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] 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 Operating Revenue Operating Revenue Operating Revenue Operating Income (Loss) Operating Income (Loss) Defined Benefit Plan [Abstract] Schedule of Net Periodic Benefit Costs Schedule of Net Benefit Costs [Table Text Block] Fair Value Disclosures [Abstract] Carrying Amount and Fair Value of Financial Instruments Fair Value, by Balance Sheet Grouping [Table Text Block] Fair Values by Fair Value Heirarchy Input Level Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Transfers of Assets between Level 1 and Level 2 Fair Value Measurments Transfers of Assets between Level 1 and Level 2 Disclosure of the transfers between Level 1 and Level 2 during the period. Changes in Assets and Liabilities Measured at Fair Value on a Recurring Basis using Significant Unobservable Inputs Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] Quantitative Information Regarding Significant Unobservable Inputs Fair Value Inputs, Assets, Quantitative Information [Table Text Block] Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract] 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] Equity Components Equity Components [Axis] Equity Component Equity Component [Domain] Net Unrealized Gain on Securities Accumulated Net Investment Gain (Loss) Attributable to Parent [Member] Net Gain on Cash Flow 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 Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] Net Realized Investment Gain, 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) Net Income Net Income (Loss) 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 Operating Revenue and Operating Income by Segment to Total Revenue and Income Before Income Tax Reconciliation of Revenue from Segments to Consolidated [Table Text Block] Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure Commitments and Contingencies Disclosure [Text Block] Fair Values of Financial Instruments Additional Information [Abstract] Disclosure - Fair Values of Financial Instruments - Additional Information [Abstract] Fair Value Measurements Fair Value Measurements, Recurring and Nonrecurring [Table] 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] Range Range [Axis] Range Range [Domain] Minimum Minimum [Member] Maximum Maximum [Member] Fair Value, Hierarchy Fair Value, Hierarchy [Axis] Fair Value Hierarchy Fair Value Hierarchy [Domain] 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] 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. Private Equity Partnership Future Liquidation Term Private Equity Partnership Future Liquidation Term Private Equity Partnership Future Liquidation Term Long-term Debt Long-term Debt and Capital Lease Obligations 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 New Accounting Pronouncements and Changes in Accounting Principles [Abstract] Accounting Developments New Accounting Pronouncements and Changes in Accounting Principles [Text Block] Accounting Updates Adopted in 2017 Schedule of New Accounting Pronouncements and Changes in Accounting Principles [Table Text Block] Accounting Updates Outstanding Description of New Accounting Pronouncements Not yet Adopted [Text Block] Assets Assets Schedule of Net Unrealized Gain on Securities [Abstract] Schedule of Net Unrealized Gain on Securities [Abstract] Schedule of Net Unrealized Gain on Securities Schedule of Net Unrealized Gain on Securities [Table] Schedule of Net Unrealized Gain on Securities [Table] Component of Net Unrealized Gain on Securities Component of Net Unrealized Gain on Securities [Axis] Component of Net Unrealized Gain on Securities [Axis] Component of Net Unrealized Gain on Securities Component of Net Unrealized Gain on Securities [Domain] [Domain] for Component of Net Unrealized Gain on Securities [Axis] Fixed Maturity Securities Debt Securities [Member] Other Investments Other Investments [Member] Deferred Acquisition Costs Deferred Acquisition Costs [Member] Deferred Acquisition Costs [Member] Reserve for Future Policy and Contract Benefits Reserve for Future Policy and Contract Benefits [Member] Reserve for Future Policy and Contract Benefits [Member] Reinsurance Recoverable Reinsurance Recoverable 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), Available-for-sale Securities Adjustment, Net of Tax Change in Net Unrealized Gain on Securities Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax End of Period Balance Transfers of Assets between Level 1 and Level 2 [Abstract] Disclosure - Transfers of Assets between Level 1 and Level 2 [Abstract] 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 Second Quarter Second Quarter [Member] Second Quarter [Member] First and Second Quarters First and Second Quarters [Member] First and Second Quarters [Member] Major Types of Debt and Equity Securities Major Types of Debt and Equity Securities [Axis] Total Fixed Maturity Securities Major Types of Debt and Equity Securities [Domain] 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] Public Utilities Public Utility, Bonds [Member] All Other Corporate Bonds Corporate Debt Securities [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 Accounting Policies [Abstract] Basis of Presentation Basis of Accounting [Text Block] Notes to Financial Statements [Abstract] Notes to Financial Statements [Abstract] Derivative Financial Instruments Derivative Instruments and Hedging Activities Disclosure [Text Block] Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract] Schedule of Available-for-sale Securities Schedule of Available-for-sale Securities [Table] 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 Schedule of Available-for-sale Securities [Line Items] Fair Value of Securities in Continuous Unrealized Loss Possition for Less Than 12 Months Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value 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 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 Net Securities Borrowed Reported in Balance Sheet Securities Borrowed 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 Statement of Financial Position [Abstract] Investments Investments [Abstract] Fixed Maturity Securities, Amortized Cost Available-for-sale Debt Securities, Amortized Cost Basis Stockholders' Equity Stockholders' Equity Attributable to Parent [Abstract] Common Stock, Par Common Stock, Par or Stated Value Per Share Common Stock, Authorized Common Stock, Shares Authorized Common Stock, Issued Common Stock, Shares, Issued Treasury Stock, Shares at Cost Treasury Stock, Shares Derivative Financial Instruments Additional Information [Abstract] Disclosure - Derivative Financial Instruments - Additional Information [Abstract] Derivative Derivative [Table] Credit Exposure Credit Exposure [Axis] Credit Exposure [Axis] Credit Exposure Credit Exposure [Domain] [Domain] for Credit Exposure [Axis] 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 Credit Derivatives Contract Type Credit Derivatives Contract Type [Axis] Credit Derivatives Contract Type Credit Derivatives Contract Type [Domain] Receive Variable/Pay Fixed Derivative Financial Instruments Receive Variable Pay Fixed [Member] Derivative Financial Instruments, Receive Variable Pay Fixed [Member] Hedging Designation Hedging Designation [Axis] Hedging Designation Hedging Designation [Domain] Not Designated as Hedging Instrument Not Designated as Hedging Instrument [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] Receive Fixed/Pay Variable Derivative Financial Instruments Receive Fixed Pay Variable [Member] Derivative Financial Instruments, Receive Fixed Pay Variable [Member] Swaps Swap [Member] Credit Default Swaps Credit Default Swap [Member] Derivative Derivative [Line Items] Current Credit Exposure on Derivatives Fair Value, Concentration of Risk, Derivative Instruments, Assets Cash Collateral from Counterparties Carrying Value of Fixed Maturity Securities Posted as Collateral to Counterparties Available-for-sale Securities Pledged as Collateral Cash Collateral to Counterparties 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 Material Ineffectiveness on Cash Flow Hedges Gain on Cash Flow Hedge Ineffectiveness Gain from Components Excluded from Assessment of Cash Flow Hedge Effectiveness Gain (Loss) from Components Excluded from Assessment of Cash Flow Hedge Effectiveness, Net Approximate Amount of Net Deferred Gains on Derivative Instruments Expected to be Amortized During the Next Twelve Months Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months Change in Unrealized Gain (Loss) on Fair Value Hedging Instruments Change in Unrealized Gain (Loss) on Fair Value Hedging Instruments Notional Amount Of Derivatives Terminations Notional Amount Of Derivatives Terminations Notional Amount Of Derivatives, Terminations Loss on Derivative Contract Termination Loss on Contract Termination Material Ineffectiveness on Fair Value Hedges Gain on Fair Value Hedge Ineffectiveness 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 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 (Loss) Gain (Loss) on Investments Operating Revenue Income Before Income Tax Net Realized Investment Gain (Loss) Loss Related to Guaranty Fund Assessment Loss Related to Guaranty Fund Assessment Loss Related to Guaranty Fund Assessment Operating Income Fair Value Inputs, Quantitative Information [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] Asset Class Asset Class [Axis] Asset Class Asset Class [Domain] All Other Corporate Bonds - Private Equity Securities Equity Securities [Member] Liability Class Liability Class [Axis] Fair Value by Liability Class Fair Value by Liability Class [Domain] Embedded Derivative Liability Derivative Financial Instruments, Liabilities [Member] Weighted Average Weighted Average [Member] Fair Value, Inputs, Level 3 Fair Value, Inputs, Level 3 [Member] Unobservable Input Unobservable Input [Axis] Unobservable Input [Axis] Unobservable Input Unobservable Input [Domain] [Domain] for Unobservable Input [Axis] Market Convention Market Convention [Member] Represents a decision to price based on par value, cost, or owner's equity when limited data is available Projected Cash Flows Projected Cash Flows [Member] Represents various actuarial assumptions required to derive the liability cash flows including incidence, termination, and lapse rates 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] Fair Value of Financial Instrument Using Internally Derived Unobservable Inputs Fair Value of Financial Instrument Using Internally Derived Unobservable Inputs Fair Values of Financial Instruments Using Internally Derived Unobservable Inputs Comparability Adjustments Fair Value Inputs, Comparability Adjustments Discount for Size Fair Value Inputs, Discount for Size Fair Value Inputs, Discount for Size Lack of Marketability Fair Value Inputs, Discount for Lack of Marketability Volatility of Credit Fair Value Inputs, Entity Credit Risk Significant Assumptions to Calculating Fair Value of Level 3 Instrument Fair Value Measurements, Significant Assumptions Realized Investment Gains and Losses Reported in Consolidated Statements of Income [Abstract] Disclosure - Realized Investment Gains and Losses Reported in Consolidated Statements of Income [Abstract] Fixed Maturity Securities Available-for-sale Securities [Abstract] Gross Gains on Sales Available-for-sale Securities, Gross Realized Gains Gross Losses on Sales Available-for-sale Securities, Gross Realized Losses 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 Other than Temporary Impairment Losses, Investments Other than Temporary Impairment Losses, Investments Gain (Loss) on All Other Derivatives Derivative, Gain (Loss) on Derivative, Net Foreign Currency Transactions Foreign Currency Transaction Gain (Loss), before Tax Net Realized Investment Gain (Loss) 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 June 30 Plus Reinsurance Recoverable Balance at June 30 Basis of Accounting Basis of Accounting, Policy [Policy Text Block] Number of Operating Segments Number of Operating Segments Mortgage Loans on Real Estate, Other Required Disclosures [Abstract] Mortgage Loans on Real Estate Schedule Mortgage Loans on Real Estate Schedule [Table] Mortgage Loan Property Type Real Estate, Type of Property [Axis] Mortgage Loan Property Type Real Estate [Domain] Apartment Apartment Building [Member] Industrial Industrial Property [Member] Office Office Building [Member] Retail Retail Site [Member] 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 Mortgage Loans on Real Estate [Line Items] Mortgage Loans Mortgage Loans on Real Estate, Commercial and Consumer, Net Percent of Total Percentage of loan portfolio Percentage Of Loan Portfolio 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] Statement of Comprehensive Income [Abstract] Change in Net Unrealized Gain on Securities Before Adjustment, Tax Expense Other Comprehensive Income (Loss), Available-for-sale Securities, Tax Change in Adjustment to Deferred Acquisition Costs and Reserves for Future Policy and Contract Benefits, Net of Reinsurance, Tax Benefit Change in Adjustment to Deferred Acquisition Costs and Reserves for Future Policy and Contract Benefits, Net of Reinsurance, Tax Expense Tax effect from the unrealized adjustment to deferred acquisition costs and reserves for future policy and contract benefits for unrealized loss on securities during the period net of the effects of contracts assumed and ceded Change in Net Gain on Cash Flow Hedges, Tax 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 Insurance Product Line Products and Services [Axis] Insurance Product Line Products and Services [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] Loss Contingencies [Table] Loss Contingencies [Table] Litigation Status Litigation Status [Axis] Litigation Status Litigation Status [Domain] Settled Litigation Settled Litigation [Member] Loss Contingency Nature Loss Contingency Nature [Axis] Loss Contingency, Nature Loss Contingency, Nature [Domain] Unfavorable Regulatory Action Unfavorable Regulatory Action [Member] Before or After Tax Before or After Tax [Axis] Before or After Tax [Axis] Before or After Tax Before or After Tax [Domain] [Domain] for Before or After Tax [Axis] Net of Tax Net of Tax [Member] Net of Tax [Member] Loss Contingencies Loss Contingencies [Line Items] Loss Contingency, Loss in Period Loss Contingency, Loss in Period Loss Contingency Accrual, Insurance-related Assessment, Premium Tax Offset Loss Contingency Accrual, Insurance-related Assessment, Premium Tax Offset Loss Contingency, Loss in Period, Tax Loss Contingency, Loss in Period, Tax Loss Contingency, Loss in Period, Tax Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net [Abstract] Derivative Instruments, Gain (Loss) by Hedging Relationship, by Income Statement Location, by Derivative Instrument Risk Derivative Instruments, Gain (Loss) [Table] 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 Foreign Governments Foreign Government Debt Securities [Member] Amortized Cost of Fixed Maturity Securities Accumulated Gross Unrealized Gain on Securities Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax Accumulated Gross Unrealized Loss on Securities Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax Fair Value of Fixed Maturity Securities Available-for-sale Securities, Debt Securities 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 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 Upaid Claims and Claims Adjustment Expense 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 Accumulated Other Comprehensive Income (Loss) Comprehensive Income (Loss) Note [Text Block] Earnings Per Share, Basic and Diluted [Abstract] Numerator Net Income (Loss) Attributable to Parent [Abstract] Denominator (000s) Weighted Average Number of Shares Outstanding Reconciliation [Abstract] Weighted Average 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 Net Income Per Common Share Earnings Per Share [Abstract] Basic Earnings Per Share, Basic Assuming Dilution Earnings Per Share, Diluted 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 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 Debt - Additional Information [Abstract] Debt - Additional Information [Abstract] Debt Narrative Detail Information Debt Narrative Detail Information [Table] Debt Narrative Detail Information Income Statement Location Income Statement Location [Axis] Income Statement Location Income Statement Location [Domain] Net Realized Investments Gain (Loss) Net Realized Investments Gain Loss [Member] Net Realized Investments Gain (Loss) [Member] Extinguishment of Debt Extinguishment of Debt [Axis] Extinguishment of Debt, Type Extinguishment of Debt, Type [Domain] Long-term Debt Long-term Debt [Member] Legal Entity Legal Entity [Axis] Entity Entity [Domain] Northwind Holdings LLC Northwind Holdings LLC [Member] Northwind Holdings LLC [Member] Debt Narrative Detail Information Debt Narrative Detail Information [Line Items] [Line Items] for Debt Narrative Detail Information Extinguishment of Debt, Amount Extinguishment of Debt, Amount Principal Payments on Long-term Debt Debt Instrument, Periodic Payment, Principal Letters of Credit Outstanding, Amount Letters of Credit Outstanding, Amount Amount Outsanding on Credit Facility Long-term Line of Credit Notional Amounts for Each Category of Derivative Activity [Abstract] Disclosure - Notional Amounts for Each Category of Derivative Activity [Abstract] Forwards Forward Contracts [Member] Receive Fixed/Pay Fixed Derivative Financial Instruments Receive Fixed Pay Fixed [Member] Derivative Financial Instruments, Receive Fixed Pay Fixed [Member] Balance at beginning of period Additions Notional Amount Of Derivatives Additions Notional Amount Of Derivatives, Additions Terminations Balance at ending of period Investments, Debt and Equity Securities [Abstract] Investments Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] 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] Net Investment Income Investment Income [Member] Interest Expense Interest Expense [Member] Gain (Loss) Recognized in OCI on Derivatives (Effective Portion) Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion) Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net 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 2017 Repurchase Program Authorized in May 2017 [Member] Repurchase Program Authorized in May 2017 [Member] Repurchase Program Authorized in May 2016 Repurchase Program Authorized in May 2016 [Member] Repurchase Program Authorized in May 2016 [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 Earnings Per Share Disclosure Earnings Per Share [Text Block] Stockholders' Equity Disclosure Stockholders' Equity Note 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 Marketable Securities, Realized Loss, Other than Temporary Impairments, Amount 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 Tax Income Tax Expense (Benefit), Continuing Operations [Abstract] Current Current Income Tax Expense (Benefit) Deferred Deferred Income Tax Expense (Benefit) Total Income Tax Net Income Statement of Cash Flows [Abstract] Cash Flows from Operating Activities Net Cash Provided by (Used in) Operating Activities [Abstract] 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 Depreciation Depreciation, Amortization and Accretion, Net Other, Net Other Noncash Income (Expense) Net Cash Provided by Operating Activities Net Cash Provided by (Used in) Operating Activities Cash Flows from Investing Activities Net Cash Provided by (Used in) Investing Activities [Abstract] Proceeds from Sales of Fixed Maturity Securities Proceeds from Sale of Available-for-sale Securities Proceeds from Maturities of Fixed Maturity Securities Proceeds from Maturities, Prepayments and Calls of Available-for-sale Securities Proceeds from Sales and Maturities of Other Investments Proceeds from Sale and Maturity of Other Investments Purchases of Fixed Maturity Securities Payments to Acquire Available-for-sale Securities Purchases of Other Investments Payments to Acquire Other Investments Net Purchases of Short-term Investments Payments for (Proceeds from) Short-term Investments Net Increase (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] Issuance of Long-term Debt Proceeds from Issuance of Long-term Debt Long-term Debt Repayments Repayments of Long-term Debt Issuance of Common Stock Proceeds from Issuance of Common Stock Repurchase of Common Stock Payments for Repurchase of Common Stock Dividends Paid to Stockholders Payments of Dividends Other, Net Proceeds from (Payments for) Other Financing Activities Net Cash Provided (Used) by Financing Activities Net Cash Provided by (Used in) Financing Activities Net Increase (Decrease) in Cash and Bank Deposits Cash and Cash Equivalents, Period Increase (Decrease) Cash and Bank Deposits at Beginning of Year Cash Cash and Bank Deposits at End of Period 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 Amortized Cost and Fair Values of Securities by Security Type Schedule of Available-for-sale Securities Reconciliation [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] 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] 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 Investments [Table Text Block] Scenario Scenario [Axis] Scenario, Unspecified [Domain] Scenario, Unspecified [Domain] Class of Stock [Axis] Class of Stock [Axis] Class of Stock [Domain] Class of Stock [Domain] Assets Assets [Abstract] Fixed Maturity Securities - at fair value (amortized cost: $39,626.4; $39,552.7) Available-for-sale Securities Mortgage Loans Policy Loans Loans, Gross, Insurance Policy Other Long-term Investments Other Long-term Investments Short-term Investments Other Short-term Investments Total Investments Investments Other Assets Other Assets, Unclassified [Abstract] Cash and Bank Deposits Accounts and Premiums Receivable Premiums and Other Receivables, Net Reinsurance Recoverable Reinsurance Recoverables, 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 Other Assets Other Assets Total Assets Liabilities and Stockholders' Equity Liabilities and Equity [Abstract] Liabilities Liabilities [Abstract] Unearned Premiums Unearned Premiums Other Policyholders' Funds Other Policyholder Funds Income Tax Payable Taxes Payable Deferred Income Tax Deferred Tax Liabilities, Net Long-term Debt Payables for Collateral on Investments Collateralized Financings Other Liabilities Other Liabilities Total Liabilities Liabilities Commitments and Contingent Liabilities - Note 11 Commitments and Contingencies Common Stock, $0.10 par; authorized: 725,000,000 shares; issued: 304,082,323 and 303,552,934 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: 77,980,192 and 73,729,992 shares Treasury Stock, Value Total Stockholders' Equity Stockholders' Equity Attributable to Parent Total Liabilities and Stockholders' Equity Liabilities and Equity Fair Value, by Balance Sheet Grouping [Table] Measurement Basis Measurement Basis [Axis] Basis of Measurement Basis of Measurement [Domain] [Domain] for Basis of Measurement [Axis] Portion at Fair Value Measurement Portion at Fair Value Measurement [Member] Fair Value Estimate of Fair Value Measurement [Member] Carrying Amount Reported Value Measurement [Member] Fair Value by Balance Sheet Grouping Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fixed Maturity Securities Other Long-term Investments Derivative Assets Equity Securities Marketable Securities, Equity Securities Miscellaneous Long-Term Investments Miscellaneous Long-Term Investments Miscellaneous Long-Term Investments Policyholders' Funds Policyholder Funds [Abstract] Deferred Annuity Products Deferred Annuity Products Deferred Annuity Products Supplementary Contracts without Life Contingencies Supplementary Contracts without Life Contingencies Supplementary Contracts Without Life Contingencies Payables for Collateral on Investments Collateralized Financings [Abstract] Federal Home Loan Bank (FHLB) Funding Agreements Federal Home Loan Bank, Advances, Branch of FHLB Bank, Amount of Advances Other Liabilities Other Liabilities, Unclassified [Abstract] Derivative Liabilities Embedded Derivative in Modified Coinsurance Arrangement Embedded Derivative, Fair Value of Embedded Derivative Liability Unfunded Commitments to Investment Partnerships Unfunded commitment to fund tax credit partnership investments Unfunded Commitments and Standby Letters of Credit Common Stock Common Stock [Member] Additional Paid-in Capital Additional Paid-in Capital [Member] Accumulated Other Comprehensive Income 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 Year Common Stock Activity Stock Issued During Period, Value, New Issues Other Comprehensive Income Other Comprehensive Income (Loss), Net of Tax Dividends to Stockholders (per common share: $0.40; $0.37) Dividends, Cash Purchases of Treasury Stock Balance at End of Period Notional Amounts for Each Category of Derivative Activity Schedule of Derivative Instruments [Table Text Block] Location and Fair Values of Derivative Financial Instruments Schedule of Derivative Instruments in Statement of Financial Position, Fair Value [Table Text Block] Location of Gains and Losses on Derivative Instruments Designated as Cash Flow Hedging Instruments Derivative Instruments, Gain (Loss) [Table Text Block] Gains and Losses on Derivatives Not Designated as Hedging Instruments Schedule of Other Derivatives Not Designated as Hedging Instruments, Statements of Financial Performance and Financial Position, Location [Table Text Block] Distribution of the Maturity Dates for Fixed Maturity Securities [Abstract] Disclosure - Distribution of the Maturity Dates for Fixed Maturity Securities [Abstract] Gain (Loss) on Investments by Category Investments by Category [Axis] Marketable Securities and Investments Held at Cost Marketable Securities and Investments Held at Cost [Domain] Fair Value of Fixed Maturity Securities in Unrealized Gain Position Available for Sale Securities Unrealized Gain Position Fair Value [Member] Available For Sale Securities Gross Unrealized Gain [Member] Fair Value of Fixed Maturity Securities in Unrealized Loss Position Available for Sale Securities Unrealized Loss Position Fair Value [Member] Available For Sale Securities Gross Unrealized Loss [Member] Available-for-Sale Securities, Total Amortized Cost Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Fiscal Year Maturity [Abstract] 1 year or less Available-for-sale Securities, Debt Maturities, Next Twelve Months, Amortized Cost Basis Over 1 year through 5 years Available-for-sale Securities, Debt Maturities, Year Two Through Five, Amortized Cost Basis Over 5 years through 10 years Available-for-sale Securities, Debt Maturities, Year Six Through Ten, Amortized Cost Basis Over 10 years Available-for-sale Securities, Debt Maturities, after Ten Years, Amortized Cost Basis Available-for-sale Securities, Debt Maturities, Gross Subtotal Available for sale Securities Debt Maturities Amortized Cost Gross Subtotal Available-for-sale Securities, Debt Maturities, Amortized Cost, Gross Subtotal Mortgage/Asset-Backed Securities Available-for-sale Securities, Debt Maturities, without Single Maturity Date, Amortized Cost Basis Available-for-Sale Securities, Unrealized Gain Position, Gross Gain Available for Sale Securities Unrealized Gain Position Gross Gain Available-For-Sale Securities, Debt Maturities Unrealized Gain Position Gross Gain Abstract 1 year or less Available For Sale Securities Debt Maturities Within One Year Unrealized Gain Position Gross Gain Available-For-Sale Securities, Debt Maturities Within One Year Unrealized Gain Position Gross Gain Over 1 year through 5 years Available For Sale Securities Debt Maturities After One Through Five Years Unrealized Gain Position Gross Gain Available-For-Sale-Securities, Debt Maturities After One Through Five Years Unrealized Gain Position Gross Gain Over 5 years through 10 years Available For Sale Securities Debt Maturities After Five Through Ten Years Unrealized Gain Position GrossGain Available-For-Sale Securities, Debt Maturities After Five Through Ten Years Unrealized Gain Position GrossGain Over 10 years Available For Sale Securities Debt Maturities After Ten Years Unrealized Gain Position Gross Gain Available-For-Sale, Securities Debt Maturities After Ten Years Unrealized Gain Position Gross Gain Available-For-Sale Securities, Debt Maturities Unrealized Gain Position, Gross Gain, Gross Subtotal Available For Sale Securities Debt Maturities Unrealized Gain Position Gross Gain Gross Subtotal Available-For-Sale Securities, Debt Maturities Unrealized Gain Position, Gross Gain, Gross Subtotal Mortgage/Asset-Backed Securities Available For Sale Securities Debt Maturities Without Single Maturity Date Unrealized Gain Position Gross Gain Available-For-Sale Securities, Debt Maturities Without Single Maturity Date Unrealized Gain Position Gross Gain Total Fixed Maturity Securities Available for sale Securities, Debt Maturities Unrealized Gain Position Gross Gain Available for sale Securities, Debt Maturities Unrealized Gain Position Gross Gain Fair Value Maturity Distribution Fair Value Maturity Distribution [Abstract] Fair Value Maturity Distribution [Abstract] 1 year or less Available-for-sale Securities, Debt Maturities, Next Twelve Months, Fair Value Over 1 year through 5 years Available-for-sale Securities, Debt Maturities, Year Two Through Five, Fair Value Over 5 years through 10 years Available-for-sale Securities, Debt Maturities, Year Six Through Ten, Fair Value Over 10 years Available-for-sale Securities, Debt Maturities, after Ten Years, Fair Value Available-for-sale Securities, Debt Maturities, Fair Value, Gross Subtotal Available for sale Securities Debt Maturities Fair Value Gross Subtotal Available-for-sale Securities, Debt Maturities, Fair Value, Gross Subtotal Mortgage/Asset-Backed Securities Available-for-sale Securities, Debt Maturities, without Single Maturity Date, Fair Value Total Fixed Maturity Securities Available-for-Sale Securities, Unrealized Loss Position, Gross Loss Available for Sale Securities Unrealized Loss Position Gross Loss Available-For-Sale Securities, Debt Maturities Unrealized Loss Position Gross Loss Abstract 1 year or less Available For Sale Securities Debt Maturities Within One Year Unrealized Loss Position Gross Loss Available-For-Sale Securities, Debt Maturities Within One Year Unrealized Loss Position Gross Loss Over 1 year through 5 years Available For Sale Securities Debt Maturities After One Through Five Years Unrealized Loss Position Gross Loss Available-For- Sale Securities, Debt Maturities After One Through Five Years Unrealized Loss PositionGrossLoss Over 5 years through 10 years Available For Sale Securities Debt Maturities After Five Through Ten Years Unrealized Loss PositionGross Loss Available-For-Sale Securities, Debt Maturities After Five Through Ten Years Unrealized Loss PositionGross Loss Over 10 years Available For Sale Securities Debt Maturities After Ten Years Unrealized Loss Position Gross Loss Available-For-Sale Securities, Debt Maturities After Ten Years Unrealized Loss Position Gross Loss Available-For-Sale Securities, Debt Maturities Unrealized Gain Position, Gross Loss, Gross Subtotal Available For Sale Securities Debt Maturities Unrealized Gain Position Gross Loss Gross Subtotal Available-For-Sale Securities, Debt Maturities Unrealized Gain Position, Gross Loss, Gross Subtotal Mortgage/Asset-Backed Securities Available For Sale Securities Debt Maturities Without Single Maturity Date Unrealized Loss Position Gross Loss Available-For-Sale Securities, Debt Maturities Without Single Maturity Date Unrealized Loss Position Gross Loss Total Fixed Maturity Securities Available For Sale Securities Unrealized Loss Position Gross Loss Subtoatl Available-For-Sale Securities, Unrealized Loss Position Gross Loss 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] Accumulated Other Comprehensive Income Accumulated Other Comprehensive Income (Loss) [Table] Foreign Currency Translation Adjustment Accumulated Foreign Currency Adjustment Attributable to Parent [Member] Accumulated Other Comprehensive Income Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income, 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 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 Net Other Comprehensive Income (Loss) Balance at End of Period Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract] Fair Value Measurements by Input Level Fixed Maturity Securities Marketable Securities, Fixed Maturities [Abstract] Fair Values of Financial Instruments Fair Value Disclosures [Text Block] 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] Document Document and Entity Information [Abstract] Document - Document and Entity Information [Abstract] Entity Registrant Name Entity Registrant Name Trading Symbol Trading Symbol Entity Central Index Key Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Document Type Document Type Document Period End Date Document Period End Date Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Amendment Flag Amendment Flag Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Employee Benefit Plans Compensation and Employee Benefit Plans, Other than Share-based Compensation [Text Block] Debt and Other Disclosures [Abstract] Debt and Other Disclosures [Abstract] Debt Disclosure Debt Disclosure [Text Block] Liability for Future Policy Benefits and Unpaid Claims Disclosure Liability for Future Policy Benefits and Unpaid Claims Disclosure [Text Block] 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) Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment Net Periodic Benefit Cost Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Segment Information Segment Reporting Disclosure [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] 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] Starmount Starmount [Member] Starmount [Member] External Credit Rating by Grouping External Credit Rating by Grouping [Axis] External Credit Rating by Grouping External Credit Rating by Grouping [Domain] External Credit Rating, Investment Grade External Credit Rating, Investment Grade [Member] External Credit Rating, Non Investment Grade External Credit Rating, Non Investment Grade [Member] Variable Interest Entities by Classification of Entity Variable Interest Entities [Axis] Variable Interest Entity, Classification Variable Interest Entity, Classification [Domain] Partnership Interests In Tax Credit Investments Partnership Interests In Tax Credit Investments [Member] Partnership Interests In Tax Credit Investments [Member] Equity Method Investments Equity Method Investments [Member] Entity Classification Entity Classification [Axis] Entity Classification [Axis] Entity Classification Entity Classification [Domain] [Domain] for Entity Classification [Axis] Special Purpose Entity Special Purpose Entity [Member] Special Purpose Entity [Member] Bonds Bonds [Member] Partnership Interest Partnership Interest [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] 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] Mortgage Loans as Collateral Collateralized Mortgage Backed Securities [Member] Schedule of Investments Schedule of Investments [Line Items] Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax Available-for-sale Securities, Accumulated Gross Unrealized Gain (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. 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 Available-for-sale Securities, Gross Unrealized Gain (Loss) Available-for-sale Securities, Gross Unrealized Gain (Loss) 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 Unconditional Commitment to Fund Private Equity Partnerships Unfunded Unconditional Commitment to Fund Private Equity Partnerships Unfunded Unconditional Commitment to Fund Private Equity Partnerships Commitment to Fund Partnership Equity Investments Commitment to fund partnership Equity Investments Commitment To Fund Partnership Equity Investments Gain (Loss) on Investments, Excluding Other than Temporary Impairments 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 Number of Financing Receivables on Nonaccrual Status Count of Financing Receivable, Recorded Investment, Nonaccrual status Number (Count) of Financing Receivable, Recorded Investment, Nonaccrual status 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 Financing Receivable, Allowance for Credit Losses Financing Receivable, Allowance for Credit Losses Provision for Loan and Lease Losses Provision for Loan and Lease Losses Impaired Financing Receivable, Average Recorded Investment Impaired Financing Receivable, 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 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 Federal Home Loan Bank Stock Federal Home Loan Bank Stock Collateral Pledged to Federal Home Loan Bank (FHLB) Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged 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 of $206.5; $479.9; $295.5; $894.2) Change in Adjustment to Deferred Acquisition Costs and Reserves for Future Policy and Contract Benefits, Net of Reinsurance (net of tax benefit of $162.6; $367.6; $229.9; $655.3) Change in Adjustment to Deferred Acquisition Costs and Reserves for Future Policy and Contract Benefits, Net of Reinsurance and Net of Tax Expense Benefit Unrealized adjustment to deferred acquisition costs and reserves for future policy and contract benefits for unrealized loss on securities during the period net of the effects of contracts assumed and ceded, net of tax. Change in Net Gain on Cash Flow Hedges (net of tax benefit of $6.3; $4.4; $12.3; $18.0) Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax Change in Foreign Currency Translation Adjustment Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax Change in Unrecognized Pension and Postretirement Benefit Costs (net of tax expense of $1.3; $2.0; $2.8; $3.6) Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax Total Other Comprehensive Income Comprehensive Income Comprehensive Income (Loss), Net of Tax, Attributable to Parent 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] Designated as Hedging Instrument Designated as Hedging Instrument [Member] Credit Risk Contract Credit Risk Contract [Member] Derivative Instrument by Balance Sheet Location Other Liabilities Other Liabilities [Member] Asset Derivatives Fair Value Liability Derivatives Fair Value Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table] 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