Unum (UNM) 10-K 17 Feb 21 2020 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2020	Feb. 12, 2021
Entity Information [Line Items]
Document Type	10-K
Document Annual Report	true
Amendment Flag	false
Document Period End Date	Dec. 31, 2020
Document Fiscal Year Focus	2020
Current Fiscal Year End Date	--12-31
Document Fiscal Period Focus	FY
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
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		203,731,259
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Public Float	$ 3,400,000,000
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	Dec. 31, 2020	Dec. 31, 2019
Investments
Fixed Maturity Securities - at fair value (amortized cost of $36,546.5; $41,079.3; allowance for credit losses of $6.8; $—)	$ 44,137.3	$ 47,443.7
Mortgage Loans (net of allowance for credit losses of $13.1; $—)	2,432.1	2,397
Policy Loans	3,683.9	3,779.5
Other Long-term Investments	960.2	844.2
Short-term Investments	1,470	1,294.5
Total Investments	52,683.5	55,758.9
Other Assets
Cash and Bank Deposits	197	84.1
Accounts and Premiums Receivable (net of allowance for credit losses of $38.8; $10.3)	1,519.3	1,602.9
Reinsurance Recoverable (net of allowance for credit losses of $11.7; $—)	10,666	4,780.7
Accrued Investment Income	611.4	693
Deferred Acquisition Costs	2,272.6	2,324
Goodwill	353	351.7
Property and Equipment	498	534.1
Income Taxes Receivable	72.7	0
Other Assets	1,752.3	884
Total Assets	70,625.8	67,013.4
Liabilities
Policy and Contract Benefits	1,855.4	1,745.5
Reserves for Future Policy and Contract Benefits	49,653	47,780.1
Unearned Premiums	349.3	363.9
Other Policyholders' Funds	1,663.9	1,599.7
Income Tax Payable	0	256.7
Deferred Income Tax	416.1	95.4
Short-term debt	0	399.7
Long-term Debt	3,345.7	2,926.9
Other Liabilities	2,471.4	1,880.5
Total Liabilities	59,754.8	57,048.4
Commitments and Contingent Liabilities - Note 14
Stockholders' Equity
Common Stock, $0.10 par; authorized: 725,000,000 shares; issued: 306,566,572 and 305,813,326 shares	30.7	30.6
Additional Paid-in Capital	2,376.2	2,348.1
Accumulated Other Comprehensive Income	374.2	37.3
Retained Earnings	11,269.6	10,728.7
Treasury Stock - at cost: 102,876,514 shares	(3,179.7)	(3,179.7)
Total Stockholders' Equity	10,871	9,965
Total Liabilities and Stockholders' Equity	$ 70,625.8	$ 67,013.4

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Investments
Amortized Cost of Fixed Maturity Securities	$ 36,546.5	$ 41,079.3
Debt Securities, Available-for-sale, Allowance for Credit Loss for Fixed Maturity Securities	6.8	0
Allowance for credit losses for Mortgage Loans	13.1	0
Other Assets
Accounts Receivable, after Allowance for Credit Loss	38.8	10.3
Reinsurance Recoverable, Allowance for Credit Loss	$ 11.7	$ 0
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	306,566,572	305,813,326
Treasury Stock, Shares at Cost	102,876,514	102,876,514

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue
Premium Income	$ 9,378.1	$ 9,365.6	$ 8,986.1
Net Investment Income	2,360.7	2,435.3	2,453.7
Net Realized Investment Gain (Loss)	1,199.1	(23.2)	(39.5)
Other Income	224.2	221.2	198.2
Total Revenue	13,162.1	11,998.9	11,598.5
Benefits and Expenses
Benefits and Change in Reserves for Future Benefits	8,972.9	7,496.2	8,020.4
Commissions	1,057.3	1,122.7	1,108.4
Interest and Debt Expense	188.2	177.4	167.3
Cost Related to Early Retirement of Debt	0	27.3	0
Deferral of Acquisition Costs	(576.2)	(658.6)	(668)
Amortization of Deferred Acquisition Costs	606.1	609.9	565.5
Compensation Expense	953.2	898.3	885.9
Other Expenses	996.6	943.6	891.2
Total Benefits and Expenses	12,198.1	10,616.8	10,970.7
Income Before Income Tax	964	1,382.1	627.8
Income Tax
Current	(116.6)	274.8	227.4
Deferred	287.6	7	(123)
Total Income Tax	171	281.8	104.4
Net Income	$ 793	$ 1,100.3	$ 523.4
Net Income Per Common Share
Basic	$ 3.89	$ 5.25	$ 2.38
Assuming Dilution	$ 3.89	$ 5.24	$ 2.38

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Net Income	$ 793	$ 1,100.3	$ 523.4
Other Comprehensive Income (Loss)
Change in Net Unrealized Gain on Securities Before Adjustment (net of tax expense (benefit) of $250.2; $757.0; $(614.2))	983	2,870.9	(2,314.5)
Change in Adjustment to Deferred Acquisition Costs and Reserves for Future Policy and Contract Benefits, Net of Reinsurance (net of tax expense (benefit) of $(138.2); $(511.7); $371.7)	(531.2)	(1,942.6)	1,411.8
Change in Net Gain on Hedges (net of tax benefit of $23.8; $17.0; $8.2)	(90)	(62.8)	(31.7)
Change in Foreign Currency Translation Adjustment (net of tax expense (benefit) of $(4.3); $0.2; $(0.6))	20.3	23.6	(50.7)
Change in Unrecognized Pension and Postretirement Benefit Costs (net of tax expense (benefit) of $(34.8); $(9.3); $17.0)	45.2	37.6	(60.9)
Total Other Comprehensive Income (Loss)	336.9	851.5	(924.2)
Comprehensive Income	$ 1,129.9	$ 1,951.8	$ (400.8)

STATEMENT OF COMPREHENSIVE INCO

STATEMENT OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Change in Net Unrealized Gain on Securities Before Adjustment, Tax Expense (Benefit)	$ 250.2	$ 757	$ (614.2)
Change in Adjustment to Deferred Acquisition Costs and Reserves for Future Policy and Contract Benefits, Net of Reinsurance, Tax Expense (Benefit)	(138.2)	(511.7)	371.7
Change in Net Gain on Hedges, Tax Expense (Benefit)	(23.8)	(17)	(8.2)
Change in Foreign Currency Translation Adjustment, Tax Expense (Benefit)	(4.3)	0.2	(0.6)
Change in Unrecognized Pension and Postretirement Benefit Costs, Tax Expense (Benefit)	$ (34.8)	$ (9.3)	$ 17

CONSOLIDATED STATEMENTS OF STOC

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Millions	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss)Cumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Income (Loss)Restatement Adjustment	Retained Earnings	Retained EarningsCumulative Effect, Period of Adoption, Adjustment	Retained EarningsRestatement Adjustment	Treasury Stock
Balance at Beginning of Year at Dec. 31, 2017		$ 30.5	$ 2,303.3	$ 127.5		$ 110	$ 9,542.2		$ 9,556.7	$ (2,428.6)
Balance at Beginning of Year (Accounting Standards Update 2016-01) at Dec. 31, 2017					$ (17.5)			$ 14.5
Increase (Decrease) in Stockholders' Equity
Common Stock Activity		0	18.4
Other Comprehensive Income (Loss)	$ (924.2)			(924.2)
Net Income	523.4						523.4
Dividends to Stockholders (per common share: $1.14; $1.09; $0.98)							(217)
Purchases of Treasury Stock										(350.7)
Balance at End of Year at Dec. 31, 2018	8,621.8	30.5	2,321.7	(814.2)		(814.2)	9,863.1		9,859.7	(2,779.3)
Balance at End of Year (Accounting Standards Update 2016-01) at Dec. 31, 2018					0
Balance at End of Year (Accounting Standards Update 2016-02) at Dec. 31, 2018								(3.4)
Increase (Decrease) in Stockholders' Equity
Common Stock Activity		0.1	26.4
Other Comprehensive Income (Loss)	851.5			851.5
Net Income	1,100.3						1,100.3
Dividends to Stockholders (per common share: $1.14; $1.09; $0.98)							(231.3)
Purchases of Treasury Stock										(400.4)
Balance at End of Year at Dec. 31, 2019	9,965	30.6	2,348.1	37.3		$ 37.3	10,728.7		$ 10,709.8	(3,179.7)
Balance at End of Year (Accounting Standards Update 2016-01) at Dec. 31, 2019					$ 0
Balance at End of Year (Accounting Standards Update 2016-13) at Dec. 31, 2019								$ (18.9)
Increase (Decrease) in Stockholders' Equity
Common Stock Activity		0.1	28.1
Other Comprehensive Income (Loss)	336.9			336.9
Net Income	793						793
Dividends to Stockholders (per common share: $1.14; $1.09; $0.98)							(233.2)
Purchases of Treasury Stock										0
Balance at End of Year at Dec. 31, 2020	$ 10,871	$ 30.7	$ 2,376.2	$ 374.2			$ 11,269.6			$ (3,179.7)

CONSOLIDATED STATEMENTS OF ST_2

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Stockholders' Equity [Abstract]
Dividends to Stockholders (per common share: $1.14; $1.09; $0.98)	$ 1.14	$ 1.09	$ 0.98

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash Flows from Operating Activities
Net Income	$ 793	$ 1,100.3	$ 523.4
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities
Change in Receivables	242.9	37.5	(4.7)
Change in Deferred Acquisition Costs	29.9	(48.7)	(102.5)
Change in Insurance Reserves and Liabilities	1,610	376.1	1,193.1
Change in Income Taxes	(31.3)	248.2	(39.1)
Change in Other Accrued Liabilities	160.1	51.3	(10.1)
Non-cash Components of Net Investment Income	(120.5)	(237.9)	(211.1)
Net Realized Investment (Gain) Loss	(1,199.1)	23.2	39.5
Depreciation	113.6	110.1	101.4
Cash Related to Reinsurance Agreement	(1,084.6)	0	0
Other, Net	83.5	81.5	46.6
Net Cash Provided by Operating Activities	597.5	1,741.6	1,536.5
Cash Flows from Investing Activities
Proceeds from Sales of Fixed Maturity Securities	990.8	955.2	642.5
Proceeds from Maturities of Fixed Maturity Securities	2,052.4	2,401	2,815.4
Proceeds from Sales and Maturities of Other Investments	237	363.5	454
Purchase of Fixed Maturity Securities	(3,169.6)	(4,022.4)	(3,861.7)
Purchase of Other Investments	(440.6)	(568.5)	(623.2)
Net Sales (Purchases) of Short-term Investments	(133.1)	(267.6)	200.5
Net Increase (Decrease) in Payables for Collateral on Investments	314.5	(104.1)	(268.1)
Acquisition of Business (Net of Cash Acquired)	0	0	(145.4)
Net Purchases of Property and Equipment	(119.1)	(150.9)	(144.1)
Other, Net	0	(0.3)	0
Net Cash Used by Investing Activities	(267.7)	(1,393.5)	(930.1)
Cash Flows from Financing Activities
Short-term Debt Repayment	(400)	0	(200)
Issuance of Long-term Debt	494.1	841.9	290.7
Long-term Debt Repayment	(80)	(493.1)	(60)
Cost Related to Early Retirement of Debt	0	25.9	0
Issuance of Common Stock	4.4	6.1	4.6
Repurchase of Common Stock	0	(400.3)	(356.2)
Dividends Paid to Stockholders	(231.9)	(229.2)	(215.6)
Cash Received Related to Active Life Volatility Cover Agreement	62.1	0	0
Other, Net	(65.6)	(57.5)	(53.3)
Net Cash Used by Financing Activities	(216.9)	(358)	(589.8)
Net Increase (Decrease) in Cash and Bank Deposits	112.9	(9.9)	16.6
Cash and Bank Deposits at Beginning of Year	84.1	94	77.4
Cash and Bank Deposits at End of Year	$ 197	$ 84.1	$ 94

Significant Accounting Policies

Significant Accounting Policies	12 Months Ended
	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Significant Accounting Policies	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). Such accounting principles differ from statutory accounting principles (see Note 16). Intercompany transactions have been eliminated. Description of Business : We are a leading provider of financial protection benefits in the United States, the United Kingdom, and Poland. Our products include disability, life, accident, critical illness, dental and vision, and other related services. We market our products primarily through the workplace. We have three principal operating business segments: Unum US, Unum International, and Colonial Life. Our other reporting segments are Closed Block and Corporate. See Note 13 for further discussion of our operating segments. Use of Estimates : The preparation of financial statements in conformity with GAAP requires us to make estimates and assumptions that affect amounts reported in the financial statements and accompanying notes. Such estimates and assumptions could change in the future as more information becomes known, which could impact the amounts reported and disclosed herein. Fixed Maturity Securities : Fixed maturity securities include long-term bonds and redeemable preferred stocks. Our fixed maturity securities are classified as available-for-sale and reported at fair value. Changes in the fair value of available-for-sale fixed maturity securities, except for amounts related to impairment and credit losses recognized in earnings, are reported as a component of other comprehensive income. These amounts are net of income tax and valuation adjustments to deferred acquisition costs and reserves for future policy and contract benefits which would have been recorded had the related unrealized gain or loss on these securities been realized. Interest income is recorded as part of net investment income when earned, using an effective yield method giving effect to amortization of premium and accretion of discount. Included within fixed maturity securities are mortgage-backed and asset-backed securities. We recognize investment income on these securities using a constant effective yield based on projected prepayments of the underlying loans and the estimated economic life of the securities. Actual prepayment experience is reviewed periodically, and effective yields are recalculated when differences arise between prepayments originally projected and the actual prepayments received and currently projected. The effective yield is recalculated on a retrospective basis, and the adjustment is reflected in net investment income. For fixed maturity securities on which collection of investment income is uncertain, we discontinue the accrual of investment income and recognize investment income when interest and dividends are received. Payment terms specified for fixed maturity securities may include a prepayment penalty for unscheduled payoff of the investment. Prepayment penalties are recognized as investment income when received. In determining when a decline in fair value below amortized cost of a fixed maturity security is a credit loss, we evaluate available information, both positive and negative, in reaching our conclusions. In particular, we consider the strength of the issuer's balance sheet, its debt obligations and near-term funding requirements, 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. Although all available and applicable factors are considered in our analysis, our expectation of recovering the entire amortized cost basis of the security, whether we intend to sell the security, whether it is more likely than not that we will be required to sell the security before recovery of its amortized cost, and whether the security is current on principal and interest payments are the most critical factors in determining whether impairments represent credit losses. The significance of the decline in value is also an important factor, but we generally do not record an impairment loss based solely on this factor, since often other more relevant factors will impact our evaluation of a security. For securities with a decline in fair value below amortized costs which we intend to sell or more likely than not will be required to sell before recovery in value, the amortized cost of the investment is written down to fair value through earnings, and an impairment loss is recognized in the current period. For securities that we believe are impaired and which we do not intend to sell and it is not more likely than not that we will be required to sell before recovery in value, we calculate an allowance for credit losses recognized in earnings which generally represents the difference between the amortized cost of the security and 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 and limited by the difference between amortized cost and fair value of the security. For fixed maturity securities for which we have recognized an allowance for credit loss through earnings, if through subsequent evaluation there is a significant increase in expected cash flows, the allowance is reduced and is recognized as a reduction to credit losses in the current period. See Notes 2 and 3. Mortgage Loans : Mortgage loans are generally held for investment and are carried at amortized cost less an allowance for expected credit losses. Interest income is accrued on the principal amount of the loan based on the loan's contractual interest rate. Prepayment penalties are recognized as investment income when received. For mortgage loans on which collection of interest income is uncertain, we discontinue the accrual of interest and recognize it in the period when an interest payment is received. We typically do not resume the accrual of interest on mortgage loans on nonaccrual status until there are significant improvements in the underlying financial condition of the borrower. We consider a loan to be delinquent if full payment is not received in accordance with the contractual terms of the loan. 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. 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 impairment. 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. Additions and reductions to our allowance for credit losses on mortgage loans are reported as a component of net realized investment gains and losses. See Note 3. Policy Loans : Policy loans are presented at unpaid balances directly related to policyholders. Interest income is accrued on the principal amount of the loan based on the loan's contractual interest rate. Included in policy loans are $3,390.6 million and $3,490.6 million of policy loans ceded to reinsurers at December 31, 2020 and 2019, respectively. Other Long-term Investments : Other long-term investments are comprised primarily of tax credit partnerships, private equity partnerships, and real estate. Tax credit partnerships in which we have invested were formed for the purpose of investing in the construction and rehabilitation of low-income housing. Because the partnerships are structured such that there is no return of principal, the primary sources of investment return from our tax credit partnerships are tax credits and tax benefits derived from passive losses on the investments, both of which may exhibit variability over the life of the investment. These partnerships are accounted for using either the proportional or the effective yield method, depending primarily on whether the tax credits are guaranteed through a letter of credit, a tax indemnity agreement, or another similar arrangement. Tax credits received from these partnerships are reported in our consolidated statements of income as either a reduction of premium tax or a reduction of income tax. The amortization of the principal amount invested in these partnerships is reported as a component of either premium tax or income tax. Our investments in private equity partnerships are passive in nature and represent funds that are primarily invested in private credit, private equity, and real assets. We account for our investments in these partnerships using either the equity method or at fair value through net income depending on the level of ownership and the degree of our influence over partnership operating and financial policies. For investments in partnerships accounted for under the equity method, we report our investments at our share of the partnership's net asset value (NAV) and record our portion of partnership earnings as a component of net investment income. For investments in partnerships accounted for at fair value through net income, we also report our investments at our share of the partnership's NAV as a practical expedient for fair value with increases or decreases recorded as a component of net investment income. Distributions received from the funds arise from income generated by the underlying investments as well as the liquidation of the underlying investments and there is generally not a public market for these investments. Investment real estate is primarily comprised of property held for the production of income and property held for sale. Property held for the production of income is carried at cost less accumulated depreciation and any write-downs to fair value for impairment losses. Depreciation is recorded on a straight-line basis over the estimated useful life of the asset. A review for impairment is made whenever events or circumstances indicate that the carrying value may not be recoverable. An impairment loss is recognized when the carrying value of the property exceeds the expected undiscounted cash flows generated from the property, at which point the carrying value is written down to an estimated fair value. Real estate held for sale is carried at the lower of depreciated cost or fair value less estimated selling costs and is not further depreciated once classified as such. See Notes 2 and 3 for further discussion of our other long-term investments. Short-term Investments : Short-term investments are carried at cost. Short-term investments include investments maturing within one year of purchase, such as corporate commercial paper and U.S. Treasury bills, bank term deposits, and other cash accounts and cash equivalents earning interest. Cash and Bank Deposits : Cash and bank deposits include cash on hand and non-interest bearing cash and deposit accounts. Derivative Financial Instruments : Derivative financial instruments (including certain derivative instruments embedded in other contracts) are recognized as either other long-term investments or other liabilities in our consolidated balance sheets and are reported at fair value. The accounting for a derivative depends on whether it has been designated and qualifies as part of a hedging relationship, and further, on the type of hedging relationship. To qualify for hedge accounting, at the inception of the hedging transaction, we formally document the risk management objective and strategy for undertaking the hedging transaction, as well as the designation of the hedge as either a fair value hedge or a cash flow hedge. Included in this documentation is how the hedging instrument is expected to hedge the designated risk(s) related to specific assets or liabilities on the balance sheet or to specific forecasted transactions as well as a description of the method that will be used to retrospectively and prospectively assess the hedging instrument's effectiveness. A derivative designated as a hedging instrument must be assessed as being highly effective in offsetting the designated risk(s) of the hedged item. Hedge effectiveness is formally assessed at inception and periodically throughout the life of the designated hedging relationship, using qualitative and quantitative methods. Qualitative methods include comparison of critical terms of the derivative to the hedged item. Quantitative methods include regression or other statistical analysis of changes in fair value or cash flows associated with the hedge relationship. Changes in the fair value of a derivative designated as a fair value hedge and changes in the fair value of the hedged item attributable to the risk being hedged are recognized in earnings as a component of net realized investment gain or loss during the period of change in fair value. For gains or losses on the derivative instrument that are excluded from the assessment of hedge effectiveness, those gains and losses are recognized in other comprehensive income or loss and amortized into earnings in the same income statement line as the related hedged item. The gain or loss on the termination of a fair value hedge is recognized in earnings as a component of net realized investment gain or loss during the period in which the termination occurs. When interest rate swaps are used in hedge accounting relationships, periodic settlements are recorded in the same income statement line as the related settlements of the hedged items. Changes in the fair value of a derivative designated as a cash flow hedge are reported in other comprehensive income and reclassified into earnings and reported on the same income statement line item as the hedged item and in the same period or periods during which the hedged item affects earnings. The gain or loss on the termination of an effective cash flow hedge is reported in other comprehensive income and reclassified into earnings and reported on the same income statement line item as the hedged item and in the same period or periods during which the hedged item affects earnings. Gains or losses on the termination of ineffective fair value or cash flow hedges are reported in earnings as a component of net realized investment gain or loss. In the event a hedged item is disposed of or the anticipated transaction being hedged is no longer likely to occur, we will terminate the related derivative and recognize the gain or loss on termination in current earnings as a component of net realized investment gain or loss. In the event a hedged item is disposed of subsequent to the termination of the hedging transaction, we reclassify any remaining gain or loss on the hedge out of accumulated other comprehensive income into earnings as a component of the same income statement line item wherein we report the gain or loss on disposition of the hedged item. For a derivative not designated as a hedging instrument, changes in the fair value of the derivative, together with the payment of periodic fees, if applicable, are recognized in earnings as a component of net realized investment gain or loss during the period of change in fair value. Cash flow activity from the settlement of derivative contracts is reported in the consolidated statements of cash flows as a component of proceeds from sales and maturities of other investments. In our consolidated balance sheets, we do not offset fair value amounts recognized for derivatives executed with the same counterparty under a master netting agreement and fair value amounts recognized for the right to reclaim cash collateral or the obligation to return cash collateral arising from those master netting agreements. See Notes 2, 3, and 4. Fair Value Measurement : Certain assets and liabilities are reported at fair value in our consolidated balance sheets and in our notes to our consolidated financial statements. We define fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. Therefore, fair value represents an exit price, not an entry price. The exit price objective applies regardless of our intent and/or ability to sell the asset or transfer the liability at the measurement date. Assets or liabilities with readily available actively 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. When actively quoted prices are not available, fair values are based on quoted prices in markets that are not active, quoted prices for similar but not identical assets or liabilities, or other observable inputs. If observable inputs are not available, unobservable inputs and/or adjustments to observable inputs requiring management judgment are used to determine fair value. We categorize our assets and liabilities measured at estimated fair value into a three-level hierarchy, based on the significance of the inputs. The fair value hierarchy gives the highest priority to inputs which are unadjusted and represent quoted prices in active markets for identical assets or liabilities (Level 1) and the lowest priority to unobservable inputs (Level 3). See Note 2. Realized Investment Gains and Losses : Realized investment gains and losses are reported as a component of revenue in the consolidated statements of income and are based upon specific identification of the investments sold. See Note 3. Allowance for Credit Losses on Premiums Receivable : We establish an allowance for credit losses on premiums receivable, which is deducted from the gross amount of our receivable balance, to present the net amount we expect to collect on this asset. The allowance is forward-looking in nature and is calculated based on considerations regarding both historical events and future expectations. Periodic changes in the allowance are recorded through earnings. The allowance on our premiums receivable is primarily determined using an aging analysis as well as historical lapse and delinquency rates by line of business, adjusted for key factors that may impact our future expectation of premium receipts such as changes in customer demographics, business practices, economic conditions, and product offerings. We write off premiums receivable amounts when determined to be uncollectible, which is based on various factors, including the aging of premiums receivable past the due date and specific communication with customers. At January 1, 2020 and December 31, 2020, the allowance for expected credit losses on premium receivables was $23.8 million and $38.8 million, respectively, on gross premium receivables of $543.0 million and $525.8 million, respectively. The allowance at January 1, 2020 includes amounts that were previously established at December 31, 2019. The allowance increased $15.0 million during the year ended December 31, 2020, primarily due to the uncertainty of collectability resulting from the impacts of COVID-19, partially offset by premium due write-offs and a decrease in the premium due balance. The primary factors considered in establishing the additional allowance were the recent increase in unemployment levels and the general uncertainty around the financial condition of some of our customers. Deferred Acquisition Costs : Incremental direct costs associated with the successful acquisition of new or renewal insurance contracts have been deferred. Such costs include commissions, other agency compensation, certain selection and policy issue expenses, and certain field expenses. Acquisition costs that do not vary with the production of new business, such as commissions on group products which are generally level throughout the life of the policy, are excluded from deferral. Deferred acquisition costs are subject to recoverability testing at the time of policy issue and loss recognition testing in subsequent years. Deferred acquisition costs related to non-interest sensitive policies are amortized in proportion to the premium income we expect to receive over the lives of the policies. Deferred acquisition costs related to interest sensitive policies are amortized over the lives of the policies in relation to the present value of estimated gross profits from surrender charges, mortality margins, investment returns, and expense margins. Deviations from projections result in a change to the rate of amortization in the period during which such events occur. Generally, the amortization periods for these policies approximate the estimated lives of the policies. For certain products, policyholders can elect to modify product benefits, features, rights, or coverages by exchanging a contract for a new contract or by amendment, endorsement, or rider to a contract, or by the election of a feature or coverage within a contract. These transactions are known as internal replacement transactions. Internal replacement transactions wherein the modification does not substantially change the policy are accounted for as continuations of the replaced contracts. Unamortized deferred acquisition costs from the original policy continue to be amortized over the expected life of the new policy, and the costs of replacing the policy are accounted for as policy maintenance costs and expensed as incurred. Internal replacement transactions, principally on group contracts, that result in a policy that is substantially changed are accounted for as an extinguishment of the original policy and the issuance of a new policy. Unamortized deferred acquisition costs on the original policy that was replaced are immediately expensed, and the costs of acquiring the new policy are capitalized and amortized in accordance with our accounting policies for deferred acquisition costs. Loss recognition testing is performed on an annual basis, or more frequently if appropriate, using best estimate assumptions as to future experience as of the date of the test. Insurance contracts are grouped for each major product line within a segment when we perform the loss recognition tests. If loss recognition testing indicates that deferred acquisition costs are not recoverable, the deficiency is charged to expense. Goodwill : Goodwill is the excess of the amount paid to acquire a business over the fair value of the net assets acquired. We review the carrying amount of goodwill for impairment on an annual basis, or more frequently if events or changes in circumstances indicate that the carrying amount might not be recoverable. Goodwill impairment testing compares the fair value of a reporting unit with its carrying amount, including goodwill. If the fair value of the reporting unit to which the goodwill relates is less than the carrying amount of the reporting unit, an impairment charge is recognized for the amount by which the carrying amount exceeds the fair value of the reporting unit in an amount not to exceed the total amount of goodwill allocated to the reporting unit. Property and Equipment : Property and equipment is reported at cost less accumulated depreciation, which is calculated on the straight-line method over the estimated useful life. The accumulated depreciation for property and equipment was $1,239.9 million and $1,195.3 million as of December 31, 2020 and 2019, respectively. Value of Business Acquired : Value of business acquired represents the present value of future profits recorded in connection with the acquisition of a block of insurance policies. The asset is amortized based upon expected future premium income for non-interest sensitive insurance policies and estimated future gross profits from surrender charges, mortality margins, investment returns, and expense margins for interest sensitive insurance policies. The value of business acquired, which is included in other assets in our consolidated balance sheets, was $83.8 million and $88.7 million at December 31, 2020 and 2019, respectively. The accumulated amortization for value of business acquired was $153.7 million and $144.1 million as of December 31, 2020 and 2019, respectively. The amortization of value of business acquired, which is included in other expenses in the consolidated statements of income, was $6.1 million, $7.1 million, and $6.4 million for the years ended December 31, 2020, 2019, and 2018, respectively. We periodically review the carrying amount of value of business acquired using the same methods used to evaluate deferred acquisition costs. Policy and Contract Benefits : Policy and contract benefits represent amounts paid and expected to be paid based on reported losses and estimates of incurred but not reported losses for non-interest sensitive life and accident and health products. For interest sensitive products, benefits are the amounts paid and expected to be paid on insured claims in excess of the policyholders' policy fund balances. Reserves for Policy and Contract Benefits : Policy reserves represent future policy and contract benefits for claims not yet incurred. Policy reserves for non-interest sensitive life and accident and health products are determined using the net level premium method. The reserves are calculated based upon assumptions as to interest, persistency, morbidity, and mortality that were appropriate at the date of issue. Discount rate assumptions are based on actual and expected net investment returns. Persistency assumptions are based on our actual historical experience adjusted for future expectations. Claim incidence and claim resolution rate assumptions related to morbidity and mortality are based on actual experience or industry standards adjusted as appropriate to reflect our actual experience and future expectations. The assumptions vary by plan, year of issue, and policy duration and include a provision for adverse deviation. Policy reserves for group single premium annuities are developed on a net single premium method. The reserves are calculated based on assumptions as to interest, mortality, and retirement that were appropriate at the date of issue. Mortality assumptions are based upon industry standards adjusted as appropriate to reflect our actual experience and future expectations. The assumptions vary by year of issue. Policy reserves for interest sensitive products are principally policyholder account values. Policy reserves require ongoing loss recognition testing. We perform loss recognition tests on our policy reserves annually, or more frequently if appropriate, using best estimate assumptions as of the date of the test, without a provision for adverse deviation. We group the policy reserves for each major product line within a segment when we perform the loss recognition tests. If the policy reserves determined using these best estimate assumptions are higher than our existing policy reserves net of any deferred acquisition cost balance, the existing policy reserves are increased or deferred acquisition costs are reduced to immediately recognize the deficiency. This becomes the new basis for policy reserves going forward, subject to future loss recognition testing. Claim reserves represent future policy and contract benefits for claims that have been incurred or are estimated to have been incurred but not yet reported to us. Our claim reserves relate primarily to disability and long-term care policies and are calculated based on assumptions as to interest and claim resolution rates that are currently appropriate. Claim resolution rate assumptions are based on our actual experience. The interest rate assumptions used for discounting claim reserves are based on projected portfolio yield rates, after consideration for defaults and investment expenses, for the assets supporting the liabilities for the various product lines. Unlike policy reserves for which assumptions are generally established and locked in at the time of policy issuance, claim reserves are subject to revision as current claim experience and projections of future factors affecting claim experience change. Claim reserves do not include a provision for adverse deviation. See Note 6. Policyholders Funds : Policyholders' funds represent customer deposits plus interest credited at contract rates. We control interest rate risk by investing in quality assets which have an aggregate duration that closely matches the expected duration of the liabilities. Income Tax : Deferred taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial statement purposes and the amounts used for income tax purposes. Deferred taxes have been measured using enacted statutory income tax rates and laws that are currently in effect. We record adjustments to our deferred taxes resulting from tax rate changes through income as of the date of enactment. We record deferred tax assets for tax positions taken in the U.S. and other tax jurisdictions based on our assessment of whether a position is more likely than not to be sustained upon examination based solely on its technical merits. A valuation allowance is established for deferred tax assets when it is more likely than not that an amount will not be realized. We follow an aggregate portfolio approach to release disproportionate tax effects from accumulated other comprehensive income upon disposal of an entire business segment's portfolio. See Note 7. Short-term and Long-term Debt : Debt is generally carried at the unpaid principal balance, net of unamortized discount or premium and deferred debt issuance costs. Short-term debt consists of debt due within the next twel

Fair Values of Financial Instru

Fair Values of Financial Instruments	12 Months Ended
	Dec. 31, 2020
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. See Note 1. 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 2020, 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 2019. 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 December 31, 2020, approximately 9.6 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 90.4 percent of our fixed maturity securities were valued based on non-binding quotes or other observable and unobservable inputs, as discussed below: • 74.9 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. • 10.4 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: 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 December 31, 2019 Investment Category Fair Value Redemption Term / Redemption Notice Unfunded Commitments (in millions of dollars) (in millions of dollars) Private Credit (a) $ 223.6 Not redeemable $ 152.6 39.6 Initial 2 year lock on each new investment / Quarterly after 2 year lock with 90 days notice 0.1 Total Private Credit 263.2 152.7 Private Equity (b) 149.3 Not redeemable 166.8 Real Assets (c) 173.8 Not redeemable 130.6 30.4 Quarterly / 90 days notice 25.0 Total Real Assets 204.2 155.6 Total Partnerships $ 616.7 $ 475.1 (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 December 31, 2020, the estimated remaining life of the investments that do not allow for redemptions is approximately 37 percent in the next 3 years, 38 percent during the period from 3 to 5 years, 22 percent during the period from 5 to 10 years, and 3 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 December 31, 2020, the estimated remaining life of the investments that do not allow for redemptions is approximately 20 percent in the next 3 years, 35 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 December 31, 2020, the estimated remaining life of the investments that do not allow for redemptions is approximately 12 percent in the next 3 years, 23 percent during period from 3 to 5 years, 64 percent during the period from 5 to 10 years, and 1 percent during the period from 10 to 15 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: 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 December 31, 2019 Level 1 Level 2 Level 3 NAV Total (in millions of dollars) Assets Fixed Maturity Securities United States Government and Government Agencies and Authorities $ 412.8 $ 988.9 $ — $ — $ 1,401.7 States, Municipalities, and Political Subdivisions — 3,321.6 41.8 — 3,363.4 Foreign Governments — 995.9 21.8 — 1,017.7 Public Utilities 171.1 7,546.5 14.6 — 7,732.2 Mortgage/Asset-Backed Securities — 1,444.6 34.1 — 1,478.7 All Other Corporate Bonds 4,114.4 27,695.5 600.5 — 32,410.4 Redeemable Preferred Stocks — 39.6 — — 39.6 Total Fixed Maturity Securities 4,698.3 42,032.6 712.8 — 47,443.7 Other Long-term Investments Derivatives Foreign Exchange Contracts — 27.0 — — 27.0 Credit Default Swaps — 0.5 — — 0.5 Total Derivatives — 27.5 — — 27.5 Perpetual Preferred Equity Securities — 28.0 4.6 — 32.6 Private Equity Partnerships — — — 616.7 616.7 Total Other Long-term Investments — 55.5 4.6 616.7 676.8 Total Financial Instrument Assets Carried at Fair Value $ 4,698.3 $ 42,088.1 $ 717.4 $ 616.7 $ 48,120.5 Liabilities Other Liabilities Derivatives Interest Rate Swaps $ — $ 0.6 $ — $ — $ 0.6 Foreign Exchange Contracts — 34.0 — — 34.0 Embedded Derivative in Modified Coinsurance Arrangement — — 22.8 — 22.8 Total Derivatives — 34.6 22.8 — 57.4 Total Financial Instrument Liabilities Carried at Fair Value $ — $ 34.6 $ 22.8 $ — $ 57.4 Changes in assets and liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3) are as follows: Year Ended December 31, 2020 Fair Value Beginning Total Realized and Purchases Sales Level 3 Transfers Fair Value End of Change in Unrealized Earnings OCI 1 Into Out of OCI 1 Earnings (in millions of dollars) Fixed Maturity Securities States, Municipalities, and Political Subdivisions $ 41.8 $ — $ 2.2 $ — $ — $ — $ (28.5) $ 15.5 $ 1.7 $ — Foreign Governments 21.8 — — — — — — 21.8 — — Public Utilities 14.6 — 3.8 — — 175.9 (8.6) 185.7 3.7 — Mortgage/Asset-Backed Securities 34.1 — (3.0) — (67.9) 118.1 — 81.3 (3.5) — All Other Corporate Bonds 600.5 — 29.8 194.7 (36.1) 343.1 (188.9) 943.1 26.7 — Total Fixed Maturity Securities 712.8 — 32.8 194.7 (104.0) 637.1 (226.0) 1,247.4 28.6 — Perpetual Preferred Equity Securities 4.6 0.1 — — — — — 4.7 — 0.1 Embedded Derivative in Modified Coinsurance Arrangement (22.8) (17.0) — — — — — (39.8) — (17.0) 1 Other Comprehensive Income (Loss) Year Ended December 31, 2019 Total Realized and Fair Value Beginning Earnings Other Purchases Sales Level 3 Transfers Fair Value End of Into Out of (in millions of dollars) Fixed Maturity Securities States, Municipalities, and Political Subdivisions $ — $ — $ 2.8 $ 13.3 $ — $ 25.7 $ — $ 41.8 Foreign Governments 31.4 — 0.6 — (10.2) — — 21.8 Public Utilities 84.7 — 0.8 — — 6.0 (76.9) 14.6 Mortgage/Asset-Backed Securities — — (2.7) — — 36.8 — 34.1 All Other Corporate Bonds 1,495.8 — (3.1) 93.0 (86.0) 190.6 (1,089.8) 600.5 Redeemable Preferred Stocks 21.1 — — — — — (21.1) — Total Fixed Maturity Securities 1,633.0 — (1.6) 106.3 (96.2) 259.1 (1,187.8) 712.8 Perpetual Preferred Equity Securities 4.6 — — — — — — 4.6 Embedded Derivative in Modified Coinsurance Arrangement (31.1) 8.3 — — — — — (22.8) 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. 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 (b) 0.50% - 24.90% / 3.63% Perpetual Preferred Equity Securities 4.7 Market Approach Market Convention (c) Priced at Cost or Owner's Equity Embedded Derivative in Modified Coinsurance Arrangement (39.8) Discounted Cash Flows Projected Liability Cash Flows (d) Actuarial Assumptions December 31, 2019 Fair Value Valuation Method Unobservable Input Range/Weighted Average (in millions of dollars) Fixed Maturity Securities All Other Corporate Bonds - Private $ 119.2 Market Approach Lack of Marketability Volatility of Credit Market Convention (a) (b) (c) 4.56% - 4.56% / 4.56% 0.35% - 17.68% / 2.2% Priced at Par Perpetual Preferred Equity Securities 4.6 Market Approach Market Convention (c) Priced at Cost or Owner's Equity Embedded Derivative in Modified Coinsurance Arrangement (22.8) Discounted Cash Flows Projected Liability Cash Flows (d) Actuarial Assumptions (a) Represents basis point adjustments to apply a discount due to the illiquidity of an investment (b) Represents basis point adjustments for credit-specific factors (c) Represents a decision to price based on par value, cost, or owner's equity when limited data is available (d) 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 values are estimated using discounted cash flow analyses and interest rates currently being offered for similar loans to borrowers with similar credit ratings and maturities. Loans with similar characteristics are aggregated for purposes of the calculations. 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 $3,390.6 million and $3,490.6 million as of December 31, 2020 and 2019, 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: 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 Payable for Collateral on FHLB Funding Agreements — 312.2 — 312.2 312.2 Other Lia

Investments

Investments	12 Months Ended
	Dec. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Investments	65% <= 75% 1,000.3 41.1 1,053.0 43.9 > 75% <= 85% 155.8 6.4 91.4 3.8 > 85% 86.6 3.6 37.5 1.6 Total $ 2,432.1 100.0 % $ 2,397.0 100.0 % The following table presents the amortized cost of our mortgage loans by year of origination and credit quality indicators at December 31, 2020: Prior to 2016 2016 2017 2018 2019 2020 Total (in millions of dollars) Internal Rating AA $ 3.5 $ — $ — $ — $ — $ — $ 3.5 A 240.3 119.5 56.3 60.2 16.9 18.0 511.2 BBB 482.6 287.8 253.9 331.8 351.9 166.4 1,874.4 BB 29.4 — 10.5 — — — 39.9 B 16.2 — — — — — 16.2 Total Amortized Cost 772.0 407.3 320.7 392.0 368.8 184.4 2,445.2 Allowance for credit losses (2.4) (2.0) (1.9) (2.4) (2.9) (1.5) (13.1) Carrying Amount $ 769.6 $ 405.3 $ 318.8 $ 389.6 $ 365.9 $ 182.9 $ 2,432.1 Loan-to-Value Ratio <=65% $ 598.5 $ 257.5 $ 139.0 $ 77.8 $ 82.8 $ 37.2 $ 1,192.8 >65<=75% 47.2 122.5 109.9 294.8 286.0 147.2 1,007.6 >75%<=85% 78.7 27.3 37.9 13.3 — — 157.2 >85% 47.6 — 33.9 6.1 — — 87.6 Total Amortized Cost 772.0 407.3 320.7 392.0 368.8 184.4 2,445.2 Allowance for credit losses (2.4) (2.0) (1.9) (2.4) (2.9) (1.5) (13.1) Carrying Amount $ 769.6 $ 405.3 $ 318.8 $ 389.6 $ 365.9 $ 182.9 $ 2,432.1 The following table presents a rollforward of allowance for expected credit losses by loan-to-value ratio: Year Ended December 31, 2020 Beginning of Period Current Period Provisions Write-Offs Recoveries End of Period (in millions of dollars) Loan-to-Value Ratio <=65% $ 2.8 $ 0.6 $ — $ — $ 3.4 >65<=75% 4.6 2.7 — — 7.3 >75%<=85% 0.5 0.8 — — 1.3 >85% 0.4 0.7 — — 1.1 Total $ 8.3 $ 4.8 $ — $ — $ 13.1 The increase in our estimate of expected losses during the year ended December 31, 2020 is primarily due to the expected impact of COVID-19, specifically impacts to underlying commercial real estate values, and reflects market conditions at December 31, 2020. There were no troubled debt restructurings during 2020 or 2019. We had one mortgage loan which was modified in a troubled debt restructuring during the second quarter of 2018. The loan had a principal balance of $3.6 million prior to the restructuring, wherein the terms of the loan were modified to reduce monthly payments to interest-only at the current note rate and to permit a discounted payoff by September 2018. At time of restructuring, we recorded an allowance for credit losses on mortgage loans and recognized an impairment loss of $0.2 million in the second quarter of 2018. The payoff of the loan did not occur in September 2018 and the loan was considered impaired as of December 31, 2018. The loan was settled during the first quarter of 2019 resulting in an additional loss of $0.1 million. At 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 years ended December 31, 2020, 2019, or 2018. For the year ended December 31, 2020, we had no impaired mortgage loans. Our average investment in impaired mortgage loans was $0.6 million, and $2.3 million for the years ended December 31, 2019 and 2018, respectively. We did not recognize any interest income during 2020, 2019 or 2018 on mortgage loans subsequent to impairment. At December 31, 2020, we had commitments of $11.4 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 December 31, 2020, we had $0.1 million of expected credit losses related to unfunded commitments on our consolidated balance sheets. Investment Real Estate Our investment real estate balance was $106.3 million and $90.5 million at December 31, 2020 and 2019, respectively, and the associated accumulated depreciation was $97.7 million and $49.8 million at December 31, 2020 and 2019, respectively. For the year ended December 31, 2020, we recognized $36.6 million in impairments related to certain of our real estate held for investment. We did not recognize any impairments on investment real estate during 2019 and we recognized $0.6 million in impairments in 2018. 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 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. As of December 31, 2019, the carrying amount of fixed maturity securities loaned to third parties under our securities lending program was $176.4 million, for which we received collateral in the form of securities of $186.5 million. We had no outstanding repurchase agreements at December 31, 2020 or 2019. The remaining contractual maturities of our securities lending agreements disaggregated by class of collateral pledged are as follows: December 31 2020 2019 Overnight and Continuous (in millions of dollars) Borrowings United States Government and Government Agencies and Authorities $ 0.1 $ — State, Municipalities, and Political Subdivisions 0.4 — Public Utilities 0.3 — All Other Corporate Bonds 16.8 — Total Borrowings $ 17.6 $ — Gross Amount of Recognized Liability for Securities Lending Transactions 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 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: December 31 2020 2019 (in millions of dollars) Carrying Value of FHLB Common Stock $ 28.2 $ 18.5 Advances from FHLB 312.2 — Carrying Value of Collateral Posted to FHLB Fixed Maturity Securities $ 944.0 $ 182.1 Commercial Mortgage Loans 1,072.5 164.4 Total Carrying Value of Collateral Posted to FHLB $ 2,016.5 $ 346.5 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 4 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. 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 December 31, 2019 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 $ 27.5 $ — $ 27.5 $ (4.0) $ (23.5) $ — Securities Lending 176.4 — 176.4 (176.4) — — Total $ 203.9 $ — $ 203.9 $ (180.4) $ (23.5) $ — Financial Liabilities: Derivatives $ 34.6 $ — $ 34.6 $ (31.3) $ — $ 3.3 Net Investment Income Net investment income reported in our consolidated statements of income is presented below. Certain prior period amounts have been reclassified to conform to the current period presentation. Year Ended December 31 2020 2019 2018 (in millions of dollars) Fixed Maturity Securities $ 2,164.0 $ 2,213.6 $ 2,239.7 Derivatives 78.7 73.4 66.1 Mortgage Loans 108.9 103.3 110.1 Policy Loans 20.0 19.9 18.6 Other Long-term Investments Perpetual Preferred Securities 1 (2.1) 5.4 (0.2) Private Equity Partnerships 2 19.8 31.7 36.0 Other 3.9 3.9 8.4 Short-term Investments 10.5 29.0 23.7 Gross Investment Income 2,403.7 2,480.2 2,502.4 Less Investment Expenses 30.6 32.1 35.2 Less Investment Income on Participation Fund Account Assets 12.4 12.8 13.5 Net Investment Income $ 2,360.7 $ 2,435.3 $ 2,453.7 1 The net unrealized gain (loss) recognized in net investment income for the year ended December 31, 2020 related to perpetual preferred securities still held at December 31, 2020 was $(4.6) million. The net unrealized gain (loss) recognized in net investment income for the year ended December 31, 2019 related to perpetual preferred securities still held at December 31, 2019 was $3.3 million. 2 The net unrealized gain (loss) recognized in net investment income for the year ended December 31, 2020 related to private equity partnerships still held at December 31, 2020 was $(8.7) million. The net unrealized gain (loss) recognized in net investment income for the year ended December 31, 2019 related to private equity partnerships still held at December 31, 2019 was $6.8 million. See Note 2 for further discussion of private equity partnerships. Realized Investment Gain and Loss Realized investment gains and losses are as follows: Year Ended December 31 2020 2019 2018 (in millions of dollars) Fixed Maturity Securities Gross Gains on Sales 1 $ 1,332.8 $ 22.9 $ 9.7 Gross Losses on Sales (20.3) (32.6) (15.2) Credit Losses (53.6) (25.3) (17.5) Mortgage Loans and Other Invested Assets Gross Gains on Sales 1.9 4.6 0.5 Gross Losses on Sales (0.3) (0.3) — Impairment Loss (36.6) — (1.4) Credit Losses (4.6) — — Embedded Derivative in Modified Coinsurance Arrangement (17.0) 8.3 (15.2) All Other Derivatives (2.5) (0.1) 0.3 Foreign Currency Transactions (0.7) (0.7) (0.7) Net Realized Investment Gain (Loss) $ 1,199.1 $ (23.2) $ (39.5) 1 Gross gains on sales of fixed maturity securities includes gains of $1,302.3 million as a result of the reinsurance transaction that we entered into during the fourth quarter of 2020. See Note 12 for further discussion." id="sjs-B4">Fixed Maturity Securities At December 31, 2020 and 2019, 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: 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 December 31, 2019 Amortized Gross Gross Fair (in millions of dollars) United States Government and Government Agencies and Authorities $ 1,246.1 $ 156.0 $ 0.4 $ 1,401.7 States, Municipalities, and Political Subdivisions 2,863.1 507.6 7.3 3,363.4 Foreign Governments 843.5 175.2 1.0 1,017.7 Public Utilities 6,436.7 1,303.7 8.2 7,732.2 Mortgage/Asset-Backed Securities 1,377.8 101.3 0.4 1,478.7 All Other Corporate Bonds 28,273.1 4,211.2 73.9 32,410.4 Redeemable Preferred Stocks 39.0 0.6 — 39.6 Total Fixed Maturity Securities $ 41,079.3 $ 6,455.6 $ 91.2 $ 47,443.7 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. 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 December 31, 2019 Less Than 12 Months 12 Months or Greater Fair Gross Fair Gross (in millions of dollars) United States Government and Government Agencies and Authorities $ 110.2 $ 0.4 $ — $ — States, Municipalities, and Political Subdivisions 331.0 7.3 0.3 — Foreign Governments 69.4 1.0 — — Public Utilities 168.3 2.6 37.0 5.6 Mortgage/Asset-Backed Securities 47.0 0.4 3.1 — All Other Corporate Bonds 579.1 29.1 379.8 44.8 Total Fixed Maturity Securities $ 1,305.0 $ 40.8 $ 420.2 $ 50.4 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. 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 December 31, 2019 Total Unrealized Gain Position Unrealized Loss Position Gross Gain Fair Value Gross Loss Fair Value (in millions of dollars) 1 year or less $ 821.5 $ 14.5 $ 832.6 $ 0.2 $ 3.2 Over 1 year through 5 years 6,286.2 456.5 6,423.4 41.7 277.6 Over 5 years through 10 years 13,570.8 1,688.3 14,881.3 14.6 363.2 Over 10 years 19,023.0 4,195.0 22,152.6 34.3 1,031.1 39,701.5 6,354.3 44,289.9 90.8 1,675.1 Mortgage/Asset-Backed Securities 1,377.8 101.3 1,428.6 0.4 50.1 Total Fixed Maturity Securities $ 41,079.3 $ 6,455.6 $ 45,718.5 $ 91.2 $ 1,725.2 The following chart depicts an analysis of our fixed maturity security portfolio between investment-grade and below-investment-grade categories as of December 31, 2020: Gross Unrealized Loss Fair Value Gross Unrealized Gain Amount Percent of Total Gross Unrealized Loss (in millions of dollars) Investment-Grade $ 40,637.2 $ 7,371.5 $ 18.1 32.4 % Below-Investment-Grade 3,500.1 282.0 37.8 67.6 Total Fixed Maturity Securities $ 44,137.3 $ 7,653.5 $ 55.9 100.0 % 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 December 31, 2020, 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 December 31, 2020, we held 47 individual investment-grade fixed maturity securities and 21 individual below-investment-grade fixed maturity securities that were in an unrealized loss position, of which 5 investment-grade fixed maturity securities and 13 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 December 31, 2020, with respect to the fixed maturity securities for which an 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 December 31, 2020: Year Ended (in millions of dollars) Balance, beginning of period $ — Credit losses on securities for which credit losses were not previously recorded 44.5 Change in allowance due to change in intent to hold securities to maturity (37.7) Change in allowance on securities with allowance recorded in previous period — Balance, end of period $ 6.8 At December 31, 2020, we had commitments of $21.0 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 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. At December 31, 2019, the carrying amount of our variable interest entity investments that are not consolidated in our financial statements was $675.1 million, comprised of $58.4 million of tax credit partnerships and $616.7 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: Year Ended December 31 2020 2019 2018 (in millions of dollars) Income Tax Credits $ 33.2 $ 37.8 $ 41.4 Amortization, Net of Tax (21.9) (25.2) (28.1) Income Tax Benefit $ 11.3 $ 12.6 $ 13.3 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 December 31, 2020. See Note 2 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 adopted new accounting guidance that requires us to estimate an allowance for expected credit losses effective January 1, 2020. We carry our mortgage loans at amortized cost less the allowance for expected credit losses. The amortized cost of our mortgage loans was $2,445.2 million and $2,397.0 million at December 31, 2020 and December 31, 2019, respectively. The allowance for expected credit losses was $13.1 million at December 31, 2020. 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 and $8.3 million at December 31, 2020 and December 31, 2019, respectively. The carrying amount of mortgage loans by property type and geographic region are presented below. December 31 2020 2019 (in millions of dollars) Carrying Percent of Carrying Percent of Amount Total Amount Total Property Type Apartment $ 638.0 26.2 % $ 608.8 25.4 % Industrial 654.0 26.9 623.6 26.0 Office 517.8 21.3 549.3 22.9 Retail 575.6 23.7 567.5 23.7 Other 46.7 1.9 47.8 2.0 Total $ 2,432.1 100.0 % $ 2,397.0 100.0 % Region New England $ 40.0 1.6 % $ 28.9 1.2 % Mid-Atlantic 202.5 8.2 184.5 7.7 East North Central 330.4 13.6 329.2 13.7 West North Central 196.1 8.1 215.4 9.0 South Atlantic 512.0 21.1 509.2 21.2 East South Central 110.0 4.5 114.3 4.8 West South Central 257.4 10.6 246.6 10.3 Mountain 268.8 11.1 268.2 11.2 Pacific 514.9 21.2 500.7 20.9 Total $ 2,432.1 100.0 % $ 2,397.0 100.0 % 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. Mortgage loans, sorted by the applicable credit quality indicators, are as follows: December 31 2020 2019 (in millions of dollars) Carrying Amount Percent of Total Carrying Amount Percent of Total Internal Rating AA $ 3.5 0.1 % $ — — % A 510.0 21.0 % 485.6 20.3 % BBB 1,863.0 76.6 1,911.4 79.7 BB 39.4 1.6 — — B 16.2 0.7 — — Total $ 2,432.1 100.0 % $ 2,397.0 100.0 % Loan-to-Value Ratio <= 65% $ 1,189.4 48.9 % $ 1,215.1 50.7 % > 65% <= 75% 1,000.3 41.1 1,053.0 43.9 > 75% <= 85% 155.8 6.4 91.4 3.8 > 85% 86.6 3.6 37.5 1.6 Total $ 2,432.1 100.0 % $ 2,397.0 100.0 % The following table presents the amortized cost of our mortgage loans by year of origination and credit quality indicators at December 31, 2020: Prior to 2016 2016 2017 2018 2019 2020 Total (in millions of dollars) Internal Rating AA $ 3.5 $ — $ — $ — $ — $ — $ 3.5 A 240.3 119.5 56.3 60.2 16.9 18.0 511.2 BBB 482.6 287.8 253.9 331.8 351.9 166.4 1,874.4 BB 29.4 — 10.5 — — — 39.9 B 16.2 — — — — — 16.2 Total Amortized Cost 772.0 407.3 320.7 392.0 368.8 184.4 2,445.2 Allowance for credit losses (2.4) (2.0) (1.9) (2.4) (2.9) (1.5) (13.1) Carrying Amount $ 769.6 $ 405.3 $ 318.8 $ 389.6 $ 365.9 $ 182.9 $ 2,432.1 Loan-to-Value Ratio <=65% $ 598.5 $ 257.5 $ 139.0 $ 77.8 $ 82.8 $ 37.2 $ 1,192.8 >65<=75% 47.2 122.5 109.9 294.8 286.0 147.2 1,007.6 >75%<=85% 78.7 27.3 37.9 13.3 — — 157.2 >85% 47.6 — 33.9 6.1 — — 87.6 Total Amortized Cost 772.0 407.3 320.7 392.0 368.8 184.4 2,445.2 Allowance for credit losses (2.4) (2.0) (1.9) (2.4) (2.9) (1.5) (13.1) Carrying Amount $ 769.6 $ 405.3 $ 318.8 $ 389.6 $ 365.9 $ 182.9 $ 2,432.1 The following table presents a rollforward of allowance for expected credit losses by loan-to-value ratio: Year Ended December 31, 2020 Beginning of Period Current Period Provisions Write-Offs Recoveries End of Period (in millions of dollars) Loan-to-Value Ratio <=65% $ 2.8 $ 0.6 $ — $ — $ 3.4 >65<=75% 4.6 2.7 — — 7.3 >75%<=85% 0.5 0.8 — — 1.3 >85% 0.4 0.7 — — 1.1 Total $ 8.3 $ 4.8 $ — $ — $ 13.1 The increase in our estimate of expected losses during the year ended December 31, 2020 is primarily due to the expected impact of COVID-19, specifically impacts to underlying commercial real estate values, and reflects market conditions at December 31, 2020. There were no troubled debt restructurings during 2020 or 2019. We had one mortgage loan which was modified in a troubled debt restructuring during the second quarter of 2018. The loan had a principal balance of $3.6 million prior to the restructuring, wherein the terms of the loan were modified to reduce monthly payments to interest-only at the current note rate and to permit a discounted payoff by September 2018. At time of restructuring, we recorded an allowance for credit losses on mortgage loans and recognized an impairment loss of $0.2 million in the second quarter of 2018. The payoff of the loan did not occur in September 2018 and the loan was considered impaired as of December 31, 2018. The loan was settled during the first quarter of 2019 resulting in an additional loss of $0.1 million. At 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 years ended December 31, 2020, 2019, or 2018. For the year ended December 31, 2020, we had no impaired mortgage loans. Our average investment in impaired mortgage loans was $0.6 million, and $2.3 million for the years ended December 31, 2019 and 2018, respectively. We did not recognize any interest income during 2020, 2019 or 2018 on mortgage loans subsequent to impairment. At December 31, 2020, we had commitments of $11.4 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 December 31, 2020, we had $0.1 million of expected credit losses related to unfunded commitments on our consolidated balance sheets. Investment Real Estate Our investment real estate balance was $106.3 million and $90.5 million at December 31, 2020 and 2019, respectively, and the associated accumulated depreciation was $97.7 million and $49.8 million at December 31, 2020 and 2019, respectively. For the year ended December 31, 2020, we recognized $36.6 million in impairments related to certain of our real estate held for investment. We did not recognize any impairments on investment real estate during 2019 and we recognized $0.6 million in impairments in 2018. 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 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. As of December 31, 2019, the carrying amount of fixed maturity securities loaned to third parties under our securities lending program was $176.4 million, for which we received collateral in the form of securities of $186.5 million. We had no outstanding repurchase agreements at December 31, 2020 or 2019. The remaining contractual maturities of our securities lending agreements disaggregated by class of collateral pledged are as follows: December 31 2020 2019 Overnight and Continuous (in millions of dollars) Borrowings United States Government and Government Agencies and Authorities $ 0.1 $ — State, Municipalities, and Political Subdivisions 0.4 — Public Utilities 0.3 — All Other Corporate Bonds 16.8 — Total Borrowings $ 17.6 $ — Gross Amount of Recognized Liability for Securities Lending Transactions 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 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: December 31 2020 2019 (in millions of dollars) Carrying Value of FHLB Common Stock $ 28.2 $ 18.5 Advances from FHLB 312.2 — Carrying Value of Collateral Posted to FHLB Fixed Maturity Securities $ 944.0 $ 182.1 Commercial Mortgage Loans 1,072.5 164.4 Total Carrying Value of Collateral Posted to FHLB $ 2,016.5 $ 346.5 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 4 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. 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 December 31, 2019 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 $ 27.5 $ — $ 27.5 $ (4.0) $ (23.5) $ — Securities Lending 176.4 — 176.4 (176.4) — — Total $ 203.9 $ — $ 203.9 $ (180.4) $ (23.5) $ — Financial Liabilities: Derivatives $ 34.6 $ — $ 34.6 $ (31.3) $ — $ 3.3 Net Investment Income Net investment income reported in our consolidated statements of income is presented below. Certain prior period amounts have been reclassified to conform to the current period presentation. Year Ended December 31 2020 2019 2018 (in millions of dollars) Fixed Maturity Securities $ 2,164.0 $ 2,213.6 $ 2,239.7 Derivatives 78.7 73.4 66.1 Mortgage Loans 108.9 103.3 110.1 Policy Loans 20.0 19.9 18.6 Other Long-term Investments Perpetual Preferred Securities 1 (2.1) 5.4 (0.2) Private Equity Partnerships 2 19.8 31.7 36.0 Other 3.9 3.9 8.4 Short-term Investments 10.5 29.0 23.7 Gross Investment Income 2,403.7 2,480.2 2,502.4 Less Investment Expenses 30.6 32.1 35.2 Less Investment Income on Participation Fund Account Assets 12.4 12.8 13.5 Net Investment Income $ 2,360.7 $ 2,435.3 $ 2,453.7 1 The net unrealized gain (loss) recognized in net investment income for the year ended December 31, 2020 related to perpetual preferred securities still held at December 31, 2020 was $(4.6) million. The net unrealized gain (loss) recognized in net investment income for the year ended December 31, 2019 related to perpetual preferred securities still held at December 31, 2019 was $3.3 million. 2 The net unrealized gain (loss) recognized in net investment income for the year ended December 31, 2020 related to private equity partnerships still held at December 31, 2020 was $(8.7) million. The net unrealized gain (loss) recognized in net investment income for the year ended December 31, 2019 related to private equity partnerships still held at December 31, 2019 was $6.8 million. See Note 2 for further discussion of private equity partnerships. Realized Investment Gain and Loss Realized investment gains and losses are as follows: Year Ended December 31 2020 2019 2018 (in millions of dollars) Fixed Maturity Securities Gross Gains on Sales 1 $ 1,332.8 $ 22.9 $ 9.7 Gross Losses on Sales (20.3) (32.6) (15.2) Credit Losses (53.6) (25.3) (17.5) Mortgage Loans and Other Invested Assets Gross Gains on Sales 1.9 4.6 0.5 Gross Losses on Sales (0.3) (0.3) — Impairment Loss (36.6) — (1.4) Credit Losses (4.6) — — Embedded Derivative in Modified Coinsurance Arrangement (17.0) 8.3 (15.2) All Other Derivatives (2.5) (0.1) 0.3 Foreign Currency Transactions (0.7) (0.7) (0.7) Net Realized Investment Gain (Loss) $ 1,199.1 $ (23.2) $ (39.5) 1 Gross gains on sales of fixed maturity securities includes gains of $1,302.3 million as a result of the reinsurance transaction that we entered into during the fourth quarter of 2020. See Note 12 for further discussion.

Derivative Financial Instrument

Derivative Financial Instruments	12 Months Ended
	Dec. 31, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
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 used to reduce our exposure to interest rate and duration risk are as follows: • Interest rate swaps are used to effectively convert certain of our fixed rate securities into floating rate securities which are used to fund our floating rate long-term debt. Under these swap agreements, we receive a variable rate of interest and pay a fixed rate of interest. Additionally, we use interest rate swaps to effectively convert certain fixed rate, long-term debt into floating rate long-term debt. Under these swap agreements, we receive a fixed rate of interest and pay 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 and credit losses on securities owned 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. 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. At December 31, 2020, we had $0.7 million credit exposure on derivatives. At December 31, 2019, we had no credit exposure on derivatives. The table below summarizes the nature and amount of collateral received from and posted to our derivative counterparties. December 31 2020 2019 (in millions of dollars) Carrying Value of Collateral Received from Counterparties Cash $ 8.7 $ 24.0 Carrying Value of Collateral Posted to Counterparties Fixed Maturity Securities $ 54.0 $ 28.6 See Note 3 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 $59.7 million and $34.6 million at December 31, 2020 and 2019, 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 Receive Credit Default Forwards Total (in millions of dollars) Balance at December 31, 2017 $ 48.0 $ 536.5 $ 250.0 $ 70.0 $ — $ 904.5 Additions — 78.1 — 11.0 47.4 136.5 Terminations 48.0 76.4 — 70.0 47.4 241.8 Balance at December 31, 2018 — 538.2 250.0 11.0 — 799.2 Additions — 171.3 — — 382.4 553.7 Terminations — 98.4 — — 373.1 471.5 Foreign Currency — — — 0.4 (0.4) — Balance at December 31, 2019 — 611.1 250.0 11.4 8.9 881.4 Additions — 113.6 — — 6.4 120.0 Terminations — 3.9 250.0 — 3.4 257.3 Foreign Currency — — — 0.3 — 0.3 Balance at December 31, 2020 $ — $ 720.8 $ — $ 11.7 $ 11.9 $ 744.4 Cash Flow Hedges As of December 31, 2020 and 2019, we had $210.2 million and $213.5 million, respectively, 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 fourth quarter of 2020, in connection with the Closed Block individual disability reinsurance transaction, we reclassified $30.7 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. During the third quarter of 2019, we entered into a $350.0 million notional forward benchmark interest rate lock in order to hedge the interest rate risk associated with the cash flows related to the tender offer and early redemption of certain of our debt securities. We terminated the interest rate lock during 2019 and recognized a loss of $0.5 million that was reported with the $5.3 million tender premium as a cost related to the early retirement of debt in our statement of income. See Note 8 for further discussion of the tender offer and early redemption of certain of our debt securities. As of December 31, 2020, we expect to amortize approximately $60.3 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 are not estimable. As of December 31, 2020, we are hedging the variability of future cash flows associated with forecasted transactions through the year 2045. Fair Value Hedges As of December 31, 2020 and 2019, we had $362.4 million and $249.4 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 liabilities and the related cumulative basis adjustments related to our fair value hedges: Carrying Amount of Hedged Assets (Liabilities) Cumulative Amount of Fair Value Hedging Adjustment Included in the Carrying Amount of the Hedged Assets (Liabilities) December 31, 2020 December 31, 2019 December 31, 2020 December 31, 2019 (in millions of dollars) Fixed maturity securities: Receive fixed functional currency interest, pay fixed foreign currency interest $ 404.5 $ 239.4 $ 24.4 $ 1.1 Long-term Debt $ — $ (249.2) $ — $ 0.6 For the years ended December 31, 2020, 2019, and 2018, $(1.8) million, $2.0 million, and $2.5 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 December 31, 2020 and 2019, 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 December 31, 2020 and 2019, we held $11.7 million and $11.4 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 December 31, 2020 and 2019, we held $11.9 million and $8.9 million, respectively, notional amount of foreign currency forwards to mitigate the foreign currency risk associated with specific securities owned. 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. 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 December 31, 2019 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 $ 19.4 Other Liabilities $ 6.6 Fair Value Hedges Interest Rate Swaps Other L-T Investments — Other Liabilities 0.6 Foreign Exchange Contracts Other L-T Investments 7.6 Other Liabilities 5.0 Total Fair Value Hedges 7.6 5.6 Total Designated as Hedging Instruments $ 27.0 $ 12.2 Not Designated as Hedging Instruments Credit Default Swaps Other L-T Investments $ 0.5 Other Liabilities $ — Foreign Exchange Contracts Other L-T Investments — Other Liabilities 22.4 Embedded Derivative in Modified Coinsurance Arrangement Other L-T Investments — Other Liabilities 22.8 Total Not Designated as Hedging Instruments $ 0.5 $ 45.2 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. Year Ended December 31, 2020 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 $ 2,360.7 $ 1,199.1 $ 188.2 Gain (Loss) on Cash Flow Hedging Relationships Interest Rate Swaps: Hedged items 286.1 397.7 29.2 Derivatives Designated as Hedging Instruments 75.9 32.0 1.7 Foreign Exchange Contracts: Hedged items 12.1 (0.1) — Derivatives Designated as Hedging Instruments 2.5 0.1 — Gain (Loss) on Fair Value Hedging Relationships Interest Rate Swaps: Hedged items — (0.6) 10.1 Derivatives Designated as Hedging Instruments — 0.6 (0.9) Foreign Exchange Contracts Hedged items 7.1 23.3 — Derivatives Designated as Hedging Instruments 2.8 (23.3) — Year Ended December 31, 2019 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 $ 2,435.3 $ (23.2) $ 177.4 Gain (Loss) on Cash Flow Hedging Relationships Interest Rate Swaps: Hedged items 294.6 (1.6) 30.4 Derivatives Designated as Hedging Instruments 74.3 9.3 2.4 Foreign Exchange Contracts: Hedged items 14.8 1.4 — Derivatives Designated as Hedging Instruments (2.0) (1.4) — Gain (Loss) on Fair Value Hedging Relationships Interest Rate Swaps: Hedged items — (4.5) 14.3 Derivatives Designated as Hedging Instruments — 4.5 2.5 Foreign Exchange Contracts Hedged items 2.9 3.8 — Derivatives Designated as Hedging Instruments 1.9 (3.8) — Year Ended December 31, 2018 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 $ 2,453.7 $ (39.5) $ 167.3 Gain (Loss) on Cash Flow Hedging Relationships Interest Rate Swaps: Hedged items 310.3 0.1 38.4 Derivatives Designated as Hedging Instruments 67.1 (0.3) 2.3 Foreign Exchange Contracts: Hedged items 18.1 1.5 — Derivatives Designated as Hedging Instruments (0.9) (1.5) — Gain (Loss) on Fair Value Hedging Relationships Interest Rate Swaps: Hedged items 1.0 0.1 14.3 Derivatives Designated as Hedging Instruments (0.5) (0.1) 1.8 Foreign Exchange Contracts Hedged items 0.6 (2.7) — Derivatives Designated as Hedging Instruments 0.5 2.7 — 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). Year Ended December 31 2020 2019 2018 (in millions of dollars) Gain (Loss) Recognized in Other Comprehensive Income (Loss) on Derivatives Interest Rate Swaps and Forwards $ — $ (0.1) $ (0.1) Foreign Exchange Contracts (5.4) (6.1) 16.9 Total $ (5.4) $ (6.2) $ 16.8 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. Year Ended December 31 2020 2019 2018 (in millions of dollars) Net Realized Investment Gain (Loss) Credit Default Swaps $ (0.5) $ (0.1) $ (0.3) Interest Rate Swaps — — (0.3) Foreign Exchange Contracts (2.0) — 0.9 Embedded Derivative in Modified Coinsurance Arrangement (17.0) 8.3 (15.2) Total $ (19.5) $ 8.2 $ (14.9)

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	12 Months Ended
	Dec. 31, 2020
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 (Loss) on Securities Net Gain on Hedges Foreign Currency Translation Adjustment Unrecognized Pension and Postretirement Benefit Costs Total (in millions of dollars) Balances at December 31, 2017 $ 607.8 $ 282.3 $ (254.5) $ (508.1) $ 127.5 Adjustment to Adopt Accounting Standard Update - Note 1 (17.5) — — — (17.5) Other Comprehensive Income (Loss) Before Reclassifications (920.3) 16.8 (50.7) 43.6 (910.6) Amounts Reclassified from Accumulated Other Comprehensive Income or Loss 17.6 (48.5) — 17.3 (13.6) Net Other Comprehensive Income (Loss) (902.7) (31.7) (50.7) 60.9 (924.2) Balances at December 31, 2018 (312.4) 250.6 (305.2) (447.2) (814.2) Other Comprehensive Income (Loss) Before Reclassifications 894.1 (0.2) 23.6 (52.0) 865.5 Amounts Reclassified from Accumulated Other Comprehensive Income or Loss 34.2 (62.6) — 14.4 (14.0) Net Other Comprehensive Income (Loss) 928.3 (62.8) 23.6 (37.6) 851.5 Balances at December 31, 2019 615.9 187.8 (281.6) (484.8) 37.3 Other Comprehensive Income (Loss) Before Reclassifications 405.6 (5.7) 20.3 (60.8) 359.4 Amounts Reclassified from Accumulated Other Comprehensive Income or Loss 46.2 (84.3) — 15.6 (22.5) Net Other Comprehensive Income (Loss) 451.8 (90.0) 20.3 (45.2) 336.9 Balances at December 31, 2020 $ 1,067.7 $ 97.8 $ (261.3) $ (530.0) $ 374.2 The net unrealized gain (loss) on securities consists of the following components: December 31 January 1 December 31 Change for the Year Ended December 31 2020 2019 2018 2018 2017 2020 2019 2018 (in millions of dollars) Fixed Maturity Securities $ 7,597.6 $ 6,364.4 $ 2,736.5 $ 5,665.2 $ 5,677.3 $ 1,233.2 $ 3,627.9 $ (2,928.7) Other Investments — — — — 14.4 — — — Deferred Acquisition Costs (85.1) (62.7) (27.9) (51.4) (51.4) (22.4) (34.8) 23.5 Reserves for Future Policy and Contract Benefits (6,225.6) (5,803.1) (3,220.3) (5,094.7) (5,094.7) (422.5) (2,582.8) 1,874.4 Reinsurance Recoverable 200.2 424.7 261.4 375.8 375.8 (224.5) 163.3 (114.4) Income Tax (419.4) (307.4) (62.1) (304.6) (313.6) (112.0) (245.3) 242.5 Total $ 1,067.7 $ 615.9 $ (312.4) $ 590.3 $ 607.8 $ 451.8 $ 928.3 $ (902.7) Amounts reclassified from accumulated other comprehensive income (loss) were recognized in our consolidated statements of income as follows: Year Ended December 31 2020 2019 2018 (in millions of dollars) Net Unrealized Gain (Loss) on Securities Net Realized Investment Gain (Loss) Gain (Loss) on Sales on Securities $ 1,279.7 $ (18.0) $ (4.8) Credit Losses on Fixed Maturity Securities (53.6) (25.3) (17.5) Loss on Benefits and Change in Reserves for Future Benefits (1,284.5) — — (58.4) (43.3) (22.3) Income Tax Benefit (12.2) (9.1) (4.7) Total $ (46.2) $ (34.2) $ (17.6) Net Gain on Hedges Net Investment Income Gain on Interest Rate Swaps and Forwards $ 74.1 $ 73.6 $ 65.9 Gain (Loss) on Foreign Exchange Contracts 2.0 0.8 (1.1) Net Realized Investment Gain (Loss) Gain on Interest Rate Swaps 32.0 8.8 0.2 Gain (Loss) on Foreign Exchange Contracts 0.1 (1.3) (1.5) Interest and Debt Expense Loss on Interest Rate Swaps (1.5) (2.1) (2.1) Loss on Forward — (0.5) — 106.7 79.3 61.4 Income Tax Expense 22.4 16.7 12.9 Total $ 84.3 $ 62.6 $ 48.5 Unrecognized Pension and Postretirement Benefit Costs Other Expenses Amortization of Net Actuarial Loss $ (19.8) $ (18.6) $ (22.3) Amortization of Prior Service Credit 0.1 0.2 0.2 Curtailment Gain (0.1) — — (19.8) (18.4) (22.1) Income Tax Benefit (4.2) (4.0) (4.8) Total $ (15.6) $ (14.4) $ (17.3)

Liability for Unpaid Claims and

Liability for Unpaid Claims and Claim Adjustment Expenses	12 Months Ended
	Dec. 31, 2020
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: 2020 2019 2018 (in millions of dollars) Balance at January 1 $ 23,076.7 $ 23,149.0 $ 23,222.0 Less Reinsurance Recoverable 2,246.8 2,227.3 2,182.0 Net Balance at January 1 20,829.9 20,921.7 21,040.0 Incurred Related to Current Year 6,327.8 6,113.2 5,832.3 Prior Years Interest 997.8 1,036.5 1,049.8 All Other Incurred 878.7 (274.1) (106.2) Foreign Currency 65.9 76.0 (110.7) Total Incurred 8,270.2 6,951.6 6,665.2 Paid Related to Current Year (2,727.0) (2,532.4) (2,354.7) Prior Years (4,430.3) (4,511.0) (4,428.8) Total Paid (7,157.3) (7,043.4) (6,783.5) Reserves Ceded Pursuant to Reinsurance Transaction (6,141.5) — — Net Balance at December 31 15,801.3 20,829.9 20,921.7 Plus Reinsurance Recoverable 8,378.9 2,246.8 2,227.3 Balance at December 31 $ 24,180.2 $ 23,076.7 $ 23,149.0 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 year’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 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 Closed Block individual disability reinsurance agreement and reserve adjustments as discussed in the following paragraphs, which impact the comparability between the years presented. Excluding those adjustments, 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. Closed Block Individual Disability Reinsurance Transaction In connection with the first phase of the Closed Block individual disability coinsurance agreement that closed in December 2020, we recorded a reinsurance recoverable of $6,141.5 million representing the ceded reserves related to the cohort of policies on claim status as of July 1, 2020 (DLR cohort) and an increase in benefits and change in reserves for future benefits of $1,284.5 million resulting from the realization of previously unrealized investment gains and losses recorded in accumulated other comprehensive income. These impacts are reflected in the chart shown above and the reconciliation shown below. 2020 Long-term Care Reserve Increase During the fourth quarter of 2020, we completed a review of policy reserve adequacy, which incorporated our most recent experience and included a review of all material assumptions. Based on our analysis, during the fourth quarter of 2020, we updated our interest rate and premium rate increase reserve assumptions and determined that our gross long-term care policy and claim reserves should be increased by $151.5 million, of which $7.0 million was related to our liability for unpaid claims and claims adjustment expenses, which can be primarily attributed to prior year incurred claims, thereby impacting the results shown in the preceding chart. 2018 Long-term Care Reserve Increase During the third quarter of 2018, we completed our annual review of policy reserve adequacy, which incorporated our most recent experience and included a review of all assumptions. Based on our analysis, during the third quarter of 2018, we updated our reserve assumptions and determined that our policy and claim reserves should be increased by $750.8 million of which, approximately $236 million was related to our liability for unpaid claims and claims adjustment expenses, which can be primarily attributed to prior year incurred claims, thereby impacting the results shown in the preceding chart. 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: December 31 2020 2019 2018 (in millions of dollars) Policy and Contract Benefits $ 1,855.4 $ 1,745.5 $ 1,695.7 Reserves for Future Policy and Contract Benefits 49,653.0 47,780.1 44,841.9 Total 51,508.4 49,525.6 46,537.6 Less: Life Reserves for Future Policy and Contract Benefits 8,371.7 8,435.7 8,330.9 Accident and Health Active Life Reserves 12,730.9 12,210.1 11,837.4 Adjustment Related to Unrealized Investment Gains and Losses 6,225.6 5,803.1 3,220.3 Liability for Unpaid Claims and Claim Adjustment Expenses $ 24,180.2 $ 23,076.7 $ 23,149.0

Income Tax

Income Tax	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Income Tax Disclosure	Total income tax expense (benefit) is allocated as follows: Year Ended December 31 2020 2019 2018 (in millions of dollars) Net Income $ 171.0 $ 281.8 $ 104.4 Stockholders' Equity - Accumulated Other Comprehensive Income (Loss) Change in Net Unrealized Gain on Securities Before Adjustment 250.2 757.0 (614.2) Change in Adjustment to Deferred Acquisition Costs and Reserves for Future Policy and Contract Benefits, Net of Reinsurance (138.2) (511.7) 371.7 Change in Net Gain on Hedges (23.8) (17.0) (8.2) Change in Foreign Currency Translation Adjustment (4.3) 0.2 (0.6) Change in Unrecognized Pension and Postretirement Benefit Costs (34.8) (9.3) 17.0 Total $ 220.1 $ 501.0 $ (129.9) A reconciliation of the income tax provision at the U.S. federal statutory rate to the income tax rate as reported in our consolidated statements of income is as follows: Year Ended December 31 2020 2019 2018 Statutory Income Tax 21.0 % 21.0 % 21.0 % Net Operating Loss Carryback (3.8) — — Deemed Repatriation Tax on Foreign Earnings and Profit — — 1.8 Tax Exempt Income (0.8) (0.5) (1.3) Tax Credits (1.3) (1.1) (2.4) Policyholder Reserves 0.7 — (2.4) Other Items, Net 1.9 1.0 (0.1) Effective Tax 17.7 % 20.4 % 16.6 % Our net deferred tax asset (liability) consists of the following. Certain prior year amounts have been reclassified to conform to current year reporting. December 31 2020 2019 (in millions of dollars) Deferred Tax Asset Reserves $ 1,279.6 $ 1,154.6 Employee Benefits 218.7 201.6 Other 52.9 19.4 Gross Deferred Tax Asset 1,551.2 1,375.6 Less: Valuation Allowance 14.5 28.3 Net Deferred Tax Asset 1,536.7 1,347.3 Deferred Tax Liability Deferred Acquisition Costs 185.5 115.6 Fixed Assets 74.7 58.5 Invested Assets 1,443.5 1,213.7 Cost of Reinsurance 180.4 10.8 Other 68.7 44.1 Gross Deferred Tax Liability 1,952.8 1,442.7 Net Deferred Tax Asset (Liability) $ (416.1) $ (95.4) Our consolidated statements of income include amounts subject to both domestic and foreign taxation. The income and related tax expense (benefit) are as follows: Year Ended December 31 2020 2019 2018 (in millions of dollars) Income Before Tax Domestic $ 924.7 $ 1,289.5 $ 492.6 Foreign 39.3 92.6 135.2 Total $ 964.0 $ 1,382.1 $ 627.8 Current Tax Expense (Benefit) Federal $ (98.4) $ 273.6 $ 194.6 State and Local 1.5 1.3 (0.6) Foreign (19.7) (0.1) 33.4 Total (116.6) 274.8 227.4 Deferred Tax Expense (Benefit) Federal 250.5 (9.5) (114.6) State and Local 1.0 (0.1) (0.2) Foreign 36.1 16.6 (8.2) Total 287.6 7.0 (123.0) Total Tax Expense $ 171.0 $ 281.8 $ 104.4 On December 22, 2017, the U.S. Federal government enacted the TCJA, which reduced the federal corporate tax rate from 35 percent to 21 percent effective January 1, 2018. The Securities and Exchange Commission issued Staff Accounting Bulletin No. 118 (SAB 118) allowing a one-year measurement period after the enactment date of TCJA to finalize the calculation and record the related tax impacts. We finalized and recorded adjustments to our initial estimates during 2018. As a result of guidance from the Internal Revenue Service (IRS), we recorded additional deemed repatriation transition tax on accumulated foreign E&P of $11.5 million, for a total of $77.9 million. We recorded no other material changes to our calculations of the impact of the TCJA during the one-year measurement period after the enactment period as allowed by SAB 118. In 2020, we recorded a tax benefit of $36.5 million for 2020 tax losses that will be carried back to a 35 percent tax year pursuant to the Coronavirus Aid, Relief, and Economic Security Act (CARES Act). On July 22, 2020, the Finance Bill 2019-21 was enacted, resulting in a U.K. tax rate increase from 17 percent to 19 percent, retroactively effective April 1, 2020, which resulted in tax expense of $9.3 million for the revaluation of our tax assets and liabilities, primarily deferred tax liabilities related to policyholder reserves. As of December 31, 2020, our plans for the future repatriations of cash from our foreign subsidiaries can include no more than the amount of capital above that which is required by U.K. regulatory capital requirements. The remainder of our investment in our foreign subsidiaries is indefinitely reinvested and we have not recorded any deferred taxes on the approximately $0.7 billion of the excess of the U.S. GAAP carrying values over the tax basis of investments in our foreign subsidiaries. Our consolidated statements of income include the following changes in unrecognized tax benefits. December 31 2020 2019 2018 (in millions of dollars) Balance at Beginning of Year $ 241.0 $ 262.2 $ 1.4 Increases (Decreases) for Tax Positions Related to Prior Years (21.0) (21.1) 261.5 Lapse of the Applicable Statute of Limitations (0.3) (0.1) (0.7) Balance at End of Year 219.7 241.0 262.2 Less Tax Attributable to Temporary Items Included Above (105.9) (127.1) (148.2) Total Unrecognized Tax Benefits That if Recognized Would Affect the Effective Tax Rate $ 113.8 $ 113.9 $ 114.0 In 2018, we recorded $261.1 million gross unrecognized tax benefits for a policyholder reserves position taken on our 2017 federal tax return, which if recognized, would decrease our tax expense by $112.9 million. The balances of unrecognized tax benefits for which the ultimate deductibility is highly certain but for which there is uncertainty about the timing of such deductibility are $105.9 million at December 31, 2020, $127.1 million at December 31, 2019, and $148.2 million at December 31, 2018. It is reasonably possible that this item could reverse in the next 12 months following review by the IRS. We recognize interest expense and penalties, if applicable, related to unrecognized tax benefits in tax expense. We recognized $7.8 million and $12.8 million of interest expense related to unrecognized tax benefits during 2020 and 2019, respectively, and a de minimis amount in 2018. The liability for net interest expense on uncertain tax positions was approximately $20.6 million and $12.8 million as of December 31, 2020 and 2019, respectively, and a de minimis amount in 2018. We file federal and state income tax returns in the United States and in foreign jurisdictions. Tax years subsequent to 2014 remain subject to examination by the IRS. Tax years subsequent to 2016 remain subject to examination by the IRS for the subsidiaries not included in the consolidated tax return. All other major foreign jurisdictions remain subject to examination for tax years subsequent to 2018 with the exception of Poland for which tax years subsequent to 2014 remain subject to examination. We believe sufficient provision has been made for all potential adjustments for years that are not closed by the statute of limitations in all major tax jurisdictions and that any such adjustments would not have a material adverse effect on our financial position, liquidity, or results of operations. We file state income tax returns in nearly every state in the United States. Tax years subsequent to 2015 remain subject to examination depending on the statute of limitation established by the various states, which is generally three to four years. We have no accumulated federal net operating loss carryforwards as of December 31, 2020. Our federal capital loss carryforward, related to subsidiaries not included in the consolidated U.S. federal return, was $0.6 million at December 31, 2020 and is expected to be utilized by the time it expires in 2022. We have net operating loss carryforwards for state and local income tax of approximately $191 million, most of which is expected to expire unused between 2021 and 2040. We record valuation allowances to reduce deferred tax assets to the amount that is more likely than not to be realized. Our valuation allowance was $14.5 million and $28.3 million at December 31, 2020 and 2019, the majority of which related to our cumulative deferred state income tax benefits. The de minimis remaining amount of our valuation allowance relates to unrealized tax losses on buildings which we own and occupy in the U.K. We recorded a decrease in our valuation allowance of $13.8 million during 2020 and an increase of $9.9 million in 2019, primarily in other comprehensive income. Total income taxes paid net of refunds during 2020, 2019, and 2018 were $200.0 million, $35.1 million, and $139.7 million, respectively.

Debt

Debt	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Debt	Debt consists of the following: December 31 2020 2019 Interest Rates Maturities (in millions of dollars) Long-term Debt Outstanding Principal Senior Secured Notes issued 2007 Variable 2037 $ — $ 80.0 Senior Notes issued 1998 6.750 - 7.250% 2028 335.8 335.8 Senior Notes issued 2002 7.375% 2032 39.5 39.5 Senior Notes issued 2012 and 2016 5.750% 2042 500.0 500.0 Senior Notes issued 2014 4.000% 2024 350.0 350.0 Senior Notes issued 2015 3.875% 2025 275.0 275.0 Senior Notes issued 2019 4.000% 2029 400.0 400.0 Senior Notes issued 2019 4.500% 2049 450.0 450.0 Senior Notes issued 2020 4.500% 2025 500.0 — Medium-term Notes issued 1990 - 1996 7.000 - 7.190% 2023 - 2028 20.5 20.5 Junior Subordinated Debt Securities issued 1998 7.405% 2038 203.7 203.7 Junior Subordinated Debt Securities issued 2018 6.250% 2058 300.0 300.0 Fair Value Hedge Adjustment — (0.6) Less: Unamortized Net Premium 6.0 8.4 Unamortized Debt Issuance Costs (34.8) (35.4) Total Long-term Debt 3,345.7 2,926.9 Short-term Debt Outstanding Principal Senior Notes issued 2010 5.625% 2020 — 400.0 Less Unamortized Debt Issuance Costs — (0.3) Total Short-term Debt — 399.7 Total Debt $ 3,345.7 $ 3,326.6 Collateralized debt is comprised of our senior secured notes and ranks highest in priority, followed by unsecured notes, which consist of senior notes and medium-term notes, followed by junior subordinated debt securities. The medium-term notes are non-callable and the junior subordinated debt securities are callable under limited, specified circumstances. The remaining debt is callable and may be redeemed, in whole or in part, at any time. The aggregate contractual principal maturities are $2.0 million in 2023, $350.0 million in 2024, $775.0 million in 2025, and $2,247.5 million thereafter. Senior Secured Notes In 2007, Northwind Holdings, LLC (Northwind Holdings), a wholly-owned subsidiary of Unum Group, issued $800.0 million of insured, senior secured notes, bearing interest at a floating rate equal to the three month LIBOR plus 0.78% (the Northwind notes) in a private offering. Northwind Holdings made periodic principal payments on the Northwind notes of $45.0 million in 2020 and $60.0 million in both 2019 and 2018. In December 2020, Northwind Holdings redeemed the remaining $35.0 million of principal on the Northwind notes, and was released of any contractual collateral requirements. Unsecured Notes In September 2020, our $400.0 million 5.625% senior unsecured notes matured. In May 2020, we issued $500.0 million of 4.500% senior notes due 2025. The notes are callable at or above par and rank equally in the right of payment with all of our other unsecured and unsubordinated debt. During 2019 we purchased and retired (i) $30.3 million aggregate principal amount of our 7.190% medium-term notes due 2028; (ii) $30.0 million aggregate principal amount of our 7.250% senior notes due 2028; and (iii) $350.0 million aggregate principal amount of our 3.000% senior notes due 2021. In September 2019, we issued $450.0 million of 4.500% senior notes due 2049. The notes are callable at or above par and rank equally in the right of payment with all of our other unsecured and unsubordinated debt. In June 2019, we issued $400.0 million of 4.000% senior notes due 2029. The notes are callable at or above par and rank equally in the right of payment with all of our other unsecured and unsubordinated debt. In July 2018, our $200.0 million 7.000% senior unsecured notes matured. Fair Value Hedges As of December 31, 2019, we had $250.0 million notional amount of an interest rate swap which effectively converted certain of our unsecured senior notes into floating rate debt. Under this agreement, we received a fixed rate of interest and paid a variable rate of interest, based off of three-month LIBOR. During 2020, the $250.0 million notional amount of the interest rate swap matured in conjunction with the maturity of the hedged debt. See Note 4 for further information on the interest rate swap. Junior Subordinated Debt Securities In May 2018, we issued $300.0 million of 6.250% junior subordinated notes due 2058. The notes are redeemable at or above par on or after June 15, 2023 and rank equally in the right of payment with our other junior subordinated debt securities. In 1998, Provident Financing Trust I (the Trust), a 100 percent-owned finance subsidiary of Unum Group, issued $300.0 million of 7.405% capital securities due 2038 in a public offering. These capital securities are fully and unconditionally guaranteed by Unum Group, have a liquidation value of $1,000 per capital security, and have a mandatory redemption feature under certain circumstances. In connection with the capital securities offering, Unum Group issued to the Trust 7.405% junior subordinated deferrable interest debentures due 2038. The Trust is a variable interest entity of which Unum Group is not the primary beneficiary. Accordingly, the capital securities issued by the Trust are not included in our consolidated financial statements and our liability represents the junior subordinated debt securities owed to the trust which is recorded in long-term debt. The sole assets of the Trust are the junior subordinated debt securities. The retirement of any liquidation amount regarding the capital securities by the Trust results in a corresponding retirement of principal amount of the junior subordinated debt securities. During 2019, the Trust purchased and retired $22.8 million aggregate liquidation amount of the 7.405% capital securities due 2038, which resulted in our purchase and retirement of a corresponding principal amount of our 7.405% junior subordinated debt securities due 2038. Cost Related to Early Retirement of Debt During 2019, we incurred costs of $27.3 million related to the early retirement of certain of our unsecured notes and junior subordinated debt securities as previously discussed. Interest Paid Interest paid on long-term and short-term debt and related securities during 2020, 2019, and 2018 was $178.1 million, $172.9 million, and $167.3 million, respectively. Credit Facilities We have access to two separate unsecured revolving credit facilities, each with a different syndicate of lenders. One of our credit facilities is under a five-year agreement and is effective through April 2024. The terms of this agreement provide for a borrowing capacity of $500.0 million with an option to be increased up to $700.0 million. We may also request, on up to two occasions, that the lenders' commitment termination dates be extended by one year. The credit facility provides for the issuance of letters of credit subject to certain terms and limitations. At December 31, 2020, letters of credit totaling $0.6 million had been issued from this credit facility, but there were no borrowed amounts outstanding. Our other credit facility is under a three-year agreement and is effective until April 2022. The terms of this agreement provide for a borrowing capacity of $100.0 million with an option to be increased up to $140.0 million. We may also request that the lenders' commitment termination dates be extended by one year. The credit facility provides for the issuance of letters of credit subject to certain terms and limitations. At December 31, 2020, there have been no letters of credit issued from the credit facility and there were no borrowed amounts outstanding. Borrowings under the credit facilities are for general corporate uses and are subject to financial covenants, negative covenants, and events of default that are customary. The two primary financial covenants include limitations based on our leverage ratio and consolidated net worth. We are also subject to covenants that limit subsidiary indebtedness. The credit facilities provide for borrowings at an interest rate based either on the prime rate or LIBOR.

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2020
Retirement Benefits [Abstract]
Pension and Other Postretirement Benefits Disclosure	Note 9 - 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. U.S. Pension Plan Annuity Purchases On December 26, 2019, we purchased a group annuity contract which transferred a portion of our U.S. qualified defined benefit pension plan obligation to a third party. Under the transaction, which was funded with plan assets, we transferred the responsibility for pension benefits and annuity administration for approximately 1,900 retirees or their beneficiaries receiving less than $350 in monthly benefit payments from the plan. This transfer resulted in a reduction in our U.S. qualified defined benefit pension plan obligation of $59.5 million at December 31, 2019 and is reflected in the Benefits and Expenses Paid line item within the following table regarding changes in our benefit obligation. On January 2, 2020, in a separate transaction, we purchased a second group annuity contract which transferred an additional portion of our U.S. qualified defined benefit pension plan obligation to the same third party. Under the transaction, which was funded with plan assets, we transferred the responsibility for pension benefits and annuity administration for approximately 600 retirees or their beneficiaries receiving between $350 and $500 in monthly benefit payments from the plan. This transfer resulted in a reduction in our U.S. qualified benefit pension plan obligation of $44.0 million at December 31, 2020 and is reflected in the Benefits and Expenses Paid line item within the following table regarding changes in our benefit obligation. Amortization Period of Actuarial Gain or Loss and Prior Service Cost or Credit Because all participants in the U.S. and U.K. pension plans are considered inactive, we amortize the net actuarial loss and prior service credit for these plans over the average remaining life expectancy of the plans. As of December 31, 2020, the estimate of the average remaining life expectancy of the plans was approximately 25 years for the U.S. plan and 31 years for U.K. plan. The following table provides the changes in the benefit obligation and fair value of plan assets and the funded status of the plans. Pension Benefits U.S. Plans U.K. Plan OPEB 2020 2019 2020 2019 2020 2019 (in millions of dollars) Change in Benefit Obligation Benefit Obligation at Beginning of Year $ 2,106.9 $ 1,933.3 $ 256.9 $ 211.0 $ 127.2 $ 125.9 Service Cost 11.0 10.9 — — — — Interest Cost 73.0 83.3 4.9 6.1 4.1 5.3 Plan Participant Contributions — — — — 0.1 0.2 Actuarial (Gain) Loss (1) 212.4 225.7 33.8 34.9 (0.3) 7.0 Benefits and Expenses Paid (126.1) (146.3) (5.1) (4.8) (10.6) (11.2) Curtailment Gain — — (0.7) — — — Change in Foreign Exchange Rates — — 10.2 9.7 — — Benefit Obligation at End of Year $ 2,277.2 $ 2,106.9 $ 300.0 $ 256.9 $ 120.5 $ 127.2 Accumulated Benefit Obligation at December 31 $ 2,277.2 $ 2,106.9 $ 297.5 $ 253.1 N/A N/A Change in Fair Value of Plan Assets Fair Value of Plan Assets at Beginning of Year $ 1,600.0 $ 1,454.9 $ 252.8 $ 217.0 $ 9.9 $ 10.1 Actual Return on Plan Assets 227.9 282.7 36.4 31.0 0.1 0.2 Employer Contributions 9.1 8.7 — — 9.8 10.6 Plan Participant Contributions — — — — 0.1 0.2 Benefits and Expenses Paid (126.1) (146.3) (5.1) (4.8) (10.6) (11.2) Change in Foreign Exchange Rates — — 10.0 9.6 — — Fair Value of Plan Assets at End of Year $ 1,710.9 $ 1,600.0 $ 294.1 $ 252.8 $ 9.3 $ 9.9 Underfunded Status $ 566.3 $ 506.9 $ 5.9 $ 4.1 $ 111.2 $ 117.3 (1) The actuarial losses recognized for the U.S. and U.K. pension plans were primarily driven by decreases in the discount rate assumption. The amounts recognized in our consolidated balance sheets for our pension and OPEB plans at December 31, 2020 and 2019 are as follows. Pension Benefits U.S. Plans U.K. Plan OPEB 2020 2019 2020 2019 2020 2019 (in millions of dollars) Current Liability $ 8.0 $ 7.7 $ — $ — $ 1.5 $ 1.5 Noncurrent Liability 558.3 499.2 5.9 4.1 109.7 115.8 Noncurrent Asset — — — — — — Underfunded Status $ 566.3 $ 506.9 $ 5.9 $ 4.1 $ 111.2 $ 117.3 Unrecognized Pension and Postretirement Benefit Costs Net Actuarial Gain (Loss) $ (767.9) $ (695.4) $ (70.5) $ (63.1) $ 11.0 $ 11.1 Prior Service Credit (Cost) (0.6) (0.7) (0.2) (0.3) 2.9 3.1 (768.5) (696.1) (70.7) (63.4) 13.9 14.2 Income Tax 273.9 240.7 16.0 14.5 5.4 5.3 Total Included in Accumulated Other Comprehensive Income (Loss) $ (494.6) $ (455.4) $ (54.7) $ (48.9) $ 19.3 $ 19.5 The following table provides the changes recognized in other comprehensive income for the years ended December 31, 2020 and 2019. Pension Benefits U.S. Plans U.K. Plan OPEB 2020 2019 2020 2019 2020 2019 (in millions of dollars) Accumulated Other Comprehensive Income (Loss) at Beginning of Year $ (455.4) $ (437.3) $ (48.9) $ (37.3) $ 19.5 $ 27.4 Net Actuarial Gain (Loss) Amortization 18.7 20.2 1.1 0.9 — (2.5) All Other Changes (91.2) (43.0) (8.5) (15.1) (0.1) (7.3) Prior Service Credit (Cost) Amortization 0.1 — — — (0.2) (0.2) Curtailment Gain — — 0.1 — — — Change in Income Tax 33.2 4.7 1.5 2.6 0.1 2.1 Accumulated Other Comprehensive Income (Loss) at End of Year $ (494.6) $ (455.4) $ (54.7) $ (48.9) $ 19.3 $ 19.5 Plan Assets The objective of our U.S. pension and OPEB plans is to maximize long-term return, within acceptable risk levels, in a manner that is consistent with the fiduciary standards of the Employee Retirement Income Security Act (ERISA), while maintaining sufficient liquidity to pay current benefits and expenses. Our U.S. qualified defined benefit pension plan assets include a diversified blend of domestic, international, global, and emerging market equity securities, fixed income securities, opportunistic credit securities, real estate investments, alternative investments, and cash equivalents. Equity securities are comprised of funds and individual securities that are benchmarked against the respective indices specified below. International and global equity funds may allocate a certain percentage of assets to forward currency contracts. Fixed income securities include U.S. government and agency asset-backed securities, corporate investment-grade bonds, private placement securities, and bonds issued by states or other municipalities. Opportunistic credits consist of investments in funds that hold varied fixed income investments purchased at depressed values with the intention to later sell those investments for a gain. Real estate investments consist primarily of funds that hold commercial real estate investments. Alternative investments, which include private equity direct investments, private equity funds of funds, and hedge funds of funds, utilize proprietary strategies that are intended to have a low correlation to the U.S. stock market. Prohibited investments include, but are not limited to, unlisted securities, options, short sales, and investments in securities issued by Unum Group or its affiliates. The invested asset classes, asset types, and benchmark indices for our U.S. qualified defined benefit pension plan is as follows. We target approximately 36 percent to equity securities, 40 percent to fixed income securities, and 24 percent to opportunistic credits, alternative, and real estate investments. Asset Class Asset Type Benchmark Indices Equity Securities Collective funds; Individual holdings Standard & Poor's 500; Russell 2000 Value and Growth; Morgan Stanley Capital International (MSCI) Europe Australasia Far East Small Cap; MSCI Emerging Markets; MSCI World and World Minimum Volatility; FTSE RAFI All-World Low Volatility Fixed Income Individual holdings Bloomberg Barclays Long Government/Corporate Index Opportunistic Credits Collective fund Custom Index Real Estate Collective fund National Council of Real Estate Investment Fund Open-end Diversified Core Equity Index Alternative Investments (Hedge and Private Equity) Fund of funds; Direct investments Hedge Fund Research Institute Fund of Funds; Custom Index Assets for our U.K. pension plan are primarily invested in a pooled diversified growth fund. This fund invests in assets such as global equities, hedge funds, commodities, below-investment-grade fixed income securities, and currencies. The objectives of the fund are to generate capital appreciation over the course of a complete economic and market cycle and to deliver equity-like returns in the medium-to-long term while maintaining approximately two thirds of the volatility of equity markets. Performance of this fund is measured against LIBOR plus four and a half percent. The remaining assets in the U.K. plan are invested in leveraged interest rate and inflation gilt funds of varying durations designed to broadly match the interest rate and inflation sensitivities of the plan's liabilities. The current target allocation for the assets is 65 percent diversified growth assets and 35 percent interest rate and inflation gilt funds. There are no categories of investments that are specifically prohibited by the U.K. plan, but there are general guidelines that ensure prudent investment action is taken. Such guidelines include the prevention of the plan from using derivatives for speculative purposes and limiting the concentration of risk in any one type of investment. Assets for the OPEB plan are invested in life insurance contracts issued by one of our insurance subsidiaries. The assets support life insurance benefits payable to certain former retirees covered under the OPEB plan. The terms of these contracts are consistent in all material respects with those the subsidiary offers to unaffiliated parties that are similarly situated. There are no categories of investments specifically prohibited by the OPEB plan. We believe our investment portfolios are well diversified by asset class and sector, with no undue risk concentrations in any one category. The categorization of fair value measurements by input level for the invested assets in our U.S. pension plans is shown below. The carrying values of investment-related receivables and payables approximate fair value due to the short-term nature of the securities and are not included in the following chart. Investments valued using net asset value (NAV) as a practical expedient are not required to be categorized by input level, but these investments are included as follows to reconcile to total invested assets. December 31, 2020 Quoted Prices Significant Other Significant NAV as a Practical Total (in millions of dollars) Invested Assets Equity Securities: U.S. Large Cap $ — $ — $ — $ 112.6 $ 112.6 U.S. Small Cap 25.8 — — 33.2 59.0 Global — — — 307.9 307.9 International — — — 31.6 31.6 Emerging Markets — — — 62.3 62.3 Fixed Income Securities: U.S. Government and Agencies 227.8 — — — 227.8 Corporate — 445.6 — — 445.6 State and Municipal Securities — 3.7 — — 3.7 Opportunistic Credits — — — 200.4 200.4 Real Estate — — — 108.9 108.9 Alternative Investments: Private Equity Direct Investments — — — 62.1 62.1 Private Equity Funds of Funds — — — 39.2 39.2 Cash Equivalents 46.3 — — — 46.3 Total Invested Assets $ 299.9 $ 449.3 $ — $ 958.2 $ 1,707.4 December 31, 2019 Quoted Prices Significant Significant NAV as a Practical Total (in millions of dollars) Invested Assets Equity Securities: U.S. Large Cap $ — $ — $ — $ 95.2 $ 95.2 U.S. Small Cap 23.0 — — 24.8 47.8 Global — — — 299.1 299.1 International — — — 28.3 28.3 Emerging Markets — — — 50.4 50.4 Fixed Income Securities: U.S. Government and Agencies 199.0 — — — 199.0 Corporate — 391.1 — — 391.1 State and Municipal Securities — 2.5 — — 2.5 Opportunistic Credits — — — 196.5 196.5 Real Estate — — — 108.4 108.4 Alternative Investments: Private Equity Direct Investments — — — 57.7 57.7 Private Equity Funds of Funds — — — 38.4 38.4 Cash Equivalents 82.4 — — — 82.4 Total Invested Assets $ 304.4 $ 393.6 $ — $ 898.8 $ 1,596.8 Level 1 investments consist of individual holdings that are valued based on unadjusted quoted prices from active markets for identical securities. Level 2 investments consist of individual holdings that are valued using observable inputs through market corroborated pricing. Certain equity, opportunistic credit, and real estate investments are valued based on the NAV of the underlying holdings. We made no adjustments to the NAV for 2020 or 2019. These investments have no unfunded commitments and no specific redemption restrictions. Alternative investments are valued based on NAV in a period ranging from one month to one quarter in arrears. We evaluate the need for adjustments to the NAV based on market conditions and discussions with fund managers in the period subsequent to the valuation date and prior to issuance of the financial statements. We made no adjustments to the NAV for 2020 or 2019. The private equity direct investments and private equity funds of funds generally cannot be redeemed by investors. Distributions of capital from the sale of underlying fund assets may occur at any time, but are generally concentrated between five The categorization of fair value measurements by input level for the invested assets in our U.K. pension plan is shown below. Investments valued using NAV as a practical expedient are not required to be categorized by input level, but these investments are included as follows to reconcile to total invested assets. December 31, 2020 Quoted Prices Significant Significant NAV as a Practical Total (in millions of dollars) Plan Assets Diversified Growth Assets $ — $ — $ — $ 176.0 $ 176.0 Fixed Interest and Index-linked Securities 116.8 — — — 116.8 Cash Equivalents 1.3 — — — 1.3 Total Plan Assets $ 118.1 $ — $ — $ 176.0 $ 294.1 December 31, 2019 Quoted Prices Significant Significant NAV as a Practical Total (in millions of dollars) Plan Assets Diversified Growth Assets $ — $ — $ — $ 163.0 $ 163.0 Fixed Interest and Index-linked Securities 89.6 — — — 89.6 Cash Equivalents 0.2 — — — 0.2 Total Plan Assets $ 89.8 $ — $ — $ 163.0 $ 252.8 Level 1 fixed interest and index-linked securities consist of individual funds that are valued based on unadjusted quoted prices from active markets for identical securities. Diversified growth assets are valued based on the NAV of the underlying holdings. We made no adjustments to the NAV for 2020 or 2019. These investments have no unfunded commitments and no specific redemption restrictions. The categorization of fair value measurements by input level for the assets in our OPEB plan is as follows: December 31, 2020 Quoted Prices Significant Other Significant Total (in millions of dollars) Assets Life Insurance Contracts $ — $ — $ 9.3 $ 9.3 December 31, 2019 Quoted Prices Significant Other Significant Total (in millions of dollars) Assets Life Insurance Contracts $ — $ — $ 9.9 $ 9.9 The fair value is represented by the actuarial present value of future cash flows of the contracts. Changes in our OPEB plan assets measured at fair value on a recurring basis using significant unobservable inputs (Level 3) during the years ended December 31, 2020 and 2019 are as follows: Year Ended December 31, 2020 Beginning Actual Return on Plan Assets Contributions Net Benefits and Expenses Paid End of Year (in millions of dollars) Life Insurance Contracts $ 9.9 $ 0.1 $ 9.9 $ (10.6) $ 9.3 Year Ended December 31, 2019 Beginning Actual Return on Plan Assets Contributions Net Benefits and Expenses Paid End of Year (in millions of dollars) Life Insurance Contracts $ 10.1 $ 0.2 $ 10.8 $ (11.2) $ 9.9 For the years ended December 31, 2020 and 2019, the actual return on plan assets relates solely to investments still held at the reporting date. There were no transfers into or out of Level 3 during 2020 or 2019. Measurement Assumptions We use a December 31 measurement date for each of our plans. The weighted average assumptions used in the measurement of our benefit obligations as of December 31 and our net periodic benefit costs for the years ended December 31 are as follows: Pension Benefits U.S. Plans U.K. Plan OPEB 2020 2019 2020 2019 2020 2019 Benefit Obligations Discount Rate 2.90 % 3.60 % 1.40 % 2.00 % 2.60 % 3.40 % Rate of Compensation Increase N/A N/A 2.80 % 2.90 % N/A N/A Net Periodic Benefit Cost Discount Rate 3.60 % 4.40 % 2.00 % 2.90 % 3.40 % 4.40 % Expected Return on Plan Assets 7.00 % 7.00 % 4.10 % 4.30 % 5.75 % 5.75 % Rate of Compensation Increase N/A N/A 2.90 % 3.70 % N/A N/A We set the discount rate assumption annually for each of our retirement-related benefit plans at the measurement date to reflect the yield on a portfolio of high quality fixed income corporate debt instruments matched against the projected cash flows for future benefits. Our long-term rate of return on plan assets assumption is selected from a range of probable return outcomes from an analysis of the asset portfolio. Our expectations for the future investment returns of the asset categories are based on a combination of historical market performance, evaluations of investment forecasts obtained from external consultants and economists, and current market yields. The methodology underlying the return assumption includes the various elements of the expected return for each asset class such as long-term rates of return, volatility of returns, and the correlation of returns between various asset classes. The expected return for the total portfolio is calculated based on the plan's strategic asset allocation. Investment risk is measured and monitored on an ongoing basis through annual liability measurements, periodic asset/liability studies, and quarterly investment portfolio reviews. Risk tolerance is established through consideration of plan liabilities, plan funded status, and corporate financial condition. Our mortality rate assumption reflects our best estimate, as of the measurement date, of the life expectancies of plan participants in order to determine the expected length of time for benefit payments. We derive our assumptions from industry mortality tables. The expected return assumption for the life insurance reserve for our OPEB plan is based on full investment in fixed income securities with an average book yield of 4.87 percent and 4.74 percent in 2020 and 2019, respectively. The rate of compensation increase assumption for our U.K. pension plan is generally based on periodic studies of compensation trends. At December 31, 2020 and 2019, the annual rates of increase in the per capita cost of covered postretirement health care benefits assumed for the next calendar year are 6.50 percent for benefits payable to both retirees prior to Medicare eligibility as well as Medicare eligible retirees. The rates are assumed to change gradually to 5.00 percent by 2027 for measurement at December 31, 2020 and remain at that level thereafter. The annual rates of increase in the per capita cost of covered postretirement health benefits do not apply to retirees whose postretirement health care benefits are provided through an exchange. Net Periodic Benefit Cost The following table provides the components of the net periodic benefit cost (credit) for the years ended December 31. Pension Benefits U.S. Plans U.K. Plan OPEB 2020 2019 2018 2020 2019 2018 2020 2019 2018 (in millions of dollars) Service Cost $ 11.0 $ 10.9 $ 9.1 $ — $ — $ — $ — $ — $ — Interest Cost 73.0 83.3 79.8 4.9 6.1 5.9 4.1 5.3 4.9 Expected Return on Plan Assets (106.7) (99.4) (104.5) (9.5) (8.9) (8.9) (0.5) (0.6) (0.6) Amortization of: Net Actuarial Loss (Gain) 18.7 20.2 21.7 1.1 0.9 0.6 — (2.5) — Prior Service Credit 0.1 — — — — — (0.2) (0.2) (0.2) Curtailment Gain — — — 0.1 — — — — — Total Net Periodic Benefit Cost $ (3.9) $ 15.0 $ 6.1 $ (3.4) $ (1.9) $ (2.4) $ 3.4 $ 2.0 $ 4.1 The service cost component of net periodic pension and postretirement benefit cost 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. Benefit Payments The following table provides expected benefit payments, which reflect expected future service, as appropriate. Pension Benefits U.S. Plans U.K. Plan OPEB (in millions of dollars) Year Gross Subsidy Payments Net 2021 $ 75.0 $ 6.1 $ 11.1 $ 0.1 $ 11.0 2022 78.4 6.1 10.5 0.1 10.4 2023 82.2 6.5 10.0 0.1 9.9 2024 86.1 7.0 9.5 0.1 9.4 2025 90.1 7.2 9.0 0.1 8.9 2026-2030 514.9 42.3 38.3 0.2 38.1 Funding Policy The funding policy for our U.S. qualified defined benefit plan is to contribute annually an amount at least equal to the minimum annual contribution required under ERISA and other applicable laws, but generally not greater than the maximum amount that can be deducted for federal income tax purposes. We had no regulatory contribution requirements for our U.S. qualified defined benefit plan in 2020 and made a de minimis amount of voluntary contributions during 2020 . We do not expect to make any contributions in 2021. The funding policy for our U.S. non-qualified defined benefit pension plan is to contribute the amount of the benefit payments made during the year. Our expected return on plan assets and discount rate will not affect the cash contributions we are required to make to our U.S. pension plan because such contributions are determined under the minimum funding requirements as set forth in ERISA. We made no contributions to our U.K. plan during 2020, nor do we expect to make any contributions in 2021, either voluntary or those required to meet the minimum funding requirements under U.K. legislation. Our OPEB plan represents a non-vested, non-guaranteed obligation, and current regulations do not require specific funding levels for these benefits, which are comprised of retiree life, medical, and dental benefits. It is our practice to use general assets to pay medical and dental claims as they come due in lieu of utilizing plan assets for the medical and dental benefit portions of our OPEB plan. Defined Contribution Plans We offer a 401(k) plan to all eligible U.S. employees under which a portion of employee contributions is matched. We match dollar-for-dollar up to 5.0 percent of base salary and any recognized sales and performance-based incentive compensation for employee contributions into the plan. We also make an additional non-elective contribution of 4.5 percent of earnings for all eligible employees and a separate transition contribution for eligible employees who met certain age and years of service criteria as of December 31, 2013. The separate transition contributions continued through December 31, 2020, at which point they expired. The 401(k) plan remains in compliance with ERISA guidelines and continues to qualify for a “safe harbor” from annual discrimination testing. We also offer a defined contribution plan to all eligible U.K. employees under which a portion of employee contributions is matched. We match two pounds for every one pound on the first 1.0 percent of employee contributions into the plan and match additional employee contributions pound-for-pound up to 5.0 percent of base salary. We also make an additional non-elective contribution of 6.0 percent of base salary for all eligible employees who met certain age and years of service criteria as of March 31, 2016. During the years ended December 31, 2020, 2019, and 2018, we recognized costs of $83.4 million, $77.3 million, and $72.7 million, respectively, for our U.S. defined contribution plan. We recognized costs of $5.0 million, $4.4 million, and $4.2 million in 2020, 2019, and 2018, respectively, for our U.K. defined contribution plan.

Stockholders' Equity and Earnin

Stockholders' Equity and Earnings Per Common Share	12 Months Ended
	Dec. 31, 2020
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: Year Ended December 31 2020 2019 2018 (in millions of dollars, except share data) Numerator Net Income $ 793.0 $ 1,100.3 $ 523.4 Denominator (000s) Weighted Average Common Shares - Basic 203,642.0 209,728.9 219,635.6 Dilution for Assumed Exercises of Stock Options and Nonvested Stock Awards 113.3 125.5 423.0 Weighted Average Common Shares - Assuming Dilution 203,755.3 209,854.4 220,058.6 Net Income Per Common Share Basic $ 3.89 $ 5.25 $ 2.38 Assuming Dilution $ 3.89 $ 5.24 $ 2.38
Stockholders' Equity Disclosure	Common Stock During the second quarter of 2019, our board of directors authorized the repurchase of up to $750.0 million of Unum Group's outstanding common stock through November 23, 2020, at which point the authorization expired. This authorization replaced the previous authorization of $750.0 million that was scheduled to expire on November 24, 2019. As of December 31, 2020, we did not authorize a new share repurchase program and there were no remaining amounts to be repurchased under either plan at December 31, 2020. Common stock repurchases, which are accounted for using the cost method and classified as treasury stock until otherwise retired, were as follows: Year Ended December 31 2020 2019 2018 (in millions) Shares Repurchased — 12.3 8.7 Cost of Shares Repurchased (1) $ — $ 400.4 $ 350.7 (1) Includes commissions of $0.4 million and $0.7 million for the years ended December 31, 2019 and 2018, respectively. 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.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
Disclosure of Compensation Related Costs, Share-based Payments	Stock-Based Compensation Description of Stock Plans Under the Stock Incentive Plan of 2017 (the 2017 Plan), up to 17 million shares of common stock are available for awards to our employees, officers, consultants, and directors. Awards may be in the form of stock options, stock appreciation rights, restricted stock, restricted stock units, performance share units, and other stock-based awards. Each full-value award, defined as any award other than a stock option or stock appreciation right, is counted as 1.76 shares. The exercise price for stock options issued cannot be less than the fair value of the underlying common stock as of the grant date. Stock options generally have a term of eight years after the date of grant and fully vest after three years. At December 31, 2020, approximately 10.1 million shares were available for future grants under the 2017 Plan. Under the Stock Incentive Plan of 2012 (the 2012 Plan), which was terminated in May 2017 for the purposes of any further grants, up to 20 million shares of common stock were available for awards to our employees, officers, consultants, and directors. Awards could be in the form of stock options, stock appreciation rights, restricted stock, restricted stock units, performance share units, and other stock-based awards. Each full-value award, defined as any award other than a stock option or stock appreciation right, is counted as 1.76 shares. Awards granted before the termination of the 2012 Plan remain outstanding in accordance with the plan's terms. Stock options generally have a term of eight years after the date of grant and fully vest after three years. We issue new shares of common stock for all of our stock plan vestings and exercises. Stock Success Units (SSUs) Activity for SSUs classified as equity is as follows: Weighted Average Shares Grant Date (000s) Fair Value Outstanding at December 31, 2019 — $ — Granted 321 18.78 Outstanding at December 31, 2020 321 18.78 During 2020, we issued SSUs with a weighted average grant date fair value per share of $18.78. SSUs vest over a six There were no shares that vested during 2020. At December 31, 2020, we had $5.7 million of unrecognized compensation cost related to SSUs that will be recognized over a weighted average period of 2.9 years. Performance Share Units (PSUs) Activity for PSUs classified as equity is as follows: Weighted Average Shares Grant Date (000s) Fair Value Outstanding at December 31, 2019 337 $ 44.11 Granted 323 23.49 Vested (135) 48.20 Forfeited (8) 35.81 Outstanding at December 31, 2020 517 30.31 During 2020, 2019, and 2018, we issued PSUs with a weighted average grant date fair value per share of $23.49, $41.57, and $44.19, respectively. Vesting for the PSUs occurs at the end of a three-year period and is contingent upon our achievement of prospective company performance goals and our total shareholder return relative to a board-approved peer group during the three PSU shares in the preceding table represent aggregate initial target awards and accrued dividend equivalents and do not reflect potential increases or decreases resulting from the application of the performance factor determined after the end of the performance periods. At December 31, 2020, the three an adjustment to reflect the application of the performance factor to the 2017 PSU grant, which occurred during the first quarter of 2020. At December 31, 2020, we had approximately $6.5 million of unrecognized compensation cost related to PSUs that will be recognized over a weighted average period of 1.6 years. The estimated compensation expense is adjusted for actual performance experience and is recognized ratably during the service period, or remaining service period, if and when it becomes probable that the performance conditions will be satisfied. Compensation cost for PSUs subject to accelerated vesting at the date of retirement eligibility is recognized over the implicit service period. The fair value of PSUs is estimated on the date of initial grant using the Monte-Carlo simulation m odel. Key assumptions used to value PSUs granted during the years shown are as follows: Year Ended December 31 2020 2019 2018 Expected Volatility (based on our and our peer group historical daily stock prices) 23 % 23 % 24 % Expected Life (equals the performance period) 3 years 3 years 3 years Risk Free Interest Rate (based on U.S. Treasury yields at the date of grant) 0.85 % 2.53 % 2.32 % Restricted Stock Units (RSUs) Activity for RSUs classified as equity is as follows: Weighted Average Shares Grant Date (000s) Fair Value Outstanding at December 31, 2019 1,044 $ 41.06 Granted 1,262 22.71 Vested (626) 40.11 Forfeited (87) 28.75 Outstanding at December 31, 2020 1,593 27.57 During 2020, 2019, and 2018, we issued RSUs with a weighted average grant date fair value per share of $22.71, $37.07, and $47.76, respectively. RSUs vest over a one three The total fair value of shares vested during 2020, 2019, and 2018 was $25.1 million, $19.5 million, and $18.1 million, respectively. At December 31, 2020, we had $21.2 million of unrecognized compensation cost related to RSUs that will be recognized over a weighted average period of 0.9 years. Cash-Settled RSUs Activity for cash-settled RSUs classified as a liability is as follows: Weighted Average Shares Grant Date (000s) Fair Value Outstanding at December 31, 2019 — $ — Granted 68 22.94 Outstanding at December 31, 2020 68 22.94 Cash-settled RSUs vest over a one three The amount payable per unit awarded is equal to the price per share of Unum Group's common stock at settlement of the award, and as such, we measure the value of the award each reporting period based on the current stock price. The effects of changes in the stock price during the service period are recognized as compensation cost over the service period. Changes in the amount of the liability due to stock price changes after the service period are recognized as compensation cost during the period in which the changes occur. At December 31, 2020, we had $1.1 million of unrecognized compensation cost related to cash-settled RSUs that will be recognized over a weighted average period of 1.1 years. The cash-settled RSUs have a weighted average grant date fair value per unit granted of $22.94. As of December 31, 2020, no amount of cash-settled RSUs have vested or been paid. Stock Options Stock option activity is summarized as follows: Remaining Intrinsic Shares Weighted Average Contractual Term Value (000s) Exercise Price (in years) (in millions) Outstanding at December 31, 2019 74 $ 24.09 Exercised (13) 23.35 Forfeited (21) 24.25 Outstanding at December 31, 2020 40 24.25 0.1 $ — Exercisable at December 31, 2020 40 $ 24.25 0.1 $ — All outstanding stock options at December 31, 2020 have vested. Stock options vest over a one three The intrinsic value of options exercised in 2020, 2019, and 2018 was $0.1 million, $0.3 million, and $0.7 million, respectively. There were no stock options granted or vested in the years 2018 through 2020. Expense Compensation expense for the stock plans, as reported in our consolidated statements of income, is as follows: Year Ended December 31 2020 2019 2018 (in millions of dollars) Performance Share Units $ 5.6 $ 5.0 $ 6.8 Restricted Stock Units and Cash-Settled Restricted Stock Units 23.9 21.0 19.0 Stock Success Units 0.4 — — Other 0.5 0.6 0.5 Total Compensation Expense, Before Income Tax $ 30.4 $ 26.6 $ 26.3 Total Compensation Expense, Net of Income Tax $ 26.1 $ 22.7 $ 20.9

Reinsurance

Reinsurance	12 Months Ended
	Dec. 31, 2020
Reinsurance Disclosures [Abstract]
Reinsurance	Reinsurance Reinsurance activity related to both our premium income and changes in reserves for future benefits are as follows: Year Ended December 31 2020 2019 2018 (in millions of dollars) Direct Premium Income $ 9,621.9 $ 9,576.3 $ 9,171.1 Reinsurance Assumed 94.1 116.5 142.6 Reinsurance Ceded (337.9) (327.2) (327.6) Net Premium Income $ 9,378.1 $ 9,365.6 $ 8,986.1 Ceded Benefits and Change in Reserves for Future Benefits $ 628.8 $ 650.1 $ 667.2 Effective December 16, 2020, 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", entered into a series of agreements (collectively referred to as the "reinsurance agreement") with Commonwealth Annuity and Life Insurance Company (Commonwealth), a subsidiary of Global Atlantic Financial Group, 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. Commonwealth has established and will maintain collateralized trust accounts for the benefit of the ceding companies to secure its obligations under the relevant reinsurance agreement. As part of the agreement, additional Closed Block individual disability business consisting of direct business not ceded in December 2020 and business assumed by the ceding companies from third parties, is expected to be reinsured in the first quarter of 2021, subject to receipt of required consents and regulatory approvals and the satisfaction or waiver of other customary closing conditions and is considered the second phase of this transaction. In connection with the first phase of the coinsurance agreement that closed in December 2020, the ceding companies paid a total cash ceding commission to Commonwealth of approximately $438 million and transferred additional assets consisting primarily of fixed maturity securities and cash totaling $6,669.8 million. 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), which represents approximately five percent of the reserves ceded to Commonwealth. As part of this agreement, PLC received a payment from Commonwealth of approximately $62 million. PLC will provide similar coverage to Commonwealth related to additional business ceded as part of the second phase of the transaction. 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. Under this volatility cover, annual settlements will be made equal to the difference between the actual and estimated cash flows and reserve changes during the year. Upon expiration of the 12-year period, a terminal settlement will be made based on the final disabled life reserves. As a result of the volatility cover, the reinsurance agreement covering the ALR cohort, does not pass risk transfer requirements under GAAP and is accounted for under the deposit method. As a result of this reinsurance agreement, we recognized the following as of the date of the agreement: • Net realized investment gains totaling $1,302.3 million related to the transfer of investments. • Increase in benefits and change in reserves for future benefits of $1,284.5 million resulting from the realization of previously unrealized investment gains and losses recorded in accumulated other comprehensive income. • Transaction costs totaling $21.0 million. • Tax benefit of $36.5 million. • Reinsurance recoverable of $6,141.5 million representing the ceded reserves related to policies on claim status (DLR cohort). • Cost of reinsurance, or the prepaid reinsurance premium, of $815.7 million related to the DLR cohort. • Deposit asset of $88.2 million related to the ALR cohort. The cost of reinsurance will be amortized over the expected run-off pattern of the ceded reserves for the DLR cohort and we recognized $2.6 million in amortization expense in 2020 subsequent to the execution of the agreement. The deposit asset will be adjusted over the 12-year period of the volatility cover based on cash flows related to the ALR cohort, settlement payments as determined above, and accretion of interest and will result in an amount equal to the expected disabled life reserve for the ALR cohort at the expiration of the volatility cover. Both the cost of reinsurance and the deposit asset are reported in Other Assets within our Consolidated Balance Sheets. As of December 31, 2020, Commonwealth accounted for approximately 59 percent of the total reinsurance recoverable and the majority of our total cost of reinsurance. Commonwealth has an A rating by A.M. Best Company (AM Best) and has also established collateralized trust accounts for our benefit to secure its obligations. In addition, nine other major companies, which account for approximately 35 percent of our reinsurance recoverable at December 31, 2020, are also rated A or better by either AM Best or Standard & Poor's Ratings Services (S&P), or are fully securitized by letters of credit or investment-grade fixed maturity securities held in trust. Approximately five percent of our reinsurance recoverable relates to business reinsured either with companies rated A- or better by AM Best or S&P, with overseas entities with equivalent ratings, or backed by letters of credit or trust agreements, or through reinsurance arrangements wherein we retain the assets in our general account. The remaining one percent of our reinsurance recoverable is held by companies either rated below A- by AM Best or S&P, or not rated.

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2020
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. The Unum US segment is comprised of group long-term and short-term disability insurance, which includes our medical stop-loss product as well as our fee-based leave management services and ASO business, group life and accidental death and dismemberment products, and supplemental and voluntary lines of business, which are comprised of individual disability, voluntary benefits, and dental and vision products. These products are marketed through our field sales personnel who work in conjunction with independent brokers and consultants. The Unum International segment is comprised of our operations in both the United Kingdom and Poland. Our Unum UK products include insurance for group long-term disability, group life, and supplemental lines of business which include dental, individual disability, and critical illness products. Our Unum Poland products include insurance for individual and group life with accident and health riders. Unum International's products are sold primarily through field sales personnel and independent brokers and consultants. The Colonial Life segment includes insurance for accident, sickness, and disability products, which includes our dental and vision products, life products, and cancer and critical illness products marketed to employees, on both a group and an individual basis, at the workplace through an independent contractor agency sales force and brokers. The Closed Block segment consists of group and individual long-term care, individual disability, and other insurance products no longer actively marketed. We discontinued offering individual long-term care in 2009 and group long-term care in 2012. Individual disability in this segment generally consists of policies we sold prior to the mid-1990s and entirely discontinued selling in 2004. Other insurance products include group pension, individual life and corporate-owned life insurance, reinsurance pools and management operations, and other miscellaneous product lines. The Corporate segment includes investment income on corporate assets not specifically allocated to a line of business, interest expense on corporate debt other than non-recourse debt, and certain other corporate income and expenses not allocated to a line of business. Costs Related to Organizational Design Update During the third quarter of 2020, we realigned certain parts of our organizational structure by shifting resources to accelerate growth, fund priority investments, and simplify and improve our business practices. In connection with this update, we incurred charges of $23.3 million, which primarily consisted of employee severance and benefit costs as well as certain costs related to lease terminations and the disposal of certain fixed assets. These costs were recorded within either compensation expense or other expenses in the consolidated statements of income and were included within our Corporate segment. This update did not result in the exit or disposal of any of our lines of business and we do not expect material additional costs associated with this update in the future. Acquisitions of Business On November 1, 2018, we acquired 100 percent of the shares and voting interests in Jaimini Health, Inc. (Jaimini Health), a dental health maintenance organization. The acquisition of Jaimini Health will broaden our employee benefit dental offerings in the U.S., particularly in the state of California, and is reported in our Unum US segment. On October 1, 2018, we acquired 100 percent of the shares and voting interests in Unum Poland, a financial protection benefits provider in Poland. This acquisition will expand our European presence, which we believe to be an attractive market for financial protection benefits. On January 1, 2018, we acquired 100 percent of the shares and voting interests in Leavelogic, Inc (Leavelogic), a leave management technology provider. The acquisition of Leavelogic will enhance our current leave management offerings by providing tools for employers and employees to better manage the family leave process and is reported in our Unum US segment. Segment information is as follows: Year Ended December 31 2020 2019 2018 (in millions of dollars) Premium Income Unum US Group Disability Group Long-term Disability $ 1,828.5 $ 1,823.1 $ 1,766.2 Group Short-term Disability 799.2 768.8 706.3 Group Life and Accidental Death & Dismemberment Group Life 1,640.5 1,662.0 1,583.7 Accidental Death & Dismemberment 163.9 165.7 156.3 Supplemental and Voluntary Individual Disability 456.0 440.7 425.4 Voluntary Benefits 875.2 910.2 895.7 Dental and Vision 255.6 246.1 202.8 6,018.9 6,016.6 5,736.4 Unum International Unum UK Group Long-term Disability 364.9 353.4 358.9 Group Life 108.5 115.7 110.8 Supplemental 99.8 89.5 81.7 Unum Poland 79.6 71.9 17.4 652.8 630.5 568.8 Colonial Life Accident, Sickness, and Disability 975.1 973.4 929.3 Life 376.4 351.6 328.4 Cancer and Critical Illness 360.5 360.0 346.1 1,712.0 1,685.0 1,603.8 Closed Block Long-term Care 666.9 651.6 648.3 Individual Disability 319.6 374.3 420.8 All Other 7.9 7.6 8.0 994.4 1,033.5 1,077.1 Total Premium Income $ 9,378.1 $ 9,365.6 $ 8,986.1 Unum US Unum International Colonial Life Closed Block Corporate Total (in millions of dollars) Year Ended December 31, 2020 Premium Income $ 6,018.9 $ 652.8 $ 1,712.0 $ 994.4 $ — $ 9,378.1 Net Investment Income 720.3 104.6 155.7 1,370.3 9.8 2,360.7 Other Income 154.9 0.5 1.1 66.6 1.1 224.2 Adjusted Operating Revenue $ 6,894.1 $ 757.9 $ 1,868.8 $ 2,431.3 $ 10.9 $ 11,963.0 Adjusted Operating Income (Loss) $ 825.4 $ 76.6 $ 335.4 $ 241.4 $ (200.8) $ 1,278.0 Interest and Debt Expense $ — $ — $ — $ 3.1 $ 185.1 $ 188.2 Depreciation and Amortization $ 421.7 $ 20.1 $ 273.9 $ 5.9 $ 0.7 $ 722.3 Year Ended December 31, 2019 Premium Income $ 6,016.6 $ 630.5 $ 1,685.0 $ 1,033.5 $ — $ 9,365.6 Net Investment Income 739.4 122.5 148.0 1,404.9 20.5 2,435.3 Other Income 142.8 0.6 3.4 71.3 3.1 221.2 Adjusted Operating Revenue $ 6,898.8 $ 753.6 $ 1,836.4 $ 2,509.7 $ 23.6 $ 12,022.1 Adjusted Operating Income (Loss) $ 1,031.1 $ 107.9 $ 344.5 $ 137.7 $ (188.6) $ 1,432.6 Interest and Debt Expense $ — $ — $ — $ 5.3 $ 172.1 $ 177.4 Depreciation and Amortization $ 422.8 $ 18.7 $ 276.6 $ 7.7 $ 1.7 $ 727.5 Year Ended December 31, 2018 Premium Income $ 5,736.4 $ 568.8 $ 1,603.8 $ 1,077.1 $ — $ 8,986.1 Net Investment Income 778.7 117.2 151.2 1,377.1 29.5 2,453.7 Other Income 118.5 0.4 1.2 75.4 2.7 198.2 Adjusted Operating Revenue $ 6,633.6 $ 686.4 $ 1,756.2 $ 2,529.6 $ 32.2 $ 11,638.0 Adjusted Operating Income (Loss) $ 1,014.6 $ 113.9 $ 335.2 $ 125.5 $ (171.1) $ 1,418.1 Interest and Debt Expense $ — $ — $ — $ 6.9 $ 160.4 $ 167.3 Depreciation and Amortization $ 389.6 $ 17.6 $ 257.3 $ 8.3 $ 1.0 $ 673.8 Unum Colonial Unum US International Life Total (in millions of dollars) Deferred Acquisition Costs Year Ended December 31, 2020 Beginning of Year $ 1,223.0 $ 26.4 $ 1,074.6 $ 2,324.0 Capitalization 291.5 12.1 272.6 576.2 Amortization (341.0) (7.4) (257.7) (606.1) Adjustment Related to Unrealized Investment Gains and Losses (4.8) — (17.6) (22.4) Foreign Currency — 0.9 — 0.9 End of Year $ 1,168.7 $ 32.0 $ 1,071.9 $ 2,272.6 Year Ended December 31, 2019 Beginning of Year $ 1,239.4 $ 20.0 $ 1,050.0 $ 2,309.4 Capitalization 334.5 12.8 311.3 658.6 Amortization (344.0) (7.1) (258.8) (609.9) Adjustment Related to Unrealized Investment Gains and Losses (6.9) — (27.9) (34.8) Foreign Currency — 0.7 — 0.7 End of Year $ 1,223.0 $ 26.4 $ 1,074.6 $ 2,324.0 Year Ended December 31, 2018 Beginning of Year $ 1,205.4 $ 21.3 $ 957.9 $ 2,184.6 Capitalization 344.0 8.1 315.9 668.0 Amortization (315.1) (8.2) (242.2) (565.5) Adjustment Related to Unrealized Investment Gains and Losses 5.1 — 18.4 23.5 Foreign Currency — (1.2) — (1.2) End of Year $ 1,239.4 $ 20.0 $ 1,050.0 $ 2,309.4 December 31 2020 2019 (in millions of dollars) Assets Unum US $ 19,034.2 $ 18,586.3 Unum International 4,206.2 3,869.1 Colonial Life 4,864.3 4,629.0 Closed Block 38,187.2 37,008.7 Corporate 4,333.9 2,920.3 Total Assets $ 70,625.8 $ 67,013.4 Revenue is primarily derived from sources in the United States, the United Kingdom, and Poland. There are no material revenues or assets attributable to foreign operations other than those reported in our Unum International segment. We report goodwill in our Unum US, Unum International, and Colonial Life segments, which are the segments expected to benefit from the originating business combinations. At December 31, 2020 and 2019 goodwill was $353.0 million and $351.7 million, respectively, with $280.0 million attributable to Unum US in each year, $45.3 million and $44.0 million, respectively, attributable to Unum International, and $27.7 million attributable to Colonial Life in each year. Stockholders' equity is allocated to the operating segments on the basis of an internal allocation formula that reflects the volume and risk components of each operating segment's business and aligns allocated equity with our target capital levels for regulatory and rating agency purposes. We modify this formula periodically to recognize changes in the views of capital requirements. 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 amortization of the cost of reinsurance as well as certain other items 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. As previously discussed in Note 12, we have exited a substantial portion of our closed block individual disability product line through the reinsurance agreement that was executed in December 2020. 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. 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. See above and Notes 6, 8, 12, and 15 for further discussion regarding the impacts of the 2018 and 2020 long-term care reserve increases, the group pension reserve increase, the impacts from of the Closed Block individual disability reinsurance transaction, the amortization of the cost of reinsurance, the net tax benefit from the reinsurance transaction, costs related to the organizational design update, the impairment loss on the ROU asset related to one of our operating leases for office space, and the cost related to the early retirement of debt. A reconciliation of total revenue to "adjusted operating revenue" and income before income tax to "adjusted operating income" is as follows: Year Ended December 31 2020 2019 2018 (in millions of dollars) Total Revenue $ 13,162.1 $ 11,998.9 $ 11,598.5 Excluding: Net Realized Investment Gain (Loss) 1,199.1 (23.2) (39.5) Adjusted Operating Revenue $ 11,963.0 $ 12,022.1 $ 11,638.0 Income Before Income Tax $ 964.0 $ 1,382.1 $ 627.8 Excluding: Net Realized Investment Gains and Losses Net Realized Investment Gain Related to Reinsurance Transaction 1,302.3 — — Net Realized Investment Loss, Other (103.2) (23.2) (39.5) Total Net Realized Investment Gain (Loss) 1,199.1 (23.2) (39.5) Items Related to Closed Block Individual Disability Reinsurance Transaction Change in Benefit Reserves and Transaction Costs (1,305.5) — — Amortization of the Cost of Reinsurance (2.6) — — Total Items Related to Closed Block Individual Disability Reinsurance Transaction (1,308.1) — — Long-term Care Reserve Increase (151.5) — (750.8) Group Pension Reserve Increase (17.5) — — Impairment Loss on ROU Asset (12.7) — — Costs Related to Organizational Design Update (23.3) — — Costs Related to Early Retirement of Debt — (27.3) — Adjusted Operating Income $ 1,278.0 $ 1,432.6 $ 1,418.1

Commitments and Contingent Liab

Commitments and Contingent Liabilities	12 Months Ended
	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies Disclosure	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. We also are cooperating with a Delaware Market Conduct examination involving the same issue, which is currently inactive. The legal and regulatory environment around unclaimed death benefits continues to evolve. It is possible that the current settlement and/or similar investigations by other state jurisdictions may result in payments to beneficiaries, the payment of abandoned funds under state law, and/or administrative penalties, the total of which may be in excess of the reserves established. 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 has scheduled oral argument for March 2, 2021. 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, depending on the nature, scope, and amount of any ruling, materially adversely affect our consolidated results of operations in a period.

Leases

Leases	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Lessee, Operating Leases	Leases We lease certain buildings and equipment under various noncancellable operating lease agreements. In addition, we have sub-lease agreements on a limited number of our building lease agreements. The majority of our building leases and sub-leases expire within a five ten one three We do not have any lease agreements or sub-lease agreements that contain variable lease payments. In addition, we do not have lease agreements or sub-lease agreements that contain residual value guarantees or impose any financial restrictions or covenants with the lessors. Operating lease information is as follows: Year Ended December 31 2020 2019 (in millions of dollars) Lease Cost Operating Lease Cost $ 48.6 $ 29.4 Sublease Income (1.3) (1.9) Total Lease Cost $ 47.3 $ 27.5 Other Information Cash Paid for Amounts Included in the Measurement of Lease Liabilities $ 30.8 $ 28.9 Weighted-Average Remaining Lease Term 6 years 7 years Weighted-Average Discount Rate 4.37 % 4.60 % Operating lease cost as calculated prior to the adoption of ASC 842 was $29.2 million for the year ended December 31, 2018. As of December 31, 2020, aggregate undiscounted minimum net lease payments and the reconciliation to our lease liability are as follows (in millions of dollars): 2021 $ 25.4 2022 22.8 2023 16.5 2024 12.7 2025 9.8 2026 and Thereafter 34.4 Total 121.6 Less Imputed Interest 15.7 Lease Liability $ 105.9 The right-of-use asset was $82.9 million and $108.6 million at December 31, 2020 and 2019, respectively. During 2020, we recognized an impairment loss of $12.7 million on the ROU asset related to one of our operating leases for office space that we do not plan to continue using to support our general operations. The impairment loss was recorded as a result of a decrease in the fair value of the ROU asset compared to its carrying value. The fair value of the ROU asset was determined based on a discounted cash flow model utilizing estimated market rates for sub-lease rentals. The impairment loss is recorded within other expenses in the consolidated statements of income and is included within our Corporate segment.

Statutory Financial Information

Statutory Financial Information	12 Months Ended
	Dec. 31, 2020
Statutory Financial Information [Abstract]
Statutory Financial Information	Statutory Net Income, Capital and Surplus, and Dividends Statutory net income for U.S. life insurance companies is reported in conformity with statutory accounting principles prescribed by the National Association of Insurance Commissioners (NAIC) and adopted by applicable domiciliary state laws. The commissioners of the states of domicile have the right to permit other specific practices that may deviate from prescribed practices. In connection with a financial examination of Unum America, which closed at the end of the second quarter of 2020, the Maine Bureau of Insurance (MBOI) concluded that Unum America’s long-term care statutory reserves are deficient by $2.1 billion as of December 31, 2018, the financial statement date of the examination period. The MBOI granted permission to Unum America on May 1, 2020, to phase in the additional statutory reserves over seven years beginning with year-end 2020 and ending with year-end 2026. This strengthening will be incorporated using explicitly agreed upon margins into our existing assumptions for annual statutory reserve adequacy testing. These actions will add margin to Unum America's best estimate assumptions. Our long-term care reserves and financial results reported under generally accepted accounting principles are not affected by the MBOI’s examination conclusion. We plan to fund the additional statutory reserves with expected cash flows. If the permitted practice was not granted by the MBOI to phase in these additional statutory reserves, the impact to the risk-based capital ratio would have triggered a regulatory event. The 2020 phase-in amount was recorded in the fourth quarter of 2020 and was approximately $229 million. Our other traditional U.S. life insurance subsidiaries have no prescribed or permitted statutory accounting practices that differ materially from statutory accounting principles prescribed by the NAIC. Unum America cedes certain blocks of business to Fairwind Insurance Company (Fairwind), which is an affiliated captive reinsurance subsidiary (captive reinsurer) domiciled in the United States, with Unum Group as the ultimate parent. This captive reinsurer was established for the limited purpose of reinsuring risks attributable to specified policies issued or reinsured by Unum America. Fairwind, which is domiciled in the state of Vermont, is required to follow GAAP in accordance with Vermont reporting requirements for pure captive insurance companies, unless the commissioner permits the use of some other basis of accounting. Fairwind has permission from Vermont to follow accounting practices that are generally consistent with current NAIC statutory accounting principles for its insurance reserves and invested assets supporting reserves. All other assets and liabilities are accounted for in accordance with GAAP, as prescribed by Vermont, which includes the full recognition of deferred tax assets which are more likely than not to be realized. Statutory accounting principles have a stricter limitation for the recognition of deferred tax assets. The impact of following the prescribed and permitted practices of Vermont rather than statutory accounting principles prescribed by the NAIC resulted in higher capital and surplus for Fairwind of approximately $287 million and $194 million as of December 31, 2020 and 2019 respectively. Included in the 2020 results for Fairwind was the $229 million increase to long-term care statutory reserves assumed from Unum America. Included in the 2018 results for Fairwind was the assumed portion of the statutory impact of the 2018 long-term care reserve increase. In December 2020, prior to entering into the reinsurance transaction with Commonwealth, Provident, Paul Revere Life, and Unum America recaptured their respective reinsurance agreements with Northwind Reinsurance Company, a wholly-owned domestic special purpose reinsurance subsidiary (Northwind Re). Northwind Re was established for the limited purpose of reinsuring risks attributable to specified policies issued or reinsured by the aforementioned companies, and has no material state prescribed accounting practices that differ from statutory accounting principles prescribed by the NAIC. See Note 12 for further discussion regarding the reinsurance transaction with Commonwealth. The operating results and capital and surplus of our traditional U.S. life insurance subsidiaries and our captive reinsurers, prepared in accordance with prescribed or permitted accounting practices of the NAIC or states of domicile, are presented separately below. Year Ended December 31 2020 2019 2018 (in millions of dollars) Combined Net Income (Loss) Traditional U.S. Life Insurance Subsidiaries $ 646.8 $ 982.1 $ 953.0 Captive Reinsurers $ (201.0) $ (122.5) $ (109.6) Combined Net Gain (Loss) from Operations Traditional U.S. Life Insurance Subsidiaries $ 726.2 $ 1,027.2 $ 959.8 Captive Reinsurers $ (149.4) $ (108.4) $ (110.9) December 31 2020 2019 (in millions of dollars) Combined Capital and Surplus Traditional U.S. Life Insurance Subsidiaries $ 3,875.0 $ 3,644.4 Captive Reinsurers $ 2,088.0 $ 1,908.3 Solvency II, a European Union directive prescribes capital requirements and risk management standards for the European insurance industry. As derived from the most recent annual financial statements for December 31, 2019, based on Solvency II requirements, regulatory net income and own funds available of our United Kingdom insurance subsidiary, Unum Limited, were £91.0 million and £656.1 million, respectively. Risk-based capital (RBC) standards for U.S. life insurance companies are prescribed by the NAIC. The domiciliary states of our U.S. insurance subsidiaries have all adopted a version of the RBC model formula of the NAIC, which prescribes a system for assessing the adequacy of statutory capital and surplus for all life and health insurers. The basis of the system is a risk-based formula that applies prescribed factors to the various risk elements in a life and health insurer's business to report a minimum capital requirement proportional to the amount of risk assumed by the insurer. The life and health RBC formula is designed to measure annually (i) the risk of loss from asset defaults and asset value fluctuations, (ii) the risk of loss from adverse mortality and morbidity experience, (iii) the risk of loss from mismatching of asset and liability cash flow due to changing interest rates, and (iv) business risks. The formula is used as an early warning tool to identify companies that are potentially inadequately capitalized. State insurance laws grant insurance regulators the authority to require various actions by, or take various actions against, insurers whose total adjusted capital does not meet or exceed certain RBC levels. The total adjusted capital of each of our U.S. insurance subsidiaries at December 31, 2020 is in excess of those RBC levels. Restrictions under applicable state insurance laws limit the amount of dividends that can be paid to a parent company from its insurance subsidiaries in any 12-month period without prior approval by regulatory authorities. For life insurance companies domiciled in the U.S., that limitation generally equals, depending on the state of domicile, either ten percent of an insurer's statutory surplus with respect to policyholders as of the preceding year end or the statutory net gain from operations, excluding realized investment gains and losses, of the preceding year. The payment of dividends to a parent company from a life insurance subsidiary is generally further limited to the amount of unassigned funds. Based on the restrictions under current law, approximately $974 million is available, without prior approval by regulatory authorities, during 2021 for the payment of dividends to Unum Group from its traditional U.S. life insurance subsidiaries. The ability of our captive insurers to pay dividends to their respective parent companies will depend on their satisfaction of applicable regulatory requirements and on the performance of the business reinsured. We also have the ability to receive dividends from our foreign subsidiaries, primarily in the U.K., for which the payment may be subject to applicable insurance company regulations and capital guidance. Approximately £170.0 million is considered distributable from Unum Limited during 2021, subject to local solvency standards and regulatory approval. Deposits

Unaudited Quarterly Results

Unaudited Quarterly Results	12 Months Ended
	Dec. 31, 2020
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information	The following is a summary of our unaudited quarterly results of operations for 2020 and 2019: 2020 4 th 3 rd 2 nd 1 st (in millions of dollars, except share data) Premium Income $ 2,319.9 $ 2,318.1 $ 2,368.7 $ 2,371.4 Net Investment Income 593.5 613.2 569.0 585.0 Net Realized Investment Gain (Loss) 1,304.9 4.4 33.8 (144.0) Total Revenue 4,273.5 2,996.3 3,021.2 2,871.1 Income Before Income Tax 124.7 299.6 337.6 202.1 Net Income 135.4 231.1 265.5 161.0 Net Income Per Common Share Basic 0.66 1.13 1.30 0.79 Assuming Dilution 0.66 1.13 1.30 0.79 2019 4 th 3 rd 2 nd 1 st (in millions of dollars, except share data) Premium Income $ 2,352.6 $ 2,331.2 $ 2,343.1 $ 2,338.7 Net Investment Income 616.3 599.4 624.9 594.7 Net Realized Investment Gain (Loss) 9.2 (26.2) (7.3) 1.1 Total Revenue 3,034.6 2,960.0 3,016.7 2,987.6 Income Before Income Tax 377.4 299.4 352.0 353.3 Net Income 296.2 242.0 281.2 280.9 Net Income Per Common Share Basic 1.44 1.16 1.33 1.31 Assuming Dilution 1.44 1.16 1.33 1.31 Items affecting the comparability of our financial results are as follows: • Fourth quarter of 2020 net realized investment gain of $1,302.3 million before tax and $1,028.8 million after tax, related to the transfer of investments for the Closed Block individual disability reinsurance transaction. • Fourth quarter of 2020 impacts from the Closed Block individual disability reinsurance transaction of $1,305.5 million before tax and $1,031.3 million after tax. • Fourth quarter of 2020 amortization of the cost of reinsurance related to the Closed Block individual disability reinsurance transaction of $2.6 million before tax and $2.0 million after tax. • Fourth quarter of 2020 net tax benefit from the Closed Block individual disability reinsurance transaction of $36.5 million. • Fourth quarter of 2020 reserve increases of $151.5 million and $17.5 million before tax and $119.7 million and $13.8 million after tax related to long-term care and group pension, respectively. • Third quarter of 2020 costs related to organizational design update of $23.3 million before tax and $18.6 million after tax. • Second quarter of 2020 impairment on ROU asset related to an operating lease for office space that we do not plan to continue using to support our general operations of $12.7 million before tax and $10.0 million after tax. • Fourth quarter of 2019 cost related to the early retirement of debt of $2.1 million before tax and $1.7 million after tax. • Third quarter of 2019 cost related to the early retirement of debt of $25.2 million before tax and $19.9 million after tax. See Notes 6, 7, 8, 12, 13, and 15 for further discussion of the above items.

Schedule I - Summary of Investm

Schedule I - Summary of Investments, Other Than Investments in Related Parties Schedule I - Summary of Investments, Other Than Investments in Related Parties	12 Months Ended
	Dec. 31, 2020
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Abstract]
Summary of Investments, Other Than Investments in Related Parties	SCHEDULE I--SUMMARY OF INVESTMENTS - OTHER THAN INVESTMENTS IN RELATED PARTIES as of December 31, 2020 Unum Group and Subsidiaries Type of Investment Cost or Amortized Cost (1) Fair Value Amount shown on the balance sheet (in millions of dollars) Fixed Maturity Securities: Bonds United States Government and Government Agencies and Authorities $ 559.0 $ 709.8 $ 709.8 States, Municipalities, and Political Subdivisions 3,609.9 4,261.2 4,261.2 Foreign Governments 902.9 1,168.2 1,168.2 Public Utilities 5,486.4 6,962.3 6,962.3 Mortgage/Asset-Backed Securities 1,019.9 1,107.7 1,107.7 All Other Corporate Bonds 24,958.8 29,918.6 29,918.6 Redeemable Preferred Stocks 9.6 9.5 9.5 Total Fixed Maturity Securities 36,546.5 44,137.3 44,137.3 Mortgage Loans 2,445.2 2,432.1 Policy Loans 3,683.9 3,683.9 Other Long-term Investments Derivatives — 19.8 (2) Perpetual Preferred Equity Securities 32.6 28.3 (3) Private Equity Partnerships 720.9 747.5 (3) Miscellaneous Long-term Investments 165.2 164.6 Short-term Investments 1,470.0 1,470.0 Total Investments $ 45,064.3 $ 52,683.5 (1) The amortized cost for fixed maturity securities and mortgage loans represents original cost reduced by repayments, write-downs from declines in fair value, amortization of premiums, and/or accretion of discounts. The amortized cost for these investments does not include allowance for expected credit losses. (2) Derivatives are carried at fair value. (3) The difference between amortized cost and carrying value for private equity partnerships and perpetual preferred equity securities primarily results from changes in the partnership owner's equity and the issuer's equity since acquisition, respectively.

Schedule II Condensed Finacial

Schedule II Condensed Finacial Information of Registrant	12 Months Ended
	Dec. 31, 2020
Condensed Financial Information Disclosure [Abstract]
Condensed Financial Information of Parent Company Only Disclosure	SCHEDULE II--CONDENSED FINANCIAL INFORMATION OF REGISTRANT Unum Group (Parent Company) BALANCE SHEETS December 31 2020 2019 (in millions of dollars) Assets Fixed Maturity Securities - at fair value (amortized cost: $349.5; $122.3) $ 355.1 $ 125.6 Other Long-term Investments 10.6 35.2 Short-term Investments 164.5 604.4 Investment in Subsidiaries 14,122.6 12,820.9 Deferred Income Tax 158.8 122.7 Other Assets 496.7 488.9 Total Assets $ 15,308.3 $ 14,197.7 Liabilities and Stockholders' Equity Liabilities Short-term Debt $ — $ 399.7 Long-term Debt 3,345.7 2,846.9 Pension and Postretirement Benefits 677.5 624.2 Other Liabilities 414.1 361.9 Total Liabilities 4,437.3 4,232.7 Stockholders' Equity Common Stock 30.7 30.6 Additional Paid-in Capital 2,376.2 2,348.1 Accumulated Other Comprehensive Income 374.2 37.3 Retained Earnings 11,269.6 10,728.7 Treasury Stock (3,179.7) (3,179.7) Total Stockholders' Equity 10,871.0 9,965.0 Total Liabilities and Stockholders' Equity $ 15,308.3 $ 14,197.7 See notes to condensed financial information. SCHEDULE II--CONDENSED FINANCIAL INFORMATION OF REGISTRANT (Continued) Unum Group (Parent Company) STATEMENTS OF OPERATIONS Year Ended December 31 2020 2019 2018 (in millions of dollars) Cash Dividends from Subsidiaries $ 974.6 $ 1,089.4 $ 1,135.4 Other Income 51.7 63.9 66.6 Total Revenue 1,026.3 1,153.3 1,202.0 Interest and Debt Expense 187.1 173.2 161.4 Cost Related to Early Retirement of Debt — 27.3 — Other Expenses 51.1 53.4 53.4 Total Expenses 238.2 253.9 214.8 Income of Parent Company Before Income Tax 788.1 899.4 987.2 Income Tax Benefit (15.3) (21.5) (1.7) Income of Parent Company 803.4 920.9 988.9 Equity in Undistributed Earnings (Loss) of Subsidiaries (10.4) 179.4 (465.5) Net Income 793.0 1,100.3 523.4 Other Comprehensive Income (Loss), Net of Tax 336.9 851.5 (924.2) Comprehensive Income (Loss) $ 1,129.9 $ 1,951.8 $ (400.8) See notes to condensed financial information. SCHEDULE II--CONDENSED FINANCIAL INFORMATION OF REGISTRANT (Continued) Unum Group (Parent Company) STATEMENTS OF CASH FLOWS Year Ended December 31 2020 2019 2018 (in millions of dollars) Cash Provided by Operating Activities $ 964.0 $ 1,000.0 $ 1,052.1 Cash Flows from Investing Activities Proceeds from Maturities of Fixed Maturity Securities 138.8 16.6 52.5 Proceeds from Sales and Maturities of Other Investments 46.6 5.6 — Purchase of Fixed Maturity Securities (384.7) — (47.9) Purchase of Other Investments (22.0) — (22.3) Net Sales (Purchases) of Short-term Investments 440.6 (309.0) 192.6 Cash Distributions to Subsidiaries (965.5) (389.0) (530.8) Net Purchases of Property and Equipment (81.6) (85.9) (73.2) Acquisition of Business — — (146.1) Cash Used by Investing Activities (827.8) (761.7) (575.2) Cash Flows from Financing Activities Short-term Debt Repayment (400.0) — (200.0) Issuance of Long-term Debt 494.1 841.9 290.7 Long-term Debt Repayment — (433.1) — Cost Related to Early Retirement of Debt — (25.9) — Issuance of Common Stock 4.4 6.1 4.6 Repurchase of Common Stock — (400.3) (356.2) Dividends Paid to Stockholders (231.9) (229.2) (215.6) Other, Net (1.4) (3.7) (9.3) Cash Used by Financing Activities (134.8) (244.2) (485.8) Increase (Decrease) in Cash $ 1.4 $ (5.9) $ (8.9) See notes to condensed financial information. SCHEDULE II--CONDENSED FINANCIAL INFORMATION OF REGISTRANT (Continued) Unum Group (Parent Company) NOTES TO CONDENSED FINANCIAL INFORMATION Note 1 - Basis of Presentation The accompanying condensed financial statements should be read in conjunction with the consolidated financial statements and notes thereto of Unum Group and subsidiaries. Note 2 - Debt Debt consists of the following: December 31 2020 2019 Interest Rates Maturities (in millions of dollars) Long-term Debt Outstanding Principal Senior Notes issued 1998 6.750 - 7.250% 2028 $ 335.8 $ 335.8 Senior Notes issued 2002 7.375% 2032 39.5 39.5 Senior Notes issued 2012 and 2016 5.750% 2042 500.0 500.0 Senior Notes issued 2014 4.000% 2024 350.0 350.0 Senior Notes issued 2015 3.875% 2025 275.0 275.0 Senior Notes issued 2019 4.000% 2029 400.0 400.0 Senior Notes issued 2019 4.500% 2049 450.0 450.0 Senior Notes issued 2020 4.500% 2025 500.0 — Medium-term Notes issued 1990 - 1996 7.000 - 7.190% 2023 - 2028 20.5 20.5 Junior Subordinated Debt Securities issued 1998 7.405% 2038 203.7 203.7 Junior Subordinated Debt Securities issued 2018 6.250% 2058 300.0 300.0 Fair Value Hedge Adjustment — (0.6) Less: Unamortized Net Premium 6.0 8.4 Unamortized Debt Issuance Costs (34.8) (35.4) Total Long-term Debt 3,345.7 2,846.9 Short-term Debt Outstanding Principal Senior Notes issued 2010 5.625% 2020 — 400.0 Less Unamortized Debt Issuance Costs — (0.3) Total Short-term Debt — 399.7 Total Debt $ 3,345.7 $ 3,246.6 The medium-term notes are non-callable. The junior subordinated debt securities are callable under limited, specified circumstances. The remaining debt is callable and may be redeemed, in whole or in part, at any time. The aggregate contractual principal maturities are $2.0 million in 2023, $350.0 million in 2024, $775.0 million in 2025, and $2,247.5 million thereafter. SCHEDULE II--CONDENSED FINANCIAL INFORMATION OF REGISTRANT (Continued) Unum Group (Parent Company) NOTES TO CONDENSED FINANCIAL INFORMATION - CONTINUED Unsecured Notes In September 2020, our $400.0 million 5.625% senior unsecured notes matured. In May 2020, we issued $500.0 million of 4.500% senior notes due 2025. The notes are callable at or above par and rank equally in the right of payment with all of our other unsecured and unsubordinated debt. During 2019 we purchased and retired (i) $30.3 million aggregate principal amount of our 7.190% medium-term notes due 2028; (ii) $30.0 million aggregate principal amount of our 7.250% senior notes due 2028; and (iii) $350.0 million aggregate principal amount of our 3.000% senior notes due 2021. In September 2019, we issued $450.0 million of 4.500% senior notes due 2049. The notes are callable at or above par and rank equally in the right of payment with all of our other unsecured and unsubordinated debt. In June 2019, we issued $400.0 million of 4.000% senior notes due 2029. The notes are callable at or above par and rank equally in the right of payment with all of our other unsecured and unsubordinated debt. In July 2018, our $200.0 million 7.000% senior unsecured notes matured. Fair Value Hedges As of December 31, 2019, we had $250.0 million notional amount of an interest rate swap which effectively converted certain of our unsecured senior notes into floating rate debt. Under this agreement, we received a fixed rate of interest and paid a variable rate of interest, based off of three-month LIBOR. During 2020, the $250.0 million notional amount of the interest rate swap matured in conjunction with the maturity of the hedged debt. Junior Subordinated Debt Securities In May 2018, we issued $300.0 million of 6.250% junior subordinated notes due 2058. The notes are redeemable at or above par on or after June 15, 2023 and rank equally in the right of payment with our other junior subordinated debt securities. In 1998, Provident Financing Trust I (the Trust), a 100 percent-owned finance subsidiary of Unum Group, issued $300.0 million of 7.405% capital securities due 2038 in a public offering. These capital securities are fully and unconditionally guaranteed by Unum Group, have a liquidation value of $1,000 per capital security, and have a mandatory redemption feature under certain circumstances. In connection with the capital securities offering, Unum Group issued to the Trust 7.405% junior subordinated deferrable interest debentures due 2038. The Trust is a variable interest entity of which Unum Group is not the primary beneficiary. Accordingly, the capital securities issued by the Trust are not included in the consolidated financial statements of Unum Group and subsidiaries and our liability represents the junior subordinated debt securities owed to the trust which is recorded in long-term debt. The sole assets of the Trust are the junior subordinated debt securities. The retirement of any liquidation amount regarding the capital securities by the Trust results in a corresponding retirement of principal amount of the junior subordinated debt securities. During 2019, the Trust purchased and retired $22.8 million aggregate liquidation amount of the 7.405% capital securities due 2038, which resulted in our purchase and retirement of a corresponding principal amount of our 7.405% junior subordinated debt securities due 2038. Cost Related to Early Retirement of Debt During 2019, we incurred costs of $27.3 million related to the early retirement of certain of our unsecured notes and junior subordinated debt securities as previously discussed. Interest Paid Interest paid on long-term and short-term debt and related securities during 2020, 2019, and 2018 was $176.6 million, $168.4 million, and $161.4 million, respectively. Credit Facilities We have access to two separate unsecured revolving credit facilities, each with a different syndicate of lenders. One of our credit facilities is under a five-year agreement and is effective through April 2024. The terms of this agreement provide for a borrowing capacity of $500.0 million with an option to be increased up to $700.0 million. We may also request, on up to two occasions, that the lenders' commitment termination dates be extended by one year. The credit facility provides for the issuance of letters of credit subject to certain terms and limitations. At December 31, 2020, letters of credit totaling $0.6 million had been issued from this credit facility, but there were no borrowed amounts outstanding. Our other credit facility is under a three-year agreement and is effective until April 2022. The terms of this agreement provide for a borrowing capacity of $100.0 million with an option to be increased up to $140.0 million. We may also request that the lenders' commitment termination dates be extended by one year. The credit facility provides for the issuance of letters of credit subject to certain terms and limitations. At December 31, 2020, there have been no letters of credit issued from the credit facility and there were no borrowed amounts outstanding. Borrowings under the credit facilities are for general corporate uses and are subject to financial covenants, negative covenants, and events of default that are customary. The two primary financial covenants include limitations based on our leverage ratio and consolidated net worth. We are also subject to covenants that limit subsidiary indebtedness. The credit facilities provide for borrowings at an interest rate based either on the prime rate or LIBOR.

Schedule III Supplementary Insu

Schedule III Supplementary Insurance Information	12 Months Ended
	Dec. 31, 2020
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Abstract]
Supplementary Insurance Information, for Insurance Companies Disclosure	SCHEDULE III--SUPPLEMENTARY INSURANCE INFORMATION Unum Group and Subsidiaries Segment Deferred Acquisition Costs Reserves for Future Policy Contract Benefits Unearned Premiums Policy and Contract Benefits (in millions of dollars) December 31, 2020 Unum US $ 1,168.7 $ 11,681.4 $ 44.0 $ 1,191.2 Unum International 32.0 2,794.2 123.3 175.6 Colonial Life 1,071.9 2,628.5 36.9 217.2 Closed Block — 32,548.9 145.1 271.4 Total $ 2,272.6 $ 49,653.0 $ 349.3 $ 1,855.4 December 31, 2019 Unum US $ 1,223.0 $ 11,367.8 $ 46.0 $ 1,117.5 Unum International 26.4 2,566.6 129.9 157.3 Colonial Life 1,074.6 2,477.2 36.8 189.4 Closed Block — 31,368.5 151.2 281.3 Total $ 2,324.0 $ 47,780.1 $ 363.9 $ 1,745.5 SCHEDULE III--SUPPLEMENTARY INSURANCE INFORMATION (Continued) Unum Group and Subsidiaries Segment Premium Income Net Investment Income 1 Benefits and Change in Reserves for Future Benefits 2 Amortization of Deferred Acquisition Costs All Other Expenses 3 Premiums Written 4 (in millions of dollars) December 31, 2020 Unum US $ 6,018.9 $ 720.3 $ 4,138.7 $ 341.0 $ 1,589.0 $ 4,088.6 Unum International 652.8 104.6 500.9 7.4 173.0 456.0 Colonial Life 1,712.0 155.7 906.5 257.7 369.2 1,252.4 Closed Block 994.4 1,370.3 3,426.8 — 240.2 979.3 Corporate — 9.8 — — 247.7 — Total $ 9,378.1 $ 2,360.7 $ 8,972.9 $ 606.1 $ 2,619.1 December 31, 2019 Unum US $ 6,016.6 $ 739.4 $ 4,022.1 $ 344.0 $ 1,501.6 $ 4,073.9 Unum International 630.5 122.5 469.8 7.1 168.8 443.7 Colonial Life 1,685.0 148.0 865.0 258.8 368.1 1,249.6 Closed Block 1,033.5 1,404.9 2,139.3 — 232.7 1,020.8 Corporate — 20.5 — — 239.5 — Total $ 9,365.6 $ 2,435.3 $ 7,496.2 $ 609.9 $ 2,510.7 December 31, 2018 Unum US $ 5,736.4 $ 778.7 $ 3,856.5 $ 315.1 $ 1,447.4 $ 3,873.0 Unum International 568.8 117.2 419.8 8.2 144.5 455.5 Colonial Life 1,603.8 151.2 824.9 242.2 353.9 1,277.3 Closed Block 1,077.1 1,377.1 2,919.2 — 235.7 1,065.7 Corporate — 29.5 — — 203.3 — Total $ 8,986.1 $ 2,453.7 $ 8,020.4 $ 565.5 $ 2,384.8 1 Net investment income is allocated based upon segmentation. Each segment has its own specifically identified assets and receives the investment income generated by those assets. 2 Included in 2020 and 2018 are reserve increases of $151.5 million and $750.8 million, respectively in the Closed Block segment related to our long-term care business, as well as a reserve increase of $17.5 million in 2020 related to our group pension Closed Block business. Also included in 2020 is an increase in benefits and change in reserves for future benefits of $1,284.5 million in 2020 resulting from the recognition of the adjustment related to unrealized investment gains and losses previously recognized in accumulated other comprehensive income related to the Closed Block individual disability reinsurance transaction. 3 Includes commissions, interest and debt expense, cost related to early retirement of debt, deferral of acquisition costs, compensation expense, and other expenses. Where not directly attributable to a segment, expenses are generally allocated based on activity levels, time information, and usage statistics. Included in 2020 is the amortization of the cost of reinsurance of $2.6 million and transaction costs of $21.0 million related to the Closed Block individual disability reinsurance transaction. Also included in 2020 is a ROU asset impairment of $12.7 million related to one of our operating leases for office space that we do not plan to continue using to support general operations and costs related to organizational design updates of $23.3 million in Corporate. 4 Excludes life insurance.

Schedule IV Reinsurance

Schedule IV Reinsurance	12 Months Ended
	Dec. 31, 2020
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Abstract]
Supplemental Schedule of Reinsurance Premiums for Insurance Companies	SCHEDULE IV--REINSURANCE Unum Group and Subsidiaries Gross Amount Ceded to Other Companies Assumed from Other Companies Net Amount Percentage Amount Assumed to Net (in millions of dollars) Year Ended December 31, 2020 Life Insurance in Force $ 979,755.7 $ 41,550.9 $ 896.4 $ 939,101.2 0.1 % Premium Income: Life Insurance $ 2,536.8 $ 141.9 $ 8.0 $ 2,402.9 0.3 % Accident, Health, and Other Insurance 7,085.1 196.0 86.1 6,975.2 1.2 % Total $ 9,621.9 $ 337.9 $ 94.1 $ 9,378.1 1.0 % Year Ended December 31, 2019 Life Insurance in Force $ 990,371.0 $ 41,669.8 $ 1,018.4 $ 949,719.6 0.1 % Premium Income: Life Insurance $ 2,549.7 $ 137.2 $ 8.2 $ 2,420.7 0.3 % Accident, Health, and Other Insurance 7,026.6 190.0 108.3 6,944.9 1.6 % Total $ 9,576.3 $ 327.2 $ 116.5 $ 9,365.6 1.2 % Year Ended December 31, 2018 Life Insurance in Force $ 937,300.8 $ 40,902.8 $ 1,089.3 $ 897,487.3 0.1 % Premium Income: Life Insurance $ 2,442.1 $ 138.2 $ 8.7 $ 2,312.6 0.4 % Accident, Health, and Other Insurance 6,729.0 189.4 133.9 6,673.5 2.0 % Total $ 9,171.1 $ 327.6 $ 142.6 $ 8,986.1 1.6 %

Schedule V Valuation and Qualif

Schedule V Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2020
SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract]
Schedule of Valuation and Qualifying Accounts Disclosure	SCHEDULE V--VALUATION AND QUALIFYING ACCOUNTS Unum Group and Subsidiaries Description Balance at Beginning of Year 3 Additions Charged to Costs and Expenses Additions Charged to Other Accounts 1 Deductions 2 Balance at End of Year (in millions of dollars) Year Ended December 31, 2020 Real Estate reserve (deducted from other long-term investments) $ 0.3 $ — $ — $ 0.3 $ — Allowance for expected credit losses (deducted from accounts and premiums receivable) $ 23.8 $ 34.2 $ 0.1 $ 19.3 $ 38.8 Allowance for expected credit losses (deducted from reinsurance recoverable) $ 1.8 $ 10.1 $ — $ 0.2 $ 11.7 Year Ended December 31, 2019 Real Estate reserve (deducted from other long-term investments) $ 1.5 $ — $ — $ 1.2 $ 0.3 Allowance for doubtful accounts (deducted from accounts and premiums receivable) $ 9.9 $ 5.3 $ 0.1 $ 6.9 $ 8.4 Year Ended December 31, 2018 Real Estate reserve (deducted from other long-term investments) $ 4.2 $ 0.6 $ — $ 3.3 $ 1.5 Allowance for doubtful accounts (deducted from accounts and premiums receivable) $ 6.4 $ 5.6 $ — $ 2.1 $ 9.9 1 Additions charged to other accounts are comprised of amounts related to fluctuations in the foreign currency exchange rate. 2 Deductions include amounts deemed to reduce exposure of expected losses on premium and accounts receivables and reinsurance recoverable, probable losses on Real Estate reserve, amounts deemed uncollectible, and amounts related to fluctuations in the foreign currency exchange rate. 3 ASC 326 "Financial Instruments - Credit Losses" was adopted resulting in a beginning balance adjustment of $13.5 million to Allowance for expected credit losses (deducted from accounts and premiums receivable) and the now separately reported $1.8 million beginning balance for Allowance for expected credit losses (deducted from reinsurance recoverable). Certain items not reported above include the allowance for expected credit losses on mortgage loans, the allowance for credit losses on fixed maturity securities, and the deferred tax asset valuation allowance. See Notes 3 and 7 of the "Notes to Consolidated Financial Statements" contained herein in Item 8 for a discussion of these items.

Signficant Accounting Policies

Signficant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	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). Such accounting principles differ from statutory accounting principles (see Note 16). Intercompany transactions have been eliminated.
Use of Estimates	Use of Estimates : The preparation of financial statements in conformity with GAAP requires us to make estimates and assumptions that affect amounts reported in the financial statements and accompanying notes. Such estimates and assumptions could change in the future as more information becomes known, which could impact the amounts reported and disclosed herein.
Fixed Maturity Securities	Fixed Maturity Securities : Fixed maturity securities include long-term bonds and redeemable preferred stocks. Our fixed maturity securities are classified as available-for-sale and reported at fair value. Changes in the fair value of available-for-sale fixed maturity securities, except for amounts related to impairment and credit losses recognized in earnings, are reported as a component of other comprehensive income. These amounts are net of income tax and valuation adjustments to deferred acquisition costs and reserves for future policy and contract benefits which would have been recorded had the related unrealized gain or loss on these securities been realized. Interest income is recorded as part of net investment income when earned, using an effective yield method giving effect to amortization of premium and accretion of discount. Included within fixed maturity securities are mortgage-backed and asset-backed securities. We recognize investment income on these securities using a constant effective yield based on projected prepayments of the underlying loans and the estimated economic life of the securities. Actual prepayment experience is reviewed periodically, and effective yields are recalculated when differences arise between prepayments originally projected and the actual prepayments received and currently projected. The effective yield is recalculated on a retrospective basis, and the adjustment is reflected in net investment income. For fixed maturity securities on which collection of investment income is uncertain, we discontinue the accrual of investment income and recognize investment income when interest and dividends are received. Payment terms specified for fixed maturity securities may include a prepayment penalty for unscheduled payoff of the investment. Prepayment penalties are recognized as investment income when received. In determining when a decline in fair value below amortized cost of a fixed maturity security is a credit loss, we evaluate available information, both positive and negative, in reaching our conclusions. In particular, we consider the strength of the issuer's balance sheet, its debt obligations and near-term funding requirements, 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. Although all available and applicable factors are considered in our analysis, our expectation of recovering the entire amortized cost basis of the security, whether we intend to sell the security, whether it is more likely than not that we will be required to sell the security before recovery of its amortized cost, and whether the security is current on principal and interest payments are the most critical factors in determining whether impairments represent credit losses. The significance of the decline in value is also an important factor, but we generally do not record an impairment loss based solely on this factor, since often other more relevant factors will impact our evaluation of a security.
Mortgage Loans	Mortgage Loans : Mortgage loans are generally held for investment and are carried at amortized cost less an allowance for expected credit losses. Interest income is accrued on the principal amount of the loan based on the loan's contractual interest rate. Prepayment penalties are recognized as investment income when received. For mortgage loans on which collection of interest income is uncertain, we discontinue the accrual of interest and recognize it in the period when an interest payment is received. We typically do not resume the accrual of interest on mortgage loans on nonaccrual status until there are significant improvements in the underlying financial condition of the borrower. We consider a loan to be delinquent if full payment is not received in accordance with the contractual terms of the loan. 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. 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 impairment. 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. Additions and reductions to our allowance for credit losses on mortgage loans are reported as a component of net realized investment gains and losses. See Note 3.
Policy Loans	Policy Loans : Policy loans
Investments	Other Long-term Investments : Other long-term investments are comprised primarily of tax credit partnerships, private equity partnerships, and real estate. Tax credit partnerships in which we have invested were formed for the purpose of investing in the construction and rehabilitation of low-income housing. Because the partnerships are structured such that there is no return of principal, the primary sources of investment return from our tax credit partnerships are tax credits and tax benefits derived from passive losses on the investments, both of which may exhibit variability over the life of the investment. These partnerships are accounted for using either the proportional or the effective yield method, depending primarily on whether the tax credits are guaranteed through a letter of credit, a tax indemnity agreement, or another similar arrangement. Tax credits received from these partnerships are reported in our consolidated statements of income as either a reduction of premium tax or a reduction of income tax. The amortization of the principal amount invested in these partnerships is reported as a component of either premium tax or income tax. Our investments in private equity partnerships are passive in nature and represent funds that are primarily invested in private credit, private equity, and real assets. We account for our investments in these partnerships using either the equity method or at fair value through net income depending on the level of ownership and the degree of our influence over partnership operating and financial policies. For investments in partnerships accounted for under the equity method, we report our investments at our share of the partnership's net asset value (NAV) and record our portion of partnership earnings as a component of net investment income. For investments in partnerships accounted for at fair value through net income, we also report our investments at our share of the partnership's NAV as a practical expedient for fair value with increases or decreases recorded as a component of net investment income. Distributions received from the funds arise from income generated by the underlying investments as well as the liquidation of the underlying investments and there is generally not a public market for these investments. Investment real estate is primarily comprised of property held for the production of income and property held for sale. Property held for the production of income is carried at cost less accumulated depreciation and any write-downs to fair value for impairment losses. Depreciation is recorded on a straight-line basis over the estimated useful life of the asset. A review for impairment is made whenever events or circumstances indicate that the carrying value may not be recoverable. An impairment loss is recognized when the carrying value of the property exceeds the expected undiscounted cash flows generated from the property, at which point the carrying value is written down to an estimated fair value. Real estate held for sale is carried at the lower of depreciated cost or fair value less estimated selling costs and is not further depreciated once classified as such. See Notes 2 and 3 for further discussion of our other long-term investments. Short-term Investments :
Cash and Bank Deposits	Cash and Bank Deposits: Cash and bank deposits include cash on hand and non-interest bearing cash and deposit accounts.
Derivative Financial Instruments	Derivative Financial Instruments : Derivative financial instruments (including certain derivative instruments embedded in other contracts) are recognized as either other long-term investments or other liabilities in our consolidated balance sheets and are reported at fair value. The accounting for a derivative depends on whether it has been designated and qualifies as part of a hedging relationship, and further, on the type of hedging relationship. To qualify for hedge accounting, at the inception of the hedging transaction, we formally document the risk management objective and strategy for undertaking the hedging transaction, as well as the designation of the hedge as either a fair value hedge or a cash flow hedge. Included in this documentation is how the hedging instrument is expected to hedge the designated risk(s) related to specific assets or liabilities on the balance sheet or to specific forecasted transactions as well as a description of the method that will be used to retrospectively and prospectively assess the hedging instrument's effectiveness. A derivative designated as a hedging instrument must be assessed as being highly effective in offsetting the designated risk(s) of the hedged item. Hedge effectiveness is formally assessed at inception and periodically throughout the life of the designated hedging relationship, using qualitative and quantitative methods. Qualitative methods include comparison of critical terms of the derivative to the hedged item. Quantitative methods include regression or other statistical analysis of changes in fair value or cash flows associated with the hedge relationship. Changes in the fair value of a derivative designated as a fair value hedge and changes in the fair value of the hedged item attributable to the risk being hedged are recognized in earnings as a component of net realized investment gain or loss during the period of change in fair value. For gains or losses on the derivative instrument that are excluded from the assessment of hedge effectiveness, those gains and losses are recognized in other comprehensive income or loss and amortized into earnings in the same income statement line as the related hedged item. The gain or loss on the termination of a fair value hedge is recognized in earnings as a component of net realized investment gain or loss during the period in which the termination occurs. When interest rate swaps are used in hedge accounting relationships, periodic settlements are recorded in the same income statement line as the related settlements of the hedged items. Changes in the fair value of a derivative designated as a cash flow hedge are reported in other comprehensive income and reclassified into earnings and reported on the same income statement line item as the hedged item and in the same period or periods during which the hedged item affects earnings. The gain or loss on the termination of an effective cash flow hedge is reported in other comprehensive income and reclassified into earnings and reported on the same income statement line item as the hedged item and in the same period or periods during which the hedged item affects earnings. Gains or losses on the termination of ineffective fair value or cash flow hedges are reported in earnings as a component of net realized investment gain or loss. In the event a hedged item is disposed of or the anticipated transaction being hedged is no longer likely to occur, we will terminate the related derivative and recognize the gain or loss on termination in current earnings as a component of net realized investment gain or loss. In the event a hedged item is disposed of subsequent to the termination of the hedging transaction, we reclassify any remaining gain or loss on the hedge out of accumulated other comprehensive income into earnings as a component of the same income statement line item wherein we report the gain or loss on disposition of the hedged item. For a derivative not designated as a hedging instrument, changes in the fair value of the derivative, together with the payment of periodic fees, if applicable, are recognized in earnings as a component of net realized investment gain or loss during the period of change in fair value. Cash flow activity from the settlement of derivative contracts is reported in the consolidated statements of cash flows as a component of proceeds from sales and maturities of other investments.
Fair Value Measurement	Fair Value Measurement: Certain assets and liabilities are reported at fair value in our consolidated balance sheets and in our notes to our consolidated financial statements. We define fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. Therefore, fair value represents an exit price, not an entry price. The exit price objective applies regardless of our intent and/or ability to sell the asset or transfer the liability at the measurement date. Assets or liabilities with readily available actively 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. When actively quoted prices are not available, fair values are based on quoted prices in markets that are not active, quoted prices for similar but not identical assets or liabilities, or other observable inputs. If observable inputs are not available, unobservable inputs and/or adjustments to observable inputs requiring management judgment are used to determine fair value. We categorize our assets and liabilities measured at estimated fair value into a three-level hierarchy, based on the significance of the inputs. The fair value hierarchy gives the highest priority to inputs which are unadjusted and represent quoted prices in active markets for identical assets or liabilities (Level 1) and the lowest priority to unobservable inputs (Level 3). See Note 2.
Realized Investment Gains and Losses	Realized Investment Gains and Losses : Realized investment gains and losses are reported as a component of revenue in the consolidated statements of income and are based upon specific identification of the investments sold. See Note 3.
Allowance for Credit Losses on Premiums Receivable	Allowance for Credit Losses on Premiums Receivable : We establish an allowance for credit losses on premiums receivable, which is deducted from the gross amount of our receivable balance, to present the net amount we expect to collect on this asset. The allowance is forward-looking in nature and is calculated based on considerations regarding both historical events and future expectations. Periodic changes in the allowance are recorded through earnings. The allowance on our premiums receivable is primarily determined using an aging analysis as well as historical lapse and delinquency rates by line of business, adjusted for key factors that may impact our future expectation of premium receipts such as changes in customer demographics, business practices, economic conditions, and product offerings. We write off premiums receivable amounts when determined to be uncollectible, which is based on various factors, including the aging of premiums receivable past the due date and specific communication with customers. At January 1, 2020 and December 31, 2020, the allowance for expected credit losses on premium receivables was $23.8 million and $38.8 million, respectively, on gross premium receivables of $543.0 million and $525.8 million, respectively. The allowance at January 1, 2020 includes amounts
Deferred Acquisition Costs	Deferred Acquisition Costs : Incremental direct costs associated with the successful acquisition of new or renewal insurance contracts have been deferred. Such costs include commissions, other agency compensation, certain selection and policy issue expenses, and certain field expenses. Acquisition costs that do not vary with the production of new business, such as commissions on group products which are generally level throughout the life of the policy, are excluded from deferral. Deferred acquisition costs are subject to recoverability testing at the time of policy issue and loss recognition testing in subsequent years. Deferred acquisition costs related to non-interest sensitive policies are amortized in proportion to the premium income we expect to receive over the lives of the policies. Deferred acquisition costs related to interest sensitive policies are amortized over the lives of the policies in relation to the present value of estimated gross profits from surrender charges, mortality margins, investment returns, and expense margins. Deviations from projections result in a change to the rate of amortization in the period during which such events occur. Generally, the amortization periods for these policies approximate the estimated lives of the policies. For certain products, policyholders can elect to modify product benefits, features, rights, or coverages by exchanging a contract for a new contract or by amendment, endorsement, or rider to a contract, or by the election of a feature or coverage within a contract. These transactions are known as internal replacement transactions. Internal replacement transactions wherein the modification does not substantially change the policy are accounted for as continuations of the replaced contracts. Unamortized deferred acquisition costs from the original policy continue to be amortized over the expected life of the new policy, and the costs of replacing the policy are accounted for as policy maintenance costs and expensed as incurred. Internal replacement transactions, principally on group contracts, that result in a policy that is substantially changed are accounted for as an extinguishment of the original policy and the issuance of a new policy. Unamortized deferred acquisition costs on the original policy that was replaced are immediately expensed, and the costs of acquiring the new policy are capitalized and amortized in accordance with our accounting policies for deferred acquisition costs.
Goodwill	Goodwill: Goodwill is the excess of the amount paid to acquire a business over the fair value of the net assets acquired. We review the carrying amount of goodwill for impairment on an annual basis, or more frequently if events or changes in circumstances indicate that the carrying amount might not be recoverable. Goodwill impairment testing compares the fair value of a reporting unit with its carrying amount, including goodwill.  If the fair value of the reporting unit to which the goodwill relates is less than the carrying amount of the reporting unit, an impairment charge is recognized for the amount by which the carrying amount exceeds the fair value of the reporting unit in an amount not to exceed the total amount of goodwill allocated to the reporting unit.
Property and Equipment	Property and Equipment: Property and equipment is reported at cost less accumulated depreciation, which is calculated on the straight-line method over the estimated useful life. The accumulated depreciation for property and equipment was $1,239.9 million and $1,195.3 million as of December 31, 2020 and 2019, respectively.
Value of Business Acquired	Value of Business Acquired : Value of business acquired represents the present value of future profits recorded in connection with the acquisition of a block of insurance policies. The asset is amortized based upon expected future premium income for non-interest sensitive insurance policies and estimated future gross profits from surrender charges, mortality margins, investment returns, and expense margins for interest sensitive insurance policies. The value of business acquired, which is included in other assets in our consolidated balance sheets, was $83.8 million and $88.7 million at December 31, 2020 and 2019, respectively. The accumulated amortization for value of business acquired was $153.7 million and $144.1 million as of December 31, 2020 and 2019, respectively.
Policy and Contract Benefits	Policy and Contract Benefits : Policy and contract benefits represent amounts paid and expected to be paid based on reported losses and estimates of incurred but not reported losses for non-interest sensitive life and accident and health products. For interest sensitive products, benefits are the amounts paid and expected to be paid on insured claims in excess of the policyholders' policy fund balances.
Reserves for Policy and Contract Benefits	Reserves for Policy and Contract Benefits : Policy reserves represent future policy and contract benefits for claims not yet incurred. Policy reserves for non-interest sensitive life and accident and health products are determined using the net level premium method. The reserves are calculated based upon assumptions as to interest, persistency, morbidity, and mortality that were appropriate at the date of issue. Discount rate assumptions are based on actual and expected net investment returns. Persistency assumptions are based on our actual historical experience adjusted for future expectations. Claim incidence and claim resolution rate assumptions related to morbidity and mortality are based on actual experience or industry standards adjusted as appropriate to reflect our actual experience and future expectations. The assumptions vary by plan, year of issue, and policy duration and include a provision for adverse deviation. Policy reserves for group single premium annuities are developed on a net single premium method. The reserves are calculated based on assumptions as to interest, mortality, and retirement that were appropriate at the date of issue. Mortality assumptions are based upon industry standards adjusted as appropriate to reflect our actual experience and future expectations. The assumptions vary by year of issue. Policy reserves for interest sensitive products are principally policyholder account values. Policy reserves require ongoing loss recognition testing. We perform loss recognition tests on our policy reserves annually, or more frequently if appropriate, using best estimate assumptions as of the date of the test, without a provision for adverse deviation. We group the policy reserves for each major product line within a segment when we perform the loss recognition tests. If the policy reserves determined using these best estimate assumptions are higher than our existing policy reserves net of any deferred acquisition cost balance, the existing policy reserves are increased or deferred acquisition costs are reduced to immediately recognize the deficiency. This becomes the new basis for policy reserves going forward, subject to future loss recognition testing. Claim reserves represent future policy and contract benefits for claims that have been incurred or are estimated to have been incurred but not yet reported to us. Our claim reserves relate primarily to disability and long-term care policies and are calculated based on assumptions as to interest and claim resolution rates that are currently appropriate. Claim resolution rate assumptions are based on our actual experience. The interest rate assumptions used for discounting claim reserves are based on projected portfolio yield rates, after consideration for defaults and investment expenses, for the assets supporting the liabilities for the various product lines. Unlike policy reserves for which assumptions are generally established and locked in at the time of policy issuance, claim reserves are subject to revision as current claim experience and projections of future factors affecting claim experience change. Claim reserves do not include a provision for adverse deviation. See Note 6.
Policyholders' Funds	Policyholders Funds : Policyholders' funds represent customer deposits plus interest credited at contract rates. We control interest rate risk by investing in quality assets which have an aggregate duration that closely matches the expected duration of the liabilities.
Income Tax	Income Tax : Deferred taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial statement purposes and the amounts used for income tax purposes. Deferred taxes have been measured using enacted statutory income tax rates and laws that are currently in effect. We record adjustments to our deferred taxes resulting from tax rate changes through income as of the date of enactment. We record deferred tax assets for tax positions taken in the U.S. and other tax jurisdictions based on our assessment of whether a position is more likely than not to be sustained upon examination based solely on its technical merits. A valuation allowance is established for deferred tax assets when it is more
Short-term and Long-term Debt	Short-term and Long-term Debt : Debt is generally carried at the unpaid principal balance, net of unamortized discount or premium and deferred debt issuance costs. Short-term debt consists of debt due within the next twelve months, including that portion of debt otherwise classified as long-term. The amortization of the original issue discount or premium as well as deferred debt issuance costs are recognized as a component of interest expense over the period the debt is expected to be outstanding. The carrying amount of long-term debt that is part of a fair value hedge program includes an adjustment to reflect the effect of the change in fair value attributable to the risk being hedged. Net interest settlements for fair value hedges on our long-term debt are recognized as a component of interest expense. See Note 8.
Right-of-Use Asset (ROU) and Lease Liability	Right-of-Use Asset (ROU) and Lease Liability : ROU assets represent our right to use an underlying asset for a specified lease term and are included in other assets in our consolidated balance sheet. Lease liabilities represent the present value of lease payments that we are obligated to pay arising from a lease and are included in other liabilities in our consolidated balance sheet. We determine if an arrangement is a lease at inception through a formal process that evaluates our right to control the use of an identified asset for a period of time in exchange for consideration. We account for the lease and non-lease components of our building leases separately and have elected to use the available practical expedient to account for the lease and non-lease components of our equipment leases as a single component. All of our leases are classified as operating. For each operating lease, we calculate a lease liability at commencement date based on the present value of lease payments over the lease term and a corresponding ROU asset, adjusted for lease incentives. We do not recognize right-of-use assets and lease liabilities that arise from short-term leases for any class of underlying asset. We consider the likelihood of renewal in determining the lease terms for the calculation of the ROU asset and lease liability. As most of our leases do not provide an implicit rate of interest, we use our incremental borrowing rate based on the information available at commencement date in determining the present value of lease payments. We use the implicit rate of interest when readily determinable. Operating lease cost is calculated on a straight-line basis over the lease term and is included in other expenses in our consolidated statements of income. We amortize the ROU asset over the lease term on a pattern determined by the difference between the straight-line lease liability expense and the accretion of the imputed interest calculated on the lease liability. See Note 15.
Separation of Lease and Nonlease Components	We account for the lease and non-lease components of our building leases separately and have elected to use the available practical expedient to account for the lease and non-lease components of our equipment leases as a single component.
Short-term Leases	We do not recognize right-of-use assets and lease liabilities that arise from short-term leases for any class of underlying asset.
Treasury Stock and Retirement of Common Stock	Treasury Stock and Retirement of Common Stock : Treasury stock is reflected as a reduction of stockholders' equity at cost. When shares are retired, the par value is removed from common stock, and the excess of the repurchase price over par is allocated between additional paid-in capital and retained earnings. See Note 10.
Revenue Recognition	Revenue Recognition: Our non-interest sensitive life and accident and health products are long-duration contracts, and premium income is recognized as revenue when due from policyholders. If the contracts are experience rated, the estimated ultimate premium is recognized as revenue over the period of the contract. The estimated ultimate premium, which is revised to reflect current experience, is based on estimated claim costs, expenses, and profit margins. For interest sensitive products, the amounts collected from policyholders are considered deposits, and only the deductions during the period for cost of insurance, policy administration, and surrenders are included in revenue. Policyholders' funds represent funds deposited by contract holders and are not included in revenue.
Revenue from Service Fees	Fees from our leave management services and administrative-services only (ASO) business are reported as other income when services are rendered.
Reinsurance	Reinsurance : We routinely enter into reinsurance agreements with other insurance companies to spread risk and thereby limit losses from large exposures. For each of our reinsurance agreements, we determine if the agreement provides indemnification against loss or liability relating to insurance risk in accordance with applicable accounting standards. If we determine that a reinsurance agreement does not expose the reinsurer to a reasonable possibility of a significant loss from insurance risk, we record the agreement using the deposit method of accounting. Reinsurance activity is accounted for on a basis consistent with the terms of the reinsurance contracts and the accounting used for the original policies issued. Premium income and benefits and change in reserves for future benefits are presented in our consolidated statements of income net of reinsurance ceded. Ceded liabilities for policy and contract benefits, future policy and contract benefits, and unearned premiums are reported on a gross basis in our consolidated balance sheets, as are ceded policy loans. Our reinsurance recoverable includes the balances due from reinsurers under the terms of the reinsurance agreements for these ceded balances as well as settlement amounts currently due. Where applicable, gains or costs recognized on reinsurance transactions are generally deferred and amortized into earnings based upon expected future premium income for non-interest sensitive insurance policies and estimated future gross profits for interest sensitive insurance policies. Gains or costs recognized on reinsurance transactions for non-interest sensitive products for which we no longer receive premiums are generally deferred and amortized into earnings based upon expected claim reserve patterns. The cost of reinsurance included in other assets in our consolidated balance sheet at December 31, 2020 was $813.0 million. The deferred gain on reinsurance included in other liabilities in our consolidated balance sheets at December 31, 2020 and December 31, 2019 was $5.6 million and $8.5 million, respectively. Under ceded reinsurance agreements wherein we are not relieved of our legal liability to our policyholders, if the assuming reinsurer is unable to meet its obligations, we remain contingently liable. We evaluate the financial condition of reinsurers and monitor concentration of credit risk to minimize this exposure. We may also require assets in trust, letters of credit, or other acceptable collateral to support our reinsurance recoverable balances. We estimate an allowance for expected credit losses for our reinsurance recoverable balance using a probability of default approach which incorporates key inputs and assumptions regarding historical insurer liquidation rates, counterparty credit ratings, and collateral received. Liquidation rates are derived from rating agency studies covering domestic insurers and are based on historical liquidation trends according to their respective credit ratings. When calculating our allowance, we apply these liquidation rates to the net amount of our credit exposure, which considers collateral arrangements such as letters of credit and trust accounts. We evaluate the factors used to determine our allowance on a quarterly basis to consider material changes in our assumptions and make adjustments accordingly. At January 1, 2020 and December 31, 2020, the allowance for expected credit losses on reinsurance recoverables was $1.8 million and $11.7 million, respectively. The allowance increased $9.9 million during the year ended December 31, 2020, primarily due to an increase in the reinsurance recoverable balance, changes in certain counterparty credit ratings, and changes in our assumptions about the recoverability of receivables from certain counterparties. See Note 12.
Premium Tax Expense	Premium Tax Expense : Premium tax expense is included in other expenses in the consolidated statements of income. For the years ended December 31, 2020, 2019, and 2018, premium tax expense was $175.5 million, $170.1 million, and $155.8 million, respectively.
Stock-Based Compensation	Stock-Based Compensation : The cost of stock-based compensation is generally measured based on the grant-date fair value of the award. The Black-Scholes options valuation model is used for estimating the fair value of stock options, and the Monte-Carlo valuation model is used for estimating the fair value of performance units. Restricted stock units and stock success units are valued based on the fair value of common stock at the grant date. Stock-based awards are expensed over the requisite service period, or for performance units over the requisite service period, or remaining service period, if and when it becomes probable that the performance conditions will be satisfied, with an offsetting increase to additional paid-in capital in stockholders' equity. Forfeitures of stock-based awards are recognized as they occur. See Note 11.
Earnings Per Share	Earnings Per Share : We compute basic earnings per share by dividing net income by the weighted average number of common shares outstanding for the period. Earnings per share assuming dilution is computed by dividing net income by the weighted average number of shares outstanding for the period plus the shares representing the dilutive effect of stock-based awards. In computing earnings per share assuming dilution, only potential common shares resulting from stock-based awards that are dilutive (those that reduce earnings per share) are included. We use the treasury stock method to account for the effect of outstanding stock options and nonvested stock awards on the computation of earnings per share assuming dilution. See Note 10.
Translation of Foreign Curency	Translation of Foreign Currency : Revenues and expenses of our foreign operations are translated at average exchange rates. Assets and liabilities are translated at the rate of exchange on the balance sheet dates. The translation gain or loss is generally reported in accumulated other comprehensive income, net of income tax. We do not provide for deferred taxes to the extent unremitted foreign earnings are deemed permanently invested.
Accounting for Participating Individual Life Insurance	Accounting for Participating Individual Life Insurance : Participating policies issued by one of our subsidiaries prior to its 1986 conversion from a mutual to a stock life insurance company will remain participating as long as the policies remain in-force. A Participation Fund Account (PFA) was established for the benefit of all such individual participating life and annuity policies and contracts. The assets of the PFA provide for the benefit, dividend, and certain expense obligations of the participating individual life insurance policies and annuity contracts. The assets of the PFA were $319.8 million and $311.2 million at December 31, 2020 and 2019, respectively.
Accounting Updates Outstanding	Accounting Updates Outstanding: ASC Description Date of Adoption Effect on Financial Statements ASC 740 "Income Taxes" The amendments in this update simplify 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 simplify 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 will not have a material effect on our financial position or results of operations. 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 by reference rate reform 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 Description Date of Adoption Effect on Financial Statements 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.

Significant Accounting Polici_2

Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
New Accounting Pronouncements and Changes in Accounting Principles	Accounting Updates Adopted in 2020: Accounting Standards Codification (ASC) Description Date of Adoption Effect on Financial Statements ASC 350 "Intangibles - Goodwill and Other" This update eliminated the requirement to calculate the implied fair value of goodwill (the second step in the current two-step test) to measure a goodwill impairment charge. Instead, entities should perform the goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount and recognize an impairment charge for the excess of the carrying amount over the fair value, with the loss not to exceed the total amount of goodwill allocated to that reporting unit. This guidance was applied in the period of adoption. January 1, 2020 The adoption of this update did not have an effect on our financial position or results of operations. ASC 820 "Fair Value Measurement" This update amended the fair value measurement guidance by removing or clarifying certain existing disclosure requirements, while also adding new disclosure requirements. Specifically, this update removed certain disclosures related to Level 1 and Level 2 transfers and removed the discussion regarding valuation processes of Level 3 fair value measurements. The update modified guidance related to investments in certain entities that calculate net asset value to explicitly require disclosure regarding timing of liquidation of the investee's assets and timing of redemption restrictions. The update added disclosures around the changes in unrealized gains and losses in other comprehensive income for recurring Level 3 investments held at the end of the reporting period and adds disclosures regarding certain unobservable inputs on Level 3 fair value measurements. The guidance was applied both retrospectively and prospectively, depending on the specific requirement of the update. December 31, 2018 for the removal and modification of certain disclosures and January 1, 2020 for the addition of certain disclosures. The adoption of this update modified our disclosures but did not have an impact on our financial position or results of operations. ASC 715 "Compensation - Retirement Benefits" This update amends the defined benefit pension and other postretirement benefit guidance by removing or clarifying certain existing disclosure requirements, while also adding new disclosure requirements. Specifically, this update removes the requirement to disclose the effects of a one-percentage point change in the assumed healthcare cost trend and the requirement to disclose amounts in accumulated other comprehensive income expected to be recognized as part of net periodic benefit cost of the next year. This update adds a requirement to describe the reasons for significant gains and losses related to changes in the benefit obligation for the period. The update also clarifies that the projected benefit obligation (PBO) and accumulated benefit obligation (ABO) and fair value of plan assets are to be disclosed for plans with PBOs or ABOs in excess of plan assets. The guidance is to be applied retrospectively and early adoption is permitted. December 31, 2020 The adoption of this update modified our disclosures but did not have an impact on our financial position or results of operations. Accounting Standards Codification (ASC) Description Date of Adoption Effect on Financial Statements ASC 326 "Financial Instruments - Credit Losses" This update 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. Additional disclosures are also required, including information used to develop the allowance for losses. The guidance was applied using a modified retrospective approach through a cumulative-effect adjustment to retained earnings 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. This guidance was applied in the period of adoption. January 1, 2020 See the summary table below for the financial statement impacts of this adoption on our financial statement line items at January 1, 2020. In addition, see Note 3 of the "Notes to Consolidated Financial Statements" contained herein in this Item 1 for the additional disclosures required by the update. Summary of Financial Statement Impacts of Accounting Updates Adopted in 2020: Balance at December 31, 2019 Balance at Effect of Change (in millions of dollars) Adjustments due to ASC 326 Consolidated Balance Sheets Assets Mortgage Loans $ 2,397.0 $ 2,388.7 $ (8.3) Reinsurance Recoverable 4,780.7 4,778.9 (1.8) Accounts and Premiums Receivable 1,602.9 1,589.4 (13.5) Liabilities Deferred Income Tax 95.4 90.4 (5.0) Other Liabilities 1,856.5 1,856.8 0.3 Stockholders' Equity Retained Earnings 10,728.7 10,709.8 (18.9) Accounting Updates Adopted in 2019: Accounting Standards Codification (ASC) Description Date of Adoption Effect on Financial Statements ASC 220 "Income Statement - Reporting Comprehensive Income" This update allowed entities to make an accounting policy election to reclassify the disproportionate tax effects arising as a result of the recognition of the enactment of the tax bill, H.R.1, An Act to Provide Reconciliation Pursuant to Titles II and V of the Concurrent Resolution on the Budget for Fiscal Year 2018, more commonly known as TCJA, from accumulated other comprehensive income to retained earnings. Tax effects that are disproportionate in accumulated other comprehensive income for reasons other than the TCJA may not be reclassified. This update required additional disclosures on whether an entity elects to reclassify the disproportionate tax effects and its policy for releasing tax effects from accumulated other comprehensive income. January 1, 2019 The adoption of this update expanded certain of our disclosures but had no impact on our financial position or results of operations because we did not make the optional accounting policy election to reclassify the disproportionate tax effects resulting from the TCJA from accumulated other comprehensive income to retained earnings. ASC 310 "Receivables - Nonrefundable Fees and Other Costs" This update shortened the amortization period to the earliest call date for certain callable debt securities held at a premium. This update did not impact securities held at a discount. January 1, 2019 The adoption of this update did not have a material impact on our financial position or results of operations. ASC 718 "Compensation - Stock Compensation" This update generally aligned the accounting guidance for share-based payments issued to non-employees with guidance for share-based payments issued to employees. Specifically, the update required non-employee share-based payments to be measured using the grant date fair value of the equity instruments that an entity is obligated to issue when the good has been delivered or the service has been rendered rather than being remeasured through the performance completion date. Additionally, for non-employee share-based payments that contain performance conditions, the update changed the criteria regarding the recognition of compensation cost to when achievement of a performance condition is probable rather than upon actual achievement of the performance condition. January 1, 2019 The adoption of this update did not have an impact on our financial position or results of operations. ASC 842 "Leases" This update changed the accounting for leases, requiring lessees to report most leases on their balance sheets, regardless of whether the lease is classified as a finance lease or an operating lease. For lessees, the initial lease liability is equal to the present value of lease payments, and a corresponding asset, adjusted for certain items, is also recorded. Expense recognition for lessees remained similar to previous accounting requirements for capital and operating leases. For lessors, the guidance modified the classification criteria and the accounting for sales-type and direct financing leases. The guidance was applied using a modified retrospective approach through a cumulative-effect adjustment to retained earnings at the beginning of the period of adoption. In addition, the package of practical expedients available to leases that commenced prior to the date of adoption was applied. January 1, 2019 The adoption of this update resulted in the recognition of a lease liability of $122.0 million, with a corresponding right-of-use asset of $117.7 million, less an immaterial cumulative-effect decrease to retained earnings of $3.4 million related to our operating leases. There were also immaterial impacts to deferred income tax and income tax payable. This update did not have an impact on our results of operations, but it expanded our disclosures. Accounting Updates Adopted in 2018: ASC Description Date of Adoption Effect on Financial Statements ASC 230 "Statement of Cash Flows" This update provided clarifying guidance intended to reduce the diversity in practice in how certain cash receipts and cash payments are presented and classified in the statement of cash flows. The update addressed eight specific cash flow issues that relate to various types of transactions. The guidance was applied retrospectively. January 1, 2018 The adoption of this update resulted in the reclassification of certain cash inflows between investing activities and operating activities within our consolidated statements of cash flows. The reclassification primarily related to cash distributions from equity method investees and the bifurcation of those distributions as either returns on investment or returns of investment which resulted in a reclassification of cash inflows from investing activities to operating activities. The remaining portion of the reclassification related to the receipt of proceeds from corporate-owned life insurance benefits which resulted in a reclassification of cash inflows from operating activities to investing activities. The adoption of this update had no effect on our financial position or results of operations. ASC 606 "Revenue from Contracts with Customers" These updates superseded virtually all existing guidance regarding the recognition of revenue from customers. Specifically excluded from the scope of these updates are insurance contracts, although our fee-based service products are included within the scope. Our fee-based service products, which are primarily sold in our Unum US segment, are reported in other income within our consolidated statements of income and represent less than one percent of our total revenue. The core principle of this guidance is that revenue recognition should depict the transfer of goods or services to customers in an amount that reflects the consideration to which an entity expects to be entitled in exchange for those goods or services. Accordingly, we continue to recognize revenue for these fee-based service products as services are rendered. January 1, 2018 The adoption of these updates did not have an impact on our financial position or results of operations and did not result in expanded disclosures due to the immaterial nature of our fee-based service products relative to our overall business. ASC Description Date of Adoption Effect on Financial Statements ASC 715 "Compensation - Retirement Benefits" This update required the service cost component of net periodic pension and postretirement benefit costs to be included as a component of compensation costs in an entity's statement of income. Other components of net periodic pension and postretirement benefit costs are required to be presented separately from the service cost along with a disclosure identifying the line items in which these costs are presented in the statement of income. The amendments in this update were applied retrospectively or prospectively depending on the specific requirement of the update. January 1, 2018 The adoption of this update resulted in the reclassification of service cost from the other expenses line item to the compensation expense line item on our consolidated statements of income but had no effect on our financial position or results of operations. We elected to use the practical expedient for the retrospective application of this update. ASC 740 "Income Taxes" This update eliminated the exception that required the tax effect of intra-entity asset transfers other than inventory to be deferred until the transferred asset is sold to a third party or otherwise recovered through use. It required recognition of tax expense from the sale of the asset in the seller’s tax jurisdiction when the transfer occurs, even though the pre-tax effects of that transaction are eliminated in consolidation. January 1, 2018 The adoption of this update did not have an impact on our financial position or results of operations. ASC 815 "Derivatives and Hedge Accounting" This update provided targeted improvements to accounting for hedging activities for both nonfinancial and financial risk components, aligns the recognition and presentation of the effects of the hedging instrument and the hedged item in the financial statements, eases certain documentation and effectiveness assessment requirements, and enhances transparency through expanded disclosures. The amended presentation and disclosure guidance was adopted prospectively. Early adoption was permitted. January 1, 2018 We elected to early adopt this update. The adoption of this update did not have an impact on our financial position or results of operations; however, it expanded our disclosures. This update also simplified hedge documentation requirements and expanded available hedging strategies. ASC 825 "Financial Instruments - Overall" This update changed the accounting and disclosure requirements for certain financial instruments. These changes include a requirement to measure equity investments, other than those that result in consolidation or are accounted for under the equity method, at fair value through net income unless the investment qualifies for certain practicability exceptions. In addition, the update clarified guidance related to the valuation allowance assessment when recognizing deferred tax assets resulting from unrealized losses on available-for-sale fixed maturity securities. Changes also included the modification of certain disclosures around the fair value of financial instruments, including the requirement for separate presentation of financial assets and liabilities by measurement category, as well as the elimination of certain disclosures around methods and significant assumptions used to estimate fair value. The guidance was applied using a modified retrospective approach through a cumulative-effect adjustment to accumulated other comprehensive income with a corresponding adjustment to retained earnings as of the beginning of the fiscal year of adoption. January 1, 2018 The adoption of this update resulted in a cumulative-effect reduction to accumulated other comprehensive income of $17.5 million with a corresponding increase to retained earnings of $14.5 million, a decrease to other long-term investments of $3.8 million, and a decrease to deferred income tax liability of $0.8 million.

Fair Values of Financial Inst_2

Fair Values of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2020
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: 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 December 31, 2019 Investment Category Fair Value Redemption Term / Redemption Notice Unfunded Commitments (in millions of dollars) (in millions of dollars) Private Credit (a) $ 223.6 Not redeemable $ 152.6 39.6 Initial 2 year lock on each new investment / Quarterly after 2 year lock with 90 days notice 0.1 Total Private Credit 263.2 152.7 Private Equity (b) 149.3 Not redeemable 166.8 Real Assets (c) 173.8 Not redeemable 130.6 30.4 Quarterly / 90 days notice 25.0 Total Real Assets 204.2 155.6 Total Partnerships $ 616.7 $ 475.1 (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 December 31, 2020, the estimated remaining life of the investments that do not allow for redemptions is approximately 37 percent in the next 3 years, 38 percent during the period from 3 to 5 years, 22 percent during the period from 5 to 10 years, and 3 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 December 31, 2020, the estimated remaining life of the investments that do not allow for redemptions is approximately 20 percent in the next 3 years, 35 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 December 31, 2020, the estimated remaining life of the investments that do not allow for redemptions is approximately 12 percent in the next 3 years, 23 percent during period from 3 to 5 years, 64 percent during the period from 5 to 10 years, and 1 percent during the period from 10 to 15 years.
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: 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 December 31, 2019 Level 1 Level 2 Level 3 NAV Total (in millions of dollars) Assets Fixed Maturity Securities United States Government and Government Agencies and Authorities $ 412.8 $ 988.9 $ — $ — $ 1,401.7 States, Municipalities, and Political Subdivisions — 3,321.6 41.8 — 3,363.4 Foreign Governments — 995.9 21.8 — 1,017.7 Public Utilities 171.1 7,546.5 14.6 — 7,732.2 Mortgage/Asset-Backed Securities — 1,444.6 34.1 — 1,478.7 All Other Corporate Bonds 4,114.4 27,695.5 600.5 — 32,410.4 Redeemable Preferred Stocks — 39.6 — — 39.6 Total Fixed Maturity Securities 4,698.3 42,032.6 712.8 — 47,443.7 Other Long-term Investments Derivatives Foreign Exchange Contracts — 27.0 — — 27.0 Credit Default Swaps — 0.5 — — 0.5 Total Derivatives — 27.5 — — 27.5 Perpetual Preferred Equity Securities — 28.0 4.6 — 32.6 Private Equity Partnerships — — — 616.7 616.7 Total Other Long-term Investments — 55.5 4.6 616.7 676.8 Total Financial Instrument Assets Carried at Fair Value $ 4,698.3 $ 42,088.1 $ 717.4 $ 616.7 $ 48,120.5 Liabilities Other Liabilities Derivatives Interest Rate Swaps $ — $ 0.6 $ — $ — $ 0.6 Foreign Exchange Contracts — 34.0 — — 34.0 Embedded Derivative in Modified Coinsurance Arrangement — — 22.8 — 22.8 Total Derivatives — 34.6 22.8 — 57.4 Total Financial Instrument Liabilities Carried at Fair Value $ — $ 34.6 $ 22.8 $ — $ 57.4
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: Year Ended December 31, 2020 Fair Value Beginning Total Realized and Purchases Sales Level 3 Transfers Fair Value End of Change in Unrealized Earnings OCI 1 Into Out of OCI 1 Earnings (in millions of dollars) Fixed Maturity Securities States, Municipalities, and Political Subdivisions $ 41.8 $ — $ 2.2 $ — $ — $ — $ (28.5) $ 15.5 $ 1.7 $ — Foreign Governments 21.8 — — — — — — 21.8 — — Public Utilities 14.6 — 3.8 — — 175.9 (8.6) 185.7 3.7 — Mortgage/Asset-Backed Securities 34.1 — (3.0) — (67.9) 118.1 — 81.3 (3.5) — All Other Corporate Bonds 600.5 — 29.8 194.7 (36.1) 343.1 (188.9) 943.1 26.7 — Total Fixed Maturity Securities 712.8 — 32.8 194.7 (104.0) 637.1 (226.0) 1,247.4 28.6 — Perpetual Preferred Equity Securities 4.6 0.1 — — — — — 4.7 — 0.1 Embedded Derivative in Modified Coinsurance Arrangement (22.8) (17.0) — — — — — (39.8) — (17.0) 1 Other Comprehensive Income (Loss) Year Ended December 31, 2019 Total Realized and Fair Value Beginning Earnings Other Purchases Sales Level 3 Transfers Fair Value End of Into Out of (in millions of dollars) Fixed Maturity Securities States, Municipalities, and Political Subdivisions $ — $ — $ 2.8 $ 13.3 $ — $ 25.7 $ — $ 41.8 Foreign Governments 31.4 — 0.6 — (10.2) — — 21.8 Public Utilities 84.7 — 0.8 — — 6.0 (76.9) 14.6 Mortgage/Asset-Backed Securities — — (2.7) — — 36.8 — 34.1 All Other Corporate Bonds 1,495.8 — (3.1) 93.0 (86.0) 190.6 (1,089.8) 600.5 Redeemable Preferred Stocks 21.1 — — — — — (21.1) — Total Fixed Maturity Securities 1,633.0 — (1.6) 106.3 (96.2) 259.1 (1,187.8) 712.8 Perpetual Preferred Equity Securities 4.6 — — — — — — 4.6 Embedded Derivative in Modified Coinsurance Arrangement (31.1) 8.3 — — — — — (22.8) 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.
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. 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 (b) 0.50% - 24.90% / 3.63% Perpetual Preferred Equity Securities 4.7 Market Approach Market Convention (c) Priced at Cost or Owner's Equity Embedded Derivative in Modified Coinsurance Arrangement (39.8) Discounted Cash Flows Projected Liability Cash Flows (d) Actuarial Assumptions December 31, 2019 Fair Value Valuation Method Unobservable Input Range/Weighted Average (in millions of dollars) Fixed Maturity Securities All Other Corporate Bonds - Private $ 119.2 Market Approach Lack of Marketability Volatility of Credit Market Convention (a) (b) (c) 4.56% - 4.56% / 4.56% 0.35% - 17.68% / 2.2% Priced at Par Perpetual Preferred Equity Securities 4.6 Market Approach Market Convention (c) Priced at Cost or Owner's Equity Embedded Derivative in Modified Coinsurance Arrangement (22.8) Discounted Cash Flows Projected Liability Cash Flows (d) Actuarial Assumptions (a) Represents basis point adjustments to apply a discount due to the illiquidity of an investment (b) Represents basis point adjustments for credit-specific factors (c) Represents a decision to price based on par value, cost, or owner's equity when limited data is available (d) 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: 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 Payable 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 December 31, 2019 Estimated Fair Value Level 1 Level 2 Level 3 Total Carrying Value (in millions of dollars) Assets Mortgage Loans $ — $ 2,556.3 $ — $ 2,556.3 $ 2,397.0 Policy Loans — — 3,911.4 3,911.4 3,779.5 Other Long-term Investments Miscellaneous Long-term Investments — 18.5 58.4 76.9 76.9 Total Financial Instrument Assets Not Carried at Fair Value $ — $ 2,574.8 $ 3,969.8 $ 6,544.6 $ 6,253.4 Liabilities Long-term Debt $ 1,712.8 $ 1,526.2 $ — $ 3,239.0 $ 2,926.9 Other Liabilities Unfunded Commitments — 1.9 — 1.9 1.9 Total Financial Instrument Liabilities Not Carried at Fair Value $ 1,712.8 $ 1,528.1 $ — $ 3,240.9 $ 2,928.8

Investments (Tables)

Investments (Tables)	12 Months Ended
	Dec. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Amortized Cost and Fair Values of Securities by Security Type	At December 31, 2020 and 2019, 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: 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 December 31, 2019 Amortized Gross Gross Fair (in millions of dollars) United States Government and Government Agencies and Authorities $ 1,246.1 $ 156.0 $ 0.4 $ 1,401.7 States, Municipalities, and Political Subdivisions 2,863.1 507.6 7.3 3,363.4 Foreign Governments 843.5 175.2 1.0 1,017.7 Public Utilities 6,436.7 1,303.7 8.2 7,732.2 Mortgage/Asset-Backed Securities 1,377.8 101.3 0.4 1,478.7 All Other Corporate Bonds 28,273.1 4,211.2 73.9 32,410.4 Redeemable Preferred Stocks 39.0 0.6 — 39.6 Total Fixed Maturity Securities $ 41,079.3 $ 6,455.6 $ 91.2 $ 47,443.7 1 Allowance for Credit Losses
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. 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 December 31, 2019 Less Than 12 Months 12 Months or Greater Fair Gross Fair Gross (in millions of dollars) United States Government and Government Agencies and Authorities $ 110.2 $ 0.4 $ — $ — States, Municipalities, and Political Subdivisions 331.0 7.3 0.3 — Foreign Governments 69.4 1.0 — — Public Utilities 168.3 2.6 37.0 5.6 Mortgage/Asset-Backed Securities 47.0 0.4 3.1 — All Other Corporate Bonds 579.1 29.1 379.8 44.8 Total Fixed Maturity Securities $ 1,305.0 $ 40.8 $ 420.2 $ 50.4
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. 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 December 31, 2019 Total Unrealized Gain Position Unrealized Loss Position Gross Gain Fair Value Gross Loss Fair Value (in millions of dollars) 1 year or less $ 821.5 $ 14.5 $ 832.6 $ 0.2 $ 3.2 Over 1 year through 5 years 6,286.2 456.5 6,423.4 41.7 277.6 Over 5 years through 10 years 13,570.8 1,688.3 14,881.3 14.6 363.2 Over 10 years 19,023.0 4,195.0 22,152.6 34.3 1,031.1 39,701.5 6,354.3 44,289.9 90.8 1,675.1 Mortgage/Asset-Backed Securities 1,377.8 101.3 1,428.6 0.4 50.1 Total Fixed Maturity Securities $ 41,079.3 $ 6,455.6 $ 45,718.5 $ 91.2 $ 1,725.2
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 December 31, 2020: Gross Unrealized Loss Fair Value Gross Unrealized Gain Amount Percent of Total Gross Unrealized Loss (in millions of dollars) Investment-Grade $ 40,637.2 $ 7,371.5 $ 18.1 32.4 % Below-Investment-Grade 3,500.1 282.0 37.8 67.6 Total Fixed Maturity Securities $ 44,137.3 $ 7,653.5 $ 55.9 100.0 %
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 December 31, 2020: Year Ended (in millions of dollars) Balance, beginning of period $ — Credit losses on securities for which credit losses were not previously recorded 44.5 Change in allowance due to change in intent to hold securities to maturity (37.7) Change in allowance on securities with allowance recorded in previous period — Balance, end of period $ 6.8
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: Year Ended December 31 2020 2019 2018 (in millions of dollars) Income Tax Credits $ 33.2 $ 37.8 $ 41.4 Amortization, Net of Tax (21.9) (25.2) (28.1) Income Tax Benefit $ 11.3 $ 12.6 $ 13.3
Mortgage Loans by Property Type and Geographic Region	The carrying amount of mortgage loans by property type and geographic region are presented below. December 31 2020 2019 (in millions of dollars) Carrying Percent of Carrying Percent of Amount Total Amount Total Property Type Apartment $ 638.0 26.2 % $ 608.8 25.4 % Industrial 654.0 26.9 623.6 26.0 Office 517.8 21.3 549.3 22.9 Retail 575.6 23.7 567.5 23.7 Other 46.7 1.9 47.8 2.0 Total $ 2,432.1 100.0 % $ 2,397.0 100.0 % Region New England $ 40.0 1.6 % $ 28.9 1.2 % Mid-Atlantic 202.5 8.2 184.5 7.7 East North Central 330.4 13.6 329.2 13.7 West North Central 196.1 8.1 215.4 9.0 South Atlantic 512.0 21.1 509.2 21.2 East South Central 110.0 4.5 114.3 4.8 West South Central 257.4 10.6 246.6 10.3 Mountain 268.8 11.1 268.2 11.2 Pacific 514.9 21.2 500.7 20.9 Total $ 2,432.1 100.0 % $ 2,397.0 100.0 %
Schedule of Participating Mortgage Loans by Internal Credit Rating and Loan to Value	Mortgage loans, sorted by the applicable credit quality indicators, are as follows: December 31 2020 2019 (in millions of dollars) Carrying Amount Percent of Total Carrying Amount Percent of Total Internal Rating AA $ 3.5 0.1 % $ — — % A 510.0 21.0 % 485.6 20.3 % BBB 1,863.0 76.6 1,911.4 79.7 BB 39.4 1.6 — — B 16.2 0.7 — — Total $ 2,432.1 100.0 % $ 2,397.0 100.0 % Loan-to-Value Ratio <= 65% $ 1,189.4 48.9 % $ 1,215.1 50.7 % > 65% <= 75% 1,000.3 41.1 1,053.0 43.9 > 75% <= 85% 155.8 6.4 91.4 3.8 > 85% 86.6 3.6 37.5 1.6 Total $ 2,432.1 100.0 % $ 2,397.0 100.0 %
Mortgage Loans by Credit Quality Indicators	The following table presents the amortized cost of our mortgage loans by year of origination and credit quality indicators at December 31, 2020: Prior to 2016 2016 2017 2018 2019 2020 Total (in millions of dollars) Internal Rating AA $ 3.5 $ — $ — $ — $ — $ — $ 3.5 A 240.3 119.5 56.3 60.2 16.9 18.0 511.2 BBB 482.6 287.8 253.9 331.8 351.9 166.4 1,874.4 BB 29.4 — 10.5 — — — 39.9 B 16.2 — — — — — 16.2 Total Amortized Cost 772.0 407.3 320.7 392.0 368.8 184.4 2,445.2 Allowance for credit losses (2.4) (2.0) (1.9) (2.4) (2.9) (1.5) (13.1) Carrying Amount $ 769.6 $ 405.3 $ 318.8 $ 389.6 $ 365.9 $ 182.9 $ 2,432.1 Loan-to-Value Ratio <=65% $ 598.5 $ 257.5 $ 139.0 $ 77.8 $ 82.8 $ 37.2 $ 1,192.8 >65<=75% 47.2 122.5 109.9 294.8 286.0 147.2 1,007.6 >75%<=85% 78.7 27.3 37.9 13.3 — — 157.2 >85% 47.6 — 33.9 6.1 — — 87.6 Total Amortized Cost 772.0 407.3 320.7 392.0 368.8 184.4 2,445.2 Allowance for credit losses (2.4) (2.0) (1.9) (2.4) (2.9) (1.5) (13.1) Carrying Amount $ 769.6 $ 405.3 $ 318.8 $ 389.6 $ 365.9 $ 182.9 $ 2,432.1
Financing Receivable, Allowance for Credit Loss	The following table presents a rollforward of allowance for expected credit losses by loan-to-value ratio: Year Ended December 31, 2020 Beginning of Period Current Period Provisions Write-Offs Recoveries End of Period (in millions of dollars) Loan-to-Value Ratio <=65% $ 2.8 $ 0.6 $ — $ — $ 3.4 >65<=75% 4.6 2.7 — — 7.3 >75%<=85% 0.5 0.8 — — 1.3 >85% 0.4 0.7 — — 1.1 Total $ 8.3 $ 4.8 $ — $ — $ 13.1
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: December 31 2020 2019 Overnight and Continuous (in millions of dollars) Borrowings United States Government and Government Agencies and Authorities $ 0.1 $ — State, Municipalities, and Political Subdivisions 0.4 — Public Utilities 0.3 — All Other Corporate Bonds 16.8 — Total Borrowings $ 17.6 $ — Gross Amount of Recognized Liability for Securities Lending Transactions 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: December 31 2020 2019 (in millions of dollars) Carrying Value of FHLB Common Stock $ 28.2 $ 18.5 Advances from FHLB 312.2 — Carrying Value of Collateral Posted to FHLB Fixed Maturity Securities $ 944.0 $ 182.1 Commercial Mortgage Loans 1,072.5 164.4 Total Carrying Value of Collateral Posted to FHLB $ 2,016.5 $ 346.5
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. 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 December 31, 2019 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 $ 27.5 $ — $ 27.5 $ (4.0) $ (23.5) $ — Securities Lending 176.4 — 176.4 (176.4) — — Total $ 203.9 $ — $ 203.9 $ (180.4) $ (23.5) $ — Financial Liabilities: Derivatives $ 34.6 $ — $ 34.6 $ (31.3) $ — $ 3.3
Net Investment Income	Net Investment Income Net investment income reported in our consolidated statements of income is presented below. Certain prior period amounts have been reclassified to conform to the current period presentation. Year Ended December 31 2020 2019 2018 (in millions of dollars) Fixed Maturity Securities $ 2,164.0 $ 2,213.6 $ 2,239.7 Derivatives 78.7 73.4 66.1 Mortgage Loans 108.9 103.3 110.1 Policy Loans 20.0 19.9 18.6 Other Long-term Investments Perpetual Preferred Securities 1 (2.1) 5.4 (0.2) Private Equity Partnerships 2 19.8 31.7 36.0 Other 3.9 3.9 8.4 Short-term Investments 10.5 29.0 23.7 Gross Investment Income 2,403.7 2,480.2 2,502.4 Less Investment Expenses 30.6 32.1 35.2 Less Investment Income on Participation Fund Account Assets 12.4 12.8 13.5 Net Investment Income $ 2,360.7 $ 2,435.3 $ 2,453.7 1 The net unrealized gain (loss) recognized in net investment income for the year ended December 31, 2020 related to perpetual preferred securities still held at December 31, 2020 was $(4.6) million. The net unrealized gain (loss) recognized in net investment income for the year ended December 31, 2019 related to perpetual preferred securities still held at December 31, 2019 was $3.3 million. 2 The net unrealized gain (loss) recognized in net investment income for the year ended December 31, 2020 related to private equity partnerships still held at December 31, 2020 was $(8.7) million. The net unrealized gain (loss) recognized in net investment income for the year ended December 31, 2019 related to private equity partnerships still held at December 31, 2019 was $6.8 million. See Note 2 for further discussion of private equity partnerships.
Realized Investment Gains and Losses Reported in Consolidated Statements of Income	Realized Investment Gain and Loss Realized investment gains and losses are as follows: Year Ended December 31 2020 2019 2018 (in millions of dollars) Fixed Maturity Securities Gross Gains on Sales 1 $ 1,332.8 $ 22.9 $ 9.7 Gross Losses on Sales (20.3) (32.6) (15.2) Credit Losses (53.6) (25.3) (17.5) Mortgage Loans and Other Invested Assets Gross Gains on Sales 1.9 4.6 0.5 Gross Losses on Sales (0.3) (0.3) — Impairment Loss (36.6) — (1.4) Credit Losses (4.6) — — Embedded Derivative in Modified Coinsurance Arrangement (17.0) 8.3 (15.2) All Other Derivatives (2.5) (0.1) 0.3 Foreign Currency Transactions (0.7) (0.7) (0.7) Net Realized Investment Gain (Loss) $ 1,199.1 $ (23.2) $ (39.5) 1 Gross gains on sales of fixed maturity securities includes gains of $1,302.3 million as a result of the reinsurance transaction that we entered into during the fourth quarter of 2020. See Note 12 for further discussion.

Derivative Financial Instrume_2

Derivative Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2020
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. December 31 2020 2019 (in millions of dollars) Carrying Value of Collateral Received from Counterparties Cash $ 8.7 $ 24.0 Carrying Value of Collateral Posted to Counterparties Fixed Maturity Securities $ 54.0 $ 28.6
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 Receive Credit Default Forwards Total (in millions of dollars) Balance at December 31, 2017 $ 48.0 $ 536.5 $ 250.0 $ 70.0 $ — $ 904.5 Additions — 78.1 — 11.0 47.4 136.5 Terminations 48.0 76.4 — 70.0 47.4 241.8 Balance at December 31, 2018 — 538.2 250.0 11.0 — 799.2 Additions — 171.3 — — 382.4 553.7 Terminations — 98.4 — — 373.1 471.5 Foreign Currency — — — 0.4 (0.4) — Balance at December 31, 2019 — 611.1 250.0 11.4 8.9 881.4 Additions — 113.6 — — 6.4 120.0 Terminations — 3.9 250.0 — 3.4 257.3 Foreign Currency — — — 0.3 — 0.3 Balance at December 31, 2020 $ — $ 720.8 $ — $ 11.7 $ 11.9 $ 744.4
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 liabilities and the related cumulative basis adjustments related to our fair value hedges: Carrying Amount of Hedged Assets (Liabilities) Cumulative Amount of Fair Value Hedging Adjustment Included in the Carrying Amount of the Hedged Assets (Liabilities) December 31, 2020 December 31, 2019 December 31, 2020 December 31, 2019 (in millions of dollars) Fixed maturity securities: Receive fixed functional currency interest, pay fixed foreign currency interest $ 404.5 $ 239.4 $ 24.4 $ 1.1 Long-term Debt $ — $ (249.2) $ — $ 0.6
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. 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 December 31, 2019 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 $ 19.4 Other Liabilities $ 6.6 Fair Value Hedges Interest Rate Swaps Other L-T Investments — Other Liabilities 0.6 Foreign Exchange Contracts Other L-T Investments 7.6 Other Liabilities 5.0 Total Fair Value Hedges 7.6 5.6 Total Designated as Hedging Instruments $ 27.0 $ 12.2 Not Designated as Hedging Instruments Credit Default Swaps Other L-T Investments $ 0.5 Other Liabilities $ — Foreign Exchange Contracts Other L-T Investments — Other Liabilities 22.4 Embedded Derivative in Modified Coinsurance Arrangement Other L-T Investments — Other Liabilities 22.8 Total Not Designated as Hedging Instruments $ 0.5 $ 45.2
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. Year Ended December 31, 2020 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 $ 2,360.7 $ 1,199.1 $ 188.2 Gain (Loss) on Cash Flow Hedging Relationships Interest Rate Swaps: Hedged items 286.1 397.7 29.2 Derivatives Designated as Hedging Instruments 75.9 32.0 1.7 Foreign Exchange Contracts: Hedged items 12.1 (0.1) — Derivatives Designated as Hedging Instruments 2.5 0.1 — Gain (Loss) on Fair Value Hedging Relationships Interest Rate Swaps: Hedged items — (0.6) 10.1 Derivatives Designated as Hedging Instruments — 0.6 (0.9) Foreign Exchange Contracts Hedged items 7.1 23.3 — Derivatives Designated as Hedging Instruments 2.8 (23.3) — Year Ended December 31, 2019 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 $ 2,435.3 $ (23.2) $ 177.4 Gain (Loss) on Cash Flow Hedging Relationships Interest Rate Swaps: Hedged items 294.6 (1.6) 30.4 Derivatives Designated as Hedging Instruments 74.3 9.3 2.4 Foreign Exchange Contracts: Hedged items 14.8 1.4 — Derivatives Designated as Hedging Instruments (2.0) (1.4) — Gain (Loss) on Fair Value Hedging Relationships Interest Rate Swaps: Hedged items — (4.5) 14.3 Derivatives Designated as Hedging Instruments — 4.5 2.5 Foreign Exchange Contracts Hedged items 2.9 3.8 — Derivatives Designated as Hedging Instruments 1.9 (3.8) — Year Ended December 31, 2018 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 $ 2,453.7 $ (39.5) $ 167.3 Gain (Loss) on Cash Flow Hedging Relationships Interest Rate Swaps: Hedged items 310.3 0.1 38.4 Derivatives Designated as Hedging Instruments 67.1 (0.3) 2.3 Foreign Exchange Contracts: Hedged items 18.1 1.5 — Derivatives Designated as Hedging Instruments (0.9) (1.5) — Gain (Loss) on Fair Value Hedging Relationships Interest Rate Swaps: Hedged items 1.0 0.1 14.3 Derivatives Designated as Hedging Instruments (0.5) (0.1) 1.8 Foreign Exchange Contracts Hedged items 0.6 (2.7) — Derivatives Designated as Hedging Instruments 0.5 2.7 —
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). Year Ended December 31 2020 2019 2018 (in millions of dollars) Gain (Loss) Recognized in Other Comprehensive Income (Loss) on Derivatives Interest Rate Swaps and Forwards $ — $ (0.1) $ (0.1) Foreign Exchange Contracts (5.4) (6.1) 16.9 Total $ (5.4) $ (6.2) $ 16.8
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. Year Ended December 31 2020 2019 2018 (in millions of dollars) Net Realized Investment Gain (Loss) Credit Default Swaps $ (0.5) $ (0.1) $ (0.3) Interest Rate Swaps — — (0.3) Foreign Exchange Contracts (2.0) — 0.9 Embedded Derivative in Modified Coinsurance Arrangement (17.0) 8.3 (15.2) Total $ (19.5) $ 8.2 $ (14.9)

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Income (Tables)	12 Months Ended
	Dec. 31, 2020
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 (Loss) on Securities Net Gain on Hedges Foreign Currency Translation Adjustment Unrecognized Pension and Postretirement Benefit Costs Total (in millions of dollars) Balances at December 31, 2017 $ 607.8 $ 282.3 $ (254.5) $ (508.1) $ 127.5 Adjustment to Adopt Accounting Standard Update - Note 1 (17.5) — — — (17.5) Other Comprehensive Income (Loss) Before Reclassifications (920.3) 16.8 (50.7) 43.6 (910.6) Amounts Reclassified from Accumulated Other Comprehensive Income or Loss 17.6 (48.5) — 17.3 (13.6) Net Other Comprehensive Income (Loss) (902.7) (31.7) (50.7) 60.9 (924.2) Balances at December 31, 2018 (312.4) 250.6 (305.2) (447.2) (814.2) Other Comprehensive Income (Loss) Before Reclassifications 894.1 (0.2) 23.6 (52.0) 865.5 Amounts Reclassified from Accumulated Other Comprehensive Income or Loss 34.2 (62.6) — 14.4 (14.0) Net Other Comprehensive Income (Loss) 928.3 (62.8) 23.6 (37.6) 851.5 Balances at December 31, 2019 615.9 187.8 (281.6) (484.8) 37.3 Other Comprehensive Income (Loss) Before Reclassifications 405.6 (5.7) 20.3 (60.8) 359.4 Amounts Reclassified from Accumulated Other Comprehensive Income or Loss 46.2 (84.3) — 15.6 (22.5) Net Other Comprehensive Income (Loss) 451.8 (90.0) 20.3 (45.2) 336.9 Balances at December 31, 2020 $ 1,067.7 $ 97.8 $ (261.3) $ (530.0) $ 374.2
Schedule of Components of Unrealized Gain on Securities	The net unrealized gain (loss) on securities consists of the following components: December 31 January 1 December 31 Change for the Year Ended December 31 2020 2019 2018 2018 2017 2020 2019 2018 (in millions of dollars) Fixed Maturity Securities $ 7,597.6 $ 6,364.4 $ 2,736.5 $ 5,665.2 $ 5,677.3 $ 1,233.2 $ 3,627.9 $ (2,928.7) Other Investments — — — — 14.4 — — — Deferred Acquisition Costs (85.1) (62.7) (27.9) (51.4) (51.4) (22.4) (34.8) 23.5 Reserves for Future Policy and Contract Benefits (6,225.6) (5,803.1) (3,220.3) (5,094.7) (5,094.7) (422.5) (2,582.8) 1,874.4 Reinsurance Recoverable 200.2 424.7 261.4 375.8 375.8 (224.5) 163.3 (114.4) Income Tax (419.4) (307.4) (62.1) (304.6) (313.6) (112.0) (245.3) 242.5 Total $ 1,067.7 $ 615.9 $ (312.4) $ 590.3 $ 607.8 $ 451.8 $ 928.3 $ (902.7)
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: Year Ended December 31 2020 2019 2018 (in millions of dollars) Net Unrealized Gain (Loss) on Securities Net Realized Investment Gain (Loss) Gain (Loss) on Sales on Securities $ 1,279.7 $ (18.0) $ (4.8) Credit Losses on Fixed Maturity Securities (53.6) (25.3) (17.5) Loss on Benefits and Change in Reserves for Future Benefits (1,284.5) — — (58.4) (43.3) (22.3) Income Tax Benefit (12.2) (9.1) (4.7) Total $ (46.2) $ (34.2) $ (17.6) Net Gain on Hedges Net Investment Income Gain on Interest Rate Swaps and Forwards $ 74.1 $ 73.6 $ 65.9 Gain (Loss) on Foreign Exchange Contracts 2.0 0.8 (1.1) Net Realized Investment Gain (Loss) Gain on Interest Rate Swaps 32.0 8.8 0.2 Gain (Loss) on Foreign Exchange Contracts 0.1 (1.3) (1.5) Interest and Debt Expense Loss on Interest Rate Swaps (1.5) (2.1) (2.1) Loss on Forward — (0.5) — 106.7 79.3 61.4 Income Tax Expense 22.4 16.7 12.9 Total $ 84.3 $ 62.6 $ 48.5 Unrecognized Pension and Postretirement Benefit Costs Other Expenses Amortization of Net Actuarial Loss $ (19.8) $ (18.6) $ (22.3) Amortization of Prior Service Credit 0.1 0.2 0.2 Curtailment Gain (0.1) — — (19.8) (18.4) (22.1) Income Tax Benefit (4.2) (4.0) (4.8) Total $ (15.6) $ (14.4) $ (17.3)

Liability for Unpaid Claims a_2

Liability for Unpaid Claims and Claim Adjustment Expenses (Tables)	12 Months Ended
	Dec. 31, 2020
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: 2020 2019 2018 (in millions of dollars) Balance at January 1 $ 23,076.7 $ 23,149.0 $ 23,222.0 Less Reinsurance Recoverable 2,246.8 2,227.3 2,182.0 Net Balance at January 1 20,829.9 20,921.7 21,040.0 Incurred Related to Current Year 6,327.8 6,113.2 5,832.3 Prior Years Interest 997.8 1,036.5 1,049.8 All Other Incurred 878.7 (274.1) (106.2) Foreign Currency 65.9 76.0 (110.7) Total Incurred 8,270.2 6,951.6 6,665.2 Paid Related to Current Year (2,727.0) (2,532.4) (2,354.7) Prior Years (4,430.3) (4,511.0) (4,428.8) Total Paid (7,157.3) (7,043.4) (6,783.5) Reserves Ceded Pursuant to Reinsurance Transaction (6,141.5) — — Net Balance at December 31 15,801.3 20,829.9 20,921.7 Plus Reinsurance Recoverable 8,378.9 2,246.8 2,227.3 Balance at December 31 $ 24,180.2 $ 23,076.7 $ 23,149.0
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: December 31 2020 2019 2018 (in millions of dollars) Policy and Contract Benefits $ 1,855.4 $ 1,745.5 $ 1,695.7 Reserves for Future Policy and Contract Benefits 49,653.0 47,780.1 44,841.9 Total 51,508.4 49,525.6 46,537.6 Less: Life Reserves for Future Policy and Contract Benefits 8,371.7 8,435.7 8,330.9 Accident and Health Active Life Reserves 12,730.9 12,210.1 11,837.4 Adjustment Related to Unrealized Investment Gains and Losses 6,225.6 5,803.1 3,220.3 Liability for Unpaid Claims and Claim Adjustment Expenses $ 24,180.2 $ 23,076.7 $ 23,149.0

Income Tax (Tables)

Income Tax (Tables)	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Schedule of Components of Income Tax Expense (Benefit)	Total income tax expense (benefit) is allocated as follows: Year Ended December 31 2020 2019 2018 (in millions of dollars) Net Income $ 171.0 $ 281.8 $ 104.4 Stockholders' Equity - Accumulated Other Comprehensive Income (Loss) Change in Net Unrealized Gain on Securities Before Adjustment 250.2 757.0 (614.2) Change in Adjustment to Deferred Acquisition Costs and Reserves for Future Policy and Contract Benefits, Net of Reinsurance (138.2) (511.7) 371.7 Change in Net Gain on Hedges (23.8) (17.0) (8.2) Change in Foreign Currency Translation Adjustment (4.3) 0.2 (0.6) Change in Unrecognized Pension and Postretirement Benefit Costs (34.8) (9.3) 17.0 Total $ 220.1 $ 501.0 $ (129.9)
Schedule of Effective Income Tax Rate Reconciliation	A reconciliation of the income tax provision at the U.S. federal statutory rate to the income tax rate as reported in our consolidated statements of income is as follows: Year Ended December 31 2020 2019 2018 Statutory Income Tax 21.0 % 21.0 % 21.0 % Net Operating Loss Carryback (3.8) — — Deemed Repatriation Tax on Foreign Earnings and Profit — — 1.8 Tax Exempt Income (0.8) (0.5) (1.3) Tax Credits (1.3) (1.1) (2.4) Policyholder Reserves 0.7 — (2.4) Other Items, Net 1.9 1.0 (0.1) Effective Tax 17.7 % 20.4 % 16.6 %
Schedule of Deferred Tax Assets and Liabilities	Our net deferred tax asset (liability) consists of the following. Certain prior year amounts have been reclassified to conform to current year reporting. December 31 2020 2019 (in millions of dollars) Deferred Tax Asset Reserves $ 1,279.6 $ 1,154.6 Employee Benefits 218.7 201.6 Other 52.9 19.4 Gross Deferred Tax Asset 1,551.2 1,375.6 Less: Valuation Allowance 14.5 28.3 Net Deferred Tax Asset 1,536.7 1,347.3 Deferred Tax Liability Deferred Acquisition Costs 185.5 115.6 Fixed Assets 74.7 58.5 Invested Assets 1,443.5 1,213.7 Cost of Reinsurance 180.4 10.8 Other 68.7 44.1 Gross Deferred Tax Liability 1,952.8 1,442.7 Net Deferred Tax Asset (Liability) $ (416.1) $ (95.4)
Schedule of Income before Income Tax, Domestic and Foreign	Our consolidated statements of income include amounts subject to both domestic and foreign taxation. The income and related tax expense (benefit) are as follows: Year Ended December 31 2020 2019 2018 (in millions of dollars) Income Before Tax Domestic $ 924.7 $ 1,289.5 $ 492.6 Foreign 39.3 92.6 135.2 Total $ 964.0 $ 1,382.1 $ 627.8 Current Tax Expense (Benefit) Federal $ (98.4) $ 273.6 $ 194.6 State and Local 1.5 1.3 (0.6) Foreign (19.7) (0.1) 33.4 Total (116.6) 274.8 227.4 Deferred Tax Expense (Benefit) Federal 250.5 (9.5) (114.6) State and Local 1.0 (0.1) (0.2) Foreign 36.1 16.6 (8.2) Total 287.6 7.0 (123.0) Total Tax Expense $ 171.0 $ 281.8 $ 104.4
Summary of Positions for which Significant Change in Unrecognized Tax Benefits is Reasonably Possible	Our consolidated statements of income include the following changes in unrecognized tax benefits. December 31 2020 2019 2018 (in millions of dollars) Balance at Beginning of Year $ 241.0 $ 262.2 $ 1.4 Increases (Decreases) for Tax Positions Related to Prior Years (21.0) (21.1) 261.5 Lapse of the Applicable Statute of Limitations (0.3) (0.1) (0.7) Balance at End of Year 219.7 241.0 262.2 Less Tax Attributable to Temporary Items Included Above (105.9) (127.1) (148.2) Total Unrecognized Tax Benefits That if Recognized Would Affect the Effective Tax Rate $ 113.8 $ 113.9 $ 114.0

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Schedule of Debt	Debt consists of the following: December 31 2020 2019 Interest Rates Maturities (in millions of dollars) Long-term Debt Outstanding Principal Senior Secured Notes issued 2007 Variable 2037 $ — $ 80.0 Senior Notes issued 1998 6.750 - 7.250% 2028 335.8 335.8 Senior Notes issued 2002 7.375% 2032 39.5 39.5 Senior Notes issued 2012 and 2016 5.750% 2042 500.0 500.0 Senior Notes issued 2014 4.000% 2024 350.0 350.0 Senior Notes issued 2015 3.875% 2025 275.0 275.0 Senior Notes issued 2019 4.000% 2029 400.0 400.0 Senior Notes issued 2019 4.500% 2049 450.0 450.0 Senior Notes issued 2020 4.500% 2025 500.0 — Medium-term Notes issued 1990 - 1996 7.000 - 7.190% 2023 - 2028 20.5 20.5 Junior Subordinated Debt Securities issued 1998 7.405% 2038 203.7 203.7 Junior Subordinated Debt Securities issued 2018 6.250% 2058 300.0 300.0 Fair Value Hedge Adjustment — (0.6) Less: Unamortized Net Premium 6.0 8.4 Unamortized Debt Issuance Costs (34.8) (35.4) Total Long-term Debt 3,345.7 2,926.9 Short-term Debt Outstanding Principal Senior Notes issued 2010 5.625% 2020 — 400.0 Less Unamortized Debt Issuance Costs — (0.3) Total Short-term Debt — 399.7 Total Debt $ 3,345.7 $ 3,326.6

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2020
Defined Benefit Plans and Other Postretirement Benefit Plans
Schedule of Changes in Projected Benefit Obligations and Fair Value of Plan Assets	The following table provides the changes in the benefit obligation and fair value of plan assets and the funded status of the plans. Pension Benefits U.S. Plans U.K. Plan OPEB 2020 2019 2020 2019 2020 2019 (in millions of dollars) Change in Benefit Obligation Benefit Obligation at Beginning of Year $ 2,106.9 $ 1,933.3 $ 256.9 $ 211.0 $ 127.2 $ 125.9 Service Cost 11.0 10.9 — — — — Interest Cost 73.0 83.3 4.9 6.1 4.1 5.3 Plan Participant Contributions — — — — 0.1 0.2 Actuarial (Gain) Loss (1) 212.4 225.7 33.8 34.9 (0.3) 7.0 Benefits and Expenses Paid (126.1) (146.3) (5.1) (4.8) (10.6) (11.2) Curtailment Gain — — (0.7) — — — Change in Foreign Exchange Rates — — 10.2 9.7 — — Benefit Obligation at End of Year $ 2,277.2 $ 2,106.9 $ 300.0 $ 256.9 $ 120.5 $ 127.2 Accumulated Benefit Obligation at December 31 $ 2,277.2 $ 2,106.9 $ 297.5 $ 253.1 N/A N/A Change in Fair Value of Plan Assets Fair Value of Plan Assets at Beginning of Year $ 1,600.0 $ 1,454.9 $ 252.8 $ 217.0 $ 9.9 $ 10.1 Actual Return on Plan Assets 227.9 282.7 36.4 31.0 0.1 0.2 Employer Contributions 9.1 8.7 — — 9.8 10.6 Plan Participant Contributions — — — — 0.1 0.2 Benefits and Expenses Paid (126.1) (146.3) (5.1) (4.8) (10.6) (11.2) Change in Foreign Exchange Rates — — 10.0 9.6 — — Fair Value of Plan Assets at End of Year $ 1,710.9 $ 1,600.0 $ 294.1 $ 252.8 $ 9.3 $ 9.9 Underfunded Status $ 566.3 $ 506.9 $ 5.9 $ 4.1 $ 111.2 $ 117.3 (1) The actuarial losses recognized for the U.S. and U.K. pension plans were primarily driven by decreases in the discount rate assumption.
Schedule of Amounts Recognized in Balance Sheet	The amounts recognized in our consolidated balance sheets for our pension and OPEB plans at December 31, 2020 and 2019 are as follows. Pension Benefits U.S. Plans U.K. Plan OPEB 2020 2019 2020 2019 2020 2019 (in millions of dollars) Current Liability $ 8.0 $ 7.7 $ — $ — $ 1.5 $ 1.5 Noncurrent Liability 558.3 499.2 5.9 4.1 109.7 115.8 Noncurrent Asset — — — — — — Underfunded Status $ 566.3 $ 506.9 $ 5.9 $ 4.1 $ 111.2 $ 117.3 Unrecognized Pension and Postretirement Benefit Costs Net Actuarial Gain (Loss) $ (767.9) $ (695.4) $ (70.5) $ (63.1) $ 11.0 $ 11.1 Prior Service Credit (Cost) (0.6) (0.7) (0.2) (0.3) 2.9 3.1 (768.5) (696.1) (70.7) (63.4) 13.9 14.2 Income Tax 273.9 240.7 16.0 14.5 5.4 5.3 Total Included in Accumulated Other Comprehensive Income (Loss) $ (494.6) $ (455.4) $ (54.7) $ (48.9) $ 19.3 $ 19.5
Schedule of Amounts Recognized in Other Comprehensive Income (Loss)	The following table provides the changes recognized in other comprehensive income for the years ended December 31, 2020 and 2019. Pension Benefits U.S. Plans U.K. Plan OPEB 2020 2019 2020 2019 2020 2019 (in millions of dollars) Accumulated Other Comprehensive Income (Loss) at Beginning of Year $ (455.4) $ (437.3) $ (48.9) $ (37.3) $ 19.5 $ 27.4 Net Actuarial Gain (Loss) Amortization 18.7 20.2 1.1 0.9 — (2.5) All Other Changes (91.2) (43.0) (8.5) (15.1) (0.1) (7.3) Prior Service Credit (Cost) Amortization 0.1 — — — (0.2) (0.2) Curtailment Gain — — 0.1 — — — Change in Income Tax 33.2 4.7 1.5 2.6 0.1 2.1 Accumulated Other Comprehensive Income (Loss) at End of Year $ (494.6) $ (455.4) $ (54.7) $ (48.9) $ 19.3 $ 19.5
Schedule of Assumptions Used	We use a December 31 measurement date for each of our plans. The weighted average assumptions used in the measurement of our benefit obligations as of December 31 and our net periodic benefit costs for the years ended December 31 are as follows: Pension Benefits U.S. Plans U.K. Plan OPEB 2020 2019 2020 2019 2020 2019 Benefit Obligations Discount Rate 2.90 % 3.60 % 1.40 % 2.00 % 2.60 % 3.40 % Rate of Compensation Increase N/A N/A 2.80 % 2.90 % N/A N/A Net Periodic Benefit Cost Discount Rate 3.60 % 4.40 % 2.00 % 2.90 % 3.40 % 4.40 % Expected Return on Plan Assets 7.00 % 7.00 % 4.10 % 4.30 % 5.75 % 5.75 % Rate of Compensation Increase N/A N/A 2.90 % 3.70 % N/A N/A
Schedule of Net Benefit Costs	Net Periodic Benefit Cost The following table provides the components of the net periodic benefit cost (credit) for the years ended December 31. Pension Benefits U.S. Plans U.K. Plan OPEB 2020 2019 2018 2020 2019 2018 2020 2019 2018 (in millions of dollars) Service Cost $ 11.0 $ 10.9 $ 9.1 $ — $ — $ — $ — $ — $ — Interest Cost 73.0 83.3 79.8 4.9 6.1 5.9 4.1 5.3 4.9 Expected Return on Plan Assets (106.7) (99.4) (104.5) (9.5) (8.9) (8.9) (0.5) (0.6) (0.6) Amortization of: Net Actuarial Loss (Gain) 18.7 20.2 21.7 1.1 0.9 0.6 — (2.5) — Prior Service Credit 0.1 — — — — — (0.2) (0.2) (0.2) Curtailment Gain — — — 0.1 — — — — — Total Net Periodic Benefit Cost $ (3.9) $ 15.0 $ 6.1 $ (3.4) $ (1.9) $ (2.4) $ 3.4 $ 2.0 $ 4.1
Schedule of Expected Benefit Payments	The following table provides expected benefit payments, which reflect expected future service, as appropriate. Pension Benefits U.S. Plans U.K. Plan OPEB (in millions of dollars) Year Gross Subsidy Payments Net 2021 $ 75.0 $ 6.1 $ 11.1 $ 0.1 $ 11.0 2022 78.4 6.1 10.5 0.1 10.4 2023 82.2 6.5 10.0 0.1 9.9 2024 86.1 7.0 9.5 0.1 9.4 2025 90.1 7.2 9.0 0.1 8.9 2026-2030 514.9 42.3 38.3 0.2 38.1
Pension Plan | UNITED STATES
Defined Benefit Plans and Other Postretirement Benefit Plans
Defined Benefit Plan, Plan Assets, Category	The categorization of fair value measurements by input level for the invested assets in our U.S. pension plans is shown below. The carrying values of investment-related receivables and payables approximate fair value due to the short-term nature of the securities and are not included in the following chart. Investments valued using net asset value (NAV) as a practical expedient are not required to be categorized by input level, but these investments are included as follows to reconcile to total invested assets. December 31, 2020 Quoted Prices Significant Other Significant NAV as a Practical Total (in millions of dollars) Invested Assets Equity Securities: U.S. Large Cap $ — $ — $ — $ 112.6 $ 112.6 U.S. Small Cap 25.8 — — 33.2 59.0 Global — — — 307.9 307.9 International — — — 31.6 31.6 Emerging Markets — — — 62.3 62.3 Fixed Income Securities: U.S. Government and Agencies 227.8 — — — 227.8 Corporate — 445.6 — — 445.6 State and Municipal Securities — 3.7 — — 3.7 Opportunistic Credits — — — 200.4 200.4 Real Estate — — — 108.9 108.9 Alternative Investments: Private Equity Direct Investments — — — 62.1 62.1 Private Equity Funds of Funds — — — 39.2 39.2 Cash Equivalents 46.3 — — — 46.3 Total Invested Assets $ 299.9 $ 449.3 $ — $ 958.2 $ 1,707.4 December 31, 2019 Quoted Prices Significant Significant NAV as a Practical Total (in millions of dollars) Invested Assets Equity Securities: U.S. Large Cap $ — $ — $ — $ 95.2 $ 95.2 U.S. Small Cap 23.0 — — 24.8 47.8 Global — — — 299.1 299.1 International — — — 28.3 28.3 Emerging Markets — — — 50.4 50.4 Fixed Income Securities: U.S. Government and Agencies 199.0 — — — 199.0 Corporate — 391.1 — — 391.1 State and Municipal Securities — 2.5 — — 2.5 Opportunistic Credits — — — 196.5 196.5 Real Estate — — — 108.4 108.4 Alternative Investments: Private Equity Direct Investments — — — 57.7 57.7 Private Equity Funds of Funds — — — 38.4 38.4 Cash Equivalents 82.4 — — — 82.4 Total Invested Assets $ 304.4 $ 393.6 $ — $ 898.8 $ 1,596.8
Pension Plan | UNITED KINGDOM
Defined Benefit Plans and Other Postretirement Benefit Plans
Defined Benefit Plan, Plan Assets, Category	The categorization of fair value measurements by input level for the invested assets in our U.K. pension plan is shown below. Investments valued using NAV as a practical expedient are not required to be categorized by input level, but these investments are included as follows to reconcile to total invested assets. December 31, 2020 Quoted Prices Significant Significant NAV as a Practical Total (in millions of dollars) Plan Assets Diversified Growth Assets $ — $ — $ — $ 176.0 $ 176.0 Fixed Interest and Index-linked Securities 116.8 — — — 116.8 Cash Equivalents 1.3 — — — 1.3 Total Plan Assets $ 118.1 $ — $ — $ 176.0 $ 294.1 December 31, 2019 Quoted Prices Significant Significant NAV as a Practical Total (in millions of dollars) Plan Assets Diversified Growth Assets $ — $ — $ — $ 163.0 $ 163.0 Fixed Interest and Index-linked Securities 89.6 — — — 89.6 Cash Equivalents 0.2 — — — 0.2 Total Plan Assets $ 89.8 $ — $ — $ 163.0 $ 252.8
Other Postretirement Benefit Plans
Defined Benefit Plans and Other Postretirement Benefit Plans
Defined Benefit Plan, Plan Assets, Category	The categorization of fair value measurements by input level for the assets in our OPEB plan is as follows: December 31, 2020 Quoted Prices Significant Other Significant Total (in millions of dollars) Assets Life Insurance Contracts $ — $ — $ 9.3 $ 9.3 December 31, 2019 Quoted Prices Significant Other Significant Total (in millions of dollars) Assets Life Insurance Contracts $ — $ — $ 9.9 $ 9.9
Schedule of Effect of Significant Unobservable Inputs, Changes in Plan Assets	Changes in our OPEB plan assets measured at fair value on a recurring basis using significant unobservable inputs (Level 3) during the years ended December 31, 2020 and 2019 are as follows: Year Ended December 31, 2020 Beginning Actual Return on Plan Assets Contributions Net Benefits and Expenses Paid End of Year (in millions of dollars) Life Insurance Contracts $ 9.9 $ 0.1 $ 9.9 $ (10.6) $ 9.3 Year Ended December 31, 2019 Beginning Actual Return on Plan Assets Contributions Net Benefits and Expenses Paid End of Year (in millions of dollars) Life Insurance Contracts $ 10.1 $ 0.2 $ 10.8 $ (11.2) $ 9.9

Stockholders' Equity and Earn_2

Stockholders' Equity and Earnings Per Common Share (Tables)	12 Months Ended
	Dec. 31, 2020
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: Year Ended December 31 2020 2019 2018 (in millions of dollars, except share data) Numerator Net Income $ 793.0 $ 1,100.3 $ 523.4 Denominator (000s) Weighted Average Common Shares - Basic 203,642.0 209,728.9 219,635.6 Dilution for Assumed Exercises of Stock Options and Nonvested Stock Awards 113.3 125.5 423.0 Weighted Average Common Shares - Assuming Dilution 203,755.3 209,854.4 220,058.6 Net Income Per Common Share Basic $ 3.89 $ 5.25 $ 2.38 Assuming Dilution $ 3.89 $ 5.24 $ 2.38
Treasury Stock Transactions	During the second quarter of 2019, our board of directors authorized the repurchase of up to $750.0 million of Unum Group's outstanding common stock through November 23, 2020, at which point the authorization expired. This authorization replaced the previous authorization of $750.0 million that was scheduled to expire on November 24, 2019. As of December 31, 2020, we did not authorize a new share repurchase program and there were no remaining amounts to be repurchased under either plan at December 31, 2020. Common stock repurchases, which are accounted for using the cost method and classified as treasury stock until otherwise retired, were as follows: Year Ended December 31 2020 2019 2018 (in millions) Shares Repurchased — 12.3 8.7 Cost of Shares Repurchased (1) $ — $ 400.4 $ 350.7 (1) Includes commissions of $0.4 million and $0.7 million for the years ended December 31, 2019 and 2018, respectively.

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award
Schedule of Compensation Cost for Share-based Payment Arrangements	Compensation expense for the stock plans, as reported in our consolidated statements of income, is as follows: Year Ended December 31 2020 2019 2018 (in millions of dollars) Performance Share Units $ 5.6 $ 5.0 $ 6.8 Restricted Stock Units and Cash-Settled Restricted Stock Units 23.9 21.0 19.0 Stock Success Units 0.4 — — Other 0.5 0.6 0.5 Total Compensation Expense, Before Income Tax $ 30.4 $ 26.6 $ 26.3 Total Compensation Expense, Net of Income Tax $ 26.1 $ 22.7 $ 20.9
Stock Success Units (SSUs)
Share-based Compensation Arrangement by Share-based Payment Award
Schedule of SSU Activity	Stock Success Units (SSUs) Activity for SSUs classified as equity is as follows: Weighted Average Shares Grant Date (000s) Fair Value Outstanding at December 31, 2019 — $ — Granted 321 18.78 Outstanding at December 31, 2020 321 18.78
Performance Share Units
Share-based Compensation Arrangement by Share-based Payment Award
Activity for PSUs Classified as Equity	Activity for PSUs classified as equity is as follows: Weighted Average Shares Grant Date (000s) Fair Value Outstanding at December 31, 2019 337 $ 44.11 Granted 323 23.49 Vested (135) 48.20 Forfeited (8) 35.81 Outstanding at December 31, 2020 517 30.31
Valuation Assumptions on PSU Grants	The fair value of PSUs is estimated on the date of initial grant using the Monte-Carlo simulation m odel. Key assumptions used to value PSUs granted during the years shown are as follows: Year Ended December 31 2020 2019 2018 Expected Volatility (based on our and our peer group historical daily stock prices) 23 % 23 % 24 % Expected Life (equals the performance period) 3 years 3 years 3 years Risk Free Interest Rate (based on U.S. Treasury yields at the date of grant) 0.85 % 2.53 % 2.32 %
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award
Activity for Restricted Stock Units	Activity for RSUs classified as equity is as follows: Weighted Average Shares Grant Date (000s) Fair Value Outstanding at December 31, 2019 1,044 $ 41.06 Granted 1,262 22.71 Vested (626) 40.11 Forfeited (87) 28.75 Outstanding at December 31, 2020 1,593 27.57
Cash Settled RSUs
Share-based Compensation Arrangement by Share-based Payment Award
Share-based Payment Arrangement, Cash-Settled Restricted Stock Units, Activity	Activity for cash-settled RSUs classified as a liability is as follows: Weighted Average Shares Grant Date (000s) Fair Value Outstanding at December 31, 2019 — $ — Granted 68 22.94 Outstanding at December 31, 2020 68 22.94
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award
Schedule of Stock Option Activity	Stock option activity is summarized as follows: Remaining Intrinsic Shares Weighted Average Contractual Term Value (000s) Exercise Price (in years) (in millions) Outstanding at December 31, 2019 74 $ 24.09 Exercised (13) 23.35 Forfeited (21) 24.25 Outstanding at December 31, 2020 40 24.25 0.1 $ — Exercisable at December 31, 2020 40 $ 24.25 0.1 $ —

Reinsurance (Tables)

Reinsurance (Tables)	12 Months Ended
	Dec. 31, 2020
Reinsurance Disclosures [Abstract]
Effects of Reinsurance	Reinsurance activity related to both our premium income and changes in reserves for future benefits are as follows: Year Ended December 31 2020 2019 2018 (in millions of dollars) Direct Premium Income $ 9,621.9 $ 9,576.3 $ 9,171.1 Reinsurance Assumed 94.1 116.5 142.6 Reinsurance Ceded (337.9) (327.2) (327.6) Net Premium Income $ 9,378.1 $ 9,365.6 $ 8,986.1 Ceded Benefits and Change in Reserves for Future Benefits $ 628.8 $ 650.1 $ 667.2

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2020
Segment Reporting [Abstract]
Premium Income by Major Line of Business within Each Segment	Segment information is as follows: Year Ended December 31 2020 2019 2018 (in millions of dollars) Premium Income Unum US Group Disability Group Long-term Disability $ 1,828.5 $ 1,823.1 $ 1,766.2 Group Short-term Disability 799.2 768.8 706.3 Group Life and Accidental Death & Dismemberment Group Life 1,640.5 1,662.0 1,583.7 Accidental Death & Dismemberment 163.9 165.7 156.3 Supplemental and Voluntary Individual Disability 456.0 440.7 425.4 Voluntary Benefits 875.2 910.2 895.7 Dental and Vision 255.6 246.1 202.8 6,018.9 6,016.6 5,736.4 Unum International Unum UK Group Long-term Disability 364.9 353.4 358.9 Group Life 108.5 115.7 110.8 Supplemental 99.8 89.5 81.7 Unum Poland 79.6 71.9 17.4 652.8 630.5 568.8 Colonial Life Accident, Sickness, and Disability 975.1 973.4 929.3 Life 376.4 351.6 328.4 Cancer and Critical Illness 360.5 360.0 346.1 1,712.0 1,685.0 1,603.8 Closed Block Long-term Care 666.9 651.6 648.3 Individual Disability 319.6 374.3 420.8 All Other 7.9 7.6 8.0 994.4 1,033.5 1,077.1 Total Premium Income $ 9,378.1 $ 9,365.6 $ 8,986.1
Selected Operating Statement Data by Segment	Unum US Unum International Colonial Life Closed Block Corporate Total (in millions of dollars) Year Ended December 31, 2020 Premium Income $ 6,018.9 $ 652.8 $ 1,712.0 $ 994.4 $ — $ 9,378.1 Net Investment Income 720.3 104.6 155.7 1,370.3 9.8 2,360.7 Other Income 154.9 0.5 1.1 66.6 1.1 224.2 Adjusted Operating Revenue $ 6,894.1 $ 757.9 $ 1,868.8 $ 2,431.3 $ 10.9 $ 11,963.0 Adjusted Operating Income (Loss) $ 825.4 $ 76.6 $ 335.4 $ 241.4 $ (200.8) $ 1,278.0 Interest and Debt Expense $ — $ — $ — $ 3.1 $ 185.1 $ 188.2 Depreciation and Amortization $ 421.7 $ 20.1 $ 273.9 $ 5.9 $ 0.7 $ 722.3 Year Ended December 31, 2019 Premium Income $ 6,016.6 $ 630.5 $ 1,685.0 $ 1,033.5 $ — $ 9,365.6 Net Investment Income 739.4 122.5 148.0 1,404.9 20.5 2,435.3 Other Income 142.8 0.6 3.4 71.3 3.1 221.2 Adjusted Operating Revenue $ 6,898.8 $ 753.6 $ 1,836.4 $ 2,509.7 $ 23.6 $ 12,022.1 Adjusted Operating Income (Loss) $ 1,031.1 $ 107.9 $ 344.5 $ 137.7 $ (188.6) $ 1,432.6 Interest and Debt Expense $ — $ — $ — $ 5.3 $ 172.1 $ 177.4 Depreciation and Amortization $ 422.8 $ 18.7 $ 276.6 $ 7.7 $ 1.7 $ 727.5 Year Ended December 31, 2018 Premium Income $ 5,736.4 $ 568.8 $ 1,603.8 $ 1,077.1 $ — $ 8,986.1 Net Investment Income 778.7 117.2 151.2 1,377.1 29.5 2,453.7 Other Income 118.5 0.4 1.2 75.4 2.7 198.2 Adjusted Operating Revenue $ 6,633.6 $ 686.4 $ 1,756.2 $ 2,529.6 $ 32.2 $ 11,638.0 Adjusted Operating Income (Loss) $ 1,014.6 $ 113.9 $ 335.2 $ 125.5 $ (171.1) $ 1,418.1 Interest and Debt Expense $ — $ — $ — $ 6.9 $ 160.4 $ 167.3 Depreciation and Amortization $ 389.6 $ 17.6 $ 257.3 $ 8.3 $ 1.0 $ 673.8
Deferred Policy Acquisition Costs by Segment	Unum Colonial Unum US International Life Total (in millions of dollars) Deferred Acquisition Costs Year Ended December 31, 2020 Beginning of Year $ 1,223.0 $ 26.4 $ 1,074.6 $ 2,324.0 Capitalization 291.5 12.1 272.6 576.2 Amortization (341.0) (7.4) (257.7) (606.1) Adjustment Related to Unrealized Investment Gains and Losses (4.8) — (17.6) (22.4) Foreign Currency — 0.9 — 0.9 End of Year $ 1,168.7 $ 32.0 $ 1,071.9 $ 2,272.6 Year Ended December 31, 2019 Beginning of Year $ 1,239.4 $ 20.0 $ 1,050.0 $ 2,309.4 Capitalization 334.5 12.8 311.3 658.6 Amortization (344.0) (7.1) (258.8) (609.9) Adjustment Related to Unrealized Investment Gains and Losses (6.9) — (27.9) (34.8) Foreign Currency — 0.7 — 0.7 End of Year $ 1,223.0 $ 26.4 $ 1,074.6 $ 2,324.0 Year Ended December 31, 2018 Beginning of Year $ 1,205.4 $ 21.3 $ 957.9 $ 2,184.6 Capitalization 344.0 8.1 315.9 668.0 Amortization (315.1) (8.2) (242.2) (565.5) Adjustment Related to Unrealized Investment Gains and Losses 5.1 — 18.4 23.5 Foreign Currency — (1.2) — (1.2) End of Year $ 1,239.4 $ 20.0 $ 1,050.0 $ 2,309.4
Assets by Segment	December 31 2020 2019 (in millions of dollars) Assets Unum US $ 19,034.2 $ 18,586.3 Unum International 4,206.2 3,869.1 Colonial Life 4,864.3 4,629.0 Closed Block 38,187.2 37,008.7 Corporate 4,333.9 2,920.3 Total Assets $ 70,625.8 $ 67,013.4
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: Year Ended December 31 2020 2019 2018 (in millions of dollars) Total Revenue $ 13,162.1 $ 11,998.9 $ 11,598.5 Excluding: Net Realized Investment Gain (Loss) 1,199.1 (23.2) (39.5) Adjusted Operating Revenue $ 11,963.0 $ 12,022.1 $ 11,638.0 Income Before Income Tax $ 964.0 $ 1,382.1 $ 627.8 Excluding: Net Realized Investment Gains and Losses Net Realized Investment Gain Related to Reinsurance Transaction 1,302.3 — — Net Realized Investment Loss, Other (103.2) (23.2) (39.5) Total Net Realized Investment Gain (Loss) 1,199.1 (23.2) (39.5) Items Related to Closed Block Individual Disability Reinsurance Transaction Change in Benefit Reserves and Transaction Costs (1,305.5) — — Amortization of the Cost of Reinsurance (2.6) — — Total Items Related to Closed Block Individual Disability Reinsurance Transaction (1,308.1) — — Long-term Care Reserve Increase (151.5) — (750.8) Group Pension Reserve Increase (17.5) — — Impairment Loss on ROU Asset (12.7) — — Costs Related to Organizational Design Update (23.3) — — Costs Related to Early Retirement of Debt — (27.3) — Adjusted Operating Income $ 1,278.0 $ 1,432.6 $ 1,418.1

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Lease, Cost	Operating lease information is as follows: Year Ended December 31 2020 2019 (in millions of dollars) Lease Cost Operating Lease Cost $ 48.6 $ 29.4 Sublease Income (1.3) (1.9) Total Lease Cost $ 47.3 $ 27.5 Other Information Cash Paid for Amounts Included in the Measurement of Lease Liabilities $ 30.8 $ 28.9 Weighted-Average Remaining Lease Term 6 years 7 years Weighted-Average Discount Rate 4.37 % 4.60 % Operating lease cost as calculated prior to the adoption of ASC 842 was $29.2 million for the year ended December 31, 2018.
Lessee, Operating Lease, Liability, Maturity	As of December 31, 2020, aggregate undiscounted minimum net lease payments and the reconciliation to our lease liability are as follows (in millions of dollars): 2021 $ 25.4 2022 22.8 2023 16.5 2024 12.7 2025 9.8 2026 and Thereafter 34.4 Total 121.6 Less Imputed Interest 15.7 Lease Liability $ 105.9

Statutory Financial Informati_2

Statutory Financial Information (Tables)	12 Months Ended
	Dec. 31, 2020
Statutory Financial Information [Abstract]
Statutory Earnings and Surplus	The operating results and capital and surplus of our traditional U.S. life insurance subsidiaries and our captive reinsurers, prepared in accordance with prescribed or permitted accounting practices of the NAIC or states of domicile, are presented separately below. Year Ended December 31 2020 2019 2018 (in millions of dollars) Combined Net Income (Loss) Traditional U.S. Life Insurance Subsidiaries $ 646.8 $ 982.1 $ 953.0 Captive Reinsurers $ (201.0) $ (122.5) $ (109.6) Combined Net Gain (Loss) from Operations Traditional U.S. Life Insurance Subsidiaries $ 726.2 $ 1,027.2 $ 959.8 Captive Reinsurers $ (149.4) $ (108.4) $ (110.9) December 31 2020 2019 (in millions of dollars) Combined Capital and Surplus Traditional U.S. Life Insurance Subsidiaries $ 3,875.0 $ 3,644.4 Captive Reinsurers $ 2,088.0 $ 1,908.3

Unaudited Quarterly Results (Ta

Unaudited Quarterly Results (Tables)	12 Months Ended
	Dec. 31, 2020
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Financial Information	The following is a summary of our unaudited quarterly results of operations for 2020 and 2019: 2020 4 th 3 rd 2 nd 1 st (in millions of dollars, except share data) Premium Income $ 2,319.9 $ 2,318.1 $ 2,368.7 $ 2,371.4 Net Investment Income 593.5 613.2 569.0 585.0 Net Realized Investment Gain (Loss) 1,304.9 4.4 33.8 (144.0) Total Revenue 4,273.5 2,996.3 3,021.2 2,871.1 Income Before Income Tax 124.7 299.6 337.6 202.1 Net Income 135.4 231.1 265.5 161.0 Net Income Per Common Share Basic 0.66 1.13 1.30 0.79 Assuming Dilution 0.66 1.13 1.30 0.79 2019 4 th 3 rd 2 nd 1 st (in millions of dollars, except share data) Premium Income $ 2,352.6 $ 2,331.2 $ 2,343.1 $ 2,338.7 Net Investment Income 616.3 599.4 624.9 594.7 Net Realized Investment Gain (Loss) 9.2 (26.2) (7.3) 1.1 Total Revenue 3,034.6 2,960.0 3,016.7 2,987.6 Income Before Income Tax 377.4 299.4 352.0 353.3 Net Income 296.2 242.0 281.2 280.9 Net Income Per Common Share Basic 1.44 1.16 1.33 1.31 Assuming Dilution 1.44 1.16 1.33 1.31 Items affecting the comparability of our financial results are as follows: • Fourth quarter of 2020 net realized investment gain of $1,302.3 million before tax and $1,028.8 million after tax, related to the transfer of investments for the Closed Block individual disability reinsurance transaction. • Fourth quarter of 2020 impacts from the Closed Block individual disability reinsurance transaction of $1,305.5 million before tax and $1,031.3 million after tax. • Fourth quarter of 2020 amortization of the cost of reinsurance related to the Closed Block individual disability reinsurance transaction of $2.6 million before tax and $2.0 million after tax. • Fourth quarter of 2020 net tax benefit from the Closed Block individual disability reinsurance transaction of $36.5 million. • Fourth quarter of 2020 reserve increases of $151.5 million and $17.5 million before tax and $119.7 million and $13.8 million after tax related to long-term care and group pension, respectively. • Third quarter of 2020 costs related to organizational design update of $23.3 million before tax and $18.6 million after tax. • Second quarter of 2020 impairment on ROU asset related to an operating lease for office space that we do not plan to continue using to support our general operations of $12.7 million before tax and $10.0 million after tax. • Fourth quarter of 2019 cost related to the early retirement of debt of $2.1 million before tax and $1.7 million after tax. • Third quarter of 2019 cost related to the early retirement of debt of $25.2 million before tax and $19.9 million after tax.

Schedule II Condensed Financial

Schedule II Condensed Financial Information of Registrant (Tables)	12 Months Ended
	Dec. 31, 2020
Condensed Financial Statements, Captions
Schedule of Debt Instruments Parent Company Only	Debt consists of the following: December 31 2020 2019 Interest Rates Maturities (in millions of dollars) Long-term Debt Outstanding Principal Senior Secured Notes issued 2007 Variable 2037 $ — $ 80.0 Senior Notes issued 1998 6.750 - 7.250% 2028 335.8 335.8 Senior Notes issued 2002 7.375% 2032 39.5 39.5 Senior Notes issued 2012 and 2016 5.750% 2042 500.0 500.0 Senior Notes issued 2014 4.000% 2024 350.0 350.0 Senior Notes issued 2015 3.875% 2025 275.0 275.0 Senior Notes issued 2019 4.000% 2029 400.0 400.0 Senior Notes issued 2019 4.500% 2049 450.0 450.0 Senior Notes issued 2020 4.500% 2025 500.0 — Medium-term Notes issued 1990 - 1996 7.000 - 7.190% 2023 - 2028 20.5 20.5 Junior Subordinated Debt Securities issued 1998 7.405% 2038 203.7 203.7 Junior Subordinated Debt Securities issued 2018 6.250% 2058 300.0 300.0 Fair Value Hedge Adjustment — (0.6) Less: Unamortized Net Premium 6.0 8.4 Unamortized Debt Issuance Costs (34.8) (35.4) Total Long-term Debt 3,345.7 2,926.9 Short-term Debt Outstanding Principal Senior Notes issued 2010 5.625% 2020 — 400.0 Less Unamortized Debt Issuance Costs — (0.3) Total Short-term Debt — 399.7 Total Debt $ 3,345.7 $ 3,326.6
Parent Company
Condensed Financial Statements, Captions
Condensed Financial Information of Parent Company Only Balance Sheets	BALANCE SHEETS December 31 2020 2019 (in millions of dollars) Assets Fixed Maturity Securities - at fair value (amortized cost: $349.5; $122.3) $ 355.1 $ 125.6 Other Long-term Investments 10.6 35.2 Short-term Investments 164.5 604.4 Investment in Subsidiaries 14,122.6 12,820.9 Deferred Income Tax 158.8 122.7 Other Assets 496.7 488.9 Total Assets $ 15,308.3 $ 14,197.7 Liabilities and Stockholders' Equity Liabilities Short-term Debt $ — $ 399.7 Long-term Debt 3,345.7 2,846.9 Pension and Postretirement Benefits 677.5 624.2 Other Liabilities 414.1 361.9 Total Liabilities 4,437.3 4,232.7 Stockholders' Equity Common Stock 30.7 30.6 Additional Paid-in Capital 2,376.2 2,348.1 Accumulated Other Comprehensive Income 374.2 37.3 Retained Earnings 11,269.6 10,728.7 Treasury Stock (3,179.7) (3,179.7) Total Stockholders' Equity 10,871.0 9,965.0 Total Liabilities and Stockholders' Equity $ 15,308.3 $ 14,197.7 See notes to condensed financial information.
Condensed Financial Information of Parent Company Only Statement of Earnings	STATEMENTS OF OPERATIONS Year Ended December 31 2020 2019 2018 (in millions of dollars) Cash Dividends from Subsidiaries $ 974.6 $ 1,089.4 $ 1,135.4 Other Income 51.7 63.9 66.6 Total Revenue 1,026.3 1,153.3 1,202.0 Interest and Debt Expense 187.1 173.2 161.4 Cost Related to Early Retirement of Debt — 27.3 — Other Expenses 51.1 53.4 53.4 Total Expenses 238.2 253.9 214.8 Income of Parent Company Before Income Tax 788.1 899.4 987.2 Income Tax Benefit (15.3) (21.5) (1.7) Income of Parent Company 803.4 920.9 988.9 Equity in Undistributed Earnings (Loss) of Subsidiaries (10.4) 179.4 (465.5) Net Income 793.0 1,100.3 523.4 Other Comprehensive Income (Loss), Net of Tax 336.9 851.5 (924.2) Comprehensive Income (Loss) $ 1,129.9 $ 1,951.8 $ (400.8) See notes to condensed financial information.
Condensed Financial Information of Parent Company Only Statements of Cash Flows	STATEMENTS OF CASH FLOWS Year Ended December 31 2020 2019 2018 (in millions of dollars) Cash Provided by Operating Activities $ 964.0 $ 1,000.0 $ 1,052.1 Cash Flows from Investing Activities Proceeds from Maturities of Fixed Maturity Securities 138.8 16.6 52.5 Proceeds from Sales and Maturities of Other Investments 46.6 5.6 — Purchase of Fixed Maturity Securities (384.7) — (47.9) Purchase of Other Investments (22.0) — (22.3) Net Sales (Purchases) of Short-term Investments 440.6 (309.0) 192.6 Cash Distributions to Subsidiaries (965.5) (389.0) (530.8) Net Purchases of Property and Equipment (81.6) (85.9) (73.2) Acquisition of Business — — (146.1) Cash Used by Investing Activities (827.8) (761.7) (575.2) Cash Flows from Financing Activities Short-term Debt Repayment (400.0) — (200.0) Issuance of Long-term Debt 494.1 841.9 290.7 Long-term Debt Repayment — (433.1) — Cost Related to Early Retirement of Debt — (25.9) — Issuance of Common Stock 4.4 6.1 4.6 Repurchase of Common Stock — (400.3) (356.2) Dividends Paid to Stockholders (231.9) (229.2) (215.6) Other, Net (1.4) (3.7) (9.3) Cash Used by Financing Activities (134.8) (244.2) (485.8) Increase (Decrease) in Cash $ 1.4 $ (5.9) $ (8.9) See notes to condensed financial information.
Schedule of Debt Instruments Parent Company Only	Debt consists of the following: December 31 2020 2019 Interest Rates Maturities (in millions of dollars) Long-term Debt Outstanding Principal Senior Notes issued 1998 6.750 - 7.250% 2028 $ 335.8 $ 335.8 Senior Notes issued 2002 7.375% 2032 39.5 39.5 Senior Notes issued 2012 and 2016 5.750% 2042 500.0 500.0 Senior Notes issued 2014 4.000% 2024 350.0 350.0 Senior Notes issued 2015 3.875% 2025 275.0 275.0 Senior Notes issued 2019 4.000% 2029 400.0 400.0 Senior Notes issued 2019 4.500% 2049 450.0 450.0 Senior Notes issued 2020 4.500% 2025 500.0 — Medium-term Notes issued 1990 - 1996 7.000 - 7.190% 2023 - 2028 20.5 20.5 Junior Subordinated Debt Securities issued 1998 7.405% 2038 203.7 203.7 Junior Subordinated Debt Securities issued 2018 6.250% 2058 300.0 300.0 Fair Value Hedge Adjustment — (0.6) Less: Unamortized Net Premium 6.0 8.4 Unamortized Debt Issuance Costs (34.8) (35.4) Total Long-term Debt 3,345.7 2,846.9 Short-term Debt Outstanding Principal Senior Notes issued 2010 5.625% 2020 — 400.0 Less Unamortized Debt Issuance Costs — (0.3) Total Short-term Debt — 399.7 Total Debt $ 3,345.7 $ 3,246.6

Significant Accounting Polici_3

Significant Accounting Policies Schedule of New Accounting Pronouncements (Details) - USD ($) $ in Millions	Dec. 31, 2020	Jan. 01, 2020	Dec. 31, 2019
New Accounting Pronouncements or Change in Accounting Principle
Mortgage Loans	$ 2,432.1		$ 2,397
Reinsurance Recoverables	10,666		4,780.7
Accounts and Premiums Receivable	1,519.3		1,602.9
Deferred Income Tax	416.1		95.4
Other Liabilities	2,471.4		1,880.5
Retained Earnings	$ 11,269.6		10,728.7
Accounting Standards Update 2016-13
New Accounting Pronouncements or Change in Accounting Principle
Mortgage Loans		$ 2,388.7	2,397
Reinsurance Recoverables		4,778.9	4,780.7
Accounts and Premiums Receivable		1,589.4	1,602.9
Deferred Income Tax		90.4	95.4
Other Liabilities		1,856.8	1,856.5
Retained Earnings		10,709.8	$ 10,728.7
Accounting Standards Update 2016-13 | Restatement Adjustment
New Accounting Pronouncements or Change in Accounting Principle
Mortgage Loans		(8.3)
Reinsurance Recoverables		(1.8)
Accounts and Premiums Receivable		(13.5)
Deferred Income Tax		(5)
Other Liabilities		0.3
Retained Earnings		$ (18.9)

Significant Accounting Polici_4

Significant Accounting Policies - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)Integer	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Jan. 01, 2020USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of Operating Segments | Integer	3
Ceded Policy Loans	$ 3,390.6	$ 3,490.6
Premium Receivable, Allowance for Credit Loss	38.8			$ 23.8
Premiums Receivable, Gross	525.8			543
Premium Receivable, Credit Loss Expense (Reversal)	15
Accumulated Depreciation for Property and Equipment	1,239.9	1,195.3
Value of Business Acquired	83.8	88.7
Accumulated Amortization of Value of Business Acquired	153.7	144.1
Amortization of Value of Business Acquired	6.1	7.1	$ 6.4
Prepaid Reinsurance Premiums	813
Deferred Gain on Reinsurance	5.6	8.5
Reinsurance Recoverable, Allowance for Credit Loss	11.7	0		$ 1.8
Reinsurance Recoverable, Credit Loss Expense (Reversal)	9.9
Premium Tax Expense	175.5	170.1	$ 155.8
Participation Fund Account Assets (PFA)	$ 319.8	$ 311.2

Fair Values of Financial Inst_3

Fair Values of Financial Instruments Private Equity Partnerships (Details) - Private Equity Partnerships - USD ($) $ in Millions	Dec. 31, 2020		Dec. 31, 2019
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share
Alternative Investments	$ 747.5		$ 616.7
Alternative Investments, Unfunded Commitments	590.7		475.1
Private Credit
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share
Alternative Investments	273.7		263.2
Alternative Investments, Unfunded Commitments	180.2		152.7
Private Credit | Not Redeemable
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share
Alternative Investments	233.3	[1]	223.6
Alternative Investments, Unfunded Commitments	178.9		152.6
Private Credit | Quarterly after 2 year lock with 90 days notice
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share
Alternative Investments	40.4		39.6
Alternative Investments, Unfunded Commitments	1.3		0.1
Private Equity Limited Partnership
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share
Alternative Investments	241.8
Alternative Investments, Unfunded Commitments	225.3
Private Equity Limited Partnership | Not Redeemable
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share
Alternative Investments	232.6	[2]	149.3
Alternative Investments, Unfunded Commitments	191		166.8
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
Alternative Investments, Unfunded Commitments	34.3
Real Assets
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share
Alternative Investments	232		204.2
Alternative Investments, Unfunded Commitments	185.2		155.6
Real Assets | Not Redeemable
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share
Alternative Investments	176.3	[3]	173.8
Alternative Investments, Unfunded Commitments	185.2		130.6
Real Assets | Quarterly
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share
Alternative Investments	55.7		30.4
Alternative Investments, Unfunded Commitments	$ 0		$ 25
[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 December 31, 2020, the estimated remaining life of the investments that do not allow for redemptions is approximately 37 percent in the next 3 years, 38 percent during the period from 3 to 5 years, 22 percent during the period from 5 to 10 years, and 3 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 December 31, 2020, the estimated remaining life of the investments that do not allow for redemptions is approximately 20 percent in the next 3 years, 35 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 December 31, 2020, the estimated remaining life of the investments that do not allow for redemptions is approximately 12 percent in the next 3 years, 23 percent during period from 3 to 5 years, 64 percent during the period from 5 to 10 years, and 1 percent during the period from 10 to 15 years.

Fair Value Measurements by Inpu

Fair Value Measurements by Input Level (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Fixed Maturity Securities
Fixed Maturity Securities	$ 44,137.3	$ 47,443.7
Derivative Assets	19.8	27.5
Equity Securities	28.3	32.6
Other Long-term Investments	960.2	844.2
Assets, Fair Value Disclosure	44,932.9	48,120.5
Liabilities
Derivative Liabilities	99.5	57.4
Liabilities, Fair Value Disclosure	99.5	57.4
Foreign Exchange Contracts
Liabilities
Derivative Liabilities	59.2	34
Interest Rate Swaps
Liabilities
Derivative Liabilities	0.5	0.6
Embedded Derivative in Modified Coinsurance Arrangement
Liabilities
Derivative Liabilities	39.8	22.8
Fair Value, Measurements, Recurring
Fixed Maturity Securities
Other Long-term Investments	795.6	676.8
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Fixed Maturity Securities
Fixed Maturity Securities	4,221.3	4,698.3
Derivative Assets	0	0
Equity Securities	8.4	0
Other Long-term Investments	8.4	0
Assets, Fair Value Disclosure	4,229.7	4,698.3
Liabilities
Liabilities, Fair Value Disclosure	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 | Interest Rate Swaps
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	38,668.6	42,032.6
Derivative Assets	19.8	27.5
Equity Securities	15.2	28
Other Long-term Investments	35	55.5
Assets, Fair Value Disclosure	38,703.6	42,088.1
Liabilities
Liabilities, Fair Value Disclosure	59.7	34.6
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | Foreign Exchange Contracts
Liabilities
Derivative Liabilities	59.2	34
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | Interest Rate Swaps
Liabilities
Derivative Liabilities	0.5	0.6
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	1,247.4	712.8
Derivative Assets	0	0
Equity Securities	4.7	4.6
Other Long-term Investments	4.7	4.6
Assets, Fair Value Disclosure	1,252.1	717.4
Liabilities
Liabilities, Fair Value Disclosure	39.8	22.8
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 | Interest Rate Swaps
Liabilities
Derivative Liabilities	0	0
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3 | Embedded Derivative in Modified Coinsurance Arrangement
Liabilities
Derivative Liabilities	39.8	22.8
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	747.5	616.7
Assets, Fair Value Disclosure	747.5	616.7
Liabilities
Liabilities, Fair Value Disclosure	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 | Interest Rate Swaps
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	709.8	1,401.7
United States Government and Government Agencies and Authorities | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Fixed Maturity Securities
Fixed Maturity Securities	0	412.8
United States Government and Government Agencies and Authorities | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Fixed Maturity Securities
Fixed Maturity Securities	709.8	988.9
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	4,261.2	3,363.4
States, Municipalities, and Political Subdivisions | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Fixed Maturity Securities
Fixed Maturity Securities	0	0
States, Municipalities, and Political Subdivisions | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Fixed Maturity Securities
Fixed Maturity Securities	4,245.7	3,321.6
States, Municipalities, and Political Subdivisions | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fixed Maturity Securities
Fixed Maturity Securities	15.5	41.8
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	1,168.2	1,017.7
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	1,146.4	995.9
Foreign Governments | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fixed Maturity Securities
Fixed Maturity Securities	21.8	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	6,962.3	7,732.2
Public Utilities | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Fixed Maturity Securities
Fixed Maturity Securities	131.9	171.1
Public Utilities | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Fixed Maturity Securities
Fixed Maturity Securities	6,644.7	7,546.5
Public Utilities | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fixed Maturity Securities
Fixed Maturity Securities	185.7	14.6
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	1,107.7	1,478.7
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	1,026.4	1,444.6
Mortgage/Asset-backed Securities | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fixed Maturity Securities
Fixed Maturity Securities	81.3	34.1
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
All Other Corporate Bonds
Fixed Maturity Securities
Fixed Maturity Securities	29,918.6	32,410.4
All Other Corporate Bonds | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Fixed Maturity Securities
Fixed Maturity Securities	4,089.4	4,114.4
All Other Corporate Bonds | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Fixed Maturity Securities
Fixed Maturity Securities	24,886.1	27,695.5
All Other Corporate Bonds | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fixed Maturity Securities
Fixed Maturity Securities	943.1	600.5
All Other Corporate Bonds | 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	9.5	39.6
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	9.5	39.6
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
Foreign Exchange Contracts
Fixed Maturity Securities
Derivative Assets	19.7	27
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	19.7	27
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	0.5
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	0.5
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 Partnerships
Fixed Maturity Securities
Alternative Investments	747.5	616.7
Private Equity Partnerships | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Fixed Maturity Securities
Alternative Investments	0	0
Private Equity Partnerships | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Fixed Maturity Securities
Alternative Investments	0	0
Private Equity Partnerships | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fixed Maturity Securities
Alternative Investments	0	0
Private Equity Partnerships | Fair Value, Measurements, Recurring | Fair Value Measured at Net Asset Value Per Share
Fixed Maturity Securities
Alternative Investments	747.5	616.7
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	59.7	34.6
Derivatives | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Liabilities
Derivative Liabilities	39.8	22.8
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	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Embedded Derivative in Modified Coinsurance Arrangement
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Derivatives Measured with Unobservable Inputs, Beginning Balance	$ (22.8)	$ (31.1)
Derivative Liability Gain (Loss) Included in Earnings	(17)	8.3
Derivative Liability Gain (Loss) Included in OCI	0	0
Derivative Purchases	0	0
Derivative Sales	0	0
Derivative Transfers Into Level 3	0	0
Derivative Transfers Out of Level 3	0	0
Derivatives Measured with Unobservable Inputs, Ending Balance	(39.8)	(22.8)
Embedded Derivative in Modified Coinsurance Arrangement | Net Investment Income
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Fair Value, Net Derivative Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss)	(17)
Embedded Derivative in Modified Coinsurance Arrangement | Other Comprehensive Income (Loss)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Fair Value, Net Derivative Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss)	0
States, Municipalities, and Political Subdivisions
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Assets Measured with Unobservable Inputs, Beginning Balance	41.8	0
Investment Gain (Loss) included in Earnings	0	0
Investment Gain (Loss) included in OCI	2.2	2.8
Investment Purchases	0	13.3
Investment Sales	0	0
Investment Level 3 Transfers Into	0	25.7
Investment Level 3 Transfers Out of	(28.5)	0
Assets Measured with Unobservable Inputs, Ending Balance	15.5	41.8
States, Municipalities, and Political Subdivisions | Net Investment Income
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	0
States, Municipalities, and Political Subdivisions | Other Comprehensive Income (Loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	1.7
Foreign Governments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Assets Measured with Unobservable Inputs, Beginning Balance	21.8	31.4
Investment Gain (Loss) included in Earnings	0	0
Investment Gain (Loss) included in OCI	0	0.6
Investment Purchases	0	0
Investment Sales	0	(10.2)
Investment Level 3 Transfers Into	0	0
Investment Level 3 Transfers Out of	0	0
Assets Measured with Unobservable Inputs, Ending Balance	21.8	21.8
Foreign Governments | Net Investment Income
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	0
Foreign Governments | Other Comprehensive Income (Loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	0
Public Utilities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Assets Measured with Unobservable Inputs, Beginning Balance	14.6	84.7
Investment Gain (Loss) included in Earnings	0	0
Investment Gain (Loss) included in OCI	3.8	0.8
Investment Purchases	0	0
Investment Sales	0	0
Investment Level 3 Transfers Into	175.9	6
Investment Level 3 Transfers Out of	(8.6)	(76.9)
Assets Measured with Unobservable Inputs, Ending Balance	185.7	14.6
Public Utilities | Net Investment Income
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	0
Public Utilities | Other Comprehensive Income (Loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	3.7
Mortgage/Asset-backed Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Assets Measured with Unobservable Inputs, Beginning Balance	34.1	0
Investment Gain (Loss) included in Earnings	0	0
Investment Gain (Loss) included in OCI	(3)	(2.7)
Investment Purchases	0	0
Investment Sales	(67.9)	0
Investment Level 3 Transfers Into	118.1	36.8
Investment Level 3 Transfers Out of	0	0
Assets Measured with Unobservable Inputs, Ending Balance	81.3	34.1
Mortgage/Asset-backed Securities | Net Investment Income
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	0
Mortgage/Asset-backed Securities | Other Comprehensive Income (Loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	(3.5)
All Other Corporate Bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Assets Measured with Unobservable Inputs, Beginning Balance	600.5	1,495.8
Investment Gain (Loss) included in Earnings	0	0
Investment Gain (Loss) included in OCI	29.8	(3.1)
Investment Purchases	194.7	93
Investment Sales	(36.1)	(86)
Investment Level 3 Transfers Into	343.1	190.6
Investment Level 3 Transfers Out of	(188.9)	(1,089.8)
Assets Measured with Unobservable Inputs, Ending Balance	943.1	600.5
All Other Corporate Bonds | Net Investment Income
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	0
All Other Corporate Bonds | Other Comprehensive Income (Loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	26.7
Redeemable Preferred Stocks
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Assets Measured with Unobservable Inputs, Beginning Balance	0	21.1
Investment Gain (Loss) included in Earnings		0
Investment Gain (Loss) included in OCI		0
Investment Purchases		0
Investment Sales		0
Investment Level 3 Transfers Into		0
Investment Level 3 Transfers Out of		(21.1)
Assets Measured with Unobservable Inputs, Ending Balance		0
Fixed Maturity Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Assets Measured with Unobservable Inputs, Beginning Balance	712.8	1,633
Investment Gain (Loss) included in Earnings	0	0
Investment Gain (Loss) included in OCI	32.8	(1.6)
Investment Purchases	194.7	106.3
Investment Sales	(104)	(96.2)
Investment Level 3 Transfers Into	637.1	259.1
Investment Level 3 Transfers Out of	(226)	(1,187.8)
Assets Measured with Unobservable Inputs, Ending Balance	1,247.4	712.8
Fixed Maturity Securities | Net Investment Income
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	0
Fixed Maturity Securities | Other Comprehensive Income (Loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	28.6
Perpetual Preferred Equity Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Assets Measured with Unobservable Inputs, Beginning Balance	4.6	4.6
Investment Gain (Loss) included in Earnings	0.1	0
Investment Gain (Loss) included in OCI	0	0
Investment Purchases	0	0
Investment Sales	0	0
Investment Level 3 Transfers Into	0	0
Investment Level 3 Transfers Out of	0	0
Assets Measured with Unobservable Inputs, Ending Balance	4.7	$ 4.6
Perpetual Preferred Equity Securities | Net Investment Income
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	0.1
Perpetual Preferred Equity Securities | Other Comprehensive Income (Loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	$ 0

Quantitative Information Regard

Quantitative Information Regarding Significant Unobservable Inputs (Details) $ in Millions		Dec. 31, 2020USD ($)Rate	Dec. 31, 2019USD ($)Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity Securities | $		$ 28.3	$ 32.6
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 | $	[1]	(39.8)	(22.8)
Fair Value, Inputs, Level 3 | All Other Corporate Bonds | Market Approach
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
All Other Corporate Bonds - Private | $	[2]	$ 45.7	$ 119.2	[3],[4]
Fair Value, Inputs, Level 3 | All Other Corporate Bonds | Market Approach | Minimum | Lack of Marketability
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
All Other Corporate Bonds - Private, Measurement Input			0.0456
Fair Value, Inputs, Level 3 | All Other Corporate Bonds | Market Approach | Minimum | Volatility of Credit
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
All Other Corporate Bonds - Private, Measurement Input		0.0050	0.0035
Fair Value, Inputs, Level 3 | All Other Corporate Bonds | Market Approach | Maximum | Lack of Marketability
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
All Other Corporate Bonds - Private, Measurement Input			0.0456
Fair Value, Inputs, Level 3 | All Other Corporate Bonds | Market Approach | Maximum | Volatility of Credit
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
All Other Corporate Bonds - Private, Measurement Input		0.2490	0.1768
Fair Value, Inputs, Level 3 | All Other Corporate Bonds | Market Approach | Weighted Average | Lack of Marketability
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
All Other Corporate Bonds - Private, Measurement Input			0.0456
Fair Value, Inputs, Level 3 | All Other Corporate Bonds | Market Approach | Weighted Average | Volatility of Credit
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
All Other Corporate Bonds - Private, Measurement Input		0.0363	0.022
Fair Value, Inputs, Level 3 | Perpetual Preferred Equity Securities | Market Approach
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity Securities | $	[3]	$ 4.7	$ 4.6
[1]	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.
[2]	Represents basis point adjustments for credit-specific factors
[3]	Represents a decision to price based on par value, cost, or owner's equity when limited data is available
[4]	Represents basis point adjustments to apply a discount due to the illiquidity of an investment

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	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Mortgage Loans	$ 2,432.1	$ 2,397
Policy Loans	3,683.9	3,779.5
Long-term Debt	3,345.7	2,926.9
Unfunded Commitments	0.9
Liabilities, Fair Value Disclosure	99.5	57.4
Fair Value, Nonrecurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Mortgage Loans, Fair Value Disclosure	2,641.8	2,556.3
Mortgage Loans	2,432.1	2,397
Policy Loans, Fair Value Disclosure	3,850.8	3,911.4
Policy Loans	3,683.9	3,779.5
Miscellaneous Long-Term Investments, Fair Value Disclosure	57.5	76.9
Miscellaneous Long-Term Investments	57.5	76.9
Financial Instruments, Financial Assets Fair Value Disclosure	6,550.1	6,544.6
Total Financial Instrument Assets Not Carried at Fair Value	6,173.5	6,253.4
Long-term Debt, Fair Value Disclosure	3,887.4	3,239
Long-term Debt	3,345.7	2,926.9
Federal Home Loan Bank Funding Agreements, Fair Value Disclosure	312.2
Federal Home Loan Bank Funding Agreements	312.2
Unfunded Commitments	0.9	1.9
Liabilities, Fair Value Disclosure	4,200.5	3,240.9
Total Financial Instrument Liabilities Not Carried at Fair Value	3,658.8	2,928.8
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	2,393.1	1,712.8
Federal Home Loan Bank Funding Agreements, Fair Value Disclosure	0
Unfunded Commitments	0	0
Liabilities, Fair Value Disclosure	2,393.1	1,712.8
Fair Value, Inputs, Level 2 | Fair Value, Nonrecurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Mortgage Loans, Fair Value Disclosure	2,641.8	2,556.3
Policy Loans, Fair Value Disclosure	0	0
Miscellaneous Long-Term Investments, Fair Value Disclosure	28.2	18.5
Financial Instruments, Financial Assets Fair Value Disclosure	2,670	2,574.8
Long-term Debt, Fair Value Disclosure	1,494.3	1,526.2
Federal Home Loan Bank Funding Agreements, Fair Value Disclosure	312.2
Unfunded Commitments	0.9	1.9
Liabilities, Fair Value Disclosure	1,807.4	1,528.1
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	3,850.8	3,911.4
Miscellaneous Long-Term Investments, Fair Value Disclosure	29.3	58.4
Financial Instruments, Financial Assets Fair Value Disclosure	3,880.1	3,969.8
Long-term Debt, Fair Value Disclosure	0	0
Federal Home Loan Bank Funding Agreements, Fair Value Disclosure	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	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Ceded Policy Loans	$ 3,390.6	$ 3,490.6
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	9.60%
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	74.90%
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	10.40%
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	90.40%
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	Dec. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale
Amortized Cost of Fixed Maturity Securities	$ 36,546.5	$ 41,079.3
Debt Securities, Available-for-sale, Allowance for Credit Loss	6.8	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	7,653.5
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	55.9
Debt Securities, Available-for-sale, Total	44,137.3	47,443.7
United States Government and Government Agencies and Authorities
Debt Securities, Available-for-sale
Amortized Cost of Fixed Maturity Securities	559	1,246.1
Debt Securities, Available-for-sale, Allowance for Credit Loss	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	150.8	156
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0	0.4
Debt Securities, Available-for-sale, Total	709.8	1,401.7
States, Municipalities, and Political Subdivisions
Debt Securities, Available-for-sale
Amortized Cost of Fixed Maturity Securities	3,609.9	2,863.1
Debt Securities, Available-for-sale, Allowance for Credit Loss	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	652.8	507.6
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1.5	7.3
Debt Securities, Available-for-sale, Total	4,261.2	3,363.4
Foreign Governments
Debt Securities, Available-for-sale
Amortized Cost of Fixed Maturity Securities	902.9	843.5
Debt Securities, Available-for-sale, Allowance for Credit Loss	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	266.5	175.2
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1.2	1
Debt Securities, Available-for-sale, Total	1,168.2	1,017.7
Public Utilities
Debt Securities, Available-for-sale
Amortized Cost of Fixed Maturity Securities	5,486.4	6,436.7
Debt Securities, Available-for-sale, Allowance for Credit Loss	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1,481.9	1,303.7
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	6	8.2
Debt Securities, Available-for-sale, Total	6,962.3	7,732.2
Mortgage/Asset-backed Securities
Debt Securities, Available-for-sale
Amortized Cost of Fixed Maturity Securities	1,019.9	1,377.8
Debt Securities, Available-for-sale, Allowance for Credit Loss	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	88	101.3
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0.2	0.4
Debt Securities, Available-for-sale, Total	1,107.7	1,478.7
All Other Corporate Bonds
Debt Securities, Available-for-sale
Amortized Cost of Fixed Maturity Securities	24,958.8	28,273.1
Debt Securities, Available-for-sale, Allowance for Credit Loss	6.8	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	5,013.5	4,211.2
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	46.9	73.9
Debt Securities, Available-for-sale, Total	29,918.6	32,410.4
Redeemable Preferred Stocks
Debt Securities, Available-for-sale
Amortized Cost of Fixed Maturity Securities	9.6	39
Debt Securities, Available-for-sale, Allowance for Credit Loss	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0.6
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0.1	0
Debt Securities, Available-for-sale, Total	9.5	39.6
Fixed Maturity Securities
Debt Securities, Available-for-sale
Amortized Cost of Fixed Maturity Securities	36,546.5	41,079.3
Debt Securities, Available-for-sale, Allowance for Credit Loss	6.8
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	7,653.5	6,455.6
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	55.9	91.2
Debt Securities, Available-for-sale, Total	$ 44,137.3	$ 47,443.7

Length of Time Fixed Maturity S

Length of Time Fixed Maturity Securities had been in a Gross Unrealized Loss Position (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
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		$ 110.2
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		0.4
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	$ 133.4	331
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	1.5	7.3
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0.1	0.3
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	20.3	69.4
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	1.2	1
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	76.3	168.3
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	3.7	2.6
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	25.4	37
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	2.3	5.6
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	3	47
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0.1	0.4
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	0.1	0
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	520.4	579.1
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	22.4	29.1
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	113.5	379.8
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	24.5	44.8
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	762.9	1,305
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	29	40.8
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	142.1	420.2
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 26.9	$ 50.4

Investments Distribution of the

Investments Distribution of the Maturity Dates for Fixed Maturity Securities (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale, Amortized Cost, Net of Allowance for Credit Losses, Fiscal Year Maturity [Abstract]
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Amortized Cost	$ 881.8
Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year One Through Five, Net	6,162.6
Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year 5 Through 10, Net	10,886.9
Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year 10, Net	17,588.5
Available for sale Securities Debt Maturities Amortized Cost Gross Subtotal, Net	35,519.8
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Amortized Cost, Net	1,019.9
Debt Securities, Available-for-sale, Amortized Cost, Net of Allowance for Credit Losses	36,539.7
Debt Securities, Available-for-sale, Amortized Cost, Fiscal Year Maturity [Abstract]
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Amortized Cost		$ 821.5
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Amortized Cost		6,286.2
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Amortized Cost		13,570.8
Debt Securities, Available-for-sale, Allocated and Single Maturity Date, Maturity, after 10 Years, Amortized Cost		19,023
Available for sale Securities Debt Maturities Amortized Cost Gross Subtotal		39,701.5
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Amortized Cost		1,377.8
Debt Securities, Available-for-sale, Amortized Cost, Total	36,546.5	41,079.3
Available for Sale Securities Unrealized Gain Position Gross Gain [Abstract]
Available For Sale Securities Debt Maturities Within One Year Unrealized Gain Position Gross Gain	19.5	14.5
Available For Sale Securities Debt Maturities After One Through Five Years Unrealized Gain Position Gross Gain	589.9	456.5
Available For Sale Securities Debt Maturities After Five Through Ten Years Unrealized Gain Position Gross Gain	1,914.8	1,688.3
Available For Sale Securities Debt Maturities After Ten Years Unrealized Gain Position Gross Gain	5,041.3	4,195
Available For Sale Securities Debt Maturities Unrealized Gain Position Gross Gain Gross Subtotal	7,565.5	6,354.3
Available For Sale Securities Debt Maturities Without Single Maturity Date Unrealized Gain Position Gross Gain	88	101.3
Available for sale Securities, Debt Maturities Unrealized Gain Position Gross Gain	7,653.5	6,455.6
Available for Sale Securities Unrealized Loss Position Gross Loss [Abstract]
Available For Sale Securities Debt Maturities Within One Year Unrealized Loss Position Gross Loss	2.9	0.2
Available For Sale Securities Debt Maturities After One Through Five Years Unrealized Loss Position Gross Loss	22.9	41.7
Available For Sale Securities Debt Maturities After Five Through Ten Years Unrealized Loss Position Gross Loss	10.7	14.6
Available For Sale Securities Debt Maturities After Ten Years Unrealized Loss Position Gross Loss	19.2	34.3
Available For Sale Securities Debt Maturities Unrealized Gain Position Gross Loss Gross Subtotal	55.7	90.8
Available For Sale Securities Debt Maturities Without Single Maturity Date Unrealized Loss Position Gross Loss	0.2	0.4
Available For Sale Securities Unrealized Loss Position Gross Loss Subtotal	55.9	91.2
Fair Value Maturity Distribution [Abstract]
Debt Securities, Available-for-sale, Total	44,137.3	47,443.7
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	836.4	832.6
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Fair Value	6,545.7	6,423.4
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Fair Value	12,659.4	14,881.3
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after 10 Years, Fair Value	22,089.2	22,152.6
Available for sale Securities Debt Maturities Fair Value Gross Subtotal	42,130.7	44,289.9
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Fair Value	1,101.6	1,428.6
Debt Securities, Available-for-sale, Total	43,232.3	45,718.5
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	62	3.2
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Fair Value	183.9	277.6
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Fair Value	131.6	363.2
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after 10 Years, Fair Value	521.4	1,031.1
Available for sale Securities Debt Maturities Fair Value Gross Subtotal	898.9	1,675.1
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Fair Value	6.1	50.1
Debt Securities, Available-for-sale, Total	$ 905	$ 1,725.2

Investments Distribution by Ext

Investments Distribution by External Credit Rating for Fixed Maturity Securities (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale
Fixed Maturity Securities	$ 44,137.3	$ 47,443.7
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	7,653.5
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	$ 55.9
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	$ 40,637.2
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	7,371.5
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	$ 18.1
Fixed maturity securities in unrealized loss position percent of total	32.40%
External Credit Rating, Below-Investment-Grade
Debt Securities, Available-for-sale
Fixed Maturity Securities	$ 3,500.1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	282
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	$ 37.8
Fixed maturity securities in unrealized loss position percent of total	67.60%

Debt Securities, Available-for-

Debt Securities, Available-for-sale, Allowance for Credit Losses Rollforward (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale, Allowance for Credit Loss
Debt Securities, Available-for-sale, Allowance for Credit Loss	$ 6.8	$ 0
All Other Corporate Bonds
Debt Securities, Available-for-sale, Allowance for Credit Loss
Debt Securities, Available-for-sale, Allowance for Credit Loss	6.8	$ 0
Debt Securities, Available-for-sale, Allowance for Credit Loss, Not Previously Recorded	44.5
Debt Securities, Available-for-sale, Allowance for Credit Loss, Not to Sell before Recovery, Credit Loss, Previously Recorded, Expense (Reversal)	(37.7)
Debt Securities, Available-for-sale, Change in Present Value, Expense (Reversal)	$ 0

Investments Low Income Housing

Investments Low Income Housing Tax Credits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Low Income Housing Tax Credits [Abstract]
Affordable Housing Tax Credits	$ 33.2	$ 37.8	$ 41.4
Amortization of Affordable Housing Tax Credit Investments	(21.9)	(25.2)	(28.1)
Tax Benefits from Low Income Housing Investments	$ 11.3	$ 12.6	$ 13.3

Mortgage Loans by Property Type

Mortgage Loans by Property Type and Geographic Region (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Mortgage Loans on Real Estate
Mortgage Loans	$ 2,432.1	$ 2,397
Percent of Total	100.00%	100.00%
New England
Mortgage Loans on Real Estate
Mortgage Loans	$ 40	$ 28.9
Percent of Total	1.60%	1.20%
Mid-Atlantic
Mortgage Loans on Real Estate
Mortgage Loans	$ 202.5	$ 184.5
Percent of Total	8.20%	7.70%
East North Central
Mortgage Loans on Real Estate
Mortgage Loans	$ 330.4	$ 329.2
Percent of Total	13.60%	13.70%
West North Central
Mortgage Loans on Real Estate
Mortgage Loans	$ 196.1	$ 215.4
Percent of Total	8.10%	9.00%
South Atlantic
Mortgage Loans on Real Estate
Mortgage Loans	$ 512	$ 509.2
Percent of Total	21.10%	21.20%
East South Central
Mortgage Loans on Real Estate
Mortgage Loans	$ 110	$ 114.3
Percent of Total	4.50%	4.80%
West South Central
Mortgage Loans on Real Estate
Mortgage Loans	$ 257.4	$ 246.6
Percent of Total	10.60%	10.30%
Mountain
Mortgage Loans on Real Estate
Mortgage Loans	$ 268.8	$ 268.2
Percent of Total	11.10%	11.20%
Pacific
Mortgage Loans on Real Estate
Mortgage Loans	$ 514.9	$ 500.7
Percent of Total	21.20%	20.90%
Apartment
Mortgage Loans on Real Estate
Mortgage Loans	$ 638	$ 608.8
Percent of Total	26.20%	25.40%
Industrial
Mortgage Loans on Real Estate
Mortgage Loans	$ 654	$ 623.6
Percent of Total	26.90%	26.00%
Office
Mortgage Loans on Real Estate
Mortgage Loans	$ 517.8	$ 549.3
Percent of Total	21.30%	22.90%
Retail
Mortgage Loans on Real Estate
Mortgage Loans	$ 575.6	$ 567.5
Percent of Total	23.70%	23.70%
Other Property
Mortgage Loans on Real Estate
Mortgage Loans	$ 46.7	$ 47.8
Percent of Total	1.90%	2.00%

Schedule of Participating Mortg

Schedule of Participating Mortgage Loans by Internal Credit Rating and Loan to Value (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Mortgage Loans on Real Estate
Mortgage Loans	$ 2,432.1	$ 2,397
Percent of Total	100.00%	100.00%
Loan to Value Ratio Below or Equal to 65 Percent
Mortgage Loans on Real Estate
Mortgage Loans	$ 1,189.4	$ 1,215.1
Percent of Total	48.90%	50.70%
Loan To Value Ratio Above 65 To 75 Percent
Mortgage Loans on Real Estate
Mortgage Loans	$ 1,000.3	$ 1,053
Percent of Total	41.10%	43.90%
Loan To Value Ratio Above 75 To 85 Percent
Mortgage Loans on Real Estate
Mortgage Loans	$ 155.8	$ 91.4
Percent of Total	6.40%	3.80%
Loan To Value Ratio Above 85 Percent
Mortgage Loans on Real Estate
Mortgage Loans	$ 86.6	$ 37.5
Percent of Total	3.60%	1.60%
Total
Mortgage Loans on Real Estate
Percent of Total	100.00%	100.00%
AA Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans	$ 3.5	$ 0
Percent of Total	0.10%	0.00%
A Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans	$ 510	$ 485.6
Percent of Total	21.00%	20.30%
BBB Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans	$ 1,863	$ 1,911.4
Percent of Total	76.60%	79.70%
BB Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans	$ 39.4	$ 0
Percent of Total	1.60%	0.00%
B Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans	$ 16.2	$ 0
Percent of Total	0.70%	0.00%
Total
Mortgage Loans on Real Estate
Percent of Total	100.00%	100.00%

Mortgage Loans Sorted by Applic

Mortgage Loans Sorted by Applicable Credit Quality Indicators (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Jan. 01, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator
Financing Receivable, Allowance for Credit Loss	$ (13.1)		$ 0
Mortgage Loans	2,432.1		2,397
Loan to Value Ratio Below or Equal to 65 Percent
Financing Receivable, Credit Quality Indicator
Mortgage Loans	1,189.4		1,215.1
Loan To Value Ratio Above 65 To 75 Percent
Financing Receivable, Credit Quality Indicator
Mortgage Loans	1,000.3		1,053
Loan To Value Ratio Above 75 To 85 Percent
Financing Receivable, Credit Quality Indicator
Mortgage Loans	155.8		91.4
Loan To Value Ratio Above 85 Percent
Financing Receivable, Credit Quality Indicator
Mortgage Loans	86.6		37.5
Originated Five or More Years before Last Fiscal Year
Financing Receivable, Credit Quality Indicator
Mortgage Loans	769.6
Originated Four Years before Last Fiscal Year
Financing Receivable, Credit Quality Indicator
Mortgage Loans	405.3
Originated Three Years before Last Fiscal Year
Financing Receivable, Credit Quality Indicator
Mortgage Loans	318.8
Originated Two Years before Last Fiscal Year
Financing Receivable, Credit Quality Indicator
Mortgage Loans	389.6
Originated in Fiscal Year before Latest Fiscal Year
Financing Receivable, Credit Quality Indicator
Mortgage Loans	365.9
Originated in Current Fiscal Year
Financing Receivable, Credit Quality Indicator
Mortgage Loans	182.9
AA Credit Rating
Financing Receivable, Credit Quality Indicator
Mortgage Loans	3.5		0
A Credit Rating
Financing Receivable, Credit Quality Indicator
Mortgage Loans	510		485.6
BBB Credit Rating
Financing Receivable, Credit Quality Indicator
Mortgage Loans	1,863		1,911.4
BB Credit Rating
Financing Receivable, Credit Quality Indicator
Mortgage Loans	39.4		0
B Credit Rating
Financing Receivable, Credit Quality Indicator
Mortgage Loans	16.2		0
Commercial Real Estate
Financing Receivable, Credit Quality Indicator
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	772
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	407.3
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	320.7
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	392
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	368.8
Financing Receivable, Year One, Originated, Current Fiscal Year	184.4
Financing Receivable, before Allowance for Credit Loss	2,445.2		$ 2,397
Financing Receivable, Allowance for Credit Loss	(13.1)
Commercial Real Estate | Loan to Value Ratio Below or Equal to 65 Percent
Financing Receivable, Credit Quality Indicator
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	598.5
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	257.5
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	139
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	77.8
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	82.8
Financing Receivable, Year One, Originated, Current Fiscal Year	37.2
Financing Receivable, before Allowance for Credit Loss	1,192.8
Financing Receivable, Allowance for Credit Loss	(3.4)	$ (2.8)
Commercial Real Estate | Loan To Value Ratio Above 65 To 75 Percent
Financing Receivable, Credit Quality Indicator
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	47.2
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	122.5
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	109.9
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	294.8
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	286
Financing Receivable, Year One, Originated, Current Fiscal Year	147.2
Financing Receivable, before Allowance for Credit Loss	1,007.6
Financing Receivable, Allowance for Credit Loss	(7.3)	(4.6)
Commercial Real Estate | Loan To Value Ratio Above 75 To 85 Percent
Financing Receivable, Credit Quality Indicator
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	78.7
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	27.3
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	37.9
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	13.3
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0
Financing Receivable, Year One, Originated, Current Fiscal Year	0
Financing Receivable, before Allowance for Credit Loss	157.2
Financing Receivable, Allowance for Credit Loss	(1.3)	(0.5)
Commercial Real Estate | Loan To Value Ratio Above 85 Percent
Financing Receivable, Credit Quality Indicator
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	47.6
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	33.9
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	6.1
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0
Financing Receivable, Year One, Originated, Current Fiscal Year	0
Financing Receivable, before Allowance for Credit Loss	87.6
Financing Receivable, Allowance for Credit Loss	(1.1)	$ (0.4)
Commercial Real Estate | Originated Five or More Years before Last Fiscal Year
Financing Receivable, Credit Quality Indicator
Financing Receivable, Allowance for Credit Loss	(2.4)
Commercial Real Estate | Originated Four Years before Last Fiscal Year
Financing Receivable, Credit Quality Indicator
Financing Receivable, Allowance for Credit Loss	(2)
Commercial Real Estate | Originated Three Years before Last Fiscal Year
Financing Receivable, Credit Quality Indicator
Financing Receivable, Allowance for Credit Loss	(1.9)
Commercial Real Estate | Originated Two Years before Last Fiscal Year
Financing Receivable, Credit Quality Indicator
Financing Receivable, Allowance for Credit Loss	(2.4)
Commercial Real Estate | Originated in Fiscal Year before Latest Fiscal Year
Financing Receivable, Credit Quality Indicator
Financing Receivable, Allowance for Credit Loss	(2.9)
Commercial Real Estate | Originated in Current Fiscal Year
Financing Receivable, Credit Quality Indicator
Financing Receivable, Allowance for Credit Loss	(1.5)
Commercial Real Estate | AA Credit Rating
Financing Receivable, Credit Quality Indicator
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	3.5
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0
Financing Receivable, Year One, Originated, Current Fiscal Year	0
Financing Receivable, before Allowance for Credit Loss	3.5
Commercial Real Estate | A Credit Rating
Financing Receivable, Credit Quality Indicator
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	240.3
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	119.5
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	56.3
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	60.2
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	16.9
Financing Receivable, Year One, Originated, Current Fiscal Year	18
Financing Receivable, before Allowance for Credit Loss	511.2
Commercial Real Estate | BBB Credit Rating
Financing Receivable, Credit Quality Indicator
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	482.6
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	287.8
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	253.9
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	331.8
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	351.9
Financing Receivable, Year One, Originated, Current Fiscal Year	166.4
Financing Receivable, before Allowance for Credit Loss	1,874.4
Commercial Real Estate | BB Credit Rating
Financing Receivable, Credit Quality Indicator
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	29.4
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	10.5
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0
Financing Receivable, Year One, Originated, Current Fiscal Year	0
Financing Receivable, before Allowance for Credit Loss	39.9
Commercial Real Estate | B Credit Rating
Financing Receivable, Credit Quality Indicator
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	16.2
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0
Financing Receivable, Year One, Originated, Current Fiscal Year	0
Financing Receivable, before Allowance for Credit Loss	$ 16.2

Mortgage Loans, Allowance for C

Mortgage Loans, Allowance for Credit Losses Rollforward (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)
Financing Receivable, Allowance for Credit Loss
Financing Receivable, Allowance for Credit Loss, Beginning Balance	$ 0
Financing Receivable, Allowance for Credit Loss, Ending Balance	13.1
Commercial Real Estate
Financing Receivable, Allowance for Credit Loss
Financing Receivable, Allowance for Credit Loss, Ending Balance	13.1
Commercial Real Estate | Loan to Value Ratio Below or Equal to 65 Percent
Financing Receivable, Allowance for Credit Loss
Financing Receivable, Credit Loss, Expense (Reversal)	0.6
Financing Receivable, Allowance for Credit Loss, Writeoff	0
Financing Receivable, Allowance for Credit Loss, Recovery	0
Financing Receivable, Allowance for Credit Loss, Ending Balance	3.4
Commercial Real Estate | Loan To Value Ratio Above 65 To 75 Percent
Financing Receivable, Allowance for Credit Loss
Financing Receivable, Credit Loss, Expense (Reversal)	2.7
Financing Receivable, Allowance for Credit Loss, Writeoff	0
Financing Receivable, Allowance for Credit Loss, Recovery	0
Financing Receivable, Allowance for Credit Loss, Ending Balance	7.3
Commercial Real Estate | Loan To Value Ratio Above 75 To 85 Percent
Financing Receivable, Allowance for Credit Loss
Financing Receivable, Credit Loss, Expense (Reversal)	0.8
Financing Receivable, Allowance for Credit Loss, Writeoff	0
Financing Receivable, Allowance for Credit Loss, Recovery	0
Financing Receivable, Allowance for Credit Loss, Ending Balance	1.3
Commercial Real Estate | Loan To Value Ratio Above 85 Percent
Financing Receivable, Allowance for Credit Loss
Financing Receivable, Credit Loss, Expense (Reversal)	0.7
Financing Receivable, Allowance for Credit Loss, Writeoff	0
Financing Receivable, Allowance for Credit Loss, Recovery	0
Financing Receivable, Allowance for Credit Loss, Ending Balance	1.1
Commercial Real Estate | Loan to Value Ratio Total
Financing Receivable, Allowance for Credit Loss
Financing Receivable, Credit Loss, Expense (Reversal)	4.8
Financing Receivable, Allowance for Credit Loss, Writeoff	0
Financing Receivable, Allowance for Credit Loss, Recovery	0
Financing Receivable, Allowance for Credit Loss, Ending Balance	$ 13.1

Investments Remaining Contractu

Investments Remaining Contractual Maturity of Security Lending Agreements (Details) - Overnight and Continuous - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
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	$ 17.6	$ 0
Securities Loaned and Securities Sold under Agreement to Repurchase, Gross Including Not Subject to Master Netting Arrangement	17.6	0
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
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
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	0.3	0
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	$ 16.8	$ 0

Investments Federal Home Loan B

Investments Federal Home Loan Bank Carrying Amount, Collateral Posted and Advances Received (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Federal Home Loan Bank Carrying Value of Common Stock, Collateral Posted and Advances
Federal Home Loan Bank Common Stock	$ 28.2	$ 18.5
Federal Home Loan Bank, Advances	312.2	0
Federal Home Loan Bank, Collateral Posted to FHLB	2,016.5	346.5
Fixed Maturity Securities
Federal Home Loan Bank Carrying Value of Common Stock, Collateral Posted and Advances
Federal Home Loan Bank, Collateral Posted to FHLB	944	182.1
Commercial Mortgage Loans
Federal Home Loan Bank Carrying Value of Common Stock, Collateral Posted and Advances
Federal Home Loan Bank, Collateral Posted to FHLB	$ 1,072.5	$ 164.4

Investments Schedule of Financi

Investments Schedule of Financial Instrument and Derivative Offsetting (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Offsetting Derivative Assets
Derivative Asset, Fair Value, Gross Asset	$ 19.8	$ 27.5
Derivative Liabilities Offsetting Derivative Assets in Balance Sheet	0	0
Net Derivative Assets Reported in Balance Sheet	19.8	27.5
Securities Received as Collateral on Derivative Assets	(10.1)	(4)
Cash Collateral from Counterparties	(8.7)	(23.5)
Derivative Assets Net of Collateral	1	0
Offsetting Securities Borrowed
Gross Securities Borrowed	96.6	176.4
Liabilities Offsetting Securities Borrowed in Balance Sheet	0	0
Net Securities Borrowed Reported in Balance Sheet	96.6	176.4
Securities Received as Collateral on Securities Borrowed	(79)	(176.4)
Cash Received as Collateral on Securities Borrowed	(17.6)	0
Securities Borrowed Net of Collateral	0	0
Offsetting Financial Assets
Gross Financial Assets	116.4	203.9
Financial Liabilities Offsetting Financial Assets in Balance Sheet	0	0
Net Financial Assets Reported in Balance Sheet	116.4	203.9
Securities Received as Collateral on Financial Assets	(89.1)	(180.4)
Cash Received as Collateral on Financial Assets	(26.3)	(23.5)
Financial Assets Net of Collateral	1	0
Offsetting Derivative Liabilities
Net Derivative Liabilities Reported in Balance Sheet	99.5	57.4
Offsetting Securities Loaned
Gross Securities Loaned	17.6
Assets Offsetting Securities Loaned in Balance Sheet	0
Net Securities Loaned Reported in Balance Sheet	17.6
Securities Given as Collateral on Securities Loaned	(17.6)
Cash Given as Collateral on Securities Loaned	0
Securities Loaned Net of Collateral	0
Offsetting Financial Liabilities
Gross Financial Liability	77.3
Financial Assets Offsetting Financial Liabilities in Balance Sheet	0
Net Financial Liabilities Reported in Balance Sheet	77.3
Securities Given as Collateral on Financial Liabilities	(76.6)
Cash Given as Collateral on Financial Liabilities	0
Financial Liabilities Net of Collateral	0.7
Over the Counter
Offsetting Derivative Liabilities
Gross Derivative Liability	59.7	34.6
Derivative Assets Offsetting Derivative Liabilities in Balance Sheet	0	0
Net Derivative Liabilities Reported in Balance Sheet	59.7	34.6
Securities Given as Collateral on Derivative Liabilities	(59)	(31.3)
Cash Collateral to counterparties	0	0
Derivative Liabilities Net of Collateral	$ 0.7	$ 3.3

Investments Investment Income (

Investments Investment Income (Detail) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Net Investment Income
Investment Income, Interest and Dividend										$ 2,403.7	$ 2,480.2	$ 2,502.4
Less Investment Expenses										30.6	32.1	35.2
Less Investment Income on PFA Assets										12.4	12.8	13.5
Net Investment Income		$ 593.5	$ 613.2	$ 569	$ 585	$ 616.3	$ 599.4	$ 624.9	$ 594.7	2,360.7	2,435.3	2,453.7
Fixed Maturity Securities
Net Investment Income
Investment Income, Interest and Dividend										2,164	2,213.6	2,239.7
Derivatives
Net Investment Income
Investment Income, Interest and Dividend										78.7	73.4	66.1
Mortgage Loans
Net Investment Income
Investment Income, Interest and Dividend										108.9	103.3	110.1
Policy Loans
Net Investment Income
Investment Income, Interest and Dividend										20	19.9	18.6
Perpetual Preferred Equity Securities
Net Investment Income
Investment Income, Interest and Dividend	[1]									(2.1)	5.4	(0.2)
Private Equity Partnerships
Net Investment Income
Investment Income, Interest and Dividend	[2]									19.8	31.7	36
Other Long-term Investments
Net Investment Income
Investment Income, Interest and Dividend										3.9	3.9	8.4
Short-term Investments
Net Investment Income
Investment Income, Interest and Dividend										$ 10.5	$ 29	$ 23.7
[1]	The net unrealized gain (loss) recognized in net investment income for the year ended December 31, 2020 related to perpetual preferred securities still held at December 31, 2020 was $(4.6) million. The net unrealized gain (loss) recognized in net investment income for the year ended December 31, 2019 related to perpetual preferred securities still held at December 31, 2019 was $3.3 million.
[2]	The net unrealized gain (loss) recognized in net investment income for the year ended December 31, 2020 related to private equity partnerships still held at December 31, 2020 was $(8.7) million. The net unrealized gain (loss) recognized in net investment income for the year ended December 31, 2019 related to private equity partnerships still held at December 31, 2019 was $6.8 million. See Note 2 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									12 Months Ended
	Dec. 31, 2020	[2]	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020		Dec. 31, 2019	Dec. 31, 2018
Fixed Maturity Securities
Gross Gains on Sales										$ 1,332.8	[1]	$ 22.9	$ 9.7
Gross Losses on Sales										(20.3)		(32.6)	(15.2)
Credit Losses										(53.6)		(25.3)	(17.5)
Mortgage Loans and Other Invested Assets
Gross Gains on Sales										1.9		4.6	0.5
Gross Losses on Sales										(0.3)		(0.3)	0
Impairment Loss										(36.6)		0	(1.4)
Credit Losses										(4.6)		0	0
Gain (Loss) on Embedded Derivative										(17)		8.3	(15.2)
All Other Derivatives										(2.5)		(0.1)	0.3
Foreign Currency Transactions										(0.7)		(0.7)	(0.7)
Net Realized Investment Gain (Loss)	$ 1,304.9		$ 4.4	$ 33.8	$ (144)	$ 9.2	$ (26.2)	$ (7.3)	$ 1.1	$ 1,199.1		$ (23.2)	$ (39.5)
[1]	Gross gains on sales of fixed maturity securities includes gains of $1,302.3 million as a result of the reinsurance transaction that we entered into during the fourth quarter of 2020. See Note 12 for further discussion.
[2]	Fourth quarter of 2020 net realized investment gain of $1,302.3 million before tax and $1,028.8 million after tax, related to the transfer of investments for the Closed Block individual disability reinsurance transaction.

Investments - Additional Inform

Investments - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2020USD ($)Integer	Dec. 31, 2019USD ($)Integer	Dec. 31, 2018USD ($)Integer
Schedule of Investments
Commitment to Fund Private Placement Fixed Maturity Securities	$ 21,000,000
Other Long-term Investments	960,200,000	$ 844,200,000
Unfunded Commitments	900,000
Financing Receivable, Allowance for Credit Losses	13,100,000	0
Accrued Investment Income	611,400,000	693,000,000
Foreclosed Real Estate Expense	0	0	$ 0
Average Recorded Investment of Impaired Mortgage Loans		600,000	2,300,000
Committments to Fund Commercial Mortgage Loans	11,400,000
Real Estate Investment Property, Net	106,300,000	90,500,000
Real Estate Investment Property, Accumulated Depreciation	97,700,000	49,800,000
Impairment of Real Estate	$ 36,600,000	0	$ 1,400,000
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	$ 96,600,000	176,400,000
Outstanding Repurchase Agreements	0	0
Off Balance Sheet Amount
Schedule of Investments
Cash Collateral for Borrowed Securities	17,600,000
Securities Received as Collateral	82,800,000	186,500,000
Commercial Real Estate
Schedule of Investments
Financing Receivable, before Allowance for Credit Loss	2,445,200,000	2,397,000,000
Financing Receivable, Allowance for Credit Losses	13,100,000
Accrued Investment Income	$ 8,000,000	$ 8,300,000
Financing Receivable, Modifications, Number of Contracts | Integer	0	0	1,000,000
Financing Receivable, Modifications, Pre-Modification Recorded Investment			$ 3,600,000
Provision for Loan and Lease Losses		$ 100,000	200,000
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	$ 0
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	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	776,800,000	675,100,000
Tax Credit Partnership | Variable Interest Entity, Not Primary Beneficiary
Schedule of Investments
Other Long-term Investments	29,300,000	58,400,000
Private Equity Partnerships | Variable Interest Entity, Not Primary Beneficiary
Schedule of Investments
Other Long-term Investments	747,500,000	$ 616,700,000
Investment Real Estate
Schedule of Investments
Impairment of Real Estate	$ 36,600,000		$ 600,000
External Credit Rating, Investment Grade
Schedule of Investments
Number of Fixed Maturity Securities in an Unrealized Loss Position	47
Number of Fixed Maturity Securities in an Unrealized Loss Position Continuously for Over One Year	5
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	13

Derivative Financial Instrume_3

Derivative Financial Instruments Nature and Amount of Collateral Received From and Posted To Our Derivative Counterparties (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Derivative
Cash Collateral from Counterparties	$ 8.7	$ 23.5
Carrying Value of Fixed Maturity Securities Posted as Collaterial to Counterparties	10.1	4
Cash
Derivative
Cash Collateral from Counterparties	8.7	24
Fixed Maturity Securities
Derivative
Carrying Value of Fixed Maturity Securities Posted as Collaterial to Counterparties	$ 54	$ 28.6

Notional Amounts for Each Categ

Notional Amounts for Each Category of Derivative Activity (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Derivative
Balance at beginning of period	$ 881.4	$ 799.2	$ 904.5
Additions	120	553.7	136.5
Terminations	257.3	471.5	241.8
Foreign Currency	0.3	0
Balance at end of period	744.4	881.4	799.2
Interest Rate Swaps | Receive Variable/Pay Fixed
Derivative
Balance at beginning of period	0	0	48
Additions	0	0	0
Terminations	0	0	48
Foreign Currency	0	0
Balance at end of period	0	0	0
Interest Rate Swaps | Receive Fixed/Pay Fixed
Derivative
Balance at beginning of period	611.1	538.2	536.5
Additions	113.6	171.3	78.1
Terminations	3.9	98.4	76.4
Balance at end of period	720.8	611.1	538.2
Interest Rate Swaps | Receive Fixed/Pay Variable
Derivative
Balance at beginning of period	250	250	250
Additions	0	0	0
Terminations	250	0	0
Balance at end of period	0	250	250
Credit Default Swaps | Credit Default Swaps
Derivative
Balance at beginning of period	11.4	11	70
Additions	0	0	11
Terminations	0	0	70
Foreign Currency	0.3	0.4
Balance at end of period	11.7	11.4	11
Forwards
Derivative
Balance at beginning of period	8.9	0	0
Additions	6.4	382.4	47.4
Terminations	3.4	373.1	47.4
Foreign Currency	0	(0.4)
Balance at end of period	$ 11.9	$ 8.9	$ 0

Derivative Financial Instrume_4

Derivative Financial Instruments Fair Value Hedges Carrying Amount of Hedged Assets and Liabilities and Cumulative Basis Adjustments (Details) - Interest Rate Swaps - Designated as Hedging Instrument - Fair Value Hedging - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Fixed Maturity Securities | Receive Fixed/Pay Fixed
Derivative Instruments and Hedging Activities Disclosures
Hedged Asset, Fair Value Hedge	$ 404.5	$ 239.4
Hedged Asset, Fair Value Hedge, Cumulative Increase (Decrease)	24.4	1.1
Long-term Debt | Receive Fixed/Pay Variable
Derivative Instruments and Hedging Activities Disclosures
Hedged Liability, Fair Value Hedge	0	(249.2)
Hedged Liability, Fair Value Hedge, Cumulative Increase (Decrease)	$ 0	$ 0.6

Location and Fair Values of Der

Location and Fair Values of Derivative Financial Instruments (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Derivative
Asset Derivatives Fair Value	$ 19.8	$ 27.5
Designated as Hedging Instrument | Other Long-term Investments
Derivative
Asset Derivatives Fair Value	19.7	27
Designated as Hedging Instrument | Other Long-term Investments | Fair Value Hedging
Derivative
Asset Derivatives Fair Value		7.6
Designated as Hedging Instrument | Other Long-term Investments | Foreign Exchange Contracts | Cash Flow Hedging
Derivative
Asset Derivatives Fair Value	16.4	19.4
Designated as Hedging Instrument | Other Long-term Investments | Foreign Exchange Contracts | Fair Value Hedging
Derivative
Asset Derivatives Fair Value	3.3	7.6
Designated as Hedging Instrument | Other Long-term Investments | Interest Rate Swaps | Fair Value Hedging
Derivative
Asset Derivatives Fair Value		0
Designated as Hedging Instrument | Other Liabilities
Derivative
Liability Derivatives Fair Value	35.4	12.2
Designated as Hedging Instrument | Other Liabilities | Fair Value Hedging
Derivative
Liability Derivatives Fair Value		5.6
Designated as Hedging Instrument | Other Liabilities | Foreign Exchange Contracts | Cash Flow Hedging
Derivative
Liability Derivatives Fair Value	9.4	6.6
Designated as Hedging Instrument | Other Liabilities | Foreign Exchange Contracts | Fair Value Hedging
Derivative
Liability Derivatives Fair Value	26	5
Designated as Hedging Instrument | Other Liabilities | Interest Rate Swaps | Fair Value Hedging
Derivative
Liability Derivatives Fair Value		0.6
Not Designated as Hedging Instrument | Other Long-term Investments
Derivative
Asset Derivatives Fair Value	0.1	0.5
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	0.5
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 Long-term Investments | Forwards
Derivative
Asset Derivatives Fair Value	0
Not Designated as Hedging Instrument | Other Liabilities
Derivative
Liability Derivatives Fair Value	64.1	45.2
Not Designated as Hedging Instrument | Other Liabilities | Foreign Exchange Contracts
Derivative
Liability Derivatives Fair Value	23.8	22.4
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	39.8	$ 22.8
Not Designated as Hedging Instrument | Other Liabilities | Forwards
Derivative
Liability Derivatives Fair Value	$ 0.5

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									12 Months Ended
	Dec. 31, 2020		Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Derivative Instruments, Gain (Loss)
Net Investment Income	$ 593.5		$ 613.2	$ 569	$ 585	$ 616.3	$ 599.4	$ 624.9	$ 594.7	$ 2,360.7	$ 2,435.3	$ 2,453.7
Net Realized Investment Gain (Loss)	$ 1,304.9	[1]	$ 4.4	$ 33.8	$ (144)	$ 9.2	$ (26.2)	$ (7.3)	$ 1.1	1,199.1	(23.2)	(39.5)
Interest and Debt Expense										188.2	177.4	167.3
Derivative, Gain (Loss) on Derivative, Net										2.5	0.1	(0.3)
Designated as Hedging Instrument | Interest Rate Swaps | Net Investment Income | Cash Flow Hedging
Derivative Instruments, Gain (Loss)
Net Investment Income										286.1	294.6	310.3
Derivative, Gain (Loss) on Derivative, Net										75.9	74.3	67.1
Designated as Hedging Instrument | Interest Rate Swaps | Net Investment Income | Fair Value Hedging
Derivative Instruments, Gain (Loss)
Net Investment Income										0	0	1
Derivative, Gain (Loss) on Derivative, Net										0	0	(0.5)
Designated as Hedging Instrument | Interest Rate Swaps | Net Realized Investment Gain (Loss) | Cash Flow Hedging
Derivative Instruments, Gain (Loss)
Net Realized Investment Gain (Loss)										397.7	(1.6)	0.1
Derivative, Gain (Loss) on Derivative, Net										32	9.3	(0.3)
Designated as Hedging Instrument | Interest Rate Swaps | Net Realized Investment Gain (Loss) | Fair Value Hedging
Derivative Instruments, Gain (Loss)
Net Realized Investment Gain (Loss)										(0.6)	(4.5)	0.1
Derivative, Gain (Loss) on Derivative, Net										0.6	4.5	(0.1)
Designated as Hedging Instrument | Interest Rate Swaps | Interest and Debt Expense | Cash Flow Hedging
Derivative Instruments, Gain (Loss)
Interest and Debt Expense										29.2	30.4	38.4
Derivative, Gain (Loss) on Derivative, Net										1.7	2.4	2.3
Designated as Hedging Instrument | Interest Rate Swaps | Interest and Debt Expense | Fair Value Hedging
Derivative Instruments, Gain (Loss)
Interest and Debt Expense										10.1	14.3	14.3
Derivative, Gain (Loss) on Derivative, Net										(0.9)	2.5	1.8
Designated as Hedging Instrument | Foreign Exchange Contracts | Net Investment Income | Cash Flow Hedging
Derivative Instruments, Gain (Loss)
Net Investment Income										12.1	14.8	18.1
Derivative, Gain (Loss) on Derivative, Net										2.5	(2)	(0.9)
Designated as Hedging Instrument | Foreign Exchange Contracts | Net Investment Income | Fair Value Hedging
Derivative Instruments, Gain (Loss)
Net Investment Income										7.1	2.9	0.6
Derivative, Gain (Loss) on Derivative, Net										2.8	1.9	0.5
Designated as Hedging Instrument | Foreign Exchange Contracts | Net Realized Investment Gain (Loss) | Cash Flow Hedging
Derivative Instruments, Gain (Loss)
Net Realized Investment Gain (Loss)										(0.1)	1.4	1.5
Derivative, Gain (Loss) on Derivative, Net										0.1	(1.4)	(1.5)
Designated as Hedging Instrument | Foreign Exchange Contracts | Net Realized Investment Gain (Loss) | Fair Value Hedging
Derivative Instruments, Gain (Loss)
Net Realized Investment Gain (Loss)										23.3	3.8	(2.7)
Derivative, Gain (Loss) on Derivative, Net										(23.3)	(3.8)	2.7
Designated as Hedging Instrument | Foreign Exchange Contracts | Interest and Debt Expense | Cash Flow Hedging
Derivative Instruments, Gain (Loss)
Interest and Debt Expense										0	0	0
Derivative, Gain (Loss) on Derivative, Net										0	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	$ 0
Derivative, Gain (Loss) on Derivative, Net										$ 0
[1]	Fourth quarter of 2020 net realized investment gain of $1,302.3 million before tax and $1,028.8 million after tax, related to the transfer of investments for the Closed Block individual disability reinsurance transaction.

Location of Gains and Losses on

Location of Gains and Losses on Derivative Instruments Designated as Cash Flow Hedging Instruments (Detail) - Designated as Hedging Instrument - Cash Flow Hedging - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in OCI on Derivatives (Effective Portion)	$ (5.4)	$ (6.2)	$ 16.8
Interest Rate Swaps
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in OCI on Derivatives (Effective Portion)	0	(0.1)	(0.1)
Foreign Exchange Contracts
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in OCI on Derivatives (Effective Portion)	$ (5.4)	$ (6.1)	$ 16.9

Gains and Losses on Derivatives

Gains and Losses on Derivatives Not Designated as Hedging Instruments (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Derivative Instruments, Gain (Loss)
Net Gain (Loss) on Derivatives	$ (2.5)	$ (0.1)	$ 0.3
Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss)
Net Gain (Loss) on Derivatives	(19.5)	8.2	(14.9)
Credit Default Swaps | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss)
Net Gain (Loss) on Derivatives	(0.5)	(0.1)	(0.3)
Interest Rate Swaps | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss)
Net Gain (Loss) on Derivatives	0	0	(0.3)
Foreign Exchange Contracts | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss)
Net Gain (Loss) on Derivatives	(2)	0	0.9
Embedded Derivative in Modified Coinsurance Arrangement | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss)
Net Gain (Loss) on Derivatives	$ (17)	$ 8.3	$ (15.2)

Derivative Financial Instrume_6

Derivative Financial Instruments - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Derivative
Aggregate fair value of all derivative instruments with credit risk-related contingent features in a liability position	$ 59.7	$ 34.6
Additions	120	553.7	$ 136.5
Approximate amount of net deferred gains on derivative instruments expected to be amortized during the next twelve months	60.3
Notional Amount Of Derivatives Terminations	257.3	471.5	241.8
Component of Derivative Gain (Loss) Excluded from the Assessment of Hedge Effectiveness	(1.8)	2	2.5
Discontinued Hedge Accounting Due to Instrument No Longer Qualifying as Fair Value Hedge	0	0
Derivative, Notional Amount	744.4	881.4	799.2	$ 904.5
Interest Rate Cash Flow Hedge Gain (Loss) Reclassified to Earnings, Net	30.7
Credit Risk Contract | Credit Default Swaps
Derivative
Additions	0	0	11
Notional Amount Of Derivatives Terminations	0	0	70
Derivative, Notional Amount	11.7	11.4	11	70
Credit Risk Contract | Credit Default Swaps | Not Designated as Hedging Instrument
Derivative
Derivative, Notional Amount	11.7	11.4
Forwards
Derivative
Additions	6.4	382.4	47.4
Notional Amount Of Derivatives Terminations	3.4	373.1	47.4
Derivative, Notional Amount	11.9	8.9	0	0
Forwards | Not Designated as Hedging Instrument
Derivative
Derivative, Notional Amount	11.9	8.9
Forwards | Cash Flow Hedging | Designated as Hedging Instrument
Derivative
Additions		350
Derivative, Loss on Derivative		0.5
Derivative, Cost of Hedge		5.3
Credit Exposure
Derivative
Credit Exposure on Derivatives	0.7	0
Receive Fixed/Pay Fixed | Interest Rate Swaps
Derivative
Additions	113.6	171.3	78.1
Notional Amount Of Derivatives Terminations	3.9	98.4	76.4
Derivative, Notional Amount	720.8	611.1	538.2	536.5
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	213.5
Receive Fixed/Pay Fixed | Interest Rate Swaps | Fair Value Hedging | Designated as Hedging Instrument
Derivative
Derivative, Notional Amount	362.4	249.4
Receive Variable/Pay Fixed | Interest Rate Swaps
Derivative
Additions	0	0	0
Notional Amount Of Derivatives Terminations	0	0	48
Derivative, Notional Amount	0	0	0	48
Receive Fixed/Pay Variable | Interest Rate Swaps
Derivative
Additions	0	0	0
Notional Amount Of Derivatives Terminations	250	0	0
Derivative, Notional Amount	$ 0	250	$ 250	$ 250
Receive Fixed/Pay Variable | Interest Rate Swaps | Cash Flow Hedging | Designated as Hedging Instrument
Derivative
Derivative, Notional Amount		$ 250

Schedule of Accumulated Other C

Schedule of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 374.2	$ 37.3	$ (814.2)		$ 127.5
Other Comprehensive Income (Loss) Before Reclassifications	359.4	865.5	(910.6)
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	22.5	14	13.6
Total Other Comprehensive Income (Loss)	336.9	851.5	(924.2)
Accounting Standards Update 2016-01
Accumulated Other Comprehensive Income (Loss)
Cumulative Effect, Period of Adoption, Adjustment				$ (17.5)
Net Unrealized Gain (Loss) on Securities
Accumulated Other Comprehensive Income (Loss)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	1,067.7	615.9	(312.4)		607.8
Other Comprehensive Income (Loss) Before Reclassifications	405.6	894.1	(920.3)
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	(46.2)	(34.2)	(17.6)
Total Other Comprehensive Income (Loss)	451.8	928.3	(902.7)
Net Unrealized Gain (Loss) on Securities | Accounting Standards Update 2016-01
Accumulated Other Comprehensive Income (Loss)
Cumulative Effect, Period of Adoption, Adjustment				(17.5)
Net Gain on Hedges
Accumulated Other Comprehensive Income (Loss)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	97.8	187.8	250.6		282.3
Other Comprehensive Income (Loss) Before Reclassifications	(5.7)	(0.2)	16.8
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	84.3	62.6	48.5
Total Other Comprehensive Income (Loss)	(90)	(62.8)	(31.7)
Net Gain on Hedges | Accounting Standards Update 2016-01
Accumulated Other Comprehensive Income (Loss)
Cumulative Effect, Period of Adoption, Adjustment				0
Foreign Currency Translation Adjustment
Accumulated Other Comprehensive Income (Loss)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(261.3)	(281.6)	(305.2)		(254.5)
Other Comprehensive Income (Loss) Before Reclassifications	20.3	23.6	(50.7)
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	0	0	0
Total Other Comprehensive Income (Loss)	20.3	23.6	(50.7)
Foreign Currency Translation Adjustment | Accounting Standards Update 2016-01
Accumulated Other Comprehensive Income (Loss)
Cumulative Effect, Period of Adoption, Adjustment				0
Unrecognized Pension and Postretirement Benefit Costs
Accumulated Other Comprehensive Income (Loss)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(530)	(484.8)	(447.2)		$ (508.1)
Other Comprehensive Income (Loss) Before Reclassifications	(60.8)	(52)	43.6
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	(15.6)	(14.4)	(17.3)
Total Other Comprehensive Income (Loss)	$ (45.2)	$ (37.6)	$ 60.9
Unrecognized Pension and Postretirement Benefit Costs | Accounting Standards Update 2016-01
Accumulated Other Comprehensive Income (Loss)
Cumulative Effect, Period of Adoption, Adjustment				$ 0

Schedule of Components of Unrea

Schedule of Components of Unrealized Gain (Loss) on Securities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jan. 01, 2018
Change in Components of Net Unrealized Gain on Securities
Change in Net Unrealized Gain on Securities	$ 983	$ 2,870.9	$ (2,314.5)
Fixed Maturity Securities
Change in Components of Net Unrealized Gain on Securities
Beginning of Year Balance	6,364.4	2,736.5	5,677.3
Change in Net Unrealized Gain on Securities	1,233.2	3,627.9	(2,928.7)
Accumulated Other Comprehensive Income (Loss), Debt Securities, Available-for-sale, Adjustment, after Tax	6,364.4	2,736.5	5,677.3	$ 5,665.2
End of Year Balance	7,597.6	6,364.4	2,736.5
Other Investments
Change in Components of Net Unrealized Gain on Securities
Beginning of Year Balance	0	0	14.4
Change in Net Unrealized Gain on Securities	0	0	0
Accumulated Other Comprehensive Income (Loss), Debt Securities, Available-for-sale, Adjustment, after Tax	0	0	14.4	0
End of Year Balance	0	0	0
Deferred Acquisition Costs
Change in Components of Net Unrealized Gain on Securities
Beginning of Year Balance	(62.7)	(27.9)	(51.4)
Change in Net Unrealized Gain on Securities	(22.4)	(34.8)	23.5
Accumulated Other Comprehensive Income (Loss), Debt Securities, Available-for-sale, Adjustment, after Tax	(62.7)	(27.9)	(51.4)	(51.4)
End of Year Balance	(85.1)	(62.7)	(27.9)
Reserve for Future Policy and Contract Benefits
Change in Components of Net Unrealized Gain on Securities
Beginning of Year Balance	(5,803.1)	(3,220.3)	(5,094.7)
Change in Net Unrealized Gain on Securities	(422.5)	(2,582.8)	1,874.4
Accumulated Other Comprehensive Income (Loss), Debt Securities, Available-for-sale, Adjustment, after Tax	(5,803.1)	(3,220.3)	(5,094.7)	(5,094.7)
End of Year Balance	(6,225.6)	(5,803.1)	(3,220.3)
Reinsurance Recoverable
Change in Components of Net Unrealized Gain on Securities
Beginning of Year Balance	424.7	261.4	375.8
Change in Net Unrealized Gain on Securities	(224.5)	163.3	(114.4)
Accumulated Other Comprehensive Income (Loss), Debt Securities, Available-for-sale, Adjustment, after Tax	424.7	261.4	375.8	375.8
End of Year Balance	200.2	424.7	261.4
Income Tax
Change in Components of Net Unrealized Gain on Securities
Beginning of Year Balance	(307.4)	(62.1)	(313.6)
Change in Net Unrealized Gain on Securities	(112)	(245.3)	242.5
Accumulated Other Comprehensive Income (Loss), Debt Securities, Available-for-sale, Adjustment, after Tax	(307.4)	(62.1)	(313.6)	(304.6)
End of Year Balance	(419.4)	(307.4)	(62.1)
Net Unrealized Gain (Loss) on Securities
Change in Components of Net Unrealized Gain on Securities
Beginning of Year Balance	615.9	(312.4)	607.8
Change in Net Unrealized Gain on Securities	451.8	928.3	(902.7)
Accumulated Other Comprehensive Income (Loss), Debt Securities, Available-for-sale, Adjustment, after Tax	615.9	(312.4)	607.8	$ 590.3
End of Year Balance	$ 1,067.7	$ 615.9	$ (312.4)

Schedule of Reclassifications O

Schedule of Reclassifications Out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended													12 Months Ended
	Dec. 31, 2020		Sep. 30, 2020		Jun. 30, 2020		Mar. 31, 2020	Dec. 31, 2019		Sep. 30, 2019		Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Benefits and Change in Reserves for Future Benefits														$ (8,972.9)	$ (7,496.2)	$ (8,020.4)
Net Investment Income	$ 593.5		$ 613.2		$ 569		$ 585	$ 616.3		$ 599.4		$ 624.9	$ 594.7	2,360.7	2,435.3	2,453.7
Interest and Debt Expense														(188.2)	(177.4)	(167.3)
Other Expenses														(996.6)	(943.6)	(891.2)
Income Before Income Tax	124.7	[1],[2],[3],[4]	299.6	[5]	337.6	[6]	202.1	377.4	[7]	299.4	[8]	352	353.3	964	1,382.1	627.8
Income Tax Expense (Benefit)														171	281.8	104.4
Net Income	$ 135.4	[1],[2],[3],[4],[9]	$ 231.1	[5]	$ 265.5	[6]	$ 161	$ 296.2	[7]	$ 242	[8]	$ 281.2	$ 280.9	793	1,100.3	523.4
Reclassification out of Accumulated Other Comprehensive Income | Net Unrealized Gain (Loss) on Securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Net Realized Investment Gain (Loss), Excluding Other-Than-Temporary Impairment Loss on Fixed Maturity Securities														1,279.7	(18)	(4.8)
Other-Than-Temporary Impairment Loss														(53.6)	(25.3)	(17.5)
Benefits and Change in Reserves for Future Benefits														(1,284.5)	0	0
Income Before Income Tax														(58.4)	(43.3)	(22.3)
Income Tax Expense (Benefit)														(12.2)	(9.1)	(4.7)
Net Income														(46.2)	(34.2)	(17.6)
Reclassification out of Accumulated Other Comprehensive Income | Net Gain on Hedges
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Income Before Income Tax														106.7	79.3	61.4
Income Tax Expense (Benefit)														22.4	16.7	12.9
Net Income														84.3	62.6	48.5
Reclassification out of Accumulated Other Comprehensive Income | Net Gain on Hedges | Interest Rate Swaps
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Net Realized Investment Gain (Loss), Excluding Other-Than-Temporary Impairment Loss on Fixed Maturity Securities														32	8.8	0.2
Net Investment Income														74.1	73.6	65.9
Interest and Debt Expense														(1.5)	(2.1)	(2.1)
Reclassification out of Accumulated Other Comprehensive Income | Net Gain on Hedges | Foreign Exchange Contracts
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Net Realized Investment Gain (Loss), Excluding Other-Than-Temporary Impairment Loss on Fixed Maturity Securities														0.1	(1.3)	(1.5)
Net Investment Income														2	0.8	(1.1)
Reclassification out of Accumulated Other Comprehensive Income | Net Gain on Hedges | Forwards
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Interest and Debt Expense														0	(0.5)	0
Reclassification out of Accumulated Other Comprehensive Income | Net Actuarial Loss
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Other Expenses														(19.8)	(18.6)	(22.3)
Reclassification out of Accumulated Other Comprehensive Income | Prior Service Credit
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Other Expenses														0.1	0.2	0.2
Reclassification out of Accumulated Other Comprehensive Income | Unrecognized Pension and Postretirement Benefit Costs
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Income Before Income Tax														(19.8)	(18.4)	(22.1)
Income Tax Expense (Benefit)														(4.2)	(4)	(4.8)
Net Income														(15.6)	(14.4)	(17.3)
Reclassification out of Accumulated Other Comprehensive Income | Curtailment Gain
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Other Expenses														$ (0.1)	$ 0	$ 0
[1]	Fourth quarter of 2020 amortization of the cost of reinsurance related to the Closed Block individual disability reinsurance transaction of $2.6 million before tax and $2.0 million after tax.
[2]	Fourth quarter of 2020 impacts from the Closed Block individual disability reinsurance transaction of $1,305.5 million before tax and $1,031.3 million after tax.
[3]	Fourth quarter of 2020 net realized investment gain of $1,302.3 million before tax and $1,028.8 million after tax, related to the transfer of investments for the Closed Block individual disability reinsurance transaction.
[4]	Fourth quarter of 2020 reserve increases of $151.5 million and $17.5 million before tax and $119.7 million and $13.8 million after tax related to long-term care and group pension, respectively.
[5]	Third quarter of 2020 costs related to organizational design update of $23.3 million before tax and $18.6 million after tax.
[6]	Second quarter of 2020 impairment on ROU asset related to an operating lease for office space that we do not plan to continue using to support our general operations of $12.7 million before tax and $10.0 million after tax.
[7]	Fourth quarter of 2019 cost related to the early retirement of debt of $2.1 million before tax and $1.7 million after tax.
[8]	Third quarter of 2019 cost related to the early retirement of debt of $25.2 million before tax and $19.9 million after tax.
[9]	Fourth quarter of 2020 net tax benefit from the Closed Block individual disability reinsurance transaction of $36.5 million.

Liability for Unpaid Claims a_3

Liability for Unpaid Claims and Claims Adjustment Expense (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense
Balance at January 1	$ 23,076.7	$ 23,149	$ 23,222
Less Reinsurance Recoverable	2,246.8	2,227.3	2,182
Net Balance at January 1	20,829.9	20,921.7	21,040
Incurred Related to
Current Year	6,327.8	6,113.2	5,832.3
Paid Related to
Current Year	(2,727)	(2,532.4)	(2,354.7)
Prior Years	(4,430.3)	(4,511)	(4,428.8)
Total Paid	(7,157.3)	(7,043.4)	(6,783.5)
Reserves Ceded Pursuant to Reinsurance Transaction	(6,141.5)	0	0
Net Balance at December 31	15,801.3	20,829.9	20,921.7
Plus Reinsurance Recoverable	8,378.9	2,246.8	2,227.3
Balance at December 31	24,180.2	23,076.7	23,149
Amount Related to Interest
Incurred Related to
Prior Years	997.8	1,036.5	1,049.8
Incurred Claims
Incurred Related to
Prior Years	878.7	(274.1)	(106.2)
Foreign Currency
Incurred Related to
Prior Years	65.9	76	(110.7)
Operating Expense
Incurred Related to
Total Incurred	$ 8,270.2	$ 6,951.6	$ 6,665.2

Reconciliation of Policy and Co

Reconciliation of Policy and Contract Benefits and Reserves for Future Policy and Contract Benefits (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Insurance [Abstract]
Policy and Contract Benefits	$ 1,855.4	$ 1,745.5	$ 1,695.7
Reserves for Future Policy and Contract Benefits	49,653	47,780.1	44,841.9
Total Policy and Contract Benefits and Reserves for Future Policy and Contract Benefits	51,508.4	49,525.6	46,537.6
Life Reserves for Future Policy and Contract Benefits	8,371.7	8,435.7	8,330.9
Accident and Health Active Life Reserves	12,730.9	12,210.1	11,837.4
Adjustment Related to Unrealized Investment Gains and Losses	6,225.6	5,803.1	3,220.3
Liability for Unpaid Claims and Claim Adjustment Expense	$ 24,180.2	$ 23,076.7	$ 23,149	$ 23,222

Liability for Unpaid Claims - A

Liability for Unpaid Claims - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 16, 2020	Dec. 31, 2017
Liability for Unpaid Claims and CAE Narrative Information
Long-term Care Reserve Increase, Before Tax	$ 151.5		$ 750.8
Reinsurance Recoverables, Incurred but Not Reported Claims	8,378.9	$ 2,246.8	2,227.3		$ 2,182
Benefits and Change in Reserves for Future Benefits	8,972.9	7,496.2	8,020.4
Closed Block Individual Disability Reinsurance Transaction
Liability for Unpaid Claims and CAE Narrative Information
Reinsurance Recoverables, Incurred but Not Reported Claims	6,141.5			$ 6,141.5
Reclassification out of Accumulated Other Comprehensive Income | Net Unrealized Gain (Loss) on Securities
Liability for Unpaid Claims and CAE Narrative Information
Benefits and Change in Reserves for Future Benefits	1,284.5	$ 0	0
Claim Reserve
Liability for Unpaid Claims and CAE Narrative Information
Long-term Care Reserve Increase, Before Tax	$ 7		$ 236

Income Tax Expense (Benefit) (D

Income Tax Expense (Benefit) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax [Abstract]
Income Tax Expense	$ 171	$ 281.8	$ 104.4
Other Comprehensive Income (Loss), Tax
Change in Net Unrealized Gain on Securities Before Adjustment	250.2	757	(614.2)
Change in Adjustment to Deferred Acquisition Costs and Reserves for Future Policy and Contract Benefits, Net of Reinsurance	(138.2)	(511.7)	371.7
Change in Net Gain on Hedges	(23.8)	(17)	(8.2)
Change in Foreign Currency Translation Adjustment	(4.3)	0.2	(0.6)
Change in Unrecognized Pension and Postretirement Benefit Costs	(34.8)	(9.3)	17
Total	$ 220.1	$ 501	$ (129.9)

Reconciliation of income tax co

Reconciliation of income tax computed at US Federal tax rates (Detail)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax [Abstract]
Statutory Income Tax	21.00%	21.00%	21.00%
Net Operating Loss Carryback	(3.80%)	0.00%	0.00%
Deemed Repatriation Tax on Foreign Earnings and Profit	0.00%	0.00%	1.80%
Tax Exempt Income	(0.80%)	(0.50%)	(1.30%)
Tax Credits	(1.30%)	(1.10%)	(2.40%)
Policyholder Reserves	0.70%	0.00%	(2.40%)
Other Items, Net	1.90%	1.00%	(0.10%)
Effective Tax	17.70%	20.40%	16.60%

Schedule of deferred income tax

Schedule of deferred income tax assets and liabilities (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Income Tax [Abstract]
Deferred Tax Asset, Reserves	$ 1,279.6	$ 1,154.6
Deferred Tax Asset, Employee Benefits	218.7	201.6
Deferred Tax Asset, Other	52.9	19.4
Deferred Tax Assets, Gross, Total	1,551.2	1,375.6
Less: Valuation Allowance	14.5	28.3
Deferred Tax Assets, Net of Valuation Allowance, Total	1,536.7	1,347.3
Deferred Tax Liabilities for Deferred Acquisition Cost	185.5	115.6
Deferred Tax Liabilities for Fixed Assets	74.7	58.5
Deferred Tax Liabilities on Invested Assets	1,443.5	1,213.7
Deferred Tax Liabilities on Cost of Reinsurance	180.4	10.8
Deferred Tax Liability, Other	68.7	44.1
Gross Deferred Tax Liability	1,952.8	1,442.7
Deferred Tax Liabilities, Net, Total	$ 416.1	$ 95.4

Schedule of Income subject to d

Schedule of Income subject to domestic and foreign taxation (Detail) - USD ($) $ in Millions	3 Months Ended													12 Months Ended
	Dec. 31, 2020	[1],[2],[3],[4]	Sep. 30, 2020	[5]	Jun. 30, 2020	[6]	Mar. 31, 2020	Dec. 31, 2019	[7]	Sep. 30, 2019	[8]	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax [Abstract]
Income Before Tax, Domestic														$ 924.7	$ 1,289.5	$ 492.6
Income Before Tax, Foreign														39.3	92.6	135.2
Income Before Income Tax	$ 124.7		$ 299.6		$ 337.6		$ 202.1	$ 377.4		$ 299.4		$ 352	$ 353.3	964	1,382.1	627.8
Current Tax Expense (Benefit), Domestic														(98.4)	273.6	194.6
Current State and Local Tax Expense (Benefit)														1.5	1.3	(0.6)
Current Tax Expense (Benefit), Foreign														(19.7)	(0.1)	33.4
Income Tax (Benefit) - Current														(116.6)	274.8	227.4
Deferred Tax Expense (Benefit), Federal														250.5	(9.5)	(114.6)
Deferred State and Local Income Tax Expense (Benefit)														1	(0.1)	(0.2)
Deferred Tax Expense (Benefit), Foreign														36.1	16.6	(8.2)
Deferred Income Tax Expense (Benefit)														287.6	7	(123)
Income Tax Expense														$ 171	$ 281.8	$ 104.4
[1]	Fourth quarter of 2020 amortization of the cost of reinsurance related to the Closed Block individual disability reinsurance transaction of $2.6 million before tax and $2.0 million after tax.
[2]	Fourth quarter of 2020 impacts from the Closed Block individual disability reinsurance transaction of $1,305.5 million before tax and $1,031.3 million after tax.
[3]	Fourth quarter of 2020 net realized investment gain of $1,302.3 million before tax and $1,028.8 million after tax, related to the transfer of investments for the Closed Block individual disability reinsurance transaction.
[4]	Fourth quarter of 2020 reserve increases of $151.5 million and $17.5 million before tax and $119.7 million and $13.8 million after tax related to long-term care and group pension, respectively.
[5]	Third quarter of 2020 costs related to organizational design update of $23.3 million before tax and $18.6 million after tax.
[6]	Second quarter of 2020 impairment on ROU asset related to an operating lease for office space that we do not plan to continue using to support our general operations of $12.7 million before tax and $10.0 million after tax.
[7]	Fourth quarter of 2019 cost related to the early retirement of debt of $2.1 million before tax and $1.7 million after tax.
[8]	Third quarter of 2019 cost related to the early retirement of debt of $25.2 million before tax and $19.9 million after tax.

Unrecognized tax benefits (Deta

Unrecognized tax benefits (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax [Abstract]
Balance at Beginning of Year	$ 241	$ 262.2	$ 1.4
Decreases for Tax Positions Related to Prior Years	(21)	(21.1)
Increases for Tax Positions Related to Prior Years			261.5
Lapse of the Applicable Statute of Limitations	(0.3)	(0.1)	(0.7)
Balance at End of Year	219.7	241	262.2
Less Tax Attributable to Temporary Items Included Above	(105.9)	(127.1)	(148.2)
Total Unrecognized Tax Benefits that if Recognized Would Affect the Effective Tax Rate	$ 113.8	$ 113.9	$ 114

Income Tax Additional Informati

Income Tax Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Federal Income Tax Note
Tax Cuts and Jobs Act, Measurement Period Adjustment, Income Tax Expense (Benefit)		$ 11.5
Income Taxes Receivable, Net Operating Loss, CARES Act	$ 36.5
Tax Cuts and Jobs Act of 2017, Complete Accounting, Undistributed Accumulated Earnings of Foreign Subsidiary for which Unrecognized Deferred Tax Liabilities Have Not Been Recorded	700
Increases for Tax Positions Related to Prior Years			$ 261.5
Less Tax Attributable to Temporary Items Included Above	(105.9)	(127.1)	(148.2)
Unrecognized Tax Benefits, Interest on Income Taxes Expense	7.8	12.8
Unrecognized Tax Benefits, Interest on Income Taxes Accrued	20.6	12.8
Valuation Allowance on Deferred Tax Assets	14.5	28.3
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	(13.8)	9.9
Income Taxes Paid, Net	200	35.1	$ 139.7
Tax Year 2017
Federal Income Tax Note
Increases for Tax Positions Related to Prior Years		$ 261.1
Foreign Tax Authority | Her Majesty's Revenue and Customs (HMRC)
Federal Income Tax Note
Tax Expense for Revaluation of Tax Assets and Liabilities due to Finance Bill 2019-21	9.3
U.S. Federal | Subsidiary Return
Federal Income Tax Note
Operating Loss Carryforwards	0.6
State and Local Jurisdiction
Federal Income Tax Note
Operating Loss Carryforwards	$ 191

Debt Schedule (Detail)

Debt Schedule (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument
Long-term Debt, Excluding Current Maturities	$ 3,345.7	$ 2,926.9
Debt Instrument, Unamortized Premium (Discount), Net	6	8.4
Debt Issuance Costs, Noncurrent, Net	(34.8)	(35.4)
Short-term debt	0	399.7
Debt Issuance Costs, Current, Net	0	(0.3)
Long-term Debt	3,345.7	3,326.6
Short-term Debt, outstanding principal	0
Fair Value Hedge Adjustment, LT Debt
Debt Instrument
Long-term Debt, Excluding Current Maturities	0	(0.6)
Secured Notes Issued in 2007 | Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	0	80
Notes Issued in 1998 with 2028 Maturity Date | Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	335.8	335.8
Notes Issued in 2002 | Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	39.5	39.5
Notes Issued in 2010 | Senior Notes
Debt Instrument
Short-term Debt, outstanding principal		400
Notes Payable due 2042 | Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	500	500
Notes Issued in 2014 | Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	350	350
Notes Issued in 2015 | Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	275	275
Notes Issued in 2019 | Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	400	400
Notes Issued in 2019 due 2049 | Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	450	450
Notes Issued 1990 to 1996 | Medium-term Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	20.5	20.5
Notes Issued in 1998 with 2038 Maturity Date | Junior Subordinated Debt
Debt Instrument
Long-term Debt, Excluding Current Maturities	203.7	203.7
Notes Issued in 2018 with a 2058 Maturity Date | Junior Subordinated Debt
Debt Instrument
Long-term Debt, Excluding Current Maturities	300	300
Notes Issued in 2020 due 2025 | Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	$ 500	$ 0

Debt - Additional Information (

Debt - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2007	Dec. 31, 1998	Dec. 31, 2017
Debt Additional Information
Repayments of Principal in 2023	$ 2,000,000
Repayments of Principal in 2024	350,000,000
Repayments of Principal in 2025	775,000,000
Repayments of Principal Thereafter	2,247,500,000
Derivative, Notional Amount	$ 744,400,000	$ 881,400,000	$ 799,200,000			$ 904,500,000
Unum Group Percentage Ownership of Provident Financing Trust	100.00%
Cost Related to Early Retirement of Debt	$ 0	27,300,000	0
Interest Paid, Including Capitalized Interest, Operating and Investing Activities	178,100,000	172,900,000	167,300,000
Notional Amount Of Derivatives Terminations	257,300,000	471,500,000	241,800,000
Parent Company
Debt Additional Information
Repayments of Principal in 2023	2,000,000
Repayments of Principal in 2024	350,000,000
Repayments of Principal in 2025	775,000,000
Repayments of Principal Thereafter	$ 2,247,500,000
Unum Group Percentage Ownership of Provident Financing Trust	100.00%
Cost Related to Early Retirement of Debt	$ 0	27,300,000	0
Interest Paid, Including Capitalized Interest, Operating and Investing Activities	176,600,000	$ 168,400,000	$ 161,400,000
Parent Company | Five-year Unsecured Revolving Credit Facility
Debt Additional Information
Line of Credit Facility, Maximum Borrowing Capacity	500,000,000
Letters of Credit Outstanding	0
Parent Company | Three-year Unsecured Revolving Credit Facility
Debt Additional Information
Line of Credit Facility, Maximum Borrowing Capacity	100,000,000
Letters of Credit Outstanding	$ 0
Notes Issued in 2019 due 2049 | Senior Notes
Debt Additional Information
Stated Interest Rate of Debt		4.50%
Proceeds from Issuance of Debt		$ 450,000,000
Notes Issued in 2019 due 2049 | Senior Notes | Parent Company
Debt Additional Information
Stated Interest Rate of Debt		4.50%
Proceeds from Issuance of Debt		$ 450,000,000
Notes Issued in 2019 | Senior Notes
Debt Additional Information
Stated Interest Rate of Debt		4.00%
Proceeds from Issuance of Debt		$ 400,000,000
Notes Issued in 2019 | Senior Notes | Parent Company
Debt Additional Information
Stated Interest Rate of Debt		4.00%
Proceeds from Issuance of Debt		$ 400,000,000
Notes Issued in 1998 with 2018 Maturity Date | Parent Company
Debt Additional Information
Stated Interest Rate of Debt			7.00%
Notes Issued in 1998 with 2018 Maturity Date | Senior Notes | Parent Company
Debt Additional Information
Stated Interest Rate of Debt			7.00%
Notes Issued in 2018 with a 2058 Maturity Date | Junior Subordinated Debt
Debt Additional Information
Stated Interest Rate of Debt			6.25%
Proceeds from Issuance of Debt			$ 300,000,000
Notes Issued in 2018 with a 2058 Maturity Date | Junior Subordinated Debt | Parent Company
Debt Additional Information
Stated Interest Rate of Debt			6.25%
Proceeds from Issuance of Debt			$ 300,000,000
Notes Issued in 1998 with 2038 Maturity Date | Junior Subordinated Debt
Debt Additional Information
Proceeds from Issuance of Senior Long-term Debt					$ 300,000,000
Stated Interest Rate of Debt	7.405%
Liquidation value per capital security	$ 1,000
Notes Issued in 1998 with 2038 Maturity Date | Junior Subordinated Debt | Parent Company
Debt Additional Information
Stated Interest Rate of Debt	7.405%	7.405%
Proceeds from Issuance of Debt					$ 300,000,000
Liquidation value per capital security	$ 1,000
Capital Securities Notes Payable Due 2038
Debt Additional Information
Extinguishment of Debt, Amount		$ 22,800,000
Stated Interest Rate of Debt		7.405%
Capital Securities Notes Payable Due 2038 | Parent Company
Debt Additional Information
Extinguishment of Debt, Amount	$ 22,800,000
Notes 5.625 Due 2020
Debt Additional Information
Debt Instrument, Repurchased Face Amount	400,000,000
4.500% Senior Notes due 2025 | Senior Notes
Debt Additional Information
Proceeds from Issuance of Debt	$ 500,000,000
Notes Issued in 2020 due 2025 | Senior Notes | Parent Company
Debt Additional Information
Stated Interest Rate of Debt	4.50%
Proceeds from Issuance of Debt	$ 500,000,000
Notes Issued in 2010 | Senior Notes | Parent Company
Debt Additional Information
Stated Interest Rate of Debt	5.625%
Secured Notes Issued in 2007 | Senior Notes
Debt Additional Information
Extinguishment of Debt, Amount	$ 35,000,000
Medium-term Notes | Medium Term Notes Payable Due 2028
Debt Additional Information
Extinguishment of Debt, Amount		$ 30,300,000
Stated Interest Rate of Debt		7.19%
Medium-term Notes | Medium Term Notes Payable Due 2028 | Parent Company
Debt Additional Information
Extinguishment of Debt, Amount		$ 30,300,000
Stated Interest Rate of Debt		7.19%
Senior Notes | Notes Issued in 1998 with 2028 Maturity Date
Debt Additional Information
Extinguishment of Debt, Amount	$ 30,000,000
Stated Interest Rate of Debt		7.25%
Senior Notes | Notes Issued in 1998 with 2028 Maturity Date | Parent Company
Debt Additional Information
Extinguishment of Debt, Amount		$ 30,000,000
Stated Interest Rate of Debt		7.25%
Senior Notes | Senior Notes Payable due 2021
Debt Additional Information
Extinguishment of Debt, Amount		$ 350,000,000
Stated Interest Rate of Debt		3.00%
Senior Notes | Senior Notes Payable due 2021 | Parent Company
Debt Additional Information
Extinguishment of Debt, Amount		$ 350,000,000
Stated Interest Rate of Debt		3.00%
Senior Notes | Notes Issued in 2020 due 2025
Debt Additional Information
Stated Interest Rate of Debt	4.50%
Senior Notes | Notes Issued in 2010
Debt Additional Information
Stated Interest Rate of Debt	5.625%
Junior Subordinated Debt | Junior Subordinated Notes Payable Due 2038
Debt Additional Information
Extinguishment of Debt, Amount		$ 22,800,000
Stated Interest Rate of Debt	7.405%
Junior Subordinated Debt | Junior Subordinated Notes Payable Due 2038 | Parent Company
Debt Additional Information
Extinguishment of Debt, Amount	$ 22,800,000
Stated Interest Rate of Debt	7.405%
Receive Fixed/Pay Variable | Interest Rate Swaps
Debt Additional Information
Derivative, Notional Amount	$ 0	250,000,000	250,000,000			$ 250,000,000
Notional Amount Of Derivatives Terminations	250,000,000	0	0
Receive Fixed/Pay Variable | Interest Rate Swaps | Parent Company
Debt Additional Information
Derivative, Notional Amount		250,000,000
Northwind Holdings LLC
Debt Additional Information
Proceeds from Issuance of Senior Long-term Debt				$ 800,000,000
Periodic Principal Payments	$ 45,000,000	$ 60,000,000	$ 60,000,000
Basis Spread on LIBOR				0.78%

Employee Benefit Plans Change i

Employee Benefit Plans Change in Projected Benefit Obligation Amount (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension Plan | UNITED STATES
Defined Benefit Plan, Change in Benefit Obligation
Benefit Obligation at Beginning of Year	$ 2,106.9	$ 1,933.3
Service Cost	11	10.9	$ 9.1
Interest Cost	73	83.3	79.8
Plan Participant Contributions	0	0
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	212.4	225.7
Benefits and Expenses Paid	(126.1)	(146.3)
Curtailment Gain	0	0
Change in Foreign Exchange Rates	0	0
Benefit Obligation at End of Year	2,277.2	2,106.9	1,933.3
Accumulated Benefit Obligation	2,277.2	2,106.9
Defined Benefit Plan, Change in Fair Value of Plan Assets
Fair Value of Plan Assets at Beginning of Year	1,600	1,454.9
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	227.9	282.7
Employer Contributions to Defined Benefit Plan	9.1	8.7
Plan Participant Contributions	0	0
Benefits and Expenses Paid	(126.1)	(146.3)
Effect of Foreign Exchange Rates on Plan Assets	0	0
Fair Value of Plan Assets at End of Year	1,710.9	1,600	1,454.9
Funded Status of Plan	566.3	506.9
Pension Plan | UNITED KINGDOM
Defined Benefit Plan, Change in Benefit Obligation
Benefit Obligation at Beginning of Year	256.9	211
Service Cost	0	0	0
Interest Cost	4.9	6.1	5.9
Plan Participant Contributions	0	0
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	33.8	34.9
Benefits and Expenses Paid	(5.1)	(4.8)
Curtailment Gain	(0.7)	0
Change in Foreign Exchange Rates	10.2	9.7
Benefit Obligation at End of Year	300	256.9	211
Accumulated Benefit Obligation	297.5	253.1
Defined Benefit Plan, Change in Fair Value of Plan Assets
Fair Value of Plan Assets at Beginning of Year	252.8	217
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	36.4	31
Employer Contributions to Defined Benefit Plan	0	0
Plan Participant Contributions	0	0
Benefits and Expenses Paid	(5.1)	(4.8)
Effect of Foreign Exchange Rates on Plan Assets	10	9.6
Fair Value of Plan Assets at End of Year	294.1	252.8	217
Funded Status of Plan	5.9	4.1
Other Postretirement Benefit Plans
Defined Benefit Plan, Change in Benefit Obligation
Benefit Obligation at Beginning of Year	127.2	125.9
Service Cost	0	0	0
Interest Cost	4.1	5.3	4.9
Plan Participant Contributions	0.1	0.2
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	(0.3)	7
Benefits and Expenses Paid	(10.6)	(11.2)
Curtailment Gain	0	0
Change in Foreign Exchange Rates	0	0
Benefit Obligation at End of Year	120.5	127.2	125.9
Defined Benefit Plan, Change in Fair Value of Plan Assets
Fair Value of Plan Assets at Beginning of Year	9.9	10.1
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	0.1	0.2
Employer Contributions to Defined Benefit Plan	9.8	10.6
Plan Participant Contributions	0.1	0.2
Benefits and Expenses Paid	(10.6)	(11.2)
Effect of Foreign Exchange Rates on Plan Assets	0	0
Fair Value of Plan Assets at End of Year	9.3	9.9	$ 10.1
Funded Status of Plan	$ 111.2	$ 117.3

Employee Benefit Plans Amounts

Employee Benefit Plans Amounts Recognized in Balance Sheet (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension Plan | UNITED STATES
Defined Benefit Plans and Other Postretirement Benefit Plans
Current Pension Liability	$ 8	$ 7.7
Noncurrent Pension Liability	558.3	499.2
Noncurrent Pension Asset	0	0
Funded Status of Plan	566.3	506.9
Net Actuarial Gain (Loss) in Balance Sheet	(767.9)	(695.4)
Prior Service Credit in Balance Sheet	(0.6)	(0.7)
Pension Recognized in Balance Sheet, Gross of Deferred Tax	(768.5)	(696.1)
Pension Deferred Tax Asset in Balance Sheet	273.9	240.7
Pension Recognized in Balance Sheet, Net of Deferred Tax	(494.6)	(455.4)	$ (437.3)
Pension Plan | UNITED KINGDOM
Defined Benefit Plans and Other Postretirement Benefit Plans
Current Pension Liability	0	0
Noncurrent Pension Liability	5.9	4.1
Noncurrent Pension Asset	0	0
Funded Status of Plan	5.9	4.1
Net Actuarial Gain (Loss) in Balance Sheet	(70.5)	(63.1)
Prior Service Credit in Balance Sheet	(0.2)	(0.3)
Pension Recognized in Balance Sheet, Gross of Deferred Tax	(70.7)	(63.4)
Pension Deferred Tax Asset in Balance Sheet	16	14.5
Pension Recognized in Balance Sheet, Net of Deferred Tax	(54.7)	(48.9)	(37.3)
Other Postretirement Benefit Plans
Defined Benefit Plans and Other Postretirement Benefit Plans
Current Pension Liability	1.5	1.5
Noncurrent Pension Liability	109.7	115.8
Noncurrent Pension Asset	0	0
Funded Status of Plan	111.2	117.3
Net Actuarial Gain (Loss) in Balance Sheet	11	11.1
Prior Service Credit in Balance Sheet	2.9	3.1
Pension Recognized in Balance Sheet, Gross of Deferred Tax	13.9	14.2
Pension Deferred Tax Asset in Balance Sheet	5.4	5.3
Pension Recognized in Balance Sheet, Net of Deferred Tax	$ 19.3	$ 19.5	$ 27.4

Employee Benefit Plans Amount_2

Employee Benefit Plans Amounts Recognized in Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension Plan | UNITED STATES
Defined Benefit Plans and Other Postretirement Benefit Plans
Pension Recognized in Balance Sheet, Net of Deferred Tax, Beginning of Year	$ (455.4)	$ (437.3)
Amortization of Net Actuarial Loss (Gain)	18.7	20.2	$ 21.7
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, before Tax	(91.2)	(43)
Amortization of Prior Service Cost (Credit)	0.1	0	0
Change in Other Comprehensive Income, Curtailment Gain (Loss)	0	0
Change in Unrecognized Pension and Postretirement Benefit Costs, Tax Expense	33.2	4.7
Pension Recognized in Balance Sheet, Net of Deferred Tax, End of Year	(494.6)	(455.4)	(437.3)
Pension Plan | UNITED KINGDOM
Defined Benefit Plans and Other Postretirement Benefit Plans
Pension Recognized in Balance Sheet, Net of Deferred Tax, Beginning of Year	(48.9)	(37.3)
Amortization of Net Actuarial Loss (Gain)	1.1	0.9	0.6
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, before Tax	(8.5)	(15.1)
Amortization of Prior Service Cost (Credit)	0	0	0
Change in Other Comprehensive Income, Curtailment Gain (Loss)	0.1	0
Change in Unrecognized Pension and Postretirement Benefit Costs, Tax Expense	1.5	2.6
Pension Recognized in Balance Sheet, Net of Deferred Tax, End of Year	(54.7)	(48.9)	(37.3)
Other Postretirement Benefit Plans
Defined Benefit Plans and Other Postretirement Benefit Plans
Pension Recognized in Balance Sheet, Net of Deferred Tax, Beginning of Year	19.5	27.4
Amortization of Net Actuarial Loss (Gain)	0	(2.5)	0
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, before Tax	(0.1)	(7.3)
Amortization of Prior Service Cost (Credit)	(0.2)	(0.2)	(0.2)
Change in Other Comprehensive Income, Curtailment Gain (Loss)	0	0
Change in Unrecognized Pension and Postretirement Benefit Costs, Tax Expense	0.1	2.1
Pension Recognized in Balance Sheet, Net of Deferred Tax, End of Year	$ 19.3	$ 19.5	$ 27.4

Employee Benefit Plans US Pensi

Employee Benefit Plans US Pension Assets, Fair Value Measurement by Input Level (Details) - UNITED STATES - Pension Plan - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	$ 1,710.9	$ 1,600	$ 1,454.9
U.S. Large Cap
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	112.6	95.2
U.S. Large Cap | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
U.S. Large Cap | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
U.S. Large Cap | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
U.S. Large Cap | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	112.6	95.2
U.S. Small Cap
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	59	47.8
U.S. Small Cap | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	25.8	23
U.S. Small Cap | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
U.S. Small Cap | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
U.S. Small Cap | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	33.2	24.8
Global
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	307.9	299.1
Global | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Global | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Global | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Global | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	307.9	299.1
International
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	31.6	28.3
International | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
International | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
International | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
International | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	31.6	28.3
Emerging Markets
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	62.3	50.4
Emerging Markets | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Emerging Markets | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Emerging Markets | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Emerging Markets | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	62.3	50.4
U.S. Government and Agencies
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	227.8	199
U.S. Government and Agencies | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	227.8	199
U.S. Government and Agencies | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
U.S. Government and Agencies | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
U.S. Government and Agencies | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Corporate
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	445.6	391.1
Corporate | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Corporate | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	445.6	391.1
Corporate | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Corporate | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
State and Municipal Securities
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	3.7	2.5
State and Municipal Securities | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
State and Municipal Securities | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	3.7	2.5
State and Municipal Securities | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
State and Municipal Securities | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Opportunistic Credits
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	200.4	196.5
Opportunistic Credits | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Opportunistic Credits | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Opportunistic Credits | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Opportunistic Credits | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	200.4	196.5
Real Estate
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	108.9	108.4
Real Estate | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Real Estate | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Real Estate | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Real Estate | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	108.9	108.4
Private Equity Direct Investments
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	62.1	57.7
Private Equity Direct Investments | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Private Equity Direct Investments | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Private Equity Direct Investments | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Private Equity Direct Investments | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	62.1	57.7
Private Equity Funds of Funds
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	39.2	38.4
Private Equity Funds of Funds | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Private Equity Funds of Funds | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Private Equity Funds of Funds | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Private Equity Funds of Funds | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	39.2	38.4
Cash Equivalents
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	46.3	82.4
Cash Equivalents | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	46.3	82.4
Cash Equivalents | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Cash Equivalents | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Cash Equivalents | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Total Invested Assets
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	1,707.4	1,596.8
Total Invested Assets | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	299.9	304.4
Total Invested Assets | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	449.3	393.6
Total Invested Assets | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Total Invested Assets | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	$ 958.2	$ 898.8

Employee Benefit Plans UK Pensi

Employee Benefit Plans UK Pension Assets, Fair Value Measurement by Input Level (Details) - Pension Plan - UNITED KINGDOM - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	$ 294.1	$ 252.8	$ 217
Fair Value, Inputs, Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	118.1	89.8
Fair Value, Inputs, Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	0	0
Fair Value, Inputs, Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	0	0
Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	176	163
Diversified Growth Assets
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	176	163
Diversified Growth Assets | Fair Value, Inputs, Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	0	0
Diversified Growth Assets | Fair Value, Inputs, Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	0	0
Diversified Growth Assets | Fair Value, Inputs, Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	0	0
Diversified Growth Assets | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	176	163
Fixed Interest and Index-linked Securities
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	116.8	89.6
Fixed Interest and Index-linked Securities | Fair Value, Inputs, Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	116.8	89.6
Fixed Interest and Index-linked Securities | Fair Value, Inputs, Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	0	0
Fixed Interest and Index-linked Securities | Fair Value, Inputs, Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	0	0
Fixed Interest and Index-linked Securities | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	0	0
Cash Equivalents
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	1.3	0.2
Cash Equivalents | Fair Value, Inputs, Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	1.3	0.2
Cash Equivalents | Fair Value, Inputs, Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	0	0
Cash Equivalents | Fair Value, Inputs, Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	0	0
Cash Equivalents | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	$ 0	$ 0

Employee Benefit Plans OPEB Pla

Employee Benefit Plans OPEB Plan Assets, Fair Value Measurements by Input Level (Details) - Other Postretirement Benefit Plans - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plans and Other Postretirement Benefit Plans
Life Settlement Contracts, Fair Value Method, Face Value	$ 9.3	$ 9.9
Fair Value, Inputs, Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans
Life Settlement Contracts, Fair Value Method, Face Value	0	0
Fair Value, Inputs, Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans
Life Settlement Contracts, Fair Value Method, Face Value	0	0
Fair Value, Inputs, Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans
Life Settlement Contracts, Fair Value Method, Face Value	$ 9.3	$ 9.9

Employee Benefit Plans OPEB Cha

Employee Benefit Plans OPEB Changes in Assets Measured at Fair Value Using Signficant Unobservable Inputs (Details) - Other Postretirement Benefit Plans - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Fair Value of Plan Assets at Beginning of Year	$ 9.9	$ 10.1
Fair Value of Plan Assets at End of Year	9.3	9.9
Fair Value, Inputs, Level 3 | Life Insurance Contracts
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Fair Value of Plan Assets at Beginning of Year	9.9	10.1
Actual Return on Plan Assets Still Held	0.1	0.2
Plan Participant Contributions	9.9	10.8
Defined Benefit Plan, Plan Assets, Benefits Paid	10.6	11.2
Fair Value of Plan Assets at End of Year	$ 9.3	$ 9.9

Employee Benefit Plans Measurem

Employee Benefit Plans Measurement Assumptions (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Pension Plan | UNITED STATES
Defined Benefit Plans and Other Postretirement Benefit Plans
Discount Rate Assumptions Used Calculating Benefit Obligation	2.90%	3.60%
Discount Rate Assumptions Used Calculating Net Periodic Benefit Cost	3.60%	4.40%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets	7.00%	7.00%
Pension Plan | UNITED KINGDOM
Defined Benefit Plans and Other Postretirement Benefit Plans
Discount Rate Assumptions Used Calculating Benefit Obligation	1.40%	2.00%
Rate of Compensation Increase Assumptions Used Calculating Benefit Obligation	2.80%	2.90%
Discount Rate Assumptions Used Calculating Net Periodic Benefit Cost	2.00%	2.90%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets	4.10%	4.30%
Rate of Compensation Increase Assumptions Used Calculating Net Periodic Benefit Cost	2.90%	3.70%
Other Postretirement Benefit Plans
Defined Benefit Plans and Other Postretirement Benefit Plans
Discount Rate Assumptions Used Calculating Benefit Obligation	2.60%	3.40%
Discount Rate Assumptions Used Calculating Net Periodic Benefit Cost	3.40%	4.40%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets	5.75%	5.75%

Employee Benefit Plans Net Peri

Employee Benefit Plans Net Periodic Benefit Cost (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension Plan | UNITED STATES
Defined Benefit Plans and Other Postretirement Benefit Plans
Service Cost	$ 11	$ 10.9	$ 9.1
Interest Cost	73	83.3	79.8
Expected Return on Plan Assets	(106.7)	(99.4)	(104.5)
Amortization of Net Actuarial Loss (Gain)	18.7	20.2	21.7
Amortization of Prior Service Cost (Credit)	0.1	0	0
Curtailment Gain	0	0	0
Net Periodic Benefit Cost	(3.9)	15	6.1
Pension Plan | UNITED KINGDOM
Defined Benefit Plans and Other Postretirement Benefit Plans
Service Cost	0	0	0
Interest Cost	4.9	6.1	5.9
Expected Return on Plan Assets	(9.5)	(8.9)	(8.9)
Amortization of Net Actuarial Loss (Gain)	1.1	0.9	0.6
Amortization of Prior Service Cost (Credit)	0	0	0
Curtailment Gain	0.1	0	0
Net Periodic Benefit Cost	(3.4)	(1.9)	(2.4)
Other Postretirement Benefit Plans
Defined Benefit Plans and Other Postretirement Benefit Plans
Service Cost	0	0	0
Interest Cost	4.1	5.3	4.9
Expected Return on Plan Assets	(0.5)	(0.6)	(0.6)
Amortization of Net Actuarial Loss (Gain)	0	(2.5)	0
Amortization of Prior Service Cost (Credit)	(0.2)	(0.2)	(0.2)
Curtailment Gain	0	0	0
Net Periodic Benefit Cost	$ 3.4	$ 2	$ 4.1

Employee Benefit Plans Expected

Employee Benefit Plans Expected Benefit Payments (Details) $ in Millions	Dec. 31, 2020USD ($)
Pension Plan | UNITED STATES
Defined Benefit Plans and Other Postretirement Benefit Plans
Benefit Payments in Year One	$ 75
Benefit Payments in Year Two	78.4
Benefit Payments in Year Three	82.2
Benefit Payments in Year Four	86.1
Benefit Payments in Year Five	90.1
Benefit Payments in Five Fiscal Years Thereafter	514.9
Pension Plan | UNITED KINGDOM
Defined Benefit Plans and Other Postretirement Benefit Plans
Benefit Payments in Year One	6.1
Benefit Payments in Year Two	6.1
Benefit Payments in Year Three	6.5
Benefit Payments in Year Four	7
Benefit Payments in Year Five	7.2
Benefit Payments in Five Fiscal Years Thereafter	42.3
Other Postretirement Benefit Plans
Defined Benefit Plans and Other Postretirement Benefit Plans
Benefit Payments in Year One	11.1
Prescription Drug Subsidy Receipts in Year One	0.1
Net OPEB Payments in Year One	11
Benefit Payments in Year Two	10.5
Prescription Drug Subsidy Receipts in Year Two	0.1
Net OPEB Payments in Year Two	10.4
Benefit Payments in Year Three	10
Prescription Drug Subsidy Receipts in Year Three	0.1
Net OPEB Payments in Year Three	9.9
Benefit Payments in Year Four	9.5
Prescription Drug Subsidy Receipts in Year Four	0.1
Net OPEB Payments in Year Four	9.4
Benefit Payments in Year Five	9
Prescription Drug Subsidy Receipts in Year Five	0.1
Net OPEB Payments in Year Five	8.9
Benefit Payments in Five Fiscal Years Thereafter	38.3
Prescription Drug Subsidy Receipts in Five Fiscal Years Thereafter	0.2
Net OPEB Payments in Five Fiscal Years Thereafter	$ 38.1

Employee Benefit Plans - Additi

Employee Benefit Plans - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)	Dec. 31, 2020GBP (£)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Pension and Other Postretirement Benefits Disclosure
Health Care Cost Trend Rate Assumed for Next Fiscal Year	6.50%	6.50%	6.50%
Ultimate Health Care Cost Trend Rate	5.00%	5.00%
Defined Benefit Plan, Year Health Care Cost Trend Rate Reaches Ultimate Trend Rate	2027	2027
Pension Plan | UNITED STATES
Pension and Other Postretirement Benefits Disclosure
Defined Benefit Plan, Benefit Obligation, Benefits Paid	$ 126.1		$ 146.3
Average Remaining Life Expectancy of Plan Participants	25 years	25 years
Retirement Benefits, Description	We had no regulatory contribution requirements for our U.S. qualified defined benefit plan in 2020	We had no regulatory contribution requirements for our U.S. qualified defined benefit plan in 2020
Pension Plan | UNITED STATES | Group Annuity Contact
Pension and Other Postretirement Benefits Disclosure
Defined Benefit Plan, Benefit Obligation, Benefits Paid	$ 44		59.5
Pension Plan | UNITED KINGDOM
Pension and Other Postretirement Benefits Disclosure
Defined Benefit Plan, Benefit Obligation, Benefits Paid	$ 5.1		4.8
Average Remaining Life Expectancy of Plan Participants	31 years	31 years
Payment for Pension Benefits	$ 0
Other Postretirement Benefit Plans
Pension and Other Postretirement Benefits Disclosure
Defined Benefit Plan, Benefit Obligation, Benefits Paid	10.6		11.2
Investment Level 3 Transfers Into	0		0
Investment Level 3 Transfers Out of	$ 0		$ 0
Interest Rate During Period	4.87%	4.87%	4.74%
Other Postretirement Benefit Plans | UNITED STATES
Pension and Other Postretirement Benefits Disclosure
Matching Contribution Percent of Employees' Gross Pay	5.00%	5.00%
Employer Discretionary Contribution Percentage of earnings	4.50%	4.50%
Cost Recognized	$ 83.4		$ 77.3	$ 72.7
Other Postretirement Benefit Plans | UNITED KINGDOM
Pension and Other Postretirement Benefits Disclosure
Matching Contribution Percent of Employees' Gross Pay	5.00%	5.00%
Employer Discretionary Contribution Percentage of earnings	6.00%	6.00%
Employer Matching Contribution for Every Pound on the First One Percent of Employee Contributions | £		£ 2
Employee Contribution Percentage Received 2-for-1 Employer Match	1.00%	1.00%
Cost Recognized	$ 5		$ 4.4	$ 4.2
Equity Securities | Pension Plan | UNITED STATES
Pension and Other Postretirement Benefits Disclosure
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	36.00%	36.00%
Fixed Maturity Securities | Pension Plan | UNITED STATES
Pension and Other Postretirement Benefits Disclosure
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	40.00%	40.00%
Alternative Investments | Pension Plan | UNITED STATES
Pension and Other Postretirement Benefits Disclosure
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	24.00%	24.00%
Diversified Growth Assets | Pension Plan | UNITED KINGDOM
Pension and Other Postretirement Benefits Disclosure
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	65.00%	65.00%
Interest Rate Contract | Pension Plan | UNITED KINGDOM
Pension and Other Postretirement Benefits Disclosure
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	35.00%	35.00%
Minimum | Private Equity Funds of Funds | Pension Plan | UNITED STATES
Pension and Other Postretirement Benefits Disclosure
Private Equity Partnership Future Liquidation Term	5 years	5 years
Maximum | Private Equity Funds of Funds | Pension Plan | UNITED STATES
Pension and Other Postretirement Benefits Disclosure
Private Equity Partnership Future Liquidation Term	8 years	8 years

Basic and Diluted Earnings Per

Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended													12 Months Ended
	Dec. 31, 2020	[1],[2],[3],[4],[5]	Sep. 30, 2020	[6]	Jun. 30, 2020	[7]	Mar. 31, 2020	Dec. 31, 2019	[8]	Sep. 30, 2019	[9]	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Numerator
Net Income	$ 135.4		$ 231.1		$ 265.5		$ 161	$ 296.2		$ 242		$ 281.2	$ 280.9	$ 793	$ 1,100.3	$ 523.4
Denominator
Weighted Average Common Shares - Basic														203,642,000	209,728,900	219,635,600
Dilution for Assumed Exercises of Stock Options and Nonvested Stock Awards														113,300	125,500	423,000
Weighted Average Common Shares - Assuming Dilution														203,755,300	209,854,400	220,058,600
Net Income Per Common Share
Basic	$ 0.66		$ 1.13		$ 1.30		$ 0.79	$ 1.44		$ 1.16		$ 1.33	$ 1.31	$ 3.89	$ 5.25	$ 2.38
Assuming Dilution	$ 0.66		$ 1.13		$ 1.30		$ 0.79	$ 1.44		$ 1.16		$ 1.33	$ 1.31	$ 3.89	$ 5.24	$ 2.38
[1]	Fourth quarter of 2020 amortization of the cost of reinsurance related to the Closed Block individual disability reinsurance transaction of $2.6 million before tax and $2.0 million after tax.
[2]	Fourth quarter of 2020 impacts from the Closed Block individual disability reinsurance transaction of $1,305.5 million before tax and $1,031.3 million after tax.
[3]	Fourth quarter of 2020 net realized investment gain of $1,302.3 million before tax and $1,028.8 million after tax, related to the transfer of investments for the Closed Block individual disability reinsurance transaction.
[4]	Fourth quarter of 2020 net tax benefit from the Closed Block individual disability reinsurance transaction of $36.5 million.
[5]	Fourth quarter of 2020 reserve increases of $151.5 million and $17.5 million before tax and $119.7 million and $13.8 million after tax related to long-term care and group pension, respectively.
[6]	Third quarter of 2020 costs related to organizational design update of $23.3 million before tax and $18.6 million after tax.
[7]	Second quarter of 2020 impairment on ROU asset related to an operating lease for office space that we do not plan to continue using to support our general operations of $12.7 million before tax and $10.0 million after tax.
[8]	Fourth quarter of 2019 cost related to the early retirement of debt of $2.1 million before tax and $1.7 million after tax.
[9]	Third quarter of 2019 cost related to the early retirement of debt of $25.2 million before tax and $19.9 million after tax.

Treasury Stock Transactions (De

Treasury Stock Transactions (Details) - USD ($) shares in Millions, $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Equity, Class of Treasury Stock
Expiration Date of Share Repurchase Program Authorized in May 2019		Nov. 23, 2020
Number of Treasury Shares Repurchased		0	12.3	8.7
Commission Paid on Stock Repurchases			$ 0.4	$ 0.7
Repurchase Program Authorized in May 2018
Equity, Class of Treasury Stock
Authorized Amount of Treasury Share Repurchases Under Stock Repurchase Program		$ 750
Remaining Amount of Treasury Share Repurchases Authorized Under Stock Repurchase Program		0
Repurchase Program Authorized in May 2019
Equity, Class of Treasury Stock
Authorized Amount of Treasury Share Repurchases Under Stock Repurchase Program		750
Open Market Repurchase
Equity, Class of Treasury Stock
Cost of Shares Repurchased	[1]	$ 0	$ 400.4	$ 350.7
[1]	Includes commissions of $0.4 million and $0.7 million for the years ended December 31, 2019 and 2018, respectively.

Stockholders' Equity and Earn_3

Stockholders' Equity and Earnings Per Common Share - Additional Information (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Stockholders Equity and Earnings Per Common Share Additional Information [Abstract]
Antidilutive Securities Excluded from Computation of Earnings Per Share	1,600,000	1,100,000	600,000
Authorized Shares of Preferred Stock	25,000,000
Par Value Per Share of Preferred Stock	$ 0.10
Issued Shares of Preferred Stock	0

Stock-Based Compensation - Acti

Stock-Based Compensation - Activity for SSUs (Details) - Stock Success Units (SSUs) shares in Thousands	12 Months Ended
	Dec. 31, 2020$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares
Shares Outstanding Beginning Balance | shares	0
Shares Granted | shares	321
Shares Outstanding Ending Balance | shares	321
Weighted Average Grant Date Fair Value at Beginning of Period | $ / shares	$ 0
Weighted Average Grant Date Fair Value of Shares Granted | $ / shares	18.78
Weighted Average Grant Date Fair Value at End of Period | $ / shares	$ 18.78

Stock-Based Compensation - Ac_2

Stock-Based Compensation - Activity for Cash-Settled RSUs (Details) - Cash Settled RSUs shares in Thousands	12 Months Ended
	Dec. 31, 2020$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares
Shares Outstanding Beginning Balance | shares	0
Shares Granted | shares	68
Shares Outstanding Ending Balance | shares	68
Weighted Average Grant Date Fair Value at Beginning of Period | $ / shares	$ 0
Weighted Average Grant Date Fair Value of Shares Granted | $ / shares	22.94
Weighted Average Grant Date Fair Value at End of Period | $ / shares	$ 22.94

Stock-Based Compensation - Ac_3

Stock-Based Compensation - Activity for PSUs Classified as Equity (Details) - Performance Share Units - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares
Shares Outstanding Beginning Balance	337
Shares Granted	323
Shares Vested	(135)
Shares Forfeited	(8)
Shares Outstanding Ending Balance	517	337
Weighted Average Grant Date Fair Value at Beginning of Period	$ 44.11
Weighted Average Grant Date Fair Value of Shares Granted	23.49	$ 41.57	$ 44.19
Weighted Average Grant Date Fair Value of Shares Vested	48.20
Weighted Average Grant Date Fair Value of Shares Forfeited	35.81
Weighted Average Grant Date Fair Value at End of Period	$ 30.31	$ 44.11

Stock-Based Compensation - Valu

Stock-Based Compensation - Valuation Assumptions on PSU Grants (Details) - Performance Share Units	12 Months Ended
	Dec. 31, 2020Rate	Dec. 31, 2019Rate	Dec. 31, 2018Rate
Share-based Compensation Arrangement by Share-based Payment Award
Expected Volatility Rate	23.00%	23.00%	24.00%
Expected Life	3 years	3 years	3 years
Risk Free Interest Rate	0.85%	2.53%	2.32%

Stock-Based Compensation - Nonv

Stock-Based Compensation - Nonvested Stock Awards Classified in Equity (Details) - Restricted Stock Units (RSUs) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares
Shares Outstanding Beginning Balance	1,044
Shares Granted	1,262
Shares Vested	(626)
Shares Forfeited	(87)
Shares Outstanding Ending Balance	1,593	1,044
Weighted Average Grant Date Fair Value at Beginning of Period	$ 41.06
Weighted Average Grant Date Fair Value of Shares Granted	22.71	$ 37.07	$ 47.76
Weighted Average Grant Date Fair Value of Shares Vested	40.11
Weighted Average Grant Date Fair Value of Shares Forfeited	28.75
Weighted Average Grant Date Fair Value at End of Period	$ 27.57	$ 41.06

Stock option activity (Details)

Stock option activity (Details) - Stock Options $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding
Shares Outstanding at Beginning of Period | shares	74
Shares Exercised | shares	(13)
Shares Forfeited | shares	21
Shares Outstanding at End of Period | shares	40
Shares Exercisable | shares	40
Weighted Average Exercise Price of Shares Outstanding at Beginning of Period | $ / shares	$ 24.09
Weighted Average Exercise Price of Shares Exercised | $ / shares	23.35
Weighted Average Exercise Price of Shares Forfeited | $ / shares	24.25
Weighted Average Exercise Price of Shares Outstanding at End of Period | $ / shares	24.25
Weighted Average Exercise Price of Exercisable Shares | $ / shares	$ 24.25
Weighted Average Remaining Contractual Term of Outstanding Options	1 month 6 days
Weighted Average Remaining Contractual Term of Exercisable Options	1 month 6 days
Options Outstanding, Intrinsic Value | $	$ 0
Options, Exercisable, Intrinsic Value | $	$ 0

Intrinsic Value of Options Exer

Intrinsic Value of Options Exercised and Fair Value of Options Vested (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award
Intrinsic Value of Options Exercised	$ 0.1	$ 0.3	$ 0.7
Fair Value of Options Vested	$ 0	$ 0	$ 0

Stock-Based Compensation Expens

Stock-Based Compensation Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award
Allocated Share-based Compensation Expense, Before Tax	$ 30.4	$ 26.6	$ 26.3
Allocated Share-based Compensation Expense, Net of Tax	26.1	22.7	20.9
Performance Share Units
Share-based Compensation Arrangement by Share-based Payment Award
Allocated Share-based Compensation Expense, Before Tax	5.6	5	6.8
Restricted Stock Units and Cash-Settled Awards
Share-based Compensation Arrangement by Share-based Payment Award
Allocated Share-based Compensation Expense, Before Tax	23.9	21	19
Other Awards
Share-based Compensation Arrangement by Share-based Payment Award
Allocated Share-based Compensation Expense, Before Tax	0.5	0.6	0.5
Stock Success Units (SSUs)
Share-based Compensation Arrangement by Share-based Payment Award
Allocated Share-based Compensation Expense, Before Tax	$ 0.4	$ 0	$ 0

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award
Cash Received Under Share-based Payment Arrangements	$ 4.4	$ 6.1	$ 4.6
Fair Value of Options Vested	$ 0	$ 0	$ 0
Stock Incentive Plan 2017
Share-based Compensation Arrangement by Share-based Payment Award
Number of Shares Authorized	17,000,000
Number of Shares for Each Full Value Award	1.76
Total Duration of the Stock Incentive Plan	8 years
Award Vesting Period	3 years
Number of Shares Available for Grant	10,100,000
Stock Incentive Plan 2012
Share-based Compensation Arrangement by Share-based Payment Award
Number of Shares Authorized	20,000,000
Number of Shares for Each Full Value Award	1.76
Total Duration of the Stock Incentive Plan	8 years
Award Vesting Period	3 years
Performance Share Units
Share-based Compensation Arrangement by Share-based Payment Award
Award Vesting Period	3 years
Weighted Average Grant Date Fair Value of Shares Granted	$ 23.49	$ 41.57	$ 44.19
Compensation Cost Not yet Recognized	$ 6.5
Period for Recognition of Compensation Cost Not Yet Recognized	1 year 7 months 6 days
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award
Weighted Average Grant Date Fair Value of Shares Granted	$ 22.71	$ 37.07	$ 47.76
Compensation Cost Not yet Recognized	$ 21.2
Period for Recognition of Compensation Cost Not Yet Recognized	10 months 24 days
Fair Value of Awards Vested During the Period	$ 25.1	$ 19.5	$ 18.1
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award
Stock Option Compensation Not yet Recognized	$ 0
Options Granted	0	0	0
Stock Success Units (SSUs)
Share-based Compensation Arrangement by Share-based Payment Award
Award Vesting Period	6 years
Weighted Average Grant Date Fair Value of Shares Granted	$ 18.78
Compensation Cost Not yet Recognized	$ 5.7
Period for Recognition of Compensation Cost Not Yet Recognized	2 years 10 months 24 days
Fair Value of Awards Vested During the Period	$ 0
Cash Settled RSUs
Share-based Compensation Arrangement by Share-based Payment Award
Weighted Average Grant Date Fair Value of Shares Granted	$ 22.94
Compensation Cost Not yet Recognized	$ 1.1
Period for Recognition of Compensation Cost Not Yet Recognized	1 year 1 month 6 days
Fair Value of Awards Vested During the Period	$ 0
Minimum | Performance Share Units
Share-based Compensation Arrangement by Share-based Payment Award
Percentage of Stock-based Awards Possible to be Earned	40.00%
Minimum | Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award
Award Vesting Period	1 year
Minimum | Stock Options
Share-based Compensation Arrangement by Share-based Payment Award
Award Vesting Period	1 year
Minimum | Cash Settled RSUs
Share-based Compensation Arrangement by Share-based Payment Award
Award Vesting Period	1 year
Maximum | Performance Share Units
Share-based Compensation Arrangement by Share-based Payment Award
Percentage of Stock-based Awards Possible to be Earned	180.00%
Maximum | Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award
Award Vesting Period	3 years
Maximum | Stock Options
Share-based Compensation Arrangement by Share-based Payment Award
Award Vesting Period	3 years
Maximum | Cash Settled RSUs
Share-based Compensation Arrangement by Share-based Payment Award
Award Vesting Period	3 years

Reinsurance - Premium Income Da

Reinsurance - Premium Income Data (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Effects of Reinsurance
Direct Premium Income									$ 9,621.9	$ 9,576.3	$ 9,171.1
Reinsurance Assumed									94.1	116.5	142.6
Reinsurance Ceded									(337.9)	(327.2)	(327.6)
Premium Income	$ 2,319.9	$ 2,318.1	$ 2,368.7	$ 2,371.4	$ 2,352.6	$ 2,331.2	$ 2,343.1	$ 2,338.7	9,378.1	9,365.6	8,986.1
Ceded Benefits and Change in Reserves for Future Benefits									$ 628.8	$ 650.1	$ 667.2

Reinsurance - Additional Inform

Reinsurance - Additional Information (Detail) $ in Millions	3 Months Ended									12 Months Ended
	Dec. 31, 2020USD ($)		Sep. 30, 2020USD ($)	Jun. 30, 2020USD ($)	Mar. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Sep. 30, 2019USD ($)	Jun. 30, 2019USD ($)	Mar. 31, 2019USD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 16, 2020USD ($)	Dec. 31, 2017USD ($)
Negative Ceding Commission										$ 438
Net Realized Gain Related to the Transfer of Investments	$ 1,304.9	[1]	$ 4.4	$ 33.8	$ (144)	$ 9.2	$ (26.2)	$ (7.3)	$ 1.1	1,199.1	$ (23.2)	$ (39.5)
Transaction Costs Related to Reinsurance Transaction										996.6	943.6	891.2
Income Taxes Receivable, Net Operating Loss, CARES Act										36.5
Reinsurance Recoverables, Incurred but Not Reported Claims	8,378.9					$ 2,246.8				8,378.9	$ 2,246.8	$ 2,227.3		$ 2,182
Prepaid Reinsurance Premiums	$ 813									$ 813
Number of companies that make up majority of reinsurance recoverable	9									9
Closed Block Individual Disability Reinsurance Transaction
Net Realized Gain Related to the Transfer of Investments										$ 1,302.3
Increase in Benefits and Change in Reserves for Future Benefits										1,284.5
Transaction Costs Related to Reinsurance Transaction										21
Reinsurance Recoverables, Incurred but Not Reported Claims	$ 6,141.5									6,141.5			$ 6,141.5
Prepaid Reinsurance Premiums													815.7
Deposit Contracts, Assets													$ 88.2
Amortization of Prepaid Reinsurance Premium										$ 2.6
AM Best A Rating or Better | Reinsurer Concentration Risk | Reinsurance Recoverable | Commonwealth Annuity and Life Insurance Company
Percentage of Concentration Risk										59.00%
AM Best A Rating or Better | Reinsurer Concentration Risk | Reinsurance Recoverable | Top 9 Reinsurers
Percentage of Concentration Risk										35.00%
AM Best, A- Rating | Reinsurer Concentration Risk | Reinsurance Recoverable | Other Reinsurers
Percentage of Concentration Risk										5.00%
AM Best, Below A- or Not Rated | Reinsurer Concentration Risk | Reinsurance Recoverable | Other Reinsurers
Percentage of Concentration Risk										1.00%
[1]	Fourth quarter of 2020 net realized investment gain of $1,302.3 million before tax and $1,028.8 million after tax, related to the transfer of investments for the Closed Block individual disability reinsurance transaction.

Premium Income by Major Line of

Premium Income by Major Line of Business within Each Segment (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information
Premium Income	$ 2,319.9	$ 2,318.1	$ 2,368.7	$ 2,371.4	$ 2,352.6	$ 2,331.2	$ 2,343.1	$ 2,338.7	$ 9,378.1	$ 9,365.6	$ 8,986.1
Accident, Sickness, and Disability
Segment Reporting Information
Premium Income									6,975.2	6,944.9	6,673.5
Life
Segment Reporting Information
Premium Income									2,402.9	2,420.7	2,312.6
Operating Segments
Segment Reporting Information
Premium Income									9,378.1	9,365.6	8,986.1
Operating Segments | Unum US
Segment Reporting Information
Premium Income									6,018.9	6,016.6	5,736.4
Operating Segments | Unum US | Group Long-term Disability
Segment Reporting Information
Premium Income									1,828.5	1,823.1	1,766.2
Operating Segments | Unum US | Group Short-term Disability
Segment Reporting Information
Premium Income									799.2	768.8	706.3
Operating Segments | Unum US | Group Life
Segment Reporting Information
Premium Income									1,640.5	1,662	1,583.7
Operating Segments | Unum US | Accidental Death & Dismemberment
Segment Reporting Information
Premium Income									163.9	165.7	156.3
Operating Segments | Unum US | Individual Disability
Segment Reporting Information
Premium Income									456	440.7	425.4
Operating Segments | Unum US | Voluntary Benefits
Segment Reporting Information
Premium Income									875.2	910.2	895.7
Operating Segments | Unum US | Dental and Vision
Segment Reporting Information
Premium Income									255.6	246.1	202.8
Operating Segments | Unum International
Segment Reporting Information
Premium Income									652.8	630.5	568.8
Operating Segments | Unum International | Group Long-term Disability
Segment Reporting Information
Premium Income									364.9	353.4	358.9
Operating Segments | Unum International | Group Life
Segment Reporting Information
Premium Income									108.5	115.7	110.8
Operating Segments | Unum International | Supplemental
Segment Reporting Information
Premium Income									99.8	89.5	81.7
Operating Segments | Unum International | Unum Poland
Segment Reporting Information
Premium Income									79.6	71.9	17.4
Operating Segments | Colonial Life
Segment Reporting Information
Premium Income									1,712	1,685	1,603.8
Operating Segments | Colonial Life | Accident, Sickness, and Disability
Segment Reporting Information
Premium Income									975.1	973.4	929.3
Operating Segments | Colonial Life | Life
Segment Reporting Information
Premium Income									376.4	351.6	328.4
Operating Segments | Colonial Life | Cancer and Critical Illness Colonial
Segment Reporting Information
Premium Income									360.5	360	346.1
Operating Segments | Closed Block
Segment Reporting Information
Premium Income									994.4	1,033.5	1,077.1
Operating Segments | Closed Block | Individual Disability
Segment Reporting Information
Premium Income									319.6	374.3	420.8
Operating Segments | Closed Block | Long-term Care
Segment Reporting Information
Premium Income									666.9	651.6	648.3
Operating Segments | Closed Block | Other Insurance Product Line
Segment Reporting Information
Premium Income									$ 7.9	$ 7.6	$ 8

Selected Operating Statement Da

Selected Operating Statement Data by Segment (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information
Premium Income	$ 2,319.9	$ 2,318.1	$ 2,368.7	$ 2,371.4	$ 2,352.6	$ 2,331.2	$ 2,343.1	$ 2,338.7	$ 9,378.1	$ 9,365.6	$ 8,986.1
Net Investment Income	$ 593.5	$ 613.2	$ 569	$ 585	$ 616.3	$ 599.4	$ 624.9	$ 594.7	2,360.7	2,435.3	2,453.7
Other Income									224.2	221.2	198.2
Interest and Debt Expense									188.2	177.4	167.3
Operating Segments
Segment Reporting Information
Premium Income									9,378.1	9,365.6	8,986.1
Net Investment Income									2,360.7	2,435.3	2,453.7
Other Income									224.2	221.2	198.2
Adjusted Operating Revenue									11,963	12,022.1	11,638
Adjusted Operating Income (Loss)									1,278	1,432.6	1,418.1
Interest and Debt Expense									188.2	177.4	167.3
Depreciation and Amortization									722.3	727.5	673.8
Operating Segments | Unum US
Segment Reporting Information
Premium Income									6,018.9	6,016.6	5,736.4
Net Investment Income									720.3	739.4	778.7
Other Income									154.9	142.8	118.5
Adjusted Operating Revenue									6,894.1	6,898.8	6,633.6
Adjusted Operating Income (Loss)									825.4	1,031.1	1,014.6
Interest and Debt Expense									0	0	0
Depreciation and Amortization									421.7	422.8	389.6
Operating Segments | Unum International
Segment Reporting Information
Premium Income									652.8	630.5	568.8
Net Investment Income									104.6	122.5	117.2
Other Income									0.5	0.6	0.4
Adjusted Operating Revenue									757.9	753.6	686.4
Adjusted Operating Income (Loss)									76.6	107.9	113.9
Interest and Debt Expense									0	0	0
Depreciation and Amortization									20.1	18.7	17.6
Operating Segments | Colonial Life
Segment Reporting Information
Premium Income									1,712	1,685	1,603.8
Net Investment Income									155.7	148	151.2
Other Income									1.1	3.4	1.2
Adjusted Operating Revenue									1,868.8	1,836.4	1,756.2
Adjusted Operating Income (Loss)									335.4	344.5	335.2
Interest and Debt Expense									0	0	0
Depreciation and Amortization									273.9	276.6	257.3
Operating Segments | Closed Block
Segment Reporting Information
Premium Income									994.4	1,033.5	1,077.1
Net Investment Income									1,370.3	1,404.9	1,377.1
Other Income									66.6	71.3	75.4
Adjusted Operating Revenue									2,431.3	2,509.7	2,529.6
Adjusted Operating Income (Loss)									241.4	137.7	125.5
Interest and Debt Expense									3.1	5.3	6.9
Depreciation and Amortization									5.9	7.7	8.3
Operating Segments | Corporate and Other Segment
Segment Reporting Information
Premium Income									0	0	0
Net Investment Income									9.8	20.5	29.5
Other Income									1.1	3.1	2.7
Adjusted Operating Revenue									10.9	23.6	32.2
Adjusted Operating Income (Loss)									(200.8)	(188.6)	(171.1)
Interest and Debt Expense									185.1	172.1	160.4
Depreciation and Amortization									$ 0.7	$ 1.7	$ 1

Segment Information Deferred Ac

Segment Information Deferred Acquisition Costs by Segment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Movement Analysis of Deferred Policy Acquisition Costs
Deferred Acquisition Costs at Beginning of Year	$ 2,324
Deferred Policy Acquisition Costs, Amortization Expense	(606.1)	$ (609.9)	$ (565.5)
Deferred Acquisition Costs at End of Year	2,272.6	2,324
Operating Segments
Movement Analysis of Deferred Policy Acquisition Costs
Deferred Acquisition Costs at Beginning of Year	2,324	2,309.4	2,184.6
Deferral of Acquisition Costs	576.2	658.6	668
Deferred Policy Acquisition Costs, Amortization Expense	(606.1)	(609.9)	(565.5)
Adjustment Related to Unrealized Investment Gains and Losses	(22.4)	(34.8)	23.5
Deferred Policy Acquisition Costs Foreign Currency Translation Adjustment And Other	0.9	0.7	(1.2)
Deferred Acquisition Costs at End of Year	2,272.6	2,324	2,309.4
Operating Segments | Unum US
Movement Analysis of Deferred Policy Acquisition Costs
Deferred Acquisition Costs at Beginning of Year	1,223	1,239.4	1,205.4
Deferral of Acquisition Costs	291.5	334.5	344
Deferred Policy Acquisition Costs, Amortization Expense	(341)	(344)	(315.1)
Adjustment Related to Unrealized Investment Gains and Losses	(4.8)	(6.9)	5.1
Deferred Policy Acquisition Costs Foreign Currency Translation Adjustment And Other	0	0	0
Deferred Acquisition Costs at End of Year	1,168.7	1,223	1,239.4
Operating Segments | Unum International
Movement Analysis of Deferred Policy Acquisition Costs
Deferred Acquisition Costs at Beginning of Year	26.4	20	21.3
Deferral of Acquisition Costs	12.1	12.8	8.1
Deferred Policy Acquisition Costs, Amortization Expense	(7.4)	(7.1)	(8.2)
Adjustment Related to Unrealized Investment Gains and Losses	0	0	0
Deferred Policy Acquisition Costs Foreign Currency Translation Adjustment And Other	0.9	0.7	(1.2)
Deferred Acquisition Costs at End of Year	32	26.4	20
Operating Segments | Colonial Life
Movement Analysis of Deferred Policy Acquisition Costs
Deferred Acquisition Costs at Beginning of Year	1,074.6	1,050	957.9
Deferral of Acquisition Costs	272.6	311.3	315.9
Deferred Policy Acquisition Costs, Amortization Expense	(257.7)	(258.8)	(242.2)
Adjustment Related to Unrealized Investment Gains and Losses	(17.6)	(27.9)	18.4
Deferred Policy Acquisition Costs Foreign Currency Translation Adjustment And Other	0	0	0
Deferred Acquisition Costs at End of Year	$ 1,071.9	$ 1,074.6	$ 1,050

Assets by Segment (Detail)

Assets by Segment (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting Information
Total Assets	$ 70,625.8	$ 67,013.4
Operating Segments | Unum US
Segment Reporting Information
Total Assets	19,034.2	18,586.3
Operating Segments | Unum International
Segment Reporting Information
Total Assets	4,206.2	3,869.1
Operating Segments | Colonial Life
Segment Reporting Information
Total Assets	4,864.3	4,629
Operating Segments | Closed Block
Segment Reporting Information
Total Assets	38,187.2	37,008.7
Operating Segments | Corporate and Other Segment
Segment Reporting Information
Total Assets	$ 4,333.9	$ 2,920.3

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													12 Months Ended
	Dec. 31, 2020	[1]	Sep. 30, 2020		Jun. 30, 2020		Mar. 31, 2020	Dec. 31, 2019		Sep. 30, 2019		Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting, Revenue Reconciling Item
Total Revenue	$ 4,273.5		$ 2,996.3		$ 3,021.2		$ 2,871.1	$ 3,034.6		$ 2,960		$ 3,016.7	$ 2,987.6	$ 13,162.1	$ 11,998.9	$ 11,598.5
Net Realized Investment Gain (Loss)	1,304.9		4.4		33.8		(144)	9.2		(26.2)		(7.3)	1.1	1,199.1	(23.2)	(39.5)
Income Before Income Tax	$ 124.7	[2],[3],[4]	$ 299.6	[5]	$ 337.6	[6]	$ 202.1	$ 377.4	[7]	$ 299.4	[8]	$ 352	$ 353.3	964	1,382.1	627.8
Operating Lease, Impairment Loss														(12.7)
Closed Block Individual Disability Reinsurance Transaction
Segment Reporting, Revenue Reconciling Item
Net Realized Investment Gain (Loss)														1,302.3
Amortization of the Cost of Reinsurance														(2.6)
Operating Segments
Segment Reporting, Revenue Reconciling Item
Adjusted Operating Revenue														11,963	12,022.1	11,638
Total Revenue														13,162.1	11,998.9	11,598.5
Net Realized Investment Gain (Loss)														1,199.1	(23.2)	(39.5)
Income Before Income Tax														964	1,382.1	627.8
Long-term Care Reserve Increase														(151.5)	0	(750.8)
Reserve Increase for Group Pension, Before Taxes														(17.5)	0	0
Operating Lease, Impairment Loss														(12.7)	0	0
Costs Related to Organizational Design Update														(23.3)
Costs Related to Early Retirement of Debt														0	(27.3)	0
Adjusted Operating Income														1,278	1,432.6	1,418.1
Operating Segments | Closed Block Individual Disability Reinsurance Transaction
Segment Reporting, Revenue Reconciling Item
Net Realized Investment Gain (Loss)														1,302.3	0	0
Change in Benefit Reserves and Transaction Costs														(1,305.5)	0	0
Amortization of the Cost of Reinsurance														(2.6)	0	0
Operating Segments | Unrelated to Significant Transaction
Segment Reporting, Revenue Reconciling Item
Net Realized Investment Gain (Loss)														$ (103.2)	$ (23.2)	$ (39.5)
[1]	Fourth quarter of 2020 net realized investment gain of $1,302.3 million before tax and $1,028.8 million after tax, related to the transfer of investments for the Closed Block individual disability reinsurance transaction.
[2]	Fourth quarter of 2020 amortization of the cost of reinsurance related to the Closed Block individual disability reinsurance transaction of $2.6 million before tax and $2.0 million after tax.
[3]	Fourth quarter of 2020 impacts from the Closed Block individual disability reinsurance transaction of $1,305.5 million before tax and $1,031.3 million after tax.
[4]	Fourth quarter of 2020 reserve increases of $151.5 million and $17.5 million before tax and $119.7 million and $13.8 million after tax related to long-term care and group pension, respectively.
[5]	Third quarter of 2020 costs related to organizational design update of $23.3 million before tax and $18.6 million after tax.
[6]	Second quarter of 2020 impairment on ROU asset related to an operating lease for office space that we do not plan to continue using to support our general operations of $12.7 million before tax and $10.0 million after tax.
[7]	Fourth quarter of 2019 cost related to the early retirement of debt of $2.1 million before tax and $1.7 million after tax.
[8]	Third quarter of 2019 cost related to the early retirement of debt of $25.2 million before tax and $19.9 million after tax.

Segment Information Segments -

Segment Information Segments - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)Integer	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2019USD ($)	Nov. 01, 2018Rate	Oct. 01, 2018Rate	Jan. 01, 2018Rate
Segment Reporting [Abstract]
Number of Operating Segments | Integer	3
Supplementary Insurance Information, by Segment
Goodwill	$ 353			$ 351.7
Operating Segments
Supplementary Insurance Information, by Segment
Costs Related to Organizational Design Update	(23.3)
Unum US
Supplementary Insurance Information, by Segment
Goodwill	280			280
Unum International
Supplementary Insurance Information, by Segment
Goodwill	45.3			44
Colonial Life
Supplementary Insurance Information, by Segment
Goodwill	$ 27.7			$ 27.7
Jaimini Health, Inc.
Supplementary Insurance Information, by Segment
Percentage Ownership of Acquired Business | Rate					100.00%
Name of Acquired Businesses		Jaimini Health, Inc. (Jaimini Health)
Unum Poland
Supplementary Insurance Information, by Segment
Percentage Ownership of Acquired Business | Rate						100.00%
Name of Acquired Businesses		Unum Poland
Leavelogic Inc.
Supplementary Insurance Information, by Segment
Percentage Ownership of Acquired Business | Rate							100.00%
Name of Acquired Businesses		Leavelogic, Inc (Leavelogic)
Series of Individually Immaterial Business Acquisitions
Supplementary Insurance Information, by Segment
Business Acquisition, Revenue Reported by Acquired Entity for Last Annual Period			$ 61
Assets of Acquiree at Acquisition Date		$ 344
Liabilities of Acquiree at Acquisition Date		206
Total Cash Purchase Price to Acquire Business		151
Goodwill		$ 13

Leases, Cost (Details)

Leases, Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Leases [Abstract]
Operating Lease Cost	$ 48.6	$ 29.4
Sublease Income	1.3	1.9
Total Lease Cost	47.3	27.5
Cash Paid for Amounts Included in the Measurement of Lease Liabilities	$ 30.8	$ 28.9
Weighted-Average Remaining Lease Term	6 years	7 years
Weighted-Average Discount Rate	4.37%	4.60%
Operating Lease Cost Prior to ASC 842			$ 29.2

Lessee, Operating Lease, Liabil

Lessee, Operating Lease, Liability, Payment, Due (Details) $ in Millions	Dec. 31, 2020USD ($)
Leases [Abstract]
Lessee, Operating Lease, Liability, Payments, Due Next Twelve Months	$ 25.4
Lessee, Operating Lease, Liability, Payments, Due Year Two	22.8
Lessee, Operating Lease, Liability, Payments, Due Year Three	16.5
Lessee, Operating Lease, Liability, Payments, Due Year Four	12.7
Lessee, Operating Lease, Liability, Payments, Due Year Five	9.8
Lessee, Operating Lease, Liability, Payments, Due after Year Five	34.4
Lessee, Operating Lease, Liability, Payments, Due	121.6
Sales-type and Direct Financing Leases, Lease Receivable, Undiscounted Excess Amount	15.7
Operating Lease, Liability	$ 105.9

Leases - Additional Information

Leases - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Lessee, Lease, Description
Operating Lease, Right-of-Use Asset	$ 82.9	$ 108.6
Operating Lease, Impairment Loss	$ 12.7
Minimum | Land and Building
Lessee, Lease, Description
Lessee, Operating Lease, Term of Contract	5 years
Minimum | Equipment
Lessee, Lease, Description
Lessee, Operating Lease, Term of Contract	1 year
Maximum | Land and Building
Lessee, Lease, Description
Lessee, Operating Lease, Term of Contract	10 years
Maximum | Equipment
Lessee, Lease, Description
Lessee, Operating Lease, Term of Contract	3 years

Statutory Financial Informati_3

Statutory Financial Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Traditional U.S. Life Insurance Subsidiaries
Statutory Accounting Practices
Statutory Net Income (Loss)	$ 646.8	$ 982.1	$ 953
Statutory Combined Net Gain (Loss) from Operations	726.2	1,027.2	959.8
Statutory Combined Capital and Surplus	3,875	3,644.4
Captive Reinsurers
Statutory Accounting Practices
Statutory Net Income (Loss)	(201)	(122.5)	(109.6)
Statutory Combined Net Gain (Loss) from Operations	(149.4)	(108.4)	$ (110.9)
Statutory Combined Capital and Surplus	$ 2,088	$ 1,908.3

Statutory Financial Informati_4

Statutory Financial Information - Additional Details (Detail) £ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2019GBP (£)	Dec. 31, 2018USD ($)	Dec. 31, 2020GBP (£)	Dec. 31, 2019GBP (£)
Unum Life Insurance Company of America
Statutory Accounting Practices
Statutory Accounting Practices, Permitted Practice, Reserve Deficiency				$ 2,100
Statutory Accounting Practices, Permitted Practice, Amount	$ 229
Fairwind Insurance Company
Statutory Accounting Practices
Statutory Accounting Practices, Permitted Practice, Amount	287	$ 194
Unum Limited
Statutory Accounting Practices
Statutory Net Income | £			£ 91
Statutory Combined Capital and Surplus | £						£ 656.1
Statutory Accounting Practices, Statutory Amount Available for Dividend Payments | £					£ 170
Traditional U.S. Life Insurance Subsidiaries
Statutory Accounting Practices
Statutory Net Income	646.8	982.1		$ 953
Statutory Combined Capital and Surplus	3,875	3,644.4
Statutory Accounting Practices, Statutory Amount Available for Dividend Payments	974
Cash and Securities Segregated under Federal and Other Regulations	$ 135.5	$ 135.2

Schedule of Unaudited Quarterly

Schedule of Unaudited Quarterly Results (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended													12 Months Ended
	Dec. 31, 2020		Sep. 30, 2020		Jun. 30, 2020		Mar. 31, 2020	Dec. 31, 2019		Sep. 30, 2019		Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Selected Quarterly Financial Information [Abstract]
Premium Income	$ 2,319.9		$ 2,318.1		$ 2,368.7		$ 2,371.4	$ 2,352.6		$ 2,331.2		$ 2,343.1	$ 2,338.7	$ 9,378.1	$ 9,365.6	$ 8,986.1
Net Investment Income	593.5		613.2		569		585	616.3		599.4		624.9	594.7	2,360.7	2,435.3	2,453.7
Net Realized Investment Gain (Loss)	1,304.9	[1]	4.4		33.8		(144)	9.2		(26.2)		(7.3)	1.1	1,199.1	(23.2)	(39.5)
Total Revenue	4,273.5	[1]	2,996.3		3,021.2		2,871.1	3,034.6		2,960		3,016.7	2,987.6	13,162.1	11,998.9	11,598.5
Income Before Income Tax	124.7	[1],[2],[3],[4]	299.6	[5]	337.6	[6]	202.1	377.4	[7]	299.4	[8]	352	353.3	964	1,382.1	627.8
Net Income	$ 135.4	[1],[2],[3],[4],[9]	$ 231.1	[5]	$ 265.5	[6]	$ 161	$ 296.2	[7]	$ 242	[8]	$ 281.2	$ 280.9	$ 793	$ 1,100.3	$ 523.4
Basic Earnings Per Share	$ 0.66	[1],[2],[3],[4],[9]	$ 1.13	[5]	$ 1.30	[6]	$ 0.79	$ 1.44	[7]	$ 1.16	[8]	$ 1.33	$ 1.31	$ 3.89	$ 5.25	$ 2.38
Diluted Earnings Per Share	$ 0.66	[1],[2],[3],[4],[9]	$ 1.13	[5]	$ 1.30	[6]	$ 0.79	$ 1.44	[7]	$ 1.16	[8]	$ 1.33	$ 1.31	$ 3.89	$ 5.24	$ 2.38
[1]	Fourth quarter of 2020 net realized investment gain of $1,302.3 million before tax and $1,028.8 million after tax, related to the transfer of investments for the Closed Block individual disability reinsurance transaction.
[2]	Fourth quarter of 2020 amortization of the cost of reinsurance related to the Closed Block individual disability reinsurance transaction of $2.6 million before tax and $2.0 million after tax.
[3]	Fourth quarter of 2020 impacts from the Closed Block individual disability reinsurance transaction of $1,305.5 million before tax and $1,031.3 million after tax.
[4]	Fourth quarter of 2020 reserve increases of $151.5 million and $17.5 million before tax and $119.7 million and $13.8 million after tax related to long-term care and group pension, respectively.
[5]	Third quarter of 2020 costs related to organizational design update of $23.3 million before tax and $18.6 million after tax.
[6]	Second quarter of 2020 impairment on ROU asset related to an operating lease for office space that we do not plan to continue using to support our general operations of $12.7 million before tax and $10.0 million after tax.
[7]	Fourth quarter of 2019 cost related to the early retirement of debt of $2.1 million before tax and $1.7 million after tax.
[8]	Third quarter of 2019 cost related to the early retirement of debt of $25.2 million before tax and $19.9 million after tax.
[9]	Fourth quarter of 2020 net tax benefit from the Closed Block individual disability reinsurance transaction of $36.5 million.

Schedule I - Summary of Inves_2

Schedule I - Summary of Investments, Other Than Investments in Related Parties Schedule I - Summary of Investments, Other Than Investments in Related Parties (Details) $ in Millions	Dec. 31, 2020USD ($)
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost of Investments	$ 45,064.3	[1]
Amount Shown on the Balance Sheet	52,683.5
United States Government and Government Agencies and Authorities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost of Investments	559	[1]
Fair Value of Investments	709.8
Amount Shown on the Balance Sheet	709.8
States, Municipalities, and Political Subdivisions
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost of Investments	3,609.9	[1]
Fair Value of Investments	4,261.2
Amount Shown on the Balance Sheet	4,261.2
Foreign Governments
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost of Investments	902.9	[1]
Fair Value of Investments	1,168.2
Amount Shown on the Balance Sheet	1,168.2
Public Utilities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost of Investments	5,486.4	[1]
Fair Value of Investments	6,962.3
Amount Shown on the Balance Sheet	6,962.3
Mortgage/Asset-backed Securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost of Investments	1,019.9	[1]
Fair Value of Investments	1,107.7
Amount Shown on the Balance Sheet	1,107.7
All Other Corporate Bonds
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost of Investments	24,958.8	[1]
Fair Value of Investments	29,918.6
Amount Shown on the Balance Sheet	29,918.6
Redeemable Preferred Stock
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost of Investments	9.6	[1]
Fair Value of Investments	9.5
Amount Shown on the Balance Sheet	9.5
Fixed Maturities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost of Investments	36,546.5	[1]
Fair Value of Investments	44,137.3
Amount Shown on the Balance Sheet	44,137.3
Mortgages
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost of Investments	2,445.2	[1]
Amount Shown on the Balance Sheet	2,432.1
Policy Loans
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost of Investments	3,683.9	[1]
Amount Shown on the Balance Sheet	3,683.9
Derivatives
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost of Investments	0	[1]
Amount Shown on the Balance Sheet	19.8	[2]
Equity Securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost of Investments	32.6	[1]
Amount Shown on the Balance Sheet	28.3	[3]
Private Equity Partnerships
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost of Investments	720.9
Amount Shown on the Balance Sheet	747.5	[3]
Miscellaneous Long-term Investments
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost of Investments	165.2	[1]
Amount Shown on the Balance Sheet	164.6	[3]
Short-term Investments
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost of Investments	1,470	[1]
Amount Shown on the Balance Sheet	$ 1,470
[1]	The amortized cost for fixed maturity securities and mortgage loans represents original cost reduced by repayments, write-downs from declines in fair value, amortization of premiums, and/or accretion of discounts. The amortized cost for these investments does not include allowance for expected credit losses.
[2]	Derivatives are carried at fair value.
[3]	The difference between amortized cost and carrying value for private equity partnerships and perpetual preferred equity securities primarily results from changes in the partnership owner's equity and the issuer's equity since acquisition, respectively.

Parent Company Balance Sheet (D

Parent Company Balance Sheet (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Condensed Balance Sheet Statements, Captions
Amortized Cost of Fixed Maturity Securities	$ 36,546.5	$ 41,079.3
Assets
Fixed Maturity Securities - at fair value (amortized cost: $349.5; $122.3)	44,137.3	47,443.7
Other Long-term Investments	960.2	844.2
Short-term Investments	1,470	1,294.5
Other Assets	1,752.3	884
Total Assets	70,625.8	67,013.4
Liabilities
Short-term debt	0	399.7
Long-term Debt	3,345.7	2,926.9
Other Liabilities	2,471.4	1,880.5
Total Liabilities	59,754.8	57,048.4
Stockholders' Equity
Common Stock	30.7	30.6
Additional Paid-in Capital	2,376.2	2,348.1
Accumulated Other Comprehensive Income	374.2	37.3
Retained Earnings	11,269.6	10,728.7
Treasury Stock	(3,179.7)	(3,179.7)
Total Stockholders' Equity	10,871	9,965	$ 8,621.8
Total Liabilities and Stockholders' Equity	70,625.8	67,013.4
Parent Company
Condensed Balance Sheet Statements, Captions
Amortized Cost of Fixed Maturity Securities	349.5	122.3
Assets
Fixed Maturity Securities - at fair value (amortized cost: $349.5; $122.3)	355.1	125.6
Other Long-term Investments	10.6	35.2
Short-term Investments	164.5	604.4
Investments in Subsidiaries	14,122.6	12,820.9
Deferred Income Tax Assets, Net	158.8	122.7
Other Assets	496.7	488.9
Total Assets	15,308.3	14,197.7
Liabilities
Short-term debt	0	399.7
Long-term Debt	3,345.7	2,846.9
Pension and Postretirement Benefits	677.5	624.2
Other Liabilities	414.1	361.9
Total Liabilities	4,437.3	4,232.7
Stockholders' Equity
Common Stock	30.7	30.6
Additional Paid-in Capital	2,376.2	2,348.1
Accumulated Other Comprehensive Income	374.2	37.3
Retained Earnings	11,269.6	10,728.7
Treasury Stock	(3,179.7)	(3,179.7)
Total Stockholders' Equity	10,871	9,965
Total Liabilities and Stockholders' Equity	$ 15,308.3	$ 14,197.7

Parent Company Statement of Inc

Parent Company Statement of Income (Detail) - USD ($) $ in Millions	3 Months Ended													12 Months Ended
	Dec. 31, 2020	[1]	Sep. 30, 2020		Jun. 30, 2020		Mar. 31, 2020	Dec. 31, 2019		Sep. 30, 2019		Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Condensed Income Statements, Captions
Other Income														$ 224.2	$ 221.2	$ 198.2
Total Revenue	$ 4,273.5		$ 2,996.3		$ 3,021.2		$ 2,871.1	$ 3,034.6		$ 2,960		$ 3,016.7	$ 2,987.6	13,162.1	11,998.9	11,598.5
Cost Related to Early Retirement of Debt														0	27.3	0
Income Before Income Tax	124.7	[2],[3],[4]	299.6	[5]	337.6	[6]	202.1	377.4	[7]	299.4	[8]	352	353.3	964	1,382.1	627.8
Income Tax Benefit														171	281.8	104.4
Net Income	$ 135.4	[2],[3],[4],[9]	$ 231.1	[5]	$ 265.5	[6]	$ 161	$ 296.2	[7]	$ 242	[8]	$ 281.2	$ 280.9	793	1,100.3	523.4
Other Comprehensive Income (Loss), Net of Tax														336.9	851.5	(924.2)
Comprehensive Income (Loss)														1,129.9	1,951.8	(400.8)
Parent Company
Condensed Income Statements, Captions
Cash Dividends from Subsidiaries														974.6	1,089.4	1,135.4
Other Income														51.7	63.9	66.6
Total Revenue														1,026.3	1,153.3	1,202
Interest and Debt Expense														187.1	173.2	161.4
Cost Related to Early Retirement of Debt														0	27.3	0
Other Expenses														51.1	53.4	53.4
Operating Expenses, Total														238.2	253.9	214.8
Income Before Income Tax														788.1	899.4	987.2
Income Tax Benefit														(15.3)	(21.5)	(1.7)
Income of Parent Company														803.4	920.9	988.9
Equity in Undistributed Earnings (Loss) of Subsidiaries														(10.4)	179.4	(465.5)
Net Income														793	1,100.3	523.4
Other Comprehensive Income (Loss), Net of Tax														336.9	851.5	(924.2)
Comprehensive Income (Loss)														$ 1,129.9	$ 1,951.8	$ (400.8)
[1]	Fourth quarter of 2020 net realized investment gain of $1,302.3 million before tax and $1,028.8 million after tax, related to the transfer of investments for the Closed Block individual disability reinsurance transaction.
[2]	Fourth quarter of 2020 amortization of the cost of reinsurance related to the Closed Block individual disability reinsurance transaction of $2.6 million before tax and $2.0 million after tax.
[3]	Fourth quarter of 2020 impacts from the Closed Block individual disability reinsurance transaction of $1,305.5 million before tax and $1,031.3 million after tax.
[4]	Fourth quarter of 2020 reserve increases of $151.5 million and $17.5 million before tax and $119.7 million and $13.8 million after tax related to long-term care and group pension, respectively.
[5]	Third quarter of 2020 costs related to organizational design update of $23.3 million before tax and $18.6 million after tax.
[6]	Second quarter of 2020 impairment on ROU asset related to an operating lease for office space that we do not plan to continue using to support our general operations of $12.7 million before tax and $10.0 million after tax.
[7]	Fourth quarter of 2019 cost related to the early retirement of debt of $2.1 million before tax and $1.7 million after tax.
[8]	Third quarter of 2019 cost related to the early retirement of debt of $25.2 million before tax and $19.9 million after tax.
[9]	Fourth quarter of 2020 net tax benefit from the Closed Block individual disability reinsurance transaction of $36.5 million.

Parent Company Cash Flow Statem

Parent Company Cash Flow Statement (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Condensed Cash Flow Statements, Captions
Cash Provided by Operating Activities	$ 597.5	$ 1,741.6	$ 1,536.5
Cash Flows from Investing Activities
Proceeds from Maturities of Fixed Maturity Securities	2,052.4	2,401	2,815.4
Proceeds from Sales and Maturities of Other Investments	237	363.5	454
Purchase of Fixed Maturity Securities	(3,169.6)	(4,022.4)	(3,861.7)
Purchase of Other Investments	(440.6)	(568.5)	(623.2)
Net Sales (Purchases) of Short-term Investments	(133.1)	(267.6)	200.5
Net Purchases of Property and Equipment	(119.1)	(150.9)	(144.1)
Cash Used by Investing Activities	(267.7)	(1,393.5)	(930.1)
Cash Flows from Financing Activities
Short-term Debt Repayment	(400)	0	(200)
Issuance of Long-term Debt	494.1	841.9	290.7
Long-term Debt Repayment	(80)	(493.1)	(60)
Cost Related to Early Retirement of Debt	0	25.9	0
Issuance of Common Stock	4.4	6.1	4.6
Repurchase of Common Stock	0	(400.3)	(356.2)
Dividends Paid to Stockholders	(231.9)	(229.2)	(215.6)
Other, Net	(65.6)	(57.5)	(53.3)
Cash Used by Financing Activities	(216.9)	(358)	(589.8)
Net Increase (Decrease) in Cash and Bank Deposits	112.9	(9.9)	16.6
Parent Company
Condensed Cash Flow Statements, Captions
Cash Provided by Operating Activities	964	1,000	1,052.1
Cash Flows from Investing Activities
Proceeds from Maturities of Fixed Maturity Securities	138.8	16.6	52.5
Proceeds from Sales and Maturities of Other Investments	46.6	5.6	0
Purchase of Fixed Maturity Securities	(384.7)	0	(47.9)
Purchase of Other Investments	(22)	0	(22.3)
Net Sales (Purchases) of Short-term Investments	440.6	(309)	192.6
Cash Distributions to Subsidiaries	(965.5)	(389)	(530.8)
Net Purchases of Property and Equipment	(81.6)	(85.9)	(73.2)
Acquisition of Business	0	0	(146.1)
Cash Used by Investing Activities	(827.8)	(761.7)	(575.2)
Cash Flows from Financing Activities
Short-term Debt Repayment	(400)	0	(200)
Issuance of Long-term Debt	494.1	841.9	290.7
Long-term Debt Repayment	0	(433.1)	0
Cost Related to Early Retirement of Debt	0	25.9	0
Issuance of Common Stock	4.4	6.1	4.6
Repurchase of Common Stock	0	(400.3)	(356.2)
Dividends Paid to Stockholders	(231.9)	(229.2)	(215.6)
Other, Net	(1.4)	(3.7)	(9.3)
Cash Used by Financing Activities	(134.8)	(244.2)	(485.8)
Net Increase (Decrease) in Cash and Bank Deposits	$ 1.4	$ (5.9)	$ (8.9)

Parent Company Debt Schedule (D

Parent Company Debt Schedule (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument
Long-term Debt, Excluding Current Maturities	$ 3,345.7	$ 2,926.9
Debt Instrument, Unamortized Premium (Discount), Net	6	8.4
Short-term Debt, outstanding principal	0
Debt Issuance Costs, Noncurrent, Net	(34.8)	(35.4)
Debt Issuance Costs, Current, Net	0	(0.3)
Fair Value Hedge Adjustment, LT Debt
Debt Instrument
Long-term Debt, Excluding Current Maturities	0	(0.6)
Parent Company
Debt Instrument
Long-term Debt, Excluding Current Maturities	3,345.7	2,846.9
Debt Instrument, Unamortized Premium (Discount), Net	6	8.4
Debt Issuance Costs, Noncurrent, Net	(34.8)	(35.4)
Debt Issuance Costs, Current, Net	0	(0.3)
Debt, Long-term and Short-term, Combined Amount	3,345.7	3,246.6
Parent Company | Fair Value Hedge Adjustment, LT Debt
Debt Instrument
Long-term Debt, Excluding Current Maturities	0	(0.6)
Notes Issued in 1998 with 2028 Maturity Date | Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	335.8	335.8
Notes Issued in 1998 with 2028 Maturity Date | Parent Company | Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	335.8	335.8
Notes Issued in 2002 | Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	39.5	39.5
Notes Issued in 2002 | Parent Company | Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	39.5	39.5
Notes Issued in 2012 and 2016 | Parent Company | Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	500	500
Notes Issued in 2014 | Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	350	350
Notes Issued in 2014 | Parent Company | Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	350	350
Notes Issued in 2015 | Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	275	275
Notes Issued in 2015 | Parent Company | Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	275	275
Notes Issued in 2019 | Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	400	400
Notes Issued in 2019 | Parent Company | Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	400	400
Notes Issued in 2019 due 2049 | Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	450	450
Notes Issued in 2019 due 2049 | Parent Company | Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	450	450
Notes Issued in 2020 due 2025 | Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	500	0
Notes Issued in 2020 due 2025 | Parent Company | Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	500	0
Notes Issued 1990 to 1996 | Medium-term Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	20.5	20.5
Notes Issued 1990 to 1996 | Parent Company | Medium-term Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	20.5	20.5
Notes Issued in 1998 with 2038 Maturity Date | Junior Subordinated Debt
Debt Instrument
Long-term Debt, Excluding Current Maturities	203.7	203.7
Notes Issued in 1998 with 2038 Maturity Date | Parent Company | Junior Subordinated Debt
Debt Instrument
Long-term Debt, Excluding Current Maturities	203.7	203.7
Notes Issued in 2018 with a 2058 Maturity Date | Junior Subordinated Debt
Debt Instrument
Long-term Debt, Excluding Current Maturities	300	300
Notes Issued in 2018 with a 2058 Maturity Date | Parent Company | Junior Subordinated Debt
Debt Instrument
Long-term Debt, Excluding Current Maturities	300	300
Notes Issued in 2010 | Senior Notes
Debt Instrument
Short-term Debt, outstanding principal		400
Notes Issued in 2010 | Senior Notes | Parent Company
Debt Instrument
Short-term Debt, outstanding principal	$ 0	$ 400

Parent Company Notes - Addition

Parent Company Notes - Additional Details (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 1998	Dec. 31, 2017
Repayments of Principal in 2023	$ 2,000,000
Repayments of Principal in 2024	350,000,000
Repayments of Principal in 2025	775,000,000
Repayments of Principal Thereafter	2,247,500,000
Short-term debt	0	$ 399,700,000
Derivative, Notional Amount	744,400,000	881,400,000	$ 799,200,000		$ 904,500,000
Notional Amount Of Derivatives Terminations	$ 257,300,000	471,500,000	241,800,000
Unum Group Percentage Ownership of Provident Financing Trust	100.00%
Cost Related to Early Retirement of Debt	$ 0	27,300,000	0
Interest Paid, Including Capitalized Interest, Operating and Investing Activities	178,100,000	172,900,000	167,300,000
Parent Company
Repayments of Principal in 2023	2,000,000
Repayments of Principal in 2024	350,000,000
Repayments of Principal in 2025	775,000,000
Repayments of Principal Thereafter	2,247,500,000
Short-term debt	$ 0	399,700,000
Unum Group Percentage Ownership of Provident Financing Trust	100.00%
Cost Related to Early Retirement of Debt	$ 0	27,300,000	0
Interest Paid, Including Capitalized Interest, Operating and Investing Activities	176,600,000	168,400,000	161,400,000
Parent Company | Five-year Unsecured Revolving Credit Facility
Line of Credit Facility, Maximum Borrowing Capacity	500,000,000
Letters of Credit Outstanding	0
Parent Company | Three-year Unsecured Revolving Credit Facility
Line of Credit Facility, Maximum Borrowing Capacity	100,000,000
Letters of Credit Outstanding	$ 0
Notes Issued in 2010 | Senior Notes
Stated Interest Rate of Debt	5.625%
Notes Issued in 2010 | Senior Notes | Parent Company
Short-term debt	$ 400,000,000
Stated Interest Rate of Debt	5.625%
Notes Issued in 2020 due 2025 | Senior Notes
Stated Interest Rate of Debt	4.50%
Notes Issued in 2020 due 2025 | Senior Notes | Parent Company
Proceeds from Issuance of Debt	$ 500,000,000
Stated Interest Rate of Debt	4.50%
Medium Term Notes Payable Due 2028 | Medium-term Notes
Extinguishment of Debt, Amount		$ 30,300,000
Stated Interest Rate of Debt		7.19%
Medium Term Notes Payable Due 2028 | Parent Company | Medium-term Notes
Extinguishment of Debt, Amount		$ 30,300,000
Stated Interest Rate of Debt		7.19%
Notes Issued in 1998 with 2028 Maturity Date | Senior Notes
Extinguishment of Debt, Amount	$ 30,000,000
Stated Interest Rate of Debt		7.25%
Notes Issued in 1998 with 2028 Maturity Date | Parent Company | Senior Notes
Extinguishment of Debt, Amount		$ 30,000,000
Stated Interest Rate of Debt		7.25%
Senior Notes Payable due 2021 | Senior Notes
Extinguishment of Debt, Amount		$ 350,000,000
Stated Interest Rate of Debt		3.00%
Senior Notes Payable due 2021 | Parent Company | Senior Notes
Extinguishment of Debt, Amount		$ 350,000,000
Stated Interest Rate of Debt		3.00%
Notes Issued in 2019 due 2049 | Senior Notes
Proceeds from Issuance of Debt		$ 450,000,000
Stated Interest Rate of Debt		4.50%
Notes Issued in 2019 due 2049 | Senior Notes | Parent Company
Proceeds from Issuance of Debt		$ 450,000,000
Stated Interest Rate of Debt		4.50%
Notes Issued in 2019 | Senior Notes
Proceeds from Issuance of Debt		$ 400,000,000
Stated Interest Rate of Debt		4.00%
Notes Issued in 2019 | Senior Notes | Parent Company
Proceeds from Issuance of Debt		$ 400,000,000
Stated Interest Rate of Debt		4.00%
Notes Issued in 1998 with 2018 Maturity Date | Parent Company
Short-term debt			$ 200,000,000
Stated Interest Rate of Debt			7.00%
Notes Issued in 1998 with 2018 Maturity Date | Senior Notes | Parent Company
Short-term debt			$ 200,000,000
Stated Interest Rate of Debt			7.00%
Notes Issued in 2018 with a 2058 Maturity Date | Junior Subordinated Debt
Proceeds from Issuance of Debt			$ 300,000,000
Stated Interest Rate of Debt			6.25%
Notes Issued in 2018 with a 2058 Maturity Date | Junior Subordinated Debt | Parent Company
Proceeds from Issuance of Debt			$ 300,000,000
Stated Interest Rate of Debt			6.25%
Notes Issued in 1998 with 2038 Maturity Date | Junior Subordinated Debt
Stated Interest Rate of Debt	7.405%
Liquidation value per capital security	$ 1,000
Notes Issued in 1998 with 2038 Maturity Date | Junior Subordinated Debt | Parent Company
Proceeds from Issuance of Debt				$ 300,000,000
Stated Interest Rate of Debt	7.405%	7.405%
Liquidation value per capital security	$ 1,000
Junior Subordinated Notes Payable Due 2038 | Junior Subordinated Debt
Extinguishment of Debt, Amount		$ 22,800,000
Stated Interest Rate of Debt	7.405%
Junior Subordinated Notes Payable Due 2038 | Parent Company | Junior Subordinated Debt
Extinguishment of Debt, Amount	$ 22,800,000
Stated Interest Rate of Debt	7.405%
Capital Securities Notes Payable Due 2038
Extinguishment of Debt, Amount		$ 22,800,000
Stated Interest Rate of Debt		7.405%
Capital Securities Notes Payable Due 2038 | Parent Company
Extinguishment of Debt, Amount	$ 22,800,000
Receive Fixed/Pay Variable | Interest Rate Swaps
Derivative, Notional Amount	0	$ 250,000,000	$ 250,000,000		$ 250,000,000
Notional Amount Of Derivatives Terminations	$ 250,000,000	0	$ 0
Receive Fixed/Pay Variable | Interest Rate Swaps | Parent Company
Derivative, Notional Amount		$ 250,000,000

Schedule III Supplementary In_2

Schedule III Supplementary Insurance Information (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020		Dec. 31, 2019	Dec. 31, 2018
Supplementary Insurance Information, by Segment
Deferred Acquisition Costs		$ 2,272.6		$ 2,324
Reserves for Future Policy Contract Benefits		49,653		47,780.1
Unearned Premiums		349.3		363.9
Policy and Contract Benefits		1,855.4		1,745.5
Premium Income		9,378.1		9,365.6	$ 8,986.1
Net Investment Income	[1]	2,360.7		2,435.3	2,453.7
Benefits and Change in Reserves for Future Benefits		8,972.9	[2]	7,496.2	8,020.4	[2]
Amortization of Deferred Acquisition Costs		606.1		609.9	565.5
All Other Expenses	[3]	2,619.1		2,510.7	2,384.8
Unum US
Supplementary Insurance Information, by Segment
Deferred Acquisition Costs		1,168.7		1,223
Reserves for Future Policy Contract Benefits		11,681.4		11,367.8
Unearned Premiums		44		46
Policy and Contract Benefits		1,191.2		1,117.5
Premium Income		6,018.9		6,016.6	5,736.4
Net Investment Income		720.3		739.4	778.7
Benefits and Change in Reserves for Future Benefits		4,138.7		4,022.1	3,856.5
Amortization of Deferred Acquisition Costs		341		344	315.1
All Other Expenses		1,589		1,501.6	1,447.4
Premiums Written	[4]	4,088.6		4,073.9	3,873
Unum International
Supplementary Insurance Information, by Segment
Deferred Acquisition Costs		32		26.4
Reserves for Future Policy Contract Benefits		2,794.2		2,566.6
Unearned Premiums		123.3		129.9
Policy and Contract Benefits		175.6		157.3
Premium Income		652.8		630.5	568.8
Net Investment Income		104.6		122.5	117.2
Benefits and Change in Reserves for Future Benefits		500.9		469.8	419.8
Amortization of Deferred Acquisition Costs		7.4		7.1	8.2
All Other Expenses		173		168.8	144.5
Premiums Written	[4]	456		443.7	455.5
Colonial Life
Supplementary Insurance Information, by Segment
Deferred Acquisition Costs		1,071.9		1,074.6
Reserves for Future Policy Contract Benefits		2,628.5		2,477.2
Unearned Premiums		36.9		36.8
Policy and Contract Benefits		217.2		189.4
Premium Income		1,712		1,685	1,603.8
Net Investment Income		155.7		148	151.2
Benefits and Change in Reserves for Future Benefits		906.5		865	824.9
Amortization of Deferred Acquisition Costs		257.7		258.8	242.2
All Other Expenses		369.2		368.1	353.9
Premiums Written	[4]	1,252.4		1,249.6	1,277.3
Closed Block
Supplementary Insurance Information, by Segment
Deferred Acquisition Costs		0		0
Reserves for Future Policy Contract Benefits		32,548.9		31,368.5
Unearned Premiums		145.1		151.2
Policy and Contract Benefits		271.4		281.3
Premium Income		994.4		1,033.5	1,077.1
Net Investment Income		1,370.3		1,404.9	1,377.1
Benefits and Change in Reserves for Future Benefits		3,426.8	[2]	2,139.3	2,919.2	[2]
Amortization of Deferred Acquisition Costs		0		0	0
All Other Expenses		240.2	[3]	232.7	235.7
Premiums Written	[4]	979.3		1,020.8	1,065.7
Corporate and Other Segment
Supplementary Insurance Information, by Segment
Premium Income		0		0	0
Net Investment Income		9.8		20.5	29.5
Benefits and Change in Reserves for Future Benefits		0		0	0
Amortization of Deferred Acquisition Costs		0		0	0
All Other Expenses		247.7	[3]	239.5	203.3
Premiums Written	[4]	$ 0		$ 0	$ 0
[1]	Net investment income is allocated based upon segmentation. Each segment has its own specifically identified assets and receives the investment income generated by those assets.
[2]	Included in 2020 and 2018 are reserve increases of $151.5 million and $750.8 million, respectively in the Closed Block segment related to our long-term care business, as well as a reserve increase of $17.5 million in 2020 related to our group pension Closed Block business. Also included in 2020 is an increase in benefits and change in reserves for future benefits of $1,284.5 million in 2020 resulting from the recognition of the adjustment related to unrealized investment gains and losses previously recognized in accumulated other comprehensive income related to the Closed Block individual disability reinsurance transaction.
[3]	Includes commissions, interest and debt expense, cost related to early retirement of debt, deferral of acquisition costs, compensation expense, and other expenses. Where not directly attributable to a segment, expenses are generally allocated based on activity levels, time information, and usage statistics. Included in 2020 is the amortization of the cost of reinsurance of $2.6 million and transaction costs of $21.0 million related to the Closed Block individual disability reinsurance transaction. Also included in 2020 is a ROU asset impairment of $12.7 million related to one of our operating leases for office space that we do not plan to continue using to support general operations and costs related to organizational design updates of $23.3 million in Corporate.
[4]	Excludes life insurance.

Schedule IV Reinsurance (Detail

Schedule IV Reinsurance (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reinsurance Premiums for Insurance Companies, by Product Segment
Direct Premiums, Life Insurance in Force	$ 979,755.7				$ 990,371				$ 979,755.7	$ 990,371	$ 937,300.8
Ceded Premiums, Life Insurance in Force	41,550.9				41,669.8				41,550.9	41,669.8	40,902.8
Assumed Premiums, Life Insurance in Force	896.4				1,018.4				896.4	1,018.4	1,089.3
Premiums, Net, Life Insurance in Force	$ 939,101.2				$ 949,719.6				$ 939,101.2	$ 949,719.6	$ 897,487.3
Life Insurance in Force Premiums, Percentage Assumed to Net	0.10%				0.10%				0.10%	0.10%	0.10%
Gross Amount									$ 9,621.9	$ 9,576.3	$ 9,171.1
Reinsurance Ceded									337.9	327.2	327.6
Assumed Premiums Earned									94.1	116.5	142.6
Net Amount	$ 2,319.9	$ 2,318.1	$ 2,368.7	$ 2,371.4	$ 2,352.6	$ 2,331.2	$ 2,343.1	$ 2,338.7	$ 9,378.1	$ 9,365.6	$ 8,986.1
Percentage of Amount Assumed to Net									1.00%	1.20%	1.60%
Life Insurance
Reinsurance Premiums for Insurance Companies, by Product Segment
Gross Amount									$ 2,536.8	$ 2,549.7	$ 2,442.1
Reinsurance Ceded									141.9	137.2	138.2
Assumed Premiums Earned									8	8.2	8.7
Net Amount									$ 2,402.9	$ 2,420.7	$ 2,312.6
Percentage of Amount Assumed to Net									0.30%	0.30%	0.40%
Accident, Health, and Other Insurance
Reinsurance Premiums for Insurance Companies, by Product Segment
Gross Amount									$ 7,085.1	$ 7,026.6	$ 6,729
Reinsurance Ceded									196	190	189.4
Assumed Premiums Earned									86.1	108.3	133.9
Net Amount									$ 6,975.2	$ 6,944.9	$ 6,673.5
Percentage of Amount Assumed to Net									1.20%	1.60%	2.00%

Schedule V Valuation and Qual_2

Schedule V Valuation and Qualifying Accounts (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Real Estate reserve (deducted from other long-term investments)
Valuation and Qualifying Accounts Disclosure
Balance at Beginning of Year		$ 0.3	$ 1.5	$ 4.2
Additions Charged to Costs and Expenses		0	0	0.6
Additions Charged to Other Accounts	[1]	0	0	0
Deductions	[2]	0.3	1.2	3.3
Balance at End of Year		0	0.3	1.5
Allowance for expected credit losses (deducted from accounts and premiums receivable)
Valuation and Qualifying Accounts Disclosure
Balance at Beginning of Year		8.4	9.9	6.4
Additions Charged to Costs and Expenses		34.2	5.3	5.6
Additions Charged to Other Accounts	[1]	0.1	0.1	0
Deductions	[2]	19.3	6.9	2.1
Balance at End of Year		38.8	8.4	$ 9.9
Allowance for expected credit losses (deducted from accounts and premiums receivable) | Accounting Standards Update 2016-13 | Cumulative Effect, Period of Adoption, Adjusted Balance
Valuation and Qualifying Accounts Disclosure
Balance at Beginning of Year	[3]	23.8
Balance at End of Year	[3]		23.8
Allowance for expected credit losses (deducted from reinsurance recoverable)
Valuation and Qualifying Accounts Disclosure
Additions Charged to Costs and Expenses		10.1
Additions Charged to Other Accounts	[1]	0
Deductions	[2]	0.2
Balance at End of Year		11.7
Allowance for expected credit losses (deducted from reinsurance recoverable) | Accounting Standards Update 2016-13 | Cumulative Effect, Period of Adoption, Adjusted Balance
Valuation and Qualifying Accounts Disclosure
Balance at Beginning of Year	[3]	$ 1.8
Balance at End of Year	[3]		$ 1.8
[1]	Additions charged to other accounts are comprised of amounts related to fluctuations in the foreign currency exchange rate.
[2]	Deductions include amounts deemed to reduce exposure of expected losses on premium and accounts receivables and reinsurance recoverable, probable losses on Real Estate reserve, amounts deemed uncollectible, and amounts related to fluctuations in the foreign currency exchange rate.
[3]	ASC 326 "Financial Instruments - Credit Losses" was adopted resulting in a beginning balance adjustment of $13.5 million to Allowance for expected credit losses (deducted from accounts and premiums receivable) and the now separately reported $1.8 million beginning balance for Allowance for expected credit losses (deducted from reinsurance recoverable).

Uncategorized Items - unm-20201

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