Instrument, Periodic Payment, Principal Repayments of Long-term Debt Gain on Extinguishment of Debt Gains (Losses) on Extinguishment of Debt Notional Amounts for Each Category of Derivative Activity Schedule of Derivative Instruments [Table Text Block] Location and Fair Values of Derivative Financial Instruments Schedule of Derivative Instruments in Statement of Financial Position, Fair Value [Table Text Block] Location of Gains and Losses on Derivative Instruments Designated as Cash Flow Hedging Instruments Schedule of Derivative Instruments, Effect on Other Comprehensive Income (Loss) [Table Text Block] Location of and Gain (Loss) on Derivatives Not Designated as Hedging Instruments Location of and Gain (Loss) on Derivatives Not Designated as Hedging Instruments [Table Text Block] [Table Text Block] for Location of and Gain (Loss) on Derivatives Not Designated as Hedging Instruments [Table] Segment Information Segment Reporting Disclosure [Text Block] Investment Income [Abstract] Investment Income [Abstract] Schedule of Investment Income, Reported Amounts, by Category Investment Income [Table] Investment Type Investment Type [Axis] Investment Type Categorization Investments [Domain] Fixed Income Securities Fixed Income Securities [Member] Derivative Derivative [Member] Mortgage Receivable Mortgage Receivable [Member] Policy Loans Policy Loans [Member] Short-term Investments Short-term Investments [Member] Schedule of Investment Income, Reported Amounts, by Category Net Investment Income [Line Items] Investment Income, Interest and Dividend Investment Income, Interest and Dividend Less Investment Expenses Investment Income, Investment Expense Less Investment Income on PFA Assets Investment Income on PFA Assets Investment Income Participation Fund Account Assets Less Amortization of Tax Credit Partnerships Income Tax Credits and Adjustments Net Investment Income Net Investment Income Net Investment Income Other Income Other Income Operating Revenue Operating Income (Loss) Mortgage Loans Sorted by Applicable Credit Quality Indicators Internal Rating [Abstract] Disclosure - Mortgage Loans, Sorted by Applicable Credit Quality Indicators, Internal rating [Abstract] Internal Credit Assessment Internal Credit Assessment [Axis] Internal Credit Assessment Internal Credit Assessment [Domain] AA Credit Rating AA Credit Rating [Member] AA Credit Rating [Member] A Credit Rating A Credit Rating [Member] A Credit Rating [Member] Baa Credit Rating Baa Credit Rating [Member] Baa Credit Rating [Member] Ba Credit Rating Ba Credit Rating [Member] Ba Credit Rating [Member] B Credit Rating B Credit Rating [Member] B Credit Rating [Member] Schedule of Net Unrealized Gain on Securities [Abstract] Schedule of Net Unrealized Gain on Securities [Abstract] Schedule of Net Unrealized Gain on Securities Schedule of Net Unrealized Gain on Securities [Table] Schedule of Net Unrealized Gain on Securities [Table] Component of Net Unrealized Gain on Securities Component of Net Unrealized Gain on Securities [Axis] Component of Net Unrealized Gain on Securities [Axis] Component of Net Unrealized Gain on Securities Component of Net Unrealized Gain on Securities [Domain] [Domain] for Component of Net Unrealized Gain on Securities [Axis] Other Investments Other Investments [Member] Deferred Acquisition Costs Deferred Acquisition Costs [Member] Deferred Acquisition Costs [Member] Reserve for Future Policy and Contract Benefits Reserve for Future Policy and Contract Benefits [Member] Reserve for Future Policy and Contract Benefits [Member] Reinsurance Recoverable Reinsurance Recoverable [Member] Reinsurance Recoverable [Member] Deferred Income Tax Charges Deferred Income Tax Charge [Member] Schedule of Net Unrealized Gain on Securities Schedule of Net Unrealized Gain on Securities [Line Items] [Line Items] for Schedule of Net Unrealized Gain on Securities [Table] Change in Components of Net Unrealized Gain on Securities Change in Components of Net Unrealized Gain on Securities [Roll Forward] Change in Components of Net Unrealized Gain on Securities [Roll Forward] Beginning of Period Balance Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax Change in Net Unrealized Gain (Loss) on Securities End of Period Balance Fair Values of Financial Instruments Additional Information [Abstract] Disclosure - Fair Values of Financial Instruments - Additional Information [Abstract] Fair Value Measurements by Input Level Balance Sheet Location Ceded Policy Loans Ceded Policy Loans [Member] Ceded Policy Loans [Member] Other Than Fair Value Inputs Level 1 Fair Value Inputs Other Than Level 1 [Member] Fair Value Inputs Other Than Level 1 [Member] Fair Value, Inputs, Level 1 Fair Value, Inputs, Level 1 [Member] Fair Value, Inputs, Level 2 Fair Value, Inputs, Level 2 [Member] Fair Value Inputs Level 2 Or Level 3 Fair Value Inputs Level 2 Or Level 3 [Member] Fair Value Inputs Level 2 Or Level 3 [Member] Fair Value, Assets and Liabilities Components Fair Value, Assets and Liabilities Components [Axis] Fair Value, Assets and Liabilities Components Axis Fair Value, Assets and Liabilities Component Fair Value, Assets and Liabilities Component [Domain] Fair Value, Assets and Liabilities Component [Domain] Pricing Service Pricing Service [Member] Pricing Service [Member] Other Observable Market Data Other Observable Market Data [Member] Other Observable Market Data [Member] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Carrying amount of policy loans Private Equity Partnership Future Liquidation Term Private Equity Partnership Future Liquidation Term Private Equity Partnership Liquidation Term Percentage of Total Fair Value of Fixed Maturities Securities Available For Sale Securities Percent Of Total Fair Value Available For Sale Securities, Percent Of Total Fair Value Pension and Other Postretirement Benefits Disclosure Pension and Other Postretirement Benefits Disclosure [Text Block] Investments Additional Information [Abstract] Disclosure - Investments - Additional Information [Abstract] Schedule of Investments Schedule of Investments [Table] External Credit Rating by Grouping External Credit Rating by Grouping [Axis] External Credit Rating by Grouping External Credit Rating by Grouping [Domain] External Credit Rating, Investment Grade External Credit Rating, Investment Grade [Member] External Credit Rating, Non Investment Grade External Credit Rating, Non Investment Grade [Member] Variable Interest Entities by Classification of Entity Variable Interest Entities [Axis] Variable Interest Entity, Classification Variable Interest Entity, Classification [Domain] Partnership Interests In Tax Credit Investments Partnership Interests In Tax Credit Investments [Member] Partnership Interests In Tax Credit Investments [Member] Equity Method Investments Equity Method Investments [Member] Entity Classification Entity Classification [Axis] Entity Classification [Axis] Entity Classification Entity Classification [Domain] [Domain] for Entity Classification [Axis] Special Purpose Entity Special Purpose Entity [Member] Special Purpose Entity [Member] Summary of Investments, Other than Investments in Related Parties, by Type Summary of Investments, Other than Investments in Related Parties, by Type [Axis] Summary of Investments, by Type Summary of Investments, by Type [Domain] Bonds Bonds [Member] Partnership Interest Partnership Interest [Member] Class of Financing Receivable Class of Financing Receivable [Axis] Class of Financing Receivable Class of Financing Receivable [Domain] Nonperforming Financing Receivable Nonperforming Financing Receivable [Member] Schedule of Investments Schedule of Investments [Line Items] Fair value of fixed maturity securities Available-for-sale Securities, Debt Securities Fair value of fixed maturity securities, gross unrealized gain Fair Value of fixed maturity securities, gross unrealized loss Fixed maturity securities in unrealized loss position, percent of total Fixed maturity securities in unrealized loss position percent of total This item represents the gross unrealized losses for securities, at a point in time, which are categorized neither as held-to-maturity nor trading securities expressed as a percentage. Number of fixed maturity securities that were in an unrealized loss position Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions Number of fixed maturity securities in an unrealized loss position continuously for over one year Number of fixed maturity securities in an unrealized loss position continuously for over one year Available for Sale Securities Continuous Unrealized Loss Position, 12 Months Or Longer, Number of Positions Fixed Maturity Securities Other Than Temporary Impairments in Accumulated Other Comprehensive Income Loss Available for Sale Securities Other Than Temporary Impairments in Accumulated Other Comprehensive Income Loss Available-for-Sale Securities Other-Than-Temporary Impairments in Accumulated Other Comprehensive Income (Loss) Commitment to fund private placement fixed maturity securities Commitment to fund private placement fixed maturity securities Amount of non-binding funding commitments for private placement securities. Carrying amount of variable interest entity investments Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets Unfunded commitment to fund Investment Partnerships Unfunded commitment to fund tax credit partnership investments Unfunded Commitments and Standby Letters of Credit Commitment to fund partnership Equity Investments Commitment to fund partnership Equity Investments Commitment To Fund Partnership Equity Investments Commitments to Fund Special Purpose Entities Commitments to Fund Special Purpose Entities Commitments to Fund Special Purpose Entities Amount Funded to Special Purpose Entity Partnerships Amount Funded to Special Purpose Entity Partnerships Amount Funded to Special Purpose Entity Partnerships Mortgage Loan policy is not to exceed a loan-to-value ratio, percent Loan to value ratio maximum Loan To Value Ratio Maximum Loan to Value Ratio Update Frequency Loan to Value Ratio Update Frequency Loan to Value Ratio Update Frequency Mortgage Loan Inspection Frequency Mortgage Loan Inspection Frequency Mortgage Loan Inspection Frequency Mortage Loan Policy Debt Service coverage ratio lower range Mortage Loan Policy Debt Service coverage ratio lower range Mortage Loan Policy Debt Service coverage ratio lower range Mortgage Loans issuance, term years Mortgage loan policy, amortization period Mortgage loan policy, amortization period Number of Changes to Accounting Policy for Estimating Credit Losses on Mortgage Loans Number of Changes to Accounting Policy for Estimating Credit Losses on Mortgage Loans Number of Changes to Accounting Policy for Estimating Credit Losses on Mortgage Loans Number of Troubled Debt Restructurings During Period Financing Receivable, Modifications, Number of Contracts Pre-Modification Recorded Investment in Troubled Debt Restructuring Financing Receivable, Modifications, Pre-Modification Recorded Investment Impaired Financing Receivable, Related Allowance Financing Receivable, Modifications, Allowance Recorded During Period Financing Receivable, Modifications, Allowance Additions Recorded During Period Financing Receivable, Recorded Investment, Nonaccrual status Count of Financing Receivable, Recorded Investment, Nonaccrual status Number (Count) of Financing Receivable, Recorded Investment, Nonaccrual status Amount of days past due-DelinquentMortgageLoan Amount of days past due-DelinquentMortgageLoan Amount of days past due-DelinquentMortgageLoan Average Recorded Investment in Impaired Financing Receivable Impaired Financing Receivable, Average Recorded Investment Interest Income on Impaired Financing Receivable, Accrual Method Impaired Financing Receivable, Interest Income, Accrual Method Committments to Fund Commercial Mortgage Loans Committments to Fund Commercial Mortgage Loans Committments to Fund Commercial Mortgage Loans Repurchase agreements - Typical Days outstanding Repurchase Agreements, Maturities Minimum percent of the fair value of securities loaned or securities purchased under repurchase agreements be maintained as collateral Collateral Requirements Minimum Percentage Collateral To Fair Value Of Securities Loaned Or Purchased Under Repurchase Agreements Collateral Requirements, Minimum Percentage, Collateral To Fair Value Of Securities Loaned Or Purchased Under Repurchase Agreements Fixed Maturity Securities Loaned to Third Parties Collateral Received in Form of Cash Securities Received as Collateral Securities Received as Collateral Outstanding Repurchase Agreements Securities Sold under Agreements to Repurchase Fair Value, by Balance Sheet Grouping [Table] Measurement Basis Measurement Basis [Axis] Basis of Measurement Basis of Measurement [Domain] [Domain] for Basis of Measurement [Axis] Carrying Amount Reported Value Measurement [Member] Fair Value Portion at Fair Value Measurement [Member] Fair Value by Balance Sheet Grouping Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fixed Maturity Securities Other Long-term Investments Other Investments [Abstract] Derivative Assets Derivative Asset Equity Securities Marketable Securities, Equity Securities Miscellaneous Long-Term Investments Miscellaneous Long-Term Investments Miscellaneous Long-Term Investments Policyholders' Funds Policyholder Funds [Abstract] Deferred Annuity Products Deferred Annuity Products Deferred Annuity Products Supplementary Contracts without Life Contingencies Supplementary Contracts without Life Contingencies Supplementary Contracts Without Life Contingencies Other Liabilities Other Liabilities, Unclassified [Abstract] Derivative Liabilities Derivative Liability Embedded Derivative in Modified Coinsurance Arrangement Embedded Derivative, Fair Value of Embedded Derivative Liability Stockholders Equity and Earnings Per Common Share Additional Information [Abstract] Disclosure - Stockholders' Equity and Earnings Per Common Share - Additional Information [Abstract] Exercise Price Floor on Outstanding Stock Options Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Lower Range Limit Exercise Price Ceiling on Outstanding Stock Options Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Upper Range Limit Outstanding Restricted Stock Unit Grant Prices Lower Limit Outstanding Restricted Stock Unit Grant Prices Lower Limit Outstanding Restricted Stock Unit Grant Prices Lower Limit Outstanding Restricted Stock Unit Grant Prices Upper Limit Outstanding Restricted Stock Unit Grant Prices Upper Limit Outstanding Restricted Stock Unit Grant Prices Upper Limit Outstanding Performance Share Unit Awards Grant Price Range Lower Limit Outstanding Performance Share Unit Awards Grant Price Range Lower Limit Outstanding Performance Share Unit Awards Grant Price Range Lower Limit Outstanding Performance Share Unit Awards Grant Price Range Upper Limit Outstanding Performance Share Unit Awards Grant Price Range Upper Limit Outstanding Performance Share Unit Awards Grant Price Range Upper Limit Number of Antidilutive Securities Excluded from Computation of Earnings Per Share Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Authorized Shares of Preferred Stock Preferred Stock, Shares Authorized Par Value Per Share of Preferred Stock Preferred Stock, Par or Stated Value Per Share Issued Shares of Preferred Stock Preferred Stock, Shares Issued Realized Investment Gains and Losses Reported in Consolidated Statements of Income [Abstract] Disclosure - Realized Investment Gains and Losses Reported in Consolidated Statements of Income [Abstract] Fixed Maturity Securities Available-for-sale Securities [Abstract] Gross Gains on Sales Available-for-sale Securities, Gross Realized Gains Gross Losses on Sales Available-for-sale Securities, Gross Realized Losses Other-Than-Temporary Impairment Loss Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, Net Mortgage Loans and Other Invested Assets Gross Gains on Sales Other Investments Gross Realized Gains This item represents the gross profit realized on the sale of investments not otherwise specified in the taxonomy Other Investments Gross Realized Losses Other Investments Gross Realized Losses Other Investments Gross Realized Losses Impairment Loss Other than Temporary Impairment Losses, Investments Derivative, Gain (Loss) on Derivative, Net Derivative, Gain (Loss) on Derivative, Net Foreign Currency Transactions Foreign Currency Transaction Gain (Loss), before Tax Net Realized Investment Gain Gain (Loss) on Investments New Accounting Pronouncements Policy New Accounting Pronouncements, Policy [Policy Text Block] Income Statement [Abstract] Revenue Revenues [Abstract] Realized Investment Gain (Loss) Other-Than-Temporary Impairment Loss on Fixed Maturity Securities Marketable Securities, Realized Loss, Other than Temporary Impairments, Amount Net Realized Investment Gain, Excluding Other-Than-Temporary Impairment Loss on Fixed Maturity Securities Gain (Loss) on Investments, Excluding Other than Temporary Impairments Benefits and Expenses Benefits, Losses and Expenses [Abstract] Benefits and Change in Reserves for Future Benefits Policyholder Benefits and Claims Incurred, Net Commissions Insurance Commissions Interest and Debt Expense Interest and Debt Expense Deferral of Acquisition Costs Deferred Policy Acquisition Costs, Additions Amortization of Deferred Acquisition Costs Deferred Policy Acquisition Cost, Amortization Expense Compensation Expense Labor and Related Expense Other Expenses Other Cost and Expense, Operating Total Benefits and Expenses Benefits, Losses and Expenses Income Tax Income Tax Expense (Benefit), Continuing Operations [Abstract] Current Current Income Tax Expense (Benefit) Deferred Deferred Income Tax Expense (Benefit) Total Income Tax Income Tax Expense (Benefit) Net Income Debt Disclosure [Abstract] Debt Disclosure Debt Disclosure [Text Block] Distribution of the Maturity Dates for Fixed Maturity Securities [Abstract] Disclosure - Distribution of the Maturity Dates for Fixed Maturity Securities [Abstract] Gain (Loss) on Investments by Category Investments by Category [Axis] Marketable Securities and Investments Held at Cost Marketable Securities and Investments Held at Cost [Domain] Fair Value of Fixed Maturity Securities in Unrealized Gain Position Available for Sale Securities Unrealized Gain Position Fair Value [Member] Available For Sale Securities Gross Unrealized Gain [Member] Fair Value of Fixed Maturity Securities in Unrealized Loss Position Available for Sale Securities Unrealized Loss Position Fair Value [Member] Available For Sale Securities Gross Unrealized Loss [Member] Available-for-Sale Securities, Total Amortized Cost Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Fiscal Year Maturity [Abstract] 1 year or less Available-for-sale Securities, Debt Maturities, Next Twelve Months, Amortized Cost Basis Over 1 year through 5 years Available-for-sale Securities, Debt Maturities, Year Two Through Five, Amortized Cost Basis Over 5 years through 10 years Available-for-sale Securities, Debt Maturities, Year Six Through Ten, Amortized Cost Basis Over 10 years Available-for-sale Securities, Debt Maturities, after Ten Years, Amortized Cost Basis Available-for-sale Securities, Debt Maturities, Gross Subtotal Available for sale Securities Debt Maturities Amortized Cost Gross Subtotal Available-for-sale Securities, Debt Maturities, Amortized Cost, Gross Subtotal Mortgage/Asset-Backed Securities Available-for-sale Securities, Debt Maturities, without Single Maturity Date, Amortized Cost Basis Total Fixed Maturity Securities Available-for-Sale Securities, Unrealized Gain Position, Gross Gain Available for Sale Securities Unrealized Gain Position Gross Gain Available-For-Sale Securities, Debt Maturities Unrealized Gain Position Gross Gain Abstract 1 year or less Available For Sale Securities Debt Maturities Within One Year Unrealized Gain Position Gross Gain Available-For-Sale Securities, Debt Maturities Within One Year Unrealized Gain Position Gross Gain Over 1 year through 5 years Available For Sale Securities Debt Maturities After One Through Five Years Unrealized Gain Position Gross Gain Available-For-Sale-Securities, Debt Maturities After One Through Five Years Unrealized Gain Position Gross Gain Over 5 years through 10 years Available For Sale Securities Debt Maturities After Five Through Ten Years Unrealized Gain Position GrossGain Available-For-Sale Securities, Debt Maturities After Five Through Ten Years Unrealized Gain Position GrossGain Over 10 years Available For Sale Securities Debt Maturities After Ten Years Unrealized Gain Position Gross Gain Available-For-Sale, Securities Debt Maturities After Ten Years Unrealized Gain Position Gross Gain Available-For-Sale Securities, Debt Maturities Unrealized Gain Position, Gross Gain, Gross Subtotal Available For Sale Securities Debt Maturities Unrealized Gain Position Gross Gain Gross Subtotal Available-For-Sale Securities, Debt Maturities Unrealized Gain Position, Gross Gain, Gross Subtotal Mortgage/Asset-Backed Securities Available For Sale Securities Debt Maturities Without Single Maturity Date Unrealized Gain Position Gross Gain Available-For-Sale Securities, Debt Maturities Without Single Maturity Date Unrealized Gain Position Gross Gain Total Fixed Maturity Securities Available for sale Securities, Debt Maturities Unrealized Gain Position Gross Gain Available for sale Securities, Debt Maturities Unrealized Gain Position Gross Gain Fair Value Maturity Distribution Fair Value Maturity Distribution [Abstract] Fair Value Maturity Distribution [Abstract] 1 year or less Available-for-sale Securities, Debt Maturities, Next Twelve Months, Fair Value Over 1 year through 5 years Available-for-sale Securities, Debt Maturities, Year Two Through Five, Fair Value Over 5 years through 10 years Available-for-sale Securities, Debt Maturities, Year Six Through Ten, Fair Value Over 10 years Available-for-sale Securities, Debt Maturities, after Ten Years, Fair Value Available-for-sale Securities, Debt Maturities, Fair Value, Gross Subtotal Available for sale Securities Debt Maturities Fair Value Gross Subtotal Available-for-sale Securities, Debt Maturities, Fair Value, Gross Subtotal Mortgage/Asset-Backed Securities Available-for-sale Securities, Debt Maturities, without Single Maturity Date, Fair Value Total Fixed Maturity Securities Available-for-Sale Securities, Unrealized Loss Position, Gross Loss Available for Sale Securities Unrealized Loss Position Gross Loss Available-For-Sale Securities, Debt Maturities Unrealized Loss Position Gross Loss Abstract 1 year or less Available For Sale Securities Debt Maturities Within One Year Unrealized Loss Position Gross Loss Available-For-Sale Securities, Debt Maturities Within One Year Unrealized Loss Position Gross Loss Over 1 year through 5 years Available For Sale Securities Debt Maturities After One Through Five Years Unrealized Loss Position Gross Loss Available-For- Sale Securities, Debt Maturities After One Through Five Years Unrealized Loss PositionGrossLoss Over 5 years through 10 years Available For Sale Securities Debt Maturities After Five Through Ten Years Unrealized Loss PositionGross Loss Available-For-Sale Securities, Debt Maturities After Five Through Ten Years Unrealized Loss PositionGross Loss Over 10 years Available For Sale Securities Debt Maturities After Ten Years Unrealized Loss Position Gross Loss Available-For-Sale Securities, Debt Maturities After Ten Years Unrealized Loss Position Gross Loss Available-For-Sale Securities, Debt Maturities Unrealized Gain Position, Gross Loss, Gross Subtotal Available For Sale Securities Debt Maturities Unrealized Gain Position Gross Loss Gross Subtotal Available-For-Sale Securities, Debt Maturities Unrealized Gain Position, Gross Loss, Gross Subtotal Mortgage/Asset-Backed Securities Available For Sale Securities Debt Maturities Without Single Maturity Date Unrealized Loss Position Gross Loss Available-For-Sale Securities, Debt Maturities Without Single Maturity Date Unrealized Loss Position Gross Loss Total Fixed Maturity Securities Available For Sale Securities Unrealized Loss Position Gross Loss Subtoatl Available-For-Sale Securities, Unrealized Loss Position Gross Loss Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract] Derivative Assets Derivative Financial Instruments, Assets [Member] Derivative Liabilities Derivative Financial Instruments, Liabilities [Member] Fixed Maturity Securities Marketable Securities, Fixed Maturities [Abstract]