Unum (UNM) 10-Q 6 May 21 2021 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2021	May 04, 2021
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Amendment Flag	false
Document Period End Date	Mar. 31, 2021
Document Fiscal Year Focus	2021
Current Fiscal Year End Date	--12-31
Document Fiscal Period Focus	Q1
Document Transition Report	false
Entity File Number	001-11294
Entity Registrant Name	Unum Group
Entity Central Index Key	0000005513
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	62-1598430
Entity Address, Address Line One	1 Fountain Square
Entity Address, City or Town	Chattanooga,
Entity Address, State or Province	TN
Entity Address, Postal Zip Code	37402
City Area Code	423
Local Phone Number	294-1011
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		204,240,512
NEW YORK STOCK EXCHANGE, INC. | Common Class A
Entity Information [Line Items]
Title of 12(g) Security	Common stock, $0.10 par value
Trading Symbol	UNM
Security Exchange Name	NYSE
NEW YORK STOCK EXCHANGE, INC. | 6.250% Junior Subordinated Notes due 2058
Entity Information [Line Items]
Title of 12(g) Security	6.250% Junior Subordinated Notes due 2058
Trading Symbol	UNMA
Security Exchange Name	NYSE

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Investments
Fixed Maturity Securities - at fair value (amortized cost of $36,565.9; $36,546.5; allowance for credit losses of $7.3; $6.8)	$ 42,076	$ 44,137.3
Mortgage Loans (net of allowance for credit losses of $11.5; $13.1)	2,402.2	2,432.1
Policy Loans	3,628.8	3,683.9
Other Long-term Investments	995.3	960.2
Short-term Investments	756.1	1,470
Total Investments	49,858.4	52,683.5
Other Assets
Cash and Bank Deposits	561.8	197
Accounts and Premiums Receivable (net of allowance for credit losses of $33.7; $38.8)	1,656.1	1,519.3
Reinsurance Recoverable (net of allowance for credit losses of $11.7; $11.7)	11,550.2	10,666
Accrued Investment Income	668.7	611.4
Deferred Acquisition Costs	2,254.8	2,272.6
Goodwill	353	353
Property and Equipment	500.6	498
Income Tax Receivable	43.3	72.7
Other Assets	1,809.7	1,752.3
Total Assets	69,256.6	70,625.8
Liabilities
Policy and Contract Benefits	1,899.3	1,855.4
Reserves for Future Policy and Contract Benefits	48,112.3	49,653
Unearned Premiums	425	349.3
Other Policyholders' Funds	1,736.1	1,663.9
Deferred Income Tax	319.2	416.1
Long-term Debt	3,346.8	3,345.7
Other Liabilities	2,847.8	2,471.4
Total Liabilities	58,686.5	59,754.8
Commitments and Contingent Liabilities - Note 11
Stockholders' Equity
Common Stock, $0.10 par; authorized: 725,000,000 shares; issued: 307,065,068 and 306,566,572 shares	30.7	30.7
Additional Paid-in Capital	2,380.8	2,376.2
Accumulated Other Comprehensive Income (Loss)	(24.9)	374.2
Retained Earnings	11,363.2	11,269.6
Treasury Stock - at cost: 102,876,514 shares	(3,179.7)	(3,179.7)
Total Stockholders' Equity	10,570.1	10,871
Total Liabilities and Stockholders' Equity	$ 69,256.6	$ 70,625.8

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Investments
Amortized Cost of Fixed Maturity Securities	$ 36,565.9	$ 36,546.5
Debt Securities, Available-for-sale, Allowance for credit losses for Fixed Maturity Securities	7.3	6.8
Financing Receivable, Allowance for Credit Losses, Mortgage Loans	11.5	13.1
Other Assets
Accounts Receivable, after Allowance for Credit Loss	33.7	38.8
Reinsurance Recoverable, Allowance for Credit Loss	$ 11.7	$ 11.7
Stockholders' Equity
Common Stock, Par Value (in dollars per share)	$ 0.10	$ 0.10
Common Stock, Shares Authorized	725,000,000	725,000,000
Common Stock, Shares Issued	307,065,068	306,566,572
Treasury Stock, Shares at Cost	102,876,514	102,876,514

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Revenue
Premium Income	$ 2,378.3	$ 2,371.4
Net Investment Income	548.7	585
Net Realized Investment Gain (Loss)	84.6	(144)
Other Income	60.4	58.7
Total Revenue	3,072	2,871.1
Benefits and Expenses
Benefits and Change in Reserves for Future Benefits	2,051.2	1,854.8
Commissions	259.9	279.2
Interest and Debt Expense	44.4	45.7
Deferral of Acquisition Costs	(130.6)	(162)
Amortization of Deferred Acquisition Costs	166.4	176.2
Compensation Expense	236.9	239.5
Other Expenses	245	235.6
Total Benefits and Expenses	2,873.2	2,669
Income Before Income Tax	198.8	202.1
Income Tax Expense (Benefit)
Current	67.5	57.6
Deferred	(21.7)	(16.5)
Total Income Tax Expense	45.8	41.1
Net Income	$ 153	$ 161
Net Income Per Common Share
Basic	$ 0.75	$ 0.79
Assuming Dilution	$ 0.75	$ 0.79

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement of Comprehensive Income [Abstract]
Net Income	$ 153	$ 161
Other Comprehensive Income (Loss)
Change in Net Unrealized Gain on Securities Before Adjustment (net of tax benefit of $434.2; $436.5)	(1,646)	(1,666.7)
Change in Adjustment to Deferred Acquisition Costs and Reserves for Future Policy and Contract Benefits, Net of Reinsurance (net of tax expense of $331.8; $380.8)	1,256.5	1,446.1
Change in Net Gain on Hedges (net of tax expense (benefit) of $(5.4); $6.6)	(20.7)	22.8
Change in Foreign Currency Translation Adjustment (net of tax expense of $1.8; $2.1)	7.3	(63.6)
Change in Unrecognized Pension and Postretirement Benefit Costs (net of tax expense of $1.2; $1.9)	(3.8)	(7)
Total Other Comprehensive Loss	(399.1)	(254.4)
Comprehensive Loss	$ (246.1)	$ (93.4)

CONSOLIDATED STATEMENTS OF CO_2

CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (Parenthetical) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement of Comprehensive Income [Abstract]
Change in Net Unrealized Gain on Securities Before Adjustment, Tax Benefit	$ (434.2)	$ (436.5)
Change in Adjustment to Deferred Acquisition Costs and Reserves for Future Policy and Contract Benefits, Net of Reinsurance, Tax Expense	331.8	380.8
Change in Net Gain on Hedges, Tax Expense (Benefit)	(5.4)	6.6
Change in Foreign Currency Translation Adjustment, Tax Expense	1.8	2.1
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax	$ 1.2	$ 1.9

CONSOLIDATED STATEMENTS OF STOC

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Millions	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Retained EarningsCumulative Effect, Period of Adoption, Adjustment	Retained EarningsCumulative Effect, Period of Adoption, Adjusted Balance	Treasury Stock
Balance at Beginning of Year at Dec. 31, 2019		$ 30.6	$ 2,348.1	$ 37.3	$ 10,728.7			$ (3,179.7)
Balance at Beginning of Year (Accounting Standards Update 2016-13) at Dec. 31, 2019						$ (18.9)	$ 10,709.8
Increase (Decrease) in Stockholders' Equity
Common Stock Activity			9.2
Other Comprehensive Loss	$ (254.4)			(254.4)
Net Income	161				161
Dividends to Stockholders (per common share: $0.285; $0.285)					(58.8)
Balance at End of Year at Mar. 31, 2020	9,803.1	30.6	2,357.3	(217.1)	10,812			(3,179.7)
Balance at Beginning of Year at Dec. 31, 2020	10,871	30.7	2,376.2	374.2	11,269.6			(3,179.7)
Balance at Beginning of Year (Accounting Standards Update 2016-13) at Dec. 31, 2020						$ 0	$ 11,269.6
Increase (Decrease) in Stockholders' Equity
Common Stock Activity			4.6
Other Comprehensive Loss	(399.1)			(399.1)
Net Income	153				153
Dividends to Stockholders (per common share: $0.285; $0.285)					(59.4)
Balance at End of Year at Mar. 31, 2021	$ 10,570.1	$ 30.7	$ 2,380.8	$ (24.9)	$ 11,363.2			$ (3,179.7)

CONSOLIDATED STATEMENTS OF ST_2

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Parenthetical) - $ / shares	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement of Stockholders' Equity [Abstract]
Dividends to Stockholders (per common share: $0.285; $0.285)	$ 0.285	$ 0.285

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash Flows from Operating Activities
Net Income	$ 153	$ 161
Adjustments to Reconcile Net Income to Net Cash Provided (Used) by Operating Activities
Change in Receivables	4.5	(8.7)
Change in Deferred Acquisition Costs	35.8	14.2
Change in Insurance Reserves and Liabilities	291.1	67.5
Change in Income Taxes	44.9	24.9
Change in Other Accrued Liabilities	(72.4)	(121.3)
Non-cash Components of Net Investment Income	(108)	(92.5)
Net Realized Investment (Gain) Loss	(84.6)	144
Depreciation	29.3	28.5
Cash Related to Reinsurance Agreement	(456.8)	0
Other, Net	1.2	2.3
Net Cash Provided (Used) by Operating Activities	(162)	219.9
Cash Flows from Investing Activities
Proceeds from Sales of Fixed Maturity Securities	157.4	120.7
Proceeds from Maturities of Fixed Maturity Securities	856.3	414.3
Proceeds from Sales and Maturities of Other Investments	68.2	48.5
Purchases of Fixed Maturity Securities	(1,185)	(780.5)
Purchases of Other Investments	(62.5)	(144.2)
Net Sales and Maturities of Short-term Investments	769	15.5
Net Increase in Payables for Collateral on Investments	16.1	487.4
Net Purchases of Property and Equipment	(30.9)	(39.1)
Net Cash Provided by Investing Activities	588.6	122.6
Cash Flows from Financing Activities
Long-term Debt Repayment	0	(15)
Issuance of Common Stock	0.8	1.3
Dividends Paid to Stockholders	(58.4)	(57.8)
Cash Received Related to Active Life Volatility Cover Agreement	17.9	0
Other, Net	(22.1)	(17.9)
Net Cash Used by Financing Activities	(61.8)	(89.4)
Net Increase in Cash and Bank Deposits	364.8	253.1
Cash and Bank Deposits at Beginning of Year	197	84.1
Cash and Bank Deposits at End of Period	$ 561.8	$ 337.2

Basis of Presentation

Basis of Presentation	3 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
Basis of Presentation	The accompanying consolidated financial statements of Unum Group and its subsidiaries (the Company) have been prepared in accordance with U.S. generally accepted accounting principles (GAAP) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. For further information, refer to the consolidated financial statements and footnotes included in our annual report on Form 10-K for the year ended December 31, 2020. In our opinion, all adjustments (consisting of normal recurring accruals) considered necessary for a fair presentation have been included. Interim results are not necessarily indicative of full year performance, particularly when considering the risks and uncertainties associated with the coronavirus disease 2019 (COVID-19) and the impacts it may have on our financial position, results of operations, liquidity and capital resources, and overall business operations.

Accounting Developments

Accounting Developments	3 Months Ended
	Mar. 31, 2021
Accounting Developments [Abstract]
Accounting Developments	Accounting Developments Accounting Updates Adopted in 2021: Accounting Standards Codification (ASC) Description Date of Adoption Effect on Financial Statements ASC 740 "Income Taxes" The amendments in this update simplified the accounting for income taxes by removing certain exceptions in the guidance related to the following: 1. losses in continuing operations when there is income in other items, 2. foreign subsidiaries becoming equity method investments and vice versa, and 3. year-to-date interim period losses exceeding anticipated loss for the year. The amendments also simplified the accounting for income taxes related to the following: 1. franchise taxes partially based on income, 2. step up in the tax basis of goodwill, 3. allocation of tax expense to entities not subject to tax, 4. enacted changes in tax law or rates in interim periods, and 5. employee stock ownership programs and investments in qualified affordable housing projects accounted for using the equity method. January 1, 2021 The adoption of this update did not have a material effect on our financial position or results of operations. Summary of Financial Statement Impacts of Accounting Updates Adopted in 2020: Effective January 1, 2020, we adopted an update under ASC 326 "Financial Instruments - Credit Losses" that amended the guidance on the impairment of financial instruments. The update added an impairment model known as the current expected credit loss model that is based on expected losses rather than incurred losses and will generally result in earlier recognition of allowances for losses. The current expected credit loss model applies to financial instruments such as mortgage loans, fixed maturity securities classified as held-to-maturity, and certain receivables. The update also modified the other-than-temporary impairment model used for available-for-sale fixed maturity securities such that credit losses are recognized as an allowance rather than as a reduction in the amortized cost of the security. The reversal of previously recognized credit losses on available-for-sale fixed maturity securities is allowed under specified circumstances. The guidance was applied using a modified retrospective approach through a cumulative-effect reduction to retained earnings of $18.9 million as of the beginning of the period of adoption. For available-for-sale fixed maturity securities, the update was applied prospectively. Other-than-temporary impairment losses recognized on available-for-sale fixed maturity securities prior to adoption of the update cannot be reversed.
Schedule of New Accounting Pronouncements	Accounting Updates Outstanding: ASC Description Date of Adoption Effect on Financial Statements ASC 848 "Reference Rate Reform" The amendments in this update provide optional guidance, for a limited period of time, to ease the potential burden in accounting for and recognizing the effects of reference rate reform on financial reporting. The guidance allows for various practical expedients and exceptions when applying GAAP to contracts, hedging relationships, and other transactions affected either by discontinued rates as a direct result of reference rate reform or a market-wide change in interest rates used for discounting, margining or contract price alignment, if certain criteria are met. Specifically, the guidance provides certain practical expedients for contract modifications, fair value hedges, and cash flow hedges, and also provides certain exceptions related to changes in the critical terms of a hedging relationship. The guidance also allows for a one-time election to sell or transfer debt securities that were both classified as held-to-maturity prior to January 1, 2020 and reference a rate affected by the reform. Adoption is permitted as of the beginning of the interim period that includes March 12, 2020 (the issuance date of the update), or any date thereafter, through December 31, 2022, at which point the guidance will sunset. We have not yet determined the impact on our financial position or results of operations if we elect to adopt this guidance. ASC 944 "Financial Services - Insurance" This update significantly amends the accounting and disclosure requirements for long-duration insurance contracts. These changes include a requirement to review, and if necessary, update cash flow assumptions used to measure the liability for future policy benefits for traditional and limited-payment contracts at least annually, with changes recognized in earnings. In addition, an entity will be required to update the discount rate assumption at each reporting date using a yield that is reflective of an upper-medium grade fixed-income instrument, with changes recognized in other comprehensive income. These changes result in the elimination of the provision for risk of adverse deviation and premium deficiency (or loss recognition) testing. The update also requires that an entity measure all market risk benefits associated with deposit contracts at fair value, with changes recognized in earnings except for the portion attributable to a change in the instrument-specific credit risk, which is to be recognized in other comprehensive income. This update also simplifies the amortization of deferred acquisition costs by requiring amortization on a constant level basis over the expected term of the related contracts. Deferred acquisition costs are required to be written off for unexpected contract terminations but are no longer subject to an impairment test. Significant additional disclosures will also be required, which include disaggregated rollforwards of certain liability balances and the disclosure of qualitative and quantitative information about expected cash flows, estimates, and assumptions. The application of this guidance will vary based upon the specific requirements of the update but will generally result in either a modified retrospective or full retrospective approach with changes applied as of the beginning of the earliest period presented. Early adoption is permitted. January 1, 2023 We are currently evaluating the impact of the update and expect that the adoption may have a material impact on our financial position and results of operations. The update will also significantly expand our disclosures.

Fair Values of Financial Instru

Fair Values of Financial Instruments	3 Months Ended
	Mar. 31, 2021
Fair Value Disclosures [Abstract]
Fair Values of Financial Instruments	Fair Value Measurements for Financial Instruments Carried at Fair Value We report fixed maturity securities, which are classified as available-for-sale securities, derivative financial instruments, and unrestricted equity securities at fair value in our consolidated balance sheets. We report our investments in private equity partnerships at our share of the partnerships' net asset value per share or its equivalent (NAV) as a practical expedient for fair value. The degree of judgment utilized in measuring the fair value of financial instruments generally correlates to the level of pricing observability. Financial instruments with readily available active quoted prices or for which fair value can be measured from actively quoted prices in active markets generally have more pricing observability and less judgment utilized in measuring fair value. An active market for a financial instrument is a market in which transactions for an asset or a similar asset occur with sufficient frequency and volume to provide pricing information on an ongoing basis. A quoted price in an active market provides the most reliable evidence of fair value and should be used to measure fair value whenever available. Conversely, financial instruments rarely traded or not quoted have less observability and are measured at fair value using valuation techniques that require more judgment. Pricing observability is generally impacted by a number of factors, including the type of financial instrument, whether the financial instrument is new to the market and not yet established, the characteristics specific to the transaction, and overall market conditions. We classify financial instruments in accordance with a fair value hierarchy consisting of three levels based on the observability of valuation inputs: • Level 1 - the highest category of the fair value hierarchy classification wherein inputs are unadjusted and represent quoted prices in active markets for identical assets or liabilities at the measurement date. • Level 2 - valued using inputs (other than prices included in Level 1) that are either directly or indirectly observable for the asset or liability through correlation with market data at the measurement date and for the duration of the instrument's anticipated life. • Level 3 - the lowest category of the fair value hierarchy and reflects the judgment of management regarding what market participants would use in pricing assets or liabilities at the measurement date. Financial assets and liabilities categorized as Level 3 are generally those that are valued using unobservable inputs to extrapolate an estimated fair value. Valuation Methodologies of Financial Instruments Measured at Fair Value Valuation techniques used for assets and liabilities accounted for at fair value are generally categorized into three types. The market approach uses prices and other relevant information from market transactions involving identical or comparable assets or liabilities. The income approach converts future amounts, such as cash flows or earnings, to a single present amount, or a discounted amount. The cost approach is based upon the amount that currently would be required to replace the service capacity of an asset, or the current replacement cost. We use valuation techniques that are appropriate in the circumstances and for which sufficient data are available that can be obtained without undue cost and effort. In some cases, a single valuation technique will be appropriate (for example, when valuing an asset or liability using quoted prices in an active market for identical assets or liabilities). In other cases, multiple valuation techniques will be appropriate. If we use multiple valuation techniques to measure fair value, we evaluate and weigh the results, as appropriate, considering the reasonableness of the range indicated by those results. A fair value measurement is the point within that range that is most representative of fair value in the circumstances. The selection of the valuation method(s) to apply considers the definition of an exit price and depends on the nature of the asset or liability being valued. For assets and liabilities accounted for at fair value, we generally use valuation techniques consistent with the market approach, and to a lesser extent, the income approach. We believe the market approach provides more observable data than the income approach, considering the type of investments we hold. Our fair value measurements could differ significantly based on the valuation technique and available inputs. When using a pricing service, we obtain the vendor's pricing documentation to ensure we understand their methodologies. We periodically review and approve the selection of our pricing vendors to ensure we are in agreement with their current methodologies. When markets are less active, brokers may rely more on models with inputs based on the information available only to the broker. Our internal investment management professionals, which include portfolio managers and analysts, monitor securities priced by brokers and evaluate their prices for reasonableness based on benchmarking to available primary and secondary market information. In weighing a broker quote as an input to fair value, we place less reliance on quotes that do not reflect the result of market transactions. We also consider the nature of the quote, particularly whether it is a bid or market quote. If prices in an inactive market do not reflect current prices for the same or similar assets, adjustments may be necessary to arrive at fair value. When relevant market data is unavailable, which may be the case during periods of market uncertainty, the income approach can, in suitable circumstances, provide a more appropriate fair value. During 2021, we have applied valuation approaches and techniques on a consistent basis to similar assets and liabilities and consistent with those approaches and techniques used at year end 2020. Fixed Maturity and Equity Securities We use observable and unobservable inputs in measuring the fair value of our fixed maturity and equity securities. For securities categorized as Level 1, fair values equal active Trade Reporting and Compliance Engine (TRACE) pricing or unadjusted broker market maker prices. For securities categorized as Level 2 or Level 3, inputs that may be used in valuing each class of securities at any given time period are disclosed below. Actual inputs used to determine fair values will vary for each reporting period depending on the availability of inputs which may, at times, be affected by the lack of market liquidity. Level 2 Level 3 Instrument Observable Inputs Unobservable Inputs United States Government and Government Agencies and Authorities Valuation Method Principally the market approach Not applicable Valuation Techniques / Inputs Prices obtained from external pricing services States, Municipalities, and Political Subdivisions Valuation Method Principally the market approach Principally the market approach Valuation Techniques / Inputs Prices obtained from external pricing services Analysis of similar bonds, adjusted for comparability Relevant reports issued by analysts and rating agencies Audited financial statements Foreign Governments Valuation Method Principally the market approach Principally the market approach Valuation Techniques / Inputs Prices obtained from external pricing services Analysis of similar bonds, adjusted for comparability Non-binding broker quotes Call provisions Public Utilities Valuation Method Principally the market and income approaches Principally the market and income approaches Valuation Techniques / Inputs Prices obtained from external pricing services Change in benchmark reference Level 2 Level 3 Instrument Observable Inputs Unobservable Inputs Public Utilities - Continued Non-binding broker quotes Analysis of similar bonds, adjusted for comparability Benchmark yields Discount for size - illiquidity Transactional data for new issuances and secondary trades Volatility of credit Security cash flows and structures Lack of marketability Recent issuance / supply Audited financial statements Security and issuer level spreads Security creditor ratings/maturity/capital structure/optionality Public covenants Comparative bond analysis Relevant reports issued by analysts and rating agencies Mortgage/Asset-Backed Securities Valuation Method Principally the market and income approaches Principally the market approach Valuation Techniques / Inputs Prices obtained from external pricing services Analysis of similar bonds, adjusted for comparability Non-binding broker quotes Prices obtained from external pricing services Security cash flows and structures Underlying collateral Prepayment speeds/loan performance/delinquencies Relevant reports issued by analysts and rating agencies Audited financial statements All Other Corporate Bonds Valuation Method Principally the market and income approaches Principally the market and income approaches Valuation Techniques / Inputs Prices obtained from external pricing services Change in benchmark reference Non-binding broker quotes Discount for size - illiquidity Benchmark yields Volatility of credit Transactional data for new issuances and secondary trades Lack of marketability Security cash flows and structures Prices obtained from external pricing services Recent issuance / supply Security and issuer level spreads Security creditor ratings/maturity/capital structure/optionality Level 2 Level 3 Instrument Observable Inputs Unobservable Inputs All Other Corporate Bonds - Continued Public covenants Comparative bond analysis Relevant reports issued by analysts and rating agencies Audited financial statements Redeemable Preferred Stocks Valuation Method Principally the market approach Principally the market approach Valuation Techniques / Inputs Non-binding broker quotes Financial statement analysis Benchmark yields Comparative bond analysis Call provisions Relevant reports issued by analysts and rating agencies Audited financial statements Perpetual Preferred and Equity Securities Valuation Method Principally the market approach Principally the market and income approaches Valuation Techniques / Inputs Prices obtained from external pricing services Financial statement analysis Non-binding broker quotes The management of our investment portfolio includes establishing pricing policy and reviewing the reasonableness of sources and inputs used in developing pricing. We review all prices that vary between multiple pricing vendors by a threshold that is outside a normal market range for the asset type. In the event we receive a vendor's market price that does not appear reasonable based on our market analysis, we may challenge the price and request further information about the assumptions and methodologies used by the vendor to price the security. We may change the vendor price based on a better data source such as an actual trade. We also review all prices that did not change from the prior month to ensure that these prices are within our expectations. The overall valuation process for determining fair values may include adjustments to valuations obtained from our pricing sources when they do not represent a valid exit price. These adjustments may be made when, in our judgment and considering our knowledge of the financial conditions and industry in which the issuer operates, certain features of the financial instrument require that an adjustment be made to the value originally obtained from our pricing sources. These features may include the complexity of the financial instrument, the market in which the financial instrument is traded, counterparty credit risk, credit structure, concentration, or liquidity. Additionally, an adjustment to the price derived from a model typically reflects our judgment of the inputs that other participants in the market for the financial instrument being measured at fair value would consider in pricing that same financial instrument. In the event an asset is sold, we test the validity of the fair value determined by our valuation techniques by comparing the selling price to the fair value determined for the asset in the immediately preceding month end reporting period. Certain of our investments do not have readily determinable market prices and/or observable inputs or may at times be affected by the lack of market liquidity. For these securities, we use internally prepared valuations, including valuations based on estimates of future profitability, to estimate the fair value. Additionally, we may obtain prices from independent third-party brokers to aid in establishing valuations for certain of these securities. Key assumptions used by us to determine fair value for these securities include risk free interest rates, risk premiums, performance of underlying collateral (if any), and other factors involving significant assumptions which may or may not reflect those of an active market. The parameters and inputs used to validate a price on a security may be adjusted for assumptions about risk and current market conditions on a quarter to quarter basis, as certain features may be more significant drivers of valuation at the time of pricing. Changes to inputs in valuations are not changes to valuation methodologies; rather, the inputs are modified to reflect direct or indirect impacts on asset classes from changes in market conditions. At March 31, 2021, approximately 23.5 percent of our fixed maturity securities were valued using active trades from TRACE pricing or broker market maker prices for which there was current market activity in that specific security (comparable to receiving one binding quote). The prices obtained were not adjusted, and the assets were classified as Level 1. The remaining 76.5 percent of our fixed maturity securities were valued based on non-binding quotes or other observable and unobservable inputs, as discussed below: • 60.5 percent of our fixed maturity securities were valued based on prices from pricing services that generally use observable inputs such as prices for securities or comparable securities in active markets in their valuation techniques. These assets were classified as Level 2. • 10.9 percent of our fixed maturity securities were valued based on one or more non-binding broker quotes, if validated by observable market data. When only one price is available, it is used if observable inputs and analysis confirms that it is appropriate. These assets, for which we were able to validate the price using other observable market data, were classified as Level 2. • 5.1 percent of our fixed maturity securities were valued based on prices of comparable securities, internal models, or pricing services or other non-binding quotes with no other observable market data. These assets were classified as either Level 2 or Level 3, with the categorization dependent on whether there was other observable market data. Derivatives Fair values for derivatives other than embedded derivatives in modified coinsurance arrangements are based on market quotes or pricing models and represent the net amount of cash we would have paid or received if the contracts had been settled or closed as of the last day of the period. We analyze credit default swap spreads relative to the average credit spread embedded within the London Interbank Offered Rate (LIBOR) setting syndicate in determining the effect of credit risk on our derivatives' fair values. If net counterparty credit risk for a derivative asset is determined to be material and is not adequately reflected in the LIBOR based fair value obtained from our pricing sources, we adjust the valuations obtained from our pricing sources. For purposes of valuing net counterparty risk, we measure the fair value of a group of financial assets and financial liabilities on the basis of the price that would be received to sell a net long position or transfer a net short position for a particular risk exposure in an orderly transaction between market participants at the measurement date under current market conditions. In regard to our own credit risk component, we adjust the valuation of derivative liabilities wherein the counterparty is exposed to our credit risk when the LIBOR based valuation of our derivatives obtained from pricing sources does not effectively include an adequate credit component for our own credit risk. Fair values for our embedded derivative in a modified coinsurance arrangement are estimated using internal pricing models and represent the hypothetical value of the duration mismatch of assets and liabilities, interest rate risk, and third party credit risk embedded in the modified coinsurance arrangement. We consider transactions in inactive markets to be less representative of fair value. We use all available observable inputs when measuring fair value, but when significant unobservable inputs are used, we classify these assets or liabilities as Level 3. Private Equity Partnerships Our private equity partnerships represent funds that are primarily invested in private credit, private equity, and real assets, as described below. Distributions received from the funds arise from income generated by the underlying investments as well as the liquidation of the underlying investments. There is generally not a public market for these investments. The following tables present additional information about our private equity partnerships, including commitments for additional investments which may or may not be funded: March 31, 2021 Investment Category Fair Value Redemption Term / Redemption Notice Unfunded Commitments (in millions of dollars) (in millions of dollars) Private Credit (a) $ 247.5 Not redeemable $ 190.3 41.9 Initial 2 year lock on each new investment / Quarterly after 2 year lock with 90 days notice 1.1 Total Private Credit 289.4 191.4 Private Equity (b) 249.8 Not redeemable 216.4 9.2 Initial 5.5 year lock on each new investment / Quarterly after 5.5 year lock with 90 days notice 34.3 Total Private Equity 259.0 250.7 Real Assets (c) 187.7 Not redeemable 198.9 56.3 Quarterly / 90 days notice — Total Real Assets 244.0 198.9 Total Partnerships $ 792.4 $ 641.0 December 31, 2020 Investment Category Fair Value Redemption Term / Redemption Notice Unfunded Commitments (in millions of dollars) (in millions of dollars) Private Credit (a) $ 233.3 Not redeemable $ 178.9 40.4 Initial 2 year lock on each new investment / Quarterly after 2 year lock with 90 days notice 1.3 Total Private Credit 273.7 180.2 Private Equity (b) 232.6 Not redeemable 191.0 9.2 Initial 5.5 year lock on each new investment / Quarterly after 5.5 year lock with 90 days notice 34.3 Total Private Equity 241.8 225.3 Real Assets (c) 176.3 Not redeemable 185.2 55.7 Quarterly / 90 days notice — Total Real Assets 232.0 185.2 Total Partnerships $ 747.5 $ 590.7 (a) Private Credit - The limited partnerships described in this category employ various investment strategies, generally providing direct lending or other forms of debt financing including first-lien, second-lien, mezzanine, and subordinated loans. The limited partnerships have credit exposure to corporates, physical assets, and/or financial assets within a variety of industries (including manufacturing, healthcare, energy, business services, technology, materials, and retail) in North America and, to a lesser extent, outside of North America. As of March 31, 2021, the estimated remaining life of the investments that do not allow for redemptions is approximately 34 percent in the next 3 years, 51 percent during the period from 3 to 5 years, 13 percent during the period from 5 to 10 years, and 2 percent during the period from 10 to 15 years. (b) Private Equity - The limited partnerships described in this category employ various strategies generally investing in controlling or minority control equity positions directly in companies and/or assets across various industries (including manufacturing, healthcare, energy, business services, technology, materials, and retail), primarily in private markets within North America and, to a lesser extent, outside of North America. As of March 31, 2021, the estimated remaining life of the investments that do not allow for redemptions is approximately 21 percent in the next 3 years, 34 percent during the period from 3 to 5 years, 44 percent during the period from 5 to 10 years, and 1 percent during the period from 10 to 15 years. (c) Real Assets - The limited partnerships described in this category employ various strategies, which include investing in the equity and/or debt financing of physical assets, including infrastructure (energy, power, water/wastewater, communications), transportation (including airports, ports, toll roads, aircraft, railcars) and real estate in North America, Europe, South America, and Asia. As of March 31, 2021, the estimated remaining life of the investments that do not allow for redemptions is approximately 11 percent in the next 3 years, 21 percent during period from 3 to 5 years and 68 percent during the period from 5 to 10 years. We record changes in our share of net asset value of the partnerships in net investment income. We receive financial information related to our investments in partnerships and generally record investment income on a one-quarter lag in accordance with our accounting policy. The following tables present information about financial instruments measured at fair value on a recurring basis by fair value level, based on the observability of the inputs used: March 31, 2021 Level 1 Level 2 Level 3 NAV Total (in millions of dollars) Assets Fixed Maturity Securities United States Government and Government Agencies and Authorities $ 101.1 $ 475.5 $ — $ — $ 576.6 States, Municipalities, and Political Subdivisions 54.1 4,149.8 — — 4,203.9 Foreign Governments — 1,098.9 21.7 — 1,120.6 Public Utilities 594.2 5,746.9 103.4 — 6,444.5 Mortgage/Asset-Backed Securities — 847.9 77.2 — 925.1 All Other Corporate Bonds 9,144.4 19,157.6 499.2 — 28,801.2 Redeemable Preferred Stocks — 4.1 — — 4.1 Total Fixed Maturity Securities 9,893.8 31,480.7 701.5 — 42,076.0 Other Long-term Investments Derivatives Forwards — 0.1 — — 0.1 Foreign Exchange Contracts — 17.4 — — 17.4 Credit Default Swaps — 0.1 — — 0.1 Total Derivatives — 17.6 — — 17.6 Perpetual Preferred Equity Securities 26.1 0.2 5.2 — 31.5 Private Equity Partnerships — — — 792.4 792.4 Total Other Long-term Investments 26.1 17.8 5.2 792.4 841.5 Total Financial Instrument Assets Carried at Fair Value $ 9,919.9 $ 31,498.5 $ 706.7 $ 792.4 $ 42,917.5 Liabilities Other Liabilities Derivatives Forwards $ — $ 0.1 $ — $ — $ 0.1 Foreign Exchange Contracts — 54.8 — — 54.8 Embedded Derivative in Modified Coinsurance Arrangement — — 22.9 — 22.9 Total Derivatives — 54.9 22.9 — 77.8 Total Financial Instrument Liabilities Carried at Fair Value $ — $ 54.9 $ 22.9 $ — $ 77.8 December 31, 2020 Level 1 Level 2 Level 3 NAV Total (in millions of dollars) Assets Fixed Maturity Securities United States Government and Government Agencies and Authorities $ — $ 709.8 $ — $ — $ 709.8 States, Municipalities, and Political Subdivisions — 4,245.7 15.5 — 4,261.2 Foreign Governments — 1,146.4 21.8 — 1,168.2 Public Utilities 131.9 6,644.7 185.7 — 6,962.3 Mortgage/Asset-Backed Securities — 1,026.4 81.3 — 1,107.7 All Other Corporate Bonds 4,089.4 24,886.1 943.1 — 29,918.6 Redeemable Preferred Stocks — 9.5 — — 9.5 Total Fixed Maturity Securities 4,221.3 38,668.6 1,247.4 — 44,137.3 Other Long-term Investments Derivatives Foreign Exchange Contracts — 19.7 — — 19.7 Credit Default Swaps — 0.1 — — 0.1 Total Derivatives — 19.8 — — 19.8 Perpetual Preferred Equity Securities 8.4 15.2 4.7 — 28.3 Private Equity Partnerships — — — 747.5 747.5 Total Other Long-term Investments 8.4 35.0 4.7 747.5 795.6 Total Financial Instrument Assets Carried at Fair Value $ 4,229.7 $ 38,703.6 $ 1,252.1 $ 747.5 $ 44,932.9 Liabilities Other Liabilities Derivatives Forwards $ — $ 0.5 $ — $ — $ 0.5 Foreign Exchange Contracts — 59.2 — — 59.2 Embedded Derivative in Modified Coinsurance Arrangement — — 39.8 — 39.8 Total Derivatives — 59.7 39.8 — 99.5 Total Financial Instrument Liabilities Carried at Fair Value $ — $ 59.7 $ 39.8 $ — $ 99.5 Changes in assets and liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3) are as follows: Three Months Ended March 31, 2021 Fair Value Beginning of Year Total Realized Level 3 Transfers Fair Value End of Period Change in Unrealized Gain (Loss) on Securities Held at the End of Period included in Earnings OCI (1) Purchases Sales Into Out of OCI Earnings (in millions of dollars) Fixed Maturity Securities States, Municipalities, and Political Subdivisions $ 15.5 $ — $ — $ — $ — $ — $ (15.5) $ — $ — $ — Foreign Governments 21.8 — (0.1) — — — — 21.7 (0.1) — Public Utilities 185.7 — (4.6) — — 36.0 (113.7) 103.4 (4.6) — Mortgage/Asset-Backed Securities 81.3 — (34.5) — (32.6) 86.1 (23.1) 77.2 (34.5) — All Other Corporate Bonds 943.1 — (13.8) — — — (430.1) 499.2 (13.8) — Total Fixed Maturity Securities 1,247.4 — (53.0) — (32.6) 122.1 (582.4) 701.5 (53.0) — Perpetual Preferred Equity Securities 4.7 — — — — 0.5 — 5.2 — — Embedded Derivative in Modified Coinsurance Arrangement (39.8) 16.9 — — — — — (22.9) — 16.9 (1) Other Comprehensive Income (Loss) Three Months Ended March 31, 2020 Fair Value Beginning of Year Total Realized Level 3 Transfers Fair Value End of Period Change in Unrealized Gain (Loss) on Securities Held at the End of Period included in Earnings OCI Purchases Sales Into Out of OCI Earnings (in millions of dollars) Fixed Maturity Securities States, Municipalities, and Political Subdivisions $ 41.8 $ — $ 2.8 $ — $ — $ — $ (13.3) $ 31.3 $ 2.9 $ — Foreign Governments 21.8 — (0.9) — — — — 20.9 (0.9) — Public Utilities 14.6 — (0.3) — — 18.0 (6.0) 26.3 — — Mortgage/Asset-Backed Securities 34.1 — (0.8) — — 49.2 (7.4) 75.1 (0.2) — All Other Corporate Bonds 600.5 — (50.6) 20.9 — 236.2 (254.0) 553.0 (2.2) — Total Fixed Maturity Securities 712.8 — (49.8) 20.9 — 303.4 (280.7) 706.6 (0.4) — Perpetual Preferred Equity Securities 4.6 — — — — — — 4.6 — — Embedded Derivative in Modified Coinsurance Arrangement (22.8) (86.9) — — — — — (109.7) — (86.9) Realized and unrealized investment gains and losses presented in the preceding tables represent gains and losses only for the time during which the applicable financial instruments were classified as Level 3. The transfers between levels resulted primarily from a change in observability of three inputs used to determine fair values of the securities transferred: (1) transactional data for new issuance and secondary trades, (2) broker/dealer quotes and pricing, primarily related to changes in the level of activity in the market and whether the market was considered orderly, and (3) comparable bond metrics from which to perform an analysis. For fair value measurements of financial instruments that were transferred either into or out of Level 3, we reflect the transfers using the fair value at the beginning of the period. We believe this allows for greater transparency, as all changes in fair value that arise during the reporting period of the transfer are disclosed as a component of our Level 3 reconciliation. The table below provides quantitative information regarding the significant unobservable inputs used in Level 3 fair value measurements derived from internal models. Unobservable inputs for fixed maturity securities are weighted by the fair value of the securities. Certain securities classified as Level 3 are excluded from the table below due to limitations in our ability to obtain the underlying inputs used by external pricing sources. March 31, 2021 Fair Value Valuation Method Unobservable Input Range/Weighted Average (in millions of dollars) Fixed Maturity Securities All Other Corporate Bonds - Private $ 45.0 Market Approach Volatility of Credit (a) 0.50% - 47.79% / 6.58% Perpetual Preferred Equity Securities 5.2 Market Approach Market Convention (b) Priced at Cost or Owner's Equity Embedded Derivative in Modified Coinsurance Arrangement (22.9) Discounted Cash Flows Projected Liability Cash Flows Weighted Spread of Swap Curve (c) Actuarial Assumptions 0.7% December 31, 2020 Fair Value Valuation Method Unobservable Input Range/Weighted Average (in millions of dollars) Fixed Maturity Securities All Other Corporate Bonds - Private $ 45.7 Market Approach Volatility of Credit (a) 0.50% - 24.90% / 3.63% Perpetual Preferred Equity Securities 4.7 Market Approach Market Convention (b) Priced at Cost or Owner's Equity Embedded Derivative in Modified Coinsurance Arrangement (39.8) Discounted Cash Flows Projected Liability Cash Flows Weighted Spread of Swap Curve (c) Actuarial Assumptions 1.0% (a) Represents basis point adjustments for credit-specific factors (b) Represents a decision to price based on par value, cost, or owner's equity when limited data is available (c) Represents various actuarial assumptions required to derive the liability cash flows. Fair value of embedded derivative is most often driven by the change in the weighted average credit spread to the swap curve for the assets backing the hypothetical loan. Isolated increases in unobservable inputs other than market convention will result in a lower fair value measurement, whereas isolated decreases will result in a higher fair value measurement. The unobservable input for market convention is not sensitive to input movements. The projected liability cash flows used in the fair value measurement of our Level 3 embedded derivative are based on expected claim payments. If claim payments increase, the projected liability cash flows will increase, resulting in a decrease in the fair value of the embedded derivative. Decreases in projected liability cash flows will result in an increase in the fair value of the embedded derivative. Fair Value Measurements for Financial Instruments Not Carried at Fair Value The methods and assumptions used to estimate fair values of financial instruments not carried at fair value are discussed as follows: Mortgage Loans: Fair value of newly originated, seasoned performing, or sub-performing but likely to continue cash flowing loans are calculated using a discounted cash flow analysis. Loans’ cash flows are modeled and appropriately discounted by a rate based on current yields and credit spreads. For sub and non-performing loans where there is some probability the loan will not continue to pay, a price based approach would be used to estimate the loan’s value in the open market utilizing current transaction information from similar loans. Policy Loans: Fair values for policy loans, net of reinsurance ceded, are estimated using discounted cash flow analyses and interest rates currently being offered to policyholders with similar policies. Carrying amounts for ceded policy loans, which equal $3,337.3 million and $3,390.6 million as of March 31, 2021 and December 31, 2020, respectively, approximate fair value and are reported on a gross basis in our consolidated balance sheets. A change in interest rates for ceded policy loans will not impact our financial position because the benefits and risks are fully ceded to reinsuring counterparties. Miscellaneous Long-term Investments: Carrying amounts for tax credit partnerships equal the unamortized balance of our contractual commitments and approximate fair value. Our shares of FHLB common stock are carried at cost, which approximates fair value. Long-term Debt: Fair values for long-term debt are obtained from independent pricing services or discounted cash flow analyses based on current incremental borrowing rates for similar types of borrowing arrangements. Federal Home Loan Bank (FHLB) Funding Agreements: Funding agreements with the FHLB represent cash advances used for the purpose of investing in fixed maturity securities. Carrying amounts approximate fair value. Unfunded Commitments to Investment Partnerships: Unfunded equity commitments represent amounts that we have committed to fund certain investment partnerships. These commitments are legally binding, subject to the partnerships meeting specified conditions. Carrying amounts of these financial instruments approximate fair value. The following table presents the carrying amounts and estimated fair values of our financial instruments not measured at fair value and indicates the level in the fair value hierarchy of the estimated fair value measurement based on the observability of the inputs used: March 31, 2021 Estimated Fair Value Level 1 Level 2 Level 3 Total Carrying Value (in millions of dollars) Assets Mortgage Loans $ — $	[1]
[1]	Real Assets - The limited partnerships described in this category employ various strategies, which include investing in the equity and/or debt financing of physical assets, including infrastructure (energy, power, water/wastewater, communications), transportation (including airports, ports, toll roads, aircraft, railcars) and real estate in North America, Europe, South America, and Asia. As of March 31, 2021, the estimated remaining life of the investments that do not allow for redemptions is approximately 11 percent in the next 3 years, 21 percent during period from 3 to 5 years and 68 percent during the period from 5 to 10 years.

Investments

Investments	3 Months Ended
	Mar. 31, 2021
Investments, Debt and Equity Securities [Abstract]
Investments	65% <= 75% 986.5 41.1 1,000.3 41.1 > 75% <= 85% 156.1 6.5 155.8 6.4 > 85% 79.2 3.3 86.6 3.6 Total $ 2,402.2 100.0 % $ 2,432.1 100.0 % The followin g table presents the amortized cost of our mortgage loans by year of origination and credit quality indicators at March 31, 2021 : Prior to 2017 2017 2018 2019 2020 2021 Total (in millions of dollars) Internal Rating AA $ 3.4 $ — $ — $ — $ — $ — $ 3.4 A 376.2 60.3 63.8 16.7 17.9 — 534.9 BBB 705.0 241.0 326.3 350.2 165.7 31.6 1,819.8 BB 29.2 10.4 — — — — 39.6 B 16.0 — — — — — 16.0 Total Amortized Cost 1,129.8 311.7 390.1 366.9 183.6 31.6 2,413.7 Allowance for credit losses (3.9) (1.6) (2.1) (2.4) (1.4) (0.1) (11.5) Carrying Amount $ 1,125.9 $ 310.1 $ 388.0 $ 364.5 $ 182.2 $ 31.5 $ 2,402.2 Loan-to-Value Ratio <=65% $ 821.9 $ 131.2 $ 90.6 $ 82.3 $ 37.2 $ 20.2 $ 1,183.4 >65<=75% 161.1 109.2 280.1 284.6 146.4 11.4 992.8 >75%<=85% 106.4 37.6 13.3 — — — 157.3 >85% 40.4 33.7 6.1 — — — 80.2 Total Amortized Cost 1,129.8 311.7 390.1 366.9 183.6 31.6 2,413.7 Allowance for credit losses (3.9) (1.6) (2.1) (2.4) (1.4) (0.1) (11.5) Carrying Amount $ 1,125.9 $ 310.1 $ 388.0 $ 364.5 $ 182.2 $ 31.5 $ 2,402.2 The following table presents a roll-forward of allowance for expected credit losses by loan-to-value ratio: Three Months Ended March 31, 2021 Beginning of Year Current Period Provisions Write-Offs Recoveries End of Period (in millions of dollars) Loan-to-Value Ratio <=65% $ 3.4 $ (0.4) $ — $ — $ 3.0 >65<=75% 7.3 (1.0) — — 6.3 >75%<=85% 1.3 (0.1) — — 1.2 >85% 1.1 (0.1) — — 1.0 Total $ 13.1 $ (1.6) $ — $ — $ 11.5 Three Months Ended March 31, 2020 Beginning of Year Current Period Provisions Write-Offs Recoveries End of Period (in millions of dollars) Loan-to-Value Ratio <=65% $ 2.8 $ 0.7 $ — $ — $ 3.5 >65<=75% 4.6 1.9 — — 6.5 >75%<=85% 0.5 (0.1) — — 0.4 >85% 0.4 0.3 — — 0.7 Total $ 8.3 $ 2.8 $ — $ — $ 11.1 The decrease in our estimate of expected losses during the first quarter of 2021 is primarily due to improved economic conditions and recovery from COVID-19, specifically as it relates to underlying commercial real estate values. There were no troubled debt restructurings during the three months ended March 31, 2021 and 2020. At March 31, 2021 and December 31, 2020, we held no mortgage loans that were greater than 90 days past due regarding principal and/or interest payments. We had no loan foreclosures for the three months ended March 31, 2021 and 2020. We had no impaired mortgage loans during three months ended March 31, 2021, or 2020, nor did we recognize any interest income on mortgage loans subsequent to impairment. At March 31, 2021, we had commitments of $18.0 million to fund certain commercial mortgage loans. Consistent with how we determine the estimate of current expected credit losses for our funded mortgage loans each period, we estimate expected credit losses for loans that have not been funded but we are committed to fund at the end of each period. At March 31, 2021 and December 31, 2020, we had a de minimis amount and $0.1 million, respectively, of expected credit losses related to unfunded commitments on our consolidated balance sheets. Transfers of Financial Assets To manage our cash position more efficiently, we may enter into repurchase agreements with unaffiliated financial institutions. We generally use repurchase agreements as a means to finance the purchase of invested assets or for short-term general business purposes until projected cash flows become available from our operations or existing investments. Our repurchase agreements are typically outstanding for less than 30 days. We post collateral through our repurchase agreement transactions whereby the counterparty commits to purchase securities with the agreement to resell them to us at a later, specified date. The fair value of collateral posted is generally 102 percent of the cash received. Our investment policy also permits us to lend fixed maturity securities to unaffiliated financial institutions in short-term securities lending agreements. These agreements increase our investment income with minimal risk. Our securities lending policy requires that a minimum of 102 percent of the fair value of the securities loaned be maintained as collateral. We may receive cash and/or securities as collateral under these agreements. Cash received as collateral is typically reinvested in short-term investments. If securities are received as collateral, we are not permitted to sell or re-post them. As of March 31, 2021, the carrying amount of fixed maturity securities loaned to third parties under our securities lending program was $220.0 million, for which we received collateral in the form of cash and securities of $43.5 million and $186.4 million, respectively. As of December 31, 2020, the carrying amount of fixed maturity securities loaned to third parties under our securities lending program was $96.6 million, for which we received collateral in the form of cash and securities of $17.6 million and $82.8 million, respectively. We had no outstanding repurchase agreements at March 31, 2021 or December 31, 2020. The remaining contractual maturities of our securities lending agreements disaggregated by class of collateral pledged are as follows: March 31, 2021 December 31, 2020 Overnight and Continuous (in millions of dollars) Borrowings United States Government and Government Agencies and Authorities $ 0.1 $ 0.1 State, Municipalities, and Political Subdivisions 0.4 0.4 Public Utilities 0.5 0.3 All Other Corporate Bonds 42.5 16.8 Total Borrowings $ 43.5 $ 17.6 Gross Amount of Recognized Liability for Securities Lending Transactions 43.5 17.6 Amounts Related to Agreements Not Included in Offsetting Disclosure Contained Herein $ — $ — Certain of our U.S. insurance subsidiaries are members of regional FHLBs. Membership, which requires that we purchase a minimum amount of FHLB common stock on which we receive dividends, provides access to low-cost funding. Advances received from the FHLB are used for the purchase of short-term investments or fixed maturity securities. Additional common stock purchases may be required, based on the amount of funds we borrow from the FHLBs. The carrying value of common stock owned, collateral posted, and advances received are as follows: March 31, 2021 December 31, 2020 (in millions of dollars) Carrying Value of FHLB Common Stock $ 26.9 $ 28.2 Advances from FHLB $ 302.2 $ 312.2 Carrying Value of Collateral Posted to FHLB Fixed Maturity Securities $ 857.9 $ 944.0 Commercial Mortgage Loans 982.1 1,072.5 Total Carrying Value of Collateral Posted to FHLB $ 1,840.0 $ 2,016.5 Offsetting of Financial Instruments We enter into master netting agreements with each of our derivatives counterparties. These agreements provide for conditional rights of set-off upon the occurrence of an early termination event. An early termination event is considered a default, and it allows the non-defaulting party to offset its contracts in a loss position against any gain positions or payments due to the defaulting party. Under our agreements, default type events are defined as failure to pay or deliver as contractually agreed, misrepresentation, bankruptcy, or merger without assumption. See Note 5 for further discussion of collateral related to our derivative contracts. We have securities lending agreements with unaffiliated financial institutions that post collateral to us in return for the use of our fixed maturity securities. A right of set-off exists that allows us to keep and apply collateral received in the event of default by the counterparty. Default within a securities lending agreement would typically occur if the counterparty failed to return the securities borrowed from us as contractually agreed. In addition, if we default by not returning collateral received, the counterparty has a right of set-off against our securities or any other amounts due to us. Shown below are our financial instruments that either meet the accounting requirements that allow them to be offset in our balance sheets or that are subject to an enforceable master netting arrangement or similar agreement. Our accounting policy is to not offset these financial instruments in our balance sheets. Net amounts disclosed below have been reduced by the amount of collateral pledged to or received from our counterparties. March 31, 2021 Gross Amount Gross Amount Not of Recognized Gross Amount Net Amount Offset in Balance Sheet Financial Offset in Presented in Financial Cash Net Instruments Balance Sheet Balance Sheet Instruments Collateral Amount (in millions of dollars) Financial Assets: Derivatives $ 17.6 $ — $ 17.6 $ (9.9) $ (7.7) $ — Securities Lending 220.0 — 220.0 (176.5) (43.5) — Total $ 237.6 $ — $ 237.6 $ (186.4) $ (51.2) $ — Financial Liabilities: Derivatives $ 54.9 $ — $ 54.9 $ (54.6) $ — $ 0.3 Securities Lending 43.5 — 43.5 (43.5) — — Total $ 98.4 $ — $ 98.4 $ (98.1) $ — $ 0.3 December 31, 2020 Gross Amount Gross Amount Not of Recognized Gross Amount Net Amount Offset in Balance Sheet Financial Offset in Presented in Financial Cash Net Instruments Balance Sheet Balance Sheet Instruments Collateral Amount (in millions of dollars) Financial Assets: Derivatives $ 19.8 $ — $ 19.8 $ (10.1) $ (8.7) $ 1.0 Securities Lending 96.6 — 96.6 (79.0) (17.6) — Total $ 116.4 $ — $ 116.4 $ (89.1) $ (26.3) $ 1.0 Financial Liabilities: Derivatives $ 59.7 $ — $ 59.7 $ (59.0) $ — $ 0.7 Securities Lending 17.6 — 17.6 (17.6) — — Total $ 77.3 $ — $ 77.3 $ (76.6) $ — $ 0.7 Net Investment Income Net investment income reported in our consolidated statements of income is presented below. Three Months Ended March 31 2021 2020 (in millions of dollars) Fixed Maturity Securities $ 469.8 $ 539.8 Derivatives 16.2 20.2 Mortgage Loans 26.3 29.0 Policy Loans 4.8 4.8 Other Long-term Investments Perpetual Preferred Securities 1 3.6 (17.1) Private Equity Partnerships 2 35.9 10.4 Other 2.1 3.2 Short-term Investments 0.6 6.4 Gross Investment Income 559.3 596.7 Less Investment Expenses 7.5 8.5 Less Investment Income on Participation Fund Account Assets 3.1 3.2 Net Investment Income $ 548.7 $ 585.0 1 The net unrealized gain (loss) recognized in net investment income for the three months ended March 31, 2021 related to perpetual preferred securities still held at March 31, 2021 was $2.7 million. The net unrealized loss recognized in net investment income for the three months ended March 31, 2020 related to perpetual preferred securities still held at March 31, 2020 was $17.9 million. 2 The net unrealized gain recognized in net investment income for the three months ended March 31, 2021 related to private equity partnerships still held at March 31, 2021 was $27.0 million. The net unrealized gain recognized in net investment income for the three months ended March 31, 2020 related to private equity partnerships still held at March 31, 2020 was $5.4 million. See Note 3 for further discussion of private equity partnerships. Realized Investment Gain and Loss Realized investment gains and losses are as follows: Three Months Ended March 31 2021 2020 (in millions of dollars) Fixed Maturity Securities Gross Gains on Sales 1 $ 71.3 $ 1.4 Gross Losses on Sales (1.1) (0.7) Credit Losses (8.3) (53.9) Mortgage Loans and Other Invested Assets Gross Gains on Sales 2.5 0.3 Gross Losses on Sales — (0.2) Credit Losses 1.7 (2.6) Embedded Derivative in Modified Coinsurance Arrangement 16.9 (86.9) All Other Derivatives 1.7 (0.7) Foreign Currency Transactions (0.1) (0.7) Net Realized Investment Gain (Loss) $ 84.6 $ (144.0) 1 Gross gains on sales of fixed maturity securities includes gains of $67.6 million as a result of the second phase of the reinsurance transaction that we completed during the first quarter of 2021. See Note 12 for further discussion." id="sjs-B4">Fixed Maturity Securities At March 31, 2021 and December 31, 2020, all fixed maturity securities were classified as available-for-sale. The amortized cost and fair values of securities by security type are shown as follows: March 31, 2021 Amortized ACL (1) Gross Gross Fair (in millions of dollars) United States Government and Government Agencies and Authorities $ 464.6 $ — $ 112.1 $ 0.1 $ 576.6 States, Municipalities, and Political Subdivisions 3,735.9 — 506.7 38.7 4,203.9 Foreign Governments 899.0 — 224.3 2.7 1,120.6 Public Utilities 5,390.6 — 1,080.0 26.1 6,444.5 Mortgage/Asset-Backed Securities 851.6 — 73.6 0.1 925.1 All Other Corporate Bonds 25,220.2 7.3 3,698.3 110.0 28,801.2 Redeemable Preferred Stocks 4.0 — 0.1 — 4.1 Total Fixed Maturity Securities $ 36,565.9 $ 7.3 $ 5,695.1 $ 177.7 $ 42,076.0 December 31, 2020 Amortized ACL (1) Gross Gross Fair (in millions of dollars) United States Government and Government Agencies and Authorities $ 559.0 $ — $ 150.8 $ — $ 709.8 States, Municipalities, and Political Subdivisions 3,609.9 — 652.8 1.5 4,261.2 Foreign Governments 902.9 — 266.5 1.2 1,168.2 Public Utilities 5,486.4 — 1,481.9 6.0 6,962.3 Mortgage/Asset-Backed Securities 1,019.9 — 88.0 0.2 1,107.7 All Other Corporate Bonds 24,958.8 6.8 5,013.5 46.9 29,918.6 Redeemable Preferred Stocks 9.6 — — 0.1 9.5 Total Fixed Maturity Securities $ 36,546.5 $ 6.8 $ 7,653.5 $ 55.9 $ 44,137.3 (1) Allowance for Credit Losses The following charts indicate the length of time our fixed maturity securities have been in a gross unrealized loss position. March 31, 2021 Less Than 12 Months 12 Months or Greater Fair Gross Fair Gross (in millions of dollars) United States Government and Government Agencies and Authorities $ 5.9 $ 0.1 $ — $ — States, Municipalities, and Political Subdivisions 888.1 38.7 0.6 — Foreign Governments 61.8 2.7 — — Public Utilities 321.4 22.8 38.6 3.3 Mortgage/Asset-Backed Securities 0.6 0.1 3.1 — All Other Corporate Bonds 1,883.4 84.0 246.0 26.0 Total Fixed Maturity Securities $ 3,161.2 $ 148.4 $ 288.3 $ 29.3 December 31, 2020 Less Than 12 Months 12 Months or Greater Fair Gross Fair Gross (in millions of dollars) States, Municipalities, and Political Subdivisions $ 133.4 $ 1.5 $ 0.1 $ — Foreign Governments 20.3 1.2 — — Public Utilities 76.3 3.7 25.4 2.3 Mortgage/Asset-Backed Securities 3.0 0.1 3.1 0.1 All Other Corporate Bonds 520.4 22.4 113.5 24.5 Redeemable Preferred Stocks 9.5 0.1 — — Total Fixed Maturity Securities $ 762.9 $ 29.0 $ 142.1 $ 26.9 The following is a distribution of the maturity dates for fixed maturity securities. The maturity dates have not been adjusted for possible calls or prepayments. March 31, 2021 Amortized Cost, Net of ACL Unrealized Gain Position Unrealized Loss Position Gross Gain Fair Value Gross Loss Fair Value (in millions of dollars) 1 year or less $ 777.5 $ 16.7 $ 731.2 $ 1.6 $ 61.4 Over 1 year through 5 years 6,304.4 581.8 6,672.8 16.2 197.2 Over 5 years through 10 years 10,695.5 1,531.9 11,529.8 23.1 674.5 Over 10 years 17,929.6 3,491.1 18,771.3 136.7 2,512.7 35,707.0 5,621.5 37,705.1 177.6 3,445.8 Mortgage/Asset-Backed Securities 851.6 73.6 921.4 0.1 3.7 Total Fixed Maturity Securities $ 36,558.6 $ 5,695.1 $ 38,626.5 $ 177.7 $ 3,449.5 December 31, 2020 Amortized Cost, Net of ACL Unrealized Gain Position Unrealized Loss Position Gross Gain Fair Value Gross Loss Fair Value (in millions of dollars) 1 year or less $ 881.8 $ 19.5 $ 836.4 $ 2.9 $ 62.0 Over 1 year through 5 years 6,162.6 589.9 6,545.7 22.9 183.9 Over 5 years through 10 years 10,886.9 1,914.8 12,659.4 10.7 131.6 Over 10 years 17,588.5 5,041.3 22,089.2 19.2 521.4 35,519.8 7,565.5 42,130.7 55.7 898.9 Mortgage/Asset-Backed Securities 1,019.9 88.0 1,101.6 0.2 6.1 Total Fixed Maturity Securities $ 36,539.7 $ 7,653.5 $ 43,232.3 $ 55.9 $ 905.0 The following chart depicts an analysis of our fixed maturity security portfolio between investment-grade and below-investment-grade categories as of March 31, 2021: Gross Unrealized Loss Fair Value Gross Unrealized Gain Amount Percent of Total Gross Unrealized Loss (in millions of dollars) Investment-Grade $ 38,846.3 $ 5,451.1 $ 149.9 84.4 % Below-Investment-Grade 3,229.7 244.0 27.8 15.6 Total Fixed Maturity Securities $ 42,076.0 $ 5,695.1 $ 177.7 100.0 % The unrealized losses on investment-grade fixed maturity securities principally relate to changes in interest rates or changes in market or sector credit spreads which occurred subsequent to the acquisition of the securities. Below-investment-grade fixed maturity securities are generally more likely to develop credit concerns than investment-grade securities. At March 31, 2021, the unrealized losses in our below-investment-grade fixed maturity securities were generally due to credit spreads in certain industries or sectors and, to a lesser extent, credit concerns related to specific securities. For each specific security in an unrealized loss position, we believe that there are positive factors which mitigate credit concerns and that the securities for which we have not recorded a credit loss will recover in value. We have the ability and intent to continue to hold these securities to recovery of amortized cost and believe that no credit losses have occurred. As of March 31, 2021, we held 239 individual investment-grade fixed maturity securities and 21 individual below-investment-grade fixed maturity securities that were in an unrealized loss position, of which 11 investment-grade fixed maturity securities and 12 below-investment-grade fixed maturity securities had been in an unrealized loss position continuously for over one year. In determining when a decline in fair value below amortized cost of a fixed maturity security represents a credit loss, we evaluate the following factors: • Whether we expect to recover the entire amortized cost basis of the security • Whether we intend to sell the security or will be required to sell the security before the recovery of its amortized cost basis • Whether the security is current as to principal and interest payments • The significance of the decline in value • Current and future business prospects and trends of earnings • The valuation of the security's underlying collateral • Relevant industry conditions and trends relative to their historical cycles • Market conditions • Rating agency and governmental actions • Bid and offering prices and the level of trading activity • Adverse changes in estimated cash flows for securitized investments • Changes in fair value subsequent to the balance sheet date • Any other key measures for the related security While determining whether a credit loss exists is a judgmental area, we utilize a formal, well-defined, and disciplined process to monitor and evaluate our fixed income investment portfolio, supported by issuer specific research and documentation as of the end of each period. The process results in a thorough evaluation of problem investments and the recording of credit losses on a timely basis for investments determined to have a credit loss. We calculate the allowance for credit losses of fixed maturity securities based on the present value of our best estimate of cash flows expected to be collected, discounted using the effective interest rate implicit in the security at the date of acquisition. When estimating future cash flows, we analyze the strength of the issuer’s balance sheet, its debt obligations and near-term funding arrangements, cash flow and liquidity, the profitability of its core businesses, the availability of marketable assets which could be sold to increase liquidity, its industry fundamentals and regulatory environment, and its access to capital markets. As of March 31, 2021, with respect to the fixed maturity securities for which the allowance for credit losses was recognized, we do not intend to sell these securities, and it is not more likely than not that we will be required to sell these securities before recovery of our estimated value. The following table presents a rollforward of the allowance for credit losses on available-for-sale fixed maturity securities, all of which are classified as "all other corporate bonds" in the preceding tables, at March 31, 2021: Three Months Ended March 31 2021 2020 (in millions of dollars) Balance, beginning of period $ 6.8 $ — Credit losses on securities for which credit losses were not previously recorded — 48.0 Change in allowance on securities with allowance recorded in previous period 0.5 — Balance, end of period $ 7.3 $ 48.0 At March 31, 2021, we had commitments of $106.5 million to fund private placement fixed maturity securities, the amount of which may or may not be funded. Variable Interest Entities We invest in variable interests issued by variable interest entities. These investments include tax credit partnerships, private equity partnerships, and special purpose entities. For those variable interests that are not consolidated in our financial statements, we are not the primary beneficiary because we have neither the power to direct the activities that are most significant to economic performance nor the responsibility to absorb a majority of the expected losses. The determination of whether we are the primary beneficiary is performed at the time of our initial investment and at the date of each subsequent reporting period. As of March 31, 2021, the carrying amount of our variable interest entity investments that are not consolidated in our financial statements was $816.8 million, comprised of $24.4 million of tax credit partnerships and $792.4 million of private equity partnerships. At December 31, 2020, the carrying amount of our variable interest entity investments that are not consolidated in our financial statements was $776.8 million, comprised of $29.3 million of tax credit partnerships and $747.5 million of private equity partnerships. These variable interest entity investments are reported as other long-term investments in our consolidated balance sheets. The Company invests in tax credit partnerships primarily for the receipt of income tax credits and tax benefits derived from passive losses on the investments. Amounts recognized in the consolidated statements of income are as follows: Three Months Ended March 31 2021 2020 (in millions of dollars) Income Tax Credits $ 5.4 $ 8.3 Amortization, Net of Tax (3.7) (5.5) Income Tax Benefit $ 1.7 $ 2.8 Contractually, we are a limited partner in these tax credit partnerships, and our maximum exposure to loss is limited to the carrying value of our investment, which includes $0.9 million of unfunded unconditional commitments at March 31, 2021. See Note 3 for commitments to fund private equity partnerships. Mortgage Loans Our mortgage loan portfolio is well diversified by both geographic region and property type to reduce risk of concentration. All of our mortgage loans are collateralized by commercial real estate. When issuing a new loan, our general policy is not to exceed a loan-to-value ratio, or the ratio of the loan balance to the estimated fair value of the underlying collateral, of 75 percent. We update the loan-to-value ratios at least every three years for each loan, and properties undergo a general inspection at least every two years. Our general policy for newly issued loans is to have a debt service coverage ratio greater than 1.25 times on a normalized 25 year amortization period. We update our debt service coverage ratios annually. We carry our mortgage loans at amortized cost less an allowance for expected credit losses. The amortized cost of our mortgage loans was $2,413.7 million and $2,445.2 million at March 31, 2021 and December 31, 2020, respectively. The allowance for expected credit losses was $11.5 million and $13.1 million at March 31, 2021 and December 31, 2020, respectively. Interest income is accrued on the principal amount of the loan based on the loan's contractual interest rate. We report accrued interest income for our mortgage loans as accrued investment income on our consolidated balance sheets, and the amount of the accrued income was $8.0 million at March 31, 2021 and December 31, 2020. The carrying amount of mortgage loans by property type and geographic region are presented below. March 31, 2021 December 31, 2020 (in millions of dollars) Carrying Amount Percent of Total Carrying Amount Percent of Total Property Type Apartment $ 648.2 27.0 % $ 638.0 26.2 % Industrial 650.6 27.1 654.0 26.9 Office 490.8 20.4 517.8 21.3 Retail 566.1 23.6 575.6 23.7 Other 46.5 1.9 46.7 1.9 Total $ 2,402.2 100.0 % $ 2,432.1 100.0 % Region New England $ 35.1 1.5 % $ 40.0 1.6 % Mid-Atlantic 200.6 8.4 202.5 8.2 East North Central 310.4 12.9 330.4 13.6 West North Central 194.3 8.1 196.1 8.1 South Atlantic 510.4 21.2 512.0 21.1 East South Central 109.1 4.5 110.0 4.5 West South Central 255.3 10.6 257.4 10.6 Mountain 276.3 11.5 268.8 11.1 Pacific 510.7 21.3 514.9 21.2 Total $ 2,402.2 100.0 % $ 2,432.1 100.0 % The risk in our mortgage loan portfolio is primarily related to vacancy rates. Events or developments, such as economic conditions that impact the ability of the borrowers to ensure occupancy of the property, may have a negative effect on our mortgage loan portfolio, particularly to the extent that our portfolio is concentrated in an affected region or property type. An increase in vacancies increases the probability of default, which would negatively affect our expected losses in our mortgage loan portfolio. We evaluate each of our mortgage loans individually for impairment and assign an internal credit quality rating based on a comprehensive rating system used to evaluate the credit risk of the loan. The factors we use to derive our internal credit ratings may include the following: • Loan-to-value ratio • Debt service coverage ratio based on current operating income • Property location, including regional economics, trends and demographics • Age, condition, and construction quality of property • Current and historical occupancy of property • Lease terms relative to market • Tenant size and financial strength • Borrower's financial strength • Borrower's equity in transaction • Additional collateral, if any Although all available and applicable factors are considered in our analysis, loan-to-value and debt service coverage ratios are the most critical factors in determining whether we will initially issue the loan and also in assigning values and determining impairment. We assign an overall rating to each loan using an internal rating scale of AA (highest quality) to B (lowest quality). We review and adjust, as needed, our internal credit quality ratings on an annual basis. This review process is performed more frequently for mortgage loans deemed to have a higher risk of delinquency. We estimate an allowance for credit losses that we expect to incur over the life of our mortgage loans using a probability of default method. For each loan, we estimate the probability that the loan will default before its maturity (probability of default) and the amount of the loss if the loan defaults (loss given default). These two factors result in an expected loss percentage that is applied to the amortized cost of each loan to determine the expected credit loss. As we are the original underwriter of the mortgage loans, the amortized cost generally equals the principal amount of the loan. We measure losses on defaults of our mortgage loans as the excess amortized cost of the mortgage loan over the fair value of the underlying collateral in the event that we foreclose on the loan or over the expected future cash flows of the loan if we retain the mortgage loan until payoff. We do not purchase mortgage loans with existing credit impairments. In estimating the probability of default, we consider historical experience, current market conditions, and reasonable and supportable forecasts about the future market conditions. We utilize our historical loan experience in combination with a large third-party industry database for a period of time that aligns with the average life of our loans based on the maturity dates of the loans and prepayment experience. Our model utilizes an industry database of the historical loss experience based on our actual portfolio characteristics such as loan-to-value, debt service coverage, collateral type, geography, and late payment history. In addition, because we actively manage our portfolio, we may extend the term of a loan in certain situations and will accordingly extend the maturity date in the estimate of probability of default. In estimating the loss given default, we primarily consider the type and value of collateral and secondarily the expected liquidation costs and time to recovery. The primary market factors that we consider in our forecast of future market conditions are gross domestic product, unemployment rates, interest rates, inflation, commercial real estate values, household formation, and retail sales. We also forecast certain loan specific factors such as growth in the fair value and net operating income of collateral by property type. We include our estimate of these factors over a two-year period and for the remainder of the loans’ estimated lives, adjusted for estimated prepayments. Past the two-year forecast period, we revert to the historical assumptions ratably by the end of the fifth year of the loan after which we utilize only historical assumptions. We utilize various scenarios to estimate our allowance for expected losses ranging from a base case scenario that reflects normal market conditions to a severe case scenario that reflects adverse market conditions. We will adjust our allowance each period to utilize the scenario or weighting of the scenarios that best reflects our view of current market conditions. The following tables present information about mortgage loans by the applicable credit quality indicators: March 31, 2021 December 31, 2020 (in millions of dollars) Carrying Amount Percent of Total Carrying Amount Percent of Total Internal Rating AA $ 3.4 0.1 % $ 3.5 0.1 % A 533.7 22.2 510.0 21.0 BBB 1,810.0 75.3 1,863.0 76.6 BB 39.1 1.6 39.4 1.6 B 16.0 0.8 16.2 0.7 Total $ 2,402.2 100.0 % $ 2,432.1 100.0 % Loan-to-Value Ratio <= 65% $ 1,180.4 49.1 % $ 1,189.4 48.9 % > 65% <= 75% 986.5 41.1 1,000.3 41.1 > 75% <= 85% 156.1 6.5 155.8 6.4 > 85% 79.2 3.3 86.6 3.6 Total $ 2,402.2 100.0 % $ 2,432.1 100.0 % The followin g table presents the amortized cost of our mortgage loans by year of origination and credit quality indicators at March 31, 2021 : Prior to 2017 2017 2018 2019 2020 2021 Total (in millions of dollars) Internal Rating AA $ 3.4 $ — $ — $ — $ — $ — $ 3.4 A 376.2 60.3 63.8 16.7 17.9 — 534.9 BBB 705.0 241.0 326.3 350.2 165.7 31.6 1,819.8 BB 29.2 10.4 — — — — 39.6 B 16.0 — — — — — 16.0 Total Amortized Cost 1,129.8 311.7 390.1 366.9 183.6 31.6 2,413.7 Allowance for credit losses (3.9) (1.6) (2.1) (2.4) (1.4) (0.1) (11.5) Carrying Amount $ 1,125.9 $ 310.1 $ 388.0 $ 364.5 $ 182.2 $ 31.5 $ 2,402.2 Loan-to-Value Ratio <=65% $ 821.9 $ 131.2 $ 90.6 $ 82.3 $ 37.2 $ 20.2 $ 1,183.4 >65<=75% 161.1 109.2 280.1 284.6 146.4 11.4 992.8 >75%<=85% 106.4 37.6 13.3 — — — 157.3 >85% 40.4 33.7 6.1 — — — 80.2 Total Amortized Cost 1,129.8 311.7 390.1 366.9 183.6 31.6 2,413.7 Allowance for credit losses (3.9) (1.6) (2.1) (2.4) (1.4) (0.1) (11.5) Carrying Amount $ 1,125.9 $ 310.1 $ 388.0 $ 364.5 $ 182.2 $ 31.5 $ 2,402.2 The following table presents a roll-forward of allowance for expected credit losses by loan-to-value ratio: Three Months Ended March 31, 2021 Beginning of Year Current Period Provisions Write-Offs Recoveries End of Period (in millions of dollars) Loan-to-Value Ratio <=65% $ 3.4 $ (0.4) $ — $ — $ 3.0 >65<=75% 7.3 (1.0) — — 6.3 >75%<=85% 1.3 (0.1) — — 1.2 >85% 1.1 (0.1) — — 1.0 Total $ 13.1 $ (1.6) $ — $ — $ 11.5 Three Months Ended March 31, 2020 Beginning of Year Current Period Provisions Write-Offs Recoveries End of Period (in millions of dollars) Loan-to-Value Ratio <=65% $ 2.8 $ 0.7 $ — $ — $ 3.5 >65<=75% 4.6 1.9 — — 6.5 >75%<=85% 0.5 (0.1) — — 0.4 >85% 0.4 0.3 — — 0.7 Total $ 8.3 $ 2.8 $ — $ — $ 11.1 The decrease in our estimate of expected losses during the first quarter of 2021 is primarily due to improved economic conditions and recovery from COVID-19, specifically as it relates to underlying commercial real estate values. There were no troubled debt restructurings during the three months ended March 31, 2021 and 2020. At March 31, 2021 and December 31, 2020, we held no mortgage loans that were greater than 90 days past due regarding principal and/or interest payments. We had no loan foreclosures for the three months ended March 31, 2021 and 2020. We had no impaired mortgage loans during three months ended March 31, 2021, or 2020, nor did we recognize any interest income on mortgage loans subsequent to impairment. At March 31, 2021, we had commitments of $18.0 million to fund certain commercial mortgage loans. Consistent with how we determine the estimate of current expected credit losses for our funded mortgage loans each period, we estimate expected credit losses for loans that have not been funded but we are committed to fund at the end of each period. At March 31, 2021 and December 31, 2020, we had a de minimis amount and $0.1 million, respectively, of expected credit losses related to unfunded commitments on our consolidated balance sheets. Transfers of Financial Assets To manage our cash position more efficiently, we may enter into repurchase agreements with unaffiliated financial institutions. We generally use repurchase agreements as a means to finance the purchase of invested assets or for short-term general business purposes until projected cash flows become available from our operations or existing investments. Our repurchase agreements are typically outstanding for less than 30 days. We post collateral through our repurchase agreement transactions whereby the counterparty commits to purchase securities with the agreement to resell them to us at a later, specified date. The fair value of collateral posted is generally 102 percent of the cash received. Our investment policy also permits us to lend fixed maturity securities to unaffiliated financial institutions in short-term securities lending agreements. These agreements increase our investment income with minimal risk. Our securities lending policy requires that a minimum of 102 percent of the fair value of the securities loaned be maintained as collateral. We may receive cash and/or securities as collateral under these agreements. Cash received as collateral is typically reinvested in short-term investments. If securities are received as collateral, we are not permitted to sell or re-post them. As of March 31, 2021, the carrying amount of fixed maturity securities loaned to third parties under our securities lending program was $220.0 million, for which we received collateral in the form of cash and securities of $43.5 million and $186.4 million, respectively. As of December 31, 2020, the carrying amount of fixed maturity securities loaned to third parties under our securities lending program was $96.6 million, for which we received collateral in the form of cash and securities of $17.6 million and $82.8 million, respectively. We had no outstanding repurchase agreements at March 31, 2021 or December 31, 2020. The remaining contractual maturities of our securities lending agreements disaggregated by class of collateral pledged are as follows: March 31, 2021 December 31, 2020 Overnight and Continuous (in millions of dollars) Borrowings United States Government and Government Agencies and Authorities $ 0.1 $ 0.1 State, Municipalities, and Political Subdivisions 0.4 0.4 Public Utilities 0.5 0.3 All Other Corporate Bonds 42.5 16.8 Total Borrowings $ 43.5 $ 17.6 Gross Amount of Recognized Liability for Securities Lending Transactions 43.5 17.6 Amounts Related to Agreements Not Included in Offsetting Disclosure Contained Herein $ — $ — Certain of our U.S. insurance subsidiaries are members of regional FHLBs. Membership, which requires that we purchase a minimum amount of FHLB common stock on which we receive dividends, provides access to low-cost funding. Advances received from the FHLB are used for the purchase of short-term investments or fixed maturity securities. Additional common stock purchases may be required, based on the amount of funds we borrow from the FHLBs. The carrying value of common stock owned, collateral posted, and advances received are as follows: March 31, 2021 December 31, 2020 (in millions of dollars) Carrying Value of FHLB Common Stock $ 26.9 $ 28.2 Advances from FHLB $ 302.2 $ 312.2 Carrying Value of Collateral Posted to FHLB Fixed Maturity Securities $ 857.9 $ 944.0 Commercial Mortgage Loans 982.1 1,072.5 Total Carrying Value of Collateral Posted to FHLB $ 1,840.0 $ 2,016.5 Offsetting of Financial Instruments We enter into master netting agreements with each of our derivatives counterparties. These agreements provide for conditional rights of set-off upon the occurrence of an early termination event. An early termination event is considered a default, and it allows the non-defaulting party to offset its contracts in a loss position against any gain positions or payments due to the defaulting party. Under our agreements, default type events are defined as failure to pay or deliver as contractually agreed, misrepresentation, bankruptcy, or merger without assumption. See Note 5 for further discussion of collateral related to our derivative contracts. We have securities lending agreements with unaffiliated financial institutions that post collateral to us in return for the use of our fixed maturity securities. A right of set-off exists that allows us to keep and apply collateral received in the event of default by the counterparty. Default within a securities lending agreement would typically occur if the counterparty failed to return the securities borrowed from us as contractually agreed. In addition, if we default by not returning collateral received, the counterparty has a right of set-off against our securities or any other amounts due to us. Shown below are our financial instruments that either meet the accounting requirements that allow them to be offset in our balance sheets or that are subject to an enforceable master netting arrangement or similar agreement. Our accounting policy is to not offset these financial instruments in our balance sheets. Net amounts disclosed below have been reduced by the amount of collateral pledged to or received from our counterparties. March 31, 2021 Gross Amount Gross Amount Not of Recognized Gross Amount Net Amount Offset in Balance Sheet Financial Offset in Presented in Financial Cash Net Instruments Balance Sheet Balance Sheet Instruments Collateral Amount (in millions of dollars) Financial Assets: Derivatives $ 17.6 $ — $ 17.6 $ (9.9) $ (7.7) $ — Securities Lending 220.0 — 220.0 (176.5) (43.5) — Total $ 237.6 $ — $ 237.6 $ (186.4) $ (51.2) $ — Financial Liabilities: Derivatives $ 54.9 $ — $ 54.9 $ (54.6) $ — $ 0.3 Securities Lending 43.5 — 43.5 (43.5) — — Total $ 98.4 $ — $ 98.4 $ (98.1) $ — $ 0.3 December 31, 2020 Gross Amount Gross Amount Not of Recognized Gross Amount Net Amount Offset in Balance Sheet Financial Offset in Presented in Financial Cash Net Instruments Balance Sheet Balance Sheet Instruments Collateral Amount (in millions of dollars) Financial Assets: Derivatives $ 19.8 $ — $ 19.8 $ (10.1) $ (8.7) $ 1.0 Securities Lending 96.6 — 96.6 (79.0) (17.6) — Total $ 116.4 $ — $ 116.4 $ (89.1) $ (26.3) $ 1.0 Financial Liabilities: Derivatives $ 59.7 $ — $ 59.7 $ (59.0) $ — $ 0.7 Securities Lending 17.6 — 17.6 (17.6) — — Total $ 77.3 $ — $ 77.3 $ (76.6) $ — $ 0.7 Net Investment Income Net investment income reported in our consolidated statements of income is presented below. Three Months Ended March 31 2021 2020 (in millions of dollars) Fixed Maturity Securities $ 469.8 $ 539.8 Derivatives 16.2 20.2 Mortgage Loans 26.3 29.0 Policy Loans 4.8 4.8 Other Long-term Investments Perpetual Preferred Securities 1 3.6 (17.1) Private Equity Partnerships 2 35.9 10.4 Other 2.1 3.2 Short-term Investments 0.6 6.4 Gross Investment Income 559.3 596.7 Less Investment Expenses 7.5 8.5 Less Investment Income on Participation Fund Account Assets 3.1 3.2 Net Investment Income $ 548.7 $ 585.0 1 The net unrealized gain (loss) recognized in net investment income for the three months ended March 31, 2021 related to perpetual preferred securities still held at March 31, 2021 was $2.7 million. The net unrealized loss recognized in net investment income for the three months ended March 31, 2020 related to perpetual preferred securities still held at March 31, 2020 was $17.9 million. 2 The net unrealized gain recognized in net investment income for the three months ended March 31, 2021 related to private equity partnerships still held at March 31, 2021 was $27.0 million. The net unrealized gain recognized in net investment income for the three months ended March 31, 2020 related to private equity partnerships still held at March 31, 2020 was $5.4 million. See Note 3 for further discussion of private equity partnerships. Realized Investment Gain and Loss Realized investment gains and losses are as follows: Three Months Ended March 31 2021 2020 (in millions of dollars) Fixed Maturity Securities Gross Gains on Sales 1 $ 71.3 $ 1.4 Gross Losses on Sales (1.1) (0.7) Credit Losses (8.3) (53.9) Mortgage Loans and Other Invested Assets Gross Gains on Sales 2.5 0.3 Gross Losses on Sales — (0.2) Credit Losses 1.7 (2.6) Embedded Derivative in Modified Coinsurance Arrangement 16.9 (86.9) All Other Derivatives 1.7 (0.7) Foreign Currency Transactions (0.1) (0.7) Net Realized Investment Gain (Loss) $ 84.6 $ (144.0) 1 Gross gains on sales of fixed maturity securities includes gains of $67.6 million as a result of the second phase of the reinsurance transaction that we completed during the first quarter of 2021. See Note 12 for further discussion.

Derivative Financial Instrument

Derivative Financial Instruments	3 Months Ended
	Mar. 31, 2021
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Financial Instruments	Derivative Financial Instruments Purpose of Derivatives We are exposed to certain risks relating to our ongoing business operations. The primary risks managed by using derivative instruments are interest rate risk, risk related to matching duration for our assets and liabilities, foreign currency risk, and credit risk. Historically, we have utilized current and forward interest rate swaps, current and forward currency swaps, forward benchmark interest rate locks, currency forward contracts, forward contracts on specific fixed income securities, and credit default swaps. Transactions hedging interest rate risk are primarily associated with our individual and group long-term care and individual and group disability products. All other product portfolios are periodically reviewed to determine if hedging strategies would be appropriate for risk management purposes. We do not use derivative financial instruments for speculative purposes. Derivatives designated as cash flow hedges and used to reduce our exposure to interest rate and duration risk are as follows: • Interest rate swaps are used to hedge interest rate risks and to improve the matching of assets and liabilities. An interest rate swap is an agreement in which we agree with other parties to exchange, at specified intervals, the difference between fixed rate and variable rate interest amounts. We use interest rate swaps to hedge the anticipated purchase of fixed maturity securities thereby protecting us from the potential adverse impact of declining interest rates on the associated policy reserves. We also use interest rate swaps to hedge the potential adverse impact of rising interest rates in anticipation of issuing fixed rate long-term debt. • Forward benchmark interest rate locks are used to minimize interest rate risk associated with the anticipated purchase or disposal of fixed maturity securities or debt. A forward benchmark interest rate lock is a derivative contract without an initial investment where we and the counterparty agree to purchase or sell a specific benchmark interest rate fixed maturity bond at a future date at a pre-determined price. Derivatives designated as fair value hedges and previously used to reduce our exposure to interest rate and duration risk included: • Interest rate swaps were used to effectively convert certain of our fixed rate securities into floating rate securities which were used to fund our floating rate long-term debt. Under these swap agreements, we received a variable rate of interest and paid a fixed rate of interest. Additionally, we used interest rate swaps to effectively convert certain fixed rate, long-term debt into floating rate long-term debt. Under these swap agreements, we received a fixed rate of interest and paid a variable rate of interest. Derivatives designated as either cash flow or fair value hedges and used to reduce our exposure to foreign currency risk are as follows: • Foreign currency interest rate swaps are used to hedge the currency risk of certain foreign currency-denominated fixed maturity securities owned for portfolio diversification. Under these swap agreements, we agree to pay, at specified intervals, fixed rate foreign currency-denominated principal and interest payments in exchange for fixed rate payments in the functional currency of the operating segment. Derivatives not designated as hedging instruments and used to reduce our exposure to foreign currency risk, credit losses on securities owned, and volatility of the underlying deferred assets in our non-qualified defined contribution plan are as follows: • Foreign currency interest rate swaps previously designated as hedges were used to hedge the currency risk of certain foreign currency-denominated fixed maturity securities owned for portfolio diversification. These derivatives were effective hedges prior to novation to a new counterparty. In conjunction with the novation, these derivatives were de-designated as hedges. We agree to pay, at specified intervals, fixed rate foreign currency-denominated principal and interest payments in exchange for fixed rate payments in the functional currency of the operating segment. We hold offsetting swaps wherein we agree to pay fixed rate principal and interest payments in the functional currency of the operating segment in exchange for fixed rate foreign currency-denominated payments. • Credit default swaps are used as economic hedges against credit risk but do not qualify for hedge accounting. A credit default swap is an agreement in which we agree with another party to pay, at specified intervals, a fixed-rate fee in exchange for insurance against a credit event on a specific investment. If a defined credit event occurs, our counterparty may either pay us a net cash settlement, or we may surrender the specific investment to them in exchange for cash equal to the full notional amount of the swap. Credit events typically include events such as bankruptcy, failure to pay, or certain types of debt restructuring. • Foreign currency forward contracts are used to minimize foreign currency risk. A foreign currency forward is a derivative without an initial investment where we and the counterparty agree to exchange a specific amount of currencies, at a specific exchange rate, on a specific date. We use these forward contracts to hedge the currency risk arising from foreign-currency denominated securities. • Total Return Swap s are used to economically hedge a portion of the liability related to our non-qualified defined contribution plan. A total return swap is an agreement in which we pay a floating rate of interest to the counterparty and receive the total return on a portfolio of exchange traded funds. These swaps are cash settled on the last day of every month and the notional amended each month based on periodic distributions from and contributions to the plan assets. Derivative Risks The basic types of risks associated with derivatives are market risk (that the value of the derivative will be adversely impacted by changes in the market, primarily the change in interest and exchange rates) and credit risk (that the counterparty will not perform according to the terms of the contract). The market risk of the derivatives should generally offset the market risk associated with the hedged financial instrument or liability. To help limit the credit exposure of the derivatives, we enter into master netting agreements with our counterparties whereby contracts in a gain position can be offset against contracts in a loss position. We also typically enter into bilateral, cross-collateralization agreements with our counterparties to help limit the credit exposure of the derivatives. These agreements require the counterparty in a loss position to submit acceptable collateral with the other counterparty in the event the net loss position meets or exceeds an agreed upon amount. Credit exposure on derivatives is limited to the value of those contracts in a net gain position, including accrued interest receivable less collateral held. As of March 31, 2021, the Company had no credit exposure on derivatives. At December 31, 2020, we had $0.7 million credit exposure on derivatives. The table below summarizes the nature and amount of collateral received from and posted to our derivative counterparties. March 31, 2021 December 31, 2020 (in millions of dollars) Carrying Value of Collateral Received from Counterparties Cash $ 8.8 $ 8.7 Carrying Value of Collateral Posted to Counterparties Fixed Maturity Securities $ 46.8 $ 54.0 See Note 4 for further discussion of our master netting agreements. The majority of our derivative instruments contain provisions that require us to maintain specified issuer credit ratings and financial strength ratings. Should our ratings fall below these specified levels, we would be in violation of the provisions, and our derivatives counterparties could terminate our contracts and request immediate payment. The aggregate fair value of all derivative instruments with credit risk-related contingent features that were in a liability position was $54.9 million and $59.7 million at March 31, 2021 and December 31, 2020, respectively. Derivative Transactions The table below summarizes, by notional amounts, the activity for each category of derivatives. The notional amounts represent the basis upon which our counterparty pay and receive amounts are calculated. Swaps Receive Receive Credit Default Total Forwards Total (in millions of dollars) Balance at December 31, 2019 $ 611.1 $ 250.0 $ 11.4 $ — $ 8.9 $ 881.4 Additions 52.0 — — — — 52.0 Terminations — — — — 1.3 1.3 Foreign Currency — — (0.7) — — (0.7) Balance at March 31, 2020 $ 663.1 $ 250.0 $ 10.7 $ — $ 7.6 $ 931.4 Balance at December 31, 2020 $ 720.8 $ — $ 11.7 $ — $ 11.9 $ 744.4 Additions 26.2 — — 75.5 — 101.7 Foreign Currency — — 0.2 — — 0.2 Balance at March 31, 2021 $ 747.0 $ — $ 11.9 $ 75.5 $ 11.9 $ 846.3 Cash Flow Hedges As of March 31, 2021 and December 31, 2020, we had $210.2 million notional amount of receive fixed, pay fixed, open current and forward foreign currency interest rate swaps to hedge fixed income foreign currency-denominated securities. During the first quarter of 2021, in connection with the second phase of the Closed Block individual disability reinsurance transaction, we reclassified $0.6 million of deferred gains from accumulated other comprehensive income into earnings included in the net realized investment gain line item on our income statement. The deferred gains were related to previously terminated interest rate swaps designated as hedging instruments of fixed maturity securities in the Closed Block individual disability product line. See Note 12 for further discussion. As of March 31, 2021, we expect to amortize approximately $56.9 million of net deferred gains on derivative instruments during the next twelve months. This amount will be reclassified from accumulated other comprehensive income into earnings and reported on the same income statement line item as the hedged item. The income statement line items that will be affected by this amortization are net investment income and interest and debt expense. Additional amounts that may be reclassified from accumulated other comprehensive income into earnings to offset the earnings impact of foreign currency translation of hedged items cannot be estimated. As of March 31, 2021, we are hedging the variability of future cash flows associated with forecasted transactions through the year 2045. Fair Value Hedges As of March 31, 2021 and December 31, 2020, we had $388.6 million and $362.4 million notional amount of receive fixed, pay fixed, open current and forward foreign currency interest rate swaps to hedge fixed income foreign currency-denominated securities. At December 31, 2019, we had $250.0 million notional amount of receive fixed, pay variable interest rate swaps to hedge the changes in the fair value of certain fixed rate long-term debt which matured in the third quarter of 2020 along with the hedged debt. These swaps effectively converted the associated fixed rate long-term debt into floating rate debt and provided for a better matching of interest rates with our short-term investments, which have frequent interest rate resets similar to a floating rate security. The following table summarizes the carrying amount of hedged assets and the related cumulative basis adjustments related to our fair value hedges: Carrying Amount of Hedged Assets Cumulative Amount of Fair Value Hedging Adjustment Included in the Carrying Amount of the Hedged Assets March 31, 2021 December 31, 2020 March 31, 2021 December 31, 2020 (in millions of dollars) Fixed maturity securities: Receive fixed functional currency interest, pay fixed foreign currency interest $ 405.6 $ 404.5 $ 14.9 $ 24.4 For the three months ended March 31, 2021 and March 31, 2020, $(7.0) million and $28.8 million, respectively, of the derivative instruments' gain (loss) was excluded from the assessment of hedge effectiveness. There were no instances wherein we discontinued fair value hedge accounting due to a hedged firm commitment no longer qualifying as a fair value hedge. Derivatives not Designated as Hedging Instruments As of March 31, 2021 and December 31, 2020, we held $148.2 million notional amount of receive fixed, pay fixed, foreign currency interest rate swaps. These derivatives are not designated as hedges, and as such, changes in fair value related to these derivatives are reported in earnings as a component of net realized investment gain or loss. As of March 31, 2021 and December 31, 2020, we held $11.9 million and $11.7 million, respectively, notional amount of single name credit default swaps. We entered into these swaps in order to mitigate the credit risk associated with specific securities owned. As of March 31, 2021 and December 31, 2020, we held $11.9 million notional amount of foreign currency forwards to mitigate the foreign currency risk associated with specific securities owned. We sponsor a non-qualified defined contribution plan for certain current and former employees. During the first quarter of 2021, we entered into a $75.5 million notional total return swap in order to mitigate the volatility associated with changes in the fair value of the underlying notional assets in our non-qualified defined contribution plan. This derivative is an economic hedge not designated as a hedging instrument, and changes in fair value are reported as a component of other expenses in our income statement. We have an embedded derivative in a modified coinsurance arrangement for which we include in our realized investment gains and losses a calculation intended to estimate the value of the option of our reinsurance counterparty to cancel the reinsurance contract with us. However, neither party can unilaterally terminate the reinsurance agreement except in extreme circumstances resulting from regulatory supervision, delinquency proceedings, or other direct regulatory action. Cash settlements or collateral related to this embedded derivative are not required at any time during the reinsurance contract or at termination of the reinsurance contract. There are no credit-related counterparty triggers, and any accumulated embedded derivative gain or loss reduces to zero over time as the reinsured business winds down. Locations and Amounts of Derivative Financial Instruments The following tables summarize the location and fair values of derivative financial instruments, as reported in our consolidated balance sheets. March 31, 2021 Derivative Assets Derivative Liabilities Balance Sheet Fair Balance Sheet Fair (in millions of dollars) Designated as Hedging Instruments Cash Flow Hedges Foreign Exchange Contracts Other L-T Investments $ 15.4 Other Liabilities $ 10.1 Fair Value Hedges Foreign Exchange Contracts Other L-T Investments 2.0 Other Liabilities 22.2 Total Designated as Hedging Instruments $ 17.4 $ 32.3 Not Designated as Hedging Instruments Credit Default Swaps Other L-T Investments $ 0.1 Other Liabilities $ — Forwards Other L-T Investments 0.1 Other Liabilities 0.1 Foreign Exchange Contracts Other L-T Investments — Other Liabilities 22.5 Embedded Derivative in Modified Coinsurance Arrangement Other L-T Investments — Other Liabilities 22.9 Total Not Designated as Hedging Instruments $ 0.2 $ 45.5 December 31, 2020 Derivative Assets Derivative Liabilities Balance Sheet Fair Balance Sheet Fair (in millions of dollars) Designated as Hedging Instruments Cash Flow Hedges Foreign Exchange Contracts Other L-T Investments $ 16.4 Other Liabilities $ 9.4 Fair Value Hedges Foreign Exchange Contracts Other L-T Investments 3.3 Other Liabilities 26.0 Total Designated as Hedging Instruments $ 19.7 $ 35.4 Not Designated as Hedging Instruments Credit Default Swaps Other L-T Investments $ 0.1 Other Liabilities $ — Forwards Other L-T Investments — Other Liabilities 0.5 Foreign Exchange Contracts Other L-T Investments — Other Liabilities 23.8 Embedded Derivative in Modified Coinsurance Arrangement Other L-T Investments — Other Liabilities 39.8 Total Not Designated as Hedging Instruments $ 0.1 $ 64.1 The following tables summarize the location of gains and losses of derivative financial instruments designated as hedging instruments, as reported in our consolidated statements of income. Three Months Ended March 31 2021 2020 Net Investment Income Net Realized Investment Gain (Loss) Interest and Debt Expense Net Investment Income Net Realized Investment Gain (Loss) Interest and Debt Expense (in millions of dollars) Total Income and Expense Presented in the Consolidated Statements of Income of Which Hedged Items are Recorded $ 548.7 $ 84.6 $ 44.4 $ 585.0 $ (144.0) $ 45.7 Gain (Loss) on Cash Flow Hedging Relationships Interest Rate Swaps: Hedged items 52.0 2.4 7.3 73.0 — 7.3 Derivatives Designated as Hedging Instruments 15.5 1.8 0.1 19.2 — 0.6 Foreign Exchange Contracts: Hedged items 3.1 — — 2.9 — — Derivatives Designated as Hedging Instruments 0.3 — — 0.9 — — Gain (Loss) on Fair Value Hedging Relationships Interest Rate Swaps: Hedged items — — — — (1.5) 3.6 Derivatives Designated as Hedging Instruments — — — — 1.5 0.1 Foreign Exchange Contracts Hedged items 2.3 (9.5) — 1.4 (13.2) — Derivatives Designated as Hedging Instruments 1.0 9.5 — 0.8 13.2 — The following table summarizes the location of gains and losses of derivative financial instruments designated as cash flow hedging instruments, as reported in our consolidated statements of comprehensive income (loss). Three Months Ended March 31 2021 2020 (in millions of dollars) Gain (Loss) Recognized in Other Comprehensive Income (Loss) on Derivatives Foreign Exchange Contracts $ (1.5) $ 19.5 The following table summarizes the location of gains and losses on our derivatives not designated as hedging instruments, as reported in our consolidated statements of income. Three Months Ended March 31 2021 2020 (in millions of dollars) Net Realized Investment Gain (Loss) Credit Default Swaps $ (0.1) $ 0.8 Foreign Exchange Contracts 1.8 (1.5) Embedded Derivative in Modified Coinsurance Arrangement 16.9 (86.9) Total $ 18.6 $ (87.6) Other Expenses Total Return Swaps $ 1.3 $ —

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	3 Months Ended
	Mar. 31, 2021
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss)	Components of our accumulated other comprehensive income (loss), after tax, and related changes are as follows: Net Unrealized Gain on Securities Net Gain on Hedges Foreign Currency Translation Adjustment Unrecognized Pension and Postretirement Benefit Costs Total (in millions of dollars) Balance at December 31, 2020 $ 1,067.7 $ 97.8 $ (261.3) $ (530.0) $ 374.2 Other Comprehensive Income (Loss) Before Reclassifications (447.2) (6.8) 7.3 (0.5) (447.2) Amounts Reclassified from Accumulated Other Comprehensive Income or Loss 57.7 (13.9) — 4.3 48.1 Net Other Comprehensive Income (Loss) (389.5) (20.7) 7.3 3.8 (399.1) Balance at March 31, 2021 $ 678.2 $ 77.1 $ (254.0) $ (526.2) $ (24.9) Balance at December 31, 2019 $ 615.9 $ 187.8 $ (281.6) $ (484.8) $ 37.3 Other Comprehensive Income (Loss) Before Reclassifications (263.2) 37.7 (63.6) 3.1 (286.0) Amounts Reclassified from Accumulated Other Comprehensive Income or Loss 42.6 (14.9) — 3.9 31.6 Net Other Comprehensive Income (Loss) (220.6) 22.8 (63.6) 7.0 (254.4) Balance at March 31, 2020 $ 395.3 $ 210.6 $ (345.2) $ (477.8) $ (217.1) The net unrealized gain on securities consists of the following components: March 31 December 31 2021 2020 Change (in millions of dollars) Fixed Maturity Securities $ 5,517.4 $ 7,597.6 $ (2,080.2) Deferred Acquisition Costs (66.6) (85.1) 18.5 Reserves for Future Policy and Contract Benefits (4,588.9) (6,225.6) 1,636.7 Reinsurance Recoverable 133.3 200.2 (66.9) Income Tax (317.0) (419.4) 102.4 Total $ 678.2 $ 1,067.7 $ (389.5) March 31 December 31 2020 2019 Change (in millions of dollars) Fixed Maturity Securities $ 4,261.2 $ 6,364.4 $ (2,103.2) Deferred Acquisition Costs (37.4) (62.7) 25.3 Reserves for Future Policy and Contract Benefits (3,899.5) (5,803.1) 1,903.6 Reinsurance Recoverable 322.7 424.7 (102.0) Income Tax (251.7) (307.4) 55.7 Total $ 395.3 $ 615.9 $ (220.6) Amounts reclassified from accumulated other comprehensive income (loss) were recognized in our consolidated statements of income as follows: Three Months Ended March 31 2021 2020 (in millions of dollars) Net Unrealized Gain on Securities Net Realized Investment Gain (Loss) Gain on Sales of Securities $ 68.3 $ — Credit Losses on Fixed Maturity Securities (8.3) (53.9) Loss on Benefits and Change in Reserves for Future Benefits (133.1) — (73.1) (53.9) Income Tax Benefit (15.4) (11.3) Total $ (57.7) $ (42.6) Net Gain on Hedges Net Investment Income Gain on Interest Rate Swaps and Forwards $ 15.3 $ 18.8 Gain on Foreign Exchange Contracts 0.5 0.5 Net Realized Investment Gain Gain on Interest Rate Swaps 1.8 — Interest and Debt Expense Loss on Interest Rate Swaps — (0.6) 17.6 18.7 Income Tax Expense 3.7 3.8 Total $ 13.9 $ 14.9 Unrecognized Pension and Postretirement Benefit Costs Other Expenses Amortization of Net Actuarial Loss $ (5.6) $ (5.0) Amortization of Prior Service Credit 0.1 0.1 (5.5) (4.9) Income Tax Benefit (1.2) (1.0) Total $ (4.3) $ (3.9)

Liability for Unpaid Claims and

Liability for Unpaid Claims and Claim Adjustment Expenses	3 Months Ended
	Mar. 31, 2021
Insurance [Abstract]
Liability for Unpaid Claims and Claims Adjustment Expenses Disclosure	Changes in the liability for unpaid claims and claim adjustment expenses are as follows: 2021 2020 (in millions of dollars) Balance at January 1 $ 24,180.2 $ 23,076.7 Less Reinsurance Recoverable 8,378.9 2,246.8 Net Balance at January 1 15,801.3 20,829.9 Incurred Related to Current Year 1,782.0 1,605.9 Prior Years Interest 183.4 271.9 All Other Incurred (55.9) (126.7) Foreign Currency 17.3 (127.6) Total Incurred 1,926.8 1,623.5 Paid Related to Current Year (409.2) (368.0) Prior Years (1,327.2) (1,453.7) Total Paid (1,736.4) (1,821.7) Reserves Ceded Pursuant to Reinsurance Transaction (990.0) — Net Balance at March 31 15,001.7 20,631.7 Plus Reinsurance Recoverable 9,225.8 2,260.7 Balance at March 31 $ 24,227.5 $ 22,892.4 The majority of the net balances are related to disability claims with long-tail payouts on which interest earned on assets backing liabilities is an integral part of pricing and reserving. Interest accrued on prior year reserves has been calculated on the opening reserve balance less one-half of the period's claim payments relative to prior years at our average reserve discount rate for the respective periods. "Incurred Related to Prior Years - All Other Incurred" shown in the preceding chart includes the $133.1 million increase in benefits and change in reserves for future benefits resulting from the realization of previously unrealized investment gains and losses as a result of the second phase of the Closed Block individual disability reinsurance transaction, which impacts the comparability between the years presented. Excluding that adjustment, the variability exhibited year over year is primarily caused by the level of claim resolutions in the period relative to the long-term expectations reflected in the reserves. Our claim resolution rate assumption used in determining reserves is our expectation of the resolution rate we will experience over the life of the block of business and will vary from actual experience in any one period, both favorably and unfavorably. Also included in the first quarter of 2021 was a reinsurance recoverable of $990.0 million representing the ceded reserves related to the cohort of policies on claim status as of January 1, 2021 (DLR cohort) related to the second phase of the Closed Block individual disability reinsurance transaction. See Note 12 for further discussion regarding the total impacts of the Closed Block individual disability reinsurance transaction. Reconciliation A reconciliation of policy and contract benefits and reserves for future policy and contract benefits as reported in our consolidated balance sheets to the liability for unpaid claims and claim adjustment expenses is as follows: March 31 2021 2020 (in millions of dollars) Policy and Contract Benefits $ 1,899.3 $ 1,760.3 Reserves for Future Policy and Contract Benefits 48,112.3 45,706.5 Total 50,011.6 47,466.8 Less: Life Reserves for Future Policy and Contract Benefits 8,389.3 8,428.5 Accident and Health Active Life Reserves 12,805.9 12,246.4 Adjustment Related to Unrealized Investment Gains and Losses 4,588.9 3,899.5 Liability for Unpaid Claims and Claim Adjustment Expenses $ 24,227.5 $ 22,892.4

Segment Information

Segment Information	3 Months Ended
	Mar. 31, 2021
Segment Reporting [Abstract]
Segment Information	We have three principal operating business segments: Unum US, Unum International, and Colonial Life. Our other segments are Closed Block and Corporate. Segment information is as follows: Three Months Ended March 31 2021 2020 (in millions of dollars) Premium Income Unum US Group Disability Group Long-term Disability $ 457.7 $ 463.0 Group Short-term Disability 215.2 203.2 Group Life and Accidental Death & Dismemberment Group Life 410.0 414.5 Accidental Death & Dismemberment 41.4 41.7 Supplemental and Voluntary Individual Disability 115.7 109.5 Voluntary Benefits 218.7 230.4 Dental and Vision 67.1 65.4 1,525.8 1,527.7 Unum International Unum UK Group Long-term Disability 97.1 90.8 Group Life 27.3 30.9 Supplemental 28.0 23.9 Unum Poland 22.0 19.0 174.4 164.6 Colonial Life Accident, Sickness, and Disability 240.7 249.3 Life 96.6 93.8 Cancer and Critical Illness 89.1 91.6 426.4 434.7 Closed Block Long-term Care 177.4 164.8 Individual Disability 72.1 77.0 All Other 2.2 2.6 251.7 244.4 Total Premium Income $ 2,378.3 $ 2,371.4 Unum US Unum International Colonial Life Closed Block Corporate Total (in millions of dollars) Three Months Ended March 31, 2021 Premium Income $ 1,525.8 $ 174.4 $ 426.4 $ 251.7 $ — $ 2,378.3 Net Investment Income 179.7 26.0 37.7 297.2 8.1 548.7 Other Income 40.4 0.1 0.2 18.4 1.3 60.4 Adjusted Operating Revenue $ 1,745.9 $ 200.5 $ 464.3 $ 567.3 $ 9.4 $ 2,987.4 Adjusted Operating Income (Loss) $ 115.7 $ 26.4 $ 73.3 $ 97.0 $ (38.9) $ 273.5 Three Months Ended March 31, 2020 Premium Income $ 1,527.7 $ 164.6 $ 434.7 $ 244.4 $ — $ 2,371.4 Net Investment Income 179.6 26.5 37.7 336.1 5.1 585.0 Other Income 40.2 — 0.3 18.2 — 58.7 Adjusted Operating Revenue $ 1,747.5 $ 191.1 $ 472.7 $ 598.7 $ 5.1 $ 3,015.1 Adjusted Operating Income (Loss) $ 261.8 $ 19.4 $ 81.1 $ 29.7 $ (45.9) $ 346.1 March 31 December 31 2021 2020 (in millions of dollars) Assets Unum US $ 18,563.1 $ 19,034.2 Unum International 4,163.6 4,206.2 Colonial Life 4,817.3 4,864.3 Closed Block 37,845.1 38,187.2 Corporate 3,867.5 4,333.9 Total Assets $ 69,256.6 $ 70,625.8 We measure and analyze our segment performance on the basis of "adjusted operating revenue" and "adjusted operating income" or "adjusted operating loss", which differ from total revenue and income before income tax as presented in our consolidated statements of income due to the exclusion of net realized investment gains and losses and the amortization of the cost of reinsurance as well as certain other items as specified in the reconciliations below. We believe adjusted operating revenue and adjusted operating income or loss are better performance measures and better indicators of the revenue and profitability and underlying trends in our business. These performance measures are in accordance with GAAP guidance for segment reporting, but they should not be viewed as a substitute for total revenue, income before income tax, or net income. Realized investment gains or losses depend on market conditions and do not necessarily relate to decisions regarding the underlying business of our segments. Our investment focus is on investment income to support our insurance liabilities as opposed to the generation of realized investment gains or losses. Although we may experience realized investment gains or losses which will affect future earnings levels, a long-term focus is necessary to maintain profitability over the life of the business since our underlying business is long-term in nature, and we need to earn the interest rates assumed in calculating our liabilities. We have exited a substantial portion of our Closed Block individual disability product line through the two phases of the reinsurance agreement that was executed in December 2020 and March 2021. As a result, we exclude the amortization of the cost of reinsurance that was recognized as a result of the exit of the business related to the DLR cohort of policies. We believe that the exclusion of the amortization of the cost of reinsurance provides a better view of our results from our ongoing businesses. See Note 12 for further discussion regarding the total impacts of the Closed Block individual disability reinsurance transaction and the amortization of the cost of reinsurance. We may at other times exclude certain other items from our discussion of financial ratios and metrics in order to enhance the understanding and comparability of our operational performance and the underlying fundamentals but this exclusion is not an indication that similar items may not recur and does not replace net income or net loss as a measure of our overall profitability. A reconciliation of total revenue to "adjusted operating revenue" and income before income tax to "adjusted operating income" is as follows: Three Months Ended March 31 2021 2020 (in millions of dollars) Total Revenue $ 3,072.0 $ 2,871.1 Excluding: Net Realized Investment Gain (Loss) 84.6 (144.0) Adjusted Operating Revenue $ 2,987.4 $ 3,015.1 Income Before Income Tax $ 198.8 $ 202.1 Excluding: Net Realized Investment Gains and Losses Net Realized Investment Gain Related to Reinsurance Transaction 67.6 — Net Realized Investment Gain (Loss), Other 17.0 (144.0) Total Net Realized Investment Gain (Loss) 84.6 (144.0) Items Related to Closed Block Individual Disability Reinsurance Transaction Change in Benefit Reserves and Transaction Costs (139.3) — Amortization of the Cost of Reinsurance (20.0) — Total Items Related to Closed Block Individual Disability Reinsurance Transaction (159.3) — Adjusted Operating Income $ 273.5 $ 346.1

Employee Benefit Plans

Employee Benefit Plans	3 Months Ended
	Mar. 31, 2021
Retirement Benefits [Abstract]
Pension and Other Postretirement Benefits Disclosure	Employee Benefit Plans Defined Benefit Pension and Other Postretirement Benefit (OPEB) Plans We sponsor several defined benefit pension and OPEB plans for our employees, including non-qualified pension plans. The U.S. qualified and non-qualified defined benefit pension plans comprise the majority of our total benefit obligation and benefit cost. We maintain a separate defined benefit plan for eligible employees in our U.K. operation. The U.S. defined benefit pension plans were closed to new entrants on December 31, 2013, the OPEB plan was closed to new entrants on December 31, 2012, and the U.K. plan was closed to new entrants on December 31, 2002. The following table provides the components of the net periodic benefit cost (credit) for the defined benefit pension and OPEB plans. Three Months Ended March 31 Pension Benefits U.S. Plans U.K. Plan OPEB 2021 2020 2021 2020 2021 2020 (in millions of dollars) Service Cost $ 2.4 $ 2.8 $ — $ — $ — $ — Interest Cost 16.3 18.2 1.1 1.2 0.8 1.0 Expected Return on Plan Assets (25.2) (26.7) (2.5) (2.4) (0.1) (0.1) Amortization of: Net Actuarial Loss 5.3 4.7 0.3 0.3 — — Prior Service Credit — — — — (0.1) (0.1) Total Net Periodic Benefit Cost (Credit) $ (1.2) $ (1.0) $ (1.1) $ (0.9) $ 0.6 $ 0.8 The service cost component of net periodic pension and postretirement benefit cost (credit) is included as a component of compensation expense in our consolidated statements of income. All other components of net periodic pension and postretirement benefit cost are included in other expenses.

Stockholders' Equity and Earnin

Stockholders' Equity and Earnings Per Common Share	3 Months Ended
	Mar. 31, 2021
Stockholders' Equity and Earnings Per Common Share [Abstract]
Earnings Per Share Disclosure	Earnings Per Common Share Net income per common share is determined as follows: Three Months Ended March 31 2021 2020 (in millions of dollars, except share data) Numerator Net Income $ 153.0 $ 161.0 Denominator (000s) Weighted Average Common Shares - Basic 204,133.3 203,306.0 Dilution for Assumed Exercises of Stock Options and Nonvested Stock Awards 604.0 49.7 Weighted Average Common Shares - Assuming Dilution 204,737.3 203,355.7 Net Income Per Common Share Basic $ 0.75 $ 0.79 Assuming Dilution $ 0.75 $ 0.79 We compute basic earnings per share by dividing net income by the weighted average number of common shares outstanding for the period. In computing earnings per share assuming dilution, we include potential common shares that are dilutive (those that reduce earnings per share). We use the treasury stock method to account for the effect of outstanding stock options, nonvested stock success units, nonvested restricted stock units, and nonvested performance share units on the computation of diluted earnings per share. Under this method, the potential common shares from stock options, nonvested stock success units, and nonvested restricted stock units will each have a dilutive effect, as individually measured, when the average market price of
Stockholders' Equity Disclosure	Common Stock As part of our capital deployment strategy, we may repurchase shares of Unum Group's common stock, as authorized by our board of directors. During the first quarter of 2021, we did not have an open share repurchase program and did not repurchase any shares. Preferred Stock Unum Group has 25.0 million shares of preferred stock authorized with a par value of $0.10 per share. No preferred stock has been issued to date.

Commitments and Contingent Liab

Commitments and Contingent Liabilities	3 Months Ended
	Mar. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies Disclosure	Commitments and Contingent Liabilities Contingent Liabilities We are a defendant in a number of litigation matters that have arisen in the normal course of business, including the matters discussed below. Further, state insurance regulatory authorities and other federal and state authorities regularly make inquiries and conduct investigations concerning our compliance with applicable insurance and other laws and regulations. Given the complexity and scope of our litigation and regulatory matters, it is not possible to predict the ultimate outcome of all pending investigations or legal proceedings or provide reasonable estimates of potential losses, except if noted in connection with specific matters. In some of these matters, no specified amount is sought. In others, very large or indeterminate amounts, including punitive and treble damages, are asserted. There is a wide variation of pleading practice permitted in the United States courts with respect to requests for monetary damages, including some courts in which no specified amount is required and others which allow the plaintiff to state only that the amount sought is sufficient to invoke the jurisdiction of that court. Further, some jurisdictions permit plaintiffs to allege damages well in excess of reasonably possible verdicts. Based on our extensive experience and that of others in the industry with respect to litigating or resolving claims through settlement over an extended period of time, we believe that the monetary damages asserted in a lawsuit or claim bear little relation to the merits of the case, or the likely disposition value. Therefore, the specific monetary relief sought is not stated. Unless indicated otherwise in the descriptions below, reserves have not been established for litigation and contingencies. An estimated loss is accrued when it is both probable that a liability has been incurred and the amount of the loss can be reasonably estimated. Claims Handling Matters We and our insurance subsidiaries, in the ordinary course of our business, are engaged in claim litigation where disputes arise as a result of a denial or termination of benefits. Most typically these lawsuits are filed on behalf of a single claimant or policyholder, and in some of these individual actions punitive damages are sought, such as claims alleging bad faith in the handling of insurance claims. For our general claim litigation, we maintain reserves based on experience to satisfy judgments and settlements in the normal course. We expect that the ultimate liability, if any, with respect to general claim litigation, after consideration of the reserves maintained, will not be material to our consolidated financial condition. Nevertheless, given the inherent unpredictability of litigation, it is possible that an adverse outcome in certain claim litigation involving punitive damages could, from time to time, have a material adverse effect on our consolidated results of operations in a period, depending on the results of operations for the particular period. From time to time class action allegations are pursued where the claimant or policyholder purports to represent a larger number of individuals who are similarly situated. Since each insurance claim is evaluated based on its own merits, there is rarely a single act or series of actions which can properly be addressed by a class action. Nevertheless, we monitor these cases closely and defend ourselves appropriately where these allegations are made. Miscellaneous Matters Similar to other insurers, we were the subject of an examination by a third party acting on behalf of a number of state treasurers concerning our compliance with the unclaimed property laws of the participating states. We cooperated fully with this examination and in the fourth quarter of 2017, we started the process to reach a Global Resolution Agreement with the third party regarding settlement of the examination, which we finalized in January of 2018. Under the terms of the agreement, the third party acting on behalf of the signatory states compared insured data to the Social Security Administration's Death Master File to identify deceased insureds and contract holders where a valid claim has not been made. During the fourth quarter of 2017, we established reserves which reflect our estimate of the liability expected to be paid as we execute on the terms of the settlement. In March of 2021, the third party confirmed our compliance with the terms of the settlement and closed out the audit. Securities Class Actions: Three alleged securities class action lawsuits have been filed against Unum Group and individual defendants as follows: • On June 13, 2018, an alleged securities class action lawsuit entitled Cynthia Pittman v. Unum Group, Richard McKenney, John McGarry, and Daniel Waxenberg was filed in the United States District Court for the Eastern District of Tennessee. The plaintiff seeks to represent purchasers of Unum Group publicly traded securities between January 31, 2018 and May 2, 2018. The plaintiff alleges the Company caused its shares to trade at artificially high levels by failing to disclose information about the rate of long-term care policy terminations and long-term care claim incidence resulting in misleading statements about capital management plans and long-term care reserves. The complaint asserts claims under Sections 10(b) and 20(a) of the Securities Exchange Act of 1934 and Rule 10b-5 thereunder and seeks compensatory damages in an amount to be proven at trial. The Company strongly denies these allegations and will vigorously defend the litigation. • On July 13, 2018, an alleged securities class action lawsuit entitled Scott Cunningham v. Unum Group, Richard McKenney, John McGarry, and Daniel Waxenberg was filed in the United States District Court for the Eastern District of Tennessee. The allegations, class period, and damages claimed mirror those in the Pittman matter. The Company strongly denies these allegations and will vigorously defend the litigation. • On July 25, 2018, an alleged securities class action lawsuit entitled City of Taylor Police and Fire Retirement System v. Unum Group, Richard McKenney, John McGarry, Steve Zabel, and Daniel Waxenberg was filed in the United States District Court for the Eastern District of Tennessee. The plaintiff seeks to represent purchasers of Unum Group publicly traded securities between October 27, 2016 and May 1, 2018. The allegations and damages claimed mirror those in the Pittman matter. The Company strongly denies these allegations and will vigorously defend the litigation. On November 9, 2018, the court consolidated the Pittman , Cunningham , and City of Taylor Police and Fire Retirement System cases into one matter entitled In re Unum Group Securities Litigation , appointed a lead plaintiff and lead plaintiff’s counsel, and directed the plaintiff to file a consolidated amended complaint. On January 15, 2019, the plaintiff filed a consolidated amended complaint asserting claims under Sections 10(b) and 20(a) of the Securities Exchange Act of 1934 and Rule 10b-5 thereunder and seeks compensatory damages in an amount to be proven at trial as well as costs, expenses, and attorney’s fees. On March 18, 2019, the Company filed a motion to dismiss the consolidated amended complaint. On November 4, 2019 the court heard oral argument on the motion. On June 1, 2020, the court granted the Company's motion and dismissed the cases with prejudice. On June 26, 2020, the plaintiffs filed a notice of appeal with the Sixth Circuit Court of Appeals. The court heard oral argument on March 2, 2021 and took the matter under advisement. We believe the appeal and the underlying claims lack merit and reserves have not been established for these matters as we are unable to estimate a range of reasonably possible losses. However, an adverse outcome in one or more of these actions could,

Other

Other	3 Months Ended
	Mar. 31, 2021
Other Disclosures [Abstract]
Reinsurance	Reinsurance In December 2020, we completed the first phase of a reinsurance transaction, pursuant to which Provident Life and Accident Insurance Company, The Paul Revere Life Insurance Company, and Unum Life Insurance Company of America, wholly-owned domestic insurance subsidiaries of Unum Group, and collectively referred to as "the ceding companies", each entered into separate reinsurance agreements with Commonwealth Annuity and Life Insurance Company (Commonwealth), to reinsure on a coinsurance basis effective as of July 1, 2020, approximately 75 percent of the Closed Block individual disability business, primarily direct business written by the ceding companies. On March 31, 2021, we completed the second phase of the reinsurance transaction, pursuant to which the ceding companies and Commonwealth amended and restated their respective reinsurance agreements to reinsure on a coinsurance and modified coinsurance basis effective as of January 1, 2021, a substantial portion of the remaining Closed Block individual disability business that was not ceded in December 2020, primarily business previously assumed by the ceding companies. Commonwealth established and will maintain collateralized trust accounts for the benefit of the ceding companies to secure its obligations under the reinsurance agreements. In December 2020, Provident Life and Casualty Insurance Company (PLC), also a wholly-owned domestic insurance subsidiary of Unum Group, entered into an agreement with Commonwealth whereby PLC will provide a 12-year volatility cover to Commonwealth for the active life cohort (ALR cohort). On March 31, 2021, PLC and Commonwealth amended and restated this agreement to incorporate the ALR cohort related to the additional business that was reinsured between the ceding companies and Commonwealth as part of the second phase of the transaction. As part of the amended and restated volatility cover, PLC received a payment from Commonwealth of approximately $18 million. At the end of the 12-year coverage period, Commonwealth will retain the remaining incidence and claims risk on the ALR cohort of the ceded business. In connection with the second phase of the reinsurance transaction, Commonwealth paid a total ceding commission to the ceding companies of $18.2 million. The ceding companies transferred assets of $767.0 million, which consisted primarily of cash and fixed maturity securities. In addition, we recognized the following in the first quarter of 2021 related to the second phase: • Net realized investment gains totaling $67.6 million related to the transfer of investments. • Increase in benefits and change in reserves for future benefits of $133.1 million resulting from the realization of previously unrealized investment gains and losses recorded in accumulated other comprehensive income. • Transaction costs totaling $6.2 million. • Reinsurance recoverable of $990.0 million related to the policies on claim status. • Payable of $307.2 million related to the portfolio of invested assets associated with the business ceded on a modified coinsurance basis. • Cost of reinsurance, or prepaid reinsurance premium, of $43.1 million related to the DLR cohort. The total cost of reinsurance recognized on a combined basis for the first and second phases was $854.8 million for which we amortized $20.0 million during the first three months of 2021.
Allowance for Expected Credit Losses on Premiums Receivable	Allowance for Expected Credit Losses on Premiums Receivable At March 31, 2021 and December 31, 2020, the allowance for expected credit losses on premiums receivables was $33.7 million and $38.8 million, respectively, on gross premiums receivables of $602.9 million and $525.8 million, respectively. The decrease in the allowance of $5.1 million during the three months ended March 31, 2021 was driven primarily by improvements in the age of premiums due to be collected and improvements in unemployment levels.

Basis of Presentation (Policies

Basis of Presentation (Policies)	3 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
Basis of Presentation	The accompanying consolidated financial statements of Unum Group and its subsidiaries (the Company) have been prepared in accordance with U.S. generally accepted accounting principles (GAAP) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. For further information, refer to the consolidated financial statements and footnotes included in our annual report on Form 10-K for the year ended December 31, 2020.

Fair Values of Financial Inst_2

Fair Values of Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 2021
Fair Value Disclosures [Abstract]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share	The following tables present additional information about our private equity partnerships, including commitments for additional investments which may or may not be funded: March 31, 2021 Investment Category Fair Value Redemption Term / Redemption Notice Unfunded Commitments (in millions of dollars) (in millions of dollars) Private Credit (a) $ 247.5 Not redeemable $ 190.3 41.9 Initial 2 year lock on each new investment / Quarterly after 2 year lock with 90 days notice 1.1 Total Private Credit 289.4 191.4 Private Equity (b) 249.8 Not redeemable 216.4 9.2 Initial 5.5 year lock on each new investment / Quarterly after 5.5 year lock with 90 days notice 34.3 Total Private Equity 259.0 250.7 Real Assets (c) 187.7 Not redeemable 198.9 56.3 Quarterly / 90 days notice — Total Real Assets 244.0 198.9 Total Partnerships $ 792.4 $ 641.0 December 31, 2020 Investment Category Fair Value Redemption Term / Redemption Notice Unfunded Commitments (in millions of dollars) (in millions of dollars) Private Credit (a) $ 233.3 Not redeemable $ 178.9 40.4 Initial 2 year lock on each new investment / Quarterly after 2 year lock with 90 days notice 1.3 Total Private Credit 273.7 180.2 Private Equity (b) 232.6 Not redeemable 191.0 9.2 Initial 5.5 year lock on each new investment / Quarterly after 5.5 year lock with 90 days notice 34.3 Total Private Equity 241.8 225.3 Real Assets (c) 176.3 Not redeemable 185.2 55.7 Quarterly / 90 days notice — Total Real Assets 232.0 185.2 Total Partnerships $ 747.5 $ 590.7
Fair Values by Fair Value Hierarchy Input level	The following tables present information about financial instruments measured at fair value on a recurring basis by fair value level, based on the observability of the inputs used: March 31, 2021 Level 1 Level 2 Level 3 NAV Total (in millions of dollars) Assets Fixed Maturity Securities United States Government and Government Agencies and Authorities $ 101.1 $ 475.5 $ — $ — $ 576.6 States, Municipalities, and Political Subdivisions 54.1 4,149.8 — — 4,203.9 Foreign Governments — 1,098.9 21.7 — 1,120.6 Public Utilities 594.2 5,746.9 103.4 — 6,444.5 Mortgage/Asset-Backed Securities — 847.9 77.2 — 925.1 All Other Corporate Bonds 9,144.4 19,157.6 499.2 — 28,801.2 Redeemable Preferred Stocks — 4.1 — — 4.1 Total Fixed Maturity Securities 9,893.8 31,480.7 701.5 — 42,076.0 Other Long-term Investments Derivatives Forwards — 0.1 — — 0.1 Foreign Exchange Contracts — 17.4 — — 17.4 Credit Default Swaps — 0.1 — — 0.1 Total Derivatives — 17.6 — — 17.6 Perpetual Preferred Equity Securities 26.1 0.2 5.2 — 31.5 Private Equity Partnerships — — — 792.4 792.4 Total Other Long-term Investments 26.1 17.8 5.2 792.4 841.5 Total Financial Instrument Assets Carried at Fair Value $ 9,919.9 $ 31,498.5 $ 706.7 $ 792.4 $ 42,917.5 Liabilities Other Liabilities Derivatives Forwards $ — $ 0.1 $ — $ — $ 0.1 Foreign Exchange Contracts — 54.8 — — 54.8 Embedded Derivative in Modified Coinsurance Arrangement — — 22.9 — 22.9 Total Derivatives — 54.9 22.9 — 77.8 Total Financial Instrument Liabilities Carried at Fair Value $ — $ 54.9 $ 22.9 $ — $ 77.8 December 31, 2020 Level 1 Level 2 Level 3 NAV Total (in millions of dollars) Assets Fixed Maturity Securities United States Government and Government Agencies and Authorities $ — $ 709.8 $ — $ — $ 709.8 States, Municipalities, and Political Subdivisions — 4,245.7 15.5 — 4,261.2 Foreign Governments — 1,146.4 21.8 — 1,168.2 Public Utilities 131.9 6,644.7 185.7 — 6,962.3 Mortgage/Asset-Backed Securities — 1,026.4 81.3 — 1,107.7 All Other Corporate Bonds 4,089.4 24,886.1 943.1 — 29,918.6 Redeemable Preferred Stocks — 9.5 — — 9.5 Total Fixed Maturity Securities 4,221.3 38,668.6 1,247.4 — 44,137.3 Other Long-term Investments Derivatives Foreign Exchange Contracts — 19.7 — — 19.7 Credit Default Swaps — 0.1 — — 0.1 Total Derivatives — 19.8 — — 19.8 Perpetual Preferred Equity Securities 8.4 15.2 4.7 — 28.3 Private Equity Partnerships — — — 747.5 747.5 Total Other Long-term Investments 8.4 35.0 4.7 747.5 795.6 Total Financial Instrument Assets Carried at Fair Value $ 4,229.7 $ 38,703.6 $ 1,252.1 $ 747.5 $ 44,932.9 Liabilities Other Liabilities Derivatives Forwards $ — $ 0.5 $ — $ — $ 0.5 Foreign Exchange Contracts — 59.2 — — 59.2 Embedded Derivative in Modified Coinsurance Arrangement — — 39.8 — 39.8 Total Derivatives — 59.7 39.8 — 99.5 Total Financial Instrument Liabilities Carried at Fair Value $ — $ 59.7 $ 39.8 $ — $ 99.5
Changes in Assets and Liabilities Measured at Fair Value on a Recurring Basis using Significant Unobservable Inputs	Changes in assets and liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3) are as follows: Three Months Ended March 31, 2021 Fair Value Beginning of Year Total Realized Level 3 Transfers Fair Value End of Period Change in Unrealized Gain (Loss) on Securities Held at the End of Period included in Earnings OCI (1) Purchases Sales Into Out of OCI Earnings (in millions of dollars) Fixed Maturity Securities States, Municipalities, and Political Subdivisions $ 15.5 $ — $ — $ — $ — $ — $ (15.5) $ — $ — $ — Foreign Governments 21.8 — (0.1) — — — — 21.7 (0.1) — Public Utilities 185.7 — (4.6) — — 36.0 (113.7) 103.4 (4.6) — Mortgage/Asset-Backed Securities 81.3 — (34.5) — (32.6) 86.1 (23.1) 77.2 (34.5) — All Other Corporate Bonds 943.1 — (13.8) — — — (430.1) 499.2 (13.8) — Total Fixed Maturity Securities 1,247.4 — (53.0) — (32.6) 122.1 (582.4) 701.5 (53.0) — Perpetual Preferred Equity Securities 4.7 — — — — 0.5 — 5.2 — — Embedded Derivative in Modified Coinsurance Arrangement (39.8) 16.9 — — — — — (22.9) — 16.9 (1) Other Comprehensive Income (Loss) Three Months Ended March 31, 2020 Fair Value Beginning of Year Total Realized Level 3 Transfers Fair Value End of Period Change in Unrealized Gain (Loss) on Securities Held at the End of Period included in Earnings OCI Purchases Sales Into Out of OCI Earnings (in millions of dollars) Fixed Maturity Securities States, Municipalities, and Political Subdivisions $ 41.8 $ — $ 2.8 $ — $ — $ — $ (13.3) $ 31.3 $ 2.9 $ — Foreign Governments 21.8 — (0.9) — — — — 20.9 (0.9) — Public Utilities 14.6 — (0.3) — — 18.0 (6.0) 26.3 — — Mortgage/Asset-Backed Securities 34.1 — (0.8) — — 49.2 (7.4) 75.1 (0.2) — All Other Corporate Bonds 600.5 — (50.6) 20.9 — 236.2 (254.0) 553.0 (2.2) — Total Fixed Maturity Securities 712.8 — (49.8) 20.9 — 303.4 (280.7) 706.6 (0.4) — Perpetual Preferred Equity Securities 4.6 — — — — — — 4.6 — — Embedded Derivative in Modified Coinsurance Arrangement (22.8) (86.9) — — — — — (109.7) — (86.9)
Quantitative Information Regarding Significant Unobservable Inputs	The table below provides quantitative information regarding the significant unobservable inputs used in Level 3 fair value measurements derived from internal models. Unobservable inputs for fixed maturity securities are weighted by the fair value of the securities. Certain securities classified as Level 3 are excluded from the table below due to limitations in our ability to obtain the underlying inputs used by external pricing sources. March 31, 2021 Fair Value Valuation Method Unobservable Input Range/Weighted Average (in millions of dollars) Fixed Maturity Securities All Other Corporate Bonds - Private $ 45.0 Market Approach Volatility of Credit (a) 0.50% - 47.79% / 6.58% Perpetual Preferred Equity Securities 5.2 Market Approach Market Convention (b) Priced at Cost or Owner's Equity Embedded Derivative in Modified Coinsurance Arrangement (22.9) Discounted Cash Flows Projected Liability Cash Flows Weighted Spread of Swap Curve (c) Actuarial Assumptions 0.7% December 31, 2020 Fair Value Valuation Method Unobservable Input Range/Weighted Average (in millions of dollars) Fixed Maturity Securities All Other Corporate Bonds - Private $ 45.7 Market Approach Volatility of Credit (a) 0.50% - 24.90% / 3.63% Perpetual Preferred Equity Securities 4.7 Market Approach Market Convention (b) Priced at Cost or Owner's Equity Embedded Derivative in Modified Coinsurance Arrangement (39.8) Discounted Cash Flows Projected Liability Cash Flows Weighted Spread of Swap Curve (c) Actuarial Assumptions 1.0% (a) Represents basis point adjustments for credit-specific factors (b) Represents a decision to price based on par value, cost, or owner's equity when limited data is available (c) Represents various actuarial assumptions required to derive the liability cash flows. Fair value of embedded derivative is most often driven by the change in the weighted average credit spread to the swap curve for the assets backing the hypothetical loan.
Carrying Amount and Fair Value of Financial Instruments	The following table presents the carrying amounts and estimated fair values of our financial instruments not measured at fair value and indicates the level in the fair value hierarchy of the estimated fair value measurement based on the observability of the inputs used: March 31, 2021 Estimated Fair Value Level 1 Level 2 Level 3 Total Carrying Value (in millions of dollars) Assets Mortgage Loans $ — $ 2,456.1 $ — $ 2,456.1 $ 2,402.2 Policy Loans — — 3,761.3 3,761.3 3,628.8 Other Long-term Investments Miscellaneous Long-term Investments — 26.9 24.4 51.3 51.3 Total Financial Instrument Assets Not Carried at Fair Value $ — $ 2,483.0 $ 3,785.7 $ 6,268.7 $ 6,082.3 Liabilities Long-term Debt $ 3,230.9 $ 557.9 $ — $ 3,788.8 $ 3,346.8 Payable for Collateral on Federal Home Loan Bank (FHLB) Funding Agreements — 302.2 — 302.2 302.2 Other Liabilities Unfunded Commitments — 0.9 — 0.9 0.9 Total Financial Instrument Liabilities Not Carried at Fair Value $ 3,230.9 $ 861.0 $ — $ 4,091.9 $ 3,649.9 December 31, 2020 Estimated Fair Value Level 1 Level 2 Level 3 Total Carrying Value (in millions of dollars) Assets Mortgage Loans $ — $ 2,641.8 $ — $ 2,641.8 $ 2,432.1 Policy Loans — — 3,850.8 3,850.8 3,683.9 Other Long-term Investments Miscellaneous Long-term Investments — 28.2 29.3 57.5 57.5 Total Financial Instrument Assets Not Carried at Fair Value $ — $ 2,670.0 $ 3,880.1 $ 6,550.1 $ 6,173.5 Liabilities Long-term Debt $ 2,393.1 $ 1,494.3 $ — $ 3,887.4 $ 3,345.7 Payables for Collateral on FHLB Funding Agreements — 312.2 — 312.2 312.2 Other Liabilities Unfunded Commitments — 0.9 — 0.9 0.9 Total Financial Instrument Liabilities Not Carried at Fair Value $ 2,393.1 $ 1,807.4 $ — $ 4,200.5 $ 3,658.8

Investments (Tables)

Investments (Tables)	3 Months Ended
	Mar. 31, 2021
Investments, Debt and Equity Securities [Abstract]
Amortized Cost and Fair Values of Securities by Security Type	At March 31, 2021 and December 31, 2020, all fixed maturity securities were classified as available-for-sale. The amortized cost and fair values of securities by security type are shown as follows: March 31, 2021 Amortized ACL (1) Gross Gross Fair (in millions of dollars) United States Government and Government Agencies and Authorities $ 464.6 $ — $ 112.1 $ 0.1 $ 576.6 States, Municipalities, and Political Subdivisions 3,735.9 — 506.7 38.7 4,203.9 Foreign Governments 899.0 — 224.3 2.7 1,120.6 Public Utilities 5,390.6 — 1,080.0 26.1 6,444.5 Mortgage/Asset-Backed Securities 851.6 — 73.6 0.1 925.1 All Other Corporate Bonds 25,220.2 7.3 3,698.3 110.0 28,801.2 Redeemable Preferred Stocks 4.0 — 0.1 — 4.1 Total Fixed Maturity Securities $ 36,565.9 $ 7.3 $ 5,695.1 $ 177.7 $ 42,076.0 December 31, 2020 Amortized ACL (1) Gross Gross Fair (in millions of dollars) United States Government and Government Agencies and Authorities $ 559.0 $ — $ 150.8 $ — $ 709.8 States, Municipalities, and Political Subdivisions 3,609.9 — 652.8 1.5 4,261.2 Foreign Governments 902.9 — 266.5 1.2 1,168.2 Public Utilities 5,486.4 — 1,481.9 6.0 6,962.3 Mortgage/Asset-Backed Securities 1,019.9 — 88.0 0.2 1,107.7 All Other Corporate Bonds 24,958.8 6.8 5,013.5 46.9 29,918.6 Redeemable Preferred Stocks 9.6 — — 0.1 9.5 Total Fixed Maturity Securities $ 36,546.5 $ 6.8 $ 7,653.5 $ 55.9 $ 44,137.3
Length of Time Fixed Maturity Securities had been in a Gross Unrealized Loss Position	The following charts indicate the length of time our fixed maturity securities have been in a gross unrealized loss position. March 31, 2021 Less Than 12 Months 12 Months or Greater Fair Gross Fair Gross (in millions of dollars) United States Government and Government Agencies and Authorities $ 5.9 $ 0.1 $ — $ — States, Municipalities, and Political Subdivisions 888.1 38.7 0.6 — Foreign Governments 61.8 2.7 — — Public Utilities 321.4 22.8 38.6 3.3 Mortgage/Asset-Backed Securities 0.6 0.1 3.1 — All Other Corporate Bonds 1,883.4 84.0 246.0 26.0 Total Fixed Maturity Securities $ 3,161.2 $ 148.4 $ 288.3 $ 29.3 December 31, 2020 Less Than 12 Months 12 Months or Greater Fair Gross Fair Gross (in millions of dollars) States, Municipalities, and Political Subdivisions $ 133.4 $ 1.5 $ 0.1 $ — Foreign Governments 20.3 1.2 — — Public Utilities 76.3 3.7 25.4 2.3 Mortgage/Asset-Backed Securities 3.0 0.1 3.1 0.1 All Other Corporate Bonds 520.4 22.4 113.5 24.5 Redeemable Preferred Stocks 9.5 0.1 — — Total Fixed Maturity Securities $ 762.9 $ 29.0 $ 142.1 $ 26.9
Distribution of the Maturity Dates for Fixed Maturity Securities	The following is a distribution of the maturity dates for fixed maturity securities. The maturity dates have not been adjusted for possible calls or prepayments. March 31, 2021 Amortized Cost, Net of ACL Unrealized Gain Position Unrealized Loss Position Gross Gain Fair Value Gross Loss Fair Value (in millions of dollars) 1 year or less $ 777.5 $ 16.7 $ 731.2 $ 1.6 $ 61.4 Over 1 year through 5 years 6,304.4 581.8 6,672.8 16.2 197.2 Over 5 years through 10 years 10,695.5 1,531.9 11,529.8 23.1 674.5 Over 10 years 17,929.6 3,491.1 18,771.3 136.7 2,512.7 35,707.0 5,621.5 37,705.1 177.6 3,445.8 Mortgage/Asset-Backed Securities 851.6 73.6 921.4 0.1 3.7 Total Fixed Maturity Securities $ 36,558.6 $ 5,695.1 $ 38,626.5 $ 177.7 $ 3,449.5 December 31, 2020 Amortized Cost, Net of ACL Unrealized Gain Position Unrealized Loss Position Gross Gain Fair Value Gross Loss Fair Value (in millions of dollars) 1 year or less $ 881.8 $ 19.5 $ 836.4 $ 2.9 $ 62.0 Over 1 year through 5 years 6,162.6 589.9 6,545.7 22.9 183.9 Over 5 years through 10 years 10,886.9 1,914.8 12,659.4 10.7 131.6 Over 10 years 17,588.5 5,041.3 22,089.2 19.2 521.4 35,519.8 7,565.5 42,130.7 55.7 898.9 Mortgage/Asset-Backed Securities 1,019.9 88.0 1,101.6 0.2 6.1 Total Fixed Maturity Securities $ 36,539.7 $ 7,653.5 $ 43,232.3 $ 55.9 $ 905.0
Distribution by External Credit Rating for Fixed Maturity Securities	The following chart depicts an analysis of our fixed maturity security portfolio between investment-grade and below-investment-grade categories as of March 31, 2021: Gross Unrealized Loss Fair Value Gross Unrealized Gain Amount Percent of Total Gross Unrealized Loss (in millions of dollars) Investment-Grade $ 38,846.3 $ 5,451.1 $ 149.9 84.4 % Below-Investment-Grade 3,229.7 244.0 27.8 15.6 Total Fixed Maturity Securities $ 42,076.0 $ 5,695.1 $ 177.7 100.0 %
Debt Securities, Available-for-sale, Allowance for Credit Loss	The following table presents a rollforward of the allowance for credit losses on available-for-sale fixed maturity securities, all of which are classified as "all other corporate bonds" in the preceding tables, at March 31, 2021: Three Months Ended March 31 2021 2020 (in millions of dollars) Balance, beginning of period $ 6.8 $ — Credit losses on securities for which credit losses were not previously recorded — 48.0 Change in allowance on securities with allowance recorded in previous period 0.5 — Balance, end of period $ 7.3 $ 48.0
Low Income Housing Tax Credits	The Company invests in tax credit partnerships primarily for the receipt of income tax credits and tax benefits derived from passive losses on the investments. Amounts recognized in the consolidated statements of income are as follows: Three Months Ended March 31 2021 2020 (in millions of dollars) Income Tax Credits $ 5.4 $ 8.3 Amortization, Net of Tax (3.7) (5.5) Income Tax Benefit $ 1.7 $ 2.8
Mortgage Loans by Property Type and Geographic Region	The carrying amount of mortgage loans by property type and geographic region are presented below. March 31, 2021 December 31, 2020 (in millions of dollars) Carrying Amount Percent of Total Carrying Amount Percent of Total Property Type Apartment $ 648.2 27.0 % $ 638.0 26.2 % Industrial 650.6 27.1 654.0 26.9 Office 490.8 20.4 517.8 21.3 Retail 566.1 23.6 575.6 23.7 Other 46.5 1.9 46.7 1.9 Total $ 2,402.2 100.0 % $ 2,432.1 100.0 % Region New England $ 35.1 1.5 % $ 40.0 1.6 % Mid-Atlantic 200.6 8.4 202.5 8.2 East North Central 310.4 12.9 330.4 13.6 West North Central 194.3 8.1 196.1 8.1 South Atlantic 510.4 21.2 512.0 21.1 East South Central 109.1 4.5 110.0 4.5 West South Central 255.3 10.6 257.4 10.6 Mountain 276.3 11.5 268.8 11.1 Pacific 510.7 21.3 514.9 21.2 Total $ 2,402.2 100.0 % $ 2,432.1 100.0 %
Schedule of Participating Mortgage Loans by Internal Credit Rating and Loan to Value	The following tables present information about mortgage loans by the applicable credit quality indicators: March 31, 2021 December 31, 2020 (in millions of dollars) Carrying Amount Percent of Total Carrying Amount Percent of Total Internal Rating AA $ 3.4 0.1 % $ 3.5 0.1 % A 533.7 22.2 510.0 21.0 BBB 1,810.0 75.3 1,863.0 76.6 BB 39.1 1.6 39.4 1.6 B 16.0 0.8 16.2 0.7 Total $ 2,402.2 100.0 % $ 2,432.1 100.0 % Loan-to-Value Ratio <= 65% $ 1,180.4 49.1 % $ 1,189.4 48.9 % > 65% <= 75% 986.5 41.1 1,000.3 41.1 > 75% <= 85% 156.1 6.5 155.8 6.4 > 85% 79.2 3.3 86.6 3.6 Total $ 2,402.2 100.0 % $ 2,432.1 100.0 %
Mortgage Loans by Credit Quality Indicators	The followin g table presents the amortized cost of our mortgage loans by year of origination and credit quality indicators at March 31, 2021 : Prior to 2017 2017 2018 2019 2020 2021 Total (in millions of dollars) Internal Rating AA $ 3.4 $ — $ — $ — $ — $ — $ 3.4 A 376.2 60.3 63.8 16.7 17.9 — 534.9 BBB 705.0 241.0 326.3 350.2 165.7 31.6 1,819.8 BB 29.2 10.4 — — — — 39.6 B 16.0 — — — — — 16.0 Total Amortized Cost 1,129.8 311.7 390.1 366.9 183.6 31.6 2,413.7 Allowance for credit losses (3.9) (1.6) (2.1) (2.4) (1.4) (0.1) (11.5) Carrying Amount $ 1,125.9 $ 310.1 $ 388.0 $ 364.5 $ 182.2 $ 31.5 $ 2,402.2 Loan-to-Value Ratio <=65% $ 821.9 $ 131.2 $ 90.6 $ 82.3 $ 37.2 $ 20.2 $ 1,183.4 >65<=75% 161.1 109.2 280.1 284.6 146.4 11.4 992.8 >75%<=85% 106.4 37.6 13.3 — — — 157.3 >85% 40.4 33.7 6.1 — — — 80.2 Total Amortized Cost 1,129.8 311.7 390.1 366.9 183.6 31.6 2,413.7 Allowance for credit losses (3.9) (1.6) (2.1) (2.4) (1.4) (0.1) (11.5) Carrying Amount $ 1,125.9 $ 310.1 $ 388.0 $ 364.5 $ 182.2 $ 31.5 $ 2,402.2
Financing Receivable, Allowance for Credit Loss	The following table presents a roll-forward of allowance for expected credit losses by loan-to-value ratio: Three Months Ended March 31, 2021 Beginning of Year Current Period Provisions Write-Offs Recoveries End of Period (in millions of dollars) Loan-to-Value Ratio <=65% $ 3.4 $ (0.4) $ — $ — $ 3.0 >65<=75% 7.3 (1.0) — — 6.3 >75%<=85% 1.3 (0.1) — — 1.2 >85% 1.1 (0.1) — — 1.0 Total $ 13.1 $ (1.6) $ — $ — $ 11.5 Three Months Ended March 31, 2020 Beginning of Year Current Period Provisions Write-Offs Recoveries End of Period (in millions of dollars) Loan-to-Value Ratio <=65% $ 2.8 $ 0.7 $ — $ — $ 3.5 >65<=75% 4.6 1.9 — — 6.5 >75%<=85% 0.5 (0.1) — — 0.4 >85% 0.4 0.3 — — 0.7 Total $ 8.3 $ 2.8 $ — $ — $ 11.1
Remaining Contractual Maturity of Securities Lending Agreements	The remaining contractual maturities of our securities lending agreements disaggregated by class of collateral pledged are as follows: March 31, 2021 December 31, 2020 Overnight and Continuous (in millions of dollars) Borrowings United States Government and Government Agencies and Authorities $ 0.1 $ 0.1 State, Municipalities, and Political Subdivisions 0.4 0.4 Public Utilities 0.5 0.3 All Other Corporate Bonds 42.5 16.8 Total Borrowings $ 43.5 $ 17.6 Gross Amount of Recognized Liability for Securities Lending Transactions 43.5 17.6 Amounts Related to Agreements Not Included in Offsetting Disclosure Contained Herein $ — $ —
Federal Home Loan Bank Common Stock Carrying Amounts, Amounts Posted, and Advances Received	The carrying value of common stock owned, collateral posted, and advances received are as follows: March 31, 2021 December 31, 2020 (in millions of dollars) Carrying Value of FHLB Common Stock $ 26.9 $ 28.2 Advances from FHLB $ 302.2 $ 312.2 Carrying Value of Collateral Posted to FHLB Fixed Maturity Securities $ 857.9 $ 944.0 Commercial Mortgage Loans 982.1 1,072.5 Total Carrying Value of Collateral Posted to FHLB $ 1,840.0 $ 2,016.5
Schedule of Financial Instrument and Derivative Offsetting	Shown below are our financial instruments that either meet the accounting requirements that allow them to be offset in our balance sheets or that are subject to an enforceable master netting arrangement or similar agreement. Our accounting policy is to not offset these financial instruments in our balance sheets. Net amounts disclosed below have been reduced by the amount of collateral pledged to or received from our counterparties. March 31, 2021 Gross Amount Gross Amount Not of Recognized Gross Amount Net Amount Offset in Balance Sheet Financial Offset in Presented in Financial Cash Net Instruments Balance Sheet Balance Sheet Instruments Collateral Amount (in millions of dollars) Financial Assets: Derivatives $ 17.6 $ — $ 17.6 $ (9.9) $ (7.7) $ — Securities Lending 220.0 — 220.0 (176.5) (43.5) — Total $ 237.6 $ — $ 237.6 $ (186.4) $ (51.2) $ — Financial Liabilities: Derivatives $ 54.9 $ — $ 54.9 $ (54.6) $ — $ 0.3 Securities Lending 43.5 — 43.5 (43.5) — — Total $ 98.4 $ — $ 98.4 $ (98.1) $ — $ 0.3 December 31, 2020 Gross Amount Gross Amount Not of Recognized Gross Amount Net Amount Offset in Balance Sheet Financial Offset in Presented in Financial Cash Net Instruments Balance Sheet Balance Sheet Instruments Collateral Amount (in millions of dollars) Financial Assets: Derivatives $ 19.8 $ — $ 19.8 $ (10.1) $ (8.7) $ 1.0 Securities Lending 96.6 — 96.6 (79.0) (17.6) — Total $ 116.4 $ — $ 116.4 $ (89.1) $ (26.3) $ 1.0 Financial Liabilities: Derivatives $ 59.7 $ — $ 59.7 $ (59.0) $ — $ 0.7 Securities Lending 17.6 — 17.6 (17.6) — — Total $ 77.3 $ — $ 77.3 $ (76.6) $ — $ 0.7
Net Investment Income	Net Investment Income Net investment income reported in our consolidated statements of income is presented below. Three Months Ended March 31 2021 2020 (in millions of dollars) Fixed Maturity Securities $ 469.8 $ 539.8 Derivatives 16.2 20.2 Mortgage Loans 26.3 29.0 Policy Loans 4.8 4.8 Other Long-term Investments Perpetual Preferred Securities 1 3.6 (17.1) Private Equity Partnerships 2 35.9 10.4 Other 2.1 3.2 Short-term Investments 0.6 6.4 Gross Investment Income 559.3 596.7 Less Investment Expenses 7.5 8.5 Less Investment Income on Participation Fund Account Assets 3.1 3.2 Net Investment Income $ 548.7 $ 585.0 1 The net unrealized gain (loss) recognized in net investment income for the three months ended March 31, 2021 related to perpetual preferred securities still held at March 31, 2021 was $2.7 million. The net unrealized loss recognized in net investment income for the three months ended March 31, 2020 related to perpetual preferred securities still held at March 31, 2020 was $17.9 million.
Realized Investment Gains and Losses Reported in Consolidated Statements of Income	Realized Investment Gain and Loss Realized investment gains and losses are as follows: Three Months Ended March 31 2021 2020 (in millions of dollars) Fixed Maturity Securities Gross Gains on Sales 1 $ 71.3 $ 1.4 Gross Losses on Sales (1.1) (0.7) Credit Losses (8.3) (53.9) Mortgage Loans and Other Invested Assets Gross Gains on Sales 2.5 0.3 Gross Losses on Sales — (0.2) Credit Losses 1.7 (2.6) Embedded Derivative in Modified Coinsurance Arrangement 16.9 (86.9) All Other Derivatives 1.7 (0.7) Foreign Currency Transactions (0.1) (0.7) Net Realized Investment Gain (Loss) $ 84.6 $ (144.0) 1 Gross gains on sales of fixed maturity securities includes gains of $67.6 million as a result of the second phase of the reinsurance transaction that we completed during the first quarter of 2021. See Note 12 for further discussion.

Derivative Financial Instrume_2

Derivative Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 2021
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Nature and Amount of Collateral Received From and Posted To Derivative Counterparty	The table below summarizes the nature and amount of collateral received from and posted to our derivative counterparties. March 31, 2021 December 31, 2020 (in millions of dollars) Carrying Value of Collateral Received from Counterparties Cash $ 8.8 $ 8.7 Carrying Value of Collateral Posted to Counterparties Fixed Maturity Securities $ 46.8 $ 54.0
Notional Amounts for Each Category of Derivative Activity	The table below summarizes, by notional amounts, the activity for each category of derivatives. The notional amounts represent the basis upon which our counterparty pay and receive amounts are calculated. Swaps Receive Receive Credit Default Total Forwards Total (in millions of dollars) Balance at December 31, 2019 $ 611.1 $ 250.0 $ 11.4 $ — $ 8.9 $ 881.4 Additions 52.0 — — — — 52.0 Terminations — — — — 1.3 1.3 Foreign Currency — — (0.7) — — (0.7) Balance at March 31, 2020 $ 663.1 $ 250.0 $ 10.7 $ — $ 7.6 $ 931.4 Balance at December 31, 2020 $ 720.8 $ — $ 11.7 $ — $ 11.9 $ 744.4 Additions 26.2 — — 75.5 — 101.7 Foreign Currency — — 0.2 — — 0.2 Balance at March 31, 2021 $ 747.0 $ — $ 11.9 $ 75.5 $ 11.9 $ 846.3
Fair Value Hedges Carrying Amount of Hedged Assets and Liabilities and Cumulative Basis Adjustments	The following table summarizes the carrying amount of hedged assets and the related cumulative basis adjustments related to our fair value hedges: Carrying Amount of Hedged Assets Cumulative Amount of Fair Value Hedging Adjustment Included in the Carrying Amount of the Hedged Assets March 31, 2021 December 31, 2020 March 31, 2021 December 31, 2020 (in millions of dollars) Fixed maturity securities: Receive fixed functional currency interest, pay fixed foreign currency interest $ 405.6 $ 404.5 $ 14.9 $ 24.4
Location and Fair Values of Derivative Financial Instruments	The following tables summarize the location and fair values of derivative financial instruments, as reported in our consolidated balance sheets. March 31, 2021 Derivative Assets Derivative Liabilities Balance Sheet Fair Balance Sheet Fair (in millions of dollars) Designated as Hedging Instruments Cash Flow Hedges Foreign Exchange Contracts Other L-T Investments $ 15.4 Other Liabilities $ 10.1 Fair Value Hedges Foreign Exchange Contracts Other L-T Investments 2.0 Other Liabilities 22.2 Total Designated as Hedging Instruments $ 17.4 $ 32.3 Not Designated as Hedging Instruments Credit Default Swaps Other L-T Investments $ 0.1 Other Liabilities $ — Forwards Other L-T Investments 0.1 Other Liabilities 0.1 Foreign Exchange Contracts Other L-T Investments — Other Liabilities 22.5 Embedded Derivative in Modified Coinsurance Arrangement Other L-T Investments — Other Liabilities 22.9 Total Not Designated as Hedging Instruments $ 0.2 $ 45.5 December 31, 2020 Derivative Assets Derivative Liabilities Balance Sheet Fair Balance Sheet Fair (in millions of dollars) Designated as Hedging Instruments Cash Flow Hedges Foreign Exchange Contracts Other L-T Investments $ 16.4 Other Liabilities $ 9.4 Fair Value Hedges Foreign Exchange Contracts Other L-T Investments 3.3 Other Liabilities 26.0 Total Designated as Hedging Instruments $ 19.7 $ 35.4 Not Designated as Hedging Instruments Credit Default Swaps Other L-T Investments $ 0.1 Other Liabilities $ — Forwards Other L-T Investments — Other Liabilities 0.5 Foreign Exchange Contracts Other L-T Investments — Other Liabilities 23.8 Embedded Derivative in Modified Coinsurance Arrangement Other L-T Investments — Other Liabilities 39.8 Total Not Designated as Hedging Instruments $ 0.1 $ 64.1
Location of Gains and Losses on Derivative Instruments Designated as Cash Flow Hedging Instruments	The following tables summarize the location of gains and losses of derivative financial instruments designated as hedging instruments, as reported in our consolidated statements of income. Three Months Ended March 31 2021 2020 Net Investment Income Net Realized Investment Gain (Loss) Interest and Debt Expense Net Investment Income Net Realized Investment Gain (Loss) Interest and Debt Expense (in millions of dollars) Total Income and Expense Presented in the Consolidated Statements of Income of Which Hedged Items are Recorded $ 548.7 $ 84.6 $ 44.4 $ 585.0 $ (144.0) $ 45.7 Gain (Loss) on Cash Flow Hedging Relationships Interest Rate Swaps: Hedged items 52.0 2.4 7.3 73.0 — 7.3 Derivatives Designated as Hedging Instruments 15.5 1.8 0.1 19.2 — 0.6 Foreign Exchange Contracts: Hedged items 3.1 — — 2.9 — — Derivatives Designated as Hedging Instruments 0.3 — — 0.9 — — Gain (Loss) on Fair Value Hedging Relationships Interest Rate Swaps: Hedged items — — — — (1.5) 3.6 Derivatives Designated as Hedging Instruments — — — — 1.5 0.1 Foreign Exchange Contracts Hedged items 2.3 (9.5) — 1.4 (13.2) — Derivatives Designated as Hedging Instruments 1.0 9.5 — 0.8 13.2 —
Schedule of Cash Flow Hedges Included in Accumulated Other Comprehensive Income (Loss)	The following table summarizes the location of gains and losses of derivative financial instruments designated as cash flow hedging instruments, as reported in our consolidated statements of comprehensive income (loss). Three Months Ended March 31 2021 2020 (in millions of dollars) Gain (Loss) Recognized in Other Comprehensive Income (Loss) on Derivatives Foreign Exchange Contracts $ (1.5) $ 19.5
Gains and Losses on Derivatives Not Designated as Hedging Instruments	The following table summarizes the location of gains and losses on our derivatives not designated as hedging instruments, as reported in our consolidated statements of income. Three Months Ended March 31 2021 2020 (in millions of dollars) Net Realized Investment Gain (Loss) Credit Default Swaps $ (0.1) $ 0.8 Foreign Exchange Contracts 1.8 (1.5) Embedded Derivative in Modified Coinsurance Arrangement 16.9 (86.9) Total $ 18.6 $ (87.6) Other Expenses Total Return Swaps $ 1.3 $ —

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Income (Loss) (Tables)	3 Months Ended
	Mar. 31, 2021
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss)	Components of our accumulated other comprehensive income (loss), after tax, and related changes are as follows: Net Unrealized Gain on Securities Net Gain on Hedges Foreign Currency Translation Adjustment Unrecognized Pension and Postretirement Benefit Costs Total (in millions of dollars) Balance at December 31, 2020 $ 1,067.7 $ 97.8 $ (261.3) $ (530.0) $ 374.2 Other Comprehensive Income (Loss) Before Reclassifications (447.2) (6.8) 7.3 (0.5) (447.2) Amounts Reclassified from Accumulated Other Comprehensive Income or Loss 57.7 (13.9) — 4.3 48.1 Net Other Comprehensive Income (Loss) (389.5) (20.7) 7.3 3.8 (399.1) Balance at March 31, 2021 $ 678.2 $ 77.1 $ (254.0) $ (526.2) $ (24.9) Balance at December 31, 2019 $ 615.9 $ 187.8 $ (281.6) $ (484.8) $ 37.3 Other Comprehensive Income (Loss) Before Reclassifications (263.2) 37.7 (63.6) 3.1 (286.0) Amounts Reclassified from Accumulated Other Comprehensive Income or Loss 42.6 (14.9) — 3.9 31.6 Net Other Comprehensive Income (Loss) (220.6) 22.8 (63.6) 7.0 (254.4) Balance at March 31, 2020 $ 395.3 $ 210.6 $ (345.2) $ (477.8) $ (217.1)
Schedule of Components of Unrealized Gain (Loss) on Securities	The net unrealized gain on securities consists of the following components: March 31 December 31 2021 2020 Change (in millions of dollars) Fixed Maturity Securities $ 5,517.4 $ 7,597.6 $ (2,080.2) Deferred Acquisition Costs (66.6) (85.1) 18.5 Reserves for Future Policy and Contract Benefits (4,588.9) (6,225.6) 1,636.7 Reinsurance Recoverable 133.3 200.2 (66.9) Income Tax (317.0) (419.4) 102.4 Total $ 678.2 $ 1,067.7 $ (389.5) March 31 December 31 2020 2019 Change (in millions of dollars) Fixed Maturity Securities $ 4,261.2 $ 6,364.4 $ (2,103.2) Deferred Acquisition Costs (37.4) (62.7) 25.3 Reserves for Future Policy and Contract Benefits (3,899.5) (5,803.1) 1,903.6 Reinsurance Recoverable 322.7 424.7 (102.0) Income Tax (251.7) (307.4) 55.7 Total $ 395.3 $ 615.9 $ (220.6)
Schedule of Reclassification out of Accumulated Other Comprehensive Income (Loss)	Amounts reclassified from accumulated other comprehensive income (loss) were recognized in our consolidated statements of income as follows: Three Months Ended March 31 2021 2020 (in millions of dollars) Net Unrealized Gain on Securities Net Realized Investment Gain (Loss) Gain on Sales of Securities $ 68.3 $ — Credit Losses on Fixed Maturity Securities (8.3) (53.9) Loss on Benefits and Change in Reserves for Future Benefits (133.1) — (73.1) (53.9) Income Tax Benefit (15.4) (11.3) Total $ (57.7) $ (42.6) Net Gain on Hedges Net Investment Income Gain on Interest Rate Swaps and Forwards $ 15.3 $ 18.8 Gain on Foreign Exchange Contracts 0.5 0.5 Net Realized Investment Gain Gain on Interest Rate Swaps 1.8 — Interest and Debt Expense Loss on Interest Rate Swaps — (0.6) 17.6 18.7 Income Tax Expense 3.7 3.8 Total $ 13.9 $ 14.9 Unrecognized Pension and Postretirement Benefit Costs Other Expenses Amortization of Net Actuarial Loss $ (5.6) $ (5.0) Amortization of Prior Service Credit 0.1 0.1 (5.5) (4.9) Income Tax Benefit (1.2) (1.0) Total $ (4.3) $ (3.9)

Liability for Unpaid Claims a_2

Liability for Unpaid Claims and Claim Adjustment Expenses (Tables)	3 Months Ended
	Mar. 31, 2021
Insurance [Abstract]
Schedule of Liability for Unpaid Claims and Claims Adjustment Expense	Changes in the liability for unpaid claims and claim adjustment expenses are as follows: 2021 2020 (in millions of dollars) Balance at January 1 $ 24,180.2 $ 23,076.7 Less Reinsurance Recoverable 8,378.9 2,246.8 Net Balance at January 1 15,801.3 20,829.9 Incurred Related to Current Year 1,782.0 1,605.9 Prior Years Interest 183.4 271.9 All Other Incurred (55.9) (126.7) Foreign Currency 17.3 (127.6) Total Incurred 1,926.8 1,623.5 Paid Related to Current Year (409.2) (368.0) Prior Years (1,327.2) (1,453.7) Total Paid (1,736.4) (1,821.7) Reserves Ceded Pursuant to Reinsurance Transaction (990.0) — Net Balance at March 31 15,001.7 20,631.7 Plus Reinsurance Recoverable 9,225.8 2,260.7 Balance at March 31 $ 24,227.5 $ 22,892.4
Reconciliation of Policy and Contract Benefits and Reserves for Future Policy and Contract Benefits to Balance Sheet Amounts	A reconciliation of policy and contract benefits and reserves for future policy and contract benefits as reported in our consolidated balance sheets to the liability for unpaid claims and claim adjustment expenses is as follows: March 31 2021 2020 (in millions of dollars) Policy and Contract Benefits $ 1,899.3 $ 1,760.3 Reserves for Future Policy and Contract Benefits 48,112.3 45,706.5 Total 50,011.6 47,466.8 Less: Life Reserves for Future Policy and Contract Benefits 8,389.3 8,428.5 Accident and Health Active Life Reserves 12,805.9 12,246.4 Adjustment Related to Unrealized Investment Gains and Losses 4,588.9 3,899.5 Liability for Unpaid Claims and Claim Adjustment Expenses $ 24,227.5 $ 22,892.4

Segment Information (Tables)

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2021
Segment Reporting [Abstract]
Premium Income by Major Line of Business within Each Segment	Segment information is as follows: Three Months Ended March 31 2021 2020 (in millions of dollars) Premium Income Unum US Group Disability Group Long-term Disability $ 457.7 $ 463.0 Group Short-term Disability 215.2 203.2 Group Life and Accidental Death & Dismemberment Group Life 410.0 414.5 Accidental Death & Dismemberment 41.4 41.7 Supplemental and Voluntary Individual Disability 115.7 109.5 Voluntary Benefits 218.7 230.4 Dental and Vision 67.1 65.4 1,525.8 1,527.7 Unum International Unum UK Group Long-term Disability 97.1 90.8 Group Life 27.3 30.9 Supplemental 28.0 23.9 Unum Poland 22.0 19.0 174.4 164.6 Colonial Life Accident, Sickness, and Disability 240.7 249.3 Life 96.6 93.8 Cancer and Critical Illness 89.1 91.6 426.4 434.7 Closed Block Long-term Care 177.4 164.8 Individual Disability 72.1 77.0 All Other 2.2 2.6 251.7 244.4 Total Premium Income $ 2,378.3 $ 2,371.4
Selected Operating Statement Data by Segment	Unum US Unum International Colonial Life Closed Block Corporate Total (in millions of dollars) Three Months Ended March 31, 2021 Premium Income $ 1,525.8 $ 174.4 $ 426.4 $ 251.7 $ — $ 2,378.3 Net Investment Income 179.7 26.0 37.7 297.2 8.1 548.7 Other Income 40.4 0.1 0.2 18.4 1.3 60.4 Adjusted Operating Revenue $ 1,745.9 $ 200.5 $ 464.3 $ 567.3 $ 9.4 $ 2,987.4 Adjusted Operating Income (Loss) $ 115.7 $ 26.4 $ 73.3 $ 97.0 $ (38.9) $ 273.5 Three Months Ended March 31, 2020 Premium Income $ 1,527.7 $ 164.6 $ 434.7 $ 244.4 $ — $ 2,371.4 Net Investment Income 179.6 26.5 37.7 336.1 5.1 585.0 Other Income 40.2 — 0.3 18.2 — 58.7 Adjusted Operating Revenue $ 1,747.5 $ 191.1 $ 472.7 $ 598.7 $ 5.1 $ 3,015.1 Adjusted Operating Income (Loss) $ 261.8 $ 19.4 $ 81.1 $ 29.7 $ (45.9) $ 346.1
Assets by Segment	March 31 December 31 2021 2020 (in millions of dollars) Assets Unum US $ 18,563.1 $ 19,034.2 Unum International 4,163.6 4,206.2 Colonial Life 4,817.3 4,864.3 Closed Block 37,845.1 38,187.2 Corporate 3,867.5 4,333.9 Total Assets $ 69,256.6 $ 70,625.8
Reconciliation of Total Revenue and Income Before Income Tax to Adjusted Operating Revenue and Adjusted Operating Income	A reconciliation of total revenue to "adjusted operating revenue" and income before income tax to "adjusted operating income" is as follows: Three Months Ended March 31 2021 2020 (in millions of dollars) Total Revenue $ 3,072.0 $ 2,871.1 Excluding: Net Realized Investment Gain (Loss) 84.6 (144.0) Adjusted Operating Revenue $ 2,987.4 $ 3,015.1 Income Before Income Tax $ 198.8 $ 202.1 Excluding: Net Realized Investment Gains and Losses Net Realized Investment Gain Related to Reinsurance Transaction 67.6 — Net Realized Investment Gain (Loss), Other 17.0 (144.0) Total Net Realized Investment Gain (Loss) 84.6 (144.0) Items Related to Closed Block Individual Disability Reinsurance Transaction Change in Benefit Reserves and Transaction Costs (139.3) — Amortization of the Cost of Reinsurance (20.0) — Total Items Related to Closed Block Individual Disability Reinsurance Transaction (159.3) — Adjusted Operating Income $ 273.5 $ 346.1

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	3 Months Ended
	Mar. 31, 2021
Defined Benefit Plans and Other Postretirement Benefit Plans
Schedule of Net Benefit Costs	The following table provides the components of the net periodic benefit cost (credit) for the defined benefit pension and OPEB plans. Three Months Ended March 31 Pension Benefits U.S. Plans U.K. Plan OPEB 2021 2020 2021 2020 2021 2020 (in millions of dollars) Service Cost $ 2.4 $ 2.8 $ — $ — $ — $ — Interest Cost 16.3 18.2 1.1 1.2 0.8 1.0 Expected Return on Plan Assets (25.2) (26.7) (2.5) (2.4) (0.1) (0.1) Amortization of: Net Actuarial Loss 5.3 4.7 0.3 0.3 — — Prior Service Credit — — — — (0.1) (0.1) Total Net Periodic Benefit Cost (Credit) $ (1.2) $ (1.0) $ (1.1) $ (0.9) $ 0.6 $ 0.8

Stockholders' Equity and Earn_2

Stockholders' Equity and Earnings Per Common Share (Tables)	3 Months Ended
	Mar. 31, 2021
Stockholders' Equity and Earnings Per Common Share [Abstract]
Schedule of Basic and Diluted Earnings Per Share	Net income per common share is determined as follows: Three Months Ended March 31 2021 2020 (in millions of dollars, except share data) Numerator Net Income $ 153.0 $ 161.0 Denominator (000s) Weighted Average Common Shares - Basic 204,133.3 203,306.0 Dilution for Assumed Exercises of Stock Options and Nonvested Stock Awards 604.0 49.7 Weighted Average Common Shares - Assuming Dilution 204,737.3 203,355.7 Net Income Per Common Share Basic $ 0.75 $ 0.79 Assuming Dilution $ 0.75 $ 0.79

Accounting Developments Additio

Accounting Developments Additional Information (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020	Jan. 01, 2020
New Accounting Pronouncements or Change in Accounting Principle
Retained Earnings	$ (11,363.2)	$ (11,269.6)
Accounting Standards Update 2016-13 | Restatement Adjustment
New Accounting Pronouncements or Change in Accounting Principle
Retained Earnings			$ 18.9

Fair Values of Financial Inst_3

Fair Values of Financial Instruments Private Equity Partnerships (Details) - Private Equity Funds - USD ($) $ in Millions		Mar. 31, 2021	Dec. 31, 2020
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share
Alternative Investments		$ 792.4	$ 747.5
Alternative Investments, Unfunded Commitments		641	590.7
Private Credit
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share
Alternative Investments	[1]	289.4	273.7
Alternative Investments, Unfunded Commitments		191.4	180.2
Private Credit | Not Redeemable
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share
Alternative Investments	[1]	247.5	233.3
Alternative Investments, Unfunded Commitments		190.3	178.9
Private Credit | Initial 2 year lock on each new investment / Quarterly after 2 year lock with 90 days notice
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share
Alternative Investments	[1]	41.9	40.4
Alternative Investments, Unfunded Commitments		1.1	1.3
Private Equity Limited Partnership
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share
Alternative Investments		259	241.8
Alternative Investments, Unfunded Commitments		250.7	225.3
Private Equity Limited Partnership | Not Redeemable
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share
Alternative Investments	[2]	249.8	232.6
Alternative Investments, Unfunded Commitments		216.4	191
Private Equity Limited Partnership | Quarterly after 5.5 year lock with 90 days notice
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share
Alternative Investments		9.2	9.2
Alternative Investments, Unfunded Commitments		34.3	34.3
Real Assets
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share
Alternative Investments	[3]	244	232
Alternative Investments, Unfunded Commitments		198.9	185.2
Real Assets | Not Redeemable
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share
Alternative Investments	[3]	187.7	176.3
Alternative Investments, Unfunded Commitments		198.9	185.2
Real Assets | Quarterly / 90 days notice
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share
Alternative Investments	[3]	56.3	55.7
Alternative Investments, Unfunded Commitments		$ 0	$ 0
[1]	Private Credit - The limited partnerships described in this category employ various investment strategies, generally providing direct lending or other forms of debt financing including first-lien, second-lien, mezzanine, and subordinated loans. The limited partnerships have credit exposure to corporates, physical assets, and/or financial assets within a variety of industries (including manufacturing, healthcare, energy, business services, technology, materials, and retail) in North America and, to a lesser extent, outside of North America. As of March 31, 2021, the estimated remaining life of the investments that do not allow for redemptions is approximately 34 percent in the next 3 years, 51 percent during the period from 3 to 5 years, 13 percent during the period from 5 to 10 years, and 2 percent during the period from 10 to 15 years.
[2]	Private Equity - The limited partnerships described in this category employ various strategies generally investing in controlling or minority control equity positions directly in companies and/or assets across various industries (including manufacturing, healthcare, energy, business services, technology, materials, and retail), primarily in private markets within North America and, to a lesser extent, outside of North America. As of March 31, 2021, the estimated remaining life of the investments that do not allow for redemptions is approximately 21 percent in the next 3 years, 34 percent during the period from 3 to 5 years, 44 percent during the period from 5 to 10 years, and 1 percent during the period from 10 to 15 years.
[3]	Real Assets - The limited partnerships described in this category employ various strategies, which include investing in the equity and/or debt financing of physical assets, including infrastructure (energy, power, water/wastewater, communications), transportation (including airports, ports, toll roads, aircraft, railcars) and real estate in North America, Europe, South America, and Asia. As of March 31, 2021, the estimated remaining life of the investments that do not allow for redemptions is approximately 11 percent in the next 3 years, 21 percent during period from 3 to 5 years and 68 percent during the period from 5 to 10 years.

Fair Value Measurements by Inpu

Fair Value Measurements by Input Level (Detail) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Fixed Maturity Securities
Fixed Maturity Securities	$ 42,076	$ 44,137.3
Derivative Assets	17.6	19.8
Equity Securities	31.5	28.3
Other Long-term Investments	995.3	960.2
Assets, Fair Value Disclosure	42,917.5	44,932.9
Liabilities
Derivative Liabilities	77.8	99.5
Liabilities, Fair Value Disclosure	77.8	99.5
Interest Rate Swaps
Liabilities
Derivative Liabilities	0.1	0.5
Foreign Exchange Contracts
Liabilities
Derivative Liabilities	54.8	59.2
Embedded Derivative in Modified Coinsurance Arrangement
Liabilities
Derivative Liabilities	22.9	39.8
Fair Value, Measurements, Recurring
Fixed Maturity Securities
Other Long-term Investments	841.5	795.6
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Fixed Maturity Securities
Fixed Maturity Securities	9,893.8	4,221.3
Derivative Assets	0	0
Equity Securities	26.1	8.4
Other Long-term Investments	26.1	8.4
Assets, Fair Value Disclosure	9,919.9	4,229.7
Liabilities
Liabilities, Fair Value Disclosure	0	0
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1 | Interest Rate Swaps
Liabilities
Derivative Liabilities	0	0
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1 | Foreign Exchange Contracts
Liabilities
Derivative Liabilities	0	0
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1 | Embedded Derivative in Modified Coinsurance Arrangement
Liabilities
Derivative Liabilities	0	0
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Fixed Maturity Securities
Fixed Maturity Securities	31,480.7	38,668.6
Derivative Assets	17.6	19.8
Equity Securities	0.2	15.2
Other Long-term Investments	17.8	35
Assets, Fair Value Disclosure	31,498.5	38,703.6
Liabilities
Liabilities, Fair Value Disclosure	54.9	59.7
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | Interest Rate Swaps
Liabilities
Derivative Liabilities	0.1	0.5
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | Foreign Exchange Contracts
Liabilities
Derivative Liabilities	54.8	59.2
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | Embedded Derivative in Modified Coinsurance Arrangement
Liabilities
Derivative Liabilities	0	0
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fixed Maturity Securities
Fixed Maturity Securities	701.5	1,247.4
Derivative Assets	0	0
Equity Securities	5.2	4.7
Other Long-term Investments	5.2	4.7
Assets, Fair Value Disclosure	706.7	1,252.1
Liabilities
Liabilities, Fair Value Disclosure	22.9	39.8
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3 | Interest Rate Swaps
Liabilities
Derivative Liabilities	0	0
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3 | Foreign Exchange Contracts
Liabilities
Derivative Liabilities	0	0
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3 | Embedded Derivative in Modified Coinsurance Arrangement
Liabilities
Derivative Liabilities	22.9	39.8
Fair Value, Measurements, Recurring | Fair Value Measured at Net Asset Value Per Share
Fixed Maturity Securities
Fixed Maturity Securities	0	0
Derivative Assets	0	0
Equity Securities	0	0
Other Long-term Investments	792.4	747.5
Assets, Fair Value Disclosure	792.4	747.5
Liabilities
Liabilities, Fair Value Disclosure	0	0
Fair Value, Measurements, Recurring | Fair Value Measured at Net Asset Value Per Share | Interest Rate Swaps
Liabilities
Derivative Liabilities	0	0
Fair Value, Measurements, Recurring | Fair Value Measured at Net Asset Value Per Share | Foreign Exchange Contracts
Liabilities
Derivative Liabilities	0	0
Fair Value, Measurements, Recurring | Fair Value Measured at Net Asset Value Per Share | Embedded Derivative in Modified Coinsurance Arrangement
Liabilities
Derivative Liabilities	0	0
United States Government and Government Agencies and Authorities
Fixed Maturity Securities
Fixed Maturity Securities	576.6	709.8
United States Government and Government Agencies and Authorities | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Fixed Maturity Securities
Fixed Maturity Securities	101.1	0
United States Government and Government Agencies and Authorities | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Fixed Maturity Securities
Fixed Maturity Securities	475.5	709.8
United States Government and Government Agencies and Authorities | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fixed Maturity Securities
Fixed Maturity Securities	0	0
United States Government and Government Agencies and Authorities | Fair Value, Measurements, Recurring | Fair Value Measured at Net Asset Value Per Share
Fixed Maturity Securities
Fixed Maturity Securities	0	0
States, Municipalities, and Political Subdivisions
Fixed Maturity Securities
Fixed Maturity Securities	4,203.9	4,261.2
States, Municipalities, and Political Subdivisions | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Fixed Maturity Securities
Fixed Maturity Securities	54.1	0
States, Municipalities, and Political Subdivisions | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Fixed Maturity Securities
Fixed Maturity Securities	4,149.8	4,245.7
States, Municipalities, and Political Subdivisions | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fixed Maturity Securities
Fixed Maturity Securities	0	15.5
States, Municipalities, and Political Subdivisions | Fair Value, Measurements, Recurring | Fair Value Measured at Net Asset Value Per Share
Fixed Maturity Securities
Fixed Maturity Securities	0	0
Foreign Governments
Fixed Maturity Securities
Fixed Maturity Securities	1,120.6	1,168.2
Foreign Governments | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Fixed Maturity Securities
Fixed Maturity Securities	0	0
Foreign Governments | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Fixed Maturity Securities
Fixed Maturity Securities	1,098.9	1,146.4
Foreign Governments | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fixed Maturity Securities
Fixed Maturity Securities	21.7	21.8
Foreign Governments | Fair Value, Measurements, Recurring | Fair Value Measured at Net Asset Value Per Share
Fixed Maturity Securities
Fixed Maturity Securities	0	0
Public Utilities
Fixed Maturity Securities
Fixed Maturity Securities	6,444.5	6,962.3
Public Utilities | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Fixed Maturity Securities
Fixed Maturity Securities	594.2	131.9
Public Utilities | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Fixed Maturity Securities
Fixed Maturity Securities	5,746.9	6,644.7
Public Utilities | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fixed Maturity Securities
Fixed Maturity Securities	103.4	185.7
Public Utilities | Fair Value, Measurements, Recurring | Fair Value Measured at Net Asset Value Per Share
Fixed Maturity Securities
Fixed Maturity Securities	0	0
Mortgage/Asset-backed Securities
Fixed Maturity Securities
Fixed Maturity Securities	925.1	1,107.7
Mortgage/Asset-backed Securities | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Fixed Maturity Securities
Fixed Maturity Securities	0	0
Mortgage/Asset-backed Securities | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Fixed Maturity Securities
Fixed Maturity Securities	847.9	1,026.4
Mortgage/Asset-backed Securities | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fixed Maturity Securities
Fixed Maturity Securities	77.2	81.3
Mortgage/Asset-backed Securities | Fair Value, Measurements, Recurring | Fair Value Measured at Net Asset Value Per Share
Fixed Maturity Securities
Fixed Maturity Securities	0	0
Corporate Debt Securities
Fixed Maturity Securities
Fixed Maturity Securities	28,801.2	29,918.6
Corporate Debt Securities | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Fixed Maturity Securities
Fixed Maturity Securities	9,144.4	4,089.4
Corporate Debt Securities | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Fixed Maturity Securities
Fixed Maturity Securities	19,157.6	24,886.1
Corporate Debt Securities | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fixed Maturity Securities
Fixed Maturity Securities	499.2	943.1
Corporate Debt Securities | Fair Value, Measurements, Recurring | Fair Value Measured at Net Asset Value Per Share
Fixed Maturity Securities
Fixed Maturity Securities	0	0
Redeemable Preferred Stocks
Fixed Maturity Securities
Fixed Maturity Securities	4.1	9.5
Redeemable Preferred Stocks | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Fixed Maturity Securities
Fixed Maturity Securities	0	0
Redeemable Preferred Stocks | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Fixed Maturity Securities
Fixed Maturity Securities	4.1	9.5
Redeemable Preferred Stocks | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fixed Maturity Securities
Fixed Maturity Securities	0	0
Redeemable Preferred Stocks | Fair Value, Measurements, Recurring | Fair Value Measured at Net Asset Value Per Share
Fixed Maturity Securities
Fixed Maturity Securities	0	0
Forwards
Fixed Maturity Securities
Derivative Assets	0.1
Forwards | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Fixed Maturity Securities
Derivative Assets	0
Forwards | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Fixed Maturity Securities
Derivative Assets	0.1
Forwards | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fixed Maturity Securities
Derivative Assets	0
Forwards | Fair Value, Measurements, Recurring | Fair Value Measured at Net Asset Value Per Share
Fixed Maturity Securities
Derivative Assets	0
Foreign Exchange Contracts
Fixed Maturity Securities
Derivative Assets	17.4	19.7
Foreign Exchange Contracts | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Fixed Maturity Securities
Derivative Assets	0	0
Foreign Exchange Contracts | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Fixed Maturity Securities
Derivative Assets	17.4	19.7
Foreign Exchange Contracts | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fixed Maturity Securities
Derivative Assets	0	0
Foreign Exchange Contracts | Fair Value, Measurements, Recurring | Fair Value Measured at Net Asset Value Per Share
Fixed Maturity Securities
Derivative Assets	0	0
Credit Default Swaps
Fixed Maturity Securities
Derivative Assets	0.1	0.1
Credit Default Swaps | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Fixed Maturity Securities
Derivative Assets	0	0
Credit Default Swaps | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Fixed Maturity Securities
Derivative Assets	0.1	0.1
Credit Default Swaps | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fixed Maturity Securities
Derivative Assets	0	0
Credit Default Swaps | Fair Value, Measurements, Recurring | Fair Value Measured at Net Asset Value Per Share
Fixed Maturity Securities
Derivative Assets	0	0
Private Equity Funds
Fixed Maturity Securities
Alternative Investments	792.4	747.5
Private Equity Funds | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Fixed Maturity Securities
Alternative Investments	0	0
Private Equity Funds | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Fixed Maturity Securities
Alternative Investments	0	0
Private Equity Funds | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fixed Maturity Securities
Alternative Investments	0	0
Private Equity Funds | Fair Value, Measurements, Recurring | Fair Value Measured at Net Asset Value Per Share
Fixed Maturity Securities
Alternative Investments	792.4	747.5
Derivatives | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Liabilities
Derivative Liabilities	0	0
Derivatives | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Liabilities
Derivative Liabilities	54.9	59.7
Derivatives | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Liabilities
Derivative Liabilities	22.9	39.8
Derivatives | Fair Value, Measurements, Recurring | Fair Value Measured at Net Asset Value Per Share
Liabilities
Derivative Liabilities	$ 0	$ 0

Changes in Assets and Liabiliti

Changes in Assets and Liabilities Measured at Fair Value on a Recurring Basis using Significant Unobservable Inputs (Level 3) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019
Embedded Derivative in Modified Coinsurance Arrangement
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	$ 0	$ 0
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	(16.9)	86.9
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobservable Inputs	(22.9)	(109.7)	$ (39.8)	$ (22.8)
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Gain (Loss) Included in Earnings	16.9	(86.9)
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Gain (Loss) Included in Other Comprehensive Income (Loss)	0	0
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Purchases	0	0
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Sales	0	0
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Transfers into Level 3	0	0
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Transfers out of Level 3	0	0
States, Municipalities, and Political Subdivisions
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	0	31.3	15.5	41.8
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	0	2.8
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	(15.5)	13.3
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	0	2.9
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	0	0
Foreign Governments
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	21.7	20.9	21.8	21.8
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	(0.1)	0.9
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	0	0
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	(0.1)	(0.9)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	0	0
Public Utilities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	103.4	26.3	185.7	14.6
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	(4.6)	(0.3)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	36	18
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	113.7	6
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	(4.6)	0
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	0	0
Mortgage/Asset-backed Securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	77.2	75.1	81.3	34.1
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	(34.5)	(0.8)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	(32.6)	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	86.1	49.2
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	23.1	7.4
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	(34.5)	(0.2)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	0	0
Corporate Debt Securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	499.2	553	943.1	600.5
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	(13.8)	(50.6)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	0	20.9
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0	236.2
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	430.1	254
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	(13.8)	(2.2)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	0	0
Fixed Maturity Securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	701.5	706.6	1,247.4	712.8
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	(53)	(49.8)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	0	20.9
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	(32.6)	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	122.1	303.4
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	582.4	280.7
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	(53)	(0.4)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	0	0
Equity Securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	5.2	4.6	$ 4.7	$ 4.6
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0.5	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	0	0
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	0	0
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	$ 0	$ 0

Quantitative Information Regard

Quantitative Information Regarding Significant Unobservable Inputs (Details) $ in Millions		Mar. 31, 2021USD ($)Rate	Dec. 31, 2020USD ($)Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity Securities		$ 31.5	$ 28.3
Fair Value, Inputs, Level 3 | Discounted Cash Flow | Embedded Derivative in Modified Coinsurance Arrangement
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded Derivative in Modified Coinsurance Arrangement		(22.9)	(39.8)
Fair Value, Inputs, Level 3 | Corporate Debt Securities | Market Approach
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
All Other Corporate Bonds - Private		$ 45	$ 45.7
Fair Value, Inputs, Level 3 | Corporate Debt Securities | Market Approach | Minimum | Volatility of Credit
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
All Other Corporate Bonds - Private, Measurement Input | Rate	[1]	0.0050	0.0050
Fair Value, Inputs, Level 3 | Corporate Debt Securities | Market Approach | Maximum | Volatility of Credit
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
All Other Corporate Bonds - Private, Measurement Input | Rate	[1]	0.4779	0.2490
Fair Value, Inputs, Level 3 | Corporate Debt Securities | Market Approach | Weighted Average | Volatility of Credit
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
All Other Corporate Bonds - Private, Measurement Input | Rate	[1]	0.0658	0.0363
Fair Value, Inputs, Level 3 | Equity Securities | Market Approach
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity Securities		$ 5.2	$ 4.7
[1]	Represents basis point adjustments for credit-specific factors

Fair Values of Financial Inst_4

Fair Values of Financial Instruments Carrying Amounts and Estimated Fair value of Financial Instruments Not Measured at Fair Value (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Mortgage Loans, Carrying Amount	$ 2,402.2	$ 2,432.1
Policy Loans	3,628.8	3,683.9
Long-term Debt	3,346.8	3,345.7
Unfunded Commitments	0.9
Liabilities, Fair Value Disclosure	77.8	99.5
Fair Value, Nonrecurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Mortgage Loans, Fair Value Disclosure	2,456.1	2,641.8
Mortgage Loans, Carrying Amount	2,402.2	2,432.1
Policy Loans, Fair Value Disclosure	3,761.3	3,850.8
Policy Loans	3,628.8	3,683.9
Miscellaneous Long-Term Investments, Fair Value Disclosure	51.3	57.5
Miscellaneous Long-Term Investments	51.3	57.5
Financial Instruments, Financial Assets Fair Value Disclosure	6,268.7	6,550.1
Total Financial Instrument Assets Not Carried at Fair Value	6,082.3	6,173.5
Long-term Debt, Fair Value Disclosure	3,788.8	3,887.4
Long-term Debt	3,346.8	3,345.7
Advances, Fair Value Disclosure	302.2	312.2
Federal Home Loan Bank Funding Agreements	302.2	312.2
Unfunded Commitments	0.9	0.9
Liabilities, Fair Value Disclosure	4,091.9	4,200.5
Total Financial Instrument Liabilities Not Carried at Fair Value	3,649.9	3,658.8
Fair Value, Inputs, Level 1 | Fair Value, Nonrecurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Mortgage Loans, Fair Value Disclosure	0	0
Policy Loans, Fair Value Disclosure	0	0
Miscellaneous Long-Term Investments, Fair Value Disclosure	0	0
Financial Instruments, Financial Assets Fair Value Disclosure	0	0
Long-term Debt, Fair Value Disclosure	3,230.9	2,393.1
Advances, Fair Value Disclosure	0	0
Unfunded Commitments	0	0
Liabilities, Fair Value Disclosure	3,230.9	2,393.1
Fair Value, Inputs, Level 2 | Fair Value, Nonrecurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Mortgage Loans, Fair Value Disclosure	2,456.1	2,641.8
Policy Loans, Fair Value Disclosure	0	0
Miscellaneous Long-Term Investments, Fair Value Disclosure	26.9	28.2
Financial Instruments, Financial Assets Fair Value Disclosure	2,483	2,670
Long-term Debt, Fair Value Disclosure	557.9	1,494.3
Advances, Fair Value Disclosure	302.2	312.2
Unfunded Commitments	0.9	0.9
Liabilities, Fair Value Disclosure	861	1,807.4
Fair Value, Inputs, Level 3 | Fair Value, Nonrecurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Mortgage Loans, Fair Value Disclosure	0	0
Policy Loans, Fair Value Disclosure	3,761.3	3,850.8
Miscellaneous Long-Term Investments, Fair Value Disclosure	24.4	29.3
Financial Instruments, Financial Assets Fair Value Disclosure	3,785.7	3,880.1
Long-term Debt, Fair Value Disclosure	0	0
Advances, Fair Value Disclosure	0	0
Unfunded Commitments	0	0
Liabilities, Fair Value Disclosure	$ 0	$ 0

Fair Value of Financial Instrum

Fair Value of Financial Instruments Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Gain (Loss) on Embedded Derivative	$ 16.9	$ (86.9)
Ceded Policy Loans	$ 3,337.3		$ 3,390.6
Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Percentage of Total Fair Value of Fixed Maturities Securities	23.50%
Fair Value, Inputs, Level 2 | Pricing Service
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Percentage of Total Fair Value of Fixed Maturities Securities	60.50%
Fair Value, Inputs, Level 2 | Other Observable Market Data
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Percentage of Total Fair Value of Fixed Maturities Securities	10.90%
Fair Value Inputs Other Than Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Percentage of Total Fair Value of Fixed Maturities Securities	76.50%
Fair Value Inputs Level 2 Or Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Percentage of Total Fair Value of Fixed Maturities Securities	5.10%

Amortized Cost and Fair Values

Amortized Cost and Fair Values of Securities by Security Type (Detail) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Jan. 01, 2020
Debt Securities, Available-for-sale
Debt Securities, Available-for-sale, Amortized Cost, Total	$ 36,565.9	$ 36,546.5
Debt Securities, Available-for-sale, Allowance for credit losses for Fixed Maturity Securities	7.3	6.8
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	5,695.1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	177.7
Debt Securities, Available-for-sale, Total	42,076	44,137.3
United States Government and Government Agencies and Authorities
Debt Securities, Available-for-sale
Debt Securities, Available-for-sale, Amortized Cost, Total	464.6	559
Debt Securities, Available-for-sale, Allowance for credit losses for Fixed Maturity Securities	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	112.1	150.8
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0.1	0
Debt Securities, Available-for-sale, Total	576.6	709.8
States, Municipalities, and Political Subdivisions
Debt Securities, Available-for-sale
Debt Securities, Available-for-sale, Amortized Cost, Total	3,735.9	3,609.9
Debt Securities, Available-for-sale, Allowance for credit losses for Fixed Maturity Securities	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	506.7	652.8
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	38.7	1.5
Debt Securities, Available-for-sale, Total	4,203.9	4,261.2
Foreign Governments
Debt Securities, Available-for-sale
Debt Securities, Available-for-sale, Amortized Cost, Total	899	902.9
Debt Securities, Available-for-sale, Allowance for credit losses for Fixed Maturity Securities	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	224.3	266.5
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	2.7	1.2
Debt Securities, Available-for-sale, Total	1,120.6	1,168.2
Public Utilities
Debt Securities, Available-for-sale
Debt Securities, Available-for-sale, Amortized Cost, Total	5,390.6	5,486.4
Debt Securities, Available-for-sale, Allowance for credit losses for Fixed Maturity Securities	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1,080	1,481.9
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	26.1	6
Debt Securities, Available-for-sale, Total	6,444.5	6,962.3
Mortgage/Asset-backed Securities
Debt Securities, Available-for-sale
Debt Securities, Available-for-sale, Amortized Cost, Total	851.6	1,019.9
Debt Securities, Available-for-sale, Allowance for credit losses for Fixed Maturity Securities	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	73.6	88
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0.1	0.2
Debt Securities, Available-for-sale, Total	925.1	1,107.7
All Other Corporate Bonds
Debt Securities, Available-for-sale
Debt Securities, Available-for-sale, Amortized Cost, Total	25,220.2	24,958.8
Debt Securities, Available-for-sale, Allowance for credit losses for Fixed Maturity Securities	7.3	6.8	$ 48	$ 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	3,698.3	5,013.5
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	110	46.9
Debt Securities, Available-for-sale, Total	28,801.2	29,918.6
Redeemable Preferred Stocks
Debt Securities, Available-for-sale
Debt Securities, Available-for-sale, Amortized Cost, Total	4	9.6
Debt Securities, Available-for-sale, Allowance for credit losses for Fixed Maturity Securities	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0.1	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0	0.1
Debt Securities, Available-for-sale, Total	4.1	9.5
Fixed Maturity Securities
Debt Securities, Available-for-sale
Debt Securities, Available-for-sale, Amortized Cost, Total	36,565.9	36,546.5
Debt Securities, Available-for-sale, Allowance for credit losses for Fixed Maturity Securities	7.3	6.8
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	5,695.1	7,653.5
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	177.7	55.9
Debt Securities, Available-for-sale, Total	$ 42,076	$ 44,137.3

Length of Time Fixed Maturity S

Length of Time Fixed Maturity Securities had been in a Gross Unrealized Loss Position (Detail) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
United States Government and Government Agencies and Authorities
Debt Securities, Available-for-sale, Unrealized Loss Position
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 5.9
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0.1
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0
States, Municipalities, and Political Subdivisions
Debt Securities, Available-for-sale, Unrealized Loss Position
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	888.1	$ 133.4
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	38.7	1.5
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0.6	0.1
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Foreign Governments
Debt Securities, Available-for-sale, Unrealized Loss Position
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	61.8	20.3
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	2.7	1.2
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Public Utilities
Debt Securities, Available-for-sale, Unrealized Loss Position
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	321.4	76.3
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	22.8	3.7
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	38.6	25.4
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	3.3	2.3
Mortgage/Asset-backed Securities
Debt Securities, Available-for-sale, Unrealized Loss Position
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	0.6	3
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0.1	0.1
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	3.1	3.1
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0.1
All Other Corporate Bonds
Debt Securities, Available-for-sale, Unrealized Loss Position
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	1,883.4	520.4
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	84	22.4
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	246	113.5
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	26	24.5
Redeemable Preferred Stocks
Debt Securities, Available-for-sale, Unrealized Loss Position
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		9.5
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		0.1
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		0
Fixed Maturity Securities
Debt Securities, Available-for-sale, Unrealized Loss Position
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	3,161.2	762.9
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	148.4	29
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	288.3	142.1
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 29.3	$ 26.9

Investments Distribution of the

Investments Distribution of the Maturity Dates for Fixed Maturity Securities (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale, Amortized Cost, Net of Allowance for Credit Losses, Fiscal Year Maturity
Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, Year One, Net	$ 777.5	$ 881.8
Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year One Through Five, Net	6,304.4	6,162.6
Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year 5 Through 10, Net	10,695.5	10,886.9
Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year 10, Net	17,929.6	17,588.5
Available for sale Securities Debt Maturities Amortized Cost Gross Subtotal, Net	35,707	35,519.8
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Amortized Cost, Net	851.6	1,019.9
Debt Securities, Available-for-sale, Amortized Cost, Net of Allowance for Credit Losses	36,558.6	36,539.7
Available for Sale Securities Unrealized Gain Position Gross Gain
Available For Sale Securities Debt Maturities Within One Year Unrealized Gain Position Gross Gain	16.7	19.5
Available For Sale Securities Debt Maturities After One Through Five Years Unrealized Gain Position Gross Gain	581.8	589.9
Available For Sale Securities Debt Maturities After Five Through Ten Years Unrealized Gain Position Gross Gain	1,531.9	1,914.8
Available For Sale Securities Debt Maturities After Ten Years Unrealized Gain Position Gross Gain	3,491.1	5,041.3
Available For Sale Securities Debt Maturities Unrealized Gain Position Gross Gain Gross Subtotal	5,621.5	7,565.5
Available For Sale Securities Debt Maturities Without Single Maturity Date Unrealized Gain Position Gross Gain	73.6	88
Available for sale Securities, Debt Maturities Unrealized Gain Position Gross Gain	5,695.1	7,653.5
Available for Sale Securities Unrealized Loss Position Gross Loss
Available For Sale Securities Debt Maturities Within One Year Unrealized Loss Position Gross Loss	1.6	2.9
Available For Sale Securities Debt Maturities After One Through Five Years Unrealized Loss Position Gross Loss	16.2	22.9
Available For Sale Securities Debt Maturities After Five Through Ten Years Unrealized Loss Position Gross Loss	23.1	10.7
Available For Sale Securities Debt Maturities After Ten Years Unrealized Loss Position Gross Loss	136.7	19.2
Available For Sale Securities Debt Maturities Unrealized Gain Position Gross Loss Gross Subtotal	177.6	55.7
Available For Sale Securities Debt Maturities Without Single Maturity Date Unrealized Loss Position Gross Loss	0.1	0.2
Available For Sale Securities Unrealized Loss Position Gross Loss Subtotal	177.7	55.9
Fair Value Maturity Distribution [Abstract]
Debt Securities, Available-for-sale, Total	42,076	44,137.3
Available for Sale Securities Unrealized Gain Position Fair Value
Fair Value Maturity Distribution [Abstract]
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Fair Value	731.2	836.4
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Fair Value	6,672.8	6,545.7
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Fair Value	11,529.8	12,659.4
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after 10 Years, Fair Value	18,771.3	22,089.2
Available for sale Securities Debt Maturities Fair Value Gross Subtotal	37,705.1	42,130.7
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Fair Value	921.4	1,101.6
Debt Securities, Available-for-sale, Total	38,626.5	43,232.3
Available for Sale Securities Unrealized Loss Position Fair Value
Fair Value Maturity Distribution [Abstract]
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Fair Value	61.4	62
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Fair Value	197.2	183.9
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Fair Value	674.5	131.6
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after 10 Years, Fair Value	2,512.7	521.4
Available for sale Securities Debt Maturities Fair Value Gross Subtotal	3,445.8	898.9
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Fair Value	3.7	6.1
Debt Securities, Available-for-sale, Total	$ 3,449.5	$ 905

Investments Distribution by Ext

Investments Distribution by External Credit Rating for Fixed Maturity Securities (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale
Fixed Maturity Securities	$ 42,076	$ 44,137.3
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	5,695.1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	$ 177.7
Fixed maturity securities in unrealized loss position percent of total	100.00%
External Credit Rating, Investment Grade
Debt Securities, Available-for-sale
Fixed Maturity Securities	$ 38,846.3
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	5,451.1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	$ 149.9
Fixed maturity securities in unrealized loss position percent of total	84.40%
External Credit Rating, Below-Investment-Grade
Debt Securities, Available-for-sale
Fixed Maturity Securities	$ 3,229.7
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	244
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	$ 27.8
Fixed maturity securities in unrealized loss position percent of total	15.60%

Debt Securities, Available-for-

Debt Securities, Available-for-sale, Allowance for Credit Losses Rollforward (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Debt Securities, Available-for-sale, Allowance for Credit Loss
Debt Securities, Available-for-sale, Allowance for Credit Loss, Beginning Balance	$ 6.8
Debt Securities, Available-for-sale, Allowance for Credit Loss, Ending Balance	7.3
All Other Corporate Bonds
Debt Securities, Available-for-sale, Allowance for Credit Loss
Debt Securities, Available-for-sale, Allowance for Credit Loss, Beginning Balance	6.8
Debt Securities, Available-for-sale, Credit losses on securities for which credit losses were not previously recorded	0	$ 48
Debt Securities, Available-for-sale, Change in allowance on securities with allowance recorded in previous period	0.5	0
Debt Securities, Available-for-sale, Allowance for Credit Loss, Ending Balance	$ 7.3	$ 48

Investments Low Income Housing

Investments Low Income Housing Tax Credits (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Low Income Housing Tax Credits [Abstract]
Affordable Housing Tax Credits	$ 5.4	$ 8.3
Amortization of Affordable Housing Tax Credit Investments	(3.7)	(5.5)
Tax Benefits from Low Income Housing Investments	$ 1.7	$ 2.8

Mortgage Loans by Property Type

Mortgage Loans by Property Type and Geographic Region (Detail) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 2,402.2	$ 2,432.1
New England
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 35.1	$ 40
Mortgage Loans, Percent of Total	1.50%	1.60%
Mid-Atlantic
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 200.6	$ 202.5
Mortgage Loans, Percent of Total	8.40%	8.20%
East North Central
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 310.4	$ 330.4
Mortgage Loans, Percent of Total	12.90%	13.60%
West North Central
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 194.3	$ 196.1
Mortgage Loans, Percent of Total	8.10%	8.10%
South Atlantic
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 510.4	$ 512
Mortgage Loans, Percent of Total	21.20%	21.10%
East South Central
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 109.1	$ 110
Mortgage Loans, Percent of Total	4.50%	4.50%
West South Central
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 255.3	$ 257.4
Mortgage Loans, Percent of Total	10.60%	10.60%
Mountain
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 276.3	$ 268.8
Mortgage Loans, Percent of Total	11.50%	11.10%
Pacific
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 510.7	$ 514.9
Mortgage Loans, Percent of Total	21.30%	21.20%
Total
Mortgage Loans on Real Estate
Mortgage Loans, Percent of Total	100000000.00%	100000000.00%
Apartment
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 648.2	$ 638
Mortgage Loans, Percent of Total	27.00%	26.20%
Industrial
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 650.6	$ 654
Mortgage Loans, Percent of Total	27.10%	26.90%
Office
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 490.8	$ 517.8
Mortgage Loans, Percent of Total	20.40%	21.30%
Retail
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 566.1	$ 575.6
Mortgage Loans, Percent of Total	23.60%	23.70%
Other Property
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 46.5	$ 46.7
Mortgage Loans, Percent of Total	1.90%	1.90%
Total
Mortgage Loans on Real Estate
Mortgage Loans, Percent of Total	100.00%	100.00%

Schedule of Participating Mortg

Schedule of Participating Mortgage Loans by Internal Credit Rating and Loan to Value (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 2,402.2	$ 2,432.1
Loan to Value Ratio Below or Equal to 65 Percent
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 1,180.4	$ 1,189.4
Mortgage Loans, Percent of Total	49.10%	48.90%
Loan To Value Ratio Above 65 To 75 Percent
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 986.5	$ 1,000.3
Mortgage Loans, Percent of Total	41.10%	41.10%
Loan To Value Ratio Above 75 To 85 Percent
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 156.1	$ 155.8
Mortgage Loans, Percent of Total	6.50%	6.40%
Loan To Value Ratio Above 85 Percent
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 79.2	$ 86.6
Mortgage Loans, Percent of Total	3.30%	3.60%
Total
Mortgage Loans on Real Estate
Mortgage Loans, Percent of Total	100.00%	100.00%
AA Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 3.4	$ 3.5
Mortgage Loans, Percent of Total	0.10%	0.10%
A Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 533.7	$ 510
Mortgage Loans, Percent of Total	22.20%	21.00%
BBB Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 1,810	$ 1,863
Mortgage Loans, Percent of Total	75.30%	76.60%
BB Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 39.1	$ 39.4
Mortgage Loans, Percent of Total	1.60%	1.60%
B Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 16	$ 16.2
Mortgage Loans, Percent of Total	0.80%	0.70%
Total
Mortgage Loans on Real Estate
Mortgage Loans, Percent of Total	100.00%	100.00%

Mortgage Loans, Sorted by Appli

Mortgage Loans, Sorted by Applicable Credit Quality Indicators (Detail) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Jan. 01, 2020
Mortgage Loans on Real Estate
Financing Receivable, Allowance for Credit Losses, Mortgage Loans	$ 11.5	$ 13.1
Mortgage Loans, Carrying Amount	2,402.2	2,432.1
Commercial Real Estate
Mortgage Loans on Real Estate
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	1,129.8
Financing Receivable, Originated Four Years before Latest Fiscal Year	311.7
Financing Receivable, Originated Three Years before Latest Fiscal Year	390.1
Financing Receivable, Originated Two Years before Latest Fiscal Year	366.9
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	183.6
Financing Receivable, Originated in Current Fiscal Year	31.6
Financing Receivable, before Allowance for Credit Loss	2,413.7	2,445.2
Financing Receivable, Allowance for Credit Losses, Mortgage Loans	11.5
Loan to Value Ratio Below or Equal to 65 Percent
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	1,180.4	1,189.4
Loan to Value Ratio Below or Equal to 65 Percent | Commercial Real Estate
Mortgage Loans on Real Estate
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	821.9
Financing Receivable, Originated Four Years before Latest Fiscal Year	131.2
Financing Receivable, Originated Three Years before Latest Fiscal Year	90.6
Financing Receivable, Originated Two Years before Latest Fiscal Year	82.3
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	37.2
Financing Receivable, Originated in Current Fiscal Year	20.2
Financing Receivable, before Allowance for Credit Loss	1,183.4
Financing Receivable, Allowance for Credit Losses, Mortgage Loans	3	3.4	$ 3.5	$ 2.8
Loan To Value Ratio Above 65 To 75 Percent
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	986.5	1,000.3
Loan To Value Ratio Above 65 To 75 Percent | Commercial Real Estate
Mortgage Loans on Real Estate
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	161.1
Financing Receivable, Originated Four Years before Latest Fiscal Year	109.2
Financing Receivable, Originated Three Years before Latest Fiscal Year	280.1
Financing Receivable, Originated Two Years before Latest Fiscal Year	284.6
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	146.4
Financing Receivable, Originated in Current Fiscal Year	11.4
Financing Receivable, before Allowance for Credit Loss	992.8
Financing Receivable, Allowance for Credit Losses, Mortgage Loans	6.3	7.3	6.5	4.6
Loan To Value Ratio Above 75 To 85 Percent
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	156.1	155.8
Loan To Value Ratio Above 75 To 85 Percent | Commercial Real Estate
Mortgage Loans on Real Estate
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	106.4
Financing Receivable, Originated Four Years before Latest Fiscal Year	37.6
Financing Receivable, Originated Three Years before Latest Fiscal Year	13.3
Financing Receivable, Originated Two Years before Latest Fiscal Year	0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	0
Financing Receivable, Originated in Current Fiscal Year	0
Financing Receivable, before Allowance for Credit Loss	157.3
Financing Receivable, Allowance for Credit Losses, Mortgage Loans	1.2	1.3	0.4	0.5
Loan To Value Ratio Above 85 Percent
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	79.2	86.6
Loan To Value Ratio Above 85 Percent | Commercial Real Estate
Mortgage Loans on Real Estate
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	40.4
Financing Receivable, Originated Four Years before Latest Fiscal Year	33.7
Financing Receivable, Originated Three Years before Latest Fiscal Year	6.1
Financing Receivable, Originated Two Years before Latest Fiscal Year	0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	0
Financing Receivable, Originated in Current Fiscal Year	0
Financing Receivable, before Allowance for Credit Loss	80.2
Financing Receivable, Allowance for Credit Losses, Mortgage Loans	1	1.1	$ 0.7	$ 0.4
Originated Five or More Years before Last Fiscal Year
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	1,125.9
Originated Five or More Years before Last Fiscal Year | Commercial Real Estate
Mortgage Loans on Real Estate
Financing Receivable, Allowance for Credit Losses, Mortgage Loans	3.9
Originated Four Years before Last Fiscal Year
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	310.1
Originated Four Years before Last Fiscal Year | Commercial Real Estate
Mortgage Loans on Real Estate
Financing Receivable, Allowance for Credit Losses, Mortgage Loans	1.6
Originated Three Years before Last Fiscal Year
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	388
Originated Three Years before Last Fiscal Year | Commercial Real Estate
Mortgage Loans on Real Estate
Financing Receivable, Allowance for Credit Losses, Mortgage Loans	2.1
Originated Two Years before Last Fiscal Year
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	364.5
Originated Two Years before Last Fiscal Year | Commercial Real Estate
Mortgage Loans on Real Estate
Financing Receivable, Allowance for Credit Losses, Mortgage Loans	2.4
Originated in Fiscal Year before Latest Fiscal Year
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	182.2
Originated in Fiscal Year before Latest Fiscal Year | Commercial Real Estate
Mortgage Loans on Real Estate
Financing Receivable, Allowance for Credit Losses, Mortgage Loans	1.4
Originated in Current Fiscal Year
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	31.5
Originated in Current Fiscal Year | Commercial Real Estate
Mortgage Loans on Real Estate
Financing Receivable, Allowance for Credit Losses, Mortgage Loans	0.1
AA Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	3.4	3.5
AA Credit Rating | Commercial Real Estate
Mortgage Loans on Real Estate
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	3.4
Financing Receivable, Originated Four Years before Latest Fiscal Year	0
Financing Receivable, Originated Three Years before Latest Fiscal Year	0
Financing Receivable, Originated Two Years before Latest Fiscal Year	0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	0
Financing Receivable, Originated in Current Fiscal Year	0
Financing Receivable, before Allowance for Credit Loss	3.4
A Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	533.7	510
A Credit Rating | Commercial Real Estate
Mortgage Loans on Real Estate
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	376.2
Financing Receivable, Originated Four Years before Latest Fiscal Year	60.3
Financing Receivable, Originated Three Years before Latest Fiscal Year	63.8
Financing Receivable, Originated Two Years before Latest Fiscal Year	16.7
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	17.9
Financing Receivable, Originated in Current Fiscal Year	0
Financing Receivable, before Allowance for Credit Loss	534.9
BBB Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	1,810	1,863
BBB Credit Rating | Commercial Real Estate
Mortgage Loans on Real Estate
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	705
Financing Receivable, Originated Four Years before Latest Fiscal Year	241
Financing Receivable, Originated Three Years before Latest Fiscal Year	326.3
Financing Receivable, Originated Two Years before Latest Fiscal Year	350.2
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	165.7
Financing Receivable, Originated in Current Fiscal Year	31.6
Financing Receivable, before Allowance for Credit Loss	1,819.8
BB Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	39.1	39.4
BB Credit Rating | Commercial Real Estate
Mortgage Loans on Real Estate
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	29.2
Financing Receivable, Originated Four Years before Latest Fiscal Year	10.4
Financing Receivable, Originated Three Years before Latest Fiscal Year	0
Financing Receivable, Originated Two Years before Latest Fiscal Year	0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	0
Financing Receivable, Originated in Current Fiscal Year	0
Financing Receivable, before Allowance for Credit Loss	39.6
B Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	16	$ 16.2
B Credit Rating | Commercial Real Estate
Mortgage Loans on Real Estate
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	16
Financing Receivable, Originated Four Years before Latest Fiscal Year	0
Financing Receivable, Originated Three Years before Latest Fiscal Year	0
Financing Receivable, Originated Two Years before Latest Fiscal Year	0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	0
Financing Receivable, Originated in Current Fiscal Year	0
Financing Receivable, before Allowance for Credit Loss	$ 16

Mortgage Loans, Allowance for C

Mortgage Loans, Allowance for Credit Losses Rollforward (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Financing Receivable, Allowance for Credit Loss Rollforward, Mortgage Loans
Financing Receivable, Allowance for Credit Loss, Beginning Balance	$ 13.1
Financing Receivable, Allowance for Credit Loss, Ending Balance	11.5
Commercial Real Estate
Financing Receivable, Allowance for Credit Loss Rollforward, Mortgage Loans
Financing Receivable, Allowance for Credit Loss, Ending Balance	11.5
Commercial Real Estate | Loan to Value Ratio Below or Equal to 65 Percent
Financing Receivable, Allowance for Credit Loss Rollforward, Mortgage Loans
Financing Receivable, Allowance for Credit Loss, Beginning Balance	3.4
Current Period Provisions	(0.4)	$ 0.7
Write-offs	0	0
Recoveries	0	0
Financing Receivable, Allowance for Credit Loss, Ending Balance	3	3.5
Commercial Real Estate | Loan To Value Ratio Above 65 To 75 Percent
Financing Receivable, Allowance for Credit Loss Rollforward, Mortgage Loans
Financing Receivable, Allowance for Credit Loss, Beginning Balance	7.3
Current Period Provisions	(1)	1.9
Write-offs	0	0
Recoveries	0	0
Financing Receivable, Allowance for Credit Loss, Ending Balance	6.3	6.5
Commercial Real Estate | Loan To Value Ratio Above 75 To 85 Percent
Financing Receivable, Allowance for Credit Loss Rollforward, Mortgage Loans
Financing Receivable, Allowance for Credit Loss, Beginning Balance	1.3
Current Period Provisions	(0.1)	(0.1)
Write-offs	0	0
Recoveries	0	0
Financing Receivable, Allowance for Credit Loss, Ending Balance	1.2	0.4
Commercial Real Estate | Loan To Value Ratio Above 85 Percent
Financing Receivable, Allowance for Credit Loss Rollforward, Mortgage Loans
Financing Receivable, Allowance for Credit Loss, Beginning Balance	1.1
Current Period Provisions	(0.1)	0.3
Write-offs	0	0
Recoveries	0	0
Financing Receivable, Allowance for Credit Loss, Ending Balance	1	0.7
Commercial Real Estate | Loan to Value Ratio Total
Financing Receivable, Allowance for Credit Loss Rollforward, Mortgage Loans
Financing Receivable, Allowance for Credit Loss, Beginning Balance	13.1
Current Period Provisions	(1.6)	2.8
Write-offs	0	0
Recoveries	0	0
Financing Receivable, Allowance for Credit Loss, Ending Balance	$ 11.5	$ 11.1

Investments Remaining Contractu

Investments Remaining Contractual Maturity of Security Lending Agreements(Details) - Overnight and Continuous - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Transfer of Certain Financial Assets Accounted for as Secured Borrowings
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred	$ 43.5	$ 17.6
Securities Loaned and Securities Sold under Agreement to Repurchase, Gross Including Not Subject to Master Netting Arrangement	43.5	17.6
Secured Borrowings, Gross, Difference, Amount	0	0
United States Government and Government Agencies and Authorities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred	0.1	0.1
States, Municipalities, and Political Subdivisions
Transfer of Certain Financial Assets Accounted for as Secured Borrowings
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred	0.4	0.4
Public Utilities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred	0.5	0.3
All Other Corporate Bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred	$ 42.5	$ 16.8

Investments Federal Home Loan B

Investments Federal Home Loan Bank Carrying Amount, Collateral Posted and Advances Received (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Federal Home Loan Bank Carrying Value of Common Stock, Collateral Posted and Advances
Federal Home Loan Bank Common Stock	$ 26.9	$ 28.2
Federal Home Loan Bank, Advances	302.2	312.2
Federal Home Loan Bank, Collateral Posted to FHLB	1,840	2,016.5
Fixed Maturity Securities
Federal Home Loan Bank Carrying Value of Common Stock, Collateral Posted and Advances
Federal Home Loan Bank, Collateral Posted to FHLB	857.9	944
Commercial Mortgage Loans
Federal Home Loan Bank Carrying Value of Common Stock, Collateral Posted and Advances
Federal Home Loan Bank, Collateral Posted to FHLB	$ 982.1	$ 1,072.5

Investments Schedule of Financi

Investments Schedule of Financial Instrument and Derivative Offsetting (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Offsetting Derivative Assets
Derivative Asset, Fair Value, Gross Asset	$ 17.6	$ 19.8
Derivative Liabilities Offsetting Derivative Assets in Balance Sheet	0	0
Net Derivative Assets Reported in Balance Sheet	17.6	19.8
Securities Received as Collateral on Derivative Assets	(9.9)	(10.1)
Cash Collateral from Counterparties	(7.7)	(8.7)
Derivative Assets Net of Collateral	0	1
Offsetting Securities Borrowed
Gross Securities Borrowed	220	96.6
Liabilities Offsetting Securities Borrowed in Balance Sheet	0	0
Net Securities Borrowed Reported in Balance Sheet	220	96.6
Securities Received as Collateral on Securities Borrowed	(176.5)	(79)
Cash Received as Collateral on Securities Borrowed	(43.5)	(17.6)
Securities Borrowed Net of Collateral	0	0
Offsetting Financial Assets
Gross Financial Assets	237.6	116.4
Financial Liabilities Offsetting Financial Assets in Balance Sheet	0	0
Net Financial Assets Reported in Balance Sheet	237.6	116.4
Securities Received as Collateral on Financial Assets	(186.4)	(89.1)
Cash Received as Collateral on Financial Assets	(51.2)	(26.3)
Financial Assets Net of Collateral	0	1
Offsetting Derivative Liabilities
Net Derivative Liabilities Reported in Balance Sheet	77.8	99.5
Offsetting Securities Loaned
Gross Securities Loaned	43.5	17.6
Assets Offsetting Securities Loaned in Balance Sheet	0	0
Net Securities Loaned Reported in Balance Sheet	43.5	17.6
Securities Given as Collateral on Securities Loaned	(43.5)	(17.6)
Cash Given as Collateral on Securities Loaned	0	0
Securities Loaned, Amount Offset Against Collateral	0	0
Offsetting Financial Liabilities
Gross Financial Liability	98.4	77.3
Financial Assets Offsetting Financial Liabilities in Balance Sheet	0	0
Net Financial Liabilities Reported in Balance Sheet	98.4	77.3
Securities Given as Collateral on Financial Liabilities	(98.1)	(76.6)
Cash Given as Collateral on Financial Liabilities	0	0
Financial Liabilities Net of Collateral	0.3	0.7
Over the Counter
Offsetting Derivative Liabilities
Gross Derivative Liability	54.9	59.7
Derivative Assets Offsetting Derivative Liabilities in Balance Sheet	0	0
Net Derivative Liabilities Reported in Balance Sheet	54.9	59.7
Securities Given as Collateral on Derivative Liabilities	(54.6)	(59)
Cash Collateral to counterparties	0	0
Derivative Liabilities Net of Collateral	$ 0.3	$ 0.7

Investments Investment Income (

Investments Investment Income (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2021	Mar. 31, 2020
Net Investment Income
Investment Income, Interest and Dividend		$ 559.3	$ 596.7
Less Investment Expenses		7.5	8.5
Less Investment Income on PFA Assets		3.1	3.2
Net Investment Income		548.7	585
Fixed Maturity Securities
Net Investment Income
Investment Income, Interest and Dividend		469.8	539.8
Derivatives
Net Investment Income
Investment Income, Interest and Dividend		16.2	20.2
Mortgage Loans
Net Investment Income
Investment Income, Interest and Dividend		26.3	29
Policy Loans
Net Investment Income
Investment Income, Interest and Dividend		4.8	4.8
Perpetual Preferred Securities
Net Investment Income
Investment Income, Interest and Dividend	[1]	3.6	(17.1)
Private Equity Partnerships
Net Investment Income
Investment Income, Interest and Dividend	[2]	35.9	10.4
Other Long-term Investments
Net Investment Income
Investment Income, Interest and Dividend		2.1	3.2
Short-term Investments
Net Investment Income
Investment Income, Interest and Dividend		$ 0.6	$ 6.4
[1]	The net unrealized gain (loss) recognized in net investment income for the three months ended March 31, 2021 related to perpetual preferred securities still held at March 31, 2021 was $2.7 million. The net unrealized loss recognized in net investment income for the three months ended March 31, 2020 related to perpetual preferred securities still held at March 31, 2020 was $17.9 million.
[2]	The net unrealized gain recognized in net investment income for the three months ended March 31, 2021 related to private equity partnerships still held at March 31, 2021 was $27.0 million. The net unrealized gain recognized in net investment income for the three months ended March 31, 2020 related to private equity partnerships still held at March 31, 2020 was $5.4 million. See Note 3 for further discussion of private equity partnerships.

Realized Investment Gains and L

Realized Investment Gains and Losses Reported in Consolidated Statements of Income (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021		Mar. 31, 2020
Fixed Maturity Securities
Gross Gains on Sales	$ 71.3	[1]	$ 1.4
Gross Losses on Sales	(1.1)		(0.7)
Credit Losses	(8.3)		(53.9)
Mortgage Loans and Other Invested Assets
Gross Gains on Sales	2.5		0.3
Gross Losses on Sales	0		(0.2)
Credit Losses	1.7		(2.6)
Embedded Derivative in Modified Coinsurance Arrangement	16.9		(86.9)
All Other Derivatives	1.7		(0.7)
Foreign Currency Transactions	(0.1)		(0.7)
Net Realized Investment Gain (Loss)	$ 84.6		$ (144)
[1]	Gross gains on sales of fixed maturity securities includes gains of $67.6 million as a result of the second phase of the reinsurance transaction that we completed during the first quarter of 2021. See Note 12 for further discussion.

Investments - Additional Inform

Investments - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2021USD ($)Integer	Mar. 31, 2020USD ($)Integer	Dec. 31, 2020USD ($)
Schedule of Investments
Commitment to Fund Private Placement Fixed Maturity Securities	$ 106,500,000
Other Long-term Investments	995,300,000		$ 960,200,000
Unfunded Commitments	900,000
Financing Receivable, Allowance for Credit Losses, Mortgage Loans	11,500,000		13,100,000
Accrued Investment Income	668,700,000		611,400,000
Loan Foreclosure Expense	0	$ 0
Commitments to Fund Commercial Mortgage Loans	$ 18,000,000
Repurchase agreements - Typical Days outstanding	30
Minimum percent of the fair value of securities loaned or securities purchased under repurchase agreements be maintained as collateral	102.00%
Gross Securities Borrowed	$ 220,000,000		96,600,000
Outstanding Repurchase Agreements	0		0
Off Balance Sheet Amount
Schedule of Investments
Cash Collateral for Borrowed Securities	43,500,000		17,600,000
Securities Received as Collateral	186,400,000		82,800,000
Commercial Real Estate
Schedule of Investments
Financing Receivable, before Allowance for Credit Loss, Mortgage Loans	2,413,700,000		2,445,200,000
Financing Receivable, Allowance for Credit Losses, Mortgage Loans	11,500,000
Accrued Investment Income	$ 8,000,000		8,000,000
Financing Receivable, Modifications, Number of Contracts | Integer	0	0
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	$ 0		0
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	0	$ 0
Unfunded Mortgage Loan Commitments
Schedule of Investments
Allowance for Credit Losses, Unfunded Mortgage Loan Commitments			100,000
Variable Interest Entity, Not Primary Beneficiary
Schedule of Investments
Other Long-term Investments	816,800,000		776,800,000
Tax Credit Partnership | Variable Interest Entity, Not Primary Beneficiary
Schedule of Investments
Other Long-term Investments	24,400,000		29,300,000
Equity Method Investments | Variable Interest Entity, Not Primary Beneficiary
Schedule of Investments
Other Long-term Investments	$ 792,400,000		$ 747,500,000
External Credit Rating, Investment Grade
Schedule of Investments
Number of Fixed Maturity Securities in an Unrealized Loss Position	239
Number of Fixed Maturity Securities in an Unrealized Loss Position Continuously for Over One Year	11
External Credit Rating, Below-Investment-Grade
Schedule of Investments
Number of Fixed Maturity Securities in an Unrealized Loss Position	21
Number of Fixed Maturity Securities in an Unrealized Loss Position Continuously for Over One Year	12

Derivative Financial Instrume_3

Derivative Financial Instruments Nature and Amount of Collateral Received From and Posted To Our Derivative Counterparties (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Derivative
Cash Collateral from Counterparties	$ 7.7	$ 8.7
Carrying Value of Fixed Maturity Securities Posted as Collateral to Counterparties	9.9	10.1
Cash
Derivative
Cash Collateral from Counterparties	8.8	8.7
Fixed Maturity Securities
Derivative
Carrying Value of Fixed Maturity Securities Posted as Collateral to Counterparties	$ 46.8	$ 54

Notional Amounts for Each Categ

Notional Amounts for Each Category of Derivative Activity (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Derivative
Balance at beginning of period	$ 744.4	$ 881.4
Additions	101.7	52
Terminations		1.3
Foreign Currency	0.2	(0.7)
Balance at end of period	846.3	931.4
Interest Rate Swaps | Receive Fixed/Pay Fixed
Derivative
Balance at beginning of period	720.8	611.1
Additions	26.2	52
Terminations		0
Foreign Currency	0	0
Balance at end of period	747	663.1
Interest Rate Swaps | Receive Fixed/Pay Variable
Derivative
Balance at beginning of period	0	250
Additions	0	0
Terminations		0
Foreign Currency	0	0
Balance at end of period	0	250
Credit Default Swaps | Credit Default Swaps
Derivative
Balance at beginning of period	11.7	11.4
Additions	0	0
Terminations		0
Foreign Currency	0.2	(0.7)
Balance at end of period	11.9	10.7
Forwards
Derivative
Balance at beginning of period	11.9	8.9
Additions	0	0
Terminations		1.3
Foreign Currency	0	0
Balance at end of period	11.9	7.6
Equity Contract | Total Return Swap
Derivative
Balance at beginning of period	0	0
Additions	75.5	0
Terminations		0
Foreign Currency	0	0
Balance at end of period	$ 75.5	$ 0

Derivative Financial Instrume_4

Derivative Financial Instruments Fair Value Hedges Carrying Amount of Hedged Assets and Cumulative Basis Adjustments (Details) - Interest Rate Swaps - Receive Fixed/Pay Fixed - Designated as Hedging Instrument - Fair Value Hedging - Fixed Maturity Securities - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Derivative Instruments and Hedging Activities Disclosures
Hedged Asset, Fair Value Hedge	$ 405.6	$ 404.5
Hedged Asset, Fair Value Hedge, Cumulative Increase (Decrease)	$ 14.9	$ 24.4

Location and Fair Values of Der

Location and Fair Values of Derivative Financial Instruments (Detail) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Derivative
Asset Derivatives Fair Value	$ 17.6	$ 19.8
Designated as Hedging Instrument | Other Long-term Investments
Derivative
Asset Derivatives Fair Value	17.4	19.7
Designated as Hedging Instrument | Other Long-term Investments | Foreign Exchange Contracts | Cash Flow Hedging
Derivative
Asset Derivatives Fair Value	15.4	16.4
Designated as Hedging Instrument | Other Long-term Investments | Foreign Exchange Contracts | Fair Value Hedging
Derivative
Asset Derivatives Fair Value	2	3.3
Designated as Hedging Instrument | Other Liabilities
Derivative
Liability Derivatives Fair Value	32.3	35.4
Designated as Hedging Instrument | Other Liabilities | Foreign Exchange Contracts | Cash Flow Hedging
Derivative
Liability Derivatives Fair Value	10.1	9.4
Designated as Hedging Instrument | Other Liabilities | Foreign Exchange Contracts | Fair Value Hedging
Derivative
Liability Derivatives Fair Value	22.2	26
Not Designated as Hedging Instrument | Other Long-term Investments
Derivative
Asset Derivatives Fair Value	0.2	0.1
Not Designated as Hedging Instrument | Other Long-term Investments | Forwards
Derivative
Asset Derivatives Fair Value	0.1	0
Not Designated as Hedging Instrument | Other Long-term Investments | Foreign Exchange Contracts
Derivative
Asset Derivatives Fair Value	0	0
Not Designated as Hedging Instrument | Other Long-term Investments | Credit Default Swaps
Derivative
Asset Derivatives Fair Value	0.1	0.1
Not Designated as Hedging Instrument | Other Long-term Investments | Embedded Derivative in Modified Coinsurance Arrangement
Derivative
Asset Derivatives Fair Value	0	0
Not Designated as Hedging Instrument | Other Liabilities
Derivative
Liability Derivatives Fair Value	45.5	64.1
Not Designated as Hedging Instrument | Other Liabilities | Forwards
Derivative
Asset Derivatives Fair Value		0.5
Liability Derivatives Fair Value	0.1
Not Designated as Hedging Instrument | Other Liabilities | Foreign Exchange Contracts
Derivative
Liability Derivatives Fair Value	22.5	23.8
Not Designated as Hedging Instrument | Other Liabilities | Credit Default Swaps
Derivative
Liability Derivatives Fair Value	0	0
Not Designated as Hedging Instrument | Other Liabilities | Embedded Derivative in Modified Coinsurance Arrangement
Derivative
Liability Derivatives Fair Value	$ 22.9	$ 39.8

Derivative Financial Instrume_5

Derivative Financial Instruments Location of Gains and Losses Designated as Hedging Instruments, Consolidated Statements of Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Derivative Instruments, Gain (Loss)
Net Investment Income	$ 548.7	$ 585
Net Realized Investment Gain (Loss)	84.6	(144)
Interest and Debt Expense	44.4	45.7
Derivative, Gain (Loss) on Derivative, Net	(1.7)	0.7
Designated as Hedging Instrument | Interest Rate Swaps | Net Investment Income | Cash Flow Hedging
Derivative Instruments, Gain (Loss)
Net Investment Income	52	73
Derivative, Gain (Loss) on Derivative, Net	15.5	19.2
Designated as Hedging Instrument | Interest Rate Swaps | Net Investment Income | Fair Value Hedging
Derivative Instruments, Gain (Loss)
Net Investment Income	0	0
Derivative, Gain (Loss) on Derivative, Net	0	0
Designated as Hedging Instrument | Interest Rate Swaps | Net Realized Investment Gain (Loss) | Cash Flow Hedging
Derivative Instruments, Gain (Loss)
Net Realized Investment Gain (Loss)	2.4	0
Derivative, Gain (Loss) on Derivative, Net	1.8	0
Designated as Hedging Instrument | Interest Rate Swaps | Net Realized Investment Gain (Loss) | Fair Value Hedging
Derivative Instruments, Gain (Loss)
Net Realized Investment Gain (Loss)	0	(1.5)
Derivative, Gain (Loss) on Derivative, Net	0	1.5
Designated as Hedging Instrument | Interest Rate Swaps | Interest and Debt Expense | Cash Flow Hedging
Derivative Instruments, Gain (Loss)
Interest and Debt Expense	7.3	7.3
Derivative, Gain (Loss) on Derivative, Net	0.1	0.6
Designated as Hedging Instrument | Interest Rate Swaps | Interest and Debt Expense | Fair Value Hedging
Derivative Instruments, Gain (Loss)
Interest and Debt Expense	0	3.6
Derivative, Gain (Loss) on Derivative, Net	0	0.1
Designated as Hedging Instrument | Foreign Exchange Contracts | Net Investment Income | Cash Flow Hedging
Derivative Instruments, Gain (Loss)
Net Investment Income	3.1	2.9
Derivative, Gain (Loss) on Derivative, Net	0.3	0.9
Designated as Hedging Instrument | Foreign Exchange Contracts | Net Investment Income | Fair Value Hedging
Derivative Instruments, Gain (Loss)
Net Investment Income	2.3	1.4
Derivative, Gain (Loss) on Derivative, Net	1	0.8
Designated as Hedging Instrument | Foreign Exchange Contracts | Net Realized Investment Gain (Loss) | Cash Flow Hedging
Derivative Instruments, Gain (Loss)
Net Realized Investment Gain (Loss)	0	0
Derivative, Gain (Loss) on Derivative, Net	0	0
Designated as Hedging Instrument | Foreign Exchange Contracts | Net Realized Investment Gain (Loss) | Fair Value Hedging
Derivative Instruments, Gain (Loss)
Net Realized Investment Gain (Loss)	(9.5)	(13.2)
Derivative, Gain (Loss) on Derivative, Net	9.5	13.2
Designated as Hedging Instrument | Foreign Exchange Contracts | Interest and Debt Expense | Cash Flow Hedging
Derivative Instruments, Gain (Loss)
Interest and Debt Expense	0	0
Derivative, Gain (Loss) on Derivative, Net	0	0
Designated as Hedging Instrument | Foreign Exchange Contracts | Interest and Debt Expense | Fair Value Hedging
Derivative Instruments, Gain (Loss)
Interest and Debt Expense	0	0
Derivative, Gain (Loss) on Derivative, Net	$ 0	$ 0

Location of Gains and Losses on

Location of Gains and Losses on Derivative Instruments Designated as Cash Flow Hedging Instruments (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Foreign Exchange Contracts | Designated as Hedging Instrument | Cash Flow Hedging
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in OCI on Derivatives (Effective Portion)	$ (1.5)	$ 19.5

Gains and Losses on Derivatives

Gains and Losses on Derivatives Not Designated as Hedging Instruments (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Derivative Instruments, Gain (Loss)
Net Gain (Loss) on Derivatives	$ 1.7	$ (0.7)
Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss)
Net Gain (Loss) on Derivatives	18.6	(87.6)
Credit Default Swaps | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss)
Net Gain (Loss) on Derivatives	(0.1)	0.8
Foreign Exchange Contracts | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss)
Net Gain (Loss) on Derivatives	1.8	(1.5)
Embedded Derivative in Modified Coinsurance Arrangement | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss)
Net Gain (Loss) on Derivatives	16.9	(86.9)
Total Return Swap | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss)
Net Gain (Loss) on Derivatives	$ 1.3	$ 0

Derivative Financial Instrume_6

Derivative Financial Instruments - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019
Derivative
Aggregate fair value of all derivative instruments with credit risk-related contingent features in a liability position	$ 54.9		$ 59.7
Interest Rate Cash Flow Hedge Gain (Loss) Reclassified to Earnings, Net	0.6
Approximate amount of net deferred gains on derivative instruments expected to be amortized during the next twelve months	56.9
Component of Derivative Gain (Loss) Excluded from the Assessment of Hedge Effectiveness	(7)	$ 28.8
Discontinued Hedge Accounting Due to Instrument No Longer Qualifying as Fair Value Hedge	0	0
Derivative, Notional Amount	846.3	931.4	744.4	$ 881.4
Designated as Hedging Instrument | Other Liabilities
Derivative
Gross Derivative Liability	32.3		35.4
Not Designated as Hedging Instrument | Other Liabilities
Derivative
Gross Derivative Liability	45.5		64.1
Credit Risk Contract | Not Designated as Hedging Instrument | Other Liabilities
Derivative
Gross Derivative Liability	0		0
Credit Risk Contract | Credit Default Swaps
Derivative
Derivative, Notional Amount	11.9	10.7	11.7	11.4
Credit Risk Contract | Credit Default Swaps | Not Designated as Hedging Instrument
Derivative
Derivative, Notional Amount	11.9		11.7
Forwards
Derivative
Derivative, Notional Amount	11.9	7.6	11.9	8.9
Forwards | Not Designated as Hedging Instrument
Derivative
Derivative, Notional Amount	11.9		11.9
Forwards | Not Designated as Hedging Instrument | Other Liabilities
Derivative
Gross Derivative Liability	0.1
Foreign Exchange Contracts | Not Designated as Hedging Instrument | Other Liabilities
Derivative
Gross Derivative Liability	22.5		23.8
Foreign Exchange Contracts | Cash Flow Hedging | Designated as Hedging Instrument | Other Liabilities
Derivative
Gross Derivative Liability	10.1		9.4
Foreign Exchange Contracts | Fair Value Hedging | Designated as Hedging Instrument | Other Liabilities
Derivative
Gross Derivative Liability	22.2		26
Total Return Swap | Not Designated as Hedging Instrument
Derivative
Derivative, Notional Amount	75.5
Credit Exposure
Derivative
Credit Exposure on Derivatives	0		0.7
Receive Fixed/Pay Fixed | Interest Rate Swaps
Derivative
Derivative, Notional Amount	747	663.1	720.8	611.1
Receive Fixed/Pay Fixed | Interest Rate Swaps | Not Designated as Hedging Instrument
Derivative
Derivative, Notional Amount	148.2		148.2
Receive Fixed/Pay Fixed | Interest Rate Swaps | Cash Flow Hedging | Designated as Hedging Instrument
Derivative
Derivative, Notional Amount	210.2		210.2
Receive Fixed/Pay Fixed | Interest Rate Swaps | Fair Value Hedging | Designated as Hedging Instrument
Derivative
Derivative, Notional Amount	388.6		362.4
Receive Fixed/Pay Variable | Interest Rate Swaps
Derivative
Derivative, Notional Amount	$ 0	$ 250	$ 0	250
Receive Fixed/Pay Variable | Interest Rate Swaps | Fair Value Hedging | Designated as Hedging Instrument
Derivative
Derivative, Notional Amount				$ 250

Schedule of Accumulated Other C

Schedule of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Accumulated Other Comprehensive Income (Loss)
Balance at Beginning of Year	$ 374.2	$ 37.3
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(447.2)	(286)
Reclassification from Accumulated Other Comprehensive Income or Loss, Current Period, Net of Tax	(48.1)	(31.6)
Total Other Comprehensive Loss	(399.1)	(254.4)
Balance at End of Period	(24.9)	(217.1)
Net Unrealized Gain on Securities
Accumulated Other Comprehensive Income (Loss)
Balance at Beginning of Year	1,067.7	615.9
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(447.2)	(263.2)
Reclassification from Accumulated Other Comprehensive Income or Loss, Current Period, Net of Tax	(57.7)	(42.6)
Total Other Comprehensive Loss	(389.5)	(220.6)
Balance at End of Period	678.2	395.3
Net Gain on Hedges
Accumulated Other Comprehensive Income (Loss)
Balance at Beginning of Year	97.8	187.8
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(6.8)	37.7
Reclassification from Accumulated Other Comprehensive Income or Loss, Current Period, Net of Tax	13.9	14.9
Total Other Comprehensive Loss	(20.7)	22.8
Balance at End of Period	77.1	210.6
Foreign Currency Translation Adjustment
Accumulated Other Comprehensive Income (Loss)
Balance at Beginning of Year	(261.3)	(281.6)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	7.3	(63.6)
Reclassification from Accumulated Other Comprehensive Income or Loss, Current Period, Net of Tax	0	0
Total Other Comprehensive Loss	7.3	(63.6)
Balance at End of Period	(254)	(345.2)
Unrecognized Pension and Postretirement Benefit Costs
Accumulated Other Comprehensive Income (Loss)
Balance at Beginning of Year	(530)	(484.8)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(0.5)	3.1
Reclassification from Accumulated Other Comprehensive Income or Loss, Current Period, Net of Tax	(4.3)	(3.9)
Total Other Comprehensive Loss	3.8	7
Balance at End of Period	$ (526.2)	$ (477.8)

Schedule of Components of Unrea

Schedule of Components of Unrealized Gain (Loss) on Securities (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Change in Components of Net Unrealized Gain on Securities
Change in Net Unrealized Gain on Securities	$ (1,646)	$ (1,666.7)
Fixed Maturity Securities
Change in Components of Net Unrealized Gain on Securities
Beginning of Period Balance	7,597.6	6,364.4
Change in Net Unrealized Gain on Securities	(2,080.2)	(2,103.2)
End of Period Balance	5,517.4	4,261.2
Deferred Acquisition Costs
Change in Components of Net Unrealized Gain on Securities
Beginning of Period Balance	(85.1)	(62.7)
Change in Net Unrealized Gain on Securities	18.5	25.3
End of Period Balance	(66.6)	(37.4)
Reserve for Future Policy and Contract Benefits
Change in Components of Net Unrealized Gain on Securities
Beginning of Period Balance	(6,225.6)	(5,803.1)
Change in Net Unrealized Gain on Securities	1,636.7	1,903.6
End of Period Balance	(4,588.9)	(3,899.5)
Reinsurance Recoverable
Change in Components of Net Unrealized Gain on Securities
Beginning of Period Balance	200.2	424.7
Change in Net Unrealized Gain on Securities	(66.9)	(102)
End of Period Balance	133.3	322.7
Income Tax
Change in Components of Net Unrealized Gain on Securities
Beginning of Period Balance	(419.4)	(307.4)
Change in Net Unrealized Gain on Securities	102.4	55.7
End of Period Balance	(317)	(251.7)
Net Unrealized Gain on Securities
Change in Components of Net Unrealized Gain on Securities
Beginning of Period Balance	1,067.7	615.9
Change in Net Unrealized Gain on Securities	(389.5)	(220.6)
End of Period Balance	$ 678.2	$ 395.3

Schedule of Reclassifications O

Schedule of Reclassifications Out of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Benefits and Change in Reserves for Future Benefits	$ 2,051.2	$ 1,854.8
Net Investment Income	548.7	585
Interest and Debt Expense	(44.4)	(45.7)
Other Expenses	(245)	(235.6)
Income Before Income Tax	198.8	202.1
Income Tax Expense (Benefit)	45.8	41.1
Net Income	153	161
Reclassification out of Accumulated Other Comprehensive Income (Loss) | Net Unrealized Gain on Securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Gain (Loss) on Investments, Excluding Other than Temporary Impairments	68.3	0
Other-Than-Temporary Impairment Loss	(8.3)	(53.9)
Benefits and Change in Reserves for Future Benefits	(133.1)	0
Income Before Income Tax	(73.1)	(53.9)
Income Tax Expense (Benefit)	(15.4)	(11.3)
Net Income	(57.7)	(42.6)
Reclassification out of Accumulated Other Comprehensive Income (Loss) | Net Gain on Hedges
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Income Before Income Tax	17.6	18.7
Income Tax Expense (Benefit)	3.7	3.8
Net Income	13.9	14.9
Reclassification out of Accumulated Other Comprehensive Income (Loss) | Net Gain on Hedges | Interest Rate Swaps
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Gain (Loss) on Investments, Excluding Other than Temporary Impairments	1.8	0
Net Investment Income	15.3	18.8
Interest and Debt Expense	0	(0.6)
Reclassification out of Accumulated Other Comprehensive Income (Loss) | Net Gain on Hedges | Foreign Exchange Contracts
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Net Investment Income	0.5	0.5
Reclassification out of Accumulated Other Comprehensive Income (Loss) | Net Actuarial Loss
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Other Expenses	(5.6)	(5)
Reclassification out of Accumulated Other Comprehensive Income (Loss) | Prior Service Credit
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Other Expenses	0.1	0.1
Reclassification out of Accumulated Other Comprehensive Income (Loss) | Unrecognized Pension and Postretirement Benefit Costs
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Income Before Income Tax	(5.5)	(4.9)
Income Tax Expense (Benefit)	(1.2)	(1)
Net Income	$ (4.3)	$ (3.9)

Liability for Unpaid Claims a_3

Liability for Unpaid Claims and Claims Adjustment Expense (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense
Balance at January 1	$ 24,180.2	$ 23,076.7
Less Reinsurance Recoverable	8,378.9	2,246.8
Net Balance at January 1	15,801.3	20,829.9
Incurred Related to
Current Year	1,782	1,605.9
Paid Related to
Current Year	(409.2)	(368)
Prior Years	(1,327.2)	(1,453.7)
Total Paid	(1,736.4)	(1,821.7)
Reserves Ceded Pursuant to Reinsurance Transaction	(990)	0
Net Balance at March 31	15,001.7	20,631.7
Plus Reinsurance Recoverable	9,225.8	2,260.7
Balance at March 31	24,227.5	22,892.4
Amount Related to Interest
Incurred Related to
Prior Years	183.4	271.9
Incurred Claims
Incurred Related to
Prior Years	(55.9)	(126.7)
Foreign Currency
Incurred Related to
Prior Years	17.3	(127.6)
Operating Expense
Incurred Related to
Total Incurred	$ 1,926.8	$ 1,623.5

Reconciliation of Policy and Co

Reconciliation of Policy and Contract Benefits and Reserves for Future Policy and Contract Benefits (Detail) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Insurance [Abstract]
Policy and Contract Benefits	$ 1,899.3	$ 1,855.4	$ 1,760.3
Reserves for Future Policy and Contract Benefits	48,112.3	49,653	45,706.5
Total Policy and Contract Benefits and Reserves for Future Policy and Contract Benefits	50,011.6		47,466.8
Life Reserves for Future Policy and Contract Benefits	8,389.3		8,428.5
Accident and Health Active Life Reserves	12,805.9		12,246.4
Adjustment Related to Unrealized Investment Gains and Losses	4,588.9		3,899.5
Liability for Unpaid Claims and Claim Adjustment Expense	$ 24,227.5	$ 24,180.2	$ 22,892.4	$ 23,076.7

Liability for Unpaid Claims a_4

Liability for Unpaid Claims and CAE - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Liability for Unpaid Claims and CAE Narrative Information
Reinsurance Recoverables, Incurred but Not Reported Claims	$ 9,225.8	$ 8,378.9	$ 2,260.7	$ 2,246.8
Closed Block Individual Disability Reinsurance Transaction | Phase 2
Liability for Unpaid Claims and CAE Narrative Information
Increase in Benefits and Change in Reserves for Future Benefits	133.1
Reinsurance Recoverables, Incurred but Not Reported Claims	$ 990

Premium Income by Major Line of

Premium Income by Major Line of Business within Each Segment (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Segment Reporting Information
Premium Income	$ 2,378.3	$ 2,371.4
Operating Segments
Segment Reporting Information
Premium Income	2,378.3	2,371.4
Operating Segments | Unum US
Segment Reporting Information
Premium Income	1,525.8	1,527.7
Operating Segments | Unum US | Group Long-term Disability
Segment Reporting Information
Premium Income	457.7	463
Operating Segments | Unum US | Group Short-term Disability
Segment Reporting Information
Premium Income	215.2	203.2
Operating Segments | Unum US | Group Life
Segment Reporting Information
Premium Income	410	414.5
Operating Segments | Unum US | Accidental Death & Dismemberment
Segment Reporting Information
Premium Income	41.4	41.7
Operating Segments | Unum US | Individual Disability
Segment Reporting Information
Premium Income	115.7	109.5
Operating Segments | Unum US | Voluntary Benefits
Segment Reporting Information
Premium Income	218.7	230.4
Operating Segments | Unum US | Dental and Vision
Segment Reporting Information
Premium Income	67.1	65.4
Operating Segments | Unum International
Segment Reporting Information
Premium Income	174.4	164.6
Operating Segments | Unum International | Group Long-term Disability
Segment Reporting Information
Premium Income	97.1	90.8
Operating Segments | Unum International | Group Life
Segment Reporting Information
Premium Income	27.3	30.9
Operating Segments | Unum International | Supplemental
Segment Reporting Information
Premium Income	28	23.9
Operating Segments | Unum International | Unum Poland
Segment Reporting Information
Premium Income	22	19
Operating Segments | Colonial Life
Segment Reporting Information
Premium Income	426.4	434.7
Operating Segments | Colonial Life | Accident, Sickness, and Disability
Segment Reporting Information
Premium Income	240.7	249.3
Operating Segments | Colonial Life | Life
Segment Reporting Information
Premium Income	96.6	93.8
Operating Segments | Colonial Life | Cancer and Critical Illness Colonial
Segment Reporting Information
Premium Income	89.1	91.6
Operating Segments | Closed Block
Segment Reporting Information
Premium Income	251.7	244.4
Operating Segments | Closed Block | Individual Disability
Segment Reporting Information
Premium Income	72.1	77
Operating Segments | Closed Block | Long-term Care
Segment Reporting Information
Premium Income	177.4	164.8
Operating Segments | Closed Block | Other Insurance Product Line
Segment Reporting Information
Premium Income	$ 2.2	$ 2.6

Selected Operating Statement Da

Selected Operating Statement Data by Segment (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Segment Reporting Information
Premium Income	$ 2,378.3	$ 2,371.4
Net Investment Income	548.7	585
Other Income	60.4	58.7
Operating Segments
Segment Reporting Information
Premium Income	2,378.3	2,371.4
Net Investment Income	548.7	585
Other Income	60.4	58.7
Adjusted Operating Revenue	2,987.4	3,015.1
Adjusted Operating Income (Loss)	273.5	346.1
Operating Segments | Unum US
Segment Reporting Information
Premium Income	1,525.8	1,527.7
Net Investment Income	179.7	179.6
Other Income	40.4	40.2
Adjusted Operating Revenue	1,745.9	1,747.5
Adjusted Operating Income (Loss)	115.7	261.8
Operating Segments | Unum International
Segment Reporting Information
Premium Income	174.4	164.6
Net Investment Income	26	26.5
Other Income	0.1	0
Adjusted Operating Revenue	200.5	191.1
Adjusted Operating Income (Loss)	26.4	19.4
Operating Segments | Colonial Life
Segment Reporting Information
Premium Income	426.4	434.7
Net Investment Income	37.7	37.7
Other Income	0.2	0.3
Adjusted Operating Revenue	464.3	472.7
Adjusted Operating Income (Loss)	73.3	81.1
Operating Segments | Closed Block
Segment Reporting Information
Premium Income	251.7	244.4
Net Investment Income	297.2	336.1
Other Income	18.4	18.2
Adjusted Operating Revenue	567.3	598.7
Adjusted Operating Income (Loss)	97	29.7
Operating Segments | Corporate
Segment Reporting Information
Premium Income	0	0
Net Investment Income	8.1	5.1
Other Income	1.3	0
Adjusted Operating Revenue	9.4	5.1
Adjusted Operating Income (Loss)	$ (38.9)	$ (45.9)

Assets by Segment (Detail)

Assets by Segment (Detail) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Segment Reporting Information
Total Assets	$ 69,256.6	$ 70,625.8
Operating Segments | Unum US
Segment Reporting Information
Total Assets	18,563.1	19,034.2
Operating Segments | Unum International
Segment Reporting Information
Total Assets	4,163.6	4,206.2
Operating Segments | Colonial Life
Segment Reporting Information
Total Assets	4,817.3	4,864.3
Operating Segments | Closed Block
Segment Reporting Information
Total Assets	37,845.1	38,187.2
Operating Segments | Corporate
Segment Reporting Information
Total Assets	$ 3,867.5	$ 4,333.9

Reconciliation of Total Revenue

Reconciliation of Total Revenue and Income Before Income Tax to Operating Revenue and Operating Income (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Segment Reporting, Revenue Reconciling Item
Total Revenue	$ 3,072	$ 2,871.1
Net Realized Investment Gain (Loss)	84.6	(144)
Income Before Income Tax	198.8	202.1
Closed Block Individual Disability Reinsurance Transaction
Segment Reporting, Revenue Reconciling Item
Amortization of the Cost of Reinsurance	20
Operating Segments
Segment Reporting, Revenue Reconciling Item
Total Revenue	3,072	2,871.1
Net Realized Investment Gain (Loss)	84.6	(144)
Adjusted Operating Revenue	2,987.4	3,015.1
Income Before Income Tax	198.8	202.1
Adjusted Operating Income	273.5	346.1
Operating Segments | Closed Block Individual Disability Reinsurance Transaction
Segment Reporting, Revenue Reconciling Item
Net Realized Investment Gain (Loss)	67.6	0
Change in Benefit Reserves and Transaction Costs	(139.3)	0
Amortization of the Cost of Reinsurance	(20)	0
Operating Segments | Unrelated to Significant Transaction
Segment Reporting, Revenue Reconciling Item
Net Realized Investment Gain (Loss)	$ 17	$ (144)

Segment Information Segments -

Segment Information Segments - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2021Integer
Segment Reporting [Abstract]
Number of Operating Segments	3

Employee Benefit Plans Net Peri

Employee Benefit Plans Net Periodic Benefit Cost (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Pension Plan | UNITED KINGDOM
Defined Benefit Plans and Other Postretirement Benefit Plans
Service Cost	$ 0	$ 0
Interest Cost	1.1	1.2
Expected Return on Plan Assets	(2.5)	(2.4)
Amortization of Net Actuarial Loss	0.3	0.3
Amortization of Prior Service Cost (Credit)	0	0
Net Periodic Benefit Cost	(1.1)	(0.9)
Pension Plan | UNITED STATES
Defined Benefit Plans and Other Postretirement Benefit Plans
Service Cost	2.4	2.8
Interest Cost	16.3	18.2
Expected Return on Plan Assets	(25.2)	(26.7)
Amortization of Net Actuarial Loss	5.3	4.7
Amortization of Prior Service Cost (Credit)	0	0
Net Periodic Benefit Cost	(1.2)	(1)
Other Postretirement Benefit Plans
Defined Benefit Plans and Other Postretirement Benefit Plans
Service Cost	0	0
Interest Cost	0.8	1
Expected Return on Plan Assets	(0.1)	(0.1)
Amortization of Net Actuarial Loss	0	0
Amortization of Prior Service Cost (Credit)	(0.1)	(0.1)
Net Periodic Benefit Cost	$ 0.6	$ 0.8

Basic and Diluted Earnings Per

Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Numerator
Net Income	$ 153	$ 161
Denominator
Weighted Average Common Shares - Basic	204,133,300	203,306,000
Dilution for Assumed Exercises of Stock Options and Nonvested Stock Awards	604,000	49,700
Weighted Average Common Shares - Assuming Dilution	204,737,300	203,355,700
Net Income Per Common Share
Basic	$ 0.75	$ 0.79
Assuming Dilution	$ 0.75	$ 0.79

Stockholders' Equity and Earn_3

Stockholders' Equity and Earnings Per Common Share - Additional Information (Detail) - $ / shares	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Stockholders Equity and Earnings Per Common Share Additional Information [Abstract]
Share-based Payment Arrangement, Option, Exercise Price Range, Outstanding, Weighted Average Exercise Price	$ 24.25
Outstanding Restricted Stock Unit Grant Prices Lower Limit	12.45
Outstanding Restricted Stock Unit Grant Prices Upper Limit	$ 49.31
Antidilutive Securities Excluded from Computation of Earnings Per Share	1,600,000	1,100,000
Authorized Shares of Preferred Stock	25,000,000
Par Value Per Share of Preferred Stock	$ 0.10
Issued Shares of Preferred Stock	0

Reinsurance (Details)

Reinsurance (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019
Effects of Reinsurance
Net Realized Investment Gain (Loss)	$ 84.6	$ (144)
Transaction Costs Related to Reinsurance Transaction	245	235.6
Reinsurance Recoverables, Incurred but Not Reported Claims	9,225.8	$ 2,260.7	$ 8,378.9	$ 2,246.8
Closed Block Individual Disability Reinsurance Transaction
Effects of Reinsurance
Amortization of the Cost of Reinsurance	20
Closed Block Individual Disability Reinsurance Transaction | Phase 2
Effects of Reinsurance
Negative Ceding Commission	(18.2)
Net Realized Investment Gain (Loss)	67.6
Increase in Benefits and Change in Reserves for Future Benefits	133.1
Transaction Costs Related to Reinsurance Transaction	6.2
Reinsurance Recoverables, Incurred but Not Reported Claims	990
Prepaid Reinsurance Premiums	43.1
Deposit Contracts, Assets	5
Closed Block Individual Disability Reinsurance Transaction | Phases 1 and 2
Effects of Reinsurance
Prepaid Reinsurance Premiums	854.8
Deposit Contracts, Assets	$ 91.8

Premium Receivable, Allowance f

Premium Receivable, Allowance for Credit Loss (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020	Jan. 01, 2020
Credit Loss [Abstract]
Premium Receivable, Allowance for Credit Loss	$ 33.7	$ 32.6	$ 38.8	$ 23.8
Premiums Receivable, Gross	602.9	607.2	$ 525.8	$ 543
Premium Receivable, Credit Loss Expense (Reversal)	$ (5.1)	$ 8.8

Uncategorized Items - unm-20210

Label	Element	Value
Commercial Real Estate [Member] | Loan to Value Ratio Total [Member]
Financing Receivable, Allowance for Credit Loss	us-gaap_FinancingReceivableAllowanceForCreditLosses	$ 8,300,000