Statement of Cash Flows [Abstract] Cash Flows from Operating Activities Net Cash Provided by (Used in) Operating Activities [Abstract] Net Income (Loss) 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 Deferred Policy Acquisition Costs, Period Increase (Decrease) 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 Components of Net Investment Income Increase (Decrease) in Accrued Investment Income Receivable Net Realized Investment Gain Gain (Loss) on Investments 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 Debt Securities, Available-for-sale Proceeds from Maturities of Fixed Maturity Securities Proceeds from Maturities, Prepayments and Calls of Debt Securities, Available-for-sale Proceeds from Sales and Maturities of Other Investments Proceeds from Sale and Maturity of Other Investments Purchases of Fixed Maturity Securities Payments to Acquire Debt Securities, Available-for-sale Purchases of Other Investments Payments to Acquire Other Investments Net Purchases of Short-term Investments Payments for (Proceeds from) Short-term Investments Net Decrease in Payables for Collateral on Investments Increase (Decrease) in Cash Collateral for Loaned Securities Net Purchases of Property and Equipment Payments to Acquire Property, Plant, and Equipment Net Cash 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] Short-term Debt Repayments Maturities of Senior Debt Issuance of Long-term Debt Proceeds from Issuance of Long-term Debt Long-term Debt Repayments Proceeds from (Repayments of) Secured 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 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 Segment Reporting [Abstract] Schedule of Segment Reporting Information, by Segment Schedule of Segment Reporting Information, by Segment [Table] Consolidation Items Consolidation Items [Axis] Consolidation Items Consolidation Items [Domain] Operating Segments Operating Segments [Member] Segments Segments [Axis] Segments Segments [Domain] Unum US Unum US [Member] Unum US [Member] Unum UK Unum UK [Member] Unum UK [Member] Colonial Life Colonial Life [Member] Colonial Life [Member] Closed Block Closed Block [Member] Closed Block [Member] Insurance Product Line Product and Service [Axis] Insurance Product Line Product and Service [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 Individual Disability Recently Issued [Member] Individual Disability Recently Issued [Member] Voluntary Benefits Voluntary Benefits [Member] Voluntary Benefits [Member] Dental and Vision Dental and Vision [Member] Dental and Vision [Member] Supplemental Insurance Supplemental and Voluntary Insurance [Member] Supplemental and Voluntary Insurance [Member] Accident, Sickness, and Disability Insurance Accident and Health Insurance Product Line [Member] Life Life Insurance Product Line [Member] Cancer and Critical Illness 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] Segment Reporting Information Segment Reporting Information [Line Items] Premium Income Premiums Earned, Net Income Tax - Additional Information [Abstract] Income Tax - Additional Information [Abstract] Income Tax - Additional Information Income Tax - Additional Information [Table] Income Tax - Additional Information [Table] Tax Period Tax Period [Axis] Tax Period Tax Period [Domain] Tax Year 2017 Tax Year 2017 [Member] Income Tax Authority, Name Income Tax Authority, Name [Axis] Income Tax Authority, Name Income Tax Authority, Name [Domain] Internal Revenue Service (IRS) Internal Revenue Service (IRS) [Member] Income Tax - Additional Information Income Tax - Additional Information [Line Items] [Line Items] for Income Tax - Additional Information [Table] Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Provisional Income Tax Benefit Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Provisional Income Tax Benefit Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Provisional Income Tax Benefit Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Change in Tax Rate, Deferred Tax Liability, Provisional Income Tax Benefit Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Change in Tax Rate, Deferred Tax Liability, Provisional Income Tax Benefit Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Change in Tax Rate, Deferred Tax Liability, Provisional Income Tax Benefit Tax Cuts and Jobs Act of 2017, Accounting Complete Tax Cuts and Jobs Act of 2017, Accounting Complete Tax Cuts and Jobs Act of 2017, Accounting Complete Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Transition Tax for Accumulated Foreign Earnings, Provisional Income Tax Expense Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Transition Tax for Accumulated Foreign Earnings, Provisional Income Tax Expense Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Transition Tax for Accumulated Foreign Earnings, Provisional Income Tax Expense Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract] Reclassification out of Accumulated Other Comprehensive Income (Loss) Reclassification out of Accumulated Other Comprehensive Income [Table] Reclassification out of Accumulated Other Comprehensive Income (Loss) Reclassification out of Accumulated Other Comprehensive Income [Axis] Reclassification out of Accumulated Other Comprehensive Income (Loss) Reclassification out of Accumulated Other Comprehensive Income [Domain] Reclassification out of Accumulated Other Comprehensive Income or Loss Reclassification out of Accumulated Other Comprehensive Income [Member] Equity Components Equity Components [Axis] Equity Component Equity Component [Domain] Net Unrealized Gain (Loss) on Securities Accumulated Net Investment Gain (Loss) Attributable to Parent [Member] Net Gain on Hedges Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] Net Actuarial Loss Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member] Prior Service Credit Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent [Member] Unrecognized Pension and Postretirement Benefit Costs Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] Derivative Instrument Derivative Instrument [Axis] Derivative Contract Derivative Contract [Domain] Interest Rate Swaps Interest Rate Swap [Member] Foreign Exchange Contracts Foreign Exchange Contract [Member] Reclassification Adjustment out of Accumulated Other Comprehensive Income (Loss) Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] Net Gain on Sales of Securities and Other Invested Assets Debt and Equity Securities, Gain (Loss), Excluding Other-than-temporary Impairment Loss Other-Than-Temporary Impairment Loss on Fixed Maturity Securities Other-than-temporary Impairment Loss, Debt Securities, Portion Recognized in Earnings Net Investment Income Net Investment Income Derivative, Gain (Loss) on Derivative, Net Derivative, Gain (Loss) on Derivative, Net Interest and Debt Expense Interest and Debt Expense Other Expenses Other Cost and Expense, Operating Income Before Income Tax Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest Total Income Tax Expense (Benefit) Income Tax Expense (Benefit) Derivative Financial Instruments Additional Information [Abstract] Disclosure - Derivative Financial Instruments - Additional Information [Abstract] Derivative Derivative [Table] Interest Rate Derivatives Contract Type Interest Rate Derivatives Contract Type [Axis] Interest Rate Derivatives Contract Type [Axis] Interest Rate Derivative Contract Type Interest Rate Derivative Contract Type [Domain] Interest Rate Derivative Contract Type [Domain] Receive Fixed/Pay Fixed Derivative Financial Instruments Receive Fixed Pay Fixed [Member] Derivative Financial Instruments, Receive Fixed Pay Fixed [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] Credit Exposure Credit Exposure [Axis] Credit Exposure [Axis] Credit Exposure Credit Exposure [Domain] [Domain] for Credit Exposure [Axis] Credit Exposure Credit Exposure [Member] The current credit exposure on derivatives which is limited to the value of those contracts in a net gain position, including accrued interest receivable less collateral held. Credit Risk Contract Credit Risk Contract [Member] Hedging Relationship Hedging Relationship [Axis] Hedging Relationship Hedging Relationship [Domain] Cash Flow Hedging Cash Flow Hedging [Member] Fair Value Hedging Fair Value Hedging [Member] Credit Derivatives Contract Type Credit Derivatives Contract Type [Axis] Credit Derivatives Contract Type Credit Derivatives Contract Type [Domain] Credit Default Swaps Credit Default Swap [Member] 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] Derivative Derivative [Line Items] Current Credit Exposure on Derivatives Fair Value, Concentration of Risk, Derivative Instruments, Assets Aggregate Fair Value of all Derivative Instruments with Credit Risk-related Contingent Features in a Liability Position Derivative, Net Liability Position, Aggregate Fair Value Notional Amount of Derivatives Derivative, Notional Amount 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 Loss on Derivative Contract Termination Loss on Contract Termination Component of Derivative Gain (Loss) Excluded from the Assessment of Hedge Effectiveness Gain (Loss) from Components Excluded from Assessment of Fair Value Hedge Effectiveness, Net Discontinued Hedge Accounting Due to Instrument No Longer Qualifying as Fair Value Hedge Gain (Loss) from Hedged Firm Commitment Not Qualifying as Fair Value Hedge, Net Fair Value Measurement Inputs and Valuation Techniques [Abstract] Fair Value Inputs, Assets and Liabilities, Quantitative Information Fair Value Inputs, Assets and liabilities, Quantitative Information [Table] Fair Value Inputs, Assets and liabilities, Quantitative Information [Table] Financial Instrument Financial Instrument [Axis] Financial Instrument Financial Instruments [Domain] All Other Corporate Bonds - Private Corporate Debt Securities [Member] Equity Securities - Private Equity Securities [Member] Measurement Input Type Measurement Input Type [Axis] Measurement Input Type Measurement Input Type [Domain] Comparability Adjustment Measurement Input, Comparability Adjustment [Member] Lack of Marketability Measurement Input, Discount for Lack of Marketability [Member] Volatility of Credit Measurement Input, Entity Credit Risk [Member] Valuation Approach and Technique Valuation Approach and Technique [Axis] Valuation Approach and Technique Valuation Approach and Technique [Domain] Market Approach Valuation, Market Approach [Member] Discounted Cash Flow Valuation Technique, Discounted Cash Flow [Member] Liability Class Liability Class [Axis] Fair Value by Liability Class Fair Value by Liability Class [Domain] Embedded Derivative in Modified Coinsurance Arrangement Derivative Financial Instruments, Liabilities [Member] Range Range [Axis] Range Range [Domain] Minimum Minimum [Member] Maximum Maximum [Member] Weighted Average Weighted Average [Member] Fair Value, Hierarchy Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy Fair Value Hierarchy and NAV [Domain] Fair Value, Inputs, Level 3 Fair Value, Inputs, Level 3 [Member] Fair Value Inputs, Assets and Liabilities, Quantitative Information Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] All Other Corporate Bonds - Private Debt Securities, Available-for-sale, Private Debt Securities, Available-for-sale, Private Equity Securities - Private Equity Securities, FV-NI Embedded Derivative in Modified Coinsurance Arrangement Embedded Derivative, Fair Value of Embedded Derivative Liability All Other Corporate Bonds - Private, Measurement Input Debt Securities, Available-for-sale, Measurement Input All Other Corporate Bonds - Private, Market Convention Measurement Input Debt Securities, Available-for-sale, Measurement Input [Extensible List] Equity Securities - Private, Measurement Input Equity Securities, FV-NI, Measurement Input [Extensible List] Embedded Derivative in Modified Coinsurance Arrangement, Measurement Input Embedded Derivative Liability, Measurement Input [Extensible List] Class of Stock Disclosures [Abstract] Class of Treasury Stock Class of Treasury Stock [Table] Share Repurchase Program Share Repurchase Program [Axis] Share Repurchase Program Share Repurchase Program [Domain] Repurchase Program Authorized in May 2018 Repurchase Program Authorized in May 2018 [Member] Repurchase Program Authorized in May 2018 [Member] Repurchase Program Authorized in May 2017 Repurchase Program Authorized in May 2017 [Member] Repurchase Program Authorized in May 2017 [Member] Equity, Class of Treasury Stock Equity, Class of Treasury Stock [Line Items] Authorized Stock Repurchases Stock Repurchase Program, Authorized Amount Remaining Authorized Share Repurchases Stock Repurchase Program, Remaining Authorized Repurchase Amount Number of Treasury Shares Repurchased Treasury Stock, Shares, Acquired Cost of Shares Repurchased Treasury Stock, Value, Acquired, Cost Method Commission Paid on Common Stock Repurchased Shares repurchased cost Commissions Fees and Commission Expenses Accounting Policies [Abstract] Basis of Accounting Basis of Accounting, Policy [Policy Text Block] Insurance [Abstract] Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Table] Nature of Claim Incurred Nature of Claim Incurred [Axis] Nature of Claim Incurred [Axis] Nature of Claim Incurred Nature of Claim Incurred [Domain] [Domain] for Nature of Claim Incurred [Axis] Amount Related to Interest Amount Related to Interest [Member] Amount Related to Interest [Member] Incurred Claims Incurred Claims [Member] Incurred Claims [Member] Foreign Currency Foreign Currency [Member] Foreign Currency [Member] Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] Balance at January 1 Liability for Claims and Claims Adjustment Expense Less Reinsurance Recoverable Reinsurance Recoverables, Incurred but Not Reported Claims Net Balance at January 1 Liability for Unpaid Claims and Claims Adjustment Expense, Net Incurred Related to Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract] Current Year Current Year Claims and Claims Adjustment Expense Prior Years Prior Year Claims and Claims Adjustment Expense Total Incurred Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims Paid Related to Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract] Current Year Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Current Year Prior Years Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years Total Paid Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid Net Balance at September 30 Plus Reinsurance Recoverable Balance at September 30 Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Asset Class Asset Class [Axis] Asset Class Asset Class [Domain] States, Municipalities, and Political Subdivisions US States and Political Subdivisions Debt Securities [Member] Foreign Governments Debt Security, Government, Non-US [Member] Public Utilities Public Utility, Bonds [Member] Mortgage/Asset-backed Securities Asset-backed Securities [Member] All Other Corporate Bonds Redeemable Preferred Stocks Redeemable Preferred Stock [Member] Fixed Maturity Securities Debt Securities [Member] Equity Securities Embedded Derivative in Modified Coinsurance Arrangement Embedded Derivative Financial Instruments [Member] Fair Value of Financial Instruments Measured on Recurring Basis with Unobservable Inputs Reconciliation Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Assets Measured with Unobservable Inputs, Beginning Balance Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset 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) Investment Purchases Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases Investment Sales Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales Investment Level 3 Transfers Into Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3 Investment Level 3 Transfers Out of Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3 Assets Measured with Unobservable Inputs, Ending Balance Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Derivatives Measured with Unobservable Inputs, Beginning Balance Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobservable Inputs Derivative Liability Gain (Loss) Included in Earnings Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Gain (Loss) Included in Earnings Derivative Liability Gain (Loss) Included in OCI Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Gain (Loss) Included in Other Comprehensive Income (Loss) Derivative Purchases Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Purchases Derivative Sales Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Sales Derivative Transfers Into Level 3 Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Transfers into Level 3 Derivative Transfers Out of Level 3 Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Transfers out of Level 3 Derivatives Measured with Unobservable Inputs, Ending Balance Statement of Financial Position [Abstract] Statement Statement [Table] Scenario Scenario [Axis] Scenario, Unspecified Scenario, Unspecified [Domain] Class of Stock Class of Stock [Axis] Class of Stock Class of Stock [Domain] Statement Statement [Line Items] Assets Assets [Abstract] Investments Investments [Abstract] Fixed Maturity Securities - at fair value (amortized cost: $39,913.2; $39,780.5) Debt Securities, Available-for-sale Mortgage Loans Mortgage Loans on Real Estate, Commercial and Consumer, Net 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, Including Reinsurance Premium Paid 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 Deferred Income Tax Deferred Income Tax Assets, Net Other Assets Other Assets Total Assets 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, Net Short-term Debt Debt, Current Long-term Debt Long-term Debt and Capital Lease Obligations Payables for Collateral on Investments Collateralized Financings Other Liabilities Other Liabilities Total Liabilities Liabilities Commitments and Contingent Liabilities - Note 11 Commitments and Contingencies Stockholders' Equity Stockholders' Equity Attributable to Parent [Abstract] Common Stock, $0.10 par; Authorized: 725,000,000 shares; Issued: 305,069,982 and 304,448,032 shares Common Stock, Value, Issued Additional Paid-in Capital Additional Paid in Capital, Common Stock Accumulated Other Comprehensive Income (Loss) Accumulated Other Comprehensive Income (Loss), Net of Tax Retained Earnings Retained Earnings (Accumulated Deficit) Treasury Stock - at cost: 86,347,280 and 81,900,950 shares Treasury Stock, Value Total Stockholders' Equity Stockholders' Equity Attributable to Parent Total Liabilities and Stockholders' Equity Liabilities and Equity 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 Entity Emerging Growth Company Entity Emerging Growth Company Entity Small Business Entity Small Business 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 Notes to Financial Statements [Abstract] Notes to Financial Statements [Abstract] Nature and Amount of Collateral Received From and Posted To Derivative Counterparty Nature and Amount of Collateral Received From and Posted To Derivative Counterparty [Table Text Block] [Table Text Block] for Nature and Amount of Collateral Received From and Posted To Derivative Counterparty [Table] Notional Amounts for Each Category of Derivative Activity Schedule of Derivative Instruments [Table Text Block] Fair Value Hedges Carrying Amount of Hedged Assets and Liabilities and Cumulative Basis Adjustments Fair Value Hedges Carrying Amount of Hedged Assets and Liabilities and Cumulative Basis Adjustments [Table Text Block] [Table Text Block] for Fair Value Hedges Carrying Amount of Hedged Assets and Liabilities and Cumulative Basis Adjustments [Table] 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 Derivative Instruments, Gain (Loss) [Table Text Block] Schedule of Cash Flow Hedges Included in Accumulated Other Comprehensive Income Schedule of Cash Flow Hedges Included in Accumulated Other Comprehensive Income (Loss) [Table Text Block] Gains and Losses on Derivatives Not Designated as Hedging Instruments Derivatives Not Designated as Hedging Instruments [Table Text Block] Transfers of Assets between Level 1 and Level 2 [Abstract] Disclosure - Transfers of Assets between Level 1 and Level 2 [Abstract] Fair Value Measurements Fair Value Measurements, Recurring and Nonrecurring [Table] Period Transferred Period Transferred [Axis] Period Transfer of Financial Asset Between FV Heirarchy Levels Period Transferred Period Transferred [Domain] [Domain] for Period Transfer of Financial Asset Between FV Heirarchy Levels Third Quarter Third Quarter [Member] Third Quarter [Member] First, Second, and Third Quarters First, Second, and Third Quarters [Member] First, Second, and Third Quarters [Member] United States Government and Government Agencies and Authorities US Treasury and Government [Member] Transfers Between Level 1 and Level 2 Transfers Between Level 1 and Level 2 [Line Items] Transfers Between Level 1 and Level 2 [Line Items] Level 1 from Level 2 Fair Value, Assets, Level 2 to Level 1 Transfers, Amount Level 2 from Level 1 Fair Value, Assets, Level 1 to Level 2 Transfers, Amount Distribution of the Maturity Dates for Fixed Maturity Securities [Abstract] Disclosure - Distribution of the Maturity Dates for Fixed Maturity Securities [Abstract] Debt Securities, Available-for-sale Debt Securities, Available-for-sale [Table] Debt Securities, Available-for-sale, Unrealized Gain (Loss), Fair Value Debt Securities, Available-for-sale, Unrealized Gain (Loss), Fair Value [Axis] Debt Securities, Available-for-sale, Unrealized Gain (Loss), Fair Value [Axis] Debt Securities, Available-for-sale, Unrealized Gain (Loss), Fair Value Debt Securities, Available-for-sale, Unrealized Gain (Loss), Fair Value [Domain] [Domain] for Debt Securities, Available-for-sale, Unrealized Gain (Loss), Fair Value [Axis] 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] Debt Securities, Available-for-sale Debt Securities, Available-for-sale [Line Items] Debt Securities, Available-for-sale, Amortized Cost, Fiscal Year Maturity Debt Securities, Available-for-sale, Amortized Cost, Fiscal Year Maturity [Abstract] Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Amortized Cost Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Amortized Cost Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Amortized Cost Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Amortized Cost Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Amortized Cost Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Amortized Cost Debt Securities, Available-for-sale, Allocated and Single Maturity Date, Maturity, after 10 Years, Amortized Cost Debt Securities, Available-for-sale, Allocated and Single Maturity Date, Maturity, after 10 Years, Amortized Cost Available for sale Securities Debt Maturities Amortized Cost Gross Subtotal Available for sale Securities Debt Maturities Amortized Cost Gross Subtotal Available-for-sale Securities, Debt Maturities, Amortized Cost, Gross Subtotal Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Amortized Cost Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Amortized Cost Debt Securities, Available-for-sale, Amortized Cost Debt Securities, Available-for-sale, Amortized Cost 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 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 Available For Sale Securities Debt Maturities Within One Year Unrealized Gain Position Gross Gain 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 Available For Sale Securities Debt Maturities After One Through Five Years Unrealized Gain Position Gross Gain Available For Sale Securities Debt Maturities After Five Through Ten Years Unrealized Gain Position Gross Gain Available For Sale Securities Debt Maturities After Five Through Ten Years Unrealized Gain Position Gross Gain Available For Sale Securities Debt Maturities After Five Through 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 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 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 Available For Sale Securities Debt Maturities Without Single Maturity Date Unrealized Gain Position Gross Gain Available for sale Securities, Debt Maturities Unrealized Gain Position Gross Gain Available for sale Securities, Debt Maturities Unrealized Gain Position Gross Gain Available for sale Securities, Debt Maturities Unrealized Gain Position Gross Gain 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 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 Available For Sale Securities Debt Maturities Within One Year Unrealized Loss Position Gross Loss 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 Position Gross Loss Available For Sale Securities Debt Maturities After One Through Five Years Unrealized Loss Position Gross Loss Available For Sale Securities Debt Maturities After Five Through Ten Years Unrealized Loss Position Gross Loss Available For Sale Securities Debt Maturities After Five Through Ten Years Unrealized Loss Position Gross Loss Available For Sale Securities Debt Maturities After Five Through 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 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 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 Available For Sale Securities Debt Maturities Without Single Maturity Date Unrealized Loss Position Gross Loss Available For Sale Securities Unrealized Loss Position Gross Loss Subtotal Available For Sale Securities Unrealized Loss Position Gross Loss Subtotal Available For Sale Securities Unrealized Loss Position Gross Loss Subtotal Fair Value Maturity Distribution Fair Value Maturity Distribution [Abstract] Fair Value Maturity Distribution [Abstract] Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Fair Value Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Fair Value Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Fair Value Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Fair Value Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Fair Value Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Fair Value Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after 10 Years, Fair Value Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after 10 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 Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Fair Value Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Fair Value Fixed Maturity Securities Federal Home Loan Banks [Abstract] Federal Home Loan Bank Carrying Value of Common Stock, Collateral Posted and Advances [Table] Federal Home Loan Bank Carrying Value of Common Stock, Collateral Posted and Advances [Table] Federal Home Loan Bank Carrying Value of Common Stock, Collateral Posted and Advances [Table] Mortgage Loans as Collateral Collateralized Mortgage Backed Securities [Member] Federal Home Loan Bank Carrying Value of Common Stock, Collateral Posted and Advances Federal Home Loan Bank Carrying Value of Common Stock, Collateral Posted and Advances [Line Items] [Line Items] for Federal Home Loan Bank Carrying Value of Common Stock, Collateral Posted and Advances [Table] Federal Home Loan Bank Stock Federal Home Loan Bank Stock Federal Home Loan Bank (FHLB) Funding Agreements Federal Home Loan Bank, Advances, Branch of FHLB Bank, Amount of Advances Collateral Pledged to Federal Home Loan Bank (FHLB) Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged Liability for Claims and Claims Adjustment Expense Liability for Claims and Claims Adjustment Expense [Table] Insurance Reserve Type Insurance Reserve Type [Axis] Insurance Reserve Type [Axis] Claim Reserve Claim Reserve Total [Domain] Claim Reserve Total [Domain] Claim Reserve Claim Reserve [Member] Claim Reserve [Member] Liability for Claims and Claims Adjustment Expense - Narrative Information Liability for Claims and Claims Adjustment Expense [Line Items] Long-term Care Reserve Increase, Before Tax Long-term Care Reserve Increase, Before Tax Long-term Care Reserve Increase, Before Tax Long-term Care Reserve Increase, After Tax Long-term Care Reserve Increase, After Tax Long-term Care Reserve Increase, After Tax Investments, All Other Investments [Abstract] Low Income Housing Tax Credits Investment Tax Credit Amortization of Low Income Housing Investments Amortization of Low Income Housing Investments Amortization of Low Income Housing Investments Tax Benefits from Low Income Housing Investments Tax Benefits from Low Income Housing Investments Tax Benefits from Low Income Housing Investments Total Policy and Contract Benefits and Reserves for Future Policy and Contract Benefits Liability for Future Policy Benefits Life Reserves for Future Policy and Contract Benefits Life Reserves for Future Policy and Contract Benefits Life Reserves for Future Policy and Contract Benefits Accident and Health Active Life Reserves Accident and Health Active Life Reserves Accident and Health Active Life Reserves Adjustment Related to Unrealized Investment Gains and Losses Unrealized Adjustment to Reserves for Future Policy and Contract Benefits Unrealized Adjustment to Reserves for Future Policy and Contract Benefits Liability for Unpaid Claims and Claim Adjustment Expenses Location of Gains and Losses on Derivative Financial Instruments Designated as Hedging Instruments [Abstract] Disclosure - Location of Gains and Losses on Derivative Financial Instruments Designated as Hedging Instruments [Abstract] Derivative Instruments, Gain (Loss) by Hedging Relationship, by Income Statement Location, by Derivative Instrument Risk Derivative Instruments, Gain (Loss) [Table] Derivative Instruments, Gain (Loss) Derivative Instruments, Gain (Loss) [Line Items] Gain (Loss) Recognized in OCI on Derivatives (Effective Portion) Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax Fair Values of Financial Instruments Additional Information [Abstract] Disclosure - Fair Values of Financial Instruments - Additional Information [Abstract] Heirarchy Level Combination Heirarchy Level Combination [Axis] Heirarchy Level Combination [Axis] Heirarchy Level Combination Heirarchy Level Combination [Domain] [Domain] for Heirarchy Level Combination [Axis] Fair Value Inputs Other Than Level 1 Fair Value Inputs Other Than Level 1 [Member] Fair Value Inputs Other Than Level 1 [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, Inputs, Level 1 Fair Value, Inputs, Level 1 [Member] Fair Value, Inputs, Level 2 Fair Value, Inputs, Level 2 [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] 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 Ceded Policy Loans Policy Loans Ceded to Reinsurers Loans ceded to reinsurers. These loans use insurance policy funds such as cash surrender values as collateral. Gain (Loss) on Embedded Derivative Embedded Derivative, Gain (Loss) on Embedded Derivative, Net Stockholders' Equity and Earnings Per Common Share [Abstract] Stockholders' Equity and Earnings Per Common Share [Abstract] Schedule of Basic and Diluted Earnings Per Share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Treasury Stock Transactions Class of Treasury Stock [Table Text Block] Reconciliation of Revenue from Segments to Consolidated Reconciliation of Revenue from Segments to Consolidated [Table] Segment Reporting, Revenue Reconciling Item Segment Reporting, Revenue Reconciling Item [Line Items] Total Revenue Revenues Net Realized Investment Gain Adjusted Operating Revenue Adjusted Operating Revenue Adjusted Operating Revenue Income (Loss) Before Income Tax Expense (Benefit) Net Realized Investment Gain Loss Related to Guaranty Fund Assessment Loss Related to Guaranty Fund Assessment Loss Related to Guaranty Fund Assessment Long-term Care Reserve Increase Adjusted Operating Income (Loss) Operating Income (Loss) Notional Amounts for Each Category of Derivative Activity [Abstract] Disclosure - Notional Amounts for Each Category of Derivative Activity [Abstract] Credit Default Swaps Forwards Forward Contracts [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 SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Abstract] Mortgage Loans Sorted by Applicable Credit Quality Indicator Schedule of Financing Receivable, Recorded Investment, Credit Quality Indicator [Table] 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] 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] Financing Receivable, Recorded Investment Financing Receivable, Recorded Investment [Line Items] Transfers and Servicing [Abstract] Transfer of Certain Financial Assets Accounted for as Secured Borrowings Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Table] All Other Corporate Bonds Corporate Bond Securities [Member] Repurchase Agreements and Similar Transactions, Maturity Periods Repurchase Agreements and Similar Transactions, Maturity Periods [Axis] Repurchase Agreements and Similar Transactions, Maturity Periods Repurchase Agreements and Similar Transactions, Maturity Periods [Domain] Overnight and Continuous Maturity Overnight [Member] Transfer of Certain Financial Assets Accounted for as Secured Borrowings Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items] Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred Securities Loaned and Securities Sold under Agreement to Repurchase, Gross Including Not Subject to Master Netting Arrangement Securities Loaned and Securities Sold under Agreement to Repurchase, Gross Including Not Subject to Master Netting Arrangement Secured Borrowings, Gross, Difference, Amount Secured Borrowings, Gross, Difference, Amount Statement of Comprehensive Income [Abstract] Other Comprehensive Income (Loss) Other Comprehensive Income (Loss), Net of Tax [Abstract] Change in Net Unrealized Gain (Loss) on Securities Before Adjustment (net of tax expense (benefit) of $(80.6); $39.2; $(525.0); $334.7) Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, after 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 $(69.8); $(31.8); $276.1; $(261.7)) 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 gain (loss) on securities during the period net of the effects of contracts assumed and ceded, net of tax. Change in Net Gain on Hedges (net of tax benefit of $4.4; $7.4; $8.3; $19.7) Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax Change in Foreign Currency Translation Adjustment (net of tax benefit of $-; $-; $0.3; $-) 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 $1.3; $1.5; $4.0; $4.3) Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax Total Other Comprehensive Income (Loss) Other Comprehensive Income (Loss), Net of Tax Comprehensive Income (Loss) Comprehensive Income (Loss), Net of Tax, Attributable to Parent Net Investment Income, Insurance Entity [Abstract] Net Investment Income Investment Income [Table] Investment Type Investment Type [Axis] Investment Type Categorization Investments [Domain] Derivatives Derivative [Member] Mortgage Loans Mortgage Receivable [Member] Policy Loans Policy Loans [Member] Private Equity Partnerships Partnership Interest [Member] Other Long-term Investments Other Long-term Investments [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 Net Investment Income 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, Below-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] Private Equity Partnerships 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] Bonds Bonds [Member] Financing Receivable, Troubled Debt Restructuring Financing Receivable Portfolio Segment [Axis] Financing Receivable Portfolio Segment Financing Receivable Portfolio Segment [Domain] Commercial Real Estate Portfolio Segment Commercial Real Estate Portfolio Segment [Member] Class of Financing Receivable Class of Financing Receivable, Type [Axis] Class of Financing Receivable Class of Financing Receivable, Type [Domain] Derivative Instrument by Balance Sheet Location Balance Sheet Location [Axis] Balance Sheet Location Balance Sheet Location [Domain] Off Balance Sheet Amount Off Balance Sheet Amount [Member] Off Balance Sheet Amount [Member] Schedule of Investments Schedule of Investments [Line Items] Number of Fixed Maturity Securities 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 Commitments to Investment Partnerships Unfunded commitment to fund tax credit partnership investments Unfunded Commitments and Standby Letters of Credit 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 Financing Receivable, Modifications, Number of Contracts Financing Receivable, Modifications, Number of Contracts Financing Receivable, Modifications, Pre-Modification Recorded Investment Financing Receivable, Modifications, Pre-Modification Recorded Investment Financing Receivable, Allowance for Credit Losses Financing Receivable, Allowance for Credit Losses Number of Financing Receivables on Nonaccrual Status Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing 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 Loans and Leases Receivable, Allowance Loans and Leases Receivable, Allowance Provision for Loan and Lease Losses Provision for Loan and Lease Losses Impaired Financing Receivable, Recorded Investment Impaired Financing Receivable, with Related Allowance, Recorded Investment Impaired Financing Receivable, Average Recorded Investment Impaired Financing Receivable, with Related Allowance, Average Recorded Investment Impaired Financing Receivable, Interest Income, 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 Fair Value of Securities Loaned or Securities Purchased Under Repurchase Agreements to 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 Net Securities Borrowed Reported in Balance Sheet Securities Borrowed Cash Collateral for Borrowed Securities Cash Collateral for Borrowed Securities Securities Received as Collateral Securities Received as Collateral Outstanding Repurchase Agreements Securities Sold under Agreements to Repurchase Investments, Debt and Equity Securities [Abstract] Investments Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Fixed Maturity Securities, Amortized Cost 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 Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net [Abstract] Gain (Loss) on Derivatives Accumulated Other Comprehensive Income (Loss) Accumulated Other Comprehensive Income (Loss) [Table] Foreign Currency Translation Adjustment Accumulated Foreign Currency Adjustment Attributable to Parent [Member] Accumulated Other Comprehensive Income (Loss) Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income (Loss), Net of Tax AOCI Attributable to Parent, Net of Tax [Roll Forward] Balance at Beginning of Period Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Recognition and Measurement of Financial Assets and Financial Liabilities, Reclassification from AOCI to Retained Earnings Recognition and Measurement of Financial Assets and Financial Liabilities, Reclassification from AOCI to Retained Earnings The amount Reclassified from AOCI to Retained Earnings due to the adoption of ASU 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities. Other Comprehensive Income (Loss) Before Reclassifications, Net of Tax Other Comprehensive Income (Loss), before Reclassifications, Net of Tax Reclassification from Accumulated Other Comprehensive Income or Loss Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax Balance at End of Period Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure Commitments and Contingencies Disclosure [Text Block] Offsetting [Abstract] Offsetting Assets and Liabilities Offsetting Liabilities [Table] Transaction Type Transaction Type [Axis] Transaction Transaction [Domain] Over the Counter Over the Counter [Member] Offsetting Assets and Liabilities Offsetting Liabilities [Line Items] Offsetting Assets Offsetting Assets [Abstract] Offsetting Assets [Abstract] Offsetting Derivative Assets Offsetting Derivative Assets [Abstract] Gross Derivative Assets Derivative Asset, Fair Value, Gross Asset Derivative Liabilities Offsetting Derivative Assets in Balance Sheet Derivative Asset, Fair Value, Gross Liability Net Derivative Assets Reported in Balance Sheet Derivative Asset Securities Received as Collateral on Derivative Assets Derivative, Collateral, Obligation to Return Securities Cash Collateral from Counterparties Derivative, Collateral, Obligation to Return Cash Derivative Assets Net of Collateral Derivative Asset, Fair Value, Amount Offset Against Collateral Offsetting Securities Borrowed Offsetting Securities Borrowed [Abstract] Gross Securities Borrowed Securities Borrowed, Gross Liabilities Offsetting Securities Borrowed in Balance Sheet Securities Borrowed, Liability Securities Received as Collateral on Securities Borrowed Securities Borrowed, Collateral, Obligation to Return Securities Cash Received as Collateral on Securities Borrowed Securities Borrowed, Collateral, Obligation to Return Cash Securities Borrowed Net of Collateral Securities Borrowed, Amount Offset Against Collateral Offsetting of Derivative Assets and Securities Borrowed Offsetting Derivative Asset, Securities Purchased under Agreements to Resell, Securities Borrowed [Abstract] Gross Financial Assets Derivative Asset, Securities Purchased under Agreements to Resell, Securities Borrowed, Gross Financial Liabilities Offsetting Financial Assets in Balance Sheet Derivative Asset, Securities Purchased under Agreements to Resell, Securities Borrowed, Liability Net Financial Assets Reported in Balance Sheet Derivative Asset, Securities Purchased under Agreements to Resell, Securities Borrowed Securities Received as Collateral on Financial Assets Derivative Asset, Securities Purchased under Agreements to Resell, Securities Borrowed, Collateral, Obligation to Return Securities Cash Received as Collateral on Financial Assets Derivative Asset, Securities Purchased under Agreements to Resell, Securities Borrowed, Collateral, Obligation to Return Cash Financial Assets Net of 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 Liability Derivative Liability, Fair Value, Gross Liability Derivative Assets Offsetting Derivative Liabilities in Balance Sheet Derivative Liability, Fair Value, Gross Asset Net Derivative Liabilities Reported in Balance Sheet Derivative Liability Securities Given as Collateral on Derivative Liabilities Derivative, Collateral, Right to Reclaim Securities Cash Collateral to Counterparties Derivative, Collateral, Right to Reclaim Cash Derivative Liabilities Net of Collateral Derivative Liability, Fair Value, Amount Offset Against Collateral Offsetting Securities Loaned Offsetting Securities Loaned [Abstract] Gross Securities Loaned Securities Loaned, Gross Assets Offsetting Securities Loaned in Balance Sheet Securities Loaned, Asset Net Securities Loaned Reported in Balance Sheet Securities Loaned Securities Given as Collateral on Securities Loaned Securities Loaned, Collateral, Right to Reclaim Securities Cash Given as Collateral on Securities Loaned Securities Loaned, Collateral, Right to Reclaim Cash Securities Loaned Net of Collateral Securities Loaned, Amount Offset Against Collateral Derivative Liabilities and Securities Lending Liabilities Offsetting Derivative Liability, Securities Sold under Agreements to Repurchase, Securities Loaned [Abstract] Gross Financial Liability Derivative Liability, Securities Sold under Agreements to Repurchase, Securities Loaned, Gross Financial Assets Offsetting Financial Liabilities in Balance Sheet Derivative Liability, Securities Sold under Agreements to Repurchase, Securities Loaned, Asset Net Financial Liabilities Reported in Balance Sheet Derivative Liability, Securities Sold under Agreements to Repurchase, Securities Loaned Securities Given as Collateral on Financial Liabilities Derivative Liability, Securities Sold under Agreements to Repurchase, Securities Loaned, Collateral, Right to Reclaim Securities Cash Given as Collateral on Financial Liabilities Derivative Liability, Securities Sold under Agreements to Repurchase, Securities Loaned, Collateral, Right to Reclaim Cash Financial Liabilities Net of Collateral Derivative Liability, Securities Sold under Agreements to Repurchase, Securities Loaned, Amount Offset Against Collateral Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract] Fair Value Measurements by Input Level Foreign Exchange Contracts Currency Swap [Member] Measurement Frequency Measurement Frequency [Axis] Fair Value, Measurement Frequency Fair Value, Measurement Frequency [Domain] Fair Value, Measurements, Recurring Fair Value, Measurements, Recurring [Member] Private Equity Partnerships Private Equity Funds [Member] Fair Value Measured at Net Asset Value Per Share Fair Value Measured at Net Asset Value Per Share [Member] Assets, Fair Value Disclosure Assets, Fair Value Disclosure [Abstract] Fixed Maturity Securities Debt Securities, Available-for-sale [Abstract] Derivative Assets Equity Securities Alternative Investments Alternative Investment Assets, Fair Value Disclosure Assets, Fair Value Disclosure Derivative Liabilities Liabilities, Fair Value Disclosure Financial and Nonfinancial Liabilities, Fair Value Disclosure Statement of Stockholders' Equity [Abstract] Common Stock Common Stock [Member] Additional Paid-in Capital Additional Paid-in Capital [Member] Accumulated Other Comprehensive Income (Loss) AOCI Attributable to Parent [Member] Retained Earnings Retained Earnings [Member] Treasury Stock Treasury Stock [Member] Increase (Decrease) in Stockholders' Equity Increase (Decrease) in Stockholders' Equity [Roll Forward] 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: $0.72; $0.63) Dividends, Cash Purchases of Treasury Stock Balance at End of Period Basis of Presentation Basis of Accounting [Text Block] Corporate and Other Corporate and Other [Member] Other Income Other Income Adjusted Operating Revenue Adjusted Operating Income (Loss) 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] Retirement Plan Type Retirement Plan Type [Axis] Retirement Plan Type Retirement Plan Type [Domain] Pension Plan Pension Plan [Member] OPEB Plan Other Postretirement Benefits Plan [Member] Retirement Plan Sponsor Location Retirement Plan Sponsor Location [Axis] Retirement Plan Sponsor Location Retirement Plan Sponsor Location [Domain] Domestic Plan Domestic Plan [Member] Foreign Plan Foreign Plan [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 (Loss) on Plan Assets Amortization of Net Actuarial Loss Defined Benefit Plan, Amortization of Gain (Loss) Amortization of Prior Service Credit Defined Benefit Plan, Amortization of Prior Service Cost (Credit) Net Periodic Benefit Cost Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Fair Value Disclosures [Abstract] Fair Value, Investments, Entities that Calculate Net Asset Value Per Share Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Table] Private Equity Fund Type Private Equity Fund Type [Axis] Private Equity Fund Type [Axis] Private Equity Fund Type Private Equity Fund Type [Domain] [Domain] for Private Equity Fund Type [Axis] Private Credit Private Credit [Member] Private Credit limited partnerships employ various investment strategies, generally providing direct lending or other forms of debt financing including first-lien, second-lien, mezzanine, and subordinated loans. [Member] Private Equity Limited Partnership Private Equity Limited Partnership [Member] Private Equity Limited Partnership [Member] Real Assets Real Assets [Member] Real Assets limited partnerships employ various strategies, which include investing in the equity and/or debt financing of physical assets, including infrastructure (energy, power, water/wastewater, communications), transportation (including airports, ports, toll roads, aircraft, railcars) and real estate in North America, Europe, South America, and Asia.[Member] Redemption Term Redemption Term [Axis] Disclosure of information about partnership equity securities with redemption features. [Axis] Redemption Term Redemption Term [Domain] [Domain] for Disclosure of information about partnership equity securities with redemption features. [Axis] Not Redeemable Not Redeemable [Member] These partnerships do not allow for redemptions [Member] Quarterly after 2 year lock with 90 days notice Quarterly after 2 year lock with 90 days notice [Member] Initial 2 year lock on each new investment. Redemptions are allowed quarterly after 2 year lock with 90 days notice. [Member] Quarterly Quarterly [Member] Quarterly redemption term with 90 day notice [Member] Fair Value, Investments, Entities that Calculate Net Asset Value Per Share Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items] Alternative Investments, Unfunded Commitments Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments Accounting Changes and Error Corrections [Abstract] New Accounting Pronouncements or Change in Accounting Principle New Accounting Pronouncements or Change in Accounting Principle [Table] Restatement Restatement [Axis] Restatement Restatement [Domain] Effect of Change Restatement Adjustment [Member] Historical Accounting Method Previously Reported [Member] Adjustments for New Accounting Pronouncements Adjustments for New Accounting Pronouncements [Axis] Type of Adoption Type of Adoption [Domain] Accounting Standards Update 2016-15 Accounting Standards Update 2016-15 [Member] Accounting Standards Update 2017-07 Accounting Standards Update 2017-07 [Member] Accounting Standards Update 2016-01 Accounting Standards Update 2016-01 [Member] New Accounting Pronouncements or Change in Accounting Principle New Accounting Pronouncements or Change in Accounting Principle [Line Items] Other, Net Compensation Expense Labor and Related Expense Other Expenses Retained Earnings 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] Gross Gains on Sales Available-for-sale Securities, Gross Realized Gains Gross Losses on Sales Available-for-sale Securities, Gross Realized Losses Mortgage Loans and Other Invested Assets Other Investments [Abstract] 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 Gross Losses on Sales Other Investments Gross Realized Losses Other Investments Gross Realized Losses Gain on Embedded Derivative Foreign Currency Transactions Foreign Currency Transaction Gain (Loss), before Tax Net Realized Investment Gain Income Statement [Abstract] Revenue Revenues [Abstract] Realized Investment Gain (Loss) Realized Investment Gains (Losses) [Abstract] Net Realized Investment Gain, Excluding Other-Than-Temporary Impairment Loss on Fixed Maturity Securities Debt and Equity Securities, Realized Gain (Loss), Excluding Other-than-temporary Impairment 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 Deferral of Acquisition Costs Increase (Decrease) in Deferred Policy Acquisition Costs Amortization of Deferred Acquisition Costs Deferred Policy Acquisition Costs, Amortization Expense Total Benefits and Expenses Benefits, Losses and Expenses Income Tax (Benefit) Income Tax Expense (Benefit), Continuing Operations [Abstract] Current Current Income Tax Expense (Benefit) Deferred Deferred Income Tax Expense (Benefit) Total Income Tax Expense (Benefit) Net Income (Loss) Net Income (Loss) Per Common Share Earnings Per Share [Abstract] Basic Earnings Per Share, Basic Assuming Dilution Earnings Per Share, Diluted 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] Assets by Segment Reconciliation of Assets from Segment to Consolidated [Table Text Block] Reconciliation of Total Revenue and Income (Loss) before Income Tax by Segment to Adjusted Operating Revenue and Adjusted Operating Income Reconciliation of Revenue from Segments to Consolidated [Table Text Block] Debt and Other Disclosures [Abstract] Debt and Other Disclosures [Abstract] Debt Disclosure Debt Disclosure [Text Block] Income Tax Disclosure Income Tax Disclosure [Text Block] 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] Derivative Instrument by Balance Sheet Location Other Liabilities Other Liabilities [Member] Asset Derivatives Fair Value Liability Derivatives Fair Value Derivative Instruments and Hedging Activities Disclosure [Abstract] Derivative Instruments and Hedging Activities Disclosures Derivative Instruments and Hedging Activities Disclosures [Table] Fixed Maturity Securities Available-for-sale Securities [Member] Long-term Debt Long-term Debt [Member] Derivative Instruments and Hedging Activities Disclosures Derivative Instruments and Hedging Activities Disclosures [Line Items] Hedged Asset, Fair Value Hedge Hedged Asset, Fair Value Hedge Hedged Asset, Fair Value Hedge, Cumulative Increase (Decrease) Hedged Asset, Fair Value Hedge, Cumulative Increase (Decrease) Hedged Liability, Fair Value Hedge Hedged Liability, Fair Value Hedge Hedged Liability, Fair Value Hedge, Cumulative Increase (Decrease) Hedged Liability, Fair Value Hedge, Cumulative Increase (Decrease) Fair Values of Financial Instruments Fair Value Disclosures [Text Block] Segment Information Segment Reporting Disclosure [Text Block] Assets Distribution by External Credit Rating for Fixed Maturity Securities [Abstract] Distribution by External Credit Rating for Fixed Maturity Securities [Abstract] Schedule of Available-for-sale Securities Schedule of Available-for-sale Securities [Table] Accumulated Gross Unrealized Gain on Securities Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax Accumulated Gross Unrealized Loss on Securities Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax Percent of Fixed Maturity Securities in Unrealized Loss Position 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. 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 (Loss) Reclassification out of Accumulated Other Comprehensive Income [Table Text Block] Change in Net Unrealized Gain on Securities Before Adjustment, Tax Expense (Benefit) Other Comprehensive Income (Loss), Securities, Available-for-sale, 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 Hedges, Tax Benefit Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Tax Change in Foreign Currency Translation Adjustment, Tax Benefit Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax Change in Unrecognized Pension and Postretirement Benefit Costs, Tax Expense Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax Amortized Cost and Fair Values of Securities by Security Type Debt Securities, Available-for-sale [Table Text Block] Length of Time Fixed Maturity Securities had been in a Gross Unrealized Loss Position Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Table Text Block] Distribution of the Maturity Dates for Fixed Maturity Securities Investments Classified by Contractual Maturity Date [Table Text Block] Available for Sale Debt Securities by External Credit Rating Available for Sale Debt Securities by External Credit Rating [Table Text Block] Available for Sale Debt Securities by External Credit Rating [Table Text Block] Low Income Housing Tax Credits Activity in Affordable Housing Program Obligation [Table Text Block] Mortgage Loans by Property Type and Geographic Region Mortgage Loans by Property Type and Geographic Regioin [Table Text Block] Mortgage Loans by Property Type and Geographic Region [Table Text Block] Mortgage Loans by Credit Quality Indicators Financing Receivable Credit Quality Indicators [Table Text Block] Remaining Contractual Maturity of Securities Lending Agreements Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Table Text Block] Federal Home Loan Bank Common Stock Carrying Amounts, Amounts Posted, and Advances Received Federal Home Loan Bank Common Stock Carrying Amounts, Amounts Posted, and Advances Received [Table Text Block] Federal Home Loan Bank Common Stock Carrying Amounts, Amounts Posted, and Advances Received [Table Text Block] Schedule of Financial Instrument and Derivative Offsetting Schedule of Financial Instrument and Derivative Offsetting [Table Text Block] Schedule of Financial Instrument and Derivative Offsetting [Table Text Block] Net Investment Income Investment Income [Table Text Block] Realized Investment Gains and Losses Reported in Consolidated Statements of Income Gain (Loss) on Securities [Table Text Block] Debt - Additional Information [Abstract] Debt - Additional Information [Abstract] Debt Narrative Detail Information Debt Narrative Detail Information [Table] Debt Narrative Detail Information Long-term Debt, Type Long-term Debt, Type [Axis] Long-term Debt, Type Long-term Debt, Type [Domain] Senior Notes Senior Notes [Member] Junior Subordinated Notes Junior Subordinated Debt [Member] Debt Instrument Debt Instrument [Axis] Debt Instrument, Name Debt Instrument, Name [Domain] Notes Payable due 2018 Notes Payable due 2018 [Member] Notes Payable due 2018 Notes Payable Due 2058 Notes Payable Due 2058 [Member] Notes Payable Due 2058 [Member] Legal Entity Legal Entity [Axis] Entity Entity [Domain] Northwind Holdings LLC Northwind Holdings LLC [Member] Northwind Holdings LLC [Member] Extinguishment of Debt Extinguishment of Debt [Axis] Extinguishment of Debt, Type Extinguishment of Debt, Type [Domain] 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]