Accounting Policies [Abstract] Basis of Accounting Basis of Accounting, Policy [Policy Text Block] Defined Benefit Plan [Abstract] Schedule of Net Periodic Benefit Costs Schedule of Net Benefit Costs [Table Text Block] Statement of Cash Flows [Abstract] 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 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) Loss 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 Available-for-sale Securities 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 Available-for-sale Securities Purchases of Other Investments Payments to Acquire Other Investments Net Sales (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 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] 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 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] Segment Information Segment Reporting Disclosure [Text Block] 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] Equity Components Equity Components [Axis] Equity Component Equity Component [Domain] Net Unrealized Gain on Securities Accumulated Net Investment Gain (Loss) Attributable to Parent [Member] 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] Fixed Maturity Securities Debt Securities [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 Including Reinsurance Premium Paid [Member] Income Tax 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), Debt Securities, Available-for-sale, Adjustment, after Tax Change in Net Unrealized Gain on Securities Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, after Tax End of Period Balance 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 March 31 Plus Reinsurance Recoverable Balance at March 31 Statement of Stockholders' Equity [Abstract] Statement Statement [Table] Retained Earnings Retained Earnings [Member] Statement Statement [Line Items] Dividends to Stockholders, per common share Common Stock, Dividends, Per Share, Cash Paid 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 International Unum International [Member] Unum International [Member] Colonial Life Colonial Life [Member] Colonial Life [Member] Closed Block Closed Block [Member] Closed Block [Member] Corporate and Other Corporate and Other [Member] Segment Reporting Information Segment Reporting Information [Line Items] Premium Income Premiums Earned, Net Net Investment Income Net Investment Income Other Income Other Income Adjusted Operating Revenue Adjusted Operating Revenue Adjusted Operating Revenue Adjusted Operating Income (Loss) Operating Income (Loss) Statement of Comprehensive Income [Abstract] 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 $326.8; $(274.9)) Change in Adjustment to Deferred Acquisition Costs and Reserves for Future Policy and Contract Benefits, Net of Reinsurance (net of tax expense (benefit) of $(245.5); $212.1) 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 $5.8; $2.3) Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax Change in Foreign Currency Translation Adjustment (net of tax expense 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 $0.7; $0.7) 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 Comprehensive Income (Loss), Net of Tax, Attributable to Parent 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 Before Income Tax to Adjusted Operating Revenue and Adjusted Operating Income Reconciliation of Revenue from Segments to Consolidated [Table Text Block] Allowance for Mortgage Loans [Abstract] Allowance for Mortgage Loans [Abstract] Schedule of Financing Receivable, Allowance for Credit Losses Schedule of Financing Receivable, Allowance for Credit Losses [Table] Class of Financing Receivable Class of Financing Receivable, Type [Axis] Class of Financing Receivable Class of Financing Receivable, Type [Domain] Commercial Real Estate Portfolio Segment Commercial Real Estate Portfolio Segment [Member] Financing Receivable, Allowance for Credit Losses Financing Receivable, Allowance for Credit Losses [Line Items] Loans and Leases Receivable, Allowance Loans and Leases Receivable, Allowance Provision for Loan and Lease Losses Provision for Loan and Lease Losses Allowance for Loan and Lease Losses, Write-offs Allowance for Loan and Lease Losses, Write-offs 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] Financial Instrument Financial Instrument [Axis] Financial Instruments Financial Instruments [Domain] 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 Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net [Abstract] Derivative Instruments, Gain (Loss) Derivative Instruments, Gain (Loss) [Table] Income Statement Location Income Statement Location [Axis] Income Statement Location Income Statement Location [Domain] Net Realized Investment Gain (Loss) Gain (Loss) on Investments [Member] Hedging Designation Hedging Designation [Axis] Hedging Designation Hedging Designation [Domain] Not Designated as Hedging Instrument Not Designated as Hedging Instrument [Member] Derivative Instrument Derivative Instrument [Axis] Derivative Contract Derivative Contract [Domain] Credit Default Swaps Credit Default Swap [Member] Foreign Exchange Contracts Foreign Exchange Contract [Member] Embedded Derivative in Modified Coinsurance Arrangement Embedded Derivative Financial Instruments [Member] Derivative Instruments, Gain (Loss) Derivative Instruments, Gain (Loss) [Line Items] Gain (Loss) on Derivatives Derivative, Gain (Loss) on Derivative, Net Investments, Debt and Equity Securities [Abstract] Investments Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Schedule of Available-for-sale Securities [Table] United States Government and Government Agencies and Authorities US Treasury and Government [Member] 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 Other Corporate Bonds [Member] Redeemable Preferred Stocks Redeemable Preferred Stock [Member] Schedule of Available-for-sale Securities Debt Securities, Available-for-sale [Line Items] Amortized Cost of Fixed Maturity Securities Debt Securities, Available-for-sale, Amortized Cost 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 Fixed Maturity Securities Debt Securities, Available-for-sale Debt and Other Disclosures [Abstract] Debt and Other Disclosures [Abstract] Debt Disclosure Debt Disclosure [Text Block] Subsequent Events Subsequent Events [Text Block] 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] Equity Securities Equity Securities [Member] Partnership Interest 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 Leases [Abstract] Lessee, Operating Lease, Liability, Payments, Due Next Twelve Months Lessee, Operating Lease, Liability, Payments, Due Next Twelve Months Lessee, Operating Lease, Liability, Payments, Due Year Two Lessee, Operating Lease, Liability, Payments, Due Year Two Lessee, Operating Lease, Liability, Payments, Due Year Three Lessee, Operating Lease, Liability, Payments, Due Year Three Lessee, Operating Lease, Liability, Payments, Due Year Four Lessee, Operating Lease, Liability, Payments, Due Year Four Lessee, Operating Lease, Liability, Payments, Due Year Five Lessee, Operating Lease, Liability, Payments, Due Year Five Lessee, Operating Lease, Liability, Payments, Due after Year Five Lessee, Operating Lease, Liability, Payments, Due after Year Five Lessee, Operating Lease, Liability, Payments, Due Lessee, Operating Lease, Liability, Payments, Due Lessee, Operating Lease, Liability, Undiscounted Excess Amount Lessee, Operating Lease, Liability, Undiscounted Excess Amount Operating Lease, Liability Operating Lease, 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 Fair Values of Financial Instruments Additional Information [Abstract] Disclosure - Fair Values of Financial Instruments - Additional Information [Abstract] Fair Value Measurements Measured on a Recurring and Nonrecurring Basis Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value, Hierarchy Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy Fair Value Hierarchy and NAV [Domain] Fair Value, Inputs, Level 1 Fair Value, Inputs, Level 1 [Member] Fair Value, Inputs, Level 2 Fair Value, Inputs, Level 2 [Member] 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, Assets and Liabilities Components Fair Value, Assets and Liabilities Components [Axis] Fair Value, Assets and Liabilities Components Axis Fair Value, Assets and Liabilities Components 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 Gain (Loss) on Embedded Derivative Embedded Derivative, Gain (Loss) on Embedded Derivative, Net Fair Value of Financial Instruments Additional Information Fair Value of Financial Instruments Additional Information [Abstract] Fair Value of Financial Instruments Additional Information [Abstract] 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. Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract] Schedule of Accumulated Other Comprehensive Income (Loss) Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Schedule of Components of Unrealized Gain 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] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract] Interest Rate Swaps Interest Rate Swap [Member] Currency Swap Currency Swap [Member] All Other Corporate Bonds Corporate Debt Securities [Member] Private Equity Funds Private Equity Funds [Member] Measurement Frequency Measurement Frequency [Axis] Fair Value, Measurement Frequency Fair Value, Measurement Frequency [Domain] Fair Value, Measurements, Recurring Fair Value, Measurements, Recurring [Member] Fair Value, Inputs, Level 3 Fair Value, Inputs, Level 3 [Member] Fair Value Measured at Net Asset Value Per Share Fair Value Measured at Net Asset Value Per Share [Member] Derivative Asset Derivative Asset Equity Securities Equity Securities, FV-NI Alternative Investment Alternative Investment Other Long-term Investments Other Long-term Investments Assets, Fair Value Disclosure Assets, Fair Value Disclosure Derivative Liability Derivative Liability Total Financial Liabilities, Fair Value Financial and Nonfinancial Liabilities, Fair Value Disclosure 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), Cash Flow Hedge, Gain (Loss), after Reclassification, 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 Operating Lease, Cost Operating Lease, Cost Sublease Income Sublease Income Lease, Cost Lease, Cost Finance Lease, Principal Payments Finance Lease, Principal Payments Operating Lease, Weighted Average Remaining Lease Term Operating Lease, Weighted Average Remaining Lease Term Operating Lease, Weighted Average Discount Rate, Percent Operating Lease, Weighted Average Discount Rate, Percent 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 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] 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 Liability for Unpaid Claims and Claims Adjustment Expense Schedule of Liability for Unpaid Claims and Claims Adjustment Expense [Table Text Block] Reconciliation of Policy and Contract Benefits and Reserves for Future Policy and Contract Benefits to Balance Sheet Amounts Reconciliation of Policy and Contract Benefits and Reserves for Future Policy and Contract Benefits to Balance Sheet Amounts [Table Text Block] [Table Text Block] for Reconciliation of Policy and Contract Benefits and Reserves for Future Policy and Contract Benefits to Balance Sheet Amounts [Table] Reclassification out of Accumulated Other Comprehensive Income Reclassification out of Accumulated Other Comprehensive Income [Table] Reclassification out of Accumulated Other Comprehensive Income Reclassification out of Accumulated Other Comprehensive Income [Axis] Reclassification out of Accumulated Other Comprehensive Income 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] Accumulated Net Gain (Loss) from Designated or Qualifying Hedges Accumulated Net Gain (Loss) from Designated or Qualifying Hedges [Member] Accumulated Net Gain (Loss) from Designated or Qualifying Hedges [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] Reclassification Adjustment out of Accumulated Other Comprehensive Income Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] Net Realized Investment Gain (Loss), Excluding Other-Than-Temporary Impairment Loss on Fixed Maturity Securities Gain (Loss) on Investments, Excluding Other than Temporary Impairments Other-Than-Temporary Impairment Loss Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, 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 Income Tax Expense (Benefit) Accounting Changes and Error Corrections [Abstract] Accounting Updates Adopted in 2018 Schedule of New Accounting Pronouncements and Changes in Accounting Principles [Table Text Block] Restatement Restatement [Axis] Restatement Restatement [Domain] Restatement Adjustment Restatement Adjustment [Member] Common Stock Common Stock [Member] Additional Paid-in Capital Additional Paid-in Capital [Member] Accumulated Other Comprehensive Income (Loss) AOCI Attributable to Parent [Member] Treasury Stock Treasury Stock [Member] Increase (Decrease) in Stockholders' Equity Increase (Decrease) in Stockholders' Equity [Roll Forward] Balance at Beginning of Period Stockholders' Equity Attributable to Parent Stock Issued During Period, Value, New Issues Stock Issued During Period, Value, New Issues Cumulative Effect of New Accounting Principle in Period of Adoption Cumulative Effect of New Accounting Principle in Period of Adoption Total Other Comprehensive Income (Loss) Dividends, Cash Dividends, Cash Treasury Stock, Value, Acquired, Cost Method Treasury Stock, Value, Acquired, Cost Method Balance at End of Period Notional Amounts for Each Category of Derivative Activity [Abstract] Disclosure - Notional Amounts for Each Category of Derivative Activity [Abstract] Derivative Derivative [Table] Interest Rate Derivatives Contract Type Interest Rate Derivatives Contract Type [Axis] Interest Rate Derivatives Contract Type [Axis] Interest Rate Derivatives Contract Type Interest Rate Derivatives Contract Type [Domain] [Domain] for Interest Rate Derivatives Contract Type [Axis] Receive Variable/Pay Fixed Derivative Financial Instruments Receive Variable Pay Fixed [Member] Derivative Financial Instruments, Receive Variable Pay Fixed [Member] Receive Fixed/Pay Fixed Derivative Financial Instruments Receive Fixed Pay Fixed [Member] Derivative Financial Instruments, Receive Fixed Pay Fixed [Member] Receive Fixed/Pay Variable Derivative Financial Instruments Receive Fixed Pay Variable [Member] Derivative Financial Instruments, Receive Fixed Pay Variable [Member] Credit Risk Contract Credit Risk Contract [Member] Forwards Forward Contracts [Member] Credit Derivatives Contract Type Credit Derivatives Contract Type [Axis] Credit Derivatives Contract Type Credit Derivatives Contract Type [Domain] Derivative Derivative [Line Items] Balance at beginning of period Derivative, Notional Amount Additions Notional Amount Of Derivatives Additions Notional Amount Of Derivatives, Additions Terminations Notional Amount Of Derivatives Terminations Notional Amount Of Derivatives, Terminations Foreign Currency Notional Amount Of Derivatives, Foreign Currency Activity for Notional Amount Of Derivatives due to Foreign Currency Balance at ending of period Notes to Financial Statements [Abstract] Notes to Financial Statements [Abstract] Derivative Financial Instruments Derivative Instruments and Hedging Activities Disclosure [Text Block] Income Statement [Abstract] Revenue Revenues [Abstract] Realized Investment Gain (Loss) Realized Investment Gains (Losses) [Abstract] Other-Than-Temporary Impairment Loss on Fixed Maturity Securities Other-than-temporary Impairment Loss, Debt Securities, Portion Recognized in Earnings Net Realized Investment Gain (Loss) Total Revenue Revenues 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 Compensation Expense Labor and Related Expense Other Expenses Total Benefits and Expenses Benefits, Losses and Expenses Income Before Income Tax 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 Net Income Net Income Per Common Share Earnings Per Share [Abstract] Basic Earnings Per Share, Basic Assuming Dilution Earnings Per Share, Diluted 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 Common Shares - 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 Common Shares - Assuming Dilution Weighted Average Number of Shares Outstanding, Diluted Debt - Additional Information [Abstract] Debt - Additional Information [Abstract] Debt Narrative Detail Information Debt Narrative Detail Information [Table] Debt Narrative Detail Information Legal Entity Legal Entity [Axis] Entity Entity [Domain] Northwind Holdings LLC Northwind Holdings LLC [Member] Northwind Holdings LLC [Member] Credit Facility Credit Facility [Axis] Credit Facility Credit Facility [Domain] Revolving Credit Facility expiring 2024 Revolving Credit Facility expiring 2024 [Member] Revolving Credit Facility expiring 2024 [Member] Revolving Credit Facility expiring 2022 Revolving Credit Facility expiring 2022 [Member] Revolving Credit Facility expiring 2022 [Member] Subsequent Event Type Subsequent Event Type [Axis] Subsequent Event Type Subsequent Event Type [Domain] Subsequent Event Subsequent Event [Member] Debt Narrative Detail Information Debt Narrative Detail Information [Line Items] [Line Items] for Debt Narrative Detail Information Principal Payments on Long-term Debt Debt Instrument, Periodic Payment, Principal Line of Credit Facility, Maximum Borrowing Capacity Line of Credit Facility, Maximum Borrowing Capacity Line Of Credit Facility Maximum Borrowing Capacity If Requested Line Of Credit Facility Maximum Borrowing Capacity If Requested Line Of Credit Facility Maximum Borrowing Capacity If Requested Letters of Credit Outstanding, Amount Letters of Credit Outstanding, Amount Amount Outsanding on Credit Facility Long-term Line of Credit 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 Accumulated Other Comprehensive Income (Loss) Comprehensive Income (Loss) Note [Text Block] Employee Benefit Plans Compensation and Employee Benefit Plans, Other than Share-based Compensation [Text Block] Investments Additional Information [Abstract] Disclosure - Investments - Additional Information [Abstract] Schedule of Investments Schedule of Investments [Table] 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] Bonds Bonds [Member] Financing Receivable, Troubled Debt Restructuring Financing Receivable Portfolio Segment [Axis] Financing Receivable Portfolio Segment Financing Receivable Portfolio Segment [Domain] 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] Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Available-for-sale, Debt Securities Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Available-for-sale, Debt Securities Impaired Financing Receivable, Average Recorded Investment Impaired Financing Receivable, Average Recorded Investment 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 Number of Loan Modifications due to Loan Foreclosure Financing Receivable, Modifications, Subsequent Default, Number of Contracts Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing 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 Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method Impaired Financing Receivable, with No Related Allowance, 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 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] Reconciliation of Total Revenue to Adjusted Operating Revenue Total Revenue Net Realized Investment Gain (Loss) Adjusted Operating Revenue Reconciliation of Income Before Income Tax to Adjusted Operating Income Segment Reporting Information, Income (Loss) before Income Taxes [Abstract] Adjusted Operating Income 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 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] 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 Relationship Hedging Relationship [Axis] Hedging Relationship Hedging Relationship [Domain] Cash Flow Hedging Cash Flow Hedging [Member] Fair Value Hedging Fair Value Hedging [Member] Designated as Hedging Instrument Designated as Hedging Instrument [Member] Derivative Instrument by Balance Sheet Location Other Liabilities Other Liabilities [Member] Asset Derivatives Fair Value Derivative Asset, Fair Value, Gross Asset Liability Derivatives Fair Value Derivative Liability, Fair Value, Gross Liability Fair Value Hedges Carrying Amount of Hedged Assets and Liabilities and Cumulative Basis Adjustments [Abstract] Fair Value Hedges Carrying Amount of Hedged Assets and Liabilities and Cumulative Basis Adjustments [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) Accumulated Other Comprehensive Income Accumulated Other Comprehensive Income (Loss) [Table] Net Gain on Hedges Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] Foreign Currency Translation Adjustment Accumulated Foreign Currency Adjustment Attributable to Parent [Member] Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income (Loss) [Line Items] Balance at Beginning of Period Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Other Comprehensive Income (Loss), before Reclassifications, net of tax Other Comprehensive Income (Loss), before Reclassifications, Net of Tax 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. Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax Balance at End of Period Federal Home Loan Bank Carrying Value of Common Stock, Collateral Posted, and Advances [Abstract] Federal Home Loan Bank Carrying Value of Common Stock, Collateral Posted, and Advances [Abstract] Federal Home Loan Bank Carrying Value of Common Stock, Collateral Posted and Advances Received 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] Schedule of Federal Home Loan Bank Information Schedule of Federal Home Loan Bank Information [Line Items] Schedule of Federal Home Loan Bank Information [Line Items] Federal Home Loan Bank Stock Federal Home Loan Bank Stock Federal Home Loan Bank, Advances, Branch of FHLB Bank, Amount of Advances Federal Home Loan Bank, Advances, Branch of FHLB Bank, Amount of Advances Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged Accounting Developments [Abstract] Accounting Developments [Abstract] Schedule of Error Corrections and Prior Period Adjustment Restatement [Table] Schedule of Error Corrections and Prior Period Adjustment Restatement [Table] Adjustments for New Accounting Pronouncements Adjustments for New Accounting Pronouncements [Axis] Type of Adoption Type of Adoption [Domain] Accounting Standards Update 2016-01 Accounting Standards Update 2016-01 [Member] Error Corrections and Prior Period Adjustments Restatement Error Corrections and Prior Period Adjustments Restatement [Line Items] Accumulated Other Comprehensive Loss Accumulated Other Comprehensive Income (Loss), Net of Tax Retained Earnings Retained Earnings (Accumulated Deficit) Deferred Tax Liabilities, Net Deferred Tax Liabilities, Net Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Asset Class Asset Class [Axis] Asset Class Asset Class [Domain] 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] Assets Assets [Abstract] Investments Investments [Abstract] Fixed Maturity Securities - at fair value (amortized cost: $40,474.2; $40,275.2) Mortgage Loans Mortgage Loans on Real Estate, Commercial and Consumer, Net Policy Loans Loans, Gross, Insurance Policy 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 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 Long-term Debt Long-term Debt and Capital Lease Obligations 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: 305,565,569 and 305,104,548 shares Common Stock, Value, Issued Additional Paid-in Capital Additional Paid in Capital, Common Stock Accumulated Other Comprehensive Loss Retained Earnings Treasury Stock - at cost: 93,275,293 and 90,551,513 shares Treasury Stock, Value Total Stockholders' Equity Total Liabilities and Stockholders' Equity Liabilities and Equity 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] 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] Distribution of the Maturity for Fixed Maturity Securities [Abstract] Distribution of the Maturity for Fixed Maturity Securities [Abstract] Debt Securities, Available-for-sale [Table] 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] Available for Sale Securities Unrealized Gain Position Fair Value Available for Sale Securities Unrealized Gain Position Fair Value [Member] Available For Sale Securities Gross Unrealized Gain [Member] Available for Sale Securities Unrealized Loss Position Fair Value Available for Sale Securities Unrealized Loss Position Fair Value [Member] Available For Sale Securities Gross Unrealized Loss [Member] Debt Securities, Available-for-sale, Amortized Cost, Fiscal Year Maturity Debt Securities, Available-for-sale, Amortized Cost, Fiscal Year Maturity [Abstract] Fixed Maturity Securities, 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 Fixed Maturity Securities, 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 Fixed Maturity Securities, 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 Fixed Maturity Securities, 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 Fixed Maturity Securities, 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 Fixed Maturity Securities, Maturity, without Single Maturity Date, Amortized Cost Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Amortized Cost Fixed Maturity Securities, 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] Fixed Maturity Securities, 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 Fixed Maturity Securities, 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 Fixed Maturity Securities, 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 Fixed Maturity Securities, 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 Fixed Maturity Securities, Fair Value Gross Subtotal Available for sale Securities Debt Maturities Fair Value Gross Subtotal Available-for-sale Securities, Debt Maturities, Fair Value, Gross Subtotal Fixed Maturity Securities, Fair Value Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Fair Value Nature and Amount of Collateral Received From and Posted To Our Derivative Counterparties [Abstract] Nature and Amount of Collateral Received From and Posted To Our Derivative Counterparties [Abstract] Nature and Amount of Collateral Received From and Posted To Our Derivative Counterparties Nature and Amount of Collateral Received From and Posted To Our Derivative Counterparties [Table] Nature and Amount of Collateral Received From and Posted To Our Derivative Counterparties [Table] Total or Partial Total or Partial [Axis] Total or Partial [Axis] Total or Partial Total or Partial [Domain] [Domain] for Total or Partial [Axis] Total Amount Total Amount [Member] Total Amount Derivative, Collateral, Obligation to Return Cash Derivative, Collateral, Obligation to Return Cash Derivative, Collateral, Obligation to Return Securities Derivative, Collateral, Obligation to Return Securities 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 Expense Stockholders' Equity and Earnings Per Common Share [Abstract] Stockholders' Equity and Earnings Per Common Share [Abstract] Earnings Per Share Disclosure Earnings Per Share [Text Block] Stockholders' Equity Disclosure Stockholders' Equity Note Disclosure [Text Block] Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract] 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 Available-for-sale Securities, Continuous Unrealized Loss Position of Less than 12 Months, Accumulated Loss Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated 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 Available-for-sale Securities, Continuous Unrealized Loss Position of 12 Months or Longer, Accumulated Loss Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate, Other Disclosure [Abstract] Mortgage Loans on Real Estate Schedule SEC Schedule, 12-29, Real Estate Companies, Investment in 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] Other Property Other Property [Member] Investment Geographic Region Investment Geographic Region [Axis] Investment Geographic Region Investment Geographic Region [Domain] New England New England [Member] New England [Member] Middle 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] Mortgage Loans on Real Estate SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items] Percent of Total Percentage of loan portfolio Percentage Of Loan Portfolio Number of Operating Segments Number of Operating Segments Nature and Amount of Collateral Received From and Posted To Our Derivative Counterparties Nature and Amount of Collateral Received From and Posted To Our Derivative Counterparties [Table Text Block] [Table Text Block] for Nature and Amount of Collateral Received From and Posted To Our Derivative Counterparties [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 of Derivative Financial Instruments Designated as Hedging Instruments, Consolidated Statements of Income Derivative Instruments, Gain (Loss) [Table Text Block] Location of Gains and Losses of Derivative Financial Instruments Designated as Hedging Instruments, Statements of 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] New Accounting Pronouncements or Change in Accounting Principle New Accounting Pronouncements or Change in Accounting Principle [Table] Accounting Standards Update 2016-02 Accounting Standards Update 2016-02 [Member] New Accounting Pronouncements or Change in Accounting Principle New Accounting Pronouncements or Change in Accounting Principle [Line Items] 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 Debt Securities, Available-for-sale [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 (Loss) on All Other Derivatives Foreign Currency Transactions Foreign Currency Transaction Gain (Loss), before Tax 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 Liabilities Offsetting Derivative Assets in Balance Sheet Derivative Asset, Fair Value, Gross Liability Net Derivative Assets Reported in Balance Sheet Securities Received as Collateral on Derivative Assets Cash Collateral from Counterparties 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 Assets Offsetting Derivative Liabilities in Balance Sheet Derivative Liability, Fair Value, Gross Asset Net Derivative Liabilities Reported in Balance Sheet Cash Collateral to Counterparties Derivative, Collateral, Right to Reclaim Cash Securities Given as Collateral on Derivative Liabilities Derivative, Collateral, Right to Reclaim Securities 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 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] Gain (Loss) Recognized in OCI on Derivatives (Effective Portion) Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax Fair Value, By Balance Sheet Grouping [Abstract] Fair Value, By Balance Sheet Grouping [Abstract] Fair Value, by Balance Sheet Grouping Fair Value, by Balance Sheet Grouping [Table] Fair Value, Balance Sheet Grouping, Financial Statement Captions Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract] Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract] Mortgage Loans, Fair Value Mortgages Held-for-sale, Fair Value Disclosure Mortgage Loans, Carrying Value Policy Loans, Fair Value Loans Receivable, Fair Value Disclosure Policy Loans, Carrying Value Other Long-term Investments Long-term Investments [Abstract] Miscellaneous Long-Term Investments, Fair Value Miscellaneous Long-Term Investments Miscellaneous Long-Term Investments Miscellaneous Long-Term Investments, Carrying Value Miscellaneous Long-Term Investments, Carrying Value Miscellaneous Long-Term Investments, Carrying Value Total Financial Instruments Assets Not Carried at Fair Value Financial Instruments, Financial Assets Fair Value Disclosure, Total Financial Instruments, Financial Assets Fair Value Disclosure, Total Financial Instruments, Financial Assets Fair Value Disclosure, Carrying Value Financial Instruments, Financial Assets Fair Value Disclosure, Carrying Value Financial Instruments, Financial Assets Fair Value Disclosure, Carrying Value Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract] Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract] Long-term Debt, Fair Value Notes Payable, Fair Value Disclosure Long-term Debt, Carrying Value Collateralized Financings [Abstract] Collateralized Financings [Abstract] Federal Home Loan Bank (FHLB) Funding Agreements, Fair Value Federal Home Loan Bank Borrowings, Fair Value Disclosure Federal Home Loan Bank (FHLB) Funding Agreements, Carrying Value Federal Home Loan Bank Advances Other Liabilities, Unfunded Commitments Qualified Affordable Housing Project Investments, Commitment Total Financial Liabilities, Carrying Value Total Financial Instrument Liabilities Not Carried at Fair Value Total Financial Instrument Liabilities Not Carried at Fair Value Location of Gains and Losses of Derivative Financial Instruments Designated as Hedging Instruments, Consolidated Statements of Income [Abstract] Location of Gains and Losses of Derivative Financial Instruments Designated as Hedging Instruments, Consolidated Statements of Income [Abstract] Investment Income Investment Income [Member] Interest Expense Interest Expense [Member] Derivative, Gain (Loss) on Derivative, Net 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 Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure Commitments and Contingencies Disclosure [Text Block] 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] All Other Corporate Bonds - Private Measurement Input Type Measurement Input Type [Axis] Measurement Input Type Measurement Input Type [Domain] 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 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 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, Meas