Unum (UNM) 10-K 20 Feb 24 2023 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2023	Feb. 16, 2024	Jun. 30, 2023
Entity Information [Line Items]
Document Type	10-K
Document Annual Report	true
Amendment Flag	false
Document Period End Date	Dec. 31, 2023
Document Fiscal Year Focus	2023
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 Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
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
Document Financial Statement Error Correction	false
Entity Shell Company	false
Entity Public Float			$ 9,400,000,000
Entity Common Stock, Shares Outstanding		191,518,006
Auditor Firm ID	42
Auditor Name	Ernst & Young LLP
Auditor Location	Chattanooga, Tennessee
NEW YORK STOCK EXCHANGE, INC. | Common Class A
Entity Information [Line Items]
Title of 12(b) 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(b) 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, 2023	Dec. 31, 2022
Investments
Fixed Maturity Securities - at fair value (amortized cost of $38,410.6; $37,825.2; allowance for credit losses of $2.2; $—)	$ 36,833.9	$ 34,840.8
Mortgage Loans (net of allowance for credit losses of $10.2; $9.3)	2,318.2	2,435.4
Policy Loans	3,620.2	3,601.2
Other Long-term Investments	1,579.4	1,440.1
Short-term Investments	1,610.7	1,394.8
Total Investments	45,962.4	43,712.3
Other Assets
Cash and Bank Deposits	146	119.2
Accounts and Premiums Receivable (net of allowance for credit losses of $29.5; $32.5)	1,543.7	1,482.1
Reinsurance Recoverable (net of allowance for credit losses of $1.7; $1.7)	9,108.4	9,608
Accrued Investment Income	633.9	615
Deferred Acquisition Costs	2,714.5	2,560
Goodwill	349.9	347.6
Property and Equipment	485.3	451.7
Deferred Income Tax Assets, Net	649.4	586
Other Assets	1,661.7	1,666.6	[1]
Total Assets	63,255.2	61,148.5
Liabilities
Future Policy Benefits	40,009.4	38,577.1	[2]
Policyholders' Account Balances	5,667.7	5,740.2	[2]
Unearned Premiums	380.2	365.5
Other Policyholders' Funds	1,615.7	1,750.4
Income Tax Payable	190	190.9
Deferred Income Tax	27	25.2
Short-term debt	0	2
Long-term Debt	3,430.4	3,427.8
Other Liabilities	2,283.4	2,334.4
Total Liabilities	53,603.8	52,413.5
Commitments and Contingent Liabilities - Note 14
Stockholders' Equity
Common Stock, $0.10 par; authorized: 725,000,000 shares; issued: 194,588,625 and 308,306,490 shares	19.4	30.8
Additional Paid-in Capital	1,547.8	2,441
Accumulated Other Comprehensive Loss	(3,308)	(3,448.3)
Retained Earnings	11,431.5	13,141.3
Treasury Stock - at cost: 1,216,528 and 110,551,977 shares	(39.3)	(3,429.8)
Total Stockholders' Equity	9,651.4	8,735
Total Liabilities and Stockholders' Equity	$ 63,255.2	$ 61,148.5
[1] 1 The change in other assets is driven by the cost of reinsurance associated with the second phase of our Closed Block individual disability reinsurance transaction which was completed in the first quarter of 2021. In accordance with the provisions of the ASU related to non-contemporaneous reinsurance, we were then required to establish the ceded reserves using an upper-medium grade fixed-income instrument as of the reinsurance transaction date in March 2021 which resulted in higher ceded reserves compared to that which was reported historically. 2 We previously reported policy and contract benefits and reserves for future policy and contract benefits liabilities in our consolidated balance sheet as of December 31, 2022 of $1,839.8 million and $42,330.2 million, respectively, resulting in total policyholder liabilities of $44,170.0 million. These balances were reclassified into new line items, future policy benefits and policyholders' account balances, which would have reported balances of $38,443.2 million and $5,726.8 million, respectively, as of December 31, 2022, resulting in total policyholder liabilities of $44,170.0 million under the historical accounting method.

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Investments
Amortized Cost of Fixed Maturity Securities	$ 38,410.6	$ 37,825.2
Debt Securities, Available-for-sale, Allowance for Credit Loss for Fixed Maturity Securities	2.2	0
Allowance for credit losses for Mortgage Loans	10.2
Other Assets
Premium Receivable, Allowance for Credit Loss	29.5	32.5
Reinsurance Recoverable, Allowance for Credit Loss	$ 1.7	$ 1.7
Stockholders' Equity, Number of Shares, Par Value and Other Disclosure
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	194,588,625	308,306,490
Treasury Stock, Shares at Cost	1,216,528	110,551,977

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022		Dec. 31, 2021
Revenue
Premium Income	$ 10,046	$ 9,616.5		$ 9,475
Net Investment Income	2,096.7	2,122.2		2,213.2
Net Investment Gain (Loss)	(36)	(15.7)		76.7
Other Income	279.2	261.1		242.9
Total Revenue	12,385.9	11,984.1		12,007.8
Benefits and Expenses
Policy Benefits	7,311.9	7,542.1	[1]	8,113.3	[1]
Policy Benefits - Remeasurement Gain	54.8	547.5		559.9
Commissions	1,170.1	1,086.4		1,038.1
Interest and Debt Expense	194.8	188.5		185
Cost Related to Early Retirement of Debt	0	4.2		67.3
Deferral of Acquisition Costs	(632.2)	(556.9)		(523.2)
Amortization of Deferred Acquisition Costs	481.4	421.1		452.1
Compensation Expense	1,162.6	1,089.5		975.2
Other Expenses	1,112	1,006.7		999.3
Total Benefits and Expenses	10,745.8	10,234.1		10,747.2
Income Before Income Tax	1,640.1	1,750		1,260.6
Income Tax
Current	452	473.5		212.8
Income Tax - Deferred	(95.7)	(130.7)		66.8
Total Income Tax	356.3	342.8		279.6
Net Income	$ 1,283.8	$ 1,407.2		$ 981
Net Income Per Common Share
Basic	$ 6.53	$ 7.01		$ 4.80
Assuming Dilution	$ 6.50	$ 6.96		$ 4.79
[1] 1 Previously disclosed as Benefits and Change in Reserves for Future Benefits

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Statement of Comprehensive Income [Abstract]
Net Income	$ 1,283.8	$ 1,407.2	$ 981
Other Comprehensive Income (Loss)
Change in Net Unrealized Gain (Loss) on Securities (net of tax expense (benefit) of $300.6; $(1,890.8); $(346.9))	1,109.3	(7,042.8)	(1,301.4)
Change in the Effect of Discount Rate Assumptions on the Liability for Future Policy Benefits, Net of Reinsurance (net of tax expense (benefit) of $(256.5); $2,385.1; $622.8)	(962.3)	8,884.6	2,361.8
Change in Net Loss on Hedges (net of tax benefit of $17.0; $19.2; $9.8)	(64.1)	(71.4)	(36)
Change in Foreign Currency Translation Adjustment (net of tax expense (benefit) of $0.9; $(0.1); $4.2)	69	(116)	(12.8)
Change in Unrecognized Pension and Postretirement Benefit Costs (net of tax expense (benefit) of $(2.7); $18.9; $42.1)	11.6	(61.9)	(134)
Total Other Comprehensive Income	140.3	1,716.3	1,145.6
Comprehensive Income	$ 1,424.1	$ 3,123.5	$ 2,126.6

STATEMENT OF COMPREHENSIVE INCO

STATEMENT OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Statement of Comprehensive Income [Abstract]
Change in Net Unrealized Gain on Securities Before Adjustment, Tax Expense (Benefit)	$ 300.6	$ (1,890.8)	$ (346.9)
OCI, Liability for Future Policy Benefit, Gain (Loss), after Reclassification Adjustment, Tax	(256.5)	2,385.1	622.8
Change in Net Gain (Loss) on Hedges, Tax Benefit	(17)	(19.2)	(9.8)
Other Comprehensive Income (Loss), Foreign Currency Translation, Tax Expense (Benefit)	0.9	(0.1)	4.2
Change in Unrecognized Pension and Postretirement Benefit Costs, Tax Expense (Benefit)	$ (2.7)	$ 18.9	$ 42.1

CONSOLIDATED STATEMENTS OF STOC

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Millions	Total		Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Treasury Stock, Common
Balance at Beginning of Year at Dec. 31, 2020			$ 30.7	$ 2,376.2	$ (6,310.2)	$ 11,249	$ (3,179.7)
Increase (Decrease) in Stockholders' Equity
Common Stock Activity			0	31.9
Other Comprehensive Income	$ 1,145.6				1,145.6
Net Income	981					981
Dividends to Stockholders (per common share: $1.39; $1.26; $1.17)						(240.6)
Purchases of Treasury Stock	(50)	[1]					(50)
Treasury Stock, Retired, Cost Method, Amount			0	0		0	0
Balance at End of Year at Dec. 31, 2021	6,033.9		30.7	2,408.1	(5,164.6)	11,989.4	(3,229.7)
Increase (Decrease) in Stockholders' Equity
Common Stock Activity			0.1	32.9
Other Comprehensive Income	1,716.3				1,716.3
Net Income	1,407.2					1,407.2
Dividends to Stockholders (per common share: $1.39; $1.26; $1.17)						(255.3)
Purchases of Treasury Stock	(200.1)	[1]					(200.1)
Treasury Stock, Retired, Cost Method, Amount			0	0		0	0
Balance at End of Year at Dec. 31, 2022	8,735		30.8	2,441	(3,448.3)	13,141.3	(3,429.8)
Increase (Decrease) in Stockholders' Equity
Common Stock Activity			0.1	21.3
Other Comprehensive Income	140.3				140.3
Net Income	1,283.8					1,283.8
Dividends to Stockholders (per common share: $1.39; $1.26; $1.17)						(277.1)
Purchases of Treasury Stock	(252)	[1]					(252)
Treasury Stock, Retired, Cost Method, Amount	(3,642.5)		(11.5)	(914.5)		(2,716.5)	(3,642.5)
Balance at End of Year at Dec. 31, 2023	$ 9,651.4		$ 19.4	$ 1,547.8	$ (3,308)	$ 11,431.5	$ (39.3)
[1]Includes $0.1 million of commissions for the years ended December 31, 2023 and 2022, respectively. There were no commissions for the year ended December 31, 2021. Also includes $1.9 million of excise tax for the year ended December 31, 2023. There were no excise taxes during the years ended December 31, 2022 and 2021.

CONSOLIDATED STATEMENTS OF ST_2

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Common Stock, Dividends, Per Share, Cash Paid	$ 1.39	$ 1.26	$ 1.17

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash Flows from Operating Activities
Net Income	$ 1,283.8	$ 1,407.2	$ 981
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities
Change in Receivables	602.7	590.6	676.1
Deferral of Acquisition Costs	(150.8)	(135.8)	(71.1)
Change in Insurance Reserves and Liabilities	(313.2)	(244.7)	37.7
Change in Income Taxes	(84.3)	(31.3)	335.3
Change in Other Accrued Liabilities	(74.8)	(113.9)	11.3
Non-cash Components of Net Investment Income	(240.3)	(247)	(254.7)
Net Investment (Gain) Loss	36	15.7	(76.7)
Depreciation	108.8	110.5	119.8
Cash Related to Reinsurance Transaction	0	0	(456.8)
Amortization of the Cost of Reinsurance	44.1	50.3	69.8
Other, Net	(9.2)	17.1	15.8
Net Cash Provided by Operating Activities	1,202.8	1,418.7	1,387.5
Cash Flows from Investing Activities
Proceeds from Sales of Fixed Maturity Securities	1,062.7	559.5	442.5
Proceeds from Maturities of Fixed Maturity Securities	1,578.1	1,532.5	2,611.4
Proceeds from Sales and Maturities of Other Investments	360	445.9	403.1
Purchase of Fixed Maturity Securities	(2,991.4)	(2,835.3)	(4,106.3)
Purchase of Other Investments	(361.2)	(482.9)	(606.8)
Net Sales (Purchases) of Short-term Investments	(141)	(22.6)	76.5
Net Decrease in Payables for Collateral on Investments	(98.3)	(50.8)	(50.7)
Net Purchases of Property and Equipment	(134.8)	(102.2)	(110.3)
Net Cash Used by Investing Activities	(725.9)	(955.9)	(1,340.6)
Cash Flows from Financing Activities
Short-term Debt Repayment	(2)	0	0
Issuance of Long-term Debt	0	349.2	588.1
Long-term Debt Repayment	0	(364)	(500)
Cost Related to Early Retirement of Debt	0	3.6	62.8
Issuance of Common Stock	5.2	4	3.4
Repurchase of Common Stock	(250.1)	(200.1)	(50)
Dividends Paid to Stockholders	(277.1)	(254.2)	(239.4)
Proceeds from Policyholder Account Deposits	143.4	119.8	128.1
Payments for Policyholder Account Withdrawals	(87)	(72)	(80.7)
Cash Received Related to Active Life Volatility Cover Agreement	18.6	5.2	40.4
Other, Net	(1.1)	(2.9)	4
Net Cash Used by Financing Activities	(450.1)	(418.6)	(168.9)
Net Increase (Decrease) in Cash and Bank Deposits	26.8	44.2	(122)
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Beginning Balance	119.2	75	197
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Ending Balance	$ 146	$ 119.2	$ 75

Significant Accounting Policies

Significant Accounting Policies	12 Months Ended
	Dec. 31, 2023
Accounting policies and error corrections [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 18). 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 solutions based 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 15 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. In accordance with standard practice, we regularly review the methodology used in the development of all key estimates. As a result of this review, in 2022, we updated our estimate of the unearned premium reserve for certain of our product lines to utilize a gross unearned premium reserve rather than a net unearned premium reserve. The effect of this change in estimate was to decrease 2022 premium income by $13.4 million and decrease commissions by $1.0 million. This resulted in a decrease to net income of $9.8 million and a decrease to both basic and diluted earnings per share by $0.05. 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, net of income tax. Realized investment gains or losses are based upon specific identification of the investments sold. 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 cost 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. When an allowance for credit losses on a fixed maturity security is recognized, we designate non-accrual status for those securities. We reverse all previously accrued interest through interest income and use a cash basis method for recognizing any future payments received. 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 typically 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 investment gains and losses. See Note 3. Policy Loans : Policy loans are presented at the 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 $3,322.5 million and $3,312.5 million of policy loans ceded to reinsurers at December 31, 2023 and 2022, respectively. Other Long-term Investments : Other long-term investments are comprised primarily of private equity partnerships, real estate, perpetual preferred stock, common stock, and tax credit partnerships. 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. Our perpetual preferred stocks are valued at fair value, based on quoted market prices, where available. For preferred stocks not actively traded, fair values are estimated using values obtained from independent pricing services. Our investments in common stock are valued at fair value. Our shares of Federal Home Loan Bank (FHLB) common stock are carried at cost, which approximates fair value. 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. 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 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 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 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 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 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 the same income statement line item as the hedged item during the period of change in fair value. Cash flows related to derivative contracts are included in the consolidated statements of cash flows, coinciding with the timing of the hedged item. Cash inflows are included as a component of proceeds from sales and maturities of other investments. Cash outflows are included as a component of purchases 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. 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 December 31, 2023 and 2022, the allowance for expected credit losses on premium receivables was $29.5 million and $32.5 million, respectively, on gross premium receivables of $612.4 million and $557.6 million, respectively. The allowance decreased $3.0 million and $1.7 million during the years ended December 31, 2023, and 2022, respectively. The decreases were driven primarily by improvements in the age of premiums receivable. 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. Our insurance contracts are grouped by product type and contract issue year into cohorts consistent with the grouping used to estimate the related contract liabilities. DAC is amortized on a constant level basis over the life of the policy. For all products, in-force volume metrics are used as the constant level basis. The lapse and mortality assumptions used to amortize DAC for our traditional long-duration products are consistent with the assumptions used to estimate the liability for future policy benefits. The underlying assumptions used to determine DAC amortization are updated concurrently with any related assumption changes for the liability for future policy benefits and changes in estimates are recognized prospectively over the remaining expected term of the related contracts. Amortization expense is adjusted based on actual versus expected experience through an adjustment to the prospective rate of amortization. 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, principally on group contracts. Internal replacement transactions wherein the modification does not substantially change the policy are accounted for as continuations of the replaced contracts. The original policy continues to be reflected as an in force policy within its original cohort. The policy's expected life then impacts the amortization of remaining unamortized deferred acquisition costs within its cohort. The costs of replacing the policy are accounted for as policy maintenance costs and expensed as incurred. Internal replacement transactions 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. The original policy that was replaced is terminated from its original cohort and this termination is reflected in the amortization rate of remaining unamortized deferred acquisition costs for the cohort. The costs of acquiring the new policy are capitalized and amortized as part of a new cohort. See note 8. 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 $1,422.8 million and $1,328.7 million as of December 31, 2023 and 2022, 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 $63.9 million and $62.9 million at December 31, 2023 and 2022, respectively. The accumulated amortization for value of business acquired was $161.8 million and $150.3 million as of December 31, 2023 and 2022, respectively. The amortization of value of business acquired, which is included in other expenses in the consolidated statements of income, was $5.2 million, $4.9 million, and $5.7 million for the years ended December 31, 2023, 2022, and 2021, respectively. We periodically review the carrying amount of value of business acquired and it is subject to recoverability testing on an annual basis, or more frequently, if appropriate. Future Policy Benefits: Liabilities for future policy benefits represent the cost of claims that we estimate we will eventually pay to our policyholders which includes policy liabilities for claims not yet incurred and for claims that have been incurred or are estimated to have been incurred but not yet reported to us. Liabilities for future policy benefits also include the related expenses for our non interest-sensitive life and accident and health products. The liability for future policy benefits is calculated based on the present value of the estimated future policy benefits less the present value of estimated future net premiums collected. Net premiums represent the portion of the gross premium required to provide for all benefits and expenses, excluding acquisition costs or any costs that are required to be charged to expense as incurred. In calculating the liability for future policy benefits, our long-duration contracts are grouped into cohorts by product type and contract issue year. The calculation of the liability for future policy benefits involves numerous assumptions including assumptions related to discount rate, lapses, mortality, and morbidity. The discount rate assumptions were initially set based on the expected investment yield of the assets supporting the reserves at the transition date of accounting standards update (ASU) 2018-12, which was January 1, 2021, for policies originally issued on or before the transition date. The discount rate assumptions for new cohorts established after the transition date, are initially set based on the policy issuance date or policy renewal date, and are based on an upper-medium grade fixed-income instrument, which is generally equivalent to a single-A interest rate matched to the duration of our insurance liabilities. As cohorts are grouped by product type and issue year, a weighted average discount rate is utilized as policies are issued or renewed throughout the year. We utilize a reference portfolio of fixed-income instruments that have been A-rated by one of the major credit rating agencies. For products with liability cash flows that exceed the duration of observable single-A fixed income instruments, we use the last market observable yield and use extrapolation approaches to determine yield assumptions for durations beyond the last market observable duration. For the discount rate assumptions for products in our Unum International segment, we utilize observable market data in the local debt markets in the UK and Poland. The initial, also referred to as the original, discount rate assumptions established for each cohort are used to determine interest accretion which is reported as a component of policy benefits on the statements of income. After policy issuance or policy renewal, the discount rate assumptions are updated quarterly and used to update the liability at each reporting date to the current discount rate, with the corresponding change reflected as the change in the effect of discount rate assumptions on the liability for future policy benefits, net of reinsurance, on the statement of changes in other comprehensive income (loss). Policyholder lapse and mortality assumptions reflect the probability that an insureds’ coverage is discontinued due to lapsation or death of the insured. For our life insurance products, mortality assumptions also reflect the probability that a benefit payment occurs. Policyholder lapse and mortality 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 claim incidence rate assumption is the rate at which new claims are submitted and the development of this assumption may involve many factors, including the age of the insured, the insured's occupation or industry, the benefit plan design, and certain external factors such as consumer confidence and levels of unemployment. The claim resolution rate assumption is the probability that a claim will close due to recovery or death of the insured and is used to estimate how long benefits will be paid on an open claim. Certain product lines may utilize additional assumptions in calculating the liability for future policy benefits in addition to those listed above such as premium rate increases for long-term care, benefit offsets for long-term disability, and claim costs for voluntary ben
New Accounting Pronouncements and Changes in Accounting Principles	Accounting Updates Adopted in 2023: ASU 2022-02, Financial Instruments - Credit Losses (Topic 326): Troubled Debt Restructurings and Vintage Disclosures The amendments in this update eliminated the troubled debt restructuring recognition and measurement guidance and instead required that an entity evaluate whether the modification represents a new loan or the continuation of an existing loan. The amendments also enhanced the disclosure requirements related to certain modifications of receivables made to borrowers experiencing financial difficulty. In addition, the amendments in this update required that an entity disclose current-period gross write-offs by year of origination for financing receivables and net investment in leases. The amendments in this update were applied prospectively in the period of adoption as of January 1, 2023. The adoption of this update modified our disclosures but did not have an impact on our financial position or results of operations. ASU 2018-12, Financial Services—Insurance (Topic 944): Targeted Improvements to the Accounting for Long-Duration Contracts and related amendments This update significantly amended the accounting and disclosure requirements for long-duration insurance contracts. These changes included 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 is 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 (loss) (OCI). These changes resulted in the elimination of the provision for risk of adverse deviation and premium deficiency (or loss recognition) testing for traditional long-duration insurance contracts. The update also required 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 OCI. This update also simplified 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 are required, which include disaggregated rollforwards of certain liability balances and the disclosure of qualitative and quantitative information about expected cash flows, estimates, and assumptions. We do not have products with market risk benefits. The update was effective for periods beginning January 1, 2023. We adopted this guidance effective January 1, 2023 using the modified retrospective approach with changes applied as of January 1, 2021, also referred to as the transition date. The following tables summarize the impacts of the adoption of ASU 2018-12 on the liability for future policy benefits, deferred acquisition costs, and stockholders' equity as of the transition date as well as impacted historical condensed consolidated financial statement line items for historical comparison. All historically reported information included throughout these financial statements has been adjusted for the impacts of our modified retrospective adoption of ASU 2018-12. Impact of the Adoption of ASU 2018-12 as of the Transition Date: Stockholders' Equity The following table summarizes the changes in stockholders' equity due to the adoption of ASU 2018-12 and the resulting adjusted balances at January 1, 2021: Consolidated Retained Earnings Accumulated Other Comprehensive Income (Loss) Total Stockholders' Equity (in millions of dollars) Balance at December 31, 2020 $ 11,269.6 $ 374.2 $ 10,871.0 Impact of the Adoption of ASU 2018-12 (20.6) (6,684.4) (6,705.0) Balance at January 1, 2021 $ 11,249.0 $ (6,310.2) $ 4,166.0 Liability for Future Policy Benefits The following tables summarize the changes in the liability for future policy benefits due to the adoption of ASU 2018-12 and the resulting adjusted balance at January 1, 2021. The removal of shadow adjustments and effect of change in discount rate assumptions are both recorded as transition adjustments to accumulated other comprehensive income (loss) (AOCI) while the adjustments for loss contracts are recorded as a transition adjustment to retained earnings. Unum US Unum International Colonial Life Closed Block Consolidated (in millions of dollars) Balance at December 31, 2020 1 $ 12,184.6 $ 2,969.8 $ 1,977.2 $ 28,572.8 $ 45,704.4 Removal of Shadow Adjustments 2 (1,569.7) (545.8) (44.5) (4,065.6) (6,225.6) Adjustments for Loss Contracts 3 — — 34.9 — 34.9 Effect of Change in Discount Rate Assumptions 2,251.8 779.4 568.6 12,484.8 16,084.6 Other 4 (5.3) — (7.6) — (12.9) Balance at January 1, 2021 12,861.4 3,203.4 2,528.6 36,992.0 55,585.4 Reinsurance Recoverable 5 357.7 132.5 4.4 10,001.4 10,496.0 Balance, Net of Reinsurance, at January 1, 2021 $ 12,503.7 $ 3,070.9 $ 2,524.2 $ 26,990.6 $ 45,089.4 1 We previously reported policy and contract benefits and reserves for future policy and contract benefits liabilities in our consolidated balance sheet as of December 31, 2020 of $1,855.4 million and $49,653.0 million, respectively, resulting in total policyholder liabilities of $51,508.4 million. These balances were reclassified into new line items, future policy benefits and policyholders' account balances, which would have reported balances of $45,704.4 million and $5,804.0 million as of December 31, 2020, respectively, resulting in total policyholder liabilities of $51,508.4 million under the historical accounting method. These balances were reclassified to more closely align with the new disclosure requirements of ASU 2018-12. 2 Shadow adjustments represent the adjustments related to unrealized investment gains and losses previously included in the reserves balance prior to the adoption of ASU 2018-12. 3 Adjustment for loss contracts represents the adjustment for those cohorts whose net premium ratio exceeded 100 percent as of the transition date. For those cohorts, the net premiums were set equal to the gross premiums and the difference was recorded as a transition adjustment to the liability for future policy benefits. 4 This amount reflects the effect of the reclassification of certain unearned premium. This amount was reclassified to more closely align with the presentation of liabilities under ASU 2018-12 and had no impact to stockholders' equity. 5 These amounts represent the portion of reinsurance recoverable related to the liability for future policy benefits. These amounts include the adjustments for the removal of shadow adjustments and for the effect of change in discount rate assumptions for the liability for future policy benefits ceded to third party reinsurers. Unum US Segment Group Disability Group Life and AD&D Individual Disability Voluntary Disability Dental and Vision Total (in millions of dollars) Balance at December 31, 2020 $ 7,409.0 $ 1,123.9 $ 2,485.3 $ 1,154.9 $ 11.5 $ 12,184.6 Removal of Shadow Adjustments (1,025.2) (88.5) (446.1) (9.9) — (1,569.7) Effect of Change in Discount Rate Assumptions 911.9 91.9 728.5 519.5 — 2,251.8 Other — — — (5.3) — (5.3) Balance at January 1, 2021 7,295.7 1,127.3 2,767.7 1,659.2 11.5 12,861.4 Reinsurance Recoverable 58.3 3.0 260.6 35.7 0.1 357.7 Balance, Net of Reinsurance, at January 1, 2021 $ 7,237.4 $ 1,124.3 $ 2,507.1 $ 1,623.5 $ 11.4 $ 12,503.7 Closed Block Segment Long-term Care All Other Total (in millions of dollars) Balance at December 31, 2020 $ 16,283.4 $ 12,289.4 $ 28,572.8 Removal of Shadow Adjustments (3,465.4) (600.2) (4,065.6) Effect of Change in Discount Rate Assumptions 9,922.9 2,561.9 12,484.8 Balance at January 1, 2021 22,740.9 14,251.1 36,992.0 Reinsurance Recoverable 44.4 9,957.0 10,001.4 Balance, Net of Reinsurance, at January 1, 2021 $ 22,696.5 $ 4,294.1 $ 26,990.6 Deferred Acquisition Costs (DAC) The following tables summarize the changes in DAC due to the adoption of ASU 2018-12 and the resulting adjusted balance at January 1, 2021. The removal of shadow adjustments is recorded as a transition adjustment to AOCI. Consolidated Unum US 1 Unum International Colonial Life Total (in millions of dollars) Balance at December 31, 2020 $ 1,168.7 $ 32.0 $ 1,071.9 $ 2,272.6 Removal of Shadow Adjustments 12.3 — 72.8 85.1 Balance at January 1, 2021 $ 1,181.0 $ 32.0 $ 1,144.7 $ 2,357.7 1 The $12.3 million removal of shadow adjustments is related to the Unum US voluntary benefits product line. Impact of the Adoption of ASU 2018-12 on Historical Financial Statements: The following tables present the effect of the adoption of ASU 2018-12 on our historical consolidated financial statements: December 31, 2022 Historical Accounting Method As Adjusted Effect of Change (in millions of dollars) Consolidated Balance Sheets Assets Reinsurance Recoverable $ 10,218.6 $ 9,608.0 $ (610.6) Deferred Acquisition Costs 2,252.3 2,560.0 307.7 Deferred Income Tax 449.8 586.0 136.2 Other Assets 1 1,786.3 1,666.6 (119.7) Total Assets 61,434.9 61,148.5 (286.4) Liabilities Policy and Contract Benefits 2 $ 1,839.8 $ — $ (1,839.8) Reserves for Future Policy and Contract Benefits 2 42,330.2 — (42,330.2) Future Policy Benefits 2 — 38,577.1 38,577.1 Policyholders' Account Balances 2 — 5,740.2 5,740.2 Unearned Premiums 352.7 365.5 12.8 Deferred Income Tax 9.2 25.2 16.0 Total Liabilities 52,237.4 52,413.5 176.1 Stockholders' Equity Accumulated Other Comprehensive Loss $ (2,756.6) $ (3,448.3) $ (691.7) Retained Earnings 12,912.1 13,141.3 229.2 Total Stockholders' Equity 9,197.5 8,735.0 (462.5) 1 The change in other assets is driven by the cost of reinsurance associated with the second phase of our Closed Block individual disability reinsurance transaction which was completed in the first quarter of 2021. In accordance with the provisions of the ASU related to non-contemporaneous reinsurance, we were then required to establish the ceded reserves using an upper-medium grade fixed-income instrument as of the reinsurance transaction date in March 2021 which resulted in higher ceded reserves compared to that which was reported historically. 2 We previously reported policy and contract benefits and reserves for future policy and contract benefits liabilities in our consolidated balance sheet as of December 31, 2022 of $1,839.8 million and $42,330.2 million, respectively, resulting in total policyholder liabilities of $44,170.0 million. These balances were reclassified into new line items, future policy benefits and policyholders' account balances, which would have reported balances of $38,443.2 million and $5,726.8 million, respectively, as of December 31, 2022, resulting in total policyholder liabilities of $44,170.0 million under the historical accounting method. Twelve Months Ended December 31, 2022 Historical Accounting Method As Adjusted Effect of Change (in millions of dollars, except share data and where noted) Consolidated Statements of Income Premium Income $ 9,623.4 $ 9,616.5 $ (6.9) Policy Benefits 1 6,936.7 7,542.1 605.4 Policy Benefits - Remeasurement Gain — (547.5) (547.5) Amortization of Deferred Acquisition Costs 591.0 421.1 (169.9) Other Expenses 1,020.2 1,006.7 (13.5) Income Tax - Deferred (156.3) (130.7) 25.6 Net Income 1,314.2 1,407.2 93.0 Net Income Per Common Share Basic $ 6.55 $ 7.01 $ 0.46 Assuming Dilution $ 6.50 $ 6.96 $ 0.46 Consolidated Statements of Comprehensive Income (Loss) Net Income $ 1,314.2 $ 1,407.2 $ 93.0 Change in Adjustment to Deferred Acquisition Costs and Reserves for Future Policy and Contract Benefits, Net of Reinsurance 4,056.9 — (4,056.9) Change in the Effect of Discount Rate Assumptions on the Liability for Future Policy Benefits, Net of Reinsurance — 8,884.6 8,884.6 Change in Foreign Currency Translation Adjustment (115.2) (116.0) (0.8) Comprehensive Income (Loss) (1,796.5) 3,123.5 4,920.0 Consolidated Statements of Stockholders' Equity Accumulated Other Comprehensive Income (Loss) Balance at Beginning of Year $ 354.1 $ (5,164.6) $ (5,518.7) Other Comprehensive Income (Loss) (3,110.7) 1,716.3 4,827.0 Retained Earnings Balance at Beginning of Year 11,853.2 11,989.4 136.2 Net Income 1,314.2 1,407.2 93.0 Consolidated Statements of Cash Flows Cash Flows from Operating Activities Net Income $ 1,314.2 $ 1,407.2 $ 93.0 Change in Receivables 566.0 590.6 24.6 Change in Deferred Acquisition Costs 34.1 (135.8) (169.9) Change in Insurance Liabilities (282.0) (244.7) 37.3 Change in Income Taxes (58.8) (31.3) 27.5 Amortization of the Cost of Reinsurance 63.8 50.3 (13.5) Other, Net 16.1 17.1 1.0 1 Previously disclosed as Benefits and Change in Reserves for Future Benefits Twelve Months Ended December 31, 2021 Historical Accounting Method As Adjusted Effect of Change (in millions of dollars, except share data and where noted) Consolidated Statements of Income Premium Income $ 9,481.0 $ 9,475.0 $ (6.0) Policy Benefits 1 7,598.6 8,113.3 514.7 Policy Benefits - Remeasurement Gain — (559.9) (559.9) Deferral of Acquisition Costs (508.1) (523.2) (15.1) Amortization of Deferred Acquisition Costs 586.1 452.1 (134.0) Other Expenses 1,008.6 999.3 (9.3) Income Tax - Deferred 26.0 66.8 40.8 Net Income 824.2 981.0 156.8 Net Income Per Common Share Basic $ 4.04 $ 4.80 $ 0.76 Assuming Dilution $ 4.02 $ 4.79 $ 0.77 Consolidated Statements of Comprehensive Income (Loss) Net Income $ 824.2 $ 981.0 $ 156.8 Change in Adjustment to Deferred Acquisition Costs and Reserves for Future Policy and Contract Benefits, Net of Reinsurance 1,195.9 — (1,195.9) Change in the Effect of Discount Rate Assumptions on the Liability for Future Policy Benefits, Net of Reinsurance — 2,361.8 2,361.8 Change in Foreign Currency Translation Adjustment (12.6) (12.8) (0.2) Comprehensive Income (Loss) 804.1 2,126.6 1,322.5 Consolidated Statements of Stockholders' Equity Accumulated Other Comprehensive Income (Loss) Balance at Beginning of Year $ 374.2 $ (6,310.2) $ (6,684.4) Other Comprehensive Income (Loss) (20.1) 1,145.6 1,165.7 Retained Earnings Balance at Beginning of Year 11,269.6 11,249.0 (20.6) Net Income 824.2 981.0 156.8 Consolidated Statements of Cash Flows Cash Flows from Operating Activities Net Income $ 824.2 $ 981.0 $ 156.8 Change in Receivables 678.0 676.1 (1.9) Change in Deferred Acquisition Costs 78.0 (71.1) (149.1) Change in Insurance Liabilities 74.2 37.7 (36.5) Change in Income Taxes 295.3 335.3 40.0 Amortization of the Cost of Reinsurance 79.1 69.8 (9.3) 1 Previously disclosed as Benefits and Change in Reserves for Future Benefits The decrease in AOCI in our recast of 2022 as shown in the preceding chart is driven primarily by the difference between the discount rate applied under the historical accounting method, which was based on an expected investment yield from our current investment strategy, and the single-A discount rate that is required as a part of the adoption of ASU 2018-12. The most significant impact is related to our longest duration products. Our investment strategy reflects the illiquid nature of the majority of our liability cash flows and, as a result, the yields in our investment portfolios supporting the cash outflows required for these products are generally higher than a single-A yield. In addition, the discount rates applied under the historical accounting method to the reserves for our longest duration products, such as long-term care, included an assumption for long-term yields rising to more historical levels. The net favorable impact of the adoption of ASU 2018-12 to net income for the years ended December 31, 2021 and December 31, 2022 shown in the preceding charts is due primarily to the following changes: • Updating the lifetime cohort net premium ratios, or lifetime loss ratio, for actual experience each reporting period will generally cause earnings patterns to be more consistent from period to period, with variances in experience reflected in earnings over the cohort lifetime. This resulted in an unfavorable impact to income for 2021 and 2022. • Alignment of amortization of deferred acquisition costs to a constant level basis and modification of amortization periods to reflect the expected term of the related contracts could result in either higher or lower income for the affected product lines. This resulted in a net favorable impact to income for 2021 and 2022. • Accelerated recognition of the provision for adverse deviation or other differences from current best estimate values for policies issued prior to the transition date and due to not establishing the provision for policies issued on or after the transition date will generally result in higher income most notably in the initial years after the transition date. This resulted in a favorable impact to income for 2021 and 2022. • Establishing reserves for claims incurred on or after the transition date at interest rates prescribed by the update could result in either higher or lower income for the affected product lines depending on the policy issue date and the interest rate environment at that time. This resulted in an unfavorable impact to income for 2021 and a favorable impact to income for 2022. • Updating cash flow assumptions could result in either higher or lower income. This resulted in a favorable impact to income for 2021 and 2022. • Accounting for non-contemporaneous reinsurance related to the second phase of our Closed Block individual disability reinsurance transaction which was completed in the first quarter of 2021. This resulted in an increase in policy benefits resulting from the realization of previously unrealized investment gains and losses previously recorded in AOCI that was removed as of the transition date which had a favorable impact on income for 2021. As a result of the execution of the second phase of the reinsurance transaction occurring after January 1, 2021, the transition date of ASU 2018-12, in accordance with the provisions of the ASU related to non-contemporaneous reinsurance, we were required to establish the ceded reserves using an upper-medium grade fixed-income instrument as of the reinsurance transaction date in March 2021 which resulted in higher ceded reserves compared to that which was reported historically. However, the direct reserves for the block reinsured in the second phase were calculated using the original discount rate utilized as of the transition date. Both the direct and ceded reserves are then remeasured at each reporting period using a current discount rate reflective of an upper-medium grade fixed-income instrument, with the changes recognized in OCI. While the total equity impact is neutral, the different original discount rates utilized for direct and ceded reserves result in disproportionate earnings impacts. The differential in the original discount rate applied to the direct and ceded cohorts of business resulted in an unfavorable impact to income for 2021 and 2022, partially offset by a decrease in the amortization of the cost of reinsurance as a result of a lower cost of reinsurance. Accounting Updates Adopted in 2022: ASU 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity's Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity's Own Equity The amendments in this update simplified the accounting for convertible instruments by removing certain separation models in the guidance related to convertible instruments and expanded related disclosure requirements. The amendments also revised the requirements for a contract or embedded derivative that is potentially settled in an entity's own stock to be classified as equity and also amended certain guidance related to the computations of earnings per share for convertible instruments and contracts in an entity's own stock. This guidance was applied in the period of adoption as of January, 1 2022. The adoption of this update did not have an effect on our financial position or results of operations, and did not expand our disclosures. Accounting Updates Adopted in 2021: ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes The amendments in this update simplified the accounting for income taxes by removing certain exceptions in the guidance related to losses in continuing operations when there is income in other items, foreign subsidiaries becoming equity method investments and vice versa, and year-to-date interim period losses exceeding anticipated loss for the year. The amendments also simplified the accounting for income taxes related to franchise taxes partially based on income, step up in the tax basis of goodwill, allocation of tax expense to entities not subject to tax, enacted changes in tax law or rates in interim periods, and employee stock ownership programs and investments in qualified affordable housing projects accounted for using the equity method. This guidance was applied in the period of adoption as of January, 1 2021. The adoption of this update did not have a material effect on our financial position or results of operations. Accounting Updates Outstanding: ASU 2020-04 , Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting and related amendments The amendments in this update provide optional guidance, for a limited period of time, to ease the potential burden in accounting for and recognizing the effects of reference rate reform on financial reporting. The guidance allows for various practical expedients and exceptions when applying GAAP to contracts, hedging relationships, and other transactions affected either by discontinued rates as a direct result of reference rate reform or a market-wide change in interest rates used for discounting, margining or contract price alignment, if certain criteria are met. Specifically, the guidance provides certain practical expedients for contract modifications, fair value hedges, and cash flow hedges, and also provides certain exceptions related to changes in the critical terms of a hedging relationship. The guidance also allows for a one-time election to sell or transfer debt securities that were both classified as held-to-maturity prior to January 1, 2020 and reference a rate affected by the reform. The adoption of this update 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, 2024, at which point the guidance will sunset. We do not anticipate needing to adopt this guidance, but we will continue to monitor our contracts and hedging relationships throughout the adoption period. ASU 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures The amendments in this update enhance disclosures of significant expenses for reportable segments. Specifically, the update adds a requirement to disclose significant expenses that are regularly provided to the Chief Operating Decision Maker (CODM) and are included in each reported measure of segment profit or loss. This update will require the disclosure of the title and position of the CODM as well as an explanation of how they use the reported measure(s) to assess segment performance and make decisions about allocating resources. The update also requires the disclosure of the amount and composition of other segment items, which is the difference between reported segment revenues less the significant segment expenses. The amendments in this update allow for the disclosure of more than one measure of segment profit or loss, provided that at least one of the reported measures includes the segment profit or loss measure that is most consistent with GAAP measurement principles. We will adopt this update effective for the annual period beginning January 1, 2024 and the interim period beginning January 1, 2025 using a retrospective approach. The adoption of this update will expand our disclosures but will not have an impact on our financial position or results of operations. ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures The amendments in this update require greater disaggregation of income tax disclosures related to the income tax rate reconciliation and income taxes paid. Specifically, the guidance requires additional information that meet a quantitative threshold in specified categories with respect to the reconciliation of the effective tax rate to the statutory tax rate for federal, state, and foreign income taxes. The specified categories are the following: state and local income taxes, foreign tax effects, effect of cross-border tax laws, enactment of new tax laws, nontaxable or nondeductible items, tax credits, changes in valuation allowances, and changes in unrecognized tax benefits. The quantitative threshold for each category is five percent of the amount computed by multiplying income (or loss) from continuing operations before income taxes by the statutory federal income tax rate. In addition, the amendments require additional information pertaining to income taxes paid, net of refunds, to be disaggregated by federal, state and foreign jurisdictions, and further disaggregated for specific jurisdictions to the extent the related amounts exceed a quantitative threshold of five percent of total income taxes paid. The amendments also require disclosures of income (or loss) before income tax expense (or benefit) as domestic or foreign for each annual reporting period. The amendments eliminate the historic requirement to disclose information regarding unrecognized tax benefits having a reasonable possibility of significantly increasing or decreasing in the twelve months following the reporting date, as well as the requirement to disclose the cumulative temporary differences when a deferred tax liability is not recognized due to certain exceptions under ASC 740.

Fair Values of Financial Instru

Fair Values of Financial Instruments	12 Months Ended
	Dec. 31, 2023
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' NAV per share or its equivalent 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 2023, 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 2022. 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 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 Level 2 Level 3 Instrument Observable Inputs Unobservable Inputs 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 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 Level 2 Level 3 Instrument Observable Inputs Unobservable Inputs 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 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 selected 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, 2023, approximately 11.6 percent of our fixed maturity securities were valued using active trades from TRACE pricing or 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 88.4 percent of our fixed maturity securities were valued based on non-binding quotes or other observable and unobservable inputs, as discussed below: • 72.9 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. • 14.7 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. • 0.8 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. Credit risk related to the counterparty and the Company is considered in determining the fair values of these derivatives. However, since we have collateralization agreements in place with each counterparty which limits our exposure, any credit risk is immaterial. Therefore, we determined that no adjustments for credit risk were required as of December 31, 2023 or 2022. 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, 2023 Investment Category Fair Value Redemption Term / Redemption Notice Unfunded Commitments (in millions of dollars) (in millions of dollars) Private Credit (a) $ 239.1 Not redeemable $ 128.2 44.5 Quarterly / 90 days notice 8.6 Total Private Credit 283.6 136.8 Private Equity (b) 543.9 Not redeemable 410.6 28.0 Initial 5.5 year lock on each new investment / Quarterly after 5.5 year lock with 90 days notice 16.6 Total Private Equity 571.9 427.2 Real Assets (c) 437.5 Not redeemable 239.1 33.2 Quarterly / 90 days notice — Total Real Assets 470.7 239.1 Total Partnerships $ 1,326.2 $ 803.1 December 31, 2022 Investment Category Fair Value Redemption Term / Redemption Notice Unfunded Commitments (in millions of dollars) (in millions of dollars) Private Credit (a) $ 239.3 Not redeemable $ 90.9 35.7 Initial 2 year lock on each new investment / Quarterly after 2 year lock with 90 days notice 13.4 Total Private Credit 275.0 104.3 Private Equity (b) 453.6 Not redeemable 377.2 31.7 Initial 5.5 year lock on each new investment / Quarterly after 5.5 year lock with 90 days notice 39.1 Total Private Equity 485.3 416.3 Real Assets (c) 373.9 Not redeemable 256.3 60.1 Quarterly / 90 days notice — Total Real Assets 434.0 256.3 Total Partnerships $ 1,194.3 $ 776.9 (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, 2023, the estimated remaining life of the investments that do not allow for redemptions is approximately 74 percent in the next 3 years, 21 percent during the period from 3 to 5 years, 3 percent during the period from 5 to 10 years, and 2 percent during the period from 10 to 15 years. (b) Private Equity - The limited partnerships described in this category employ various strategies generally investing in controlling or minority control equity positions directly in companies and/or assets across various industries (including manufacturing, healthcare, energy, business services, technology, materials, and retail), primarily in private markets within North America and, to a lesser extent, outside of North America. As of December 31, 2023, the estimated remaining life of the investments that do not allow for redemptions is approximately 34 percent in the next 3 years, 31 percent during the period from 3 to 5 years, 26 percent during the period from 5 to 10 years, and 9 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, 2023, the estimated remaining life of the investments that do not allow for redemptions is approximately 22 percent in the next 3 years, 35 percent during the period from 3 to 5 years, 42 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, 2023 Level 1 Level 2 Level 3 NAV Total (in millions of dollars) Assets Fixed Maturity Securities United States Government and Government Agencies and Authorities $ — $ 624.8 $ — $ — $ 624.8 States, Municipalities, and Political Subdivisions — 3,678.4 — — 3,678.4 Foreign Governments — 890.7 — — 890.7 Public Utilities 301.3 5,020.3 — — 5,321.6 Mortgage/Asset-Backed Securities — 611.2 32.9 — 644.1 All Other Corporate Bonds 3,985.2 21,562.1 123.4 — 25,670.7 Redeemable Preferred Stocks — 3.6 — — 3.6 Total Fixed Maturity Securities 4,286.5 32,391.1 156.3 — 36,833.9 Other Long-term Investments Derivatives Forwards — 47.5 — — 47.5 Foreign Exchange Contracts — 52.4 — — 52.4 Total Derivatives — 99.9 — — 99.9 Perpetual Preferred and Equity Securities — 10.3 21.6 — 31.9 Private Equity Partnerships — — — 1,326.2 1,326.2 Total Other Long-term Investments — 110.2 21.6 1,326.2 1,458.0 Total Financial Instrument Assets Carried at Fair Value $ 4,286.5 $ 32,501.3 $ 177.9 $ 1,326.2 $ 38,291.9 Liabilities Other Liabilities Derivatives Forwards $ — $ 78.0 $ — $ — $ 78.0 Foreign Exchange Contracts — 38.2 — — 38.2 Embedded Derivative in Modified Coinsurance Arrangement — — 1.5 — 1.5 Total Derivatives — 116.2 1.5 — 117.7 Total Financial Instrument Liabilities Carried at Fair Value $ — $ 116.2 $ 1.5 $ — $ 117.7 December 31, 2022 Level 1 Level 2 Level 3 NAV Total (in millions of dollars) Assets Fixed Maturity Securities United States Government and Government Agencies and Authorities $ 81.7 $ 416.5 $ — $ — $ 498.2 States, Municipalities, and Political Subdivisions 8.7 3,448.3 0.2 — 3,457.2 Foreign Governments — 827.1 — — 827.1 Public Utilities 160.1 4,796.8 — — 4,956.9 Mortgage/Asset-Backed Securities — 551.3 22.0 — 573.3 All Other Corporate Bonds 4,268.6 20,097.3 158.7 — 24,524.6 Redeemable Preferred Stocks — 3.5 — — 3.5 Total Fixed Maturity Securities 4,519.1 30,140.8 180.9 — 34,840.8 Other Long-term Investments Derivatives Forwards — 5.6 — — 5.6 Foreign Exchange Contracts — 83.5 — — 83.5 Total Derivatives — 89.1 — — 89.1 Perpetual Preferred and Equity Securities — 9.6 16.2 — 25.8 Private Equity Partnerships — — — 1,194.3 1,194.3 Total Other Long-term Investments — 98.7 16.2 1,194.3 1,309.2 Total Financial Instrument Assets Carried at Fair Value $ 4,519.1 $ 30,239.5 $ 197.1 $ 1,194.3 $ 36,150.0 Liabilities Other Liabilities Derivatives Forwards $ — $ 48.5 $ — $ — $ 48.5 Foreign Exchange Contracts — 25.5 — — 25.5 Embedded Derivative in Modified Coinsurance Arrangement — — 13.9 — 13.9 Total Derivatives — 74.0 13.9 — 87.9 Total Financial Instrument Liabilities Carried at Fair Value $ — $ 74.0 $ 13.9 $ — $ 87.9 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, 2023 Fair Value Beginning Total Realized and Purchases Sales/Maturities Level 3 Transfers Fair Value End of Change in Unrealized Earnings OCI Into Out of OCI Earnings (in millions of dollars) Fixed Maturity Securities States, Municipalities, and Political Subdivisions $ 0.2 $ — $ — $ — $ — $ — $ (0.2) $ — $ — $ — Public Utilities — 0.1 (0.1) — (50.5) 50.5 — — — — Mortgage/Asset-Backed Securities 22.0 — (0.2) 20.0 (0.5) 0.4 (8.8) 32.9 (0.2) — All Other Corporate Bonds 158.7 (5.0) (15.8) 1.5 (334.1) 385.0 (66.9) 123.4 (15.8) — Total Fixed Maturity Securities 180.9 (4.9) (16.1) 21.5 (385.1) 435.9 (75.9) 156.3 (16.0) — Perpetual Preferred and Equity Securities 16.2 0.6 — 4.8 — — — 21.6 — 0.6 Embedded Derivative in Modified Coinsurance Arrangement (13.9) 12.4 — — — — — (1.5) — 12.4 Year Ended December 31, 2022 Fair Value Beginning Total Realized and Purchases Sales/Maturities Level 3 Transfers Fair Value End of Change in Unrealized Earnings OCI Into Out of OCI Earnings (in millions of dollars) Fixed Maturity Securities States, Municipalities, and Political Subdivisions $ 13.4 $ — $ (0.1) $ — $ — $ 0.3 $ (13.4) $ 0.2 $ (0.1) $ — Foreign Governments 20.8 — (0.8) — (20.0) — — — (0.8) — Public Utilities 44.5 — (2.8) — (12.8) 15.6 (44.5) — (2.8) — Mortgage/Asset-Backed Securities 187.2 — (0.3) 20.7 (10.6) — (175.0) 22.0 (0.3) — All Other Corporate Bonds 861.5 — (32.0) 25.3 (102.3) 161.9 (755.7) 158.7 (32.0) — Total Fixed Maturity Securities 1,127.4 — (36.0) 46.0 (145.7) 177.8 (988.6) 180.9 (36.0) — Perpetual Preferred and Equity Securities 5.8 3.0 — 7.1 — 0.3 — 16.2 — 3.0 Embedded Derivative in Modified Coinsurance Arrangement (30.1) 16.2 — — — — — (13.9) — 16.2 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, 2023 Fair Value Valuation Method Unobservable Input Range/Weighted Average (in millions of dollars) Fixed Maturity Securities All Other Corporate Bonds - Private $ 15.9 Market Approach Volatility of Credit Market Convention (a) (b) 5.00% - 5.00% / 5.00% Priced at Par Value Perpetual Preferred and Equity Securities 21.6 Market Approach Market Convention (b) Priced at Cost, Owner's Equity, or Most Recent Round Embedded Derivative in Modified Coinsurance Arrangement (1.5) Discounted Cash Flows Projected Liability Cash Flows Weighted Spread of Swap Curve (c) Actuarial Assumptions 0.2% December 31, 2022 Fair Value Valuation Method Unobservable Input Range/Weighted Average (in millions of dollars) Fixed Maturity Securities All Other Corporate Bonds - Private $ 15.3 Market Approach Volatility of Credit Market Convention (a) (b) 5.41% - 5.41% / 5.41% Priced at Par Value Perpetual Preferred and Equity Securities 16.2 Market Approach Market Convention (b) Priced at Cost, Owner's Equity, or Most Recent Round Embedded Derivative in Modified Coinsurance Arrangement (13.9) Discounted Cash Flows Projected Liability Cash Flows Weighted Spread of Swap Curve (c) Actuarial Assumptions 0.6% (a) Represents basis point adjustments for credit-specific factors (b) Represents a decision to price based on par value, cost, owner's equity, or the price of the most recent capital funding round when limited data is available (c) Represents various actuarial assumptions required to derive the liability cash flows. Fair value of embedded derivative is most often driven by the change in the weighted average credit spread to the swap curve for the assets backing the hypothetical loan Other than market convention, the impact of isolated decreases in unobservable inputs will result in a higher estimated fair value, whereas isolated increases in unobservable inputs will result in a lower estimated fair value. The unobservable input for market convention is not sensitive to input movements. The projected liability cash flows used in the fair value measurement of our Level 3 embedded derivative are based on expected claim payments. If claim payments increase, the projected liability cash flows will increase, resulting in a decrease in the fair value of the embedded derivative. Decreases in projected liability cash flows will result in an increase in the fair value of the embedded derivative. Fair Value Measurements for Financial Instruments Not Carried at Fair Value The methods and assumptions used to estimate fair values of financial instruments not carried at fair value are discussed as follows: Mortgage Loans: Fair value of newly originated, seasoned performing, or sub-performing but likely to continue cash flowing loans are calculated using a discounted cash flow analysis. Loans’ cash flows are modeled and appropriately discounted by a rate based on current yields and credit spreads. For sub and non-performing loans where there is some probability the loan will not continue to pay, a price based approach would be used to estimate the loan’s value in the open market utilizing current transaction information from similar loans. Policy Loans: Fair values for policy loans, net of reinsurance ceded, are estimated using discounted cash flow analyses and interest rates currently being offered to policyholders with similar policies. Carrying amounts for ceded policy loans, which equal $3,322.5 million and $3,312.5 million as of December 31, 2023 and 2022, 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 Federal Home Loan Bank (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. 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, 2023 Estimated Fair Value Level 1 Level 2 Level 3 Total Carrying Value (in millions of dollars) Assets Mortgage Loans $ — $ 2,070.7 $ — $ 2,070.7 $ 2,318.2 Policy Loans — — 3,696.3 3,696.3 3,620.2 Other Long-term Investments Miscellaneous Long-term Investments — 15.7 0.3 16.0 16.0 Total Financial Instrument Assets Not Carried at Fair Value $ — $ 2,086.4 $ 3,696.6 $ 5,783.0 $ 5,954.4 Liabilities Long-term Debt $ 2,629.1 $ 598.8 $ — $ 3,227.9 $ 3,430.4 Other Liabilities Unfunded Commitments — 0.2 — 0.2 0.2 Payable for Collateral on FHLB Funding Agreements — 64.5 — 64.5 64.5 Total Financial Instrument Liabilities Not Carried at Fair Value $ 2,629.1 $ 663.5 $ — $ 3,292.6 $ 3,495.1 December 31, 2022 Estimated Fair Value Level 1 Level 2 Level 3 Total Carrying Value (in millions of dollars) Assets Mortgage Loans $ — $ 2,159.5 $ — $ 2,159.5 $ 2,435.4 Policy Loans — — 3,677.0 3,677.0 3,601.2 Other Long-term Investments Miscellaneous Long-term Investments — 17.1 1.3 18.4 18.4 Total Financial In

Investments

Investments	12 Months Ended
	Dec. 31, 2023
Investments, Debt and Equity Securities [Abstract]
Investments	65% <= 75% 707.0 30.5 937.2 38.5 > 75% <= 85% 136.5 5.9 75.0 3.1 > 85% 64.8 2.8 33.6 1.4 Total $ 2,318.2 100.0 % $ 2,435.4 100.0 % 1 Loan-to-Value Ratio utilizes the most recent internal valuation of the property There were no gross write-offs for the periods ending December 31, 2023 or 2022. The following tables present the amortized cost of our mortgage loans by year of origination and internal quality indicators for the years ended December 31, 2023 and 2022: Year Ended December 31, 2023 Prior to 2019 2019 2020 2021 2022 2023 Total (in millions of dollars) Internal Mortgage Rating AA $ 74.3 $ 11.0 $ — $ — $ — $ — $ 85.3 A 589.0 100.3 94.1 100.1 23.2 38.0 944.7 BBB 618.4 224.8 71.4 248.0 64.4 29.2 1,256.2 BB 42.2 — — — — — 42.2 Total Amortized Cost 1,323.9 336.1 165.5 348.1 87.6 67.2 2,328.4 Allowance for credit losses (6.3) (1.3) (0.6) (1.0) (0.6) (0.4) (10.2) Carrying Amount $ 1,317.6 $ 334.8 $ 164.9 $ 347.1 $ 87.0 $ 66.8 $ 2,318.2 Loan-to-Value Ratio 1 <=65% $ 908.3 $ 197.7 $ 116.4 $ 145.2 $ 16.2 $ 30.0 $ 1,413.8 >65<=75% 252.1 138.4 40.8 171.0 71.4 37.2 710.9 >75%<=85% 97.3 — 8.3 31.9 — — 137.5 >85% 66.2 — — — — — 66.2 Total Amortized Cost 1,323.9 336.1 165.5 348.1 87.6 67.2 2,328.4 Allowance for credit losses (6.3) (1.3) (0.6) (1.0) (0.6) (0.4) (10.2) Carrying Amount $ 1,317.6 $ 334.8 $ 164.9 $ 347.1 $ 87.0 $ 66.8 $ 2,318.2 1 Loan-to-Value Ratio utilizes the most recent internal valuation of the property Year Ended December 31, 2022 Prior to 2018 2018 2019 2020 2021 2022 Total (in millions of dollars) Internal Mortgage Rating AA $ 53.8 $ 27.5 $ 11.1 $ — $ — $ — $ 92.4 A 485.0 123.3 96.8 35.9 80.6 24.0 845.6 BBB 534.0 219.8 236.9 134.0 275.8 64.6 1,465.1 BB 35.7 5.9 — — — — 41.6 Total Amortized Cost 1,108.5 376.5 344.8 169.9 356.4 88.6 2,444.7 Allowance for credit losses (4.3) (1.8) (1.3) (0.6) (0.8) (0.5) (9.3) Carrying Amount $ 1,104.2 $ 374.7 $ 343.5 $ 169.3 $ 355.6 $ 88.1 $ 2,435.4 Loan-to-Value Ratio 1 <=65% $ 782.6 $ 189.0 $ 193.9 $ 81.3 $ 128.9 $ 16.9 $ 1,392.6 >65<=75% 230.2 181.6 150.9 80.1 227.5 71.7 942.0 >75%<=85% 67.5 — — 8.5 — — 76.0 >85% 28.2 5.9 — — — — 34.1 Total Amortized Cost 1,108.5 376.5 344.8 169.9 356.4 88.6 2,444.7 Allowance for credit losses (4.3) (1.8) (1.3) (0.6) (0.8) (0.5) (9.3) Carrying Amount $ 1,104.2 $ 374.7 $ 343.5 $ 169.3 $ 355.6 $ 88.1 $ 2,435.4 1 Loan-to-Value Ratio utilizes the most recent internal valuation of the property The following tables present a roll forward of allowance for expected credit losses by loan-to-value ratio for the years ended December 31, 2023 and 2022: Year Ended December 31, 2023 Beginning of Period Current Period Provisions Write-Offs Recoveries End of Period (in millions of dollars) Loan-to-Value Ratio 1 <=65% $ 3.0 $ 0.8 $ — $ — $ 3.8 >65<=75% 4.7 (0.9) — — 3.8 >75%<=85% 1.1 0.1 — — 1.2 >85% 0.5 0.9 — — 1.4 Total $ 9.3 $ 0.9 $ — $ — $ 10.2 Year Ended December 31, 2022 Beginning of Period Current Period Provisions Write-Offs Recoveries End of Period (in millions of dollars) Loan-to-Value Ratio 1 <=65% $ 2.6 $ 0.4 $ — $ — $ 3.0 >65<=75% 4.7 — — — 4.7 >75%<=85% 0.7 0.4 — — 1.1 >85% 0.3 0.2 — — 0.5 Total $ 8.3 $ 1.0 $ — $ — $ 9.3 1 Loan-to-Value Ratio utilizes the most recent internal valuation of the property For the years ended December 31, 2023 and 2022 our estimate for expected credit losses was generally consistent between periods. During the year ended December 31, 2023 we granted an other-than-insignificant payment delay for a commercial mortgage loan with an amortized cost of $14.2 million, which deferred the principal payment for 18 months. This modification represents less than one percent of the commercial mortgage loan portfolio balance. There were no troubled debt restructurings during 2022 or 2021. We held no mortgage loans that were greater than 90 days past due regarding principal and/or interest payments for the years ended December 31, 2023, 2022, or 2021. We had no loan foreclosures for the years ended December 31, 2023, 2022, or 2021. Other than our allowance for expected credit losses, we had no specifically identified impaired mortgage loans for the years ended December 31, 2023, 2022, and 2021, nor did we recognize any interest income on mortgage loans subsequent to impairment. For the year ended December 31, 2023 we had no commitments to fund certain commercial mortgage loans. For the year ended December 31, 2022 we had $5.0 million in commitments 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. For the year ended December 31, 2023, we had no expected credit losses related to unfunded commitments on our consolidated balance sheets. For the year ended December 31, 2022, we had a nominal amount of expected credit losses related to unfunded commitments on our consolidated balance sheets. Investment Real Estate Our investment real estate balance was $64.4 million and $71.6 million at December 31, 2023 and 2022, respectively, and the associated accumulated depreciation was $127.2 million and $122.1 million at December 31, 2023 and 2022, respectively. For the year ended December 31, 2023, we recognized a $3.0 million impairment related to certain of our real estate held for investment. We did not recognize any impairments related to our real estate held for investment during 2022 or 2021. Our held for sale real estate balance was $40.9 million at both December 31, 2023 and December 31, 2022 and the associated accumulated depreciation was $54.2 million at both December 31, 2023 and December 31, 2022 . During the first quarter of 2022, we reclassified one property previously held for the production of income to property held for sale. The carrying value of the property was $40.1 million at both December 31, 2023 and December 31, 2022 , and is primarily recorded within our Corporate segment. The estimated fair value less costs to sell is above the carrying value of the property and we expect to close the sale of the property within the next twelve months. During the third quarter of 2022, we reclassified one property previously held for the production of income to property held for sale. The property had a carrying value of $0.8 million as of December 31, 2023 and December 31, 2022 , respectively, and is recorded within our Corporate segment. The estimated fair value less costs to sell is above the carrying value of the property and we expect to close the sale of the property within the next twelve months. 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, 2023, the carrying amount of fixed maturity securities loaned to third parties under our securities lending program was $72.0 million, for which we received collateral in the form of cash and securities of $63.1 million and $12.5 million, respectively. As of December 31, 2022, the carrying amount of fixed maturity securities loaned to third parties under our securities lending program was $152.4 million, for which we received collateral in the form of cash and securities of $88.5 million and $69.8 million, respectively. We had no outstanding repurchase agreements at December 31, 2023 or December 31, 2022 . The remaining contractual maturities of our securities lending agreements disaggregated by class of collateral pledged are as follows: December 31 2023 2022 Overnight and Continuous (in millions of dollars) Borrowings United States Government and Government Agencies and Authorities $ — $ 0.3 Public Utilities 1.8 6.3 All Other Corporate Bonds 61.3 81.9 Total Borrowings $ 63.1 $ 88.5 Gross Amount of Recognized Liability for Securities Lending Transactions 63.1 88.5 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 2023 2022 (in millions of dollars) Carrying Value of FHLB Common Stock $ 15.7 $ 17.1 Advances from FHLB 64.5 99.1 Carrying Value of Collateral Posted to FHLB Fixed Maturity Securities $ 589.0 $ 527.1 Commercial Mortgage Loans 986.8 801.9 Total Carrying Value of Collateral Posted to FHLB $ 1,575.8 $ 1,329.0 Offsetting of Financial Instruments We enter into master netting agreements with each of our derivative's 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, 2023 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 $ 99.9 $ — $ 99.9 $ (91.9) $ (6.4) $ 1.6 Securities Lending 72.0 — 72.0 (8.9) (63.1) — Total $ 171.9 $ — $ 171.9 $ (100.8) $ (69.5) $ 1.6 Financial Liabilities: Derivatives $ 116.2 $ — $ 116.2 $ (109.4) $ — $ 6.8 Securities Lending 63.1 — 63.1 (63.1) — — Total $ 179.3 $ — $ 179.3 $ (172.5) $ — $ 6.8 December 31, 2022 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 $ 89.1 $ — $ 89.1 $ (38.0) $ (49.4) $ 1.7 Securities Lending 152.4 — 152.4 (63.9) (88.5) — Total $ 241.5 $ — $ 241.5 $ (101.9) $ (137.9) $ 1.7 Financial Liabilities: Derivatives $ 74.0 $ — $ 74.0 $ (73.2) $ — $ 0.8 Securities Lending 88.5 — 88.5 (88.5) — — Total $ 162.5 $ — $ 162.5 $ (161.7) $ — $ 0.8 Net Investment Income Net investment income reported in our consolidated statements of income is presented below. Year Ended December 31 2023 2022 2021 (in millions of dollars) Fixed Maturity Securities $ 1,853.7 $ 1,849.8 $ 1,888.2 Derivatives 45.1 57.8 68.6 Mortgage Loans 92.5 101.5 105.0 Policy Loans 20.8 20.0 19.7 Other Long-term Investments Perpetual Preferred Securities 1 2.5 5.0 6.9 Private Equity Partnerships 2 78.1 110.1 165.4 Other 9.2 9.4 5.5 Short-term Investments 68.7 20.0 1.3 Gross Investment Income 2,170.6 2,173.6 2,260.6 Less Investment Expenses 61.8 39.4 35.1 Less Investment Income on Participation Fund Account Assets 12.1 12.0 12.3 Net Investment Income $ 2,096.7 $ 2,122.2 $ 2,213.2 1 The net unrealized gain (loss) recognized in net investment income for the year ended December 31, 2023 related to perpetual preferred securities still held at December 31, 2023 was nominal . The net unrealized gain (loss) recognized in net investment income for the years ended December 31, 2022 and 2021 related to perpetual preferred securities still held at year-end was $2.8 million and $4.4 million, respectively. 2 The net unrealized gain recognized in net investment income for the year ended December 31, 2023 related to private equity partnerships still held at December 31, 2023 was $102.9 million, reduced by net management fees and partnership expenses of $(24.8) million. For the years ended December 31, 2022 and 2021, the net unrealized gain recognized in net investment income related to private equity partnerships still held at year-end was $124.1 million and $177.7 million, respectively, reduced by net management fees and partnership expenses of $(14.0) million and $(12.3) million, respectively. See Note 2 for further discussion of private equity partnerships. Investment Gain and Loss Investment gains and losses are as follows: Year Ended December 31 2023 2022 2021 (in millions of dollars) Fixed Maturity Securities Gross Gains on Sales 1 $ 4.4 $ 2.3 $ 76.2 Gross Losses on Sales (53.1) (28.8) (11.5) Credit Losses (2.2) (4.6) (9.3) Mortgage Loans and Other Invested Assets Gross Gains on Sales 6.0 1.4 5.8 Gross Losses on Sales (1.0) — — Impairment Loss (3.0) — — Change in Allowance for Credit Losses (0.9) (1.0) 4.7 Embedded Derivative in Modified Coinsurance Arrangement 12.4 16.2 9.7 All Other Derivatives (0.6) 2.6 3.1 Foreign Currency Transactions 2.0 (3.8) (2.0) Net Investment Gain (Loss) $ (36.0) $ (15.7) $ 76.7 1" id="sjs-B4">Fixed Maturity Securities At December 31, 2023 and 2022, 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, 2023 Amortized Cost, Gross of ACL 1 ACL 1 Gross Gross Fair (in millions of dollars) United States Government and Government Agencies and Authorities $ 618.6 $ — $ 25.3 $ 19.1 $ 624.8 States, Municipalities, and Political Subdivisions 4,041.3 — 135.3 498.2 3,678.4 Foreign Governments 982.1 — 29.8 121.2 890.7 Public Utilities 5,398.2 — 217.1 293.7 5,321.6 Mortgage/Asset-Backed Securities 658.0 — 10.1 24.0 644.1 All Other Corporate Bonds 26,708.4 2.2 771.8 1,807.3 25,670.7 Redeemable Preferred Stocks 4.0 — — 0.4 3.6 Total Fixed Maturity Securities $ 38,410.6 $ 2.2 $ 1,189.4 $ 2,763.9 $ 36,833.9 December 31, 2022 Amortized Cost, Gross of ACL 1 ACL 1 Gross Gross Fair (in millions of dollars) United States Government and Government Agencies and Authorities $ 503.8 $ — $ 20.3 $ 25.9 $ 498.2 States, Municipalities, and Political Subdivisions 4,006.0 — 87.1 635.9 3,457.2 Foreign Governments 908.1 — 34.9 115.9 827.1 Public Utilities 5,170.9 — 141.0 355.0 4,956.9 Mortgage/Asset-Backed Securities 592.1 — 8.2 27.0 573.3 All Other Corporate Bonds 26,640.3 — 452.1 2,567.8 24,524.6 Redeemable Preferred Stocks 4.0 — — 0.5 3.5 Total Fixed Maturity Securities $ 37,825.2 $ — $ 743.6 $ 3,728.0 $ 34,840.8 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, 2023 Less Than 12 Months 12 Months or Greater Fair Gross Fair Gross (in millions of dollars) United States Government and Government Agencies and Authorities $ 118.8 $ 0.7 $ 197.3 $ 18.4 States, Municipalities, and Political Subdivisions 128.0 4.0 2,035.1 494.2 Foreign Governments 149.9 3.3 312.9 117.9 Public Utilities 373.7 10.4 1,720.6 283.3 Mortgage/Asset-Backed Securities 60.3 2.5 316.7 21.5 All Other Corporate Bonds 1,483.8 26.8 14,215.2 1,780.5 Redeemable Preferred Stocks — — 3.6 0.4 Total Fixed Maturity Securities $ 2,314.5 $ 47.7 $ 18,801.4 $ 2,716.2 December 31, 2022 Less Than 12 Months 12 Months or Greater Fair Gross Fair Gross (in millions of dollars) United States Government and Government Agencies and Authorities $ 246.6 $ 22.6 $ 12.2 $ 3.3 States, Municipalities, and Political Subdivisions 1,920.1 476.1 346.6 159.8 Foreign Governments 160.1 47.9 176.9 68.0 Public Utilities 2,242.2 252.0 255.2 103.0 Mortgage/Asset-Backed Securities 386.6 27.0 0.1 — All Other Corporate Bonds 15,865.6 1,799.7 2,194.1 768.1 Redeemable Preferred Stocks 3.5 0.5 — — Total Fixed Maturity Securities $ 20,824.7 $ 2,625.8 $ 2,985.1 $ 1,102.2 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, 2023 Amortized Cost, Net of ACL 1 Unrealized Gain Position Unrealized Loss Position Gross Gain Fair Value Gross Loss Fair Value (in millions of dollars) 1 year or less $ 935.0 $ 0.9 $ 140.8 $ 7.5 $ 787.6 Over 1 year through 5 years 7,594.4 128.2 2,685.7 179.0 4,857.9 Over 5 years through 10 years 9,430.3 372.1 4,100.0 610.8 5,091.6 Over 10 years 19,790.7 678.1 8,524.4 1,942.6 10,001.8 37,750.4 1,179.3 15,450.9 2,739.9 20,738.9 Mortgage/Asset-Backed Securities 658.0 10.1 267.1 24.0 377.0 Total Fixed Maturity Securities $ 38,408.4 $ 1,189.4 $ 15,718.0 $ 2,763.9 $ 21,115.9 December 31, 2022 Amortized Cost, Net of ACL 1 Unrealized Gain Position Unrealized Loss Position Gross Gain Fair Value Gross Loss Fair Value (in millions of dollars) 1 year or less $ 1,133.5 $ 2.9 $ 339.1 $ 5.7 $ 791.6 Over 1 year through 5 years 7,090.8 86.7 1,953.2 238.4 4,985.9 Over 5 years through 10 years 10,096.7 294.8 3,538.9 863.8 5,988.8 Over 10 years 18,912.1 351.0 5,013.2 2,593.1 11,656.8 37,233.1 735.4 10,844.4 3,701.0 23,423.1 Mortgage/Asset-Backed Securities 592.1 8.2 186.6 27.0 386.7 Total Fixed Maturity Securities $ 37,825.2 $ 743.6 $ 11,031.0 $ 3,728.0 $ 23,809.8 1 Allowance for Credit Losses The following chart depicts an analysis of our fixed maturity security portfolio between investment-grade and below-investment-grade categories as of December 31, 2023: Gross Unrealized Loss Fair Value Gross Unrealized Gain Amount Percent of Total Gross Unrealized Loss (in millions of dollars) Investment-Grade $ 35,344.9 $ 1,169.1 $ 2,660.3 96.3 % Below-Investment-Grade 1,489.0 20.3 103.6 3.7 Total Fixed Maturity Securities $ 36,833.9 $ 1,189.4 $ 2,763.9 100.0 % 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, 2023, 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 less allowance for credit losses. As of December 31, 2023, we held 832 individual investment-grade fixed maturity securities and 75 individual below-investment-grade fixed maturity securities that were in an unrealized loss position, of which 787 investment-grade fixed maturity securities and 70 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 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. The following tables present a rollforward of the allowance for credit losses on available-for-sale fixed maturity securities, which were classified as "all other corporate bonds" during the year ended December 31, 2023 and "public utilities" during the year ended December 31, 2022, respectively. Year Ended December 31 2023 2022 (in millions of dollars) Balance, beginning of period $ — $ — Credit losses on securities for which credit losses were not previously recorded 2.2 4.6 Change in allowance on securities disposed during the period — (4.6) Balance, end of period $ 2.2 $ — In the fourth quarter of 2022, the issuer of a fixed maturity security previously classified as "public utilities" entered into a troubled debt restructuring agreement. In order to maximize recovery of the investment, the debt was restructured by way of principal reduction, interest forgiveness, and a debt to equity conversion. Principal owed was reduced by $4.8 million, semi-annual interest payments for the period beginning June 30, 2022 and ending June 30, 2024 were forgiven, and a portion of the remaining debt was converted to equity. As of December 31, 2022, we received $4.9 million of an equity stake in the restructured entity, and recorded receivables for $5.2 million and $2.8 million in cash. The full $8.0 million of the recorded receivables was subsequently received in 2023. The amortized cost of the fixed maturity security prior to the restructuring was $17.7 million, and the restructuring resulted in a total loss of $4.8 million, which was recognized during 2022. At December 31, 2023, we had commitments of $122.0 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, which are passive in nature, include minority ownership interests in private equity partnerships, tax credit partnerships, and special purpose entities. Our maximum exposure to loss is limited to the carrying value of these investments in private equity partnerships, tax credit 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, 2023, the carrying amount of our variable interest entity investments that are not consolidated in our financial statements was $1,326.5 million, comprised of $0.3 million of tax credit partnerships and $1,326.2 million of private equity partnerships. At December 31, 2022, the carrying amount of our variable interest entity investments that are not consolidated in our financial statements was $1,195.3 million, comprised of $1.0 million of tax credit partnerships and $1,194.3 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 2023 2022 2021 (in millions of dollars) Income Tax Credits $ 1.1 $ 8.0 $ 21.6 Amortization, Net of Tax (0.5) (5.9) (15.0) Income Tax Benefit $ 0.6 $ 2.1 $ 6.6 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 $0.2 million of unfunded unconditional commitments at December 31, 2023. 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 based on internal valuation of the collateral at least every three years for each loan, and properties undergo a general inspection at least every two years. Our general policy for newly issued loans is to have a debt service coverage ratio greater than 1.25 times on a normalized 25 year amortization period. We update our debt service coverage ratios annually. We carry our mortgage loans at amortized cost less an allowance for expected credit losses. The amortized cost of our mortgage loans was $2,328.4 million and $2,444.7 million at December 31, 2023 and 2022, respectively. The allowance for expected credit losses was $10.2 million and $9.3 million at December 31, 2023 and 2022, respectively. Interest income is accrued on the principal amount of the loan based on the loan's contractual interest rate. We report accrued interest income for our mortgage loans as accrued investment income on our consolidated balance sheets, and the amount of the accrued income was $7.2 million and $7.7 million at December 31, 2023 and 2022, respectively. The carrying amount of mortgage loans by property type and geographic region are presented below. December 31 2023 2022 (in millions of dollars) Carrying Percent of Carrying Percent of Amount Total Amount Total Property Type Apartment $ 685.8 29.6 % $ 688.6 28.3 % Industrial 706.0 30.5 745.3 30.6 Office 379.9 16.4 423.0 17.4 Retail 503.9 21.7 534.5 21.9 Other 42.6 1.8 44.0 1.8 Total $ 2,318.2 100.0 % $ 2,435.4 100.0 % Region New England $ 55.1 2.4 % $ 52.4 2.2 % Mid-Atlantic 155.1 6.7 192.4 7.9 East North Central 314.4 13.6 313.0 12.9 West North Central 163.5 7.0 181.4 7.4 South Atlantic 553.0 23.8 539.3 22.1 East South Central 110.7 4.8 101.8 4.2 West South Central 200.9 8.7 212.6 8.7 Mountain 282.7 12.2 298.7 12.3 Pacific 482.8 20.8 543.8 22.3 Total $ 2,318.2 100.0 % $ 2,435.4 100.0 % 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 quality rating based on a comprehensive rating system used to evaluate the risk of the loan. The factors we use to derive our internal quality ratings may include the following: • Loan-to-value ratio based on internal valuation of property • 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 quality ratings on an annual basis. This review process is performed more frequently for mortgage loans deemed to have a higher risk of delinquency. The following tables present information about mortgage loans by the applicable internal quality indicators: December 31 2023 2022 (in millions of dollars) Carrying Amount Percent of Total Carrying Amount Percent of Total Internal Mortgage Rating AA $ 85.2 3.7 % $ 92.3 3.8 % A 942.5 40.6 843.9 34.6 BBB 1,249.5 53.9 1,458.0 59.9 BB 41.0 1.8 41.2 1.7 Total $ 2,318.2 100.0 % $ 2,435.4 100.0 % Loan-to-Value Ratio 1 <= 65% $ 1,409.9 60.8 % $ 1,389.6 57.0 % > 65% <= 75% 707.0 30.5 937.2 38.5 > 75% <= 85% 136.5 5.9 75.0 3.1 > 85% 64.8 2.8 33.6 1.4 Total $ 2,318.2 100.0 % $ 2,435.4 100.0 % 1 Loan-to-Value Ratio utilizes the most recent internal valuation of the property There were no gross write-offs for the periods ending December 31, 2023 or 2022. The following tables present the amortized cost of our mortgage loans by year of origination and internal quality indicators for the years ended December 31, 2023 and 2022: Year Ended December 31, 2023 Prior to 2019 2019 2020 2021 2022 2023 Total (in millions of dollars) Internal Mortgage Rating AA $ 74.3 $ 11.0 $ — $ — $ — $ — $ 85.3 A 589.0 100.3 94.1 100.1 23.2 38.0 944.7 BBB 618.4 224.8 71.4 248.0 64.4 29.2 1,256.2 BB 42.2 — — — — — 42.2 Total Amortized Cost 1,323.9 336.1 165.5 348.1 87.6 67.2 2,328.4 Allowance for credit losses (6.3) (1.3) (0.6) (1.0) (0.6) (0.4) (10.2) Carrying Amount $ 1,317.6 $ 334.8 $ 164.9 $ 347.1 $ 87.0 $ 66.8 $ 2,318.2 Loan-to-Value Ratio 1 <=65% $ 908.3 $ 197.7 $ 116.4 $ 145.2 $ 16.2 $ 30.0 $ 1,413.8 >65<=75% 252.1 138.4 40.8 171.0 71.4 37.2 710.9 >75%<=85% 97.3 — 8.3 31.9 — — 137.5 >85% 66.2 — — — — — 66.2 Total Amortized Cost 1,323.9 336.1 165.5 348.1 87.6 67.2 2,328.4 Allowance for credit losses (6.3) (1.3) (0.6) (1.0) (0.6) (0.4) (10.2) Carrying Amount $ 1,317.6 $ 334.8 $ 164.9 $ 347.1 $ 87.0 $ 66.8 $ 2,318.2 1 Loan-to-Value Ratio utilizes the most recent internal valuation of the property Year Ended December 31, 2022 Prior to 2018 2018 2019 2020 2021 2022 Total (in millions of dollars) Internal Mortgage Rating AA $ 53.8 $ 27.5 $ 11.1 $ — $ — $ — $ 92.4 A 485.0 123.3 96.8 35.9 80.6 24.0 845.6 BBB 534.0 219.8 236.9 134.0 275.8 64.6 1,465.1 BB 35.7 5.9 — — — — 41.6 Total Amortized Cost 1,108.5 376.5 344.8 169.9 356.4 88.6 2,444.7 Allowance for credit losses (4.3) (1.8) (1.3) (0.6) (0.8) (0.5) (9.3) Carrying Amount $ 1,104.2 $ 374.7 $ 343.5 $ 169.3 $ 355.6 $ 88.1 $ 2,435.4 Loan-to-Value Ratio 1 <=65% $ 782.6 $ 189.0 $ 193.9 $ 81.3 $ 128.9 $ 16.9 $ 1,392.6 >65<=75% 230.2 181.6 150.9 80.1 227.5 71.7 942.0 >75%<=85% 67.5 — — 8.5 — — 76.0 >85% 28.2 5.9 — — — — 34.1 Total Amortized Cost 1,108.5 376.5 344.8 169.9 356.4 88.6 2,444.7 Allowance for credit losses (4.3) (1.8) (1.3) (0.6) (0.8) (0.5) (9.3) Carrying Amount $ 1,104.2 $ 374.7 $ 343.5 $ 169.3 $ 355.6 $ 88.1 $ 2,435.4 1 Loan-to-Value Ratio utilizes the most recent internal valuation of the property The following tables present a roll forward of allowance for expected credit losses by loan-to-value ratio for the years ended December 31, 2023 and 2022: Year Ended December 31, 2023 Beginning of Period Current Period Provisions Write-Offs Recoveries End of Period (in millions of dollars) Loan-to-Value Ratio 1 <=65% $ 3.0 $ 0.8 $ — $ — $ 3.8 >65<=75% 4.7 (0.9) — — 3.8 >75%<=85% 1.1 0.1 — — 1.2 >85% 0.5 0.9 — — 1.4 Total $ 9.3 $ 0.9 $ — $ — $ 10.2 Year Ended December 31, 2022 Beginning of Period Current Period Provisions Write-Offs Recoveries End of Period (in millions of dollars) Loan-to-Value Ratio 1 <=65% $ 2.6 $ 0.4 $ — $ — $ 3.0 >65<=75% 4.7 — — — 4.7 >75%<=85% 0.7 0.4 — — 1.1 >85% 0.3 0.2 — — 0.5 Total $ 8.3 $ 1.0 $ — $ — $ 9.3 1 Loan-to-Value Ratio utilizes the most recent internal valuation of the property For the years ended December 31, 2023 and 2022 our estimate for expected credit losses was generally consistent between periods. During the year ended December 31, 2023 we granted an other-than-insignificant payment delay for a commercial mortgage loan with an amortized cost of $14.2 million, which deferred the principal payment for 18 months. This modification represents less than one percent of the commercial mortgage loan portfolio balance. There were no troubled debt restructurings during 2022 or 2021. We held no mortgage loans that were greater than 90 days past due regarding principal and/or interest payments for the years ended December 31, 2023, 2022, or 2021. We had no loan foreclosures for the years ended December 31, 2023, 2022, or 2021. Other than our allowance for expected credit losses, we had no specifically identified impaired mortgage loans for the years ended December 31, 2023, 2022, and 2021, nor did we recognize any interest income on mortgage loans subsequent to impairment. For the year ended December 31, 2023 we had no commitments to fund certain commercial mortgage loans. For the year ended December 31, 2022 we had $5.0 million in commitments 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. For the year ended December 31, 2023, we had no expected credit losses related to unfunded commitments on our consolidated balance sheets. For the year ended December 31, 2022, we had a nominal amount of expected credit losses related to unfunded commitments on our consolidated balance sheets. Investment Real Estate Our investment real estate balance was $64.4 million and $71.6 million at December 31, 2023 and 2022, respectively, and the associated accumulated depreciation was $127.2 million and $122.1 million at December 31, 2023 and 2022, respectively. For the year ended December 31, 2023, we recognized a $3.0 million impairment related to certain of our real estate held for investment. We did not recognize any impairments related to our real estate held for investment during 2022 or 2021. Our held for sale real estate balance was $40.9 million at both December 31, 2023 and December 31, 2022 and the associated accumulated depreciation was $54.2 million at both December 31, 2023 and December 31, 2022 . During the first quarter of 2022, we reclassified one property previously held for the production of income to property held for sale. The carrying value of the property was $40.1 million at both December 31, 2023 and December 31, 2022 , and is primarily recorded within our Corporate segment. The estimated fair value less costs to sell is above the carrying value of the property and we expect to close the sale of the property within the next twelve months. During the third quarter of 2022, we reclassified one property previously held for the production of income to property held for sale. The property had a carrying value of $0.8 million as of December 31, 2023 and December 31, 2022 , respectively, and is recorded within our Corporate segment. The estimated fair value less costs to sell is above the carrying value of the property and we expect to close the sale of the property within the next twelve months. 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, 2023, the carrying amount of fixed maturity securities loaned to third parties under our securities lending program was $72.0 million, for which we received collateral in the form of cash and securities of $63.1 million and $12.5 million, respectively. As of December 31, 2022, the carrying amount of fixed maturity securities loaned to third parties under our securities lending program was $152.4 million, for which we received collateral in the form of cash and securities of $88.5 million and $69.8 million, respectively. We had no outstanding repurchase agreements at December 31, 2023 or December 31, 2022 . The remaining contractual maturities of our securities lending agreements disaggregated by class of collateral pledged are as follows: December 31 2023 2022 Overnight and Continuous (in millions of dollars) Borrowings United States Government and Government Agencies and Authorities $ — $ 0.3 Public Utilities 1.8 6.3 All Other Corporate Bonds 61.3 81.9 Total Borrowings $ 63.1 $ 88.5 Gross Amount of Recognized Liability for Securities Lending Transactions 63.1 88.5 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 2023 2022 (in millions of dollars) Carrying Value of FHLB Common Stock $ 15.7 $ 17.1 Advances from FHLB 64.5 99.1 Carrying Value of Collateral Posted to FHLB Fixed Maturity Securities $ 589.0 $ 527.1 Commercial Mortgage Loans 986.8 801.9 Total Carrying Value of Collateral Posted to FHLB $ 1,575.8 $ 1,329.0 Offsetting of Financial Instruments We enter into master netting agreements with each of our derivative's 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, 2023 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 $ 99.9 $ — $ 99.9 $ (91.9) $ (6.4) $ 1.6 Securities Lending 72.0 — 72.0 (8.9) (63.1) — Total $ 171.9 $ — $ 171.9 $ (100.8) $ (69.5) $ 1.6 Financial Liabilities: Derivatives $ 116.2 $ — $ 116.2 $ (109.4) $ — $ 6.8 Securities Lending 63.1 — 63.1 (63.1) — — Total $ 179.3 $ — $ 179.3 $ (172.5) $ — $ 6.8 December 31, 2022 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 $ 89.1 $ — $ 89.1 $ (38.0) $ (49.4) $ 1.7 Securities Lending 152.4 — 152.4 (63.9) (88.5) — Total $ 241.5 $ — $ 241.5 $ (101.9) $ (137.9) $ 1.7 Financial Liabilities: Derivatives $ 74.0 $ — $ 74.0 $ (73.2) $ — $ 0.8 Securities Lending 88.5 — 88.5 (88.5) — — Total $ 162.5 $ — $ 162.5 $ (161.7) $ — $ 0.8 Net Investment Income Net investment income reported in our consolidated statements of income is presented below. Year Ended December 31 2023 2022 2021 (in millions of dollars) Fixed Maturity Securities $ 1,853.7 $ 1,849.8 $ 1,888.2 Derivatives 45.1 57.8 68.6 Mortgage Loans 92.5 101.5 105.0 Policy Loans 20.8 20.0 19.7 Other Long-term Investments Perpetual Preferred Securities 1 2.5 5.0 6.9 Private Equity Partnerships 2 78.1 110.1 165.4 Other 9.2 9.4 5.5 Short-term Investments 68.7 20.0 1.3 Gross Investment Income 2,170.6 2,173.6 2,260.6 Less Investment Expenses 61.8 39.4 35.1 Less Investment Income on Participation Fund Account Assets 12.1 12.0 12.3 Net Investment Income $ 2,096.7 $ 2,122.2 $ 2,213.2 1 The net unrealized gain (loss) recognized in net investment income for the year ended December 31, 2023 related to perpetual preferred securities still held at December 31, 2023 was nominal . The net unrealized gain (loss) recognized in net investment income for the years ended December 31, 2022 and 2021 related to perpetual preferred securities still held at year-end was $2.8 million and $4.4 million, respectively. 2 The net unrealized gain recognized in net investment income for the year ended December 31, 2023 related to private equity partnerships still held at December 31, 2023 was $102.9 million, reduced by net management fees and partnership expenses of $(24.8) million. For the years ended December 31, 2022 and 2021, the net unrealized gain recognized in net investment income related to private equity partnerships still held at year-end was $124.1 million and $177.7 million, respectively, reduced by net management fees and partnership expenses of $(14.0) million and $(12.3) million, respectively. See Note 2 for further discussion of private equity partnerships. Investment Gain and Loss Investment gains and losses are as follows: Year Ended December 31 2023 2022 2021 (in millions of dollars) Fixed Maturity Securities Gross Gains on Sales 1 $ 4.4 $ 2.3 $ 76.2 Gross Losses on Sales (53.1) (28.8) (11.5) Credit Losses (2.2) (4.6) (9.3) Mortgage Loans and Other Invested Assets Gross Gains on Sales 6.0 1.4 5.8 Gross Losses on Sales (1.0) — — Impairment Loss (3.0) — — Change in Allowance for Credit Losses (0.9) (1.0) 4.7 Embedded Derivative in Modified Coinsurance Arrangement 12.4 16.2 9.7 All Other Derivatives (0.6) 2.6 3.1 Foreign Currency Transactions 2.0 (3.8) (2.0) Net Investment Gain (Loss) $ (36.0) $ (15.7) $ 76.7 1

Derivative Financial Instrument

Derivative Financial Instruments	12 Months Ended
	Dec. 31, 2023
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, credit risk, and equity 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, credit default swaps, and total return 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 were 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 used 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 used 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 the anticipated issuance of fixed rate long-term 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 predetermined price or yield. Derivatives designated as either cash flow or fair value hedges and used to reduce our exposure to foreign currency risk are as follows: • Foreign currency interest rate swaps are used to hedge the currency risk of certain foreign currency-denominated fixed maturity securities owned for portfolio diversification. Under these swap agreements, we agree to pay, at specified intervals, fixed rate foreign currency-denominated principal and interest payments in exchange for fixed rate payments in the functional currency of the operating segment. Derivatives not designated as hedging instruments and used to reduce our exposure to foreign currency risk, credit losses on securities owned, and volatility of the underlying deferred assets in our non-qualified defined contribution plan are as follows: • Foreign currency interest rate swaps previously designated as hedges were used to hedge the currency risk of certain foreign currency-denominated fixed maturity securities owned for portfolio diversification. These derivatives were effective hedges prior to novation to a new counterparty. In conjunction with the novation, these derivatives were de-designated as hedges. We agree to pay, at specified intervals, fixed rate foreign currency-denominated principal and interest payments in exchange for fixed rate payments in the functional currency of the operating segment. We hold offsetting swaps wherein we agree to pay fixed rate principal and interest payments in the functional currency of the operating segment in exchange for fixed rate foreign currency-denominated payments. • Credit default swaps were 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 occurred, our counterparty could have either paid us a net cash settlement, or we could have surrendered 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 investments. • Total Return Swaps are used to economically hedge a portion of the liability related to our non-qualified defined contribution plan. A total return swap is an agreement in which we pay a floating rate of interest to the counterparty and receive the total return on a portfolio of mutual funds and exchange traded funds. These swaps are cash settled on the last day of every month and the notional is re-established each month based on plan participant actions. 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 changes in interest rates, exchange rates, and equity prices) 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, 2023 and 2022, we had $1.6 million and $1.7 million credit exposure on derivatives, respectively. The table below summarizes the nature and amount of collateral received from and posted to our derivative counterparties. December 31 2023 2022 (in millions of dollars) Carrying Value of Collateral Received from Counterparties Cash $ 11.1 $ 49.4 Fixed Maturity Securities 26.3 — $ 37.4 $ 49.4 Carrying Value of Collateral Posted to Counterparties Cash $ — $ 5.1 Fixed Maturity Securities 39.8 39.6 $ 39.8 $ 44.7 See Note 3 for further discussion of our master netting agreements. All 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 $116.2 million and $74.0 million at December 31, 2023 and 2022, respectively. Cash Flow Hedges As of December 31, 2023 and 2022, we had $149.5 million and $168.9 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. As of December 31, 2023 and 2022, we had $1,905.0 million and $764.0 million, respectively, notional amount of forward benchmark interest rate locks to hedge the anticipated purchase of fixed maturity securities. During 2021, we entered into a $250.0 million notional forward benchmark interest rate lock in order to hedge the interest rate risk associated with the cash flows related to the early redemption of certain of our debt securities. We terminated the interest rate lock in 2021 and recognized a loss of $1.2 million that was reported as a cost related to the early retirement of debt in our income statement. During the first quarter of 2021, in connection with the Closed Block individual disability reinsurance transaction, we reclassified $0.6 million of deferred gains from accumulated other comprehensive income (AOCI) into earnings included in the net investment gain (loss) 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 14 for further discussion. As of December 31, 2023, we expect to amortize approximately $16.7 million of net deferred gains on derivative instruments during the next twelve months. This amount will be reclassified from AOCI 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 AOCI into earnings to offset the earnings impact of foreign currency translation of hedged items are not estimable. As of December 31, 2023, we are hedging the variability of future cash flows associated with forecasted transactions through the year 2063. Fair Value Hedges As of December 31, 2023 and 2022, we had $642.5 million and $557.8 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. The following table summarizes the carrying amount of hedged assets and the related cumulative basis adjustments related to our fair value hedges: Carrying Amount of Hedged Assets Cumulative Amount of Fair Value Hedging Adjustment Included in the Carrying Amount of the Hedged Assets December 31, 2023 December 31, 2022 December 31, 2023 December 31, 2022 (in millions of dollars) Fixed maturity securities: Receive fixed functional currency interest, pay fixed foreign currency interest $ 529.2 $ 394.4 $ (6.1) $ (24.8) For the years ended December 31, 2023, 2022, and 2021, $(21.1) million, $17.6 million, and $16.6 million, respectively, of the derivative instruments' gain (loss) related to cross-currency basis spread and forward points 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, 2023 and 2022, we held $132.0 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 investment gain or loss. As of December 31, 2023 and 2022, we held no single name credit default swaps. As of December 31, 2021, we held $11.6 million 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. These derivatives were not designated as hedges, and as such, changes in fair value related to these derivatives were reported in earnings as a component of net investment gain or loss. As of December 31, 2023 and 2022, we held $52.5 million and $54.3 million, respectively, notional amount of foreign currency forwards to mitigate the foreign currency risk associated with specific securities owned. 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 investment gain or loss. As of December 31, 2023 and 2022, we held $102.2 million and $76.9 million, respectively, notional amount of total return swaps to mitigate the volatility associated with changes in the fair value of the underlying notional assets in our non-qualified defined contribution plan. This derivative is an economic hedge not designated as a hedging instrument, and changes in fair value are reported as a component of other expenses in our income statement. We have an embedded derivative in a modified coinsurance arrangement for which we include in our net 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 notional amounts and fair values of derivative financial instruments, as reported in our consolidated balance sheets. Derivative assets are included in other long-term investments, while derivative liabilities are included in other liabilities within our consolidated balance sheets. The notional amounts represent the basis upon which our counterparty pay and receive amounts are calculated. December 31, 2023 Derivative Assets Derivative Liabilities Notional Fair Fair (in millions of dollars) Designated as Hedging Instruments Cash Flow Hedges Forward Benchmark Interest Rate Locks $ 1,905.0 $ 44.5 $ 77.8 Foreign Currency Interest Rate Swaps 149.5 14.2 4.5 Total Cash Flow Hedges 2,054.5 58.7 82.3 Fair Value Hedges Foreign Currency Interest Rate Swaps 642.5 38.2 16.7 Total Designated as Hedging Instruments $ 2,697.0 $ 96.9 $ 99.0 Not Designated as Hedging Instruments Foreign Currency Forwards $ 52.5 $ 3.0 $ 0.2 Foreign Currency Interest Rate Swaps 132.0 — 17.0 Total Return Swaps 102.2 — — Embedded Derivative in Modified Coinsurance Arrangement — — 1.5 Total Not Designated as Hedging Instruments $ 286.7 $ 3.0 $ 18.7 Total Derivatives $ 2,983.7 $ 99.9 $ 117.7 December 31, 2022 Derivative Assets Derivative Liabilities Notional Fair Fair (in millions of dollars) Designated as Hedging Instruments Cash Flow Hedges Forward Benchmark Interest Rate Locks $ 764.0 $ 1.6 $ 48.4 Foreign Currency Interest Rate Swaps 168.9 17.5 3.1 Total Cash Flow Hedges 932.9 19.1 51.5 Fair Value Hedges Foreign Currency Interest Rate Swaps 557.8 66.0 5.4 Total Designated as Hedging Instruments $ 1,490.7 $ 85.1 $ 56.9 Not Designated as Hedging Instruments Foreign Currency Forwards $ 54.3 $ 4.0 $ 0.1 Foreign Currency Interest Rate Swaps 132.0 — 17.0 Total Return Swaps 76.9 — — Embedded Derivative in Modified Coinsurance Arrangement — — 13.9 Total Not Designated as Hedging Instruments $ 263.2 $ 4.0 $ 31.0 Total Derivatives $ 1,753.9 $ 89.1 $ 87.9 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, 2023 Net Investment Income Net 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 $ 2,096.7 $ (36.0) $ 194.8 Gain (Loss) on Cash Flow Hedging Relationships Interest Rate Swaps: Hedged items 198.6 0.8 2.9 Derivatives Designated as Hedging Instruments 35.2 — — Foreign Exchange Contracts: Hedged items 9.6 0.4 — Derivatives Designated as Hedging Instruments — (0.4) — Forward Benchmark Interest Rate Locks: Hedged items 18.5 — — Derivatives Designated as Hedging Instruments (0.5) — — Gain (Loss) on Fair Value Hedging Relationships Foreign Exchange Contracts: Hedged items 14.5 18.7 — Derivatives Designated as Hedging Instruments 11.1 (18.7) — Year Ended December 31, 2022 Net Investment Income Net 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 $ 2,122.2 $ (15.7) $ 188.5 Gain (Loss) on Cash Flow Hedging Relationships Interest Rate Swaps: Hedged items 200.0 — 2.9 Derivatives Designated as Hedging Instruments 51.0 — — Foreign Exchange Contracts: Hedged items 12.3 (2.3) — Derivatives Designated as Hedging Instruments (0.8) 1.8 — Forward Benchmark Interest Rate Locks: Hedged items 0.5 — — Derivatives Designated as Hedging Instruments — — — Gain (Loss) on Fair Value Hedging Relationships Foreign Exchange Contracts: Hedged items 11.6 (26.8) — Derivatives Designated as Hedging Instruments 7.3 26.8 — Year Ended December 31, 2021 Net Investment Income Net 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 $ 2,213.2 $ 76.7 $ 185.0 Gain (Loss) on Cash Flow Hedging Relationships Interest Rate Swaps: Hedged items 220.4 2.7 29.2 Derivatives Designated as Hedging Instruments 64.6 2.0 5.0 Foreign Exchange Contracts: Hedged items 13.0 (0.1) — Derivatives Designated as Hedging Instruments 1.8 (0.1) — Gain (Loss) on Fair Value Hedging Relationships Foreign Exchange Contracts: Hedged items 9.8 (22.3) — Derivatives Designated as Hedging Instruments 4.6 22.3 — 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 2023 2022 2021 (in millions of dollars) Gain (Loss) Recognized in Other Comprehensive Income (Loss) on Derivatives Forwards $ (22.5) $ (49.8) $ (0.6) Foreign Exchange Contracts (4.3) 7.4 2.2 Total $ (26.8) $ (42.4) $ 1.6 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 2023 2022 2021 (in millions of dollars) Net Investment Gain (Loss) Credit Default Swaps $ — $ — $ (0.3) Foreign Exchange Contracts (0.6) 2.7 3.4 Embedded Derivative in Modified Coinsurance Arrangement 12.4 16.2 9.7 Total $ 11.8 $ 18.9 $ 12.8 Other Expenses (Gain) Loss on Total Return Swaps $ (13.6) $ 18.9 $ (8.5)

Accumulated Other Comprehensive

Accumulated Other Comprehensive Loss	12 Months Ended
	Dec. 31, 2023
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss)	Components of our accumulated other comprehensive loss, after tax, and related changes are as follows: Net Unrealized Gain (Loss) on Securities Effect of Change in Discount Rate Assumptions on the LFPB 1 Net Gain (Loss) on Hedges Foreign Currency Translation Adjustment Unrecognized Pension and Postretirement Benefit Costs Total (in millions of dollars) Balance at January 1, 2021, As Adjusted $ 5,315.8 $ (10,932.5) $ 97.8 $ (261.3) $ (530.0) $ (6,310.2) Other Comprehensive Income (Loss) Before Reclassifications (1,260.7) 2,361.8 14.7 (12.8) 116.3 1,219.3 Amounts Reclassified from Accumulated Other Comprehensive Income or Loss (40.7) — (50.7) — 17.7 (73.7) Net Other Comprehensive Income (Loss) (1,301.4) 2,361.8 (36.0) (12.8) 134.0 1,145.6 Balance at December 31, 2021 4,014.4 (8,570.7) 61.8 (274.1) (396.0) (5,164.6) Other Comprehensive Income (Loss) Before Reclassifications (7,066.0) 8,884.6 (30.4) (116.0) 49.7 1,721.9 Amounts Reclassified from Accumulated Other Comprehensive Income or Loss 23.2 — (41.0) — 12.2 (5.6) Net Other Comprehensive Income (Loss) (7,042.8) 8,884.6 (71.4) (116.0) 61.9 1,716.3 Balance at December 31, 2022 (3,028.4) 313.9 (9.6) (390.1) (334.1) (3,448.3) Other Comprehensive Income (Loss) Before Reclassifications 1,069.3 (962.3) (37.4) 69.0 (16.9) 121.7 Amounts Reclassified from Accumulated Other Comprehensive Income or Loss 40.0 — (26.7) — 5.3 18.6 Net Other Comprehensive Income (Loss) 1,109.3 (962.3) (64.1) 69.0 (11.6) 140.3 Balance at December 31, 2023 $ (1,919.1) $ (648.4) $ (73.7) $ (321.1) $ (345.7) $ (3,308.0) 1 Liability for Future Policy Benefits Amounts reclassified from accumulated other comprehensive income (loss) were recognized in our consolidated statements of income as follows: Year Ended December 31 2023 2022 2021 (in millions of dollars) Net Unrealized Gain (Loss) on Securities Net Investment Gain (Loss) Gain (Loss) on Sales on Securities $ (48.7) $ (24.8) $ 60.8 Credit Losses on Fixed Maturity Securities (2.2) (4.6) (9.3) (50.9) (29.4) 51.5 Income Tax Expense (Benefit) (10.9) (6.2) 10.8 Total $ (40.0) $ (23.2) $ 40.7 Net Gain (Loss) on Hedges Net Investment Income Gain on Interest Rate Swaps and Forwards $ 34.7 $ 51.1 $ 60.6 Gain (Loss) on Foreign Exchange Contracts (0.5) (1.0) 1.7 Net Investment Gain (Loss) Gain on Interest Rate Swaps — — 2.0 Gain (Loss) on Foreign Exchange Contracts (0.4) 1.8 (0.1) 33.8 51.9 64.2 Income Tax Expense 7.1 10.9 13.5 Total $ 26.7 $ 41.0 $ 50.7 Unrecognized Pension and Postretirement Benefit Costs Other Expenses Amortization of Net Actuarial Loss $ (7.2) $ (15.7) $ (22.6) Amortization of Prior Service Credit 0.2 0.2 0.2 (7.0) (15.5) (22.4) Income Tax Benefit (1.7) (3.3) (4.7) Total $ (5.3) $ (12.2) $ (17.7)

Financial Services, Insurance

Financial Services, Insurance	12 Months Ended
	Dec. 31, 2023
Insurance [Abstract]
Long-Duration Insurance Contracts Disclosure	Liabilities for future policy benefits represent the cost of claims that we estimate we will eventually pay to our policyholders which includes policy liabilities for claims not yet incurred and for claims that have been incurred or are estimated to have been incurred but not yet reported to us. Liabilities for future policy benefits also include the related expenses for our non interest-sensitive life and accident and health products. The liability for future policy benefits is calculated based on the present value of the estimated future policy benefits less the present value of estimated future net premiums collected. Net premiums represent the portion of the gross premium required to provide for all benefits and expenses, excluding acquisition costs or any costs that are required to be charged to expense as incurred. In calculating the liability for future policy benefits, our long-duration contracts are grouped into cohorts by product type and contract issue year. The calculation of the liability for future policy benefits involves numerous assumptions including assumptions related to discount rate, lapses, mortality, and morbidity. Cash flow assumptions are reviewed and updated, as needed, at least annually. Assumptions may be updated more frequently if necessary based on trending experience and future expectations. On a quarterly basis, cohort level cash flow measures are updated based on the emergence of actual experience. The initial, also referred to as the original, discount rate assumptions established for each cohort are used to determine interest accretion. After policy issuance or policy renewal, the discount rate assumptions are updated quarterly and used to update the liability at each reporting date to the current discount rate. The weighted average current discount rate was 4.8 percent at December 31, 2023, 5.0 percent at December 31, 2022, and 2.5 percent at December 31, 2021. The discount rate was lower at December 31, 2023 relative to December 31, 2022 due primarily to a decrease in credit spreads. The discount rate was higher at December 31, 2022 relative to December 31, 2021 due to an increase in U.S. Treasury rates. During our annual cash flow assumption review in 2023, we updated certain of our assumptions used to develop the liability for future policy benefits which resulted in a net increase to the liability. The increase to the liability for future policy benefits was driven primarily by assumption updates in the Closed Block long-term care product line, partially offset by assumption updates in the Unum US group disability product line and in the Colonial Life segment. The long-term care assumption updates were primarily driven by lower expectations for active policy lapse and mortality assumptions, partially offset by an increase to expected future premium rate increases. The Unum US group disability product line assumption updates were primarily related to claim resolution assumptions driven by favorable claim recovery trends, while the Colonial Life segment assumption updates were driven by improved claim cost assumptions and increases in policyholder lapse rates. During our annual cash flow assumption review in 2022, we updated certain of our assumptions used to develop the liability for future policy benefits which resulted in a net increase to the liability. The increase to the liability for future policy benefits was driven primarily by assumption updates related to the reinsured portion of our Closed Block segment, mostly offset by assumption updates in the Unum US segment and the Colonial Life segment. The Closed Block segment assumption updates related to the reinsured portion of our all other product line primarily included updates to mortality assumptions for the advanced age portion of our individual disability claimant population. This advanced age claimant population was included in the block ceded as a part of the Closed Block individual disability reinsurance transaction with Commonwealth Annuity and Life Insurance Company. As a result, a corresponding increase was reported in our consolidated balance sheet as a reinsurance recoverable related to these assumption updates. The Unum US segment assumption updates were primarily driven by sustained improvement in claim recovery trends in our group disability and group life product lines, partially offset by lower social security benefit offsets in our group disability product line. The Colonial Life segment assumption updates were primarily driven by improved claim cost assumptions. During our annual cash flow assumption review in 2021, we updated certain of our assumptions used to develop the liability for future policy benefits which resulted in a net decrease to the liability. The decrease to the liability for future policy benefits was driven primarily by assumption updates in the Unum US group disability product line due primarily to sustained improvement in the claim recovery trends since our last assumption update. Actual variance from expected experience for 2023 was due primarily to the Unum US group disability, Unum US group life and accidental death and dismemberment, Unum US individual disability, and Closed Block long-term care product lines. The variance for the Unum US group disability product line was driven by higher than expected claim resolutions driven by recoveries, and the variance in the group life and accidental death and dismemberment product line was driven by favorable mortality experience and favorable recovery experience for waiver of premium benefits. The variance in the Unum US individual disability product line was driven primarily by lower than expected new claim incidence, while the variance for the Closed Block long-term care product line was driven by higher than expected claim incidence. Actual variance from expected experience for 2022 was due primarily to the Unum US group disability, Unum US group life and accidental death and dismemberment, and the Unum UK group product lines, as well as the Colonial Life segment. The variance for the Unum US group disability product line was driven by higher than expected claim resolutions driven by recoveries, and the variance in the group life and accidental death and dismemberment product line was driven by lower than expected new claim incidence for waiver of premium benefits. The variance in the Unum UK group product lines was driven by an increase in inflation-linked experience compared to expectations. The variance for the Colonial Life segment was driven primarily by lower claim costs. Actual variance from expected experience for 2021 was due primarily to the Unum US group disability, Unum US individual disability, and Colonial Life cancer and critical illness product line. The variance for the Unum US group disability product line was driven by higher than expected claim resolutions driven by recoveries, and the variance in the Unum US individual disability product line was driven by lower than expected new claim incidence. The variance in the Colonial Life cancer and critical illness product line was driven by lower claim costs. For the year ended December 31, 2023, there were certain cohorts within the Closed Block segment, related to our long-term care product line, for which net premiums exceeded gross premiums, which resulted in a $226.5 million reduction to income before income tax. For the years ended December 31, 2023, 2022, and 2021, there were certain cohorts within the Colonial Life segment, related to our cancer and critical illness product line for which net premiums exceeded the gross premiums which had an immaterial impact to income before income tax. There were no other product lines with cohorts for which net premiums exceeded gross premiums for the years ended December 31, 2023, 2022, and 2021. The following table presents balances as well as the changes in the liability for future policy benefits for traditional long duration products. Consolidated December 31 2023 2022 2021 (in millions of dollars) Present Value of Expected Net Premiums Balance, beginning of year $ 12,426.2 $ 15,881.3 $ 17,095.9 Beginning balance at original discount rate 12,695.3 13,186.2 13,623.5 Effect of changes in cash flow assumptions 1,499.2 (101.9) (177.1) Effect of actual variances from expected experience (82.5) (269.6) (328.3) Adjusted beginning of year balance 14,112.0 12,814.7 13,118.1 Issuances 1,054.9 877.5 1,083.9 Interest accretion 584.0 566.0 631.9 Net premiums collected (1,537.4) (1,542.3) (1,627.4) Foreign currency 29.7 (20.6) (20.3) Ending balance at original discount rate 14,243.2 12,695.3 13,186.2 Effect of change in discount rate assumptions 174.6 (269.1) 2,695.1 Balance, end of period $ 14,417.8 $ 12,426.2 $ 15,881.3 Present Value of Expected Future Policy Benefits Balance, beginning of year $ 48,929.4 $ 65,305.0 $ 69,530.5 Beginning balance at original discount rate 49,689.0 50,397.2 50,752.4 Effect of changes in cash flow assumptions 1,702.0 (92.4) (379.9) Effect of actual variances from expected experience (310.8) (535.1) (635.9) Adjusted beginning of year balance 51,080.2 49,769.7 49,736.6 Issuances 1 3,072.2 3,194.5 3,675.0 Interest accretion 2,227.2 2,236.2 2,359.6 Benefit payments (5,236.1) (5,231.0) (5,315.7) Foreign currency 162.2 (280.4) (58.3) Ending balance at original discount rate 51,305.7 49,689.0 50,397.2 Effect of change in discount rate assumptions 1,117.9 (759.6) 14,907.8 Balance, end of period $ 52,423.6 $ 48,929.4 $ 65,305.0 Net liability for future policy benefits $ 38,005.8 $ 36,503.2 $ 49,423.7 Other 1,753.3 1,854.5 2,355.9 Total liability for future policy benefits 39,759.1 38,357.7 51,779.6 Less: Reinsurance recoverable related to future policy benefits 7,756.1 8,128.2 10,348.2 Net liability for future policy benefits, after reinsurance recoverable $ 32,003.0 $ 30,229.5 $ 41,431.4 1 Issuances include new policy issuances for most product lines. For our Unum US group disability, Unum US group life and AD&D and Closed Block - All Other product lines and certain of our Unum International product lines, this line represents new claim incurrals. The following tables summarize the amount of gross premiums and interest accretion reflected in the statements of income as well as the undiscounted and discounted expected gross premiums and expected future benefit payments and the weighted average interest rates for traditional long duration products presented in the rollforward activity above. Consolidated Year Ended December 31 2023 2022 2021 (in millions of dollars) Amount recognized in the statement of income: Gross premiums or assessments $ 9,690.7 $ 9,391.8 $ 9,263.4 Interest accretion $ 1,643.2 $ 1,670.2 $ 1,727.7 Consolidated December 31 2023 2022 2021 (in millions of dollars, except weighted average data) Amount of undiscounted: Expected future benefit payments $ 105,325.8 $ 97,060.7 $ 98,574.9 Expected future gross premiums $ 38,761.5 $ 35,299.8 $ 35,296.0 Amount of discounted (at interest accretion rate): Expected future gross premiums $ 25,552.9 $ 23,827.2 $ 23,821.7 Weighted average interest rate: Interest accretion rate 4.8 % 4.8 % 4.8 % Current discount rate 4.8 % 5.0 % 2.5 % Weighted average duration of the liability 11.5 years 10.9 years 10.9 years Unum US Segment The following table presents the balances and changes in the reserves for future policy benefits for traditional long duration products in the Unum US segment. December 31, 2023 Group Disability Group Life and AD&D Voluntary Benefits Individual Disability Total Unum US (in millions of dollars) Present Value of Expected Net Premiums Balance, beginning of year $ — $ — $ 868.2 $ 1,202.9 $ 2,071.1 Beginning balance at original discount rate — — 937.9 1,228.1 2,166.0 Effect of changes in cash flow assumptions — — 180.7 5.0 185.7 Effect of actual variances from expected experience — — (79.8) (10.4) (90.2) Adjusted beginning of year balance — — 1,038.8 1,222.7 2,261.5 Issuances — — 288.6 197.9 486.5 Interest accretion — — 29.0 48.2 77.2 Net premiums collected — — (163.9) (174.4) (338.3) Ending balance at original discount rate — — 1,192.5 1,294.4 2,486.9 Effect of change in discount rate assumptions — — (57.8) 2.3 (55.5) Balance, end of period $ — $ — $ 1,134.7 $ 1,296.7 $ 2,431.4 Present Value of Expected Future Policy Benefits Balance, beginning of year $ 5,533.3 $ 972.6 $ 1,999.5 $ 3,192.8 $ 11,698.2 Beginning balance at original discount rate 5,793.1 998.5 2,141.2 3,244.5 12,177.3 Effect of changes in cash flow assumptions (100.2) — 170.1 7.9 77.8 Effect of actual variances from expected experience (204.0) (37.0) (90.9) (45.3) (377.2) Adjusted beginning of year balance 5,488.9 961.5 2,220.4 3,207.1 11,877.9 Issuances 1 1,094.5 394.2 303.7 215.3 2,007.7 Interest accretion 171.2 20.0 86.2 164.7 442.1 Benefit payments (1,477.5) (439.2) (188.3) (273.2) (2,378.2) Ending balance at original discount rate 5,277.1 936.5 2,422.0 3,313.9 11,949.5 Effect of change in discount rate assumptions (129.7) (14.5) (87.5) 34.7 (197.0) Balance, end of period $ 5,147.4 $ 922.0 $ 2,334.5 $ 3,348.6 $ 11,752.5 Net liability for future policy benefits $ 5,147.4 $ 922.0 $ 1,199.8 $ 2,051.9 $ 9,321.1 Other 0.2 1.0 2.6 27.8 31.6 Total liability for future policy benefits 5,147.6 923.0 1,202.4 2,079.7 9,352.7 Less: Reinsurance recoverable related to future policy benefits 30.7 7.2 14.0 156.7 208.6 Net liability for future policy benefits, after reinsurance recoverable $ 5,116.9 $ 915.8 $ 1,188.4 $ 1,923.0 $ 9,144.1 1 Issuances include new policy issuances for most product lines. Issuances for Unum US group disability and Unum US group life and AD&D represents new claim incurrals. December 31, 2022 Group Disability Group Life and AD&D Voluntary Benefits Individual Disability Total Unum US (in millions of dollars) Present Value of Expected Net Premiums Balance, beginning of year $ — $ — $ 1,124.8 $ 1,494.3 $ 2,619.1 Beginning balance at original discount rate — — 1,032.3 1,279.6 2,311.9 Effect of changes in cash flow assumptions — — (23.4) (73.7) (97.1) Effect of actual variances from expected experience — — (70.9) (25.2) (96.1) Adjusted beginning of year balance — — 938.0 1,180.7 2,118.7 Issuances — — 136.2 168.6 304.8 Interest accretion — — 29.1 49.8 78.9 Net premiums collected — — (165.4) (171.0) (336.4) Ending balance at original discount rate — — 937.9 1,228.1 2,166.0 Effect of change in discount rate assumptions — — (69.7) (25.2) (94.9) Balance, end of period $ — $ — $ 868.2 $ 1,202.9 $ 2,071.1 Present Value of Expected Future Policy Benefits Balance, beginning of year $ 6,725.7 $ 1,124.1 $ 2,697.3 $ 4,017.3 $ 14,564.4 Beginning balance at original discount rate 6,158.3 1,058.3 2,201.8 3,253.3 12,671.7 Effect of changes in cash flow assumptions (102.0) (32.9) (39.9) (53.4) (228.2) Effect of actual variances from expected experience (239.4) (34.3) (74.9) (36.0) (384.6) Adjusted beginning of year balance 5,816.9 991.1 2,087.0 3,163.9 12,058.9 Issuances 1 1,304.3 444.1 154.0 181.4 2,083.8 Interest accretion 210.5 24.5 86.1 155.3 476.4 Benefit payments (1,538.6) (461.2) (185.9) (256.1) (2,441.8) Ending balance at original discount rate 5,793.1 998.5 2,141.2 3,244.5 12,177.3 Effect of change in discount rate assumptions (259.8) (25.9) (141.7) (51.7) (479.1) Balance, end of period $ 5,533.3 $ 972.6 $ 1,999.5 $ 3,192.8 $ 11,698.2 Net liability for future policy benefits $ 5,533.3 $ 972.6 $ 1,131.3 $ 1,989.9 $ 9,627.1 Other 0.4 0.9 15.6 24.7 41.6 Total liability for future policy benefits 5,533.7 973.5 1,146.9 2,014.6 9,668.7 Less: Reinsurance recoverable related to future policy benefits 36.0 7.5 14.1 193.6 251.2 Net liability for future policy benefits, after reinsurance recoverable $ 5,497.7 $ 966.0 $ 1,132.8 $ 1,821.0 $ 9,417.5 1 Issuances include new policy issuances for most product lines. Issuances for Unum US group disability and Unum US group life and AD&D represents new claim incurrals. December 31, 2021 Group Disability Group Life and AD&D Voluntary Benefits Individual Disability Total Unum US (in millions of dollars) Present Value of Expected Net Premiums Balance, beginning of year $ — $ — $ 1,239.3 $ 1,514.2 $ 2,753.5 Beginning balance at original discount rate — — 1,146.9 1,208.8 $ 2,355.7 Effect of changes in cash flow assumptions — — (29.6) (18.9) $ (48.5) Effect of actual variances from expected experience — — (117.5) (10.4) $ (127.9) Adjusted beginning of year balance — — 999.8 1,179.5 $ 2,179.3 Issuances — — 196.5 211.3 $ 407.8 Interest accretion — — 38.3 57.9 $ 96.2 Net premiums collected — — (202.3) (169.1) $ (371.4) Ending balance at original discount rate — — 1,032.3 1,279.6 $ 2,311.9 Effect of change in discount rate assumptions — — 92.5 214.7 $ 307.2 Balance, end of period $ — $ — $ 1,124.8 $ 1,494.3 $ 2,619.1 Present Value of Expected Future Policy Benefits Balance, beginning of year $ 7,281.3 $ 1,126.3 $ 2,768.1 $ 4,226.9 $ 15,402.6 Beginning balance at original discount rate 6,369.4 1,034.4 2,272.6 3,197.6 12,874.0 Effect of changes in cash flow assumptions (186.0) — (40.3) (22.9) (249.2) Effect of actual variances from expected experience (229.3) 4.0 (136.5) (42.3) (404.1) Adjusted beginning of year balance 5,954.1 1,038.4 2,095.8 3,132.4 12,220.7 Issuances 1 1,471.4 467.5 220.6 222.5 2,382.0 Interest accretion 241.5 34.9 96.9 158.5 531.8 Benefit payments (1,508.7) (482.5) (211.5) (260.1) (2,462.8) Ending balance at original discount rate 6,158.3 1,058.3 2,201.8 3,253.3 12,671.7 Effect of change in discount rate assumptions 567.4 65.8 495.5 764.0 1,892.7 Balance, end of period $ 6,725.7 $ 1,124.1 $ 2,697.3 $ 4,017.3 $ 14,564.4 Net liability for future policy benefits $ 6,725.7 $ 1,124.1 $ 1,572.5 $ 2,523.0 $ 11,945.3 Other 0.5 1.2 14.0 59.0 74.7 Total liability for future policy benefits 6,726.2 1,125.3 1,586.5 2,582.0 12,020.0 Less: Reinsurance recoverable related to future policy benefits 40.9 4.4 31.2 231.9 308.4 Net liability for future policy benefits, after reinsurance recoverable $ 6,685.3 $ 1,120.9 $ 1,555.3 $ 2,350.1 $ 11,711.6 1 Issuances include new policy issuances for most product lines. Issuances for Unum US group disability and Unum US group life and AD&D represents new claim incurrals. The following tables summarize the amount of gross premiums and interest accretion reflected in the statements of income as well as the undiscounted and discounted expected gross premiums and expected future benefit payments and the weighted average interest rates for traditional long duration products in the Unum US segment presented in the rollforward activity above. Year Ended December 31, 2023 Group Disability Group Life and AD&D Voluntary Benefits Individual Disability Total Unum US (in millions of dollars) Amount recognized in the statement of income: Gross premiums or assessments $ 2,958.7 $ 1,878.0 $ 789.9 $ 636.6 $ 6,263.2 Interest accretion $ 171.2 $ 20.0 $ 57.2 $ 116.5 $ 364.9 Year Ended December 31, 2022 Group Disability Group Life and AD&D Voluntary Benefits Individual Disability Total Unum US (in millions of dollars) Amount recognized in the statement of income: Gross premiums or assessments $ 2,791.7 $ 1,864.9 $ 773.6 $ 591.5 $ 6,021.7 Interest accretion $ 210.5 $ 24.5 $ 57.0 $ 105.5 $ 397.5 Year Ended December 31, 2021 Group Disability Group Life and AD&D Voluntary Benefits Individual Disability Total Unum US (in millions of dollars) Amount recognized in the statement of income: Gross premiums or assessments $ 2,672.4 $ 1,827.5 $ 773.8 $ 580.1 $ 5,853.8 Interest accretion $ 241.5 $ 34.9 $ 58.6 $ 100.6 $ 435.6 December 31, 2023 Group Disability Group Life and AD&D Voluntary Benefits Individual Disability Total Unum US (in millions of dollars, except weighted average data) Amount of undiscounted: Expected future benefit payments $ 6,376.6 $ 1,063.2 $ 5,173.1 $ 5,313.7 $ 17,926.6 Expected future gross premiums $ — $ — $ 5,450.6 $ 5,724.8 $ 11,175.4 Amount of discounted (at interest accretion rate): Expected future gross premiums $ — $ — $ 3,717.5 $ 4,112.9 $ 7,830.4 Weighted average interest rate: Interest accretion rate 4.0 % 2.2 % 5.0 % 5.1 % 4.2% Current discount rate 4.6 % 2.6 % 4.9 % 4.8 % 4.5% Weighted average duration of the liability 4.3 years 2.6 years 18.1 years 9.6 years 7.0 years December 31, 2022 Group Disability Group Life and AD&D Voluntary Benefits Individual Disability Total Unum US (in millions of dollars, except weighted average data) Amount of undiscounted: Expected future benefit payments $ 6,988.1 $ 1,133.0 $ 4,561.1 $ 5,168.2 $ 17,850.4 Expected future gross premiums $ — $ — $ 3,979.6 $ 5,525.1 $ 9,504.7 Amount of discounted (at interest accretion rate): Expected future gross premiums $ — $ — $ 2,939.1 $ 3,962.1 $ 6,901.2 Weighted average interest rate: Interest accretion rate 3.8 % 2.2 % 5.1 % 5.1 % 4.0% Current discount rate 4.9 % 2.7 % 5.2 % 5.1 % 4.7% Weighted average duration of the liability 4.4 years 2.6 years 17.8 years 9.4 years 6.8 years December 31, 2021 Group Disability Group Life and AD&D Voluntary Benefits Individual Disability Total Unum US (in millions of dollars, except weighted average data) Amount of undiscounted: Expected future benefit payments $ 7,538.7 $ 1,224.7 $ 4,192.1 $ 5,210.6 $ 18,166.1 Expected future gross premiums $ — $ — $ 4,136.9 $ 5,597.3 $ 9,734.2 Amount of discounted (at interest accretion rate): Expected future gross premiums $ — $ — $ 3,156.5 $ 3,958.8 $ 7,115.3 Weighted average interest rate: Interest accretion rate 4.0 % 2.3 % 5.1 % 5.0 % 4.1% Current discount rate 2.1 % 1.3 % 2.8 % 2.4 % 2.1% Weighted average duration of the liability 4.5 years 2.9 years 15.8 years 9.5 years 6.5 years Unum International Segment The following table presents the balances and changes in the reserves for future policy benefits for traditional long duration products in the Unum International segment. December 31 2023 2022 2021 (in millions of dollars) Present Value of Expected Net Premiums Balance, beginning of year $ 197.1 $ 260.5 $ 311.7 Beginning balance at original discount rate 246.8 258.1 251.4 Effect of changes in cash flow assumptions (5.1) (0.3) — Effect of actual variances from expected experience 17.1 5.6 9.3 Adjusted beginning of year balance 258.8 263.4 260.7 Issuances 23.5 17.8 31.4 Interest accretion 9.4 8.4 8.9 Net premiums collected (23.0) (22.2) (22.6) Foreign currency 29.7 (20.6) (20.3) Ending balance at original discount rate 298.4 246.8 258.1 Effect of change in discount rate assumptions (28.1) (49.7) 2.4 Balance, end of period $ 270.3 $ 197.1 $ 260.5 Present Value of Expected Future Policy Benefits Balance, beginning of year $ 2,231.4 $ 3,181.8 $ 3,465.9 Beginning balance at original discount rate 2,495.5 2,703.8 2,644.5 Effect of changes in cash flow assumptions 17.7 (20.1) (5.5) Effect of actual variances from expected experience 1.3 46.3 15.9 Adjusted beginning of year balance 2,514.5 2,730.0 2,654.9 Issuances 1 335.2 327.7 391.6 Interest accretion 63.5 64.9 75.9 Benefit payments (388.3) (346.7) (360.3) Foreign currency 162.2 (280.4) (58.3) Ending balance at original discount rate 2,687.1 2,495.5 2,703.8 Effect of change in discount rate assumptions (159.7) (264.1) 478.0 Balance, end of period $ 2,527.4 $ 2,231.4 $ 3,181.8 Net liability for future policy benefits $ 2,257.1 $ 2,034.3 $ 2,921.3 Other 36.1 28.9 34.5 Total liability for future policy benefits 2,293.2 2,063.2 2,955.8 Less: Reinsurance recoverable related to future policy benefits 78.7 70.3 125.3 Net liability for future policy benefits, after reinsurance recoverable $ 2,214.5 $ 1,992.9 $ 2,830.5 1 Issuances for Unum International primarily represent new claim incurrals. The following tables summarize the amount of gross premiums and interest accretion reflected in the statements of income as well as the undiscounted and discounted expected gross premiums and expected future benefit payments and the weighted average interest rates for traditional long duration products in the Unum International segment presented in the rollforward activity above. Year Ended December 31 2023 2022 2021 (in millions of dollars) Amount recognized in the statement of income: Gross premiums or assessments $ 849.0 $ 786.8 $ 793.9 Interest accretion $ 54.1 $ 56.5 $ 67.0 December 31 2023 2022 2021 (in millions of dollars, except weighted average data) Amount of undiscounted: Expected future benefit payments $ 4,261.1 $ 3,905.4 $ 4,292.2 Expected future gross premiums $ 1,196.6 $ 943.9 $ 914.9 Amount of discounted (at interest accretion rate): Expected future gross premiums $ 778.6 $ 626.2 $ 620.8 Weighted average interest rate: Interest accretion rate 4.0 % 4.0 % 4.0 % Current discount rate 4.6 % 5.0 % 2.0 % Weighted average duration of the liability 8.6 years 8.6 years 8.8 years Colonial Life Segment The following table presents the balances and changes in the reserves for future policy benefits for traditional long duration products in the Colonial Life segment. December 31 2023 2022 2021 (in millions of dollars) Present Value of Expected Net Premiums Balance, beginning of year $ 3,745.4 $ 4,597.0 $ 4,671.9 Beginning balance at original discount rate 4,046.4 4,158.9 4,233.7 Effect of changes in cash flow assumptions (322.7) (32.3) (157.1) Effect of actual variances from expected experience (53.5) (145.6) (60.4) Adjusted beginning of year balance 3,670.2 3,981.0 4,016.2 Issuances 544.9 554.9 644.7 Interest accretion 122.7 129.7 156.2 Net premiums collected (583.5) (619.2) (658.2) Ending balance at original discount rate 3,754.3 4,046.4 4,158.9 Effect of change in discount rate assumptions (161.7) (301.0) 438.1 Balance, end of period $ 3,592.6 $ 3,745.4 $ 4,597.0 Present Value of Expected Future Policy Benefits Balance, beginning of year $ 5,581.1 $ 7,054.8 $ 7,022.9 Beginning balance at original discount rate 6,163.9 6,201.5 6,169.6 Effect of changes in cash flow assumptions (402.9) (85.9) (178.1) Effect of actual variances from expected experience (52.0) (191.3) (95.2) Adjusted beginning of year balance 5,709.0 5,924.3 5,896.3 Issuances 605.9 628.5 704.1 Interest accretion 211.3 217.0 243.1 Benefit payments (601.0) (605.9) (642.0) Ending balance at original discount rate 5,925.2 6,163.9 6,201.5 Effect of change in discount rate assumptions (359.2) (582.8) 853.3 Balance, end of period $ 5,566.0 $ 5,581.1 $ 7,054.8 Net liability for future policy benefits $ 1,973.4 $ 1,835.7 $ 2,457.8 Other 24.4 22.7 25.1 Total liability for future policy benefits 1,997.8 1,858.4 2,482.9 Less: Reinsurance recoverable related to future policy benefits 1.8 1.1 2.3 Net liability for future policy benefits, after reinsurance recoverable $ 1,996.0 $ 1,857.3 $ 2,480.6 The following tables summarize the amount of gross premiums and interest accretion reflected in the statements of income as well as the undiscounted and discounted expected gross premiums and expected future benefit payments and the weighted average interest rates for traditional long duration products in the Colonial Life segment presented in the rollforward activity above. Year Ended December 31 2023 2022 2021 (in millions of dollars) Amount recognized in the statement of income: Gross premiums or assessments $ 1,658.6 $ 1,635.8 $ 1,615.8 Interest accretion $ 88.6 $ 87.3 $ 86.9 December 31 2023 2022 2021 (in millions of dollars, except weighted average data) Amount of undiscounted: Expected future benefit payments $ 9,796.7 $ 10,011.9 $ 9,583.1 Expected future gross premiums $ 11,903.1 $ 12,221.3 $ 11,487.9 Amount of discounted (at interest accretion rate): Expected future gross premiums $ 8,702.2 $ 8,966.3 $ 8,566.7 Weighted average interest rate: Interest accretion rate 4.3 % 4.3 % 4.4 % Current discount rate 4.8 % 5.2 % 2.7 % Weighted average duration of the liability 17.0 years 17.5 years 16.4 years Closed Block Segment The following table presents the balances and changes in the reserves for future policy benefits for traditional long duration products in the Closed Block segment. December 31, 2023 Long-term Care All Other Total Closed Block (in millions of dollars) Present Value of Expected Net Premiums Balance, beginning of year $ 6,412.6 $ — $ 6,412.6 Beginning balance at original discount rate 6,236.1 — 6,236.1 Effect of changes in cash flow assumptions 1,641.3 — 1,641.3 Effect of actual variances from expected experience 44.1 — 44.1 Adjusted beginning of year balance 7,921.5 — 7,921.5 Interest accretion 374.7 — 374.7 Net premiums collected (592.6) — (592.6) Ending balance at original discount rate 7,703.6 — 7,703.6 Effect of change in discount rate assumptions 419.9 — 419.9 Balance, end of period $ 8,123.5 $ — $ 8,123.5 Present Value of Expected Future Policy Benefits Balance, beginning of year $ 21,199.9 $ 8,218.8 $ 29,418.7 Beginning balance at original discount rate 20,221.6 8,630.7 28,852.3 Effect of changes in cash flow assumptions 2,009.4 — 2,009.4 Effect of actual variances from expected experience 113.1 4.0 117.1 Adjusted beginning of year balance 22,344.1 8,634.7 30,978.8 Issuances 1 — 123.4 123.4 Interest accretion 1,151.4 358.9 1,510.3 Benefit payments (846.2) (1,022.4) (1,868.6) Ending balance at original discount rate 22,649.3 8,094.6 30,743.9 Effect of change in discount rate assumptions 2,048.4 (214.6) 1,833.8 Balance, end of period $ 24,697.7 $ 7,880.0 $ 32,577.7 Net liability for future policy benefits $ 16,574.2 $ 7,880.0 24,454.2 Other 2 23.1 1,638.1 1,661.2 Total liability for future policy benefits 16,597.3 9,518.1 26,115.4 Less: Reinsurance recoverable related to future policy benefits 4.5 7,462.4 7,466.9 Net liability for future policy benefits, after reinsurance recoverable $ 16,592.8 $ 2,055.7 $ 18,648.5 1 Issuances for Closed Block - All Other represents new claim incurrals. 2 Other for Closed Block - All Other primarily includes our closed block group pension products and certain of our ceded closed block individual life products. December 31, 2022 Long-term Care All Other Total Closed Block (in millions of dollars) Present Value of Expected Net Premiums Balance, beginning of year $ 8,404.7 $ — $ 8,404.7 Beginning balance at original discount rate 6,457.3 — 6,457.3 Effect of changes in cash flow assumptions 27.8 — 27.8 Effect of actual variances from expected experience (33.5) — (33.5) Adjusted beginning of year balance 6,451.6 — 6,451.6 Interest accretion 349.0 — 349.0 Net premiums collected (564.5) — (564.5) Ending balance at original discount rate 6,236.1 — 6,236.1 Effect of change in discount rate assumptions 176.5 — 176.5 Balance, end of period $ 6,412.6 $ — $ 6,412.6 Present Value of Expected Future Policy Benefits Balance, beginning of year $ 30,089.6 $ 10,414.4 $ 40,504.0 Beginning balance at original discount rate 19,870.8 8,949.4 28,820.2 Effect of changes in cash flow assumptions 24.9 216.9 241.8 Effect of actual variances from expected experience (36.2) 30.7 (5.5) Adjusted beginning of year balance 19,859.5 9,197.0 29,056.5 Issuances 1 — 154.5 154.5 Interest accretion 1,105.1 372.8 1,477.9 Benefit payments (743.0) (1,093.6) (1,836.6) Ending balance at original discount rate 20,221.6 8,630.7 28,852.3 Effect of change in discount rate assumptions 978.3 (411.9) 566.4 Balance, end of period $ 21,199.9 $ 8,218.8 $ 29,418.7 Net liability for future policy benefits $ 14,787.3 $ 8,218.8 $ 23,006.1 Other 2 24.3 1,737.0 1,761.3 Total liability for future policy benefits 14,811.6 9,955.8 24,767.4 Less: Reinsurance recoverable related to future policy benefits 5.7 7,799.8 7,805.5 Net liability for future policy benefits, after reinsurance recoverable $ 14,805.9 $ 2,156.0 $ 16,961.9 1 Issuances for Closed Block - All Other represents new claim incurrals. 2 Other for Closed Block - All Other primarily includes our closed block group pension products and certain of our ceded closed block individual life products. December 31, 2021 Long-term Care All Other Total Closed Block (in millions of dollars) Present Value of Expected Net Premiums Balance, beginning of year $ 9,358.8 $ — $ 9,358.8 Beginning balance at original discount rate 6,782.7 — 6,782.7 Effect of changes in cash flow assumptions 28.5 — 28.5 Effect of actual variances from expected experience (149.3) — (149.3) Adjusted beginning of year balance 6,661.9 — 6,661.9 Interest accretion 370.6 — 370.6 Net premiums collected (575.2) — (575.2) Ending balance at original discount rate 6,457.3 — 6,457.3 Effect of change in discount rate assumptions 1,947.4 — 1,947.4 Balance, end of period $ 8,404.7 $ — $ 8,404.7 Present Value of Expected Future Policy Benefits Balance, beginning of year $ 32,047.2 $ 11,591.9 $ 43,639.1 Beginning balance at original discount rate 19,549.7 9,514.6 29,064.3 Effect of changes in cash flow assumptions 52.9 — 52.9 Effect of actual variances from expected experience (170.8) 18.3 (152.5) Adjusted
Deferred Policy Acquisition Costs by Segment	The following tables display the changes in DAC throughout the year: December 31, 2023 Unum US Unum International Colonial Life Total (in millions of dollars) Balance, beginning of year $ 1,185.1 $ 37.0 $ 1,337.9 $ 2,560.0 Capitalization 314.7 14.6 302.9 632.2 Amortization expense (267.6) (8.4) (205.4) (481.4) Foreign currency — 3.7 — 3.7 Balance, end of year $ 1,232.2 $ 46.9 $ 1,435.4 $ 2,714.5 December 31, 2022 Unum US Unum International Colonial Life Total (in millions of dollars) Balance, beginning of year $ 1,152.9 $ 36.4 $ 1,238.1 $ 2,427.4 Capitalization 273.1 12.0 271.8 556.9 Amortization expense (240.9) (8.2) (172.0) (421.1) Foreign currency — (3.2) — (3.2) Balance, end of year $ 1,185.1 $ 37.0 $ 1,337.9 $ 2,560.0 December 31, 2021 Unum US Unum International Colonial Life Total (in millions of dollars) Balance, beginning of year $ 1,181.0 $ 32.0 $ 1,144.7 $ 2,357.7 Capitalization 257.8 12.8 252.6 523.2 Amortization expense (285.9) (7.0) (159.2) (452.1) Foreign currency — (1.4) — (1.4) Balance, end of year $ 1,152.9 $ 36.4 $ 1,238.1 $ 2,427.4 December 31, 2023 Group Disability Group Life and AD&D Voluntary Benefits Individual Disability Dental and Vision Total Unum US (in millions of dollars) Balance, beginning of year $ 61.0 $ 49.3 $ 601.0 $ 464.4 $ 9.4 $ 1,185.1 Capitalization 60.2 38.6 115.8 87.4 12.7 314.7 Amortization expense (57.6) (39.0) (106.2) (54.0) (10.8) (267.6) Balance, end of year $ 63.6 $ 48.9 $ 610.6 $ 497.8 $ 11.3 $ 1,232.2 December 31, 2022 Group Disability Group Life and AD&D Voluntary Benefits Individual Disability Dental and Vision Total Unum US (in millions of dollars) Balance, beginning of year $ 60.9 $ 53.9 $ 588.6 $ 441.8 $ 7.7 $ 1,152.9 Capitalization 53.1 37.3 100.0 72.0 10.7 273.1 Amortization expense (53.0) (41.9) (87.6) (49.4) (9.0) (240.9) Balance, end of year $ 61.0 $ 49.3 $ 601.0 $ 464.4 $ 9.4 $ 1,185.1 December 31, 2021 Group Disability Group Life and AD&D Voluntary Benefits Individual Disability Dental and Vision Total Unum US (in millions of dollars) Balance, beginning of year $ 95.3 $ 76.4 $ 569.7 $ 423.6 $ 16.0 $ 1,181.0 Capitalization 49.8 36.1 99.4 63.9 8.6 257.8 Amortization expense (84.2) (58.6) (80.5) (45.7) (16.9) (285.9) Balance, end of year $ 60.9 $ 53.9 $ 588.6 $ 441.8 $ 7.7 $ 1,152.9 During the third quarter of 2023, we updated our policyholder lapse and mortality assumptions used to develop the future amortization for DAC for the Unum US voluntary benefits product line and the Colonial Life segment. During the third quarter of 2022 and 2021, we updated our policyholder lapse and mortality assumptions used to develop the future amortization for DAC for the Unum US individual disability and voluntary benefits product lines as well as for the Colonial Life segment. These assumption updates were consistent with the related assumption updates for the liability for future policy benefits.

Income Tax

Income Tax	12 Months Ended
	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Income Tax Disclosure	Total income tax expense (benefit) is allocated as follows: Year Ended December 31 2023 2022 2021 (in millions of dollars) Net Income $ 356.3 $ 342.8 $ 279.6 Stockholders' Equity - Accumulated Other Comprehensive Income (Loss) Change in Net Unrealized Gain (Loss) on Securities 300.6 (1,890.8) (346.9) Change in the Effect of Discount Rate Assumptions on the Liability for Future Policy and Contract Benefits, Net of Reinsurance (256.5) 2,385.1 622.8 Change in Net Gain (Loss) on Hedges (17.0) (19.2) (9.8) Change in Foreign Currency Translation Adjustment 0.9 (0.1) 4.2 Change in Unrecognized Pension and Postretirement Benefit Costs (2.7) 18.9 42.1 Total $ 381.6 $ 836.7 $ 592.0 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 2023 2022 2021 Statutory Income Tax 21.0 % 21.0 % 21.0 % Policyholder Reserves (0.6) (1.7) 2.0 Other Items, Net 1.3 0.3 (0.8) Effective Tax 21.7 % 19.6 % 22.2 % Our net deferred tax asset consists of the following. December 31 2023 2022 (in millions of dollars) Deferred Tax Asset Invested Assets $ 354.5 $ 664.9 Reserves 462.6 116.4 Employee Benefits 161.9 158.3 Other 35.8 34.4 Gross Deferred Tax Asset 1,014.8 974.0 Less: Valuation Allowance 11.0 10.3 Net Deferred Tax Asset 1,003.8 963.7 Deferred Tax Liability Deferred Acquisition Costs 175.1 177.7 Fixed Assets 36.7 48.9 Cost of Reinsurance 119.7 131.6 Other 49.9 44.7 Gross Deferred Tax Liability 381.4 402.9 Net Deferred Tax Asset $ 622.4 $ 560.8 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 2023 2022 2021 (in millions of dollars) Income Before Tax Domestic $ 1,506.2 $ 1,596.8 $ 1,150.5 Foreign 133.9 153.2 110.1 Total $ 1,640.1 $ 1,750.0 $ 1,260.6 Current Tax Expense (Benefit) Federal $ 440.4 $ 306.5 $ 180.7 State and Local (2.5) 12.7 2.6 Foreign 14.1 154.3 29.5 Total 452.0 473.5 212.8 Deferred Tax Expense (Benefit) Federal (106.2) 42.7 54.0 State and Local (1.5) 1.1 (2.2) Foreign 12.0 (174.5) 15.0 Total (95.7) (130.7) 66.8 Total Tax Expense $ 356.3 $ 342.8 $ 279.6 On June 10, 2021, the Finance Act 2021 was enacted, resulting in a U.K. tax increase from 19 percent to 25 percent, effective April 1, 2023, which resulted in $23.6 million of additional tax expense in operating earnings for the revaluation of our deferred tax assets and liabilities in 2021. As of December 31, 2023, our plans for 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. Our consolidated statements of income include the following changes in unrecognized tax benefits. December 31 2023 2022 2021 (in millions of dollars) Balance at Beginning of Year $ 177.4 $ 198.8 $ 219.7 Decreases for Tax Positions Related to Prior Years (20.7) (21.0) (20.9) Lapse of the Applicable Statute of Limitations — (0.4) — Balance at End of Year 156.7 177.4 198.8 Less Tax Attributable to Temporary Items Included Above (42.4) (63.5) (84.7) Total Unrecognized Tax Benefits That if Recognized Would Affect the Effective Tax Rate $ 114.3 $ 113.9 $ 114.1 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 $42.4 million at December 31, 2023, $63.5 million at December 31, 2022, and $84.7 million at December 31, 2021. 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 $12.2 million, $7.8 million, and $5.5 million of interest expense related to unrecognized tax benefits during 2023, 2022, and 2021, respectively. The liability for net interest expense on uncertain tax positions was approximately $46.2 million, $34.0 million, and $26.2 million as of December 31, 2023, 2022, and 2021, respectively. We file federal and state income tax returns in the United States and in foreign jurisdictions. Tax years 2013, 2016, 2017 and tax years subsequent to 2018 remain subject to examination by the IRS. All major foreign jurisdictions remain subject to examination for tax years subsequent to 2021 with the exception of Poland for which tax years subsequent to 2017 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 2017 remain subject to examination depending on the statute of limitation established by the various states, which is generally three to four years. As of December 31, 2023, we have no federal net operating loss or capital loss carryforwards. We have net operating loss carryforwards for state and local income tax of approximately $183.9 million, most of which is expected to expire unused between 2024 and 2043. 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 $11.0 million and $10.3 million at December 31, 2023 and 2022, respectively, 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 an increase in our valuation allowance of $0.7 million during 2023 and a decrease of $2.4 million in 2022, primarily in other comprehensive income. Total income taxes paid during 2023 and 2022 were $446.0 million and $375.0 million, respectively. Total income taxes refunded during 2021 were $51.0 million.

Debt

Debt	12 Months Ended
	Dec. 31, 2023
Debt Disclosure [Abstract]
Debt	Debt consists of the following: December 31 2023 2022 Interest Rates Maturities (in millions of dollars) 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 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 2021 4.125% 2051 600.0 600.0 Medium-term Notes issued 1990 - 1996 7.190% 2028 18.5 18.5 Junior Subordinated Debt Securities issued 1998 7.405% 2038 189.7 189.7 Junior Subordinated Debt Securities issued 2018 6.250% 2058 300.0 300.0 Term Loan issued 2022 Variable 2027 350.0 350.0 Less: Unamortized Net Premium 2.5 2.5 Unamortized Debt Issuance Costs (30.6) (33.2) Total Long-term Debt $ 3,430.4 $ 3,427.8 Short-term Debt Medium-term Notes Issued 1990 7.000% 2023 — 2.0 Total Debt $ 3,430.4 $ 3,429.8 Long-term debt is comprised of our unsecured notes, which consist of our senior notes, medium-term notes, and term loan facility, and rank highest in priority, followed by our junior subordinated debt securities. The senior notes are callable and may be redeemed, in whole or in part, at any time. The term loan facility is callable and may be redeemed at par at any time. The medium-term notes are non-callable and the junior subordinated debt securities are callable under limited, specified circumstances. The aggregate contractual principal maturities are $275.0 million in 2025, $350.0 million in 2027, $354.3 million in 2028, and $2,479.2 million thereafter. Unsecured Notes In August 2022, we redeemed $350.0 million aggregate principal amount of our 4.000% senior notes due 2024, for which we incurred costs of $3.0 million. In June 2021, we issued $600.0 million of 4.125% senior notes due 2051. 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 2021, we purchased and retired $500.0 million of 4.500% senior notes due 2025, for which we incurred costs of $67.3 million and has been recorded within cost related to the early retirement of debt in the consolidated statements of income and is included within our Corporate segment. Term Loan Facility In August 2022, we entered into a five-year $350.0 million senior unsecured delayed draw term loan facility with a syndicate of lenders. Also in August 2022, we drew the entire amount of the term loan facility, which is scheduled to mature in August 2027. Amounts due under the term loan facility incur interest based on the prime rate, the federal funds rate, or the Secured Overnight Financing Rate (SOFR). The proceeds from the term loan facility were used to redeem $350.0 million aggregate principal amount of our 4.000% senior notes due 2024. Borrowings under the term loan facility 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. 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. In September 2022, pursuant to privately negotiated transactions, we purchased, and the Trust retired, $14.0 million aggregate liquidation amount of the Trust's 7.405% capital securities due 2038, which resulted in the reduction of a corresponding principal amount of our 7.405% junior subordinated debt securities due 2038 then held by the Trust. We incurred costs of $1.2 million related to the early retirement of the junior subordinated debt securities. Interest Paid Interest paid on long-term and short-term debt and related securities during 2023, 2022, and 2021 was $183.6 million, $172.9 million, and $181.6 million, respectively. Facility Agreement for Contingent Issuance of Senior Notes During November 2021, we entered into a 20-year facility agreement with a Delaware trust (the P-Caps Trust) in connection with the sale by the trust of $400.0 million of pre-capitalized trust securities in a Rule 144A private placement. The trust invested the proceeds from the sale of the trust securities in a portfolio of principal and interest strips of U.S. Treasury securities. The facility agreement provides us the right to issue and sell to the trust, on one or more occasions, up to an aggregate principal amount outstanding at any one time of $400.0 million of our 4.046% senior notes which would be due August 15, 2041 in exchange for U.S. Treasury securities held by the trust. These senior notes will not be issued unless and until the issuance right is exercised. The exercise of the issuance right triggers recognition of the senior notes on our consolidated balance sheets. As the amount we receive upon exercise of the issuance right is contingent upon the value of the U.S. Treasury securities, a decline in the value of the U.S. Treasury securities reduces the amount we would receive upon exercise of the issuance right. In return, we will pay a semi-annual facility fee to the trust at a rate of 2.225% per year on the unexercised portion of the maximum amount of senior notes that we could issue and sell to the trust and we will reimburse the trust for its expenses. We may also direct the trust to grant the right to exercise the issuance right with respect to all or a designated amount of the senior notes to one or more assignees (who are our consolidated subsidiaries or persons to whom we have an obligation). The issuance right will be exercised automatically in full upon our failure to make certain payments to the trust, such as paying the facility fee or reimbursing the trust for its expenses, if the failure to pay is not cured within 30 days, or upon certain bankruptcy events involving the company. We are also required to exercise the issuance right in full if our consolidated stockholders’ equity, excluding accumulated other comprehensive income, falls below $2.0 billion, subject to adjustment from time to time in certain cases, and upon certain other events described in the facility agreement. Prior to any involuntary exercise of the issuance right, we have the right to repurchase any or all of the 4.046% senior notes then held by the trust in exchange for U.S. Treasury securities. We may redeem any outstanding 4.046% senior notes, in whole or in part, prior to their maturity. Prior to February 15, 2041, the redemption price will equal the greater of par or a make-whole redemption price. On or after February 15, 2041, any outstanding 4.046% senior notes may be redeemed at par. Credit Facilities In April 2022, we amended and restated our existing credit agreement providing for a five-year $500.0 million senior unsecured revolving credit facility with a syndicate of lenders. The credit facility, which was previously set to expire in April 2024, was extended through April 2027. We may request that the lenders’ aggregate commitments of $500.0 million under the facility be increased by up to an additional $200.0 million. Certain of our traditional U.S. life insurance subsidiaries, Unum Life Insurance Company of America (Unum America), Provident Life and Accident Insurance Company (Provident), and Colonial Life & Accident Insurance Company, joined the agreement and may borrow under the credit facility, and we can elect to add additional insurance subsidiaries to the facility at any later date. Any obligation of a subsidiary under the credit facility is several only and not joint and is subject to an unconditional guarantee by Unum Group. We may also request, on up to two occasions, that the lenders' commitment termination dates be extended by one year. The credit facility also provides for the issuance of letters of credit subject to certain terms and limitations. The credit facility provides for borrowings at an interest rate based on the prime rate, the federal funds rate or the SOFR. At December 31, 2023, there were no borrowed amounts outstanding under the credit facility and letters of credit totaling $0.4 million had been issued. In the third quarter of 2021, we terminated our three-year, $100.0 million unsecured revolving credit facility, which was originally set to expire in April 2022. There were no letters of credit issued from the credit facility and there were no borrowed amounts outstanding at the time of termination. Also in the third quarter of 2021, we entered into a new five-year, £75.0 million senior unsecured standby letter of credit facility with the same syndicate of lenders, pursuant to which a syndicated letter of credit was issued in favor of Unum Limited (as beneficiary), our U.K. insurance subsidiary, and is available for drawings up to £75 million until its scheduled expiration in July 2026. The credit facility provides for borrowings at an interest rate based on the prime rate or the federal funds rate. In December 2023, we entered into a new five-year, £75 million senior standby letter of credit facility pursuant to which a standby letter of credit was issued in favor of Unum Limited (as beneficiary), our U.K. insurance subsidiary, and is available for drawings up to £75.0 million until its scheduled expiration in December 2028. In connection with and as security for the December 2023 senior standby letter of credit facility, we granted to the issuer of the standby letter of credit the right to exercise, if an event of default has occurred and is continuing, the issuance right in our 20-year facility agreement with the P-Caps Trust, up to a maximum of $200.0 million. The credit facility provides for borrowings at an interest rate based on Sterling Overnight Index Average rate. At December 31, 2023, there were no borrowed amounts outstanding under the credit facilities or letters of credit. If drawings are made in the future, we may elect to borrow such amounts from the lenders pursuant to term loans made under the credit facilities.

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2023
Retirement Benefits [Abstract]
Pension and Other Postretirement Benefits Disclosure	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 Purchase In November 2023, 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 1,275 retirees or their beneficiaries receiving less than $700 in monthly benefit payments from the plan. This transfer resulted in a reduction in our U.S. qualified defined benefit pension plan obligation of approximately $72 million 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 gain or loss and prior service credit or cost for these plans over the average remaining life expectancy of the plans. As of December 31, 2023, the estimate of the average remaining life expectancy of the plans was approximately 24 years for the U.S. plans and 27 years for the U.K. plan. During 2023, we amortized the net actuarial gain or loss and prior service credit or cost for the OPEB plan over the average remaining future working lifetime for active participants in the plan. Beginning in 2024, as substantially all of our participants in our OPEB plan will be considered inactive, we will begin to amortize over the average remaining life expectancy of the plan which is estimated to be 12 years. 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 2023 2022 2023 2022 2023 2022 (in millions of dollars) Change in Benefit Obligation Benefit Obligation at Beginning of Year $ 1,585.5 $ 2,207.5 $ 157.9 $ 278.3 $ 83.9 $ 110.3 Service Cost 9.2 7.7 — — — — Interest Cost 87.9 67.2 7.7 5.0 4.5 3.0 Plan Participant Contributions — — — — 0.1 0.1 Actuarial Loss (Gain) (1) 61.0 (604.1) 3.8 (92.4) (0.5) (19.4) Benefits and Expenses Paid (168.3) (92.8) (5.7) (5.4) (9.0) (10.1) Change in Foreign Exchange Rates — — 8.6 (27.6) — — Benefit Obligation at End of Year $ 1,575.3 $ 1,585.5 $ 172.3 $ 157.9 $ 79.0 $ 83.9 Accumulated Benefit Obligation at December 31 $ 1,575.3 $ 1,585.5 $ 172.3 $ 158.0 N/A N/A Change in Fair Value of Plan Assets Fair Value of Plan Assets at Beginning of Year $ 1,308.3 $ 1,801.7 $ 140.5 $ 303.7 $ 8.5 $ 9.0 Actual Return on Plan Assets 145.6 (410.6) 3.1 (128.4) — 0.1 Employer Contributions 10.3 10.0 — — 8.6 9.4 Plan Participant Contributions — — — — 0.1 0.1 Benefits and Expenses Paid (168.3) (92.8) (5.7) (5.4) (9.0) (10.1) Change in Foreign Exchange Rates — — 7.5 (29.4) — — Fair Value of Plan Assets at End of Year $ 1,295.9 $ 1,308.3 $ 145.4 $ 140.5 $ 8.2 $ 8.5 Underfunded Status $ 279.4 $ 277.2 $ 26.9 $ 17.4 $ 70.8 $ 75.4 (1) The actuarial losses recognized in 2023 for the U.S. and U.K. plans were driven by decreases in the discount rate assumption. Also contributing to the actuarial loss for the U.K. plan in 2023 was unfavorable plan experience resulting from a higher than expected rate of inflation. The actuarial gain recognized in 2023 for the OPEB plan was driven by favorable plan experience mostly offset by a decrease in the assumed discount rate. The actuarial gains recognized in 2022 for the U.S., OPEB, and U.K. plans were primarily driven by increases in the discount rate assumption. The amounts recognized in our consolidated balance sheets for our pension and OPEB plans at December 31, 2023 and 2022 are as follows. Pension Benefits U.S. Plans U.K. Plan OPEB 2023 2022 2023 2022 2023 2022 (in millions of dollars) Current Liability $ 9.1 $ 8.8 $ — $ — $ 0.7 $ 1.1 Noncurrent Liability 270.3 268.4 26.9 17.4 70.1 74.3 Underfunded Status $ 279.4 $ 277.2 $ 26.9 $ 17.4 $ 70.8 $ 75.4 Unrecognized Pension and Postretirement Benefit Costs Net Actuarial Gain (Loss) $ (510.2) $ (517.8) $ (95.0) $ (83.7) $ 21.2 $ 31.6 Prior Service Credit (Cost) (0.6) (0.6) (0.2) (0.2) 2.3 2.5 (510.8) (518.4) (95.2) (83.9) 23.5 34.1 Income Tax 211.2 213.5 22.2 19.5 3.4 1.1 Total Included in Accumulated Other Comprehensive Income (Loss) $ (299.6) $ (304.9) $ (73.0) $ (64.4) $ 26.9 $ 35.2 The following table provides the changes recognized in other comprehensive income for the years ended December 31, 2023 and 2022. Pension Benefits U.S. Plans U.K. Plan OPEB 2023 2022 2023 2022 2023 2022 (in millions of dollars) Accumulated Other Comprehensive Income (Loss) at Beginning of Year $ (304.9) $ (383.2) $ (64.4) $ (34.0) $ 35.2 $ 21.2 Net Actuarial Gain (Loss) Amortization 15.2 16.3 2.5 0.4 (10.5) (1.0) All Other Changes (7.6) 87.7 (13.8) (41.2) 0.1 19.0 Prior Service Credit (Cost) Amortization — — — — (0.2) (0.2) Change in Income Tax (2.3) (25.7) 2.7 10.4 2.3 (3.8) Accumulated Other Comprehensive Income (Loss) at End of Year $ (299.6) $ (304.9) $ (73.0) $ (64.4) $ 26.9 $ 35.2 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 funds and U.S. government and agency asset-backed securities, treasury futures contracts, 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 and private equity 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 38 percent to equity securities, 30 percent to fixed income securities, and 32 percent to opportunistic credits, alternative, and real estate investments. Asset Class Asset Type Benchmark Indices Equity Securities Collective funds; Individual holdings Morgan Stanley Capital International (MSCI) World Index Fixed Income Collective funds; Individual holdings Bloomberg Barclays Long Corporate Index; Custom Index Opportunistic Credits Collective fund Custom Index Real Estate Collective fund Custom Index Alternative Investments (Private Equity) Fund of funds; Direct investments Custom Index The investment strategy for our U.K. plan includes increasing the funded ratio in a risk-controlled manner where the risk taken in the investment strategy reduces as the funded status of the plan increases. Assets for our U.K. plan are invested in a portfolio of diversified growth assets as well as a portfolio of fixed income and index-linked securities. The portfolio of growth assets consists of funds invested primarily in global equity securities, investment-grade and below-investment-grade fixed interest securities, including emerging market securities as well as diversified alternatives. The portfolio of fixed interest and index-linked securities are invested primarily in leveraged interest rate and inflation-linked gilt funds of varying durations designed to broadly match the interest rate and inflation sensitivities of the plan's liabilities. At December 31, 2023, our target allocation was approximately 48 percent to growth assets and 52 percent to fixed interest and index-linked securities. When the funded status of the plan increases, we utilize a de-risking framework whereby the allocation to fixed interest and index-linked securities increases and the allocation to growth assets is lowered. Simultaneously, the hedge ratio of interest rate and inflation risk will increase with the intention of reducing funding level volatility. 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. 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 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, 2023 Quoted Prices Significant Other Significant NAV as a Practical Total (in millions of dollars) Invested Assets Equity Securities: Global $ 55.0 $ — $ — $ 390.8 $ 445.8 Fixed Income Securities: U.S. Government and Agencies 1 215.9 40.8 — — 256.7 Corporate — — — 130.0 130.0 Non-U.S. Emerging Markets — — — 27.9 27.9 Opportunistic Credits — — — 150.6 150.6 Real Estate — — — 162.8 162.8 Alternative Investments: Private Equity Direct Investments — — — 68.5 68.5 Private Equity Funds of Funds — — — 40.7 40.7 Cash Equivalents 16.0 — — — 16.0 Total Invested Assets $ 286.9 $ 40.8 $ — $ 971.3 $ 1,299.0 1 U.S. Government and Agencies Fixed Income Securities includes derivative assets. December 31, 2022 Quoted Prices Significant Significant NAV as a Practical Total (in millions of dollars) Invested Assets Equity Securities: Global $ 57.4 $ — $ — $ 405.7 $ 463.1 Fixed Income Securities: U.S. Government and Agencies 1 194.0 21.7 — — 215.7 Corporate — — — 129.6 129.6 Non-U.S. Emerging Markets — — — 54.0 54.0 Opportunistic Credits — — — 132.3 132.3 Real Estate — — — 164.2 164.2 Alternative Investments: Private Equity Direct Investments — — — 74.5 74.5 Private Equity Funds of Funds — — — 47.6 47.6 Cash Equivalents 20.5 — — — 20.5 Total Invested Assets $ 271.9 $ 21.7 $ — $ 1,007.9 $ 1,301.5 1 U.S. Government and Agencies Fixed Income Securities includes derivative assets. 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 either directly or indirectly observable inputs other than quoted prices from active markets. Certain equity, opportunistic credit, and fixed-income securities are valued based on the NAV of the underlying holdings as of the reporting date. We made no adjustments to the NAV for 2023 or 2022. These investments have no unfunded commitments and no specific redemption restrictions. Alternative investments are valued based on NAV one quarter in arrears and our real estate investments are valued based on NAV one month 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 2023 or 2022. 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. 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, 2023 Quoted Prices Significant Significant NAV as a Practical Total (in millions of dollars) Invested Assets Diversified Growth Assets $ 28.1 $ — $ — $ 5.9 $ 34.0 Fixed Income and Index-linked Securities 75.3 — — — 75.3 Alternative Investments — — — 34.8 34.8 Cash Equivalents 1.3 — — — 1.3 Total Invested Assets $ 104.7 $ — $ — $ 40.7 $ 145.4 December 31, 2022 Quoted Prices Significant Significant NAV as a Practical Total (in millions of dollars) Invested Assets Diversified Growth Assets $ 32.3 $ — $ — $ 8.3 $ 40.6 Fixed Income and Index-linked Securities 70.6 — — — 70.6 Alternative Investments — — — 28.1 28.1 Cash Equivalents 1.9 — — — 1.9 Total Invested Assets $ 104.8 $ — $ — $ 36.4 $ 141.2 The level 1 diversified growth assets and fixed interest and index-linked securities consist of individual funds that are valued based on unadjusted quoted prices from active markets for identical securities. Certain diversified growth assets were valued based on the NAV of the underlying holdings as of the reporting date. Alternative investments are valued based on NAV one quarter in arrears. We evaluate the need for adjustments to the NAV of the alternative investments based on an evaluation of cash flows in the period subsequent to the valuation date and prior to issuance of the financial statements. We made no adjustments to the NAV for 2023 or 2022. These investments generally cannot be redeemed by investors. These investments had unfunded commitments at December 31, 2023 and 2022 of $9.9 million and $17.3 million, respectively. The categorization of fair value measurements by input level for the assets in our OPEB plan is as follows: December 31, 2023 Quoted Prices Significant Other Significant Total (in millions of dollars) Assets Life Insurance Contracts $ — $ — $ 8.2 $ 8.2 December 31, 2022 Quoted Prices Significant Other Significant Total (in millions of dollars) Assets Life Insurance Contracts $ — $ — $ 8.5 $ 8.5 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, 2023 and 2022 are as follows: Year Ended December 31, 2023 Beginning Actual Return on Plan Assets Contributions Net Benefits and Expenses Paid End of Year (in millions of dollars) Life Insurance Contracts $ 8.5 $ — $ 8.7 $ (9.0) $ 8.2 Year Ended December 31, 2022 Beginning Actual Return on Plan Assets Contributions Net Benefits and Expenses Paid End of Year (in millions of dollars) Life Insurance Contracts $ 9.0 $ 0.1 $ 9.5 $ (10.1) $ 8.5 For the years ended December 31, 2023 and 2022, 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 2023 or 2022. 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 2023 2022 2023 2022 2023 2022 Benefit Obligations Discount Rate 5.40 % 5.70 % 4.50 % 4.80 % 5.40 % 5.70 % Rate of Compensation Increase N/A N/A 2.40 % 2.50 % N/A N/A Net Periodic Benefit Cost Discount Rate 5.70 % 3.10 % 4.80 % 2.00 % 5.70 % 2.90 % Expected Return on Plan Assets 7.25 % 6.00 % 6.70 % 4.20 % 5.75 % 5.75 % Rate of Compensation Increase N/A N/A 2.50 % 2.90 % 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 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 4.46 percent and 4.31 percent in 2023 and 2022, respectively. The rate of compensation increase assumption for our U.K. plan is generally based on periodic studies of compensation trends. At December 31, 2023 and 2022, the annual rates of increase in the per capita cost of covered postretirement health care benefits assumed for the next calendar year are 6.75 percent and 7.00 percent, respectively, 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 2031 for measurement at December 31, 2023 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 2023 2022 2021 2023 2022 2021 2023 2022 2021 (in millions of dollars) Service Cost $ 9.2 $ 7.7 $ 9.6 $ — $ — $ — $ — $ — $ — Interest Cost 87.9 67.2 65.0 7.7 5.0 4.2 4.5 3.0 3.0 Expected Return on Plan Assets (92.0) (105.9) (100.6) (8.5) (10.9) (9.8) (0.5) (0.5) (0.5) Amortization of: Net Actuarial Loss (Gain) 15.2 16.3 21.3 2.5 0.4 1.3 (10.5) (1.0) — Prior Service Credit — — — — — — (0.2) (0.2) (0.2) Total Net Periodic Benefit Cost (Credit) $ 20.3 $ (14.7) $ (4.7) $ 1.7 $ (5.5) $ (4.3) $ (6.7) $ 1.3 $ 2.3 The service cost component of net periodic pension and postretirement benefit cost (credit) is included as a component of compensation expense in our consolidated statements of income. All other components of net periodic pension and postretirement benefit cost (credit) 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 2024 $ 83.5 $ 6.7 $ 9.1 $ — $ 9.1 2025 87.0 7.1 8.7 — 8.7 2026 91.2 7.7 8.3 — 8.3 2027 95.1 8.2 8.0 — 8.0 2028 98.8 8.5 7.6 — 7.6 2029-2033 533.2 47.0 31.9 0.1 31.8 Funding Policy The funding policy for our U.S. qualified defined benefit pension plan is to contribute an amount at least equal to the minimum contributions 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 pension plan in 2023 and made no amount of voluntary contributions during 2023. We do not expect to have regulatory contribution requirements for our U.S. qualified defined benefit pension plan in 2024, but we reserve the right to make voluntary contributions during 2024. The funding policy for our U.S. non-qualified defined benefit pension plan, which is not subject to ERISA, is to contribute the amount necessary to satisfy the liabilities of the plan as they come due to participants. We expect to make contributions to the U.S. non-qualified defined benefit pension plan of approximately $9 million to fund the benefit payments in 2024. We had no regulatory contribution requirements for our U.K. defined benefit pension plan in 2023 and made no amount of voluntary contributions during 2023. We do not expect to have regulatory contribution requirements for our U.K. defined benefit pension plan in 2024, but we reserve the right to make voluntary contributions during 2024. 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. The 401(k) plan remains in compliance with ERISA guidelines and continues to qualify for a “safe harbor” from most annual discrimination testing. We also offer a defined contribution plan to all eligible U.K. employees and offer related employer contributions. If an employee elects to make a minimum contribution of at least 1.0 percent of their base salary, we match with a contribution of 8.0 percent. We increase our contribution to a maximum of 12.0 percent as the employee increases their contribution from 1.0 percent to 5.0 percent. We do not increase our contribution percentage on employee contributions in excess of 5.0 percent. During the years ended December 31, 2023, 2022, and 2021, we recognized costs of $74.3 million, $70.9 million, and $71.0 million, respectively, for our U.S. defined contribution plan. We recognized costs of $5.7 million, $4.9 million, and $4.9 million in 2023, 2022, and 2021, respectively, for our U.K. defined contribution plan.

Stockholders' Equity and Earnin

Stockholders' Equity and Earnings Per Common Share	12 Months Ended
	Dec. 31, 2023
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 2023 2022 2021 (in millions of dollars, except share data) Numerator Net Income $ 1,283.8 $ 1,407.2 $ 981.0 Denominator (000s) Weighted Average Common Shares - Basic 196,659.7 200,647.2 204,232.9 Dilution for Assumed Exercises of Nonvested Stock Awards 942.3 1,462.2 615.0 Weighted Average Common Shares - Assuming Dilution 197,602.0 202,109.4 204,847.9 Net Income Per Common Share Basic $ 6.53 $ 7.01 $ 4.80 Assuming Dilution $ 6.50 $ 6.96 $ 4.79 We compute basic earnings per share by dividing net income by the weighted average number of common shares outstanding for the period. In computing earnings per share assuming dilution, we include potential common shares that are dilutive (those that reduce earnings per share). We use the treasury stock method to account for the effect of nonvested stock success units, nonvested restricted stock units, and nonvested performance share units on the computation of diluted earnings per share. Under this method, the potential common shares from nonvested stock success units and nonvested restricted stock units will
Stockholders' Equity Disclosure	Common Stock As part of our capital deployment strategy, we may repurchase shares of Unum Group's common stock, as authorized by our board of directors. The timing and amount of repurchase activity is based on market conditions and other considerations, including the level of available cash, alternative uses for cash, and our stock price. Our board of directors has authorized the following repurchase programs: October 2023 Authorization December 2022 Authorization 1 October 2021 Authorization (in millions) Effective Date January 1, 2024 January 1, 2023 October 25, 2021 Expiration Date None December 31, 2023 December 31, 2022 Authorized Repurchase Amount $ 500.0 $ 250.0 $ 250.0 Shares Repurchased Under Repurchase Program $ — $ 250.0 $ 250.0 Remaining Repurchase Amount at December 31, 2023 Not yet effective $ — $ — 1 In February 2023, the December 2022 program was modified to increase the authorized repurchase amount from $200.0 million to $250.0 million. In August 2022, the Inflation Reduction Act was signed into law in the U.S. and imposes a one percent excise tax on corporate stock repurchases effective January 1, 2023. This excise tax is recorded as part of the cost basis of treasury stock and is assessed on the fair market value of stock repurchases reduced by the fair market value of any shares issued during the period. 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 2023 2022 2021 (in millions) Shares Repurchased 5.7 5.7 1.9 Cost of Shares Repurchased 1 $ 252.0 $ 200.1 $ 50.0 1 Includes $0.1 million of commissions for the years ended December 31, 2023 and 2022, respectively. There were no commissions for the year ended December 31, 2021. Also includes $1.9 million of excise tax for the year ended December 31, 2023. There were no excise taxes during the years ended December 31, 2022 and 2021. As a part of our share repurchase program, we periodically enter into accelerated share repurchase agreements (ASR). Under the terms of these agreements, we make a prepayment to a financial counterparty for which we receive an initial delivery of approximately 75 percent of the total Unum Group common stock to be delivered under the agreement. We simultaneously enter into a forward contract indexed to the price of Unum Group common stock, which subjects the transactions to a future price adjustment. Under the terms of the agreements, we are to receive, or be required to pay, a price adjustment based on the volume weighted average price of Unum Group common stock during the term of the agreement, less a discount. Any price adjustment payable to us is settled in shares of Unum Group common stock. Any price adjustment we would be required to pay may be settled in either cash or common stock at our option. Details of our ASRs are as follows: Prepayment Date Prepayment Amount Initial Share Delivery Forward Contract Settlement Date Shares Delivered to Settle Forward Contract (in millions) January 2024 $100.0 1.6 March 2024 Not yet settled July 2023 50.0 0.8 September 2023 0.2 February 2022 50.0 1.3 April 2022 0.4 November 2021 50.0 1.4 November 2021 0.5 In December 2023, we retired 115.0 million shares of our treasury stock with a total cost of $3,642.5 million. 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, 2023
Share-Based Payment Arrangement [Abstract]
Disclosure of Compensation Related Costs, Share-based Payments	Description of Stock Plans Under the 2022 Stock Incentive Plan (the 2022 Plan), up to 6.8 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 award, under the 2022 plan is counted as 1.00 share. The exercise price for stock options issued cannot be less than the fair value of the underlying common stock as of the grant date. The maximum term of each stock option or stock appreciation right is ten years after the date of grant. At December 31, 2023, approximately 5.9 million shares were available for future grants under the 2022 Plan. Under the Stock Incentive Plan of 2017 (the 2017 Plan), which was terminated in May 2022 for the purposes of any further grants, up to 17.0 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 under the 2017 plan, defined as any award other than a stock option or stock appreciation right, were counted as 1.76 shares. Awards granted before the termination of the 2017 Plan remain outstanding in accordance with the plan's terms. Any shares subject to an outstanding award under the 2017 Plan that, after March 15, 2022, is not issued because the award is forfeited, terminates, expires or lapses without being exercised (as applicable), or is settled for cash, becomes available for issuance under the 2022 Plan. Stock options had a term of eight years after the date of grant and fully vested after three years. We issue new shares of common stock for all of our stock plan vestings and exercises. Stock Success Units (SSUs) SSUs are classified as equity. As of December 31, 2023 and 2022, there were 105 thousand shares and 208 thousand shares, respectively, of SSUs outstanding with a weighted average grant date fair value of $18.78 per share. There were no issuances of SSUs during 2023, 2022, or 2021. SSUs vest over a six year period, beginning at the date of grant. One-third of the SSUs are eligible for accelerated vesting on a cumulative basis at the end of each of the one-, three-, and five-year service periods that began on January 1, 2021, if certain performance goals are achieved. Forfeitable dividends on SSUs are accrued in the form of cash. Compensation cost for SSUs subject to accelerated vesting due to the achievement of certain performance conditions at the end of the one-, three-, and five-year service periods is recognized over the implicit service period. The total fair value of SSUs that vested during both 2023 and 2021 was $1.9 million. No SSUs vested during 2022. At December 31, 2023, we had $0.7 million of unrecognized compensation cost related to SSUs that will be recognized over a remaining weighted average period of 1.05 years. No SSUs were forfeited during 2023. Performance Share Units (PSUs) PSUs are classified as equity. There were no new tranches of PSUs issued during 2023, 2022, or 2021. Vesting for the PSUs occurred at the end of a three-year period and was 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 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, 2022, the three The total fair value of PSUs vested during 2023, 2022, and 2021 was $5.8 million, $4.2 million, and $6.6 million, respectively. At December 31, 2023, we had no unrecognized compensation cost related to PSUs as there are no remaining PSUs outstanding. The estimated compensation expense was adjusted for actual performance experience and was recognized ratably during the service period when it became probable that the performance conditions would be satisfied. Compensation cost for PSUs subject to accelerated vesting at the date of retirement eligibility was 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 2020 are as follows: Year Ended December 31, 2020 Expected Volatility (based on our and our peer group historical daily stock prices) 23 % Expected Life (equals the performance period) 3 years Risk Free Interest Rate (based on U.S. Treasury yields at the date of grant) 0.85 % Cash Incentive Units (CIUs) CIUs are denominated and settled in cash, with each unit representing the right to receive one dollar. Vesting for the CIUs occurs at the end of a three-year period and is based upon prospective company performance measures and our total shareholder return relative to a board-approved peer group during the three Activity for CIUs, which are classified as a liability, is as follows: Units (000s) Outstanding at December 31, 2022 15,247 Granted 9,004 Vested 1 (7,223) Outstanding at December 31, 2023 17,028 1 CIUs in the preceding table 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, 2023, the three-year performance period for the 2021 CIU grant was completed and the related awards vested, but the performance factor has not yet been applied. The performance factor will be applied during the first quarter of 2024, with payment of the awards at that time. The liability recorded in connection with CIUs at December 31, 2023, 2022, and 2021 was $37.7 million, $16.0 million, and $3.2 million, respectively. There were no CIU payments made during 2023, 2022, and 2021. We had approximately $3.4 million of unrecognized compensation cost related to CIUs that will be recognized over a weighted average period of 1.7 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 CIUs subject to accelerated vesting at the date of retirement eligibility is recognized over the implicit service period. The fair value of CIUs is estimated at each reporting period using the Monte-Carlo simulation mode l. Key assumptions used to value CIUs granted are as follows: Assumptions as of the Year Ended December 31, 2023 2023 Grant 2022 Grant Expected Volatility (based on our and our peer group historical daily stock prices) 30 % 27 % Expected Life (equals the performance period) 2 years 1 year Risk Free Interest Rate (based on U.S. Treasury yields at the date of grant) 4.26 % 4.75 % Assumptions as of the Year Ended December 31, 2022 2022 Grant 2021 Grant Expected Volatility (based on our and our peer group historical daily stock prices) 30 % 33 % Expected Life (equals the performance period) 2 years 1 year Risk Free Interest Rate (based on U.S. Treasury yields at the date of grant) 4.26 % 4.60 % Assumptions as of the Year Ended December 31, 2021 2021 Grant Expected Volatility (based on our and our peer group historical daily stock prices) 50 % Expected Life (equals the performance period) 2 years Risk Free Interest Rate (based on U.S. Treasury yields at the date of grant) 0.71 % Restricted Stock Units (RSUs) RSUs vest over a one three Activity for RSUs, which are classified as equity, is as follows: Weighted Average Shares Grant Date (000s) Fair Value Outstanding at December 31, 2022 2,182 $ 27.20 Granted 780 45.56 Vested (1,691) 29.54 Forfeited (58) 31.86 Outstanding at December 31, 2023 1,213 35.51 During 2023, 2022, and 2021, we issued RSUs with a weighted average grant date fair value per share of $45.56, $28.21, and $27.02, respectively. The total fair value of shares vested during 2023, 2022, and 2021 was $49.9 million, $28.0 million, and $23.9 million, respectively. At December 31, 2023, we had $26.0 million of unrecognized compensation cost related to RSUs that will be recognized over a weighted average period of 0.9 years. Cash-Settled RSUs Cash-settled RSUs vested over a one three Activity for cash-settled RSUs, which are classified as a liability, is as follows: Shares (000s) Outstanding at December 31, 2022 23 Vested (23) Outstanding at December 31, 2023 — There were no issuances of cash-settled RSUs during 2023, 2022, and 2021. 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 measured 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 were recognized as compensation cost over the service period. Changes in the amount of the liability due to stock price changes after the service period were recognized as compensation cost during the period in which the changes occurred. The liability recorded in connection with cash-settled RSUs at December 31, 2022, and 2021 was $0.8 million and $0.5 million, respectively. There was no remaining liability for cash-settled RSUs at December 31, 2023. Cash-settled RSU payments made during 2023, 2022, and 2021 were $1.1 million, $0.6 million, and $0.6 million, respectively. At December 31, 2023, we had no unrecognized compensation cost related to cash-settled RSUs as there are no remaining cash-settled RSUs outstanding. Expense Compensation expense for the stock based plans, as reported in our consolidated statements of income, is as follows: Year Ended December 31 2023 2022 2021 (in millions of dollars) Performance Share Units $ 0.3 $ 5.7 $ 3.3 Cash Incentive Units 21.7 12.8 3.2 Restricted Stock Units and Cash-Settled Restricted Stock Units 40.6 32.7 25.5 Stock Success Units 0.9 0.9 2.8 Other 0.6 0.6 0.6 Total Compensation Expense, Before Income Tax $ 64.1 $ 52.7 $ 35.4 Total Compensation Expense, Net of Income Tax $ 57.5 $ 47.3 $ 31.1 Cash received under all share-based payment arrangements for the years ended December 31, 2023, 2022, and 2021 was $5.2 million, $4.2 million, and $3.8 million, respectively.

Reinsurance

Reinsurance	12 Months Ended
	Dec. 31, 2023
Reinsurance Disclosures [Abstract]
Reinsurance	Reinsurance activity related to our premium income, policy benefits, and policy benefits remeasurement gain are as follows: Year Ended December 31 2023 2022 2021 (in millions of dollars) Direct Premium Income $ 10,286.8 $ 9,893.6 $ 9,736.8 Reinsurance Assumed 80.4 78.7 90.6 Reinsurance Ceded (321.2) (355.8) (352.4) Net Premium Income $ 10,046.0 $ 9,616.5 $ 9,475.0 Direct Policy Benefits $ 8,001.8 $ 8,205.3 $ 8,817.1 Reinsurance Assumed 138.7 135.1 145.0 Reinsurance Ceded (828.6) (798.3) (848.8) Net Policy Benefits $ 7,311.9 $ 7,542.1 $ 8,113.3 Direct Policy Benefits - Remeasurement Gain $ (49.2) $ (372.5) $ (546.2) Reinsurance Assumed (0.1) 36.4 1.9 Reinsurance Ceded (5.5) (211.4) (15.6) Net Policy Benefits - Remeasurement Gain $ (54.8) $ (547.5) $ (559.9) In December 2020, we completed the first phase of a reinsurance transaction, pursuant to which Provident, The Paul Revere Life Insurance Company (Paul Revere Life), and Unum America, wholly-owned domestic insurance subsidiaries of Unum Group and collectively referred to as "the ceding companies", each entered into separate reinsurance agreements with Commonwealth Annuity and Life Insurance Company (Commonwealth), to reinsure on a coinsurance basis effective as of July 1, 2020 approximately 75 percent of the Closed Block individual disability business, primarily direct business written by the ceding companies. In March 2021, we completed the second phase of the reinsurance transaction, pursuant to which the ceding companies and Commonwealth amended and restated their respective reinsurance agreements to reinsure on a coinsurance and modified coinsurance basis effective as of January 1, 2021, a substantial portion of the remaining Closed Block individual disability business that was not ceded in December 2020, primarily business previously assumed by the ceding companies. 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). In March 2021, PLC and Commonwealth amended and restated this agreement to incorporate the ALR cohort related to the additional business that was reinsured between the ceding companies and Commonwealth as part of the second phase of the transaction. As part of the amended and restated volatility cover, PLC received a payment from Commonwealth of approximately $18 million. In connection with the second phase of the reinsurance transaction, Commonwealth paid a total ceding commission to the ceding companies of $18.2 million. The ceding companies transferred assets of $767.0 million to Commonwealth, which consisted primarily of cash and fixed maturity securities. In addition, we recognized the following in 2021 related to the second phase: • Net realized investment gains totaling $67.6 million related to the transfer of investments. • Transaction costs totaling $6.2 million. • Reinsurance recoverable of $1,132.5 million related to the policies on claim status (DLR cohort). • A reduction to the cost of reinsurance, or prepaid reinsurance premium, of $99.4 million related to the DLR cohort. • Deposit asset of $5.0 million related to the ALR cohort. • Payable of $307.2 million related to the portfolio of invested assets associated with the business ceded on a modified coinsurance basis. We amortized the cost of reinsurance related to both Phase 1 and Phase 2 of $44.1 million, $50.3 million, and $69.8 million in 2023, 2022, and 2021, respectively. As of December 31, 2023, Commonwealth accounted for 56 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 39 percent of our reinsurance recoverable, 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 4 percent of our reinsurance recoverable is primarily related to business reinsured with other companies also 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. Less than 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, 2023
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 disability, group life and accidental death and dismemberment, and supplemental and voluntary lines of business. The group disability line of business includes long-term and short-term disability, medical stop-loss, and fee-based service products. The supplemental and voluntary line of business includes voluntary benefits, individual disability, 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 agent sales force and brokers. The Closed Block segment consists of group and individual long-term care, and other insurance products no longer actively marketed. We discontinued offering individual long-term care in 2009 and group long-term care in 2012. Other insurance products include individual disability, group pension, individual life and corporate-owned life insurance, reinsurance pools and management operations, and other miscellaneous product lines. In December 2020, we entered into the first phase of a reinsurance agreement to reinsure the majority of our Closed Block individual disability products to a third party. In March 2021, we completed the second phase of the reinsurance transaction to reinsure a portion of the remaining Closed Block individual disability business that was not ceded in December 2020. See Note 14 for further discussion. The Corporate segment includes investment income on corporate assets not specifically allocated to a line of business, interest expense on corporate debt, and certain other corporate income and expenses not allocated to a line of business. Impairment Loss on Internal-Use Software During 2021, we recognized an impairment loss of $12.1 million for previously capitalized internal-use software that we no longer plan to utilize. We determined that this internal-use software would no longer be developed in order to focus our efforts on the development of software that better supports our long-term strategic goals. The impairment loss reduced the carrying value of the internal-use software to zero and has been recorded within other expenses in the consolidated statements of income and is included within our Corporate segment. Segment information is shown below. Certain prior year amounts were reclassified to conform to current year presentation. Year Ended December 31 2023 2022 2021 (in millions of dollars) Premium Income Unum US Group Disability Group Long-term Disability $ 2,057.2 $ 1,911.7 $ 1,827.8 Group Short-term Disability 1,012.3 926.3 864.0 Group Life and Accidental Death & Dismemberment Group Life 1,679.0 1,669.1 1,641.9 Accidental Death & Dismemberment 175.5 173.7 165.1 Supplemental and Voluntary Voluntary Benefits 850.1 833.7 840.7 Individual Disability 527.0 461.1 459.8 Dental and Vision 278.1 275.8 272.7 6,579.2 6,251.4 6,072.0 Unum International Unum UK Group Long-term Disability 396.1 376.9 401.9 Group Life 169.3 138.2 112.3 Supplemental 141.5 114.0 112.6 Unum Poland 118.3 89.7 90.2 825.2 718.8 717.0 Colonial Life Accident, Sickness, and Disability 946.1 948.9 953.3 Life 426.5 401.1 384.7 Cancer and Critical Illness 353.5 352.0 352.2 1,726.1 1,702.0 1,690.2 Closed Block Long-term Care 696.0 697.4 704.3 All Other 219.5 246.9 291.5 915.5 944.3 995.8 Total Premium Income $ 10,046.0 $ 9,616.5 $ 9,475.0 Unum US Unum International Colonial Life Closed Block Corporate Total (in millions of dollars) Year Ended December 31, 2023 Premium Income $ 6,579.2 $ 825.2 $ 1,726.1 $ 915.5 $ — $ 10,046.0 Net Investment Income 639.9 137.2 153.5 1,066.3 99.8 2,096.7 Other Income 220.5 1.6 1.2 52.6 3.3 279.2 Adjusted Operating Revenue $ 7,439.6 $ 964.0 $ 1,880.8 $ 2,034.4 $ 103.1 $ 12,421.9 Adjusted Operating Income (Loss) $ 1,355.5 $ 158.1 $ 400.1 $ 164.9 $ (146.4) $ 1,932.2 Interest and Debt Expense $ — $ — $ — $ — $ 194.8 $ 194.8 DAC Amortization $ 267.6 $ 8.4 $ 205.4 $ — $ — $ 481.4 Depreciation and Intangible Amortization $ 76.3 $ 14.6 $ 13.6 $ 5.2 $ 0.6 $ 110.3 Year Ended December 31, 2022 Premium Income $ 6,251.4 $ 718.8 $ 1,702.0 $ 944.3 $ — $ 9,616.5 Net Investment Income 676.3 170.1 152.7 1,070.6 52.5 2,122.2 Other Income 196.3 0.9 1.1 58.0 4.8 261.1 Adjusted Operating Revenue $ 7,124.0 $ 889.8 $ 1,855.8 $ 2,072.9 $ 57.3 $ 11,999.8 Adjusted Operating Income (Loss) $ 972.6 $ 134.0 $ 412.9 $ 251.9 $ (164.3) $ 1,607.1 Interest and Debt Expense $ — $ — $ — $ — $ 188.5 $ 188.5 Costs Related to Early Retirement of Debt $ — $ — $ — $ — $ 4.2 $ 4.2 DAC Amortization $ 240.9 $ 8.2 $ 172.0 $ — $ — $ 421.1 Depreciation and Intangible Amortization $ 75.7 $ 14.4 $ 15.0 $ 4.7 $ 0.6 $ 110.4 Year Ended December 31, 2021 Premium Income $ 6,072.0 $ 717.0 $ 1,690.2 $ 995.8 $ — $ 9,475.0 Net Investment Income 721.6 132.7 172.0 1,159.0 27.9 2,213.2 Other Income 170.0 0.6 1.0 65.1 6.2 242.9 Adjusted Operating Revenue $ 6,963.6 $ 850.3 $ 1,863.2 $ 2,219.9 $ 34.1 $ 11,931.1 Adjusted Operating Income (Loss) $ 398.9 $ 105.7 $ 404.3 $ 420.1 $ (177.9) $ 1,151.1 Interest and Debt Expense $ — $ — $ — $ — $ 185.0 $ 185.0 Costs Related to Early Retirement of Debt $ — $ — $ — $ — $ 67.3 $ 67.3 DAC Amortization $ 285.9 $ 7.0 $ 159.2 $ — $ — $ 452.1 Depreciation and Intangible Amortization $ 81.9 $ 13.0 $ 16.3 $ 5.1 $ 0.7 $ 117.0 December 31 2023 2022 (in millions of dollars) Assets Unum US $ 15,561.1 $ 16,356.3 Unum International 3,372.9 3,129.4 Colonial Life 4,830.4 4,575.0 Closed Block 35,272.8 33,776.6 Corporate 4,218.0 3,311.2 Total Assets $ 63,255.2 $ 61,148.5 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, 2023 and 2022 goodwill was $349.9 million and $347.6 million, respectively, with $280.0 million attributable to Unum US in each year, $42.2 million and $39.9 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 investment gains and losses, the amortization of the cost of reinsurance, the impact of non-contemporaneous reinsurance, and reserve assumption updates as well as certain other items as specified in the reconciliations below. We believe adjusted operating revenue and adjusted operating income or loss are better performance measures and better indicators of the revenue and profitability and underlying trends in our business. These performance measures are in accordance with GAAP guidance for segment reporting, but they should not be viewed as a substitute for total revenue, income before income tax, net income, or net loss. Investment gains or losses primarily include realized investment gains or losses, expected investment credit losses, and gains or losses on derivatives. 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 investment gains or losses. Although we may experience 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. Cash flow assumptions used to calculate our liability for future policy benefits are reviewed at least annually and updated, as needed, with the resulting impact reflected in net income. While the effects of these assumption updates are recorded in the reporting period in which the review is completed, these updates reflect experience emergence and changes to expectations spanning multiple periods. We believe that by excluding the impact of reserve assumption updates we are providing a more comparable and consistent view of our quarterly results. We exited a substantial portion of our Closed Block individual disability product line through the two phases of the reinsurance transaction that were executed in December 2020 and March 2021. As a result, we exclude the amortization of the cost of reinsurance that we recognized upon the exit of the business related to the policies on claim status as well as the impact of non-contemporaneous reinsurance that resulted from the adoption of ASU 2018-12. Due to the execution of the second phase of the reinsurance transaction occurring after January 1, 2021, the transition date of ASU 2018-12, in accordance with the provisions of the ASU related to non-contemporaneous reinsurance, we were required to establish the ceded reserves using an upper- medium grade fixed-income instrument as of the reinsurance transaction date in March 2021 which resulted in higher ceded reserves compared to that which was reported historically. However, the direct reserves for the block reinsured in the second phase were calculated using the original discount rate utilized as of the transition date. Both the direct and ceded reserves are then remeasured at each reporting period using a current discount rate reflective of an upper-medium grade fixed-income instrument, with the changes recognized in OCI. While the total equity impact is neutral, the different original discount rates utilized for direct and ceded reserves result in disproportionate earnings impacts. The impact of non-contemporaneous reinsurance will fluctuate depending on the magnitude of reserve changes during the period. We believe that the exclusion of these items 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 3, 6, 10, 14, and 17 for further discussion regarding the items specified in the reconciliation below. 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 2023 2022 2021 (in millions of dollars) Total Revenue $ 12,385.9 $ 11,984.1 $ 12,007.8 Excluding: Net Investment Gain (Loss) (36.0) (15.7) 76.7 Adjusted Operating Revenue $ 12,421.9 $ 11,999.8 $ 11,931.1 Income Before Income Tax $ 1,640.1 $ 1,750.0 $ 1,260.6 Excluding: Net Investment Gains and Losses Net Realized Investment Gain Related to Reinsurance Transaction — — 67.6 Net Investment Gain (Loss), Other (36.0) (15.7) 9.1 Total Net Investment Gain (Loss) (36.0) (15.7) 76.7 Items Related to Closed Block Individual Disability Reinsurance Transaction Amortization of the Cost of Reinsurance (44.1) (50.3) (69.8) Non-Contemporaneous Reinsurance (34.8) (34.4) (32.9) Transaction Costs — — (6.2) Total Items Related to Closed Block Individual Disability Reinsurance Transaction (78.9) (84.7) (108.9) Reserve Assumption Updates (177.2) 243.3 235.0 Impairment Loss on Internal-Use Software — — (12.1) Cost Related to Early Retirement of Debt — — (67.3) Impairment Loss on ROU Asset — — (13.9) Adjusted Operating Income $ 1,932.2 $ 1,607.1 $ 1,151.1

Commitments and Contingent Liab

Commitments and Contingent Liabilities	12 Months Ended
	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies Disclosure	Commitments See Notes 2 and 3 for further discussion on certain of our investment commitments. 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. Claim 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.

Leases

Leases	12 Months Ended
	Dec. 31, 2023
Leases [Abstract]
Lessee, Operating 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. We have the option to renew the majority of our building leases and equipment leases at the end of the lease term at the fair rental value at the time of renewal. 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 2023 2022 2021 (in millions of dollars) Lease Cost Operating Lease Cost $ 16.4 $ 19.6 $ 35.2 Sublease Income (1.5) (1.1) (1.0) Total Lease Cost $ 14.9 $ 18.5 $ 34.2 Other Information Cash Paid for Amounts Included in the Measurement of Lease Liabilities $ 20.3 $ 23.1 $ 29.9 Weighted-Average Remaining Lease Term 5 years 6 years 6 years Weighted-Average Discount Rate 4.85 % 4.32 % 4.45 % As of December 31, 2023, aggregate undiscounted minimum lease payments and the reconciliation to our lease liability are as follows (in millions of dollars): 2024 $ 19.2 2025 13.9 2026 11.1 2027 9.3 2028 9.0 2029 and Thereafter 9.1 Total 71.6 Less Imputed Interest 9.0 Lease Liability $ 62.6 The right-of-use asset was $ 35.8 37.7 During 2021, we recognized an impairment loss of $13.9 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, 2023
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 were deficient by $2,100.0 million as of December 31, 2018, the financial statement date of the examination period. The amount reserves are deficient may increase or decrease over time based on changes in assumed reinvestment rates, policyholder inventories, premium rate increase activity, and the underlying growth in the locked in statutory reserve basis as well as updates to other long term actuarial assumptions. 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. The calculation of the premium deficiency reserve (PDR) reflects specific assumptions set by MBOI and results in significant margin above Unum America’s best estimate assumptions. As of December 31, 2023, the PDR calculated under the basis resulting from the MBOI examination has been fully recognized. The phase in amounts for 2023, 2022, and 2021 were funded using cash flows from operations and capital contributions from Unum Group. Our long-term care reserves and financial results reported under generally accepted accounting principles were not affected by the MBOI’s examination conclusion. Additional information regarding the Unum America PDR is as follows: Year Ended December 31 2023 2022 2021 (in millions of dollars) Premium Deficiency Reserve Gross Premium Deficiency Reserve 1 $ 1,604 $ 2,851 $ 2,977 Cumulative Gross Premium Deficiency Reserve Recognized 1,604 1,191 667 Remaining Premium Deficiency Reserve to be Recognized $ — $ 1,660 $ 2,310 1 The gross PDR decreased by $1,247 million during 2023 due primarily to changes in the assumed reinvestment rate as well as premium rate increase activity. The gross PDR decreased by $126 million during 2022 due primarily to premium rate increase activity and underlying growth in the locked-in statutory reserve basis. The gross PDR increased by $687 million during 2021 due primarily to changes in the assumed reinvestment rate. The increase for 2021 was from a gross PDR of $2,290 million as of December 31, 2020, which was an increase from the original $2,100 million reserve deficiency as of December 31, 2018. 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 for the years under examination prior to the year ended December 31, 2023. 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 blocks of long-term care 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 $469 million and $351 million as of December 31, 2023 and 2022 respectively. The 2023, 2022, and 2021 results for Fairwind include the $413 million, $524 million, and $438 million increases to long-term care statutory reserves assumed from Unum America. Northwind Re was established for the limited purpose of reinsuring risks attributable to specified policies issued or reinsured by Provident, Paul Revere Life, and Unum America, and had no material state prescribed accounting practices that differ from statutory accounting principles prescribed by the NAIC. In 2021, Northwind Re obtained a Certificate of Dormancy from the Vermont Department of Financial Regulation authorizing it to exist as a dormant captive insurance company, leaving Fairwind as the only remaining active captive reinsurer. Northwind Re was merged with one of our non-insurance U.S. holding companies, Northwind Holdings, with Northwind Holdings remaining as the surviving company. Subsequently during 2022, Northwind Holdings was merged into Unum Group. 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 2023 2022 2021 (in millions of dollars) Combined Net Income (Loss) Traditional U.S. Life Insurance Subsidiaries $ 1,329.9 $ 965.4 $ 779.5 Captive Reinsurers $ (318.3) $ (432.2) $ (159.0) Combined Net Gain (Loss) from Operations, After Tax Traditional U.S. Life Insurance Subsidiaries $ 1,351.5 $ 965.4 $ 681.1 Captive Reinsurers $ (279.4) $ (428.6) $ (247.4) December 31 2023 2022 (in millions of dollars) Combined Capital and Surplus Traditional U.S. Life Insurance Subsidiaries $ 3,751.3 $ 3,816.3 Captive Reinsurers $ 1,534.9 $ 1,229.6 Solvency II, a European Union directive that is part of retained U.K. law pursuant to the European Union (Withdrawal) Act 2018, prescribes capital requirements and risk management standards for the European insurance industry. As derived from the most recent annual financial statements for December 31, 2022, based on Solvency II requirements, regulatory net income and eligible own funds available of our United Kingdom insurance subsidiary, Unum Limited, were £569.2 million and £622.7 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, 2023 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 net realized capital 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 $1,289 million is available, without prior approval by regulatory authorities, during 2024 for the payment of dividends to Unum Group from its traditional U.S. life insurance subsidiaries. The ability of our captive insurer to pay dividends to Unum Group will depend on the satisfaction of applicable regulatory requirements and on the performance of the business reinsured by Fairwind. 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 £140 million is considered distributable from Unum Limited during 2024, subject to local solvency standards and regulatory approval. Deposits

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, 2023
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, 2023 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 $ 618.6 $ 624.8 $ 624.8 States, Municipalities, and Political Subdivisions 4,041.3 3,678.4 3,678.4 Foreign Governments 982.1 890.7 890.7 Public Utilities 5,398.2 5,321.6 5,321.6 Mortgage/Asset-Backed Securities 658.0 644.1 644.1 All Other Corporate Bonds 26,708.4 25,670.7 25,670.7 Redeemable Preferred Stocks 4.0 3.6 3.6 Total Fixed Maturity Securities 38,410.6 $ 36,833.9 36,833.9 Mortgage Loans 2,328.4 2,318.2 Policy Loans 3,620.2 3,620.2 Other Long-term Investments Derivatives (2) — 99.9 Perpetual Preferred and Equity Securities (3) 27.8 31.9 Private Equity Partnerships (3) 1,134.6 1,326.2 Miscellaneous Long-term Investments 121.4 121.4 Short-term Investments 1,610.7 1,610.7 Total Investments $ 47,253.7 $ 45,962.4 (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 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 and equity securities primarily results from changes in the partnership owner's equity and the security's market valuation since acquisition, respectively.

Schedule II Condensed Finacial

Schedule II Condensed Finacial Information of Registrant	12 Months Ended
	Dec. 31, 2023
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 2023 2022 (in millions of dollars) Assets Fixed Maturity Securities - at fair value (amortized cost: $656.2; $748.1) $ 596.1 $ 657.7 Other Long-term Investments 27.0 19.3 Short-term Investments 970.9 845.8 Investment in Subsidiaries 11,663.6 10,815.7 Deferred Income Tax 118.1 114.9 Other Assets 593.6 555.5 Total Assets $ 13,969.3 $ 13,008.9 Liabilities and Stockholders' Equity Liabilities Short-term Debt $ — $ 2.0 Long-term Debt 3,430.4 3,427.8 Pension and Postretirement Benefits 350.2 352.6 Other Liabilities 537.3 491.5 Total Liabilities 4,317.9 4,273.9 Stockholders' Equity Common Stock, $0.10 par Authorized: 725,000,000 shares Issued: 194,588,625 and 308,306,490 shares 19.4 30.8 Additional Paid-in Capital 1,547.8 2,441.0 Accumulated Other Comprehensive Loss (3,308.0) (3,448.3) Retained Earnings 11,431.5 13,141.3 Treasury Stock - at cost: 1,216,528 and 110,551,977 shares (39.3) (3,429.8) Total Stockholders' Equity 9,651.4 8,735.0 Total Liabilities and Stockholders' Equity $ 13,969.3 $ 13,008.9 SCHEDULE II--CONDENSED FINANCIAL INFORMATION OF REGISTRANT (Continued) Unum Group (Parent Company) STATEMENTS OF INCOME Year Ended December 31 2023 2022 2021 (in millions of dollars) Cash Dividends from Subsidiaries $ 1,581.1 $ 1,306.6 $ 909.8 Non-Cash Dividends from Subsidiaries — 23.0 719.6 Other Income 90.3 81.8 53.5 Total Revenue 1,671.4 1,411.4 1,682.9 Interest and Debt Expense 194.8 188.5 185.9 Cost Related to Early Retirement of Debt — 4.2 67.3 Other Expenses 54.2 35.6 39.1 Total Expenses 249.0 228.3 292.3 Income of Parent Company Before Income Tax 1,422.4 1,183.1 1,390.6 Income Tax Expense (Benefit) (9.5) 14.7 (24.1) Income of Parent Company 1,431.9 1,168.4 1,414.7 Equity in Undistributed Earnings (Loss) of Subsidiaries (148.1) 238.8 (433.7) Net Income 1,283.8 1,407.2 981.0 Other Comprehensive Income, Net of Tax 140.3 1,716.3 1,145.6 Comprehensive Income $ 1,424.1 $ 3,123.5 $ 2,126.6 SCHEDULE II--CONDENSED FINANCIAL INFORMATION OF REGISTRANT (Continued) Unum Group (Parent Company) STATEMENTS OF CASH FLOWS Year Ended December 31 2023 2022 2021 (in millions of dollars) Cash Provided by Operating Activities $ 1,548.0 $ 1,250.2 $ 861.0 Cash Flows from Investing Activities Proceeds from Sales and Maturities of Fixed Maturity Securities 97.1 192.1 245.5 Proceeds from Sales and Maturities of Other Investments 23.9 7.4 20.1 Purchase of Fixed Maturity Securities (44.5) (102.7) (2.0) Purchase of Other Investments (23.4) (32.0) (0.9) Net Purchases of Short-term Investments (104.4) (209.6) (465.0) Cash Distributions to Subsidiaries (854.5) (540.2) (300.9) Net Purchases of Property and Equipment (113.1) (94.0) (91.3) Cash Used by Investing Activities (1,018.9) (779.0) (594.5) Cash Flows from Financing Activities Short-term Debt Repayment (2.0) — — Issuance of Long-term Debt — 349.2 588.1 Long-term Debt Repayment — (364.0) (500.0) Cost Related to Early Retirement of Debt — (3.6) (62.8) Issuance of Common Stock 5.2 4.0 3.4 Repurchase of Common Stock (250.1) (200.1) (50.0) Dividends Paid to Stockholders (277.1) (254.2) (239.4) Other, Net — 0.7 (1.6) Cash Used by Financing Activities (524.0) (468.0) (262.3) Increase in Cash $ 5.1 $ 3.2 $ 4.2

Schedule III Supplementary Insu

Schedule III Supplementary Insurance Information	12 Months Ended
	Dec. 31, 2023
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 Future Policy Benefits Policyholders' Account Balances Unearned Premiums (in millions of dollars) December 31, 2023 Unum US $ 1,232.2 $ 9,419.1 $ 678.1 $ 54.6 Unum International 46.9 2,305.3 — 151.4 Colonial Life 1,435.4 1,997.8 869.8 44.5 Closed Block — 26,287.2 4,119.8 129.7 Total $ 2,714.5 $ 40,009.4 $ 5,667.7 $ 380.2 December 31, 2022 Unum US $ 1,185.1 $ 9,710.3 $ 679.7 $ 55.8 Unum International 37.0 2,063.3 — 130.4 Colonial Life 1,337.9 1,858.4 869.1 42.7 Closed Block — 24,945.1 4,191.4 136.6 Total $ 2,560.0 $ 38,577.1 $ 5,740.2 $ 365.5 SCHEDULE III--SUPPLEMENTARY INSURANCE INFORMATION (Continued) Unum Group and Subsidiaries Segment Premium Income Net Investment Income 1 Policy Benefits Including Remeasurement Loss or Gain 2 Amortization of Deferred Acquisition Costs All Other Expenses 3 Premiums Written 4 (in millions of dollars) December 31, 2023 Unum US $ 6,579.2 $ 639.9 $ 3,808.5 $ 267.6 $ 1,879.2 $ 4,634.3 Unum International 825.2 137.2 579.8 8.4 235.6 544.4 Colonial Life 1,726.1 153.5 798.1 205.4 396.5 1,221.8 Closed Block 915.5 1,066.3 2,070.7 — 246.5 904.2 Corporate — 99.8 — — 249.5 — Total $ 10,046.0 $ 2,096.7 $ 7,257.1 $ 481.4 $ 3,007.3 December 31, 2022 Unum US $ 6,251.4 $ 676.3 $ 3,970.9 $ 240.9 $ 1,768.8 $ 4,335.7 Unum International 718.8 170.1 549.6 8.2 190.4 504.1 Colonial Life 1,702.0 152.7 826.1 172.0 389.6 1,221.8 Closed Block 944.3 1,070.6 1,648.0 — 248.0 936.8 Corporate — 52.5 — — 221.6 — Total $ 9,616.5 $ 2,122.2 $ 6,994.6 $ 421.1 $ 2,818.4 December 31, 2021 Unum US $ 6,072.0 $ 721.6 $ 4,430.3 $ 285.9 $ 1,616.8 $ 4,168.9 Unum International 717.0 132.7 553.0 7.0 180.4 520.6 Colonial Life 1,690.2 172.0 911.7 159.2 364.5 1,223.3 Closed Block 995.8 1,159.0 1,658.4 — 274.7 983.0 Corporate — 27.9 — — 305.3 — Total $ 9,475.0 $ 2,213.2 $ 7,553.4 $ 452.1 $ 2,741.7 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 policy benefits including remeasurement loss or gain were the following: • In 2023, reserve assumption updates resulting in a net decrease in policy benefits including remeasurement gain or loss in the Unum US and Colonial Life segments of $128.8 million and $80.7 million, respectively and a net increase in policy benefits including remeasurement gain or loss in the Unum International and Closed Block segments of $17.9 million and $368.8 million, respectively. • In 2022, reserve assumption updates resulting in a net decrease in policy benefits including remeasurement gain or loss in the Unum US, Unum International, Colonial Life, and Closed Block segments of $170.8 million, $7.6 million, $55.2 million, and $9.7 million, respectively. • In 2021, reserve assumption updates resulting in a net decrease in policy benefits including remeasurement gain or loss in the Unum US, Unum International, and Colonial Life segments of $231.7 million, $4.2 million, and $23.5 million, respectively and a net increase in policy benefits including remeasurement gain or loss in the Closed Block segment of $24.4 million. • In 2023, 2022, and 2021 the impact of non-contemporaneous reinsurance of $34.8 million, $34.4 million, and $32.9 million respectively, in the Closed Block segment. SCHEDULE III--SUPPLEMENTARY INSURANCE INFORMATION (Continued) Unum Group and Subsidiaries 3 Includes commissions, interest and debt expense, 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. Also included in all other expenses were the following: • In 2023, 2022, and 2021 the amortization of the cost of reinsurance of $44.1 million, $50.3 million, and $69.8 million respectively, in the Closed Block segment. • In 2021, an impairment loss of $12.1 million was recorded in our Corporate segment for previously capitalized internal-use software that we no longer plan to utilize. • In 2021, costs related to early retirement of debt of $67.3 million in the Corporate segment. • In 2021, transaction costs of $6.2 million related to the Closed Block individual disability reinsurance transaction. • In 2021, a right-of-use asset impairment of $13.9 million related to one of our operating leases for office space that we do not plan to continue using to support general operations in the Corporate segment. 4 Excludes life insurance.

Schedule IV Reinsurance

Schedule IV Reinsurance	12 Months Ended
	Dec. 31, 2023
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, 2023 Life Insurance in Force $ 1,079,042.5 $ 21,210.7 $ 921.6 $ 1,058,753.4 0.1 % Premium Income: Life Insurance $ 2,799.0 $ 157.5 $ 6.0 $ 2,647.5 0.2 % Accident, Health, and Other Insurance 7,487.8 163.7 74.4 7,398.5 1.0 % Total $ 10,286.8 $ 321.2 $ 80.4 $ 10,046.0 0.8 % Year Ended December 31, 2022 Life Insurance in Force $ 1,057,312.2 $ 35,773.9 $ 931.9 $ 1,022,470.2 0.1 % Premium Income: Life Insurance $ 2,704.3 $ 155.1 $ 6.5 $ 2,555.7 0.3 % Accident, Health, and Other Insurance 7,189.3 200.7 72.2 7,060.8 1.0 % Total $ 9,893.6 $ 355.8 $ 78.7 $ 9,616.5 0.8 % Year Ended December 31, 2021 Life Insurance in Force $ 1,007,562.2 $ 37,794.6 $ 920.3 $ 970,687.9 0.1 % Premium Income: Life Insurance $ 2,544.7 $ 150.2 $ 7.6 $ 2,402.1 0.3 % Accident, Health, and Other Insurance 7,192.1 202.2 83.0 7,072.9 1.2 % Total $ 9,736.8 $ 352.4 $ 90.6 $ 9,475.0 1.0 %

Schedule V Valuation and Qualif

Schedule V Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2023
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 Additions Charged to Costs and Expenses Deductions 1 Balance at End of Year (in millions of dollars) Year Ended December 31, 2023 Allowance for expected credit losses (deducted from accounts and premiums receivable) $ 32.5 $ 11.3 $ 14.3 $ 29.5 Allowance for expected credit losses (deducted from reinsurance recoverable) $ 1.7 $ 0.1 $ 0.1 $ 1.7 Year Ended December 31, 2022 Allowance for expected credit losses (deducted from accounts and premiums receivable) $ 34.2 $ 10.8 $ 12.5 $ 32.5 Allowance for expected credit losses (deducted from reinsurance recoverable) $ 2.3 $ — $ 0.6 $ 1.7 Year Ended December 31, 2021 Allowance for expected credit losses (deducted from accounts and premiums receivable) $ 38.8 $ 18.2 $ 22.8 $ 34.2 Allowance for expected credit losses (deducted from reinsurance recoverable) $ 11.7 $ 0.7 $ 10.1 $ 2.3 1 Deductions include amounts deemed to reduce exposure of expected losses on premium and accounts receivables and reinsurance recoverable, amounts deemed uncollectible, and amounts related to fluctuations in the foreign currency exchange rate. 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 9 of the "Notes to Consolidated Financial Statements" contained herein in Item 8 for a discussion of these items.

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pay vs Performance Disclosure
Net Income	$ 1,283.8	$ 1,407.2	$ 981

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
	Dec. 31, 2023
Trading Arrangements, by Individual
Material Terms of Trading Arrangement	On November 17, 2023, Steven A. Zabel, our Executive Vice President, Chief Financial Officer, adopted a Rule 10b5-1 trading arrangement intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). The trading arrangement provides for the sale of up to 10,000 shares of our common stock between March 13, 2024 and November 15, 2024.
Name	Steven A. Zabel
Title	Executive Vice President, Chief Financial Officer
Rule 10b5-1 Arrangement Adopted	true
Adoption Date	November 17, 2023

Signficant Accounting Policies

Signficant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2023
Accounting policies and error corrections [Abstract]
Basis of Presentation	Basis of Presentation
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. In accordance with standard practice, we regularly review the methodology used in the development of all key estimates. As a result of this review, in 2022, we updated our estimate of the unearned premium reserve for certain of our product lines to utilize a gross unearned premium reserve rather than a net unearned premium reserve. The effect of this change in estimate was to decrease 2022 premium income by $13.4 million and decrease commissions by $1.0 million. This resulted in a decrease to net income of $9.8 million and a decrease to both basic and diluted earnings per share by $0.05.
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, net of income tax. Realized investment gains or losses are based upon specific identification of the investments sold. 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 cost 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. When an allowance for credit losses on a fixed maturity security is recognized, we designate non-accrual status for those securities. We reverse all previously accrued interest through interest income and use a cash basis method for recognizing any future payments received. See Notes 2 and 3.
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 typically 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 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 private equity partnerships, real estate, perpetual preferred stock, common stock, and tax credit partnerships. 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. Our perpetual preferred stocks are valued at fair value, based on quoted market prices, where available. For preferred stocks not actively traded, fair values are estimated using values obtained from independent pricing services. Our investments in common stock are valued at fair value. Our shares of Federal Home Loan Bank (FHLB) common stock are carried at cost, which approximates fair value. 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. 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
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 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 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 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 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 the same income statement line item as the hedged item during the period of change in fair value. Cash flows related to derivative contracts are included in the consolidated statements of cash flows, coinciding with the timing of the hedged item. Cash inflows are included as a component of proceeds from sales and maturities of other investments. Cash outflows are included as a component of purchases of other investments.
Fair Value Measurement	Fair Value Measurement
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.
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. Our insurance contracts are grouped by product type and contract issue year into cohorts consistent with the grouping used to estimate the related contract liabilities. DAC is amortized on a constant level basis over the life of the policy. For all products, in-force volume metrics are used as the constant level basis. The lapse and mortality assumptions used to amortize DAC for our traditional long-duration products are consistent with the assumptions used to estimate the liability for future policy benefits. The underlying assumptions used to determine DAC amortization are updated concurrently with any related assumption changes for the liability for future policy benefits and changes in estimates are recognized prospectively over the remaining expected term of the related contracts. Amortization expense is adjusted based on actual versus expected experience through an adjustment to the prospective rate of amortization. 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, principally on group contracts. Internal replacement transactions wherein the modification does not substantially change the policy are accounted for as continuations of the replaced contracts. The original policy continues to be reflected as an in force policy within its original cohort. The policy's expected life then impacts the amortization of remaining unamortized deferred acquisition costs within its cohort. The costs of replacing the policy are accounted for as policy maintenance costs and expensed as incurred. Internal replacement transactions 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. The original policy that was replaced is terminated from its original cohort and this termination is reflected in the amortization rate of remaining unamortized deferred acquisition costs for the cohort. The costs of acquiring the new policy are capitalized and amortized as part of a new cohort. See note 8.
Goodwill	Goodwill
Property and Equipment	Property and Equipment
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 $63.9 million and $62.9 million at December 31, 2023 and 2022, respectively. The accumulated amortization for value of business acquired was $161.8 million and $150.3 million as of December 31, 2023 and 2022, respectively. The amortization of value of business acquired, which is included in other expenses in the consolidated statements of income, was $5.2 million, $4.9 million, and $5.7 million for the years ended December 31, 2023, 2022, and 2021, respectively. We periodically review the carrying amount of value of business acquired and it is subject to recoverability testing on an annual basis, or more frequently, if appropriate.
Reserves for Policy and Contract Benefits	Future Policy Benefits: Liabilities for future policy benefits represent the cost of claims that we estimate we will eventually pay to our policyholders which includes policy liabilities for claims not yet incurred and for claims that have been incurred or are estimated to have been incurred but not yet reported to us. Liabilities for future policy benefits also include the related expenses for our non interest-sensitive life and accident and health products. The liability for future policy benefits is calculated based on the present value of the estimated future policy benefits less the present value of estimated future net premiums collected. Net premiums represent the portion of the gross premium required to provide for all benefits and expenses, excluding acquisition costs or any costs that are required to be charged to expense as incurred. In calculating the liability for future policy benefits, our long-duration contracts are grouped into cohorts by product type and contract issue year. The calculation of the liability for future policy benefits involves numerous assumptions including assumptions related to discount rate, lapses, mortality, and morbidity. The discount rate assumptions were initially set based on the expected investment yield of the assets supporting the reserves at the transition date of accounting standards update (ASU) 2018-12, which was January 1, 2021, for policies originally issued on or before the transition date. The discount rate assumptions for new cohorts established after the transition date, are initially set based on the policy issuance date or policy renewal date, and are based on an upper-medium grade fixed-income instrument, which is generally equivalent to a single-A interest rate matched to the duration of our insurance liabilities. As cohorts are grouped by product type and issue year, a weighted average discount rate is utilized as policies are issued or renewed throughout the year. We utilize a reference portfolio of fixed-income instruments that have been A-rated by one of the major credit rating agencies. For products with liability cash flows that exceed the duration of observable single-A fixed income instruments, we use the last market observable yield and use extrapolation approaches to determine yield assumptions for durations beyond the last market observable duration. For the discount rate assumptions for products in our Unum International segment, we utilize observable market data in the local debt markets in the UK and Poland. The initial, also referred to as the original, discount rate assumptions established for each cohort are used to determine interest accretion which is reported as a component of policy benefits on the statements of income. After policy issuance or policy renewal, the discount rate assumptions are updated quarterly and used to update the liability at each reporting date to the current discount rate, with the corresponding change reflected as the change in the effect of discount rate assumptions on the liability for future policy benefits, net of reinsurance, on the statement of changes in other comprehensive income (loss). Policyholder lapse and mortality assumptions reflect the probability that an insureds’ coverage is discontinued due to lapsation or death of the insured. For our life insurance products, mortality assumptions also reflect the probability that a benefit payment occurs. Policyholder lapse and mortality 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 claim incidence rate assumption is the rate at which new claims are submitted and the development of this assumption may involve many factors, including the age of the insured, the insured's occupation or industry, the benefit plan design, and certain external factors such as consumer confidence and levels of unemployment. The claim resolution rate assumption is the probability that a claim will close due to recovery or death of the insured and is used to estimate how long benefits will be paid on an open claim. Certain product lines may utilize additional assumptions in calculating the liability for future policy benefits in addition to those listed above such as premium rate increases for long-term care, benefit offsets for long-term disability, and claim costs for voluntary benefits. Claim costs capture the combined effect of the incidence rate, the expected level of benefit to be paid, and the claim resolution rate. Cash flow assumptions are reviewed and updated, as needed, at least annually. Assumptions may be updated more frequently if necessary based on trending experience and future expectations. On a quarterly basis, cohort level cash flow measures are updated based on the emergence of actual experience. The updated cash flows are used to determine the updated net premiums and the net premium ratio, which is the present value of benefits and related expenses divided by the present value of gross premiums. The updated net premium ratio is used to calculate the updated liability for future policy benefits as of the beginning of the year, at the original discount rate. The change in the liability for future policy benefits, at the original discount rate, as of the beginning of the period, resulting from changes in cash flow assumptions and resulting from the emergence of actual experience from expected experience, is reflected as the policy benefits - remeasurement loss (gain) in the consolidated statements of income. The impact of all other changes in the liability for future policy benefits are reflected as policy benefits in the consolidated statements of income. For most products, a net premium methodology is applied to each cohort to estimate the liability for claims not yet incurred in which discounted gross benefits are compared to discounted gross premiums. In this methodology, actual experience to date is combined with projected future cash flows to determine a net premium ratio for each cohort. The future cash flows include the costs of future expected claims as well as future cash flows on claims that have already been incurred. The net premium ratio is then used to estimate the liability for future policy benefits. The liability for future policy benefits represents the present value of future claims and associated expenses less the present value of future net premiums, which is derived by multiplying the present value of future gross premium by the net premium ratio. For our group products in the Unum US and Unum International segments, we evaluate the liability for future policy benefits required for active policies in comparison to incurred claims. Given the term nature of the products, their renewal features, and level funding nature of the premium for these products, we have determined that the liability value is generally zero for policies that are not on claim. For these products, our liability for future policy benefit values are limited to the liability associated with claims incurred as of the valuation date. Multiple estimation methods exist to establish liabilities for the incurred claim component of future policy benefits. Available reserving methods utilized to calculate these liabilities include the tabular reserve method, the paid loss development method, the incurred loss development method, the count and severity method, and the expected claim cost method. No single method is better than the others in all situations and for all product lines. The estimation methods we have chosen are those that we believe produce the most accurate and reliable liability. We use a tabular reserve methodology on reported claims for our Unum US group long-term disability and individual disability claims as well as for our Closed Block long-term care claims. Under the tabular reserve methodology, the liability for reported claims is based on certain characteristics of the actual reported claimants and their related policy provisions, such as age, length of time disabled, and medical diagnosis, as well as assumptions regarding claim duration, discount rate, and policy benefit offsets. We believe the tabular reserve method is the most accurate to calculate long-term liabilities and allows us to use the most available known facts about each claim. Incurred, but not reported (IBNR) liabilities for future policy benefits for our longer-term products are calculated using the count and severity method using historical patterns of the claims to be reported and the associated claim costs. For Unum US group short-term disability products, an estimate of the value of future payments to be made on claims already submitted, as well as on IBNR claims, is determined in aggregate using a paid loss development method rather than on the individual claimant basis that we use for reported claims on longer-term products. The average length of time between the event triggering a claim under a policy and the final resolution of those claims is much shorter for these products and results in less estimation variability. Liabilities for claims for Unum US group life and accidental death and dismemberment products are related primarily to death claims reported but not yet paid, IBNR death claims, and a liability for waiver of premium benefits in the event the policyholder becomes disabled. The death claim liability is based on the actual face amount to be paid, the IBNR liability is calculated using the count and severity method based on historical patterns of the claims, and the waiver of premium benefits liability is calculated using the tabular reserve methodology. Liabilities for claims related to the group and individual dental and vision products reported in our Unum US and Colonial Life segments have a short claim payout period. As a result, the liabilities, which primarily represent IBNR and a small amount of claims pending payment, are calculated using the paid loss development method. Liabilities for future policy benefits supporting the group products within our Unum International segment are calculated using generally the same methodology that we use for Unum US group disability and group life liabilities. Liabilities for future policy benefits for our Unum UK group life dependent product, which provides an annuity to the beneficiary upon the death of an employee, are calculated using discounted cash flows, based on our assumptions for claim duration and discount rates. The assumptions used in calculating liabilities for future policy benefits for this segment are based on standard country-specific industry experience, adjusted for our own experience. Certain products in the Colonial Life segment and the Unum US voluntary benefits product line have shorter-term benefits, which generally have less estimation variability than our longer-term products because of the shorter claim payout period. Our liabilities for future policy benefits for these lines of business are predominantly determined using the incurred loss development method based on our own experience. The incurred loss development method uses the historical patterns of payments by loss date to predict future claim payments for each loss date. Where the incurred loss development method may not be appropriate, we estimate the incurred claims using an expected claim cost per policy or other measure of exposure. See note 6.
Policyholders' Account Balances	Policyholders' Account Balances: Policyholders' account balances primarily include our universal life and corporate-owned life insurance products. Policyholders' account balances reflect customer deposits and interest credited less cost of insurance, administration expenses, surrender charges, and customer withdrawals. Our unearned revenue reserve, claim reserves and certain other reserves related to our universal life products and corporate-owned life insurance products are also reported as a component of policyholders’ account balances. Policyholders' account balances require loss recognition testing. We perform loss recognition tests on these 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 reporting segment when we perform the loss recognition tests. If the excess of the present value of projected future benefits and claim settlement expenses over the present value of projected future gross premiums is greater than the existing policy reserves less any unearned revenue reserve or value of business acquired, the existing policy reserves would be increased to immediately recognize the insufficiency. This becomes the new basis for reserves going forward, subject to future loss recognition testing. Anticipated investment income, based on our anticipated portfolio yield rates after consideration for defaults and investment expenses, is considered when performing loss recognition testing for long-duration contracts. See note 7.
Policyholders' Funds	Other Policyholders' Funds: Other 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
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. See Note 10.
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 17.
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 12.
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 solutions business, which include 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, policy benefits, and policy benefits - remeasurement gain or loss are presented in our consolidated statements of income net of reinsurance ceded. Ceded liabilities for future policy benefits, policyholders' account balances 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. For ceded reinsurance transactions occurring after January 1, 2021, the transition date of ASU 2018-12, in accordance with the provisions of the ASU related to non-contemporaneous reinsurance, we are required to establish the ceded reserves using an upper-medium grade fixed-income instrument as of the reinsurance transaction date. However, the direct reserves for the reinsured block are calculated using the original discount rate utilized as of the transition date. Both the direct and ceded reserves are then remeasured at each reporting period using a current discount rate reflective of an upper-medium grade fixed-income instrument, with the changes recognized in other comprehensive income(loss). While the total equity impact is neutral, the different original discount rates utilized for direct and ceded reserves result in disproportionate earnings impacts. 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 sheets at December 31, 2023 and 2022 was $549.4 million and $593.5 million. The deferred gain on reinsurance included in other liabilities in our consolidated balance sheets at December 31, 2023 and 2022 was $8.8 million and $3.1 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 market factors, counterparty credit ratings, and collateral received. When calculating our allowance, we apply these market factors 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. The allowance for expected credit losses on reinsurance recoverables was $1.7 million at both December 31, 2023 and 2022. In 2022, the allowance decreased $0.6 million primarily due to changes in the composition of the related receivable . See Note 14.
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, 2023, 2022, and 2021, premium tax expense was $183.5 million, $169.3 million, and $166.0 million, respectively.
Stock-Based Compensation	Stock-Based Compensation : Restricted stock units and stock success units are valued based on the fair value of common stock at the grant date. The fair value of performance units and cash incentive units is based on the Monte-Carlo valuation model. We evaluate whether there are any events which would require an adjustment to the price of common stock at the grant date. No adjustments have been made to any grant date prices for any awards as of December 31, 2023 or 2022. 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. The expense for certain of our awards is subject to accelerated recognition over the implicit service period for employees who have met the criteria for retirement eligibility. Forfeitures of stock-based awards are recognized as they occur. See Note 13.
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 nonvested stock awards on the computation of earnings per share assuming dilution. See Note 12.
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 $244.4 million and $250.2 million at December 31, 2023 and 2022, respectively.

Significant Accounting Polici_2

Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2023
Accounting policies and error corrections [Abstract]
New Accounting Pronouncements and Changes in Accounting Principles	The following table summarizes the changes in stockholders' equity due to the adoption of ASU 2018-12 and the resulting adjusted balances at January 1, 2021: Consolidated Retained Earnings Accumulated Other Comprehensive Income (Loss) Total Stockholders' Equity (in millions of dollars) Balance at December 31, 2020 $ 11,269.6 $ 374.2 $ 10,871.0 Impact of the Adoption of ASU 2018-12 (20.6) (6,684.4) (6,705.0) Balance at January 1, 2021 $ 11,249.0 $ (6,310.2) $ 4,166.0 The following tables summarize the changes in the liability for future policy benefits due to the adoption of ASU 2018-12 and the resulting adjusted balance at January 1, 2021. The removal of shadow adjustments and effect of change in discount rate assumptions are both recorded as transition adjustments to accumulated other comprehensive income (loss) (AOCI) while the adjustments for loss contracts are recorded as a transition adjustment to retained earnings. Unum US Unum International Colonial Life Closed Block Consolidated (in millions of dollars) Balance at December 31, 2020 1 $ 12,184.6 $ 2,969.8 $ 1,977.2 $ 28,572.8 $ 45,704.4 Removal of Shadow Adjustments 2 (1,569.7) (545.8) (44.5) (4,065.6) (6,225.6) Adjustments for Loss Contracts 3 — — 34.9 — 34.9 Effect of Change in Discount Rate Assumptions 2,251.8 779.4 568.6 12,484.8 16,084.6 Other 4 (5.3) — (7.6) — (12.9) Balance at January 1, 2021 12,861.4 3,203.4 2,528.6 36,992.0 55,585.4 Reinsurance Recoverable 5 357.7 132.5 4.4 10,001.4 10,496.0 Balance, Net of Reinsurance, at January 1, 2021 $ 12,503.7 $ 3,070.9 $ 2,524.2 $ 26,990.6 $ 45,089.4 1 We previously reported policy and contract benefits and reserves for future policy and contract benefits liabilities in our consolidated balance sheet as of December 31, 2020 of $1,855.4 million and $49,653.0 million, respectively, resulting in total policyholder liabilities of $51,508.4 million. These balances were reclassified into new line items, future policy benefits and policyholders' account balances, which would have reported balances of $45,704.4 million and $5,804.0 million as of December 31, 2020, respectively, resulting in total policyholder liabilities of $51,508.4 million under the historical accounting method. These balances were reclassified to more closely align with the new disclosure requirements of ASU 2018-12. 2 Shadow adjustments represent the adjustments related to unrealized investment gains and losses previously included in the reserves balance prior to the adoption of ASU 2018-12. 3 Adjustment for loss contracts represents the adjustment for those cohorts whose net premium ratio exceeded 100 percent as of the transition date. For those cohorts, the net premiums were set equal to the gross premiums and the difference was recorded as a transition adjustment to the liability for future policy benefits. 4 This amount reflects the effect of the reclassification of certain unearned premium. This amount was reclassified to more closely align with the presentation of liabilities under ASU 2018-12 and had no impact to stockholders' equity. 5 These amounts represent the portion of reinsurance recoverable related to the liability for future policy benefits. These amounts include the adjustments for the removal of shadow adjustments and for the effect of change in discount rate assumptions for the liability for future policy benefits ceded to third party reinsurers. Unum US Segment Group Disability Group Life and AD&D Individual Disability Voluntary Disability Dental and Vision Total (in millions of dollars) Balance at December 31, 2020 $ 7,409.0 $ 1,123.9 $ 2,485.3 $ 1,154.9 $ 11.5 $ 12,184.6 Removal of Shadow Adjustments (1,025.2) (88.5) (446.1) (9.9) — (1,569.7) Effect of Change in Discount Rate Assumptions 911.9 91.9 728.5 519.5 — 2,251.8 Other — — — (5.3) — (5.3) Balance at January 1, 2021 7,295.7 1,127.3 2,767.7 1,659.2 11.5 12,861.4 Reinsurance Recoverable 58.3 3.0 260.6 35.7 0.1 357.7 Balance, Net of Reinsurance, at January 1, 2021 $ 7,237.4 $ 1,124.3 $ 2,507.1 $ 1,623.5 $ 11.4 $ 12,503.7 Closed Block Segment Long-term Care All Other Total (in millions of dollars) Balance at December 31, 2020 $ 16,283.4 $ 12,289.4 $ 28,572.8 Removal of Shadow Adjustments (3,465.4) (600.2) (4,065.6) Effect of Change in Discount Rate Assumptions 9,922.9 2,561.9 12,484.8 Balance at January 1, 2021 22,740.9 14,251.1 36,992.0 Reinsurance Recoverable 44.4 9,957.0 10,001.4 Balance, Net of Reinsurance, at January 1, 2021 $ 22,696.5 $ 4,294.1 $ 26,990.6 Deferred Acquisition Costs (DAC) The following tables summarize the changes in DAC due to the adoption of ASU 2018-12 and the resulting adjusted balance at January 1, 2021. The removal of shadow adjustments is recorded as a transition adjustment to AOCI. Consolidated Unum US 1 Unum International Colonial Life Total (in millions of dollars) Balance at December 31, 2020 $ 1,168.7 $ 32.0 $ 1,071.9 $ 2,272.6 Removal of Shadow Adjustments 12.3 — 72.8 85.1 Balance at January 1, 2021 $ 1,181.0 $ 32.0 $ 1,144.7 $ 2,357.7 1 The $12.3 million removal of shadow adjustments is related to the Unum US voluntary benefits product line. The following tables present the effect of the adoption of ASU 2018-12 on our historical consolidated financial statements: December 31, 2022 Historical Accounting Method As Adjusted Effect of Change (in millions of dollars) Consolidated Balance Sheets Assets Reinsurance Recoverable $ 10,218.6 $ 9,608.0 $ (610.6) Deferred Acquisition Costs 2,252.3 2,560.0 307.7 Deferred Income Tax 449.8 586.0 136.2 Other Assets 1 1,786.3 1,666.6 (119.7) Total Assets 61,434.9 61,148.5 (286.4) Liabilities Policy and Contract Benefits 2 $ 1,839.8 $ — $ (1,839.8) Reserves for Future Policy and Contract Benefits 2 42,330.2 — (42,330.2) Future Policy Benefits 2 — 38,577.1 38,577.1 Policyholders' Account Balances 2 — 5,740.2 5,740.2 Unearned Premiums 352.7 365.5 12.8 Deferred Income Tax 9.2 25.2 16.0 Total Liabilities 52,237.4 52,413.5 176.1 Stockholders' Equity Accumulated Other Comprehensive Loss $ (2,756.6) $ (3,448.3) $ (691.7) Retained Earnings 12,912.1 13,141.3 229.2 Total Stockholders' Equity 9,197.5 8,735.0 (462.5) 1 The change in other assets is driven by the cost of reinsurance associated with the second phase of our Closed Block individual disability reinsurance transaction which was completed in the first quarter of 2021. In accordance with the provisions of the ASU related to non-contemporaneous reinsurance, we were then required to establish the ceded reserves using an upper-medium grade fixed-income instrument as of the reinsurance transaction date in March 2021 which resulted in higher ceded reserves compared to that which was reported historically. 2 We previously reported policy and contract benefits and reserves for future policy and contract benefits liabilities in our consolidated balance sheet as of December 31, 2022 of $1,839.8 million and $42,330.2 million, respectively, resulting in total policyholder liabilities of $44,170.0 million. These balances were reclassified into new line items, future policy benefits and policyholders' account balances, which would have reported balances of $38,443.2 million and $5,726.8 million, respectively, as of December 31, 2022, resulting in total policyholder liabilities of $44,170.0 million under the historical accounting method. Twelve Months Ended December 31, 2022 Historical Accounting Method As Adjusted Effect of Change (in millions of dollars, except share data and where noted) Consolidated Statements of Income Premium Income $ 9,623.4 $ 9,616.5 $ (6.9) Policy Benefits 1 6,936.7 7,542.1 605.4 Policy Benefits - Remeasurement Gain — (547.5) (547.5) Amortization of Deferred Acquisition Costs 591.0 421.1 (169.9) Other Expenses 1,020.2 1,006.7 (13.5) Income Tax - Deferred (156.3) (130.7) 25.6 Net Income 1,314.2 1,407.2 93.0 Net Income Per Common Share Basic $ 6.55 $ 7.01 $ 0.46 Assuming Dilution $ 6.50 $ 6.96 $ 0.46 Consolidated Statements of Comprehensive Income (Loss) Net Income $ 1,314.2 $ 1,407.2 $ 93.0 Change in Adjustment to Deferred Acquisition Costs and Reserves for Future Policy and Contract Benefits, Net of Reinsurance 4,056.9 — (4,056.9) Change in the Effect of Discount Rate Assumptions on the Liability for Future Policy Benefits, Net of Reinsurance — 8,884.6 8,884.6 Change in Foreign Currency Translation Adjustment (115.2) (116.0) (0.8) Comprehensive Income (Loss) (1,796.5) 3,123.5 4,920.0 Consolidated Statements of Stockholders' Equity Accumulated Other Comprehensive Income (Loss) Balance at Beginning of Year $ 354.1 $ (5,164.6) $ (5,518.7) Other Comprehensive Income (Loss) (3,110.7) 1,716.3 4,827.0 Retained Earnings Balance at Beginning of Year 11,853.2 11,989.4 136.2 Net Income 1,314.2 1,407.2 93.0 Consolidated Statements of Cash Flows Cash Flows from Operating Activities Net Income $ 1,314.2 $ 1,407.2 $ 93.0 Change in Receivables 566.0 590.6 24.6 Change in Deferred Acquisition Costs 34.1 (135.8) (169.9) Change in Insurance Liabilities (282.0) (244.7) 37.3 Change in Income Taxes (58.8) (31.3) 27.5 Amortization of the Cost of Reinsurance 63.8 50.3 (13.5) Other, Net 16.1 17.1 1.0 1 Previously disclosed as Benefits and Change in Reserves for Future Benefits Twelve Months Ended December 31, 2021 Historical Accounting Method As Adjusted Effect of Change (in millions of dollars, except share data and where noted) Consolidated Statements of Income Premium Income $ 9,481.0 $ 9,475.0 $ (6.0) Policy Benefits 1 7,598.6 8,113.3 514.7 Policy Benefits - Remeasurement Gain — (559.9) (559.9) Deferral of Acquisition Costs (508.1) (523.2) (15.1) Amortization of Deferred Acquisition Costs 586.1 452.1 (134.0) Other Expenses 1,008.6 999.3 (9.3) Income Tax - Deferred 26.0 66.8 40.8 Net Income 824.2 981.0 156.8 Net Income Per Common Share Basic $ 4.04 $ 4.80 $ 0.76 Assuming Dilution $ 4.02 $ 4.79 $ 0.77 Consolidated Statements of Comprehensive Income (Loss) Net Income $ 824.2 $ 981.0 $ 156.8 Change in Adjustment to Deferred Acquisition Costs and Reserves for Future Policy and Contract Benefits, Net of Reinsurance 1,195.9 — (1,195.9) Change in the Effect of Discount Rate Assumptions on the Liability for Future Policy Benefits, Net of Reinsurance — 2,361.8 2,361.8 Change in Foreign Currency Translation Adjustment (12.6) (12.8) (0.2) Comprehensive Income (Loss) 804.1 2,126.6 1,322.5 Consolidated Statements of Stockholders' Equity Accumulated Other Comprehensive Income (Loss) Balance at Beginning of Year $ 374.2 $ (6,310.2) $ (6,684.4) Other Comprehensive Income (Loss) (20.1) 1,145.6 1,165.7 Retained Earnings Balance at Beginning of Year 11,269.6 11,249.0 (20.6) Net Income 824.2 981.0 156.8 Consolidated Statements of Cash Flows Cash Flows from Operating Activities Net Income $ 824.2 $ 981.0 $ 156.8 Change in Receivables 678.0 676.1 (1.9) Change in Deferred Acquisition Costs 78.0 (71.1) (149.1) Change in Insurance Liabilities 74.2 37.7 (36.5) Change in Income Taxes 295.3 335.3 40.0 Amortization of the Cost of Reinsurance 79.1 69.8 (9.3) 1 Previously disclosed as Benefits and Change in Reserves for Future Benefits

Fair Values of Financial Inst_2

Fair Values of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2023
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, 2023 Investment Category Fair Value Redemption Term / Redemption Notice Unfunded Commitments (in millions of dollars) (in millions of dollars) Private Credit (a) $ 239.1 Not redeemable $ 128.2 44.5 Quarterly / 90 days notice 8.6 Total Private Credit 283.6 136.8 Private Equity (b) 543.9 Not redeemable 410.6 28.0 Initial 5.5 year lock on each new investment / Quarterly after 5.5 year lock with 90 days notice 16.6 Total Private Equity 571.9 427.2 Real Assets (c) 437.5 Not redeemable 239.1 33.2 Quarterly / 90 days notice — Total Real Assets 470.7 239.1 Total Partnerships $ 1,326.2 $ 803.1 December 31, 2022 Investment Category Fair Value Redemption Term / Redemption Notice Unfunded Commitments (in millions of dollars) (in millions of dollars) Private Credit (a) $ 239.3 Not redeemable $ 90.9 35.7 Initial 2 year lock on each new investment / Quarterly after 2 year lock with 90 days notice 13.4 Total Private Credit 275.0 104.3 Private Equity (b) 453.6 Not redeemable 377.2 31.7 Initial 5.5 year lock on each new investment / Quarterly after 5.5 year lock with 90 days notice 39.1 Total Private Equity 485.3 416.3 Real Assets (c) 373.9 Not redeemable 256.3 60.1 Quarterly / 90 days notice — Total Real Assets 434.0 256.3 Total Partnerships $ 1,194.3 $ 776.9 (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, 2023, the estimated remaining life of the investments that do not allow for redemptions is approximately 74 percent in the next 3 years, 21 percent during the period from 3 to 5 years, 3 percent during the period from 5 to 10 years, and 2 percent during the period from 10 to 15 years. (b) Private Equity - The limited partnerships described in this category employ various strategies generally investing in controlling or minority control equity positions directly in companies and/or assets across various industries (including manufacturing, healthcare, energy, business services, technology, materials, and retail), primarily in private markets within North America and, to a lesser extent, outside of North America. As of December 31, 2023, the estimated remaining life of the investments that do not allow for redemptions is approximately 34 percent in the next 3 years, 31 percent during the period from 3 to 5 years, 26 percent during the period from 5 to 10 years, and 9 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, 2023, the estimated remaining life of the investments that do not allow for redemptions is approximately 22 percent in the next 3 years, 35 percent during the period from 3 to 5 years, 42 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, 2023 Level 1 Level 2 Level 3 NAV Total (in millions of dollars) Assets Fixed Maturity Securities United States Government and Government Agencies and Authorities $ — $ 624.8 $ — $ — $ 624.8 States, Municipalities, and Political Subdivisions — 3,678.4 — — 3,678.4 Foreign Governments — 890.7 — — 890.7 Public Utilities 301.3 5,020.3 — — 5,321.6 Mortgage/Asset-Backed Securities — 611.2 32.9 — 644.1 All Other Corporate Bonds 3,985.2 21,562.1 123.4 — 25,670.7 Redeemable Preferred Stocks — 3.6 — — 3.6 Total Fixed Maturity Securities 4,286.5 32,391.1 156.3 — 36,833.9 Other Long-term Investments Derivatives Forwards — 47.5 — — 47.5 Foreign Exchange Contracts — 52.4 — — 52.4 Total Derivatives — 99.9 — — 99.9 Perpetual Preferred and Equity Securities — 10.3 21.6 — 31.9 Private Equity Partnerships — — — 1,326.2 1,326.2 Total Other Long-term Investments — 110.2 21.6 1,326.2 1,458.0 Total Financial Instrument Assets Carried at Fair Value $ 4,286.5 $ 32,501.3 $ 177.9 $ 1,326.2 $ 38,291.9 Liabilities Other Liabilities Derivatives Forwards $ — $ 78.0 $ — $ — $ 78.0 Foreign Exchange Contracts — 38.2 — — 38.2 Embedded Derivative in Modified Coinsurance Arrangement — — 1.5 — 1.5 Total Derivatives — 116.2 1.5 — 117.7 Total Financial Instrument Liabilities Carried at Fair Value $ — $ 116.2 $ 1.5 $ — $ 117.7 December 31, 2022 Level 1 Level 2 Level 3 NAV Total (in millions of dollars) Assets Fixed Maturity Securities United States Government and Government Agencies and Authorities $ 81.7 $ 416.5 $ — $ — $ 498.2 States, Municipalities, and Political Subdivisions 8.7 3,448.3 0.2 — 3,457.2 Foreign Governments — 827.1 — — 827.1 Public Utilities 160.1 4,796.8 — — 4,956.9 Mortgage/Asset-Backed Securities — 551.3 22.0 — 573.3 All Other Corporate Bonds 4,268.6 20,097.3 158.7 — 24,524.6 Redeemable Preferred Stocks — 3.5 — — 3.5 Total Fixed Maturity Securities 4,519.1 30,140.8 180.9 — 34,840.8 Other Long-term Investments Derivatives Forwards — 5.6 — — 5.6 Foreign Exchange Contracts — 83.5 — — 83.5 Total Derivatives — 89.1 — — 89.1 Perpetual Preferred and Equity Securities — 9.6 16.2 — 25.8 Private Equity Partnerships — — — 1,194.3 1,194.3 Total Other Long-term Investments — 98.7 16.2 1,194.3 1,309.2 Total Financial Instrument Assets Carried at Fair Value $ 4,519.1 $ 30,239.5 $ 197.1 $ 1,194.3 $ 36,150.0 Liabilities Other Liabilities Derivatives Forwards $ — $ 48.5 $ — $ — $ 48.5 Foreign Exchange Contracts — 25.5 — — 25.5 Embedded Derivative in Modified Coinsurance Arrangement — — 13.9 — 13.9 Total Derivatives — 74.0 13.9 — 87.9 Total Financial Instrument Liabilities Carried at Fair Value $ — $ 74.0 $ 13.9 $ — $ 87.9
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, 2023 Fair Value Beginning Total Realized and Purchases Sales/Maturities Level 3 Transfers Fair Value End of Change in Unrealized Earnings OCI Into Out of OCI Earnings (in millions of dollars) Fixed Maturity Securities States, Municipalities, and Political Subdivisions $ 0.2 $ — $ — $ — $ — $ — $ (0.2) $ — $ — $ — Public Utilities — 0.1 (0.1) — (50.5) 50.5 — — — — Mortgage/Asset-Backed Securities 22.0 — (0.2) 20.0 (0.5) 0.4 (8.8) 32.9 (0.2) — All Other Corporate Bonds 158.7 (5.0) (15.8) 1.5 (334.1) 385.0 (66.9) 123.4 (15.8) — Total Fixed Maturity Securities 180.9 (4.9) (16.1) 21.5 (385.1) 435.9 (75.9) 156.3 (16.0) — Perpetual Preferred and Equity Securities 16.2 0.6 — 4.8 — — — 21.6 — 0.6 Embedded Derivative in Modified Coinsurance Arrangement (13.9) 12.4 — — — — — (1.5) — 12.4 Year Ended December 31, 2022 Fair Value Beginning Total Realized and Purchases Sales/Maturities Level 3 Transfers Fair Value End of Change in Unrealized Earnings OCI Into Out of OCI Earnings (in millions of dollars) Fixed Maturity Securities States, Municipalities, and Political Subdivisions $ 13.4 $ — $ (0.1) $ — $ — $ 0.3 $ (13.4) $ 0.2 $ (0.1) $ — Foreign Governments 20.8 — (0.8) — (20.0) — — — (0.8) — Public Utilities 44.5 — (2.8) — (12.8) 15.6 (44.5) — (2.8) — Mortgage/Asset-Backed Securities 187.2 — (0.3) 20.7 (10.6) — (175.0) 22.0 (0.3) — All Other Corporate Bonds 861.5 — (32.0) 25.3 (102.3) 161.9 (755.7) 158.7 (32.0) — Total Fixed Maturity Securities 1,127.4 — (36.0) 46.0 (145.7) 177.8 (988.6) 180.9 (36.0) — Perpetual Preferred and Equity Securities 5.8 3.0 — 7.1 — 0.3 — 16.2 — 3.0 Embedded Derivative in Modified Coinsurance Arrangement (30.1) 16.2 — — — — — (13.9) — 16.2
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, 2023 Fair Value Valuation Method Unobservable Input Range/Weighted Average (in millions of dollars) Fixed Maturity Securities All Other Corporate Bonds - Private $ 15.9 Market Approach Volatility of Credit Market Convention (a) (b) 5.00% - 5.00% / 5.00% Priced at Par Value Perpetual Preferred and Equity Securities 21.6 Market Approach Market Convention (b) Priced at Cost, Owner's Equity, or Most Recent Round Embedded Derivative in Modified Coinsurance Arrangement (1.5) Discounted Cash Flows Projected Liability Cash Flows Weighted Spread of Swap Curve (c) Actuarial Assumptions 0.2% December 31, 2022 Fair Value Valuation Method Unobservable Input Range/Weighted Average (in millions of dollars) Fixed Maturity Securities All Other Corporate Bonds - Private $ 15.3 Market Approach Volatility of Credit Market Convention (a) (b) 5.41% - 5.41% / 5.41% Priced at Par Value Perpetual Preferred and Equity Securities 16.2 Market Approach Market Convention (b) Priced at Cost, Owner's Equity, or Most Recent Round Embedded Derivative in Modified Coinsurance Arrangement (13.9) Discounted Cash Flows Projected Liability Cash Flows Weighted Spread of Swap Curve (c) Actuarial Assumptions 0.6% (a) Represents basis point adjustments for credit-specific factors (b) Represents a decision to price based on par value, cost, owner's equity, or the price of the most recent capital funding round when limited data is available (c) Represents various actuarial assumptions required to derive the liability cash flows. Fair value of embedded derivative is most often driven by the change in the weighted average credit spread to the swap curve for the assets backing the hypothetical loan
Carrying Amount and Fair Value of Financial Instruments	The following table presents the carrying amounts and estimated fair values of our financial instruments not measured at fair value and indicates the level in the fair value hierarchy of the estimated fair value measurement based on the observability of the inputs used: December 31, 2023 Estimated Fair Value Level 1 Level 2 Level 3 Total Carrying Value (in millions of dollars) Assets Mortgage Loans $ — $ 2,070.7 $ — $ 2,070.7 $ 2,318.2 Policy Loans — — 3,696.3 3,696.3 3,620.2 Other Long-term Investments Miscellaneous Long-term Investments — 15.7 0.3 16.0 16.0 Total Financial Instrument Assets Not Carried at Fair Value $ — $ 2,086.4 $ 3,696.6 $ 5,783.0 $ 5,954.4 Liabilities Long-term Debt $ 2,629.1 $ 598.8 $ — $ 3,227.9 $ 3,430.4 Other Liabilities Unfunded Commitments — 0.2 — 0.2 0.2 Payable for Collateral on FHLB Funding Agreements — 64.5 — 64.5 64.5 Total Financial Instrument Liabilities Not Carried at Fair Value $ 2,629.1 $ 663.5 $ — $ 3,292.6 $ 3,495.1 December 31, 2022 Estimated Fair Value Level 1 Level 2 Level 3 Total Carrying Value (in millions of dollars) Assets Mortgage Loans $ — $ 2,159.5 $ — $ 2,159.5 $ 2,435.4 Policy Loans — — 3,677.0 3,677.0 3,601.2 Other Long-term Investments Miscellaneous Long-term Investments — 17.1 1.3 18.4 18.4 Total Financial Instrument Assets Not Carried at Fair Value $ — $ 2,176.6 $ 3,678.3 $ 5,854.9 $ 6,055.0 Liabilities Long-term Debt $ 2,288.9 $ 783.1 $ — $ 3,072.0 $ 3,427.8 Other Liabilities Unfunded Commitments — 0.7 — 0.7 0.7 Payable for Collateral on FHLB Funding Agreements — 99.1 — 99.1 99.1 Total Financial Instrument Liabilities Not Carried at Fair Value $ 2,288.9 $ 882.9 $ — $ 3,171.8 $ 3,527.6

Investments (Tables)

Investments (Tables)	12 Months Ended
	Dec. 31, 2023
Investments, Debt and Equity Securities [Abstract]
Amortized Cost and Fair Values of Securities by Security Type	At December 31, 2023 and 2022, 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, 2023 Amortized Cost, Gross of ACL 1 ACL 1 Gross Gross Fair (in millions of dollars) United States Government and Government Agencies and Authorities $ 618.6 $ — $ 25.3 $ 19.1 $ 624.8 States, Municipalities, and Political Subdivisions 4,041.3 — 135.3 498.2 3,678.4 Foreign Governments 982.1 — 29.8 121.2 890.7 Public Utilities 5,398.2 — 217.1 293.7 5,321.6 Mortgage/Asset-Backed Securities 658.0 — 10.1 24.0 644.1 All Other Corporate Bonds 26,708.4 2.2 771.8 1,807.3 25,670.7 Redeemable Preferred Stocks 4.0 — — 0.4 3.6 Total Fixed Maturity Securities $ 38,410.6 $ 2.2 $ 1,189.4 $ 2,763.9 $ 36,833.9 December 31, 2022 Amortized Cost, Gross of ACL 1 ACL 1 Gross Gross Fair (in millions of dollars) United States Government and Government Agencies and Authorities $ 503.8 $ — $ 20.3 $ 25.9 $ 498.2 States, Municipalities, and Political Subdivisions 4,006.0 — 87.1 635.9 3,457.2 Foreign Governments 908.1 — 34.9 115.9 827.1 Public Utilities 5,170.9 — 141.0 355.0 4,956.9 Mortgage/Asset-Backed Securities 592.1 — 8.2 27.0 573.3 All Other Corporate Bonds 26,640.3 — 452.1 2,567.8 24,524.6 Redeemable Preferred Stocks 4.0 — — 0.5 3.5 Total Fixed Maturity Securities $ 37,825.2 $ — $ 743.6 $ 3,728.0 $ 34,840.8 1 Allowance for Credit Losses
Schedule of Unrealized Loss on Investments	The following charts indicate the length of time our fixed maturity securities have been in a gross unrealized loss position. December 31, 2023 Less Than 12 Months 12 Months or Greater Fair Gross Fair Gross (in millions of dollars) United States Government and Government Agencies and Authorities $ 118.8 $ 0.7 $ 197.3 $ 18.4 States, Municipalities, and Political Subdivisions 128.0 4.0 2,035.1 494.2 Foreign Governments 149.9 3.3 312.9 117.9 Public Utilities 373.7 10.4 1,720.6 283.3 Mortgage/Asset-Backed Securities 60.3 2.5 316.7 21.5 All Other Corporate Bonds 1,483.8 26.8 14,215.2 1,780.5 Redeemable Preferred Stocks — — 3.6 0.4 Total Fixed Maturity Securities $ 2,314.5 $ 47.7 $ 18,801.4 $ 2,716.2 December 31, 2022 Less Than 12 Months 12 Months or Greater Fair Gross Fair Gross (in millions of dollars) United States Government and Government Agencies and Authorities $ 246.6 $ 22.6 $ 12.2 $ 3.3 States, Municipalities, and Political Subdivisions 1,920.1 476.1 346.6 159.8 Foreign Governments 160.1 47.9 176.9 68.0 Public Utilities 2,242.2 252.0 255.2 103.0 Mortgage/Asset-Backed Securities 386.6 27.0 0.1 — All Other Corporate Bonds 15,865.6 1,799.7 2,194.1 768.1 Redeemable Preferred Stocks 3.5 0.5 — — Total Fixed Maturity Securities $ 20,824.7 $ 2,625.8 $ 2,985.1 $ 1,102.2
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, 2023 Amortized Cost, Net of ACL 1 Unrealized Gain Position Unrealized Loss Position Gross Gain Fair Value Gross Loss Fair Value (in millions of dollars) 1 year or less $ 935.0 $ 0.9 $ 140.8 $ 7.5 $ 787.6 Over 1 year through 5 years 7,594.4 128.2 2,685.7 179.0 4,857.9 Over 5 years through 10 years 9,430.3 372.1 4,100.0 610.8 5,091.6 Over 10 years 19,790.7 678.1 8,524.4 1,942.6 10,001.8 37,750.4 1,179.3 15,450.9 2,739.9 20,738.9 Mortgage/Asset-Backed Securities 658.0 10.1 267.1 24.0 377.0 Total Fixed Maturity Securities $ 38,408.4 $ 1,189.4 $ 15,718.0 $ 2,763.9 $ 21,115.9 December 31, 2022 Amortized Cost, Net of ACL 1 Unrealized Gain Position Unrealized Loss Position Gross Gain Fair Value Gross Loss Fair Value (in millions of dollars) 1 year or less $ 1,133.5 $ 2.9 $ 339.1 $ 5.7 $ 791.6 Over 1 year through 5 years 7,090.8 86.7 1,953.2 238.4 4,985.9 Over 5 years through 10 years 10,096.7 294.8 3,538.9 863.8 5,988.8 Over 10 years 18,912.1 351.0 5,013.2 2,593.1 11,656.8 37,233.1 735.4 10,844.4 3,701.0 23,423.1 Mortgage/Asset-Backed Securities 592.1 8.2 186.6 27.0 386.7 Total Fixed Maturity Securities $ 37,825.2 $ 743.6 $ 11,031.0 $ 3,728.0 $ 23,809.8 1 Allowance for Credit Losses
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, 2023: Gross Unrealized Loss Fair Value Gross Unrealized Gain Amount Percent of Total Gross Unrealized Loss (in millions of dollars) Investment-Grade $ 35,344.9 $ 1,169.1 $ 2,660.3 96.3 % Below-Investment-Grade 1,489.0 20.3 103.6 3.7 Total Fixed Maturity Securities $ 36,833.9 $ 1,189.4 $ 2,763.9 100.0 %
Debt Securities, Available-for-sale, Allowance for Credit Loss	The following tables present a rollforward of the allowance for credit losses on available-for-sale fixed maturity securities, which were classified as "all other corporate bonds" during the year ended December 31, 2023 and "public utilities" during the year ended December 31, 2022, respectively. Year Ended December 31 2023 2022 (in millions of dollars) Balance, beginning of period $ — $ — Credit losses on securities for which credit losses were not previously recorded 2.2 4.6 Change in allowance on securities disposed during the period — (4.6) Balance, end of period $ 2.2 $ —
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 2023 2022 2021 (in millions of dollars) Income Tax Credits $ 1.1 $ 8.0 $ 21.6 Amortization, Net of Tax (0.5) (5.9) (15.0) Income Tax Benefit $ 0.6 $ 2.1 $ 6.6
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 2023 2022 (in millions of dollars) Carrying Percent of Carrying Percent of Amount Total Amount Total Property Type Apartment $ 685.8 29.6 % $ 688.6 28.3 % Industrial 706.0 30.5 745.3 30.6 Office 379.9 16.4 423.0 17.4 Retail 503.9 21.7 534.5 21.9 Other 42.6 1.8 44.0 1.8 Total $ 2,318.2 100.0 % $ 2,435.4 100.0 % Region New England $ 55.1 2.4 % $ 52.4 2.2 % Mid-Atlantic 155.1 6.7 192.4 7.9 East North Central 314.4 13.6 313.0 12.9 West North Central 163.5 7.0 181.4 7.4 South Atlantic 553.0 23.8 539.3 22.1 East South Central 110.7 4.8 101.8 4.2 West South Central 200.9 8.7 212.6 8.7 Mountain 282.7 12.2 298.7 12.3 Pacific 482.8 20.8 543.8 22.3 Total $ 2,318.2 100.0 % $ 2,435.4 100.0 %
Schedule of Participating Mortgage Loans by Internal Credit Rating and Loan to Value	The following tables present information about mortgage loans by the applicable internal quality indicators: December 31 2023 2022 (in millions of dollars) Carrying Amount Percent of Total Carrying Amount Percent of Total Internal Mortgage Rating AA $ 85.2 3.7 % $ 92.3 3.8 % A 942.5 40.6 843.9 34.6 BBB 1,249.5 53.9 1,458.0 59.9 BB 41.0 1.8 41.2 1.7 Total $ 2,318.2 100.0 % $ 2,435.4 100.0 % Loan-to-Value Ratio 1 <= 65% $ 1,409.9 60.8 % $ 1,389.6 57.0 % > 65% <= 75% 707.0 30.5 937.2 38.5 > 75% <= 85% 136.5 5.9 75.0 3.1 > 85% 64.8 2.8 33.6 1.4 Total $ 2,318.2 100.0 % $ 2,435.4 100.0 % 1 Loan-to-Value Ratio utilizes the most recent internal valuation of the property
Mortgage Loans by Credit Quality Indicators	The following tables present the amortized cost of our mortgage loans by year of origination and internal quality indicators for the years ended December 31, 2023 and 2022: Year Ended December 31, 2023 Prior to 2019 2019 2020 2021 2022 2023 Total (in millions of dollars) Internal Mortgage Rating AA $ 74.3 $ 11.0 $ — $ — $ — $ — $ 85.3 A 589.0 100.3 94.1 100.1 23.2 38.0 944.7 BBB 618.4 224.8 71.4 248.0 64.4 29.2 1,256.2 BB 42.2 — — — — — 42.2 Total Amortized Cost 1,323.9 336.1 165.5 348.1 87.6 67.2 2,328.4 Allowance for credit losses (6.3) (1.3) (0.6) (1.0) (0.6) (0.4) (10.2) Carrying Amount $ 1,317.6 $ 334.8 $ 164.9 $ 347.1 $ 87.0 $ 66.8 $ 2,318.2 Loan-to-Value Ratio 1 <=65% $ 908.3 $ 197.7 $ 116.4 $ 145.2 $ 16.2 $ 30.0 $ 1,413.8 >65<=75% 252.1 138.4 40.8 171.0 71.4 37.2 710.9 >75%<=85% 97.3 — 8.3 31.9 — — 137.5 >85% 66.2 — — — — — 66.2 Total Amortized Cost 1,323.9 336.1 165.5 348.1 87.6 67.2 2,328.4 Allowance for credit losses (6.3) (1.3) (0.6) (1.0) (0.6) (0.4) (10.2) Carrying Amount $ 1,317.6 $ 334.8 $ 164.9 $ 347.1 $ 87.0 $ 66.8 $ 2,318.2 1 Loan-to-Value Ratio utilizes the most recent internal valuation of the property Year Ended December 31, 2022 Prior to 2018 2018 2019 2020 2021 2022 Total (in millions of dollars) Internal Mortgage Rating AA $ 53.8 $ 27.5 $ 11.1 $ — $ — $ — $ 92.4 A 485.0 123.3 96.8 35.9 80.6 24.0 845.6 BBB 534.0 219.8 236.9 134.0 275.8 64.6 1,465.1 BB 35.7 5.9 — — — — 41.6 Total Amortized Cost 1,108.5 376.5 344.8 169.9 356.4 88.6 2,444.7 Allowance for credit losses (4.3) (1.8) (1.3) (0.6) (0.8) (0.5) (9.3) Carrying Amount $ 1,104.2 $ 374.7 $ 343.5 $ 169.3 $ 355.6 $ 88.1 $ 2,435.4 Loan-to-Value Ratio 1 <=65% $ 782.6 $ 189.0 $ 193.9 $ 81.3 $ 128.9 $ 16.9 $ 1,392.6 >65<=75% 230.2 181.6 150.9 80.1 227.5 71.7 942.0 >75%<=85% 67.5 — — 8.5 — — 76.0 >85% 28.2 5.9 — — — — 34.1 Total Amortized Cost 1,108.5 376.5 344.8 169.9 356.4 88.6 2,444.7 Allowance for credit losses (4.3) (1.8) (1.3) (0.6) (0.8) (0.5) (9.3) Carrying Amount $ 1,104.2 $ 374.7 $ 343.5 $ 169.3 $ 355.6 $ 88.1 $ 2,435.4 1 Loan-to-Value Ratio utilizes the most recent internal valuation of the property
Financing Receivable, Allowance for Credit Loss	The following tables present a roll forward of allowance for expected credit losses by loan-to-value ratio for the years ended December 31, 2023 and 2022: Year Ended December 31, 2023 Beginning of Period Current Period Provisions Write-Offs Recoveries End of Period (in millions of dollars) Loan-to-Value Ratio 1 <=65% $ 3.0 $ 0.8 $ — $ — $ 3.8 >65<=75% 4.7 (0.9) — — 3.8 >75%<=85% 1.1 0.1 — — 1.2 >85% 0.5 0.9 — — 1.4 Total $ 9.3 $ 0.9 $ — $ — $ 10.2 Year Ended December 31, 2022 Beginning of Period Current Period Provisions Write-Offs Recoveries End of Period (in millions of dollars) Loan-to-Value Ratio 1 <=65% $ 2.6 $ 0.4 $ — $ — $ 3.0 >65<=75% 4.7 — — — 4.7 >75%<=85% 0.7 0.4 — — 1.1 >85% 0.3 0.2 — — 0.5 Total $ 8.3 $ 1.0 $ — $ — $ 9.3 1 Loan-to-Value Ratio utilizes the most recent internal valuation of the property
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 2023 2022 Overnight and Continuous (in millions of dollars) Borrowings United States Government and Government Agencies and Authorities $ — $ 0.3 Public Utilities 1.8 6.3 All Other Corporate Bonds 61.3 81.9 Total Borrowings $ 63.1 $ 88.5 Gross Amount of Recognized Liability for Securities Lending Transactions 63.1 88.5 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 2023 2022 (in millions of dollars) Carrying Value of FHLB Common Stock $ 15.7 $ 17.1 Advances from FHLB 64.5 99.1 Carrying Value of Collateral Posted to FHLB Fixed Maturity Securities $ 589.0 $ 527.1 Commercial Mortgage Loans 986.8 801.9 Total Carrying Value of Collateral Posted to FHLB $ 1,575.8 $ 1,329.0
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, 2023 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 $ 99.9 $ — $ 99.9 $ (91.9) $ (6.4) $ 1.6 Securities Lending 72.0 — 72.0 (8.9) (63.1) — Total $ 171.9 $ — $ 171.9 $ (100.8) $ (69.5) $ 1.6 Financial Liabilities: Derivatives $ 116.2 $ — $ 116.2 $ (109.4) $ — $ 6.8 Securities Lending 63.1 — 63.1 (63.1) — — Total $ 179.3 $ — $ 179.3 $ (172.5) $ — $ 6.8 December 31, 2022 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 $ 89.1 $ — $ 89.1 $ (38.0) $ (49.4) $ 1.7 Securities Lending 152.4 — 152.4 (63.9) (88.5) — Total $ 241.5 $ — $ 241.5 $ (101.9) $ (137.9) $ 1.7 Financial Liabilities: Derivatives $ 74.0 $ — $ 74.0 $ (73.2) $ — $ 0.8 Securities Lending 88.5 — 88.5 (88.5) — — Total $ 162.5 $ — $ 162.5 $ (161.7) $ — $ 0.8
Net Investment Income	Net investment income reported in our consolidated statements of income is presented below. Year Ended December 31 2023 2022 2021 (in millions of dollars) Fixed Maturity Securities $ 1,853.7 $ 1,849.8 $ 1,888.2 Derivatives 45.1 57.8 68.6 Mortgage Loans 92.5 101.5 105.0 Policy Loans 20.8 20.0 19.7 Other Long-term Investments Perpetual Preferred Securities 1 2.5 5.0 6.9 Private Equity Partnerships 2 78.1 110.1 165.4 Other 9.2 9.4 5.5 Short-term Investments 68.7 20.0 1.3 Gross Investment Income 2,170.6 2,173.6 2,260.6 Less Investment Expenses 61.8 39.4 35.1 Less Investment Income on Participation Fund Account Assets 12.1 12.0 12.3 Net Investment Income $ 2,096.7 $ 2,122.2 $ 2,213.2 1 The net unrealized gain (loss) recognized in net investment income for the year ended December 31, 2023 related to perpetual preferred securities still held at December 31, 2023 was nominal . The net unrealized gain (loss) recognized in net investment income for the years ended December 31, 2022 and 2021 related to perpetual preferred securities still held at year-end was $2.8 million and $4.4 million, respectively. 2 The net unrealized gain recognized in net investment income for the year ended December 31, 2023 related to private equity partnerships still held at December 31, 2023 was $102.9 million, reduced by net management fees and partnership expenses of $(24.8) million. For the years ended December 31, 2022 and 2021, the net unrealized gain recognized in net investment income related to private equity partnerships still held at year-end was $124.1 million and $177.7 million, respectively, reduced by net management fees and partnership expenses of $(14.0) million and $(12.3) million, respectively. See Note 2 for further discussion of private equity partnerships.	[1]
Realized Investment Gains and Losses Reported in Consolidated Statements of Income	Investment gains and losses are as follows: Year Ended December 31 2023 2022 2021 (in millions of dollars) Fixed Maturity Securities Gross Gains on Sales 1 $ 4.4 $ 2.3 $ 76.2 Gross Losses on Sales (53.1) (28.8) (11.5) Credit Losses (2.2) (4.6) (9.3) Mortgage Loans and Other Invested Assets Gross Gains on Sales 6.0 1.4 5.8 Gross Losses on Sales (1.0) — — Impairment Loss (3.0) — — Change in Allowance for Credit Losses (0.9) (1.0) 4.7 Embedded Derivative in Modified Coinsurance Arrangement 12.4 16.2 9.7 All Other Derivatives (0.6) 2.6 3.1 Foreign Currency Transactions 2.0 (3.8) (2.0) Net Investment Gain (Loss) $ (36.0) $ (15.7) $ 76.7 1
[1]The net unrealized gain recognized in net investment income for the year ended December 31, 2023 related to private equity partnerships still held at December 31, 2023 was $102.9 million, reduced by net management fees and partnership expenses of $(24.8) million. For the years ended December 31, 2022 and 2021, the net unrealized gain recognized in net investment income related to private equity partnerships still held at year-end was $124.1 million and $177.7 million, respectively, reduced by net management fees and partnership expenses of $(14.0) million and $(12.3) million, respectively. See Note 2 for further discussion of private equity partnerships.

Derivative Financial Instrume_2

Derivative Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2023
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 2023 2022 (in millions of dollars) Carrying Value of Collateral Received from Counterparties Cash $ 11.1 $ 49.4 Fixed Maturity Securities 26.3 — $ 37.4 $ 49.4 Carrying Value of Collateral Posted to Counterparties Cash $ — $ 5.1 Fixed Maturity Securities 39.8 39.6 $ 39.8 $ 44.7
Fair Value Hedges Carrying Amount of Hedged Assets and Liabilities and Cumulative Basis Adjustments	The following table summarizes the carrying amount of hedged assets and the related cumulative basis adjustments related to our fair value hedges: Carrying Amount of Hedged Assets Cumulative Amount of Fair Value Hedging Adjustment Included in the Carrying Amount of the Hedged Assets December 31, 2023 December 31, 2022 December 31, 2023 December 31, 2022 (in millions of dollars) Fixed maturity securities: Receive fixed functional currency interest, pay fixed foreign currency interest $ 529.2 $ 394.4 $ (6.1) $ (24.8)
Location and Fair Values of Derivative Financial Instruments	The following tables summarize the notional amounts and fair values of derivative financial instruments, as reported in our consolidated balance sheets. Derivative assets are included in other long-term investments, while derivative liabilities are included in other liabilities within our consolidated balance sheets. The notional amounts represent the basis upon which our counterparty pay and receive amounts are calculated. December 31, 2023 Derivative Assets Derivative Liabilities Notional Fair Fair (in millions of dollars) Designated as Hedging Instruments Cash Flow Hedges Forward Benchmark Interest Rate Locks $ 1,905.0 $ 44.5 $ 77.8 Foreign Currency Interest Rate Swaps 149.5 14.2 4.5 Total Cash Flow Hedges 2,054.5 58.7 82.3 Fair Value Hedges Foreign Currency Interest Rate Swaps 642.5 38.2 16.7 Total Designated as Hedging Instruments $ 2,697.0 $ 96.9 $ 99.0 Not Designated as Hedging Instruments Foreign Currency Forwards $ 52.5 $ 3.0 $ 0.2 Foreign Currency Interest Rate Swaps 132.0 — 17.0 Total Return Swaps 102.2 — — Embedded Derivative in Modified Coinsurance Arrangement — — 1.5 Total Not Designated as Hedging Instruments $ 286.7 $ 3.0 $ 18.7 Total Derivatives $ 2,983.7 $ 99.9 $ 117.7 December 31, 2022 Derivative Assets Derivative Liabilities Notional Fair Fair (in millions of dollars) Designated as Hedging Instruments Cash Flow Hedges Forward Benchmark Interest Rate Locks $ 764.0 $ 1.6 $ 48.4 Foreign Currency Interest Rate Swaps 168.9 17.5 3.1 Total Cash Flow Hedges 932.9 19.1 51.5 Fair Value Hedges Foreign Currency Interest Rate Swaps 557.8 66.0 5.4 Total Designated as Hedging Instruments $ 1,490.7 $ 85.1 $ 56.9 Not Designated as Hedging Instruments Foreign Currency Forwards $ 54.3 $ 4.0 $ 0.1 Foreign Currency Interest Rate Swaps 132.0 — 17.0 Total Return Swaps 76.9 — — Embedded Derivative in Modified Coinsurance Arrangement — — 13.9 Total Not Designated as Hedging Instruments $ 263.2 $ 4.0 $ 31.0 Total Derivatives $ 1,753.9 $ 89.1 $ 87.9
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, 2023 Net Investment Income Net 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 $ 2,096.7 $ (36.0) $ 194.8 Gain (Loss) on Cash Flow Hedging Relationships Interest Rate Swaps: Hedged items 198.6 0.8 2.9 Derivatives Designated as Hedging Instruments 35.2 — — Foreign Exchange Contracts: Hedged items 9.6 0.4 — Derivatives Designated as Hedging Instruments — (0.4) — Forward Benchmark Interest Rate Locks: Hedged items 18.5 — — Derivatives Designated as Hedging Instruments (0.5) — — Gain (Loss) on Fair Value Hedging Relationships Foreign Exchange Contracts: Hedged items 14.5 18.7 — Derivatives Designated as Hedging Instruments 11.1 (18.7) — Year Ended December 31, 2022 Net Investment Income Net 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 $ 2,122.2 $ (15.7) $ 188.5 Gain (Loss) on Cash Flow Hedging Relationships Interest Rate Swaps: Hedged items 200.0 — 2.9 Derivatives Designated as Hedging Instruments 51.0 — — Foreign Exchange Contracts: Hedged items 12.3 (2.3) — Derivatives Designated as Hedging Instruments (0.8) 1.8 — Forward Benchmark Interest Rate Locks: Hedged items 0.5 — — Derivatives Designated as Hedging Instruments — — — Gain (Loss) on Fair Value Hedging Relationships Foreign Exchange Contracts: Hedged items 11.6 (26.8) — Derivatives Designated as Hedging Instruments 7.3 26.8 — Year Ended December 31, 2021 Net Investment Income Net 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 $ 2,213.2 $ 76.7 $ 185.0 Gain (Loss) on Cash Flow Hedging Relationships Interest Rate Swaps: Hedged items 220.4 2.7 29.2 Derivatives Designated as Hedging Instruments 64.6 2.0 5.0 Foreign Exchange Contracts: Hedged items 13.0 (0.1) — Derivatives Designated as Hedging Instruments 1.8 (0.1) — Gain (Loss) on Fair Value Hedging Relationships Foreign Exchange Contracts: Hedged items 9.8 (22.3) — Derivatives Designated as Hedging Instruments 4.6 22.3 —
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 2023 2022 2021 (in millions of dollars) Gain (Loss) Recognized in Other Comprehensive Income (Loss) on Derivatives Forwards $ (22.5) $ (49.8) $ (0.6) Foreign Exchange Contracts (4.3) 7.4 2.2 Total $ (26.8) $ (42.4) $ 1.6
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 2023 2022 2021 (in millions of dollars) Net Investment Gain (Loss) Credit Default Swaps $ — $ — $ (0.3) Foreign Exchange Contracts (0.6) 2.7 3.4 Embedded Derivative in Modified Coinsurance Arrangement 12.4 16.2 9.7 Total $ 11.8 $ 18.9 $ 12.8 Other Expenses (Gain) Loss on Total Return Swaps $ (13.6) $ 18.9 $ (8.5)

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Income (Tables)	12 Months Ended
	Dec. 31, 2023
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss)	Components of our accumulated other comprehensive loss, after tax, and related changes are as follows: Net Unrealized Gain (Loss) on Securities Effect of Change in Discount Rate Assumptions on the LFPB 1 Net Gain (Loss) on Hedges Foreign Currency Translation Adjustment Unrecognized Pension and Postretirement Benefit Costs Total (in millions of dollars) Balance at January 1, 2021, As Adjusted $ 5,315.8 $ (10,932.5) $ 97.8 $ (261.3) $ (530.0) $ (6,310.2) Other Comprehensive Income (Loss) Before Reclassifications (1,260.7) 2,361.8 14.7 (12.8) 116.3 1,219.3 Amounts Reclassified from Accumulated Other Comprehensive Income or Loss (40.7) — (50.7) — 17.7 (73.7) Net Other Comprehensive Income (Loss) (1,301.4) 2,361.8 (36.0) (12.8) 134.0 1,145.6 Balance at December 31, 2021 4,014.4 (8,570.7) 61.8 (274.1) (396.0) (5,164.6) Other Comprehensive Income (Loss) Before Reclassifications (7,066.0) 8,884.6 (30.4) (116.0) 49.7 1,721.9 Amounts Reclassified from Accumulated Other Comprehensive Income or Loss 23.2 — (41.0) — 12.2 (5.6) Net Other Comprehensive Income (Loss) (7,042.8) 8,884.6 (71.4) (116.0) 61.9 1,716.3 Balance at December 31, 2022 (3,028.4) 313.9 (9.6) (390.1) (334.1) (3,448.3) Other Comprehensive Income (Loss) Before Reclassifications 1,069.3 (962.3) (37.4) 69.0 (16.9) 121.7 Amounts Reclassified from Accumulated Other Comprehensive Income or Loss 40.0 — (26.7) — 5.3 18.6 Net Other Comprehensive Income (Loss) 1,109.3 (962.3) (64.1) 69.0 (11.6) 140.3 Balance at December 31, 2023 $ (1,919.1) $ (648.4) $ (73.7) $ (321.1) $ (345.7) $ (3,308.0) 1 Liability for Future Policy Benefits
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 2023 2022 2021 (in millions of dollars) Net Unrealized Gain (Loss) on Securities Net Investment Gain (Loss) Gain (Loss) on Sales on Securities $ (48.7) $ (24.8) $ 60.8 Credit Losses on Fixed Maturity Securities (2.2) (4.6) (9.3) (50.9) (29.4) 51.5 Income Tax Expense (Benefit) (10.9) (6.2) 10.8 Total $ (40.0) $ (23.2) $ 40.7 Net Gain (Loss) on Hedges Net Investment Income Gain on Interest Rate Swaps and Forwards $ 34.7 $ 51.1 $ 60.6 Gain (Loss) on Foreign Exchange Contracts (0.5) (1.0) 1.7 Net Investment Gain (Loss) Gain on Interest Rate Swaps — — 2.0 Gain (Loss) on Foreign Exchange Contracts (0.4) 1.8 (0.1) 33.8 51.9 64.2 Income Tax Expense 7.1 10.9 13.5 Total $ 26.7 $ 41.0 $ 50.7 Unrecognized Pension and Postretirement Benefit Costs Other Expenses Amortization of Net Actuarial Loss $ (7.2) $ (15.7) $ (22.6) Amortization of Prior Service Credit 0.2 0.2 0.2 (7.0) (15.5) (22.4) Income Tax Benefit (1.7) (3.3) (4.7) Total $ (5.3) $ (12.2) $ (17.7)

Financial Services, Insurance (

Financial Services, Insurance (Tables)	12 Months Ended
	Dec. 31, 2023
Insurance [Abstract]
Liability for Future Policy Benefit, Activity	The following table presents balances as well as the changes in the liability for future policy benefits for traditional long duration products. Consolidated December 31 2023 2022 2021 (in millions of dollars) Present Value of Expected Net Premiums Balance, beginning of year $ 12,426.2 $ 15,881.3 $ 17,095.9 Beginning balance at original discount rate 12,695.3 13,186.2 13,623.5 Effect of changes in cash flow assumptions 1,499.2 (101.9) (177.1) Effect of actual variances from expected experience (82.5) (269.6) (328.3) Adjusted beginning of year balance 14,112.0 12,814.7 13,118.1 Issuances 1,054.9 877.5 1,083.9 Interest accretion 584.0 566.0 631.9 Net premiums collected (1,537.4) (1,542.3) (1,627.4) Foreign currency 29.7 (20.6) (20.3) Ending balance at original discount rate 14,243.2 12,695.3 13,186.2 Effect of change in discount rate assumptions 174.6 (269.1) 2,695.1 Balance, end of period $ 14,417.8 $ 12,426.2 $ 15,881.3 Present Value of Expected Future Policy Benefits Balance, beginning of year $ 48,929.4 $ 65,305.0 $ 69,530.5 Beginning balance at original discount rate 49,689.0 50,397.2 50,752.4 Effect of changes in cash flow assumptions 1,702.0 (92.4) (379.9) Effect of actual variances from expected experience (310.8) (535.1) (635.9) Adjusted beginning of year balance 51,080.2 49,769.7 49,736.6 Issuances 1 3,072.2 3,194.5 3,675.0 Interest accretion 2,227.2 2,236.2 2,359.6 Benefit payments (5,236.1) (5,231.0) (5,315.7) Foreign currency 162.2 (280.4) (58.3) Ending balance at original discount rate 51,305.7 49,689.0 50,397.2 Effect of change in discount rate assumptions 1,117.9 (759.6) 14,907.8 Balance, end of period $ 52,423.6 $ 48,929.4 $ 65,305.0 Net liability for future policy benefits $ 38,005.8 $ 36,503.2 $ 49,423.7 Other 1,753.3 1,854.5 2,355.9 Total liability for future policy benefits 39,759.1 38,357.7 51,779.6 Less: Reinsurance recoverable related to future policy benefits 7,756.1 8,128.2 10,348.2 Net liability for future policy benefits, after reinsurance recoverable $ 32,003.0 $ 30,229.5 $ 41,431.4 1 Issuances include new policy issuances for most product lines. For our Unum US group disability, Unum US group life and AD&D and Closed Block - All Other product lines and certain of our Unum International product lines, this line represents new claim incurrals. The following tables summarize the amount of gross premiums and interest accretion reflected in the statements of income as well as the undiscounted and discounted expected gross premiums and expected future benefit payments and the weighted average interest rates for traditional long duration products presented in the rollforward activity above. Consolidated Year Ended December 31 2023 2022 2021 (in millions of dollars) Amount recognized in the statement of income: Gross premiums or assessments $ 9,690.7 $ 9,391.8 $ 9,263.4 Interest accretion $ 1,643.2 $ 1,670.2 $ 1,727.7 Consolidated December 31 2023 2022 2021 (in millions of dollars, except weighted average data) Amount of undiscounted: Expected future benefit payments $ 105,325.8 $ 97,060.7 $ 98,574.9 Expected future gross premiums $ 38,761.5 $ 35,299.8 $ 35,296.0 Amount of discounted (at interest accretion rate): Expected future gross premiums $ 25,552.9 $ 23,827.2 $ 23,821.7 Weighted average interest rate: Interest accretion rate 4.8 % 4.8 % 4.8 % Current discount rate 4.8 % 5.0 % 2.5 % Weighted average duration of the liability 11.5 years 10.9 years 10.9 years The following table presents the balances and changes in the reserves for future policy benefits for traditional long duration products in the Unum US segment. December 31, 2023 Group Disability Group Life and AD&D Voluntary Benefits Individual Disability Total Unum US (in millions of dollars) Present Value of Expected Net Premiums Balance, beginning of year $ — $ — $ 868.2 $ 1,202.9 $ 2,071.1 Beginning balance at original discount rate — — 937.9 1,228.1 2,166.0 Effect of changes in cash flow assumptions — — 180.7 5.0 185.7 Effect of actual variances from expected experience — — (79.8) (10.4) (90.2) Adjusted beginning of year balance — — 1,038.8 1,222.7 2,261.5 Issuances — — 288.6 197.9 486.5 Interest accretion — — 29.0 48.2 77.2 Net premiums collected — — (163.9) (174.4) (338.3) Ending balance at original discount rate — — 1,192.5 1,294.4 2,486.9 Effect of change in discount rate assumptions — — (57.8) 2.3 (55.5) Balance, end of period $ — $ — $ 1,134.7 $ 1,296.7 $ 2,431.4 Present Value of Expected Future Policy Benefits Balance, beginning of year $ 5,533.3 $ 972.6 $ 1,999.5 $ 3,192.8 $ 11,698.2 Beginning balance at original discount rate 5,793.1 998.5 2,141.2 3,244.5 12,177.3 Effect of changes in cash flow assumptions (100.2) — 170.1 7.9 77.8 Effect of actual variances from expected experience (204.0) (37.0) (90.9) (45.3) (377.2) Adjusted beginning of year balance 5,488.9 961.5 2,220.4 3,207.1 11,877.9 Issuances 1 1,094.5 394.2 303.7 215.3 2,007.7 Interest accretion 171.2 20.0 86.2 164.7 442.1 Benefit payments (1,477.5) (439.2) (188.3) (273.2) (2,378.2) Ending balance at original discount rate 5,277.1 936.5 2,422.0 3,313.9 11,949.5 Effect of change in discount rate assumptions (129.7) (14.5) (87.5) 34.7 (197.0) Balance, end of period $ 5,147.4 $ 922.0 $ 2,334.5 $ 3,348.6 $ 11,752.5 Net liability for future policy benefits $ 5,147.4 $ 922.0 $ 1,199.8 $ 2,051.9 $ 9,321.1 Other 0.2 1.0 2.6 27.8 31.6 Total liability for future policy benefits 5,147.6 923.0 1,202.4 2,079.7 9,352.7 Less: Reinsurance recoverable related to future policy benefits 30.7 7.2 14.0 156.7 208.6 Net liability for future policy benefits, after reinsurance recoverable $ 5,116.9 $ 915.8 $ 1,188.4 $ 1,923.0 $ 9,144.1 1 Issuances include new policy issuances for most product lines. Issuances for Unum US group disability and Unum US group life and AD&D represents new claim incurrals. December 31, 2022 Group Disability Group Life and AD&D Voluntary Benefits Individual Disability Total Unum US (in millions of dollars) Present Value of Expected Net Premiums Balance, beginning of year $ — $ — $ 1,124.8 $ 1,494.3 $ 2,619.1 Beginning balance at original discount rate — — 1,032.3 1,279.6 2,311.9 Effect of changes in cash flow assumptions — — (23.4) (73.7) (97.1) Effect of actual variances from expected experience — — (70.9) (25.2) (96.1) Adjusted beginning of year balance — — 938.0 1,180.7 2,118.7 Issuances — — 136.2 168.6 304.8 Interest accretion — — 29.1 49.8 78.9 Net premiums collected — — (165.4) (171.0) (336.4) Ending balance at original discount rate — — 937.9 1,228.1 2,166.0 Effect of change in discount rate assumptions — — (69.7) (25.2) (94.9) Balance, end of period $ — $ — $ 868.2 $ 1,202.9 $ 2,071.1 Present Value of Expected Future Policy Benefits Balance, beginning of year $ 6,725.7 $ 1,124.1 $ 2,697.3 $ 4,017.3 $ 14,564.4 Beginning balance at original discount rate 6,158.3 1,058.3 2,201.8 3,253.3 12,671.7 Effect of changes in cash flow assumptions (102.0) (32.9) (39.9) (53.4) (228.2) Effect of actual variances from expected experience (239.4) (34.3) (74.9) (36.0) (384.6) Adjusted beginning of year balance 5,816.9 991.1 2,087.0 3,163.9 12,058.9 Issuances 1 1,304.3 444.1 154.0 181.4 2,083.8 Interest accretion 210.5 24.5 86.1 155.3 476.4 Benefit payments (1,538.6) (461.2) (185.9) (256.1) (2,441.8) Ending balance at original discount rate 5,793.1 998.5 2,141.2 3,244.5 12,177.3 Effect of change in discount rate assumptions (259.8) (25.9) (141.7) (51.7) (479.1) Balance, end of period $ 5,533.3 $ 972.6 $ 1,999.5 $ 3,192.8 $ 11,698.2 Net liability for future policy benefits $ 5,533.3 $ 972.6 $ 1,131.3 $ 1,989.9 $ 9,627.1 Other 0.4 0.9 15.6 24.7 41.6 Total liability for future policy benefits 5,533.7 973.5 1,146.9 2,014.6 9,668.7 Less: Reinsurance recoverable related to future policy benefits 36.0 7.5 14.1 193.6 251.2 Net liability for future policy benefits, after reinsurance recoverable $ 5,497.7 $ 966.0 $ 1,132.8 $ 1,821.0 $ 9,417.5 1 Issuances include new policy issuances for most product lines. Issuances for Unum US group disability and Unum US group life and AD&D represents new claim incurrals. December 31, 2021 Group Disability Group Life and AD&D Voluntary Benefits Individual Disability Total Unum US (in millions of dollars) Present Value of Expected Net Premiums Balance, beginning of year $ — $ — $ 1,239.3 $ 1,514.2 $ 2,753.5 Beginning balance at original discount rate — — 1,146.9 1,208.8 $ 2,355.7 Effect of changes in cash flow assumptions — — (29.6) (18.9) $ (48.5) Effect of actual variances from expected experience — — (117.5) (10.4) $ (127.9) Adjusted beginning of year balance — — 999.8 1,179.5 $ 2,179.3 Issuances — — 196.5 211.3 $ 407.8 Interest accretion — — 38.3 57.9 $ 96.2 Net premiums collected — — (202.3) (169.1) $ (371.4) Ending balance at original discount rate — — 1,032.3 1,279.6 $ 2,311.9 Effect of change in discount rate assumptions — — 92.5 214.7 $ 307.2 Balance, end of period $ — $ — $ 1,124.8 $ 1,494.3 $ 2,619.1 Present Value of Expected Future Policy Benefits Balance, beginning of year $ 7,281.3 $ 1,126.3 $ 2,768.1 $ 4,226.9 $ 15,402.6 Beginning balance at original discount rate 6,369.4 1,034.4 2,272.6 3,197.6 12,874.0 Effect of changes in cash flow assumptions (186.0) — (40.3) (22.9) (249.2) Effect of actual variances from expected experience (229.3) 4.0 (136.5) (42.3) (404.1) Adjusted beginning of year balance 5,954.1 1,038.4 2,095.8 3,132.4 12,220.7 Issuances 1 1,471.4 467.5 220.6 222.5 2,382.0 Interest accretion 241.5 34.9 96.9 158.5 531.8 Benefit payments (1,508.7) (482.5) (211.5) (260.1) (2,462.8) Ending balance at original discount rate 6,158.3 1,058.3 2,201.8 3,253.3 12,671.7 Effect of change in discount rate assumptions 567.4 65.8 495.5 764.0 1,892.7 Balance, end of period $ 6,725.7 $ 1,124.1 $ 2,697.3 $ 4,017.3 $ 14,564.4 Net liability for future policy benefits $ 6,725.7 $ 1,124.1 $ 1,572.5 $ 2,523.0 $ 11,945.3 Other 0.5 1.2 14.0 59.0 74.7 Total liability for future policy benefits 6,726.2 1,125.3 1,586.5 2,582.0 12,020.0 Less: Reinsurance recoverable related to future policy benefits 40.9 4.4 31.2 231.9 308.4 Net liability for future policy benefits, after reinsurance recoverable $ 6,685.3 $ 1,120.9 $ 1,555.3 $ 2,350.1 $ 11,711.6 1 Issuances include new policy issuances for most product lines. Issuances for Unum US group disability and Unum US group life and AD&D represents new claim incurrals. The following tables summarize the amount of gross premiums and interest accretion reflected in the statements of income as well as the undiscounted and discounted expected gross premiums and expected future benefit payments and the weighted average interest rates for traditional long duration products in the Unum US segment presented in the rollforward activity above. Year Ended December 31, 2023 Group Disability Group Life and AD&D Voluntary Benefits Individual Disability Total Unum US (in millions of dollars) Amount recognized in the statement of income: Gross premiums or assessments $ 2,958.7 $ 1,878.0 $ 789.9 $ 636.6 $ 6,263.2 Interest accretion $ 171.2 $ 20.0 $ 57.2 $ 116.5 $ 364.9 Year Ended December 31, 2022 Group Disability Group Life and AD&D Voluntary Benefits Individual Disability Total Unum US (in millions of dollars) Amount recognized in the statement of income: Gross premiums or assessments $ 2,791.7 $ 1,864.9 $ 773.6 $ 591.5 $ 6,021.7 Interest accretion $ 210.5 $ 24.5 $ 57.0 $ 105.5 $ 397.5 Year Ended December 31, 2021 Group Disability Group Life and AD&D Voluntary Benefits Individual Disability Total Unum US (in millions of dollars) Amount recognized in the statement of income: Gross premiums or assessments $ 2,672.4 $ 1,827.5 $ 773.8 $ 580.1 $ 5,853.8 Interest accretion $ 241.5 $ 34.9 $ 58.6 $ 100.6 $ 435.6 December 31, 2023 Group Disability Group Life and AD&D Voluntary Benefits Individual Disability Total Unum US (in millions of dollars, except weighted average data) Amount of undiscounted: Expected future benefit payments $ 6,376.6 $ 1,063.2 $ 5,173.1 $ 5,313.7 $ 17,926.6 Expected future gross premiums $ — $ — $ 5,450.6 $ 5,724.8 $ 11,175.4 Amount of discounted (at interest accretion rate): Expected future gross premiums $ — $ — $ 3,717.5 $ 4,112.9 $ 7,830.4 Weighted average interest rate: Interest accretion rate 4.0 % 2.2 % 5.0 % 5.1 % 4.2% Current discount rate 4.6 % 2.6 % 4.9 % 4.8 % 4.5% Weighted average duration of the liability 4.3 years 2.6 years 18.1 years 9.6 years 7.0 years December 31, 2022 Group Disability Group Life and AD&D Voluntary Benefits Individual Disability Total Unum US (in millions of dollars, except weighted average data) Amount of undiscounted: Expected future benefit payments $ 6,988.1 $ 1,133.0 $ 4,561.1 $ 5,168.2 $ 17,850.4 Expected future gross premiums $ — $ — $ 3,979.6 $ 5,525.1 $ 9,504.7 Amount of discounted (at interest accretion rate): Expected future gross premiums $ — $ — $ 2,939.1 $ 3,962.1 $ 6,901.2 Weighted average interest rate: Interest accretion rate 3.8 % 2.2 % 5.1 % 5.1 % 4.0% Current discount rate 4.9 % 2.7 % 5.2 % 5.1 % 4.7% Weighted average duration of the liability 4.4 years 2.6 years 17.8 years 9.4 years 6.8 years December 31, 2021 Group Disability Group Life and AD&D Voluntary Benefits Individual Disability Total Unum US (in millions of dollars, except weighted average data) Amount of undiscounted: Expected future benefit payments $ 7,538.7 $ 1,224.7 $ 4,192.1 $ 5,210.6 $ 18,166.1 Expected future gross premiums $ — $ — $ 4,136.9 $ 5,597.3 $ 9,734.2 Amount of discounted (at interest accretion rate): Expected future gross premiums $ — $ — $ 3,156.5 $ 3,958.8 $ 7,115.3 Weighted average interest rate: Interest accretion rate 4.0 % 2.3 % 5.1 % 5.0 % 4.1% Current discount rate 2.1 % 1.3 % 2.8 % 2.4 % 2.1% Weighted average duration of the liability 4.5 years 2.9 years 15.8 years 9.5 years 6.5 years The following table presents the balances and changes in the reserves for future policy benefits for traditional long duration products in the Unum International segment. December 31 2023 2022 2021 (in millions of dollars) Present Value of Expected Net Premiums Balance, beginning of year $ 197.1 $ 260.5 $ 311.7 Beginning balance at original discount rate 246.8 258.1 251.4 Effect of changes in cash flow assumptions (5.1) (0.3) — Effect of actual variances from expected experience 17.1 5.6 9.3 Adjusted beginning of year balance 258.8 263.4 260.7 Issuances 23.5 17.8 31.4 Interest accretion 9.4 8.4 8.9 Net premiums collected (23.0) (22.2) (22.6) Foreign currency 29.7 (20.6) (20.3) Ending balance at original discount rate 298.4 246.8 258.1 Effect of change in discount rate assumptions (28.1) (49.7) 2.4 Balance, end of period $ 270.3 $ 197.1 $ 260.5 Present Value of Expected Future Policy Benefits Balance, beginning of year $ 2,231.4 $ 3,181.8 $ 3,465.9 Beginning balance at original discount rate 2,495.5 2,703.8 2,644.5 Effect of changes in cash flow assumptions 17.7 (20.1) (5.5) Effect of actual variances from expected experience 1.3 46.3 15.9 Adjusted beginning of year balance 2,514.5 2,730.0 2,654.9 Issuances 1 335.2 327.7 391.6 Interest accretion 63.5 64.9 75.9 Benefit payments (388.3) (346.7) (360.3) Foreign currency 162.2 (280.4) (58.3) Ending balance at original discount rate 2,687.1 2,495.5 2,703.8 Effect of change in discount rate assumptions (159.7) (264.1) 478.0 Balance, end of period $ 2,527.4 $ 2,231.4 $ 3,181.8 Net liability for future policy benefits $ 2,257.1 $ 2,034.3 $ 2,921.3 Other 36.1 28.9 34.5 Total liability for future policy benefits 2,293.2 2,063.2 2,955.8 Less: Reinsurance recoverable related to future policy benefits 78.7 70.3 125.3 Net liability for future policy benefits, after reinsurance recoverable $ 2,214.5 $ 1,992.9 $ 2,830.5 1 Issuances for Unum International primarily represent new claim incurrals. The following tables summarize the amount of gross premiums and interest accretion reflected in the statements of income as well as the undiscounted and discounted expected gross premiums and expected future benefit payments and the weighted average interest rates for traditional long duration products in the Unum International segment presented in the rollforward activity above. Year Ended December 31 2023 2022 2021 (in millions of dollars) Amount recognized in the statement of income: Gross premiums or assessments $ 849.0 $ 786.8 $ 793.9 Interest accretion $ 54.1 $ 56.5 $ 67.0 December 31 2023 2022 2021 (in millions of dollars, except weighted average data) Amount of undiscounted: Expected future benefit payments $ 4,261.1 $ 3,905.4 $ 4,292.2 Expected future gross premiums $ 1,196.6 $ 943.9 $ 914.9 Amount of discounted (at interest accretion rate): Expected future gross premiums $ 778.6 $ 626.2 $ 620.8 Weighted average interest rate: Interest accretion rate 4.0 % 4.0 % 4.0 % Current discount rate 4.6 % 5.0 % 2.0 % Weighted average duration of the liability 8.6 years 8.6 years 8.8 years The following table presents the balances and changes in the reserves for future policy benefits for traditional long duration products in the Colonial Life segment. December 31 2023 2022 2021 (in millions of dollars) Present Value of Expected Net Premiums Balance, beginning of year $ 3,745.4 $ 4,597.0 $ 4,671.9 Beginning balance at original discount rate 4,046.4 4,158.9 4,233.7 Effect of changes in cash flow assumptions (322.7) (32.3) (157.1) Effect of actual variances from expected experience (53.5) (145.6) (60.4) Adjusted beginning of year balance 3,670.2 3,981.0 4,016.2 Issuances 544.9 554.9 644.7 Interest accretion 122.7 129.7 156.2 Net premiums collected (583.5) (619.2) (658.2) Ending balance at original discount rate 3,754.3 4,046.4 4,158.9 Effect of change in discount rate assumptions (161.7) (301.0) 438.1 Balance, end of period $ 3,592.6 $ 3,745.4 $ 4,597.0 Present Value of Expected Future Policy Benefits Balance, beginning of year $ 5,581.1 $ 7,054.8 $ 7,022.9 Beginning balance at original discount rate 6,163.9 6,201.5 6,169.6 Effect of changes in cash flow assumptions (402.9) (85.9) (178.1) Effect of actual variances from expected experience (52.0) (191.3) (95.2) Adjusted beginning of year balance 5,709.0 5,924.3 5,896.3 Issuances 605.9 628.5 704.1 Interest accretion 211.3 217.0 243.1 Benefit payments (601.0) (605.9) (642.0) Ending balance at original discount rate 5,925.2 6,163.9 6,201.5 Effect of change in discount rate assumptions (359.2) (582.8) 853.3 Balance, end of period $ 5,566.0 $ 5,581.1 $ 7,054.8 Net liability for future policy benefits $ 1,973.4 $ 1,835.7 $ 2,457.8 Other 24.4 22.7 25.1 Total liability for future policy benefits 1,997.8 1,858.4 2,482.9 Less: Reinsurance recoverable related to future policy benefits 1.8 1.1 2.3 Net liability for future policy benefits, after reinsurance recoverable $ 1,996.0 $ 1,857.3 $ 2,480.6 The following tables summarize the amount of gross premiums and interest accretion reflected in the statements of income as well as the undiscounted and discounted expected gross premiums and expected future benefit payments and the weighted average interest rates for traditional long duration products in the Colonial Life segment presented in the rollforward activity above. Year Ended December 31 2023 2022 2021 (in millions of dollars) Amount recognized in the statement of income: Gross premiums or assessments $ 1,658.6 $ 1,635.8 $ 1,615.8 Interest accretion $ 88.6 $ 87.3 $ 86.9 December 31 2023 2022 2021 (in millions of dollars, except weighted average data) Amount of undiscounted: Expected future benefit payments $ 9,796.7 $ 10,011.9 $ 9,583.1 Expected future gross premiums $ 11,903.1 $ 12,221.3 $ 11,487.9 Amount of discounted (at interest accretion rate): Expected future gross premiums $ 8,702.2 $ 8,966.3 $ 8,566.7 Weighted average interest rate: Interest accretion rate 4.3 % 4.3 % 4.4 % Current discount rate 4.8 % 5.2 % 2.7 % Weighted average duration of the liability 17.0 years 17.5 years 16.4 years The following table presents the balances and changes in the reserves for future policy benefits for traditional long duration products in the Closed Block segment. December 31, 2023 Long-term Care All Other Total Closed Block (in millions of dollars) Present Value of Expected Net Premiums Balance, beginning of year $ 6,412.6 $ — $ 6,412.6 Beginning balance at original discount rate 6,236.1 — 6,236.1 Effect of changes in cash flow assumptions 1,641.3 — 1,641.3 Effect of actual variances from expected experience 44.1 — 44.1 Adjusted beginning of year balance 7,921.5 — 7,921.5 Interest accretion 374.7 — 374.7 Net premiums collected (592.6) — (592.6) Ending balance at original discount rate 7,703.6 — 7,703.6 Effect of change in discount rate assumptions 419.9 — 419.9 Balance, end of period $ 8,123.5 $ — $ 8,123.5 Present Value of Expected Future Policy Benefits Balance, beginning of year $ 21,199.9 $ 8,218.8 $ 29,418.7 Beginning balance at original discount rate 20,221.6 8,630.7 28,852.3 Effect of changes in cash flow assumptions 2,009.4 — 2,009.4 Effect of actual variances from expected experience 113.1 4.0 117.1 Adjusted beginning of year balance 22,344.1 8,634.7 30,978.8 Issuances 1 — 123.4 123.4 Interest accretion 1,151.4 358.9 1,510.3 Benefit payments (846.2) (1,022.4) (1,868.6) Ending balance at original discount rate 22,649.3 8,094.6 30,743.9 Effect of change in discount rate assumptions 2,048.4 (214.6) 1,833.8 Balance, end of period $ 24,697.7 $ 7,880.0 $ 32,577.7 Net liability for future policy benefits $ 16,574.2 $ 7,880.0 24,454.2 Other 2 23.1 1,638.1 1,661.2 Total liability for future policy benefits 16,597.3 9,518.1 26,115.4 Less: Reinsurance recoverable related to future policy benefits 4.5 7,462.4 7,466.9 Net liability for future policy benefits, after reinsurance recoverable $ 16,592.8 $ 2,055.7 $ 18,648.5 1 Issuances for Closed Block - All Other represents new claim incurrals. 2 Other for Closed Block - All Other primarily includes our closed block group pension products and certain of our ceded closed block individual life products. December 31, 2022 Long-term Care All Other Total Closed Block (in millions of dollars) Present Value of Expected Net Premiums Balance, beginning of year $ 8,404.7 $ — $ 8,404.7 Beginning balance at original discount rate 6,457.3 — 6,457.3 Effect of changes in cash flow assumptions 27.8 — 27.8 Effect of actual variances from expected experience (33.5) — (33.5) Adjusted beginning of year balance 6,451.6 — 6,451.6 Interest accretion 349.0 — 349.0 Net premiums collected (564.5) — (564.5) Ending balance at original discount rate 6,236.1 — 6,236.1 Effect of change in discount rate assumptions 176.5 — 176.5 Balance, end of period $ 6,412.6 $ — $ 6,412.6 Present Value of Expected Future Policy Benefits Balance, beginning of year $ 30,089.6 $ 10,414.4 $ 40,504.0 Beginning balance at original discount rate 19,870.8 8,949.4 28,820.2 Effect of changes in cash flow assumptions 24.9 216.9 241.8 Effect of actual variances from expected experience (36.2) 30.7 (5.5) Adjusted beginning of year balance 19,859.5 9,197.0 29,056.5 Issuances 1 — 154.5 154.5 Interest accretion 1,105.1 372.8 1,477.9 Benefit payments (743.0) (1,093.6) (1,836.6) Ending balance at original discount rate 20,221.6 8,630.7 28,852.3 Effect of change in discount rate assumptions 978.3 (411.9) 566.4 Balance, end of period $ 21,199.9 $ 8,218.8 $ 29,418.7 Net liability for future policy benefits $ 14,787.3 $ 8,218.8 $ 23,006.1 Other 2 24.3 1,737.0 1,761.3 Total liability for future policy benefits 14,811.6 9,955.8 24,767.4 Less: Reinsurance recoverable related to future policy benefits 5.7 7,799.8 7,805.5 Net liability for future policy benefits, after reinsurance recoverable $ 14,805.9 $ 2,156.0 $ 16,961.9 1 Issuances for Closed Block - All Other represents new claim incurrals. 2 Other for Closed Block - All Other primarily includes our closed block group pension products and certain of our ceded closed block individual life products. December 31, 2021 Long-term Care All Other Total Closed Block (in millions of dollars) Present Value of Expected Net Premiums Balance, beginning of year $ 9,358.8 $ — $ 9,358.8 Beginning balance at original discount rate 6,782.7 — 6,782.7 Effect of changes in cash flow assumptions 28.5 — 28.5 Effect of actual variances from expected experience (149.3) — (149.3) Adjusted beginning of year balance 6,661.9 — 6,661.9 Interest accretion 370.6 — 370.6 Net premiums collected (575.2) — (575.2) Ending balance at original discount rate 6,457.3 — 6,457.3 Effect of change in discount rate assumptions 1,947.4 — 1,947.4 Balance, end of period $ 8,404.7 $ — $ 8,404.7 Present Value of Expected Future Policy Benefits Balance, beginning of year $ 32,047.2 $ 11,591.9 $ 43,639.1 Beginning balance at original discount rate 19,549.7 9,514.6 29,064.3 Effect of changes in cash flow assumptions 52.9 — 52.9 Effect of actual variances from expected experience (170.8) 18.3 (152.5) Adjusted beginning of year balance 19,431.8 9,532.9 28,964.7 Issuances 1 — 197.3 197.3 Interest accretion 1,111.6 397.2 1,508.8 Benefit payments (672.6) (1,178.0) (1,850.6) Ending balance at original discount rate 19,870.8 8,949.4 28,820.2 Effect of change in discount rate assumptions 10,218.8 1,465.0 11,683.8 Balance, end of period $ 30,089.6 $ 10,414.4 $ 40,504.0 Net liability for future policy benefits $ 21,684.9 $ 10,414.4 $ 32,099.3 Other 2 29.8 2,191.8 2,221.6 Total liability for future policy benefits 21,714.7 12,606.2 34,320.9 Less: Reinsurance recoverable related to future policy benefits 7.4 9,904.7 9,912.1 Net liability for future policy benefits, after reinsurance recoverable $ 21,707.3 $ 2,701.5 $ 24,408.8 1 Issuances for Closed Block - All Other represents new claim incurrals. 2 Other for Closed Block - All Other primarily includes our closed block group pension products and certain of our ceded closed block individual life products. The following tables summarize the amount of gross premiums and interest accretion reflected in the statements of income as well as the undiscounted and discounted expected gross premiums and expected future benefit payments and the weighted average interest rates for traditional long duration products in the Closed Block segment presented in the rollforward activity above. Year Ended December 31, 2023 Long-term Care All Other Total Closed Block (in millions of dollars) Amount recognized in the statement of income: Gross premiums or assessments $ 696.1 $ 223.8 $ 919.9 Interest accretion $ 776.7 $ 358.9 $ 1,135.6 Year Ended December 31, 2022 Long-term Care All Other Total Closed Block (in millions of dollars) Amount recognized in the statement of income: Gross premiums or assessments $ 697.5 $ 250.0 $ 947.5 Interest accretion $ 756.1 $ 372.8 $ 1,128.9 Year Ended December 31, 2021 Long-term Care All Other Total Closed Block (in millions of dollars) Amount recognized in the statement of income: Gross premiums or assessments $ 705.0 $ 294.9 $ 999.9 Interest accretion $ 741.0 $ 397.2 $ 1,138.2 December 31, 2023 Long-term Care All Other Total Closed Block (in millions of dollars, except weighted average data) Amount of undiscounted: Expected future benefit payments $ 61,447.7 $ 11,893.7 $ 73,341.4 Expected future gross premiums $ 14,486.4 $ — $ 14,486.4 Amount of discounted (at interest accretion rate): Expected future gross premiums $ 8,241.7 $ — $ 8,241.7 Weighted average interest rate: Interest accretion rate 5.6 % 4.6 % 5.2 % Current discount rate 5.0% 4.9 % 4.9 % Weighted average duration of the liability 16.4 years 7.3 years 13.2 years December 31, 2022 Long-term Care All Other Total Closed Block (in millions of dollars, except weighted average data) Amount of undiscounted: Expected future benefit payments $ 52,544.0 $ 12,749.0 $ 65,293.0 Expected future gross premiums $ 12,629.9 $ — $ 12,629.9 Amount of discounted (at interest accretion rate): Expected future gross premiums $ 7,333.5 $ — $ 7,333.5 Weighted average interest rate: Interest accretion rate 5.5 % 4.6 % 5.2% Current discount rate 5.2 % 5.1 % 5.2% Weighted average duration of the liability 15.5 years 7.4 years 12.4 years December 31, 2021 Long-term Care All Other Total Closed Block (in millions of dollars, except weighted average data) Amount of undiscounted: Expected future benefit payments $ 53,395.1 $ 13,138.4 $ 66,533.5 Expected future gross premiums $ 13,159.0 $ — $ 13,159.0 Amount of discounted (at interest accretion rate): Expected future gross premiums $ 7,518.9 $ — $ 7,518.9 Weighted average interest rate: Interest accretion rate 5.6 % 4.6 % 5.2% Current discount rate 2.8 % 2.5 % 2.7% Weighted average duration of the liability 16.3 years 7.3 years 12.7 years A reconciliation of the liability for future policy benefits reflected in the preceding rollforwards to the related liability balances in the consolidated balance sheets are as follows: December 31 2023 2022 2021 (in millions of dollars) Liability for future policy benefits Unum US 1 $ 9,352.7 $ 9,668.7 $ 12,020.0 Unum International 2,293.2 2,063.2 2,955.8 Colonial Life 1,997.8 1,858.4 2,482.9 Closed Block 1 26,115.4 24,767.4 34,320.9 Other products 1 250.3 219.4 212.0 Total liability for future policy benefits $ 40,009.4 $ 38,577.1 $ 51,991.6 1
Policyholder Account Balance	The following table presents the balances and changes in the policyholders' account balances: December 31, 2023 Unum US - Voluntary Benefits Colonial Life Closed Block - All Other Total (in millions of dollars, except weighted average data) Balance, beginning of year $ 586.8 $ 852.4 $ 4,159.4 $ 5,598.6 Premiums received 58.5 84.9 31.7 175.1 Policy charges 1 (60.4) (74.7) (107.2) (242.3) Surrenders and withdrawals (33.3) (36.8) (18.8) (88.9) Benefit payments (9.7) (7.2) (216.2) (233.1) Interest credited 22.2 34.2 322.1 378.5 Other 14.5 0.1 (88.3) (73.7) Balance, end of period 578.6 852.9 4,082.7 5,514.2 Reserves in excess of account balance 99.5 16.9 37.1 153.5 Total policyholders' account balances 678.1 869.8 4,119.8 5,667.7 Less: Reinsurance recoverable related to policyholders' account balances 0.9 — 4,119.8 4,120.7 Net policyholders' account balances, after reinsurance recoverable $ 677.2 $ 869.8 $ — $ 1,547.0 Weighted average crediting rate 3.9% 4.1% 8.0% 7.0% Net amount at risk 2 $ 4,495.6 $ 8,760.1 $ 1,824.3 $ 15,080.0 Cash surrender value $ 566.9 $ 813.5 $ 4,062.3 $ 5,442.7 1 Contracts included in the policyholder account balances are generally charged a premium and/or monthly assessments on the basis of the account balance. 2 For those guarantees of benefits that are payable in the event of death, the net amount at risk is generally defined as the current guaranteed minimum death benefit in excess of the current account balance at the balance sheet date. December 31, 2022 Unum US - Voluntary Benefits Colonial Life Closed Block - All Other Total (in millions of dollars, except weighted average data) Balance, beginning of year $ 598.7 $ 849.2 $ 4,231.7 $ 5,679.6 Premiums received 64.5 90.9 32.2 187.6 Policy charges 1 (64.5) (78.0) (105.5) (248.0) Surrenders and withdrawals (32.9) (36.2) (21.3) (90.4) Benefit payments (10.7) (8.0) (292.8) (311.5) Interest credited 23.5 34.2 311.5 369.2 Other 8.2 0.3 3.6 12.1 Balance, end of period 586.8 852.4 4,159.4 5,598.6 Reserves in excess of account balance 92.9 16.7 32.0 141.6 Total policyholders' account balances 679.7 869.1 4,191.4 5,740.2 Less: Reinsurance recoverable related to policyholders' account balances 1.1 0.2 4,191.4 4,192.7 Net policyholders' account balances, after reinsurance recoverable $ 678.6 $ 868.9 $ — $ 1,547.5 Weighted average crediting rate 4.0% 4.1% 7.6% 6.7% Net amount at risk 2 $ 4,908.0 $ 9,338.5 $ 1,931.6 $ 16,178.1 Cash surrender value $ 583.3 $ 800.9 $ 4,045.9 $ 5,430.1 1 Contracts included in the policyholder account balances are generally charged a premium and/or monthly assessments on the basis of the account balance. 2 For those guarantees of benefits that are payable in the event of death, the net amount at risk is generally defined as the current guaranteed minimum death benefit in excess of the current account balance at the balance sheet date. December 31, 2021 Unum US - Voluntary Benefits Colonial Life Closed Block - All Other Total (in millions of dollars, except weighted average data) Balance, beginning of year $ 616.7 $ 843.8 $ 4,218.0 $ 5,678.5 Premiums received 69.6 97.5 37.4 204.5 Policy charges 1 (69.3) (82.4) (101.2) (252.9) Surrenders and withdrawals (39.5) (35.7) (14.3) (89.5) Benefit payments (11.4) (8.5) (234.1) (254.0) Interest credited 23.7 34.0 315.4 373.1 Other 8.9 0.5 10.5 19.9 Balance, end of period 598.7 849.2 4,231.7 5,679.6 Reserves in excess of account balance 82.9 21.5 30.8 135.2 Total policyholders' account balances 681.6 870.7 4,262.5 5,814.8 Less: Reinsurance recoverable related to policyholders' account balances 1.2 0.3 4,262.5 4,264.0 Net policyholders' account balances, after reinsurance recoverable $ 680.4 $ 870.4 $ — $ 1,550.8 Weighted average crediting rate 3.9% 4.1% 7.8% 6.8% Net amount at risk 2 $ 5,356.1 $ 10,000.6 $ 2,052.0 $ 17,408.7 Cash surrender value $ 584.8 $ 784.6 $ 4,134.7 $ 5,504.1 1 Contracts included in the policyholder account balances are generally charged a premium and/or monthly assessments on the basis of the account balance. 2 For those guarantees of benefits that are payable in the event of death, the net amount at risk is generally defined as the current guaranteed minimum death benefit in excess of the current account balance at the balance sheet date.
Policyholder Account Balance, Guaranteed Minimum Crediting Rate	The balance of the account values by range of guaranteed minimum crediting rates and the related range of difference, in basis points, between rates being credited to policyholders and the respective guaranteed minimums is as follows. December 31, 2023 Range of Guaranteed Minimum Crediting Rate At Guaranteed Minimum 1 Basis Point - 50 Basis Points Above 51 Basis Points - 150 Basis Points Above Greater than 150 Basis Points Above Total (in millions of dollars) Unum US - Voluntary Benefits 3.00% - 3.99% $ 91.9 $ — $ — $ — $ 91.9 4.00% - 4.99% 227.1 190.1 37.7 — 454.9 5.00% - 6.00% 31.8 — — — 31.8 350.8 190.1 37.7 — 578.6 Colonial Life 4.00% - 5.00% 846.7 6.2 — — 852.9 Closed Block - All Other 3.00% - 5.99% 526.8 1,081.8 30.7 — 1,639.3 6.00% - 8.99% 1.3 31.0 — — 32.3 9.00% - 11.99% 318.4 2,036.5 — — 2,354.9 12.00% - 15.00% — 56.2 — — 56.2 846.5 3,205.5 30.7 — 4,082.7 Total $ 2,044.0 $ 3,401.8 $ 68.4 $ — $ 5,514.2 December 31, 2022 Range of Guaranteed Minimum Crediting Rate At Guaranteed Minimum 1 Basis Point - 50 Basis Points Above 51 Basis Points - 150 Basis Points Above Greater than 150 Basis Points Above Total (in millions of dollars) Unum US - Voluntary Benefits 3.00% - 3.99% $ 94.4 $ — $ — $ — $ 94.4 4.00% - 4.99% 274.5 183.9 — — 458.4 5.00% - 6.00% 34.0 — — — 34.0 402.9 183.9 — — 586.8 Colonial Life 4.00% - 5.00% 846.4 6.0 — — 852.4 Closed Block - All Other 3.00% - 5.99% 1,661.7 29.1 6.4 — 1,697.2 6.00% - 8.99% 31.4 — — — 31.4 9.00% - 11.99% 2,378.2 — — — 2,378.2 12.00% - 15.00% 52.6 — — — 52.6 4,123.9 29.1 6.4 — 4,159.4 Total $ 5,373.2 $ 219.0 $ 6.4 $ — $ 5,598.6 December 31, 2021 Range of Guaranteed Minimum Crediting Rate At Guaranteed Minimum 1 Basis Point - 50 Basis Points Above 51 Basis Points - 150 Basis Points Above Greater than 150 Basis Points Above Total (in millions of dollars) Unum US - Voluntary Benefits 3.00% - 3.99% $ 98.0 $ — $ — $ — $ 98.0 4.00% - 4.99% 288.8 177.0 — — 465.8 5.00% - 6.00% 34.9 — — — 34.9 421.7 177.0 — — 598.7 Colonial Life 4.00% - 5.00% 843.4 5.8 — — 849.2 Closed Block - All Other 3.00% - 5.99% 1,816.1 30.2 6.4 — 1,852.7 6.00% - 8.99% 29.6 — — — 29.6 9.00% - 11.99% 2,300.4 — — — 2,300.4 12.00% - 15.00% 49.0 — — — 49.0 4,195.1 30.2 6.4 — 4,231.7 Total $ 5,460.2 $ 213.0 $ 6.4 $ — $ 5,679.6
Deferred Policy Acquisition Costs by Segment	The following tables display the changes in DAC throughout the year: December 31, 2023 Unum US Unum International Colonial Life Total (in millions of dollars) Balance, beginning of year $ 1,185.1 $ 37.0 $ 1,337.9 $ 2,560.0 Capitalization 314.7 14.6 302.9 632.2 Amortization expense (267.6) (8.4) (205.4) (481.4) Foreign currency — 3.7 — 3.7 Balance, end of year $ 1,232.2 $ 46.9 $ 1,435.4 $ 2,714.5 December 31, 2022 Unum US Unum International Colonial Life Total (in millions of dollars) Balance, beginning of year $ 1,152.9 $ 36.4 $ 1,238.1 $ 2,427.4 Capitalization 273.1 12.0 271.8 556.9 Amortization expense (240.9) (8.2) (172.0) (421.1) Foreign currency — (3.2) — (3.2) Balance, end of year $ 1,185.1 $ 37.0 $ 1,337.9 $ 2,560.0 December 31, 2021 Unum US Unum International Colonial Life Total (in millions of dollars) Balance, beginning of year $ 1,181.0 $ 32.0 $ 1,144.7 $ 2,357.7 Capitalization 257.8 12.8 252.6 523.2 Amortization expense (285.9) (7.0) (159.2) (452.1) Foreign currency — (1.4) — (1.4) Balance, end of year $ 1,152.9 $ 36.4 $ 1,238.1 $ 2,427.4 December 31, 2023 Group Disability Group Life and AD&D Voluntary Benefits Individual Disability Dental and Vision Total Unum US (in millions of dollars) Balance, beginning of year $ 61.0 $ 49.3 $ 601.0 $ 464.4 $ 9.4 $ 1,185.1 Capitalization 60.2 38.6 115.8 87.4 12.7 314.7 Amortization expense (57.6) (39.0) (106.2) (54.0) (10.8) (267.6) Balance, end of year $ 63.6 $ 48.9 $ 610.6 $ 497.8 $ 11.3 $ 1,232.2 December 31, 2022 Group Disability Group Life and AD&D Voluntary Benefits Individual Disability Dental and Vision Total Unum US (in millions of dollars) Balance, beginning of year $ 60.9 $ 53.9 $ 588.6 $ 441.8 $ 7.7 $ 1,152.9 Capitalization 53.1 37.3 100.0 72.0 10.7 273.1 Amortization expense (53.0) (41.9) (87.6) (49.4) (9.0) (240.9) Balance, end of year $ 61.0 $ 49.3 $ 601.0 $ 464.4 $ 9.4 $ 1,185.1 December 31, 2021 Group Disability Group Life and AD&D Voluntary Benefits Individual Disability Dental and Vision Total Unum US (in millions of dollars) Balance, beginning of year $ 95.3 $ 76.4 $ 569.7 $ 423.6 $ 16.0 $ 1,181.0 Capitalization 49.8 36.1 99.4 63.9 8.6 257.8 Amortization expense (84.2) (58.6) (80.5) (45.7) (16.9) (285.9) Balance, end of year $ 60.9 $ 53.9 $ 588.6 $ 441.8 $ 7.7 $ 1,152.9

Income Tax (Tables)

Income Tax (Tables)	12 Months Ended
	Dec. 31, 2023
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 2023 2022 2021 (in millions of dollars) Net Income $ 356.3 $ 342.8 $ 279.6 Stockholders' Equity - Accumulated Other Comprehensive Income (Loss) Change in Net Unrealized Gain (Loss) on Securities 300.6 (1,890.8) (346.9) Change in the Effect of Discount Rate Assumptions on the Liability for Future Policy and Contract Benefits, Net of Reinsurance (256.5) 2,385.1 622.8 Change in Net Gain (Loss) on Hedges (17.0) (19.2) (9.8) Change in Foreign Currency Translation Adjustment 0.9 (0.1) 4.2 Change in Unrecognized Pension and Postretirement Benefit Costs (2.7) 18.9 42.1 Total $ 381.6 $ 836.7 $ 592.0
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 2023 2022 2021 Statutory Income Tax 21.0 % 21.0 % 21.0 % Policyholder Reserves (0.6) (1.7) 2.0 Other Items, Net 1.3 0.3 (0.8) Effective Tax 21.7 % 19.6 % 22.2 %
Schedule of Deferred Tax Assets and Liabilities	Our net deferred tax asset consists of the following. December 31 2023 2022 (in millions of dollars) Deferred Tax Asset Invested Assets $ 354.5 $ 664.9 Reserves 462.6 116.4 Employee Benefits 161.9 158.3 Other 35.8 34.4 Gross Deferred Tax Asset 1,014.8 974.0 Less: Valuation Allowance 11.0 10.3 Net Deferred Tax Asset 1,003.8 963.7 Deferred Tax Liability Deferred Acquisition Costs 175.1 177.7 Fixed Assets 36.7 48.9 Cost of Reinsurance 119.7 131.6 Other 49.9 44.7 Gross Deferred Tax Liability 381.4 402.9 Net Deferred Tax Asset $ 622.4 $ 560.8
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 2023 2022 2021 (in millions of dollars) Income Before Tax Domestic $ 1,506.2 $ 1,596.8 $ 1,150.5 Foreign 133.9 153.2 110.1 Total $ 1,640.1 $ 1,750.0 $ 1,260.6 Current Tax Expense (Benefit) Federal $ 440.4 $ 306.5 $ 180.7 State and Local (2.5) 12.7 2.6 Foreign 14.1 154.3 29.5 Total 452.0 473.5 212.8 Deferred Tax Expense (Benefit) Federal (106.2) 42.7 54.0 State and Local (1.5) 1.1 (2.2) Foreign 12.0 (174.5) 15.0 Total (95.7) (130.7) 66.8 Total Tax Expense $ 356.3 $ 342.8 $ 279.6
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 2023 2022 2021 (in millions of dollars) Balance at Beginning of Year $ 177.4 $ 198.8 $ 219.7 Decreases for Tax Positions Related to Prior Years (20.7) (21.0) (20.9) Lapse of the Applicable Statute of Limitations — (0.4) — Balance at End of Year 156.7 177.4 198.8 Less Tax Attributable to Temporary Items Included Above (42.4) (63.5) (84.7) Total Unrecognized Tax Benefits That if Recognized Would Affect the Effective Tax Rate $ 114.3 $ 113.9 $ 114.1

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2023
Debt Disclosure [Abstract]
Schedule of Debt	Debt consists of the following: December 31 2023 2022 Interest Rates Maturities (in millions of dollars) 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 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 2021 4.125% 2051 600.0 600.0 Medium-term Notes issued 1990 - 1996 7.190% 2028 18.5 18.5 Junior Subordinated Debt Securities issued 1998 7.405% 2038 189.7 189.7 Junior Subordinated Debt Securities issued 2018 6.250% 2058 300.0 300.0 Term Loan issued 2022 Variable 2027 350.0 350.0 Less: Unamortized Net Premium 2.5 2.5 Unamortized Debt Issuance Costs (30.6) (33.2) Total Long-term Debt $ 3,430.4 $ 3,427.8 Short-term Debt Medium-term Notes Issued 1990 7.000% 2023 — 2.0 Total Debt $ 3,430.4 $ 3,429.8

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2023
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 2023 2022 2023 2022 2023 2022 (in millions of dollars) Change in Benefit Obligation Benefit Obligation at Beginning of Year $ 1,585.5 $ 2,207.5 $ 157.9 $ 278.3 $ 83.9 $ 110.3 Service Cost 9.2 7.7 — — — — Interest Cost 87.9 67.2 7.7 5.0 4.5 3.0 Plan Participant Contributions — — — — 0.1 0.1 Actuarial Loss (Gain) (1) 61.0 (604.1) 3.8 (92.4) (0.5) (19.4) Benefits and Expenses Paid (168.3) (92.8) (5.7) (5.4) (9.0) (10.1) Change in Foreign Exchange Rates — — 8.6 (27.6) — — Benefit Obligation at End of Year $ 1,575.3 $ 1,585.5 $ 172.3 $ 157.9 $ 79.0 $ 83.9 Accumulated Benefit Obligation at December 31 $ 1,575.3 $ 1,585.5 $ 172.3 $ 158.0 N/A N/A Change in Fair Value of Plan Assets Fair Value of Plan Assets at Beginning of Year $ 1,308.3 $ 1,801.7 $ 140.5 $ 303.7 $ 8.5 $ 9.0 Actual Return on Plan Assets 145.6 (410.6) 3.1 (128.4) — 0.1 Employer Contributions 10.3 10.0 — — 8.6 9.4 Plan Participant Contributions — — — — 0.1 0.1 Benefits and Expenses Paid (168.3) (92.8) (5.7) (5.4) (9.0) (10.1) Change in Foreign Exchange Rates — — 7.5 (29.4) — — Fair Value of Plan Assets at End of Year $ 1,295.9 $ 1,308.3 $ 145.4 $ 140.5 $ 8.2 $ 8.5 Underfunded Status $ 279.4 $ 277.2 $ 26.9 $ 17.4 $ 70.8 $ 75.4 (1) The actuarial losses recognized in 2023 for the U.S. and U.K. plans were driven by decreases in the discount rate assumption. Also contributing to the actuarial loss for the U.K. plan in 2023 was unfavorable plan experience resulting from a higher than expected rate of inflation. The actuarial gain recognized in 2023 for the OPEB plan was driven by favorable plan experience mostly offset by a decrease in the assumed discount rate. The actuarial gains recognized in 2022 for the U.S., OPEB, and U.K. plans were primarily driven by increases 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, 2023 and 2022 are as follows. Pension Benefits U.S. Plans U.K. Plan OPEB 2023 2022 2023 2022 2023 2022 (in millions of dollars) Current Liability $ 9.1 $ 8.8 $ — $ — $ 0.7 $ 1.1 Noncurrent Liability 270.3 268.4 26.9 17.4 70.1 74.3 Underfunded Status $ 279.4 $ 277.2 $ 26.9 $ 17.4 $ 70.8 $ 75.4 Unrecognized Pension and Postretirement Benefit Costs Net Actuarial Gain (Loss) $ (510.2) $ (517.8) $ (95.0) $ (83.7) $ 21.2 $ 31.6 Prior Service Credit (Cost) (0.6) (0.6) (0.2) (0.2) 2.3 2.5 (510.8) (518.4) (95.2) (83.9) 23.5 34.1 Income Tax 211.2 213.5 22.2 19.5 3.4 1.1 Total Included in Accumulated Other Comprehensive Income (Loss) $ (299.6) $ (304.9) $ (73.0) $ (64.4) $ 26.9 $ 35.2
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, 2023 and 2022. Pension Benefits U.S. Plans U.K. Plan OPEB 2023 2022 2023 2022 2023 2022 (in millions of dollars) Accumulated Other Comprehensive Income (Loss) at Beginning of Year $ (304.9) $ (383.2) $ (64.4) $ (34.0) $ 35.2 $ 21.2 Net Actuarial Gain (Loss) Amortization 15.2 16.3 2.5 0.4 (10.5) (1.0) All Other Changes (7.6) 87.7 (13.8) (41.2) 0.1 19.0 Prior Service Credit (Cost) Amortization — — — — (0.2) (0.2) Change in Income Tax (2.3) (25.7) 2.7 10.4 2.3 (3.8) Accumulated Other Comprehensive Income (Loss) at End of Year $ (299.6) $ (304.9) $ (73.0) $ (64.4) $ 26.9 $ 35.2
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 2023 2022 2023 2022 2023 2022 Benefit Obligations Discount Rate 5.40 % 5.70 % 4.50 % 4.80 % 5.40 % 5.70 % Rate of Compensation Increase N/A N/A 2.40 % 2.50 % N/A N/A Net Periodic Benefit Cost Discount Rate 5.70 % 3.10 % 4.80 % 2.00 % 5.70 % 2.90 % Expected Return on Plan Assets 7.25 % 6.00 % 6.70 % 4.20 % 5.75 % 5.75 % Rate of Compensation Increase N/A N/A 2.50 % 2.90 % N/A N/A
Schedule of Net Benefit Costs	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 2023 2022 2021 2023 2022 2021 2023 2022 2021 (in millions of dollars) Service Cost $ 9.2 $ 7.7 $ 9.6 $ — $ — $ — $ — $ — $ — Interest Cost 87.9 67.2 65.0 7.7 5.0 4.2 4.5 3.0 3.0 Expected Return on Plan Assets (92.0) (105.9) (100.6) (8.5) (10.9) (9.8) (0.5) (0.5) (0.5) Amortization of: Net Actuarial Loss (Gain) 15.2 16.3 21.3 2.5 0.4 1.3 (10.5) (1.0) — Prior Service Credit — — — — — — (0.2) (0.2) (0.2) Total Net Periodic Benefit Cost (Credit) $ 20.3 $ (14.7) $ (4.7) $ 1.7 $ (5.5) $ (4.3) $ (6.7) $ 1.3 $ 2.3
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 2024 $ 83.5 $ 6.7 $ 9.1 $ — $ 9.1 2025 87.0 7.1 8.7 — 8.7 2026 91.2 7.7 8.3 — 8.3 2027 95.1 8.2 8.0 — 8.0 2028 98.8 8.5 7.6 — 7.6 2029-2033 533.2 47.0 31.9 0.1 31.8
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. 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 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, 2023 Quoted Prices Significant Other Significant NAV as a Practical Total (in millions of dollars) Invested Assets Equity Securities: Global $ 55.0 $ — $ — $ 390.8 $ 445.8 Fixed Income Securities: U.S. Government and Agencies 1 215.9 40.8 — — 256.7 Corporate — — — 130.0 130.0 Non-U.S. Emerging Markets — — — 27.9 27.9 Opportunistic Credits — — — 150.6 150.6 Real Estate — — — 162.8 162.8 Alternative Investments: Private Equity Direct Investments — — — 68.5 68.5 Private Equity Funds of Funds — — — 40.7 40.7 Cash Equivalents 16.0 — — — 16.0 Total Invested Assets $ 286.9 $ 40.8 $ — $ 971.3 $ 1,299.0 1 U.S. Government and Agencies Fixed Income Securities includes derivative assets. December 31, 2022 Quoted Prices Significant Significant NAV as a Practical Total (in millions of dollars) Invested Assets Equity Securities: Global $ 57.4 $ — $ — $ 405.7 $ 463.1 Fixed Income Securities: U.S. Government and Agencies 1 194.0 21.7 — — 215.7 Corporate — — — 129.6 129.6 Non-U.S. Emerging Markets — — — 54.0 54.0 Opportunistic Credits — — — 132.3 132.3 Real Estate — — — 164.2 164.2 Alternative Investments: Private Equity Direct Investments — — — 74.5 74.5 Private Equity Funds of Funds — — — 47.6 47.6 Cash Equivalents 20.5 — — — 20.5 Total Invested Assets $ 271.9 $ 21.7 $ — $ 1,007.9 $ 1,301.5 1 U.S. Government and Agencies Fixed Income Securities includes derivative assets.
Pension Plan | Foreign Plan
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. 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, 2023 Quoted Prices Significant Significant NAV as a Practical Total (in millions of dollars) Invested Assets Diversified Growth Assets $ 28.1 $ — $ — $ 5.9 $ 34.0 Fixed Income and Index-linked Securities 75.3 — — — 75.3 Alternative Investments — — — 34.8 34.8 Cash Equivalents 1.3 — — — 1.3 Total Invested Assets $ 104.7 $ — $ — $ 40.7 $ 145.4 December 31, 2022 Quoted Prices Significant Significant NAV as a Practical Total (in millions of dollars) Invested Assets Diversified Growth Assets $ 32.3 $ — $ — $ 8.3 $ 40.6 Fixed Income and Index-linked Securities 70.6 — — — 70.6 Alternative Investments — — — 28.1 28.1 Cash Equivalents 1.9 — — — 1.9 Total Invested Assets $ 104.8 $ — $ — $ 36.4 $ 141.2
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, 2023 Quoted Prices Significant Other Significant Total (in millions of dollars) Assets Life Insurance Contracts $ — $ — $ 8.2 $ 8.2 December 31, 2022 Quoted Prices Significant Other Significant Total (in millions of dollars) Assets Life Insurance Contracts $ — $ — $ 8.5 $ 8.5
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, 2023 and 2022 are as follows: Year Ended December 31, 2023 Beginning Actual Return on Plan Assets Contributions Net Benefits and Expenses Paid End of Year (in millions of dollars) Life Insurance Contracts $ 8.5 $ — $ 8.7 $ (9.0) $ 8.2 Year Ended December 31, 2022 Beginning Actual Return on Plan Assets Contributions Net Benefits and Expenses Paid End of Year (in millions of dollars) Life Insurance Contracts $ 9.0 $ 0.1 $ 9.5 $ (10.1) $ 8.5

Stockholders' Equity and Earn_2

Stockholders' Equity and Earnings Per Common Share (Tables)	12 Months Ended
	Dec. 31, 2023
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 2023 2022 2021 (in millions of dollars, except share data) Numerator Net Income $ 1,283.8 $ 1,407.2 $ 981.0 Denominator (000s) Weighted Average Common Shares - Basic 196,659.7 200,647.2 204,232.9 Dilution for Assumed Exercises of Nonvested Stock Awards 942.3 1,462.2 615.0 Weighted Average Common Shares - Assuming Dilution 197,602.0 202,109.4 204,847.9 Net Income Per Common Share Basic $ 6.53 $ 7.01 $ 4.80 Assuming Dilution $ 6.50 $ 6.96 $ 4.79
Treasury Stock Transactions	Our board of directors has authorized the following repurchase programs: October 2023 Authorization December 2022 Authorization 1 October 2021 Authorization (in millions) Effective Date January 1, 2024 January 1, 2023 October 25, 2021 Expiration Date None December 31, 2023 December 31, 2022 Authorized Repurchase Amount $ 500.0 $ 250.0 $ 250.0 Shares Repurchased Under Repurchase Program $ — $ 250.0 $ 250.0 Remaining Repurchase Amount at December 31, 2023 Not yet effective $ — $ — 1 In February 2023, the December 2022 program was modified to increase the authorized repurchase amount from $200.0 million to $250.0 million. In August 2022, the Inflation Reduction Act was signed into law in the U.S. and imposes a one percent excise tax on corporate stock repurchases effective January 1, 2023. This excise tax is recorded as part of the cost basis of treasury stock and is assessed on the fair market value of stock repurchases reduced by the fair market value of any shares issued during the period. 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 2023 2022 2021 (in millions) Shares Repurchased 5.7 5.7 1.9 Cost of Shares Repurchased 1 $ 252.0 $ 200.1 $ 50.0 1 Includes $0.1 million of commissions for the years ended December 31, 2023 and 2022, respectively. There were no commissions for the year ended December 31, 2021. Also includes $1.9 million of excise tax for the year ended December 31, 2023. There were no excise taxes during the years ended December 31, 2022 and 2021. As a part of our share repurchase program, we periodically enter into accelerated share repurchase agreements (ASR). Under the terms of these agreements, we make a prepayment to a financial counterparty for which we receive an initial delivery of approximately 75 percent of the total Unum Group common stock to be delivered under the agreement. We simultaneously enter into a forward contract indexed to the price of Unum Group common stock, which subjects the transactions to a future price adjustment. Under the terms of the agreements, we are to receive, or be required to pay, a price adjustment based on the volume weighted average price of Unum Group common stock during the term of the agreement, less a discount. Any price adjustment payable to us is settled in shares of Unum Group common stock. Any price adjustment we would be required to pay may be settled in either cash or common stock at our option. Details of our ASRs are as follows: Prepayment Date Prepayment Amount Initial Share Delivery Forward Contract Settlement Date Shares Delivered to Settle Forward Contract (in millions) January 2024 $100.0 1.6 March 2024 Not yet settled July 2023 50.0 0.8 September 2023 0.2 February 2022 50.0 1.3 April 2022 0.4 November 2021 50.0 1.4 November 2021 0.5

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2023
Share-Based Payment Arrangement [Abstract]
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 2020 are as follows: Year Ended December 31, 2020 Expected Volatility (based on our and our peer group historical daily stock prices) 23 % Expected Life (equals the performance period) 3 years Risk Free Interest Rate (based on U.S. Treasury yields at the date of grant) 0.85 %
Activity for CIUs	Activity for CIUs, which are classified as a liability, is as follows: Units (000s) Outstanding at December 31, 2022 15,247 Granted 9,004 Vested 1 (7,223) Outstanding at December 31, 2023 17,028 1 CIUs in the preceding table 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, 2023, the three-year performance period for the 2021 CIU grant was completed and the related awards vested, but the performance factor has not yet been applied. The performance factor will be applied during the first quarter of 2024, with payment of the awards at that time.
Schedule of Cash-based Payment Award, Cash-incentive Units, Valuation Assumptions	The fair value of CIUs is estimated at each reporting period using the Monte-Carlo simulation mode l. Key assumptions used to value CIUs granted are as follows: Assumptions as of the Year Ended December 31, 2023 2023 Grant 2022 Grant Expected Volatility (based on our and our peer group historical daily stock prices) 30 % 27 % Expected Life (equals the performance period) 2 years 1 year Risk Free Interest Rate (based on U.S. Treasury yields at the date of grant) 4.26 % 4.75 % Assumptions as of the Year Ended December 31, 2022 2022 Grant 2021 Grant Expected Volatility (based on our and our peer group historical daily stock prices) 30 % 33 % Expected Life (equals the performance period) 2 years 1 year Risk Free Interest Rate (based on U.S. Treasury yields at the date of grant) 4.26 % 4.60 % Assumptions as of the Year Ended December 31, 2021 2021 Grant Expected Volatility (based on our and our peer group historical daily stock prices) 50 % Expected Life (equals the performance period) 2 years Risk Free Interest Rate (based on U.S. Treasury yields at the date of grant) 0.71 %
Activity for Restricted Stock Units	Activity for RSUs, which are classified as equity, is as follows: Weighted Average Shares Grant Date (000s) Fair Value Outstanding at December 31, 2022 2,182 $ 27.20 Granted 780 45.56 Vested (1,691) 29.54 Forfeited (58) 31.86 Outstanding at December 31, 2023 1,213 35.51
Share-based Payment Arrangement, Cash-Settled Restricted Stock Units, Activity	Activity for cash-settled RSUs, which are classified as a liability, is as follows: Shares (000s) Outstanding at December 31, 2022 23 Vested (23) Outstanding at December 31, 2023 —
Schedule of Compensation Cost for Share-based Payment Arrangements	Compensation expense for the stock based plans, as reported in our consolidated statements of income, is as follows: Year Ended December 31 2023 2022 2021 (in millions of dollars) Performance Share Units $ 0.3 $ 5.7 $ 3.3 Cash Incentive Units 21.7 12.8 3.2 Restricted Stock Units and Cash-Settled Restricted Stock Units 40.6 32.7 25.5 Stock Success Units 0.9 0.9 2.8 Other 0.6 0.6 0.6 Total Compensation Expense, Before Income Tax $ 64.1 $ 52.7 $ 35.4 Total Compensation Expense, Net of Income Tax $ 57.5 $ 47.3 $ 31.1

Reinsurance (Tables)

Reinsurance (Tables)	12 Months Ended
	Dec. 31, 2023
Reinsurance Disclosures [Abstract]
Effects of Reinsurance	Reinsurance activity related to our premium income, policy benefits, and policy benefits remeasurement gain are as follows: Year Ended December 31 2023 2022 2021 (in millions of dollars) Direct Premium Income $ 10,286.8 $ 9,893.6 $ 9,736.8 Reinsurance Assumed 80.4 78.7 90.6 Reinsurance Ceded (321.2) (355.8) (352.4) Net Premium Income $ 10,046.0 $ 9,616.5 $ 9,475.0 Direct Policy Benefits $ 8,001.8 $ 8,205.3 $ 8,817.1 Reinsurance Assumed 138.7 135.1 145.0 Reinsurance Ceded (828.6) (798.3) (848.8) Net Policy Benefits $ 7,311.9 $ 7,542.1 $ 8,113.3 Direct Policy Benefits - Remeasurement Gain $ (49.2) $ (372.5) $ (546.2) Reinsurance Assumed (0.1) 36.4 1.9 Reinsurance Ceded (5.5) (211.4) (15.6) Net Policy Benefits - Remeasurement Gain $ (54.8) $ (547.5) $ (559.9)

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2023
Segment Reporting [Abstract]
Premium Income by Major Line of Business within Each Segment	Segment information is shown below. Certain prior year amounts were reclassified to conform to current year presentation. Year Ended December 31 2023 2022 2021 (in millions of dollars) Premium Income Unum US Group Disability Group Long-term Disability $ 2,057.2 $ 1,911.7 $ 1,827.8 Group Short-term Disability 1,012.3 926.3 864.0 Group Life and Accidental Death & Dismemberment Group Life 1,679.0 1,669.1 1,641.9 Accidental Death & Dismemberment 175.5 173.7 165.1 Supplemental and Voluntary Voluntary Benefits 850.1 833.7 840.7 Individual Disability 527.0 461.1 459.8 Dental and Vision 278.1 275.8 272.7 6,579.2 6,251.4 6,072.0 Unum International Unum UK Group Long-term Disability 396.1 376.9 401.9 Group Life 169.3 138.2 112.3 Supplemental 141.5 114.0 112.6 Unum Poland 118.3 89.7 90.2 825.2 718.8 717.0 Colonial Life Accident, Sickness, and Disability 946.1 948.9 953.3 Life 426.5 401.1 384.7 Cancer and Critical Illness 353.5 352.0 352.2 1,726.1 1,702.0 1,690.2 Closed Block Long-term Care 696.0 697.4 704.3 All Other 219.5 246.9 291.5 915.5 944.3 995.8 Total Premium Income $ 10,046.0 $ 9,616.5 $ 9,475.0
Selected Operating Statement Data by Segment	Unum US Unum International Colonial Life Closed Block Corporate Total (in millions of dollars) Year Ended December 31, 2023 Premium Income $ 6,579.2 $ 825.2 $ 1,726.1 $ 915.5 $ — $ 10,046.0 Net Investment Income 639.9 137.2 153.5 1,066.3 99.8 2,096.7 Other Income 220.5 1.6 1.2 52.6 3.3 279.2 Adjusted Operating Revenue $ 7,439.6 $ 964.0 $ 1,880.8 $ 2,034.4 $ 103.1 $ 12,421.9 Adjusted Operating Income (Loss) $ 1,355.5 $ 158.1 $ 400.1 $ 164.9 $ (146.4) $ 1,932.2 Interest and Debt Expense $ — $ — $ — $ — $ 194.8 $ 194.8 DAC Amortization $ 267.6 $ 8.4 $ 205.4 $ — $ — $ 481.4 Depreciation and Intangible Amortization $ 76.3 $ 14.6 $ 13.6 $ 5.2 $ 0.6 $ 110.3 Year Ended December 31, 2022 Premium Income $ 6,251.4 $ 718.8 $ 1,702.0 $ 944.3 $ — $ 9,616.5 Net Investment Income 676.3 170.1 152.7 1,070.6 52.5 2,122.2 Other Income 196.3 0.9 1.1 58.0 4.8 261.1 Adjusted Operating Revenue $ 7,124.0 $ 889.8 $ 1,855.8 $ 2,072.9 $ 57.3 $ 11,999.8 Adjusted Operating Income (Loss) $ 972.6 $ 134.0 $ 412.9 $ 251.9 $ (164.3) $ 1,607.1 Interest and Debt Expense $ — $ — $ — $ — $ 188.5 $ 188.5 Costs Related to Early Retirement of Debt $ — $ — $ — $ — $ 4.2 $ 4.2 DAC Amortization $ 240.9 $ 8.2 $ 172.0 $ — $ — $ 421.1 Depreciation and Intangible Amortization $ 75.7 $ 14.4 $ 15.0 $ 4.7 $ 0.6 $ 110.4 Year Ended December 31, 2021 Premium Income $ 6,072.0 $ 717.0 $ 1,690.2 $ 995.8 $ — $ 9,475.0 Net Investment Income 721.6 132.7 172.0 1,159.0 27.9 2,213.2 Other Income 170.0 0.6 1.0 65.1 6.2 242.9 Adjusted Operating Revenue $ 6,963.6 $ 850.3 $ 1,863.2 $ 2,219.9 $ 34.1 $ 11,931.1 Adjusted Operating Income (Loss) $ 398.9 $ 105.7 $ 404.3 $ 420.1 $ (177.9) $ 1,151.1 Interest and Debt Expense $ — $ — $ — $ — $ 185.0 $ 185.0 Costs Related to Early Retirement of Debt $ — $ — $ — $ — $ 67.3 $ 67.3 DAC Amortization $ 285.9 $ 7.0 $ 159.2 $ — $ — $ 452.1 Depreciation and Intangible Amortization $ 81.9 $ 13.0 $ 16.3 $ 5.1 $ 0.7 $ 117.0
Assets by Segment	December 31 2023 2022 (in millions of dollars) Assets Unum US $ 15,561.1 $ 16,356.3 Unum International 3,372.9 3,129.4 Colonial Life 4,830.4 4,575.0 Closed Block 35,272.8 33,776.6 Corporate 4,218.0 3,311.2 Total Assets $ 63,255.2 $ 61,148.5
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 2023 2022 2021 (in millions of dollars) Total Revenue $ 12,385.9 $ 11,984.1 $ 12,007.8 Excluding: Net Investment Gain (Loss) (36.0) (15.7) 76.7 Adjusted Operating Revenue $ 12,421.9 $ 11,999.8 $ 11,931.1 Income Before Income Tax $ 1,640.1 $ 1,750.0 $ 1,260.6 Excluding: Net Investment Gains and Losses Net Realized Investment Gain Related to Reinsurance Transaction — — 67.6 Net Investment Gain (Loss), Other (36.0) (15.7) 9.1 Total Net Investment Gain (Loss) (36.0) (15.7) 76.7 Items Related to Closed Block Individual Disability Reinsurance Transaction Amortization of the Cost of Reinsurance (44.1) (50.3) (69.8) Non-Contemporaneous Reinsurance (34.8) (34.4) (32.9) Transaction Costs — — (6.2) Total Items Related to Closed Block Individual Disability Reinsurance Transaction (78.9) (84.7) (108.9) Reserve Assumption Updates (177.2) 243.3 235.0 Impairment Loss on Internal-Use Software — — (12.1) Cost Related to Early Retirement of Debt — — (67.3) Impairment Loss on ROU Asset — — (13.9) Adjusted Operating Income $ 1,932.2 $ 1,607.1 $ 1,151.1

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2023
Leases [Abstract]
Lease, Cost	Operating lease information is as follows: Year Ended December 31 2023 2022 2021 (in millions of dollars) Lease Cost Operating Lease Cost $ 16.4 $ 19.6 $ 35.2 Sublease Income (1.5) (1.1) (1.0) Total Lease Cost $ 14.9 $ 18.5 $ 34.2 Other Information Cash Paid for Amounts Included in the Measurement of Lease Liabilities $ 20.3 $ 23.1 $ 29.9 Weighted-Average Remaining Lease Term 5 years 6 years 6 years Weighted-Average Discount Rate 4.85 % 4.32 % 4.45 %
Lessee, Operating Lease, Liability, Maturity	As of December 31, 2023, aggregate undiscounted minimum lease payments and the reconciliation to our lease liability are as follows (in millions of dollars): 2024 $ 19.2 2025 13.9 2026 11.1 2027 9.3 2028 9.0 2029 and Thereafter 9.1 Total 71.6 Less Imputed Interest 9.0 Lease Liability $ 62.6

Statutory Financial Informati_2

Statutory Financial Information (Tables)	12 Months Ended
	Dec. 31, 2023
Statutory Financial Information [Abstract]
Statutory Permitted Practices Disclosure	Additional information regarding the Unum America PDR is as follows: Year Ended December 31 2023 2022 2021 (in millions of dollars) Premium Deficiency Reserve Gross Premium Deficiency Reserve 1 $ 1,604 $ 2,851 $ 2,977 Cumulative Gross Premium Deficiency Reserve Recognized 1,604 1,191 667 Remaining Premium Deficiency Reserve to be Recognized $ — $ 1,660 $ 2,310 1 The gross PDR decreased by $1,247 million during 2023 due primarily to changes in the assumed reinvestment rate as well as premium rate increase activity. The gross PDR decreased by $126 million during 2022 due primarily to premium rate increase activity and underlying growth in the locked-in statutory reserve basis. The gross PDR increased by $687 million during 2021 due primarily to changes in the assumed reinvestment rate. The increase for 2021 was from a gross PDR of $2,290 million as of December 31, 2020, which was an increase from the original $2,100 million reserve deficiency as of December 31, 2018.
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 2023 2022 2021 (in millions of dollars) Combined Net Income (Loss) Traditional U.S. Life Insurance Subsidiaries $ 1,329.9 $ 965.4 $ 779.5 Captive Reinsurers $ (318.3) $ (432.2) $ (159.0) Combined Net Gain (Loss) from Operations, After Tax Traditional U.S. Life Insurance Subsidiaries $ 1,351.5 $ 965.4 $ 681.1 Captive Reinsurers $ (279.4) $ (428.6) $ (247.4) December 31 2023 2022 (in millions of dollars) Combined Capital and Surplus Traditional U.S. Life Insurance Subsidiaries $ 3,751.3 $ 3,816.3 Captive Reinsurers $ 1,534.9 $ 1,229.6

Schedule II Condensed Financial

Schedule II Condensed Financial Information of Registrant (Tables) - Parent Company	12 Months Ended
	Dec. 31, 2023
Condensed Financial Statements, Captions
Condensed Balance Sheet of Parent Company	BALANCE SHEETS December 31 2023 2022 (in millions of dollars) Assets Fixed Maturity Securities - at fair value (amortized cost: $656.2; $748.1) $ 596.1 $ 657.7 Other Long-term Investments 27.0 19.3 Short-term Investments 970.9 845.8 Investment in Subsidiaries 11,663.6 10,815.7 Deferred Income Tax 118.1 114.9 Other Assets 593.6 555.5 Total Assets $ 13,969.3 $ 13,008.9 Liabilities and Stockholders' Equity Liabilities Short-term Debt $ — $ 2.0 Long-term Debt 3,430.4 3,427.8 Pension and Postretirement Benefits 350.2 352.6 Other Liabilities 537.3 491.5 Total Liabilities 4,317.9 4,273.9 Stockholders' Equity Common Stock, $0.10 par Authorized: 725,000,000 shares Issued: 194,588,625 and 308,306,490 shares 19.4 30.8 Additional Paid-in Capital 1,547.8 2,441.0 Accumulated Other Comprehensive Loss (3,308.0) (3,448.3) Retained Earnings 11,431.5 13,141.3 Treasury Stock - at cost: 1,216,528 and 110,551,977 shares (39.3) (3,429.8) Total Stockholders' Equity 9,651.4 8,735.0 Total Liabilities and Stockholders' Equity $ 13,969.3 $ 13,008.9
Condensed Income Statement of Parent Company	STATEMENTS OF INCOME Year Ended December 31 2023 2022 2021 (in millions of dollars) Cash Dividends from Subsidiaries $ 1,581.1 $ 1,306.6 $ 909.8 Non-Cash Dividends from Subsidiaries — 23.0 719.6 Other Income 90.3 81.8 53.5 Total Revenue 1,671.4 1,411.4 1,682.9 Interest and Debt Expense 194.8 188.5 185.9 Cost Related to Early Retirement of Debt — 4.2 67.3 Other Expenses 54.2 35.6 39.1 Total Expenses 249.0 228.3 292.3 Income of Parent Company Before Income Tax 1,422.4 1,183.1 1,390.6 Income Tax Expense (Benefit) (9.5) 14.7 (24.1) Income of Parent Company 1,431.9 1,168.4 1,414.7 Equity in Undistributed Earnings (Loss) of Subsidiaries (148.1) 238.8 (433.7) Net Income 1,283.8 1,407.2 981.0 Other Comprehensive Income, Net of Tax 140.3 1,716.3 1,145.6 Comprehensive Income $ 1,424.1 $ 3,123.5 $ 2,126.6
Condensed Cash Flow Statement of Parent Company	STATEMENTS OF CASH FLOWS Year Ended December 31 2023 2022 2021 (in millions of dollars) Cash Provided by Operating Activities $ 1,548.0 $ 1,250.2 $ 861.0 Cash Flows from Investing Activities Proceeds from Sales and Maturities of Fixed Maturity Securities 97.1 192.1 245.5 Proceeds from Sales and Maturities of Other Investments 23.9 7.4 20.1 Purchase of Fixed Maturity Securities (44.5) (102.7) (2.0) Purchase of Other Investments (23.4) (32.0) (0.9) Net Purchases of Short-term Investments (104.4) (209.6) (465.0) Cash Distributions to Subsidiaries (854.5) (540.2) (300.9) Net Purchases of Property and Equipment (113.1) (94.0) (91.3) Cash Used by Investing Activities (1,018.9) (779.0) (594.5) Cash Flows from Financing Activities Short-term Debt Repayment (2.0) — — Issuance of Long-term Debt — 349.2 588.1 Long-term Debt Repayment — (364.0) (500.0) Cost Related to Early Retirement of Debt — (3.6) (62.8) Issuance of Common Stock 5.2 4.0 3.4 Repurchase of Common Stock (250.1) (200.1) (50.0) Dividends Paid to Stockholders (277.1) (254.2) (239.4) Other, Net — 0.7 (1.6) Cash Used by Financing Activities (524.0) (468.0) (262.3) Increase in Cash $ 5.1 $ 3.2 $ 4.2

Significant Accounting Polici_3

Significant Accounting Policies - Additional Information (Detail) $ / shares in Units, $ in Millions		12 Months Ended
		Dec. 31, 2023 USD ($) Integer $ / shares	Dec. 31, 2022 USD ($) $ / shares		Dec. 31, 2022 USD ($) $ / shares		Dec. 31, 2021 USD ($) $ / shares		Dec. 31, 2021 USD ($) $ / shares	Jan. 01, 2021 USD ($)		Dec. 31, 2020 USD ($)
New Accounting Pronouncements or Change in Accounting Principle
Number of Operating Segments | Integer		3
Premium Income		$ 10,046	$ 9,616.5				$ 9,475
Commissions		1,170.1	1,086.4				1,038.1
Ceded Policy Loans		3,322.5	3,312.5		$ 3,312.5
Premium Receivable, Allowance for Credit Loss		29.5	32.5		32.5
Premiums Receivable, Gross		612.4	557.6		557.6
Premium Receivable, Credit Loss Expense (Reversal)		(3)	(1.7)
Accumulated Depreciation for Property and Equipment		1,422.8	1,328.7		1,328.7
Value of Business Acquired		63.9	62.9		62.9
Accumulated Amortization of Value of Business Acquired		161.8	150.3		150.3
Amortization of Value of Business Acquired		5.2	4.9				5.7
Prepaid Reinsurance Premiums		549.4	593.5		593.5
Deferred Gain on Reinsurance		8.8	3.1		3.1
Reinsurance Recoverable, Allowance for Credit Loss		1.7	1.7		1.7
Reinsurance Recoverable, Credit Loss Expense (Reversal)			(0.6)
Premium Tax Expense		183.5	169.3				166
Participation Fund Account Assets (PFA)		244.4	250.2		250.2
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		(3,308)	(3,448.3)		(3,448.3)		(5,164.6)		$ (5,164.6)	$ 4,166		$ (6,310.2)
Deferred Acquisition Costs		2,714.5	2,560		2,560					2,357.7
Reinsurance Recoverables		9,108.4	9,608		9,608
Deferred Income Tax Assets, Net		649.4	586		586
Other Assets		1,661.7	1,666.6	[1]	1,666.6	[1]
Total Assets		63,255.2	61,148.5		61,148.5
Policy and Contract Benefits	[2]		0		0
Reserves for Future Policy and Contract Benefits	[2]		0		0
Future Policy Benefits		40,009.4	38,577.1	[2]	38,577.1	[2]
Policyholders' Account Balances		5,667.7	5,740.2	[2]	5,740.2	[2]
Unearned Premiums		380.2	365.5		365.5
Deferred Income Tax		27	25.2		25.2
Liabilities		53,603.8	52,413.5		52,413.5
Accumulated Other Comprehensive Loss		(3,308)	(3,448.3)		(3,448.3)		(5,164.6)		(5,164.6)	(6,310.2)
Retained Earnings		11,431.5	13,141.3		13,141.3		11,989.4		11,989.4	11,249
Total Stockholders' Equity		9,651.4	8,735		8,735		6,033.9		6,033.9
Policy Benefits		7,311.9	7,542.1	[3]			8,113.3	[3]
Liability for Future Policy Benefit, Remeasurement Gain (Loss)		(54.8)	(547.5)				(559.9)
Deferral of Acquisition Costs		(632.2)	(556.9)				(523.2)
Amortization of Deferred Acquisition Costs		481.4	421.1				452.1
Other Expenses		1,112	1,006.7				999.3
Income Tax - Deferred		(95.7)	(130.7)				66.8
Net Income		$ 1,283.8	$ 1,407.2				$ 981
Basic Earnings Per Share | $ / shares		$ 6.53	$ 7.01				$ 4.80
Diluted Earnings Per Share | $ / shares		$ 6.50	$ 6.96				$ 4.79
Change in Adjustment to Deferred Acquisition Costs and Reserves for Future Policy and Contract Benefits, Net of Reinsurance and Net of Tax Expense Benefit			$ 0				$ 0
Change in the Effect of Discount Rate Assumptions on the Liability for Future Policy Benefits, Net of Reinsurance (net of tax expense (benefit) of $(256.5); $2,385.1; $622.8)		$ (962.3)	8,884.6				2,361.8
Change in Foreign Currency Translation Adjustment		69	(116)				(12.8)
Comprehensive Income (Loss)		1,424.1	3,123.5				2,126.6
Other Comprehensive Income (Loss), Net of Tax		140.3	1,716.3				1,145.6
Increase (Decrease) in Receivables		602.7	590.6				676.1
Deferral of Acquisition Costs		(150.8)	(135.8)				(71.1)
Change in Insurance Reserves and Liabilities		(313.2)	(244.7)				37.7
Change in Income Taxes		(84.3)	(31.3)				335.3
Amortization of the Cost of Reinsurance		44.1	50.3				69.8
Other Noncash Income (Expense)		(9.2)	17.1				15.8
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest										11,249
Total Stockholders' Equity		11,431.5	13,141.3		13,141.3		11,989.4		11,989.4			11,249
Net Income		1,283.8	1,407.2				981
Accumulated Other Comprehensive Income (Loss)
New Accounting Pronouncements or Change in Accounting Principle
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest										(6,310.2)
Total Stockholders' Equity		(3,308)	(3,448.3)		(3,448.3)		(5,164.6)		(5,164.6)			(6,310.2)
Other Comprehensive Income (Loss), Net of Tax		140.3	1,716.3				1,145.6
Operating Segments
New Accounting Pronouncements or Change in Accounting Principle
Premium Income		10,046	9,616.5				9,475
Liability for Future Policy Benefit, before Reinsurance, after Other		39,759.1	38,357.7		38,357.7		51,779.6		51,779.6	55,585.4
Liability for Future Policy Benefit, Reinsurance Recoverable, after Allowance		7,756.1	8,128.2		8,128.2		10,348.2		10,348.2	10,496	[4]
Liability for Future Policy Benefit, after Reinsurance		32,003	30,229.5		30,229.5		41,431.4		41,431.4	45,089.4
Deferred Acquisition Costs		2,714.5	2,560		2,560		2,427.4		2,427.4			2,357.7
Future Policy Benefits		40,009.4	38,577.1		38,577.1		51,991.6		51,991.6
Policyholders' Account Balances		5,667.7	5,740.2		5,740.2		5,814.8		5,814.8
Amortization of Deferred Acquisition Costs		481.4	421.1				452.1
Unum US
New Accounting Pronouncements or Change in Accounting Principle
Liability for Future Policy Benefit, before Reinsurance, after Other		9,352.7	9,668.7		9,668.7		12,020		12,020	12,861.4
Liability for Future Policy Benefit, Reinsurance Recoverable, after Allowance		208.6	251.2		251.2		308.4		308.4	357.7	[4]
Liability for Future Policy Benefit, after Reinsurance		9,144.1	9,417.5		9,417.5		11,711.6		11,711.6	12,503.7
Deferred Acquisition Costs		1,232.2	1,185.1		1,185.1		1,152.9		1,152.9	1,181		1,181
Future Policy Benefits	[5]	9,352.7	9,668.7		9,668.7		12,020		12,020
Amortization of Deferred Acquisition Costs		267.6	240.9				285.9
Unum US | Group Disability
New Accounting Pronouncements or Change in Accounting Principle
Liability for Future Policy Benefit, before Reinsurance, after Other		5,147.6	5,533.7		5,533.7		6,726.2		6,726.2	7,295.7
Liability for Future Policy Benefit, Reinsurance Recoverable, after Allowance		30.7	36		36		40.9		40.9	58.3
Liability for Future Policy Benefit, after Reinsurance		5,116.9	5,497.7		5,497.7		6,685.3		6,685.3	7,237.4
Deferred Acquisition Costs		63.6	61		61		60.9		60.9			95.3
Amortization of Deferred Acquisition Costs		57.6	53				84.2
Unum US | Group Life and AD&D
New Accounting Pronouncements or Change in Accounting Principle
Liability for Future Policy Benefit, before Reinsurance, after Other		923	973.5		973.5		1,125.3		1,125.3	1,127.3
Liability for Future Policy Benefit, Reinsurance Recoverable, after Allowance		7.2	7.5		7.5		4.4		4.4	3
Liability for Future Policy Benefit, after Reinsurance		915.8	966		966		1,120.9		1,120.9	1,124.3
Deferred Acquisition Costs		48.9	49.3		49.3		53.9		53.9			76.4
Amortization of Deferred Acquisition Costs		39	41.9				58.6
Unum US | Individual Disability
New Accounting Pronouncements or Change in Accounting Principle
Liability for Future Policy Benefit, before Reinsurance, after Other		2,079.7	2,014.6		2,014.6		2,582		2,582	2,767.7
Liability for Future Policy Benefit, Reinsurance Recoverable, after Allowance		156.7	193.6		193.6		231.9		231.9	260.6
Liability for Future Policy Benefit, after Reinsurance		1,923	1,821		1,821		2,350.1		2,350.1	2,507.1
Deferred Acquisition Costs		497.8	464.4		464.4		441.8		441.8			423.6
Amortization of Deferred Acquisition Costs		54	49.4				45.7
Unum US | Voluntary Benefits
New Accounting Pronouncements or Change in Accounting Principle
Liability for Future Policy Benefit, before Reinsurance, after Other		1,202.4	1,146.9		1,146.9		1,586.5		1,586.5	1,659.2
Liability for Future Policy Benefit, Reinsurance Recoverable, after Allowance		14	14.1		14.1		31.2		31.2	35.7
Liability for Future Policy Benefit, after Reinsurance		1,188.4	1,132.8		1,132.8		1,555.3		1,555.3	1,623.5
Deferred Acquisition Costs		610.6	601		601		588.6		588.6			569.7
Policyholders' Account Balances		678.1	679.7		679.7		681.6		681.6
Amortization of Deferred Acquisition Costs		106.2	87.6				80.5
Unum US | Dental and Vision
New Accounting Pronouncements or Change in Accounting Principle
Liability for Future Policy Benefit, before Reinsurance, after Other										11.5
Liability for Future Policy Benefit, Reinsurance Recoverable, after Allowance										0.1
Liability for Future Policy Benefit, after Reinsurance										11.4
Deferred Acquisition Costs		11.3	9.4		9.4		7.7		7.7			16
Amortization of Deferred Acquisition Costs		10.8	9				16.9
Unum US | Operating Segments
New Accounting Pronouncements or Change in Accounting Principle
Premium Income		6,579.2	6,251.4				6,072
Total Assets		15,561.1	16,356.3		16,356.3
Amortization of Deferred Acquisition Costs		267.6	240.9				285.9
Unum US | Operating Segments | Voluntary Benefits
New Accounting Pronouncements or Change in Accounting Principle
Premium Income		850.1	833.7				840.7
Unum US | Operating Segments | Dental and Vision
New Accounting Pronouncements or Change in Accounting Principle
Premium Income		278.1	275.8				272.7
Unum International
New Accounting Pronouncements or Change in Accounting Principle
Liability for Future Policy Benefit, before Reinsurance, after Other		2,293.2	2,063.2		2,063.2		2,955.8		2,955.8	3,203.4
Liability for Future Policy Benefit, Reinsurance Recoverable, after Allowance		78.7	70.3		70.3		125.3		125.3	132.5	[4]
Liability for Future Policy Benefit, after Reinsurance		2,214.5	1,992.9		1,992.9		2,830.5		2,830.5	3,070.9
Deferred Acquisition Costs		46.9	37		37		36.4		36.4	32		32
Future Policy Benefits		2,293.2	2,063.2		2,063.2		2,955.8		2,955.8
Amortization of Deferred Acquisition Costs		8.4	8.2				7
Unum International | Operating Segments
New Accounting Pronouncements or Change in Accounting Principle
Premium Income		825.2	718.8				717
Total Assets		3,372.9	3,129.4		3,129.4
Amortization of Deferred Acquisition Costs		8.4	8.2				7
Colonial Life
New Accounting Pronouncements or Change in Accounting Principle
Liability for Future Policy Benefit, before Reinsurance, after Other		1,997.8	1,858.4		1,858.4		2,482.9		2,482.9	2,528.6
Liability for Future Policy Benefit, Reinsurance Recoverable, after Allowance		1.8	1.1		1.1		2.3		2.3	4.4	[4]
Liability for Future Policy Benefit, after Reinsurance		1,996	1,857.3		1,857.3		2,480.6		2,480.6	2,524.2
Deferred Acquisition Costs		1,435.4	1,337.9		1,337.9		1,238.1		1,238.1	1,144.7		1,144.7
Future Policy Benefits		1,997.8	1,858.4		1,858.4		2,482.9		2,482.9
Policyholders' Account Balances		869.8	869.1		869.1		870.7		870.7
Amortization of Deferred Acquisition Costs		205.4	172				159.2
Colonial Life | Operating Segments
New Accounting Pronouncements or Change in Accounting Principle
Premium Income		1,726.1	1,702				1,690.2
Total Assets		4,830.4	4,575		4,575
Amortization of Deferred Acquisition Costs		205.4	172				159.2
Closed Block
New Accounting Pronouncements or Change in Accounting Principle
Liability for Future Policy Benefit, before Reinsurance, after Other		26,115.4	24,767.4		24,767.4		34,320.9		34,320.9	36,992
Liability for Future Policy Benefit, Reinsurance Recoverable, after Allowance		7,466.9	7,805.5		7,805.5		9,912.1		9,912.1	10,001.4	[4]
Liability for Future Policy Benefit, after Reinsurance		18,648.5	16,961.9		16,961.9		24,408.8		24,408.8	26,990.6
Future Policy Benefits	[5]	26,115.4	24,767.4		24,767.4		34,320.9		34,320.9
Closed Block | Long-term Care
New Accounting Pronouncements or Change in Accounting Principle
Liability for Future Policy Benefit, before Reinsurance, after Other		16,597.3	14,811.6		14,811.6		21,714.7		21,714.7	22,740.9
Liability for Future Policy Benefit, Reinsurance Recoverable, after Allowance		4.5	5.7		5.7		7.4		7.4	44.4
Liability for Future Policy Benefit, after Reinsurance		16,592.8	14,805.9		14,805.9		21,707.3		21,707.3	22,696.5
Closed Block | Other Insurance Product Line
New Accounting Pronouncements or Change in Accounting Principle
Liability for Future Policy Benefit, before Reinsurance, after Other		9,518.1	9,955.8		9,955.8		12,606.2		12,606.2	14,251.1
Liability for Future Policy Benefit, Reinsurance Recoverable, after Allowance		7,462.4	7,799.8		7,799.8		9,904.7		9,904.7	9,957
Liability for Future Policy Benefit, after Reinsurance		2,055.7	2,156		2,156		2,701.5		2,701.5	4,294.1
Policyholders' Account Balances		4,119.8	4,191.4		4,191.4		4,262.5		4,262.5
Closed Block | Operating Segments
New Accounting Pronouncements or Change in Accounting Principle
Premium Income		915.5	944.3				995.8
Total Assets		35,272.8	33,776.6		33,776.6
Amortization of Deferred Acquisition Costs		0	0				0
Closed Block | Operating Segments | Long-term Care
New Accounting Pronouncements or Change in Accounting Principle
Premium Income		696	697.4				704.3
Closed Block | Operating Segments | Other Insurance Product Line
New Accounting Pronouncements or Change in Accounting Principle
Premium Income		219.5	246.9				291.5
Previously Reported
New Accounting Pronouncements or Change in Accounting Principle
Premium Income			9,623.4				9,481
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest												10,871
Deferred Acquisition Costs			2,252.3		2,252.3							2,272.6
Reinsurance Recoverables			10,218.6		10,218.6
Deferred Income Tax Assets, Net			449.8		449.8
Other Assets	[1]		1,786.3		1,786.3
Total Assets			61,434.9		61,434.9
Policy and Contract Benefits	[2]		1,839.8		1,839.8
Reserves for Future Policy and Contract Benefits	[2]		42,330.2		42,330.2
Future Policy Benefits	[2]		0		0
Policyholders' Account Balances	[2]		0		0
Unearned Premiums			352.7		352.7
Deferred Income Tax			9.2		9.2
Liabilities			52,237.4		52,237.4
Accumulated Other Comprehensive Loss			(2,756.6)		(2,756.6)		354.1		354.1	374.2
Retained Earnings			12,912.1		12,912.1		11,853.2		$ 11,853.2	11,269.6
Total Stockholders' Equity			9,197.5		$ 9,197.5
Policy Benefits	[3]		6,936.7				7,598.6
Liability for Future Policy Benefit, Remeasurement Gain (Loss)			0				0
Deferral of Acquisition Costs							(508.1)
Amortization of Deferred Acquisition Costs			591				586.1
Other Expenses			1,020.2				1,008.6
Income Tax - Deferred			(156.3)				26
Net Income			1,314.2				824.2
Basic Earnings Per Share | $ / shares					$ 6.55				$ 4.04
Diluted Earnings Per Share | $ / shares					$ 6.50				$ 4.02
Change in Adjustment to Deferred Acquisition Costs and Reserves for Future Policy and Contract Benefits, Net of Reinsurance and Net of Tax Expense Benefit			4,056.9				1,195.9
Change in the Effect of Discount Rate Assumptions on the Liability for Future Policy Benefits, Net of Reinsurance (net of tax expense (benefit) of $(256.5); $2,385.1; $622.8)			0				0
Change in Foreign Currency Translation Adjustment			(115.2)				(12.6)
Comprehensive Income (Loss)			(1,796.5)				804.1
Other Comprehensive Income (Loss), Net of Tax			(3,110.7)				(20.1)
Increase (Decrease) in Receivables			566				678
Deferral of Acquisition Costs			34.1				78
Change in Insurance Reserves and Liabilities			(282)				74.2
Change in Income Taxes			(58.8)				295.3
Amortization of the Cost of Reinsurance			63.8				79.1
Other Noncash Income (Expense)			16.1
Previously Reported | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest												11,269.6
Previously Reported | Accumulated Other Comprehensive Income (Loss)
New Accounting Pronouncements or Change in Accounting Principle
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest												374.2
Previously Reported | Operating Segments
New Accounting Pronouncements or Change in Accounting Principle
Liability for Future Policy Benefit, before Reinsurance, after Other	[6]											45,704.4
Previously Reported | Unum US
New Accounting Pronouncements or Change in Accounting Principle
Liability for Future Policy Benefit, before Reinsurance, after Other	[6]											12,184.6
Deferred Acquisition Costs												1,168.7
Previously Reported | Unum US | Group Disability
New Accounting Pronouncements or Change in Accounting Principle
Liability for Future Policy Benefit, before Reinsurance, after Other												7,409
Previously Reported | Unum US | Group Life and AD&D
New Accounting Pronouncements or Change in Accounting Principle
Liability for Future Policy Benefit, before Reinsurance, after Other												1,123.9
Previously Reported | Unum US | Individual Disability
New Accounting Pronouncements or Change in Accounting Principle
Liability for Future Policy Benefit, before Reinsurance, after Other												2,485.3
Previously Reported | Unum US | Voluntary Benefits
New Accounting Pronouncements or Change in Accounting Principle
Liability for Future Policy Benefit, before Reinsurance, after Other												1,154.9
Previously Reported | Unum US | Dental and Vision
New Accounting Pronouncements or Change in Accounting Principle
Liability for Future Policy Benefit, before Reinsurance, after Other												11.5
Previously Reported | Unum International
New Accounting Pronouncements or Change in Accounting Principle
Liability for Future Policy Benefit, before Reinsurance, after Other	[6]											2,969.8
Deferred Acquisition Costs												32
Previously Reported | Colonial Life
New Accounting Pronouncements or Change in Accounting Principle
Liability for Future Policy Benefit, before Reinsurance, after Other	[6]											1,977.2
Deferred Acquisition Costs												1,071.9
Previously Reported | Closed Block
New Accounting Pronouncements or Change in Accounting Principle
Liability for Future Policy Benefit, before Reinsurance, after Other	[6]											28,572.8
Previously Reported | Closed Block | Long-term Care
New Accounting Pronouncements or Change in Accounting Principle
Liability for Future Policy Benefit, before Reinsurance, after Other												16,283.4
Previously Reported | Closed Block | Other Insurance Product Line
New Accounting Pronouncements or Change in Accounting Principle
Liability for Future Policy Benefit, before Reinsurance, after Other												$ 12,289.4
Accounting Standards Update 2018-12 | Revision of Prior Period, Accounting Standards Update, Adjustment
New Accounting Pronouncements or Change in Accounting Principle
Premium Income			(6.9)				(6)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest										(6,705)
Deferred Acquisition Costs			307.7		$ 307.7
Removal of Shadow Adjustments, DAC										85.1
Reinsurance Recoverables			(610.6)		(610.6)
Deferred Income Tax Assets, Net			136.2		136.2
Other Assets	[1]		(119.7)		(119.7)
Total Assets			(286.4)		(286.4)
Policy and Contract Benefits	[2]		(1,839.8)		(1,839.8)
Reserves for Future Policy and Contract Benefits	[2]		(42,330.2)		(42,330.2)
Future Policy Benefits	[2]		38,577.1		38,577.1
Policyholders' Account Balances	[2]		5,740.2		5,740.2
Unearned Premiums			12.8		12.8
Deferred Income Tax			16		16
Liabilities			176.1		176.1
Accumulated Other Comprehensive Loss			(691.7)		(691.7)		(5,518.7)		$ (5,518.7)	(6,684.4)
Retained Earnings			229.2		229.2		136.2		$ 136.2	(20.6)
Total Stockholders' Equity			(462.5)		$ (462.5)
Policy Benefits	[3]		605.4				514.7
Liability for Future Policy Benefit, Remeasurement Gain (Loss)			(547.5)				(559.9)
Deferral of Acquisition Costs							(15.1)
Amortization of Deferred Acquisition Costs			(169.9)				(134)
Other Expenses			(13.5)				(9.3)
Income Tax - Deferred			25.6				40.8
Net Income			93				156.8
Basic Earnings Per Share | $ / shares					$ 0.46				$ 0.76
Diluted Earnings Per Share | $ / shares					$ 0.46				$ 0.77
Change in Adjustment to Deferred Acquisition Costs and Reserves for Future Policy and Contract Benefits, Net of Reinsurance and Net of Tax Expense Benefit			(4,056.9)				(1,195.9)
Change in the Effect of Discount Rate Assumptions on the Liability for Future Policy Benefits, Net of Reinsurance (net of tax expense (benefit) of $(256.5); $2,385.1; $622.8)			8,884.6				2,361.8
Change in Foreign Currency Translation Adjustment			(0.8)				(0.2)
Comprehensive Income (Loss)			4,920				1,322.5
Other Comprehensive Income (Loss), Net of Tax			4,827				1,165.7
Increase (Decrease) in Receivables			24.6				(1.9)
Deferral of Acquisition Costs			(169.9)				(149.1)
Change in Insurance Reserves and Liabilities			37.3				(36.5)
Change in Income Taxes			27.5				40
Amortization of the Cost of Reinsurance			(13.5)				$ (9.3)
Other Noncash Income (Expense)			$ 1
Accounting Standards Update 2018-12 | Revision of Prior Period, Accounting Standards Update, Adjustment | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest										(20.6)
Accounting Standards Update 2018-12 | Revision of Prior Period, Accounting Standards Update, Adjustment | Accumulated Other Comprehensive Income (Loss)
New Accounting Pronouncements or Change in Accounting Principle
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest										(6,684.4)
Accounting Standards Update 2018-12 | Revision of Prior Period, Accounting Standards Update, Adjustment | Operating Segments
New Accounting Pronouncements or Change in Accounting Principle
Removal of Shadow Adjustments, LFPB	[7]									(6,225.6)
Adjustments for Loss Contracts	[8]									34.9
Effect of Change in Discount Rate Assumptions										16,084.6
Other increase (decrease)	[9]									(12.9)
Accounting Standards Update 2018-12 | Revision of Prior Period, Accounting Standards Update, Adjustment | Unum US
New Accounting Pronouncements or Change in Accounting Principle
Removal of Shadow Adjustments, LFPB	[7]									(1,569.7)
Adjustments for Loss Contracts	[8]									0
Effect of Change in Discount Rate Assumptions										2,251.8
Other increase (decrease)	[9]									(5.3)
Removal of Shadow Adjustments, DAC	[10]									12.3
Accounting Standards Update 2018-12 | Revision of Prior Period, Accounting Standards Update, Adjustment | Unum US | Group Disability
New Accounting Pronouncements or Change in Accounting Principle
Removal of Shadow Adjustments, LFPB										(1,025.2)
Effect of Change in Discount Rate Assumptions										911.9
Other increase (decrease)										0
Accounting Standards Update 2018-12 | Revision of Prior Period, Accounting Standards Update, Adjustment | Unum US | Group Life and AD&D
New Accounting Pronouncements or Change in Accounting Principle
Removal of Shadow Adjustments, LFPB										(88.5)
Effect of Change in Discount Rate Assumptions										91.9
Other increase (decrease)										0
Accounting Standards Update 2018-12 | Revision of Prior Period, Accounting Standards Update, Adjustment | Unum US | Individual Disability
New Accounting Pronouncements or Change in Accounting Principle
Removal of Shadow Adjustments, LFPB										(446.1)
Effect of Change in Discount Rate Assumptions										728.5
Other increase (decrease)										0
Accounting Standards Update 2018-12 | Revision of Prior Period, Accounting Standards Update, Adjustment | Unum US | Voluntary Benefits
New Accounting Pronouncements or Change in Accounting Principle
Removal of Shadow Adjustments, LFPB										(9.9)
Effect of Change in Discount Rate Assumptions										519.5
Other increase (decrease)										(5.3)
Accounting Standards Update 2018-12 | Revision of Prior Period, Accounting Standards Update, Adjustment | Unum US | Dental and Vision
New Accounting Pronouncements or Change in Accounting Principle
Removal of Shadow Adjustments, LFPB										0
Effect of Change in Discount Rate Assumptions										0
Other increase (decrease)										0
Accounting Standards Update 2018-12 | Revision of Prior Period, Accounting Standards Update, Adjustment | Unum International
New Accounting Pronouncements or Change in Accounting Principle
Removal of Shadow Adjustments, LFPB	[7]									(545.8)
Adjustments for Loss Contracts	[8]									0
Effect of Change in Discount Rate Assumptions										779.4
Other increase (decrease)	[9]									0
Removal of Shadow Adjustments, DAC										0
Accounting Standards Update 2018-12 | Revision of Prior Period, Accounting Standards Update, Adjustment | Colonial Life
New Accounting Pronouncements or Change in Accounting Principle
Removal of Shadow Adjustments, LFPB	[7]									(44.5)
Adjustments for Loss Contracts	[8]									34.9
Effect of Change in Discount Rate Assumptions										568.6
Other increase (decrease)	[9]									(7.6)
Removal of Shadow Adjustments, DAC										72.8
Accounting Standards Update 2018-12 | Revision of Prior Period, Accounting Standards Update, Adjustment | Closed Block
New Accounting Pronouncements or Change in Accounting Principle
Removal of Shadow Adjustments, LFPB	[7]									(4,065.6)
Adjustments for Loss Contracts	[8]									0
Effect of Change in Discount Rate Assumptions										12,484.8
Other increase (decrease)	[9]									0
Accounting Standards Update 2018-12 | Revision of Prior Period, Accounting Standards Update, Adjustment | Closed Block | Long-term Care
New Accounting Pronouncements or Change in Accounting Principle
Removal of Shadow Adjustments, LFPB										(3,465.4)
Effect of Change in Discount Rate Assumptions										9,922.9
Accounting Standards Update 2018-12 | Revision of Prior Period, Accounting Standards Update, Adjustment | Closed Block | Other Insurance Product Line
New Accounting Pronouncements or Change in Accounting Principle
Removal of Shadow Adjustments, LFPB										(600.2)
Effect of Change in Discount Rate Assumptions										$ 2,561.9
Change in Accounting Method Accounted for as Change in Estimate
New Accounting Pronouncements or Change in Accounting Principle
Premium Income		(13.4)
Commissions		(1)
Net Income		$ (9.8)
Basic Earnings Per Share | $ / shares		$ 0.05
Diluted Earnings Per Share | $ / shares		$ 0.05
[1] 1 The change in other assets is driven by the cost of reinsurance associated with the second phase of our Closed Block individual disability reinsurance transaction which was completed in the first quarter of 2021. In accordance with the provisions of the ASU related to non-contemporaneous reinsurance, we were then required to establish the ceded reserves using an upper-medium grade fixed-income instrument as of the reinsurance transaction date in March 2021 which resulted in higher ceded reserves compared to that which was reported historically. 2 We previously reported policy and contract benefits and reserves for future policy and contract benefits liabilities in our consolidated balance sheet as of December 31, 2022 of $1,839.8 million and $42,330.2 million, respectively, resulting in total policyholder liabilities of $44,170.0 million. These balances were reclassified into new line items, future policy benefits and policyholders' account balances, which would have reported balances of $38,443.2 million and $5,726.8 million, respectively, as of December 31, 2022, resulting in total policyholder liabilities of $44,170.0 million under the historical accounting method. 1 Previously disclosed as Benefits and Change in Reserves for Future Benefits 5 These amounts represent the portion of reinsurance recoverable related to the liability for future policy benefits. These amounts include the adjustments for the removal of shadow adjustments and for the effect of change in discount rate assumptions for the liability for future policy benefits ceded to third party reinsurers. 1 Unum US excludes dental & vision and medical stop-loss product lines and Closed Block excludes our participating fund account, which represents policies issued by one of our subsidiaries prior to its 1986 conversion from a mutual stock life insurance company. The liabilities associated with these products are included within Other products. 1 We previously reported policy and contract benefits and reserves for future policy and contract benefits liabilities in our consolidated balance sheet as of December 31, 2020 of $1,855.4 million and $49,653.0 million, respectively, resulting in total policyholder liabilities of $51,508.4 million. These balances were reclassified into new line items, future policy benefits and policyholders' account balances, which would have reported balances of $45,704.4 million and $5,804.0 million as of December 31, 2020, respectively, resulting in total policyholder liabilities of $51,508.4 million under the historical accounting method. These balances were reclassified to more closely align with the new disclosure requirements of ASU 2018-12. 2 Shadow adjustments represent the adjustments related to unrealized investment gains and losses previously included in the reserves balance prior to the adoption of ASU 2018-12. 3 Adjustment for loss contracts represents the adjustment for those cohorts whose net premium ratio exceeded 100 percent as of the transition date. For those cohorts, the net premiums were set equal to the gross premiums and the difference was recorded as a transition adjustment to the liability for future policy benefits. 4 This amount reflects the effect of the reclassification of certain unearned premium. This amount was reclassified to more closely align with the presentation of liabilities under ASU 2018-12 and had no impact to stockholders' equity. 1 The $12.3 million removal of shadow adjustments is related to the Unum US voluntary benefits product line.

Fair Values of Financial Inst_3

Fair Values of Financial Instruments Private Equity Partnerships (Details) - Private Equity Funds - USD ($) $ in Millions		Dec. 31, 2023	Dec. 31, 2022
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share
Alternative Investments		$ 1,326.2	$ 1,194.3
Alternative Investments, Unfunded Commitments		803.1	776.9
Private Credit
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share
Alternative Investments		283.6	275
Alternative Investments, Unfunded Commitments		136.8	104.3
Private Credit | Not Redeemable
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share
Alternative Investments	[1]	239.1	239.3
Alternative Investments, Unfunded Commitments		128.2	90.9
Private Credit | Quarterly after 2 year lock with 90 days notice [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share
Alternative Investments			35.7
Alternative Investments, Unfunded Commitments			13.4
Private Credit | Quarterly [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share
Alternative Investments		44.5
Alternative Investments, Unfunded Commitments		8.6
Private Equity Limited Partnership
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share
Alternative Investments		571.9	485.3
Alternative Investments, Unfunded Commitments		427.2	416.3
Private Equity Limited Partnership | Not Redeemable
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share
Alternative Investments	[2]	543.9	453.6
Alternative Investments, Unfunded Commitments		410.6	377.2
Private Equity Limited Partnership | Quarterly after 5.5 year lock with 90 days notice [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share
Alternative Investments		28	31.7
Alternative Investments, Unfunded Commitments		16.6	39.1
Real Assets
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share
Alternative Investments		470.7	434
Alternative Investments, Unfunded Commitments		239.1	256.3
Real Assets | Not Redeemable
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share
Alternative Investments	[3]	437.5	373.9
Alternative Investments, Unfunded Commitments		239.1	256.3
Real Assets | Quarterly [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share
Alternative Investments		33.2	60.1
Alternative Investments, Unfunded Commitments		$ 0	$ 0
[1] Private Credit - The limited partnerships described in this category employ various investment strategies, generally providing direct lending or other forms of debt financing including first-lien, second-lien, mezzanine, and subordinated loans. The limited partnerships have credit exposure to corporates, physical assets, and/or financial assets within a variety of industries (including manufacturing, healthcare, energy, business services, technology, materials, and retail) in North America and, to a lesser extent, outside of North America. As of December 31, 2023, the estimated remaining life of the investments that do not allow for redemptions is approximately 74 percent in the next 3 years, 21 percent during the period from 3 to 5 years, 3 percent during the period from 5 to 10 years, and 2 percent during the period from 10 to 15 years. 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, 2023, the estimated remaining life of the investments that do not allow for redemptions is approximately 34 percent in the next 3 years, 31 percent during the period from 3 to 5 years, 26 percent during the period from 5 to 10 years, and 9 percent during the period from 10 to 15 years. 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, 2023, the estimated remaining life of the investments that do not allow for redemptions is approximately 22 percent in the next 3 years, 35 percent during the period from 3 to 5 years, 42 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, 2023	Dec. 31, 2022
Assets
Fixed Maturity Securities	$ 36,833.9	$ 34,840.8
Derivative Asset, Statement of Financial Position [Extensible Enumeration]	Other Assets	Other Assets
Derivative Assets	$ 99.9	$ 89.1
Equity Securities	31.9	25.8
Other Long-term Investments	1,579.4	1,440.1
Assets, Fair Value Disclosure	$ 38,291.9	$ 36,150
Derivative Liability, Statement of Financial Position [Extensible Enumeration]	Other Liabilities	Other Liabilities
Derivative Liabilities	$ 117.7	$ 87.9
Liabilities
Liabilities, Fair Value Disclosure	117.7	87.9
Forwards
Assets
Derivative Liabilities	78	48.5
Foreign Exchange Contracts
Assets
Derivative Liabilities	38.2	25.5
Embedded Derivative in Modified Coinsurance Arrangement
Assets
Derivative Liabilities	1.5	13.9
Fair Value, Measurements, Recurring
Assets
Other Long-term Investments	1,458	1,309.2
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Assets
Fixed Maturity Securities	4,286.5	4,519.1
Equity Securities	0	0
Assets, Fair Value Disclosure	4,286.5	4,519.1
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Assets
Fixed Maturity Securities	32,391.1	30,140.8
Derivative Assets	99.9	89.1
Equity Securities	10.3	9.6
Other Long-term Investments	110.2	98.7
Assets, Fair Value Disclosure	32,501.3	30,239.5
Derivative Liabilities	116.2	74
Liabilities
Liabilities, Fair Value Disclosure	116.2	74
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | Forwards
Assets
Derivative Liabilities	78	48.5
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | Foreign Exchange Contracts
Assets
Derivative Liabilities	38.2	25.5
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Assets
Fixed Maturity Securities	156.3	180.9
Equity Securities	21.6	16.2
Other Long-term Investments	21.6	16.2
Assets, Fair Value Disclosure	177.9	197.1
Derivative Liabilities	1.5	13.9
Liabilities
Liabilities, Fair Value Disclosure	1.5	13.9
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3 | Embedded Derivative in Modified Coinsurance Arrangement
Assets
Derivative Liabilities	1.5	13.9
Fair Value, Measurements, Recurring | Fair Value Measured at Net Asset Value Per Share
Assets
Fixed Maturity Securities	0	0
Equity Securities	0	0
Other Long-term Investments	1,326.2	1,194.3
Assets, Fair Value Disclosure	1,326.2	1,194.3
United States Government and Government Agencies and Authorities
Assets
Fixed Maturity Securities	624.8	498.2
United States Government and Government Agencies and Authorities | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Assets
Fixed Maturity Securities	0	81.7
United States Government and Government Agencies and Authorities | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Assets
Fixed Maturity Securities	624.8	416.5
United States Government and Government Agencies and Authorities | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Assets
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
Assets
Fixed Maturity Securities	0	0
States, Municipalities, and Political Subdivisions
Assets
Fixed Maturity Securities	3,678.4	3,457.2
States, Municipalities, and Political Subdivisions | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Assets
Fixed Maturity Securities	0	8.7
States, Municipalities, and Political Subdivisions | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Assets
Fixed Maturity Securities	3,678.4	3,448.3
States, Municipalities, and Political Subdivisions | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Assets
Fixed Maturity Securities	0	0.2
States, Municipalities, and Political Subdivisions | Fair Value, Measurements, Recurring | Fair Value Measured at Net Asset Value Per Share
Assets
Fixed Maturity Securities	0	0
Foreign Governments
Assets
Fixed Maturity Securities	890.7	827.1
Foreign Governments | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Assets
Fixed Maturity Securities	0	0
Foreign Governments | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Assets
Fixed Maturity Securities	890.7	827.1
Foreign Governments | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Assets
Fixed Maturity Securities	0	0
Foreign Governments | Fair Value, Measurements, Recurring | Fair Value Measured at Net Asset Value Per Share
Assets
Fixed Maturity Securities	0	0
Public Utilities
Assets
Fixed Maturity Securities	5,321.6	4,956.9
Public Utilities | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Assets
Fixed Maturity Securities	301.3	160.1
Public Utilities | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Assets
Fixed Maturity Securities	5,020.3	4,796.8
Public Utilities | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Assets
Fixed Maturity Securities	0	0
Public Utilities | Fair Value, Measurements, Recurring | Fair Value Measured at Net Asset Value Per Share
Assets
Fixed Maturity Securities	0	0
Mortgage/Asset-backed Securities
Assets
Fixed Maturity Securities	644.1	573.3
Mortgage/Asset-backed Securities | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Assets
Fixed Maturity Securities	0	0
Mortgage/Asset-backed Securities | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Assets
Fixed Maturity Securities	611.2	551.3
Mortgage/Asset-backed Securities | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Assets
Fixed Maturity Securities	32.9	22
Mortgage/Asset-backed Securities | Fair Value, Measurements, Recurring | Fair Value Measured at Net Asset Value Per Share
Assets
Fixed Maturity Securities	0	0
All Other Corporate Bonds
Assets
Fixed Maturity Securities	25,670.7	24,524.6
All Other Corporate Bonds | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Assets
Fixed Maturity Securities	3,985.2	4,268.6
All Other Corporate Bonds | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Assets
Fixed Maturity Securities	21,562.1	20,097.3
All Other Corporate Bonds | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Assets
Fixed Maturity Securities	123.4	158.7
All Other Corporate Bonds | Fair Value, Measurements, Recurring | Fair Value Measured at Net Asset Value Per Share
Assets
Fixed Maturity Securities	0	0
Redeemable Preferred Stocks
Assets
Fixed Maturity Securities	3.6	3.5
Redeemable Preferred Stocks | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Assets
Fixed Maturity Securities	0	0
Redeemable Preferred Stocks | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Assets
Fixed Maturity Securities	3.6	3.5
Redeemable Preferred Stocks | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Assets
Fixed Maturity Securities	0	0
Redeemable Preferred Stocks | Fair Value, Measurements, Recurring | Fair Value Measured at Net Asset Value Per Share
Assets
Fixed Maturity Securities	0	0
Forwards
Assets
Derivative Assets	47.5	5.6
Forwards | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Assets
Derivative Assets	47.5	5.6
Foreign Exchange Contracts
Assets
Derivative Assets	52.4	83.5
Foreign Exchange Contracts | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Assets
Derivative Assets	52.4	83.5
Private Equity Funds
Assets
Alternative Investments	1,326.2	1,194.3
Private Equity Funds | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Assets
Alternative Investments	0	0
Private Equity Funds | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Assets
Alternative Investments	0	0
Private Equity Funds | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Assets
Alternative Investments	0	0
Private Equity Funds | Fair Value, Measurements, Recurring | Fair Value Measured at Net Asset Value Per Share
Assets
Alternative Investments	$ 1,326.2	$ 1,194.3

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, 2023	Dec. 31, 2022
Embedded Derivative in Modified Coinsurance Arrangement
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Derivatives Measured with Unobservable Inputs, Beginning Balance	$ (13.9)	$ (30.1)
Derivative Liability Gain (Loss) Included in Earnings	12.4	16.2
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	(1.5)	(13.9)
Fair Value, Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	0	0
Fair Value, Net Derivative Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss)	12.4	16.2
States, Municipalities, and Political Subdivisions
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Assets Measured with Unobservable Inputs, Beginning Balance	0.2	13.4
Investment Gain (Loss) included in Earnings	0	0
Investment Gain (Loss) included in OCI	0	(0.1)
Investment Purchases	0	0
Investment Sales	0	0
Investment Level 3 Transfers Into	0	0.3
Investment Level 3 Transfers Out of	0.2	13.4
Assets Measured with Unobservable Inputs, Ending Balance	0	0.2
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	0	0.1
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	0	0
Foreign Governments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Assets Measured with Unobservable Inputs, Beginning Balance	0	20.8
Investment Gain (Loss) included in Earnings		0
Investment Gain (Loss) included in OCI		(0.8)
Investment Purchases		0
Investment Sales		(20)
Investment Level 3 Transfers Into		0
Investment Level 3 Transfers Out of		0
Assets Measured with Unobservable Inputs, Ending Balance		0
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), OCI		0.8
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	0	44.5
Investment Gain (Loss) included in Earnings	0.1	0
Investment Gain (Loss) included in OCI	(0.1)	(2.8)
Investment Purchases	0	0
Investment Sales	(50.5)	(12.8)
Investment Level 3 Transfers Into	50.5	15.6
Investment Level 3 Transfers Out of	0	44.5
Assets Measured with Unobservable Inputs, Ending Balance	0	0
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	0	2.8
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	0	0
Mortgage/Asset-backed Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Assets Measured with Unobservable Inputs, Beginning Balance	22	187.2
Investment Gain (Loss) included in Earnings	0	0
Investment Gain (Loss) included in OCI	(0.2)	(0.3)
Investment Purchases	20	20.7
Investment Sales	(0.5)	(10.6)
Investment Level 3 Transfers Into	0.4	0
Investment Level 3 Transfers Out of	8.8	175
Assets Measured with Unobservable Inputs, Ending Balance	32.9	22
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	0.2	0.3
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	0	0
All Other Corporate Bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Assets Measured with Unobservable Inputs, Beginning Balance	158.7	861.5
Investment Gain (Loss) included in Earnings	(5)	0
Investment Gain (Loss) included in OCI	(15.8)	(32)
Investment Purchases	1.5	25.3
Investment Sales	(334.1)	(102.3)
Investment Level 3 Transfers Into	385	161.9
Investment Level 3 Transfers Out of	66.9	755.7
Assets Measured with Unobservable Inputs, Ending Balance	123.4	158.7
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	15.8	32
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	0	0
Fixed Maturity Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Assets Measured with Unobservable Inputs, Beginning Balance	180.9	1,127.4
Investment Gain (Loss) included in Earnings	(4.9)	0
Investment Gain (Loss) included in OCI	(16.1)	(36)
Investment Purchases	21.5	46
Investment Sales	(385.1)	(145.7)
Investment Level 3 Transfers Into	435.9	177.8
Investment Level 3 Transfers Out of	75.9	988.6
Assets Measured with Unobservable Inputs, Ending Balance	156.3	180.9
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	16	36
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	0	0
Perpetual Preferred Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Assets Measured with Unobservable Inputs, Beginning Balance	16.2	5.8
Investment Gain (Loss) included in Earnings	0.6	3
Investment Gain (Loss) included in OCI	0	0
Investment Purchases	4.8	7.1
Investment Sales	0	0
Investment Level 3 Transfers Into	0	0.3
Investment Level 3 Transfers Out of	0	0
Assets Measured with Unobservable Inputs, Ending Balance	21.6	16.2
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	0	0
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	$ 0.6	$ 3

Quantitative Information Regard

Quantitative Information Regarding Significant Unobservable Inputs (Details) $ in Millions		Dec. 31, 2023 USD ($) Rate	Dec. 31, 2022 USD ($) Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity Securities | $		$ 31.9	$ 25.8
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]	$ (1.5)	$ (13.9)
Fair Value, Inputs, Level 3 | Discounted Cash Flow | Embedded Derivative in Modified Coinsurance Arrangement | Weighted Average | Input Measurement, Spread of Swap Curve
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded Derivative Liability, Measurement Input | Rate		0.002	0.006
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],[3]	$ 15.9	$ 15.3
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 | Rate		0.0500	0.0541
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 | Rate		0.0500	0.0541
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 | Rate		0.0500	0.0541
Fair Value, Inputs, Level 3 | Perpetual Preferred Securities | Market Approach
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity Securities | $	[3]	$ 21.6	$ 16.2
[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 Represents basis point adjustments for credit-specific factors Represents a decision to price based on par value, cost, owner's equity, or the price of the most recent capital funding round when limited data is available

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, 2023	Dec. 31, 2022
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Mortgage Loans	$ 2,318.2	$ 2,435.4
Policy Loans	3,620.2	3,601.2
Long-term Debt	3,430.4	3,427.8
Unfunded Commitments	0.2
Liabilities, Fair Value Disclosure	117.7	87.9
Fair Value, Nonrecurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Mortgage Loans, Fair Value Disclosure	2,070.7	2,159.5
Mortgage Loans	2,318.2	2,435.4
Policy Loans, Fair Value Disclosure	3,696.3	3,677
Policy Loans	3,620.2	3,601.2
Miscellaneous Long-Term Investments, Fair Value Disclosure	16	18.4
Miscellaneous Long-Term Investments	16	18.4
Financial Instruments, Financial Assets Fair Value Disclosure	5,783	5,854.9
Total Financial Instrument Assets Not Carried at Fair Value	5,954.4	6,055
Long-term Debt, Fair Value Disclosure	3,227.9	3,072
Long-term Debt	3,430.4	3,427.8
Unfunded Commitments	0.2	0.7
Federal Home Loan Bank Funding Agreements, Fair Value Disclosure	64.5	99.1
Federal Home Loan Bank Funding Agreements	64.5	99.1
Liabilities, Fair Value Disclosure	3,292.6	3,171.8
Total Financial Instrument Liabilities Not Carried at Fair Value	3,495.1	3,527.6
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	2,629.1	2,288.9
Unfunded Commitments	0	0
Federal Home Loan Bank Funding Agreements, Fair Value Disclosure	0	0
Liabilities, Fair Value Disclosure	2,629.1	2,288.9
Fair Value, Inputs, Level 2 | Fair Value, Nonrecurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Mortgage Loans, Fair Value Disclosure	2,070.7	2,159.5
Policy Loans, Fair Value Disclosure	0	0
Miscellaneous Long-Term Investments, Fair Value Disclosure	15.7	17.1
Financial Instruments, Financial Assets Fair Value Disclosure	2,086.4	2,176.6
Long-term Debt, Fair Value Disclosure	598.8	783.1
Unfunded Commitments	0.2	0.7
Federal Home Loan Bank Funding Agreements, Fair Value Disclosure	64.5	99.1
Liabilities, Fair Value Disclosure	663.5	882.9
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	3,696.3	3,677
Miscellaneous Long-Term Investments, Fair Value Disclosure	0.3	1.3
Financial Instruments, Financial Assets Fair Value Disclosure	3,696.6	3,678.3
Long-term Debt, Fair Value Disclosure	0	0
Unfunded Commitments	0	0
Federal Home Loan Bank Funding Agreements, Fair Value Disclosure	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, 2023	Dec. 31, 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Ceded Policy Loans	$ 3,322.5	$ 3,312.5
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	11.60%
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	72.90%
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	14.70%
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	88.40%
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	0.80%

Amortized Cost and Fair Values

Amortized Cost and Fair Values of Securities by Security Type (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale
Amortized Cost of Fixed Maturity Securities	$ 38,410.6	$ 37,825.2
Debt Securities, Available-for-sale, Allowance for Credit Loss	2.2	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1,189.4
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	2,763.9
Debt Securities, Available-for-sale, Total	36,833.9	34,840.8
United States Government and Government Agencies and Authorities
Debt Securities, Available-for-sale
Amortized Cost of Fixed Maturity Securities	618.6	503.8
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	25.3	20.3
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	19.1	25.9
Debt Securities, Available-for-sale, Total	624.8	498.2
States, Municipalities, and Political Subdivisions
Debt Securities, Available-for-sale
Amortized Cost of Fixed Maturity Securities	4,041.3	4,006
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	135.3	87.1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	498.2	635.9
Debt Securities, Available-for-sale, Total	3,678.4	3,457.2
Foreign Governments
Debt Securities, Available-for-sale
Amortized Cost of Fixed Maturity Securities	982.1	908.1
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	29.8	34.9
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	121.2	115.9
Debt Securities, Available-for-sale, Total	890.7	827.1
Public Utilities
Debt Securities, Available-for-sale
Amortized Cost of Fixed Maturity Securities	5,398.2	5,170.9
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0	$ 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	217.1	141
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	293.7	355
Debt Securities, Available-for-sale, Total	5,321.6	4,956.9
Mortgage/Asset-backed Securities
Debt Securities, Available-for-sale
Amortized Cost of Fixed Maturity Securities	658	592.1
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	10.1	8.2
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	24	27
Debt Securities, Available-for-sale, Total	644.1	573.3
All Other Corporate Bonds
Debt Securities, Available-for-sale
Amortized Cost of Fixed Maturity Securities	26,708.4	26,640.3
Debt Securities, Available-for-sale, Allowance for Credit Loss	2.2	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	771.8	452.1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1,807.3	2,567.8
Debt Securities, Available-for-sale, Total	25,670.7	24,524.6
Redeemable Preferred Stocks
Debt Securities, Available-for-sale
Amortized Cost of Fixed Maturity Securities	4	4
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0.4	0.5
Debt Securities, Available-for-sale, Total	3.6	3.5
Fixed Maturity Securities
Debt Securities, Available-for-sale
Amortized Cost of Fixed Maturity Securities	38,410.6	37,825.2
Debt Securities, Available-for-sale, Allowance for Credit Loss	2.2	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1,189.4	743.6
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	2,763.9	3,728
Debt Securities, Available-for-sale, Total	$ 36,833.9	$ 34,840.8

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, 2023	Dec. 31, 2022
United States Government and Government Agencies and Authorities
Debt Securities, Available-for-sale, Unrealized Loss Position
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 118.8	$ 246.6
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0.7	22.6
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	197.3	12.2
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	18.4	3.3
States, Municipalities, and Political Subdivisions
Debt Securities, Available-for-sale, Unrealized Loss Position
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	128	1,920.1
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	4	476.1
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	2,035.1	346.6
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	494.2	159.8
Foreign Governments
Debt Securities, Available-for-sale, Unrealized Loss Position
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	149.9	160.1
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	3.3	47.9
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	312.9	176.9
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	117.9	68
Public Utilities
Debt Securities, Available-for-sale, Unrealized Loss Position
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	373.7	2,242.2
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	10.4	252
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	1,720.6	255.2
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	283.3	103
Mortgage/Asset-backed Securities
Debt Securities, Available-for-sale, Unrealized Loss Position
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	60.3	386.6
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	2.5	27
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	316.7	0.1
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	21.5	0
All Other Corporate Bonds
Debt Securities, Available-for-sale, Unrealized Loss Position
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	1,483.8	15,865.6
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	26.8	1,799.7
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	14,215.2	2,194.1
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	1,780.5	768.1
Redeemable Preferred Stocks
Debt Securities, Available-for-sale, Unrealized Loss Position
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	0	3.5
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	0.5
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	3.6	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0.4	0
Fixed Maturity Securities
Debt Securities, Available-for-sale, Unrealized Loss Position
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	2,314.5	20,824.7
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	47.7	2,625.8
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	18,801.4	2,985.1
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 2,716.2	$ 1,102.2

Investments Distribution of the

Investments Distribution of the Maturity Dates for Fixed Maturity Securities (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
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	$ 935	$ 1,133.5
Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year One Through Five, Net	7,594.4	7,090.8
Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year 5 Through 10, Net	9,430.3	10,096.7
Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year 10, Net	19,790.7	18,912.1
Available for sale Securities Debt Maturities Amortized Cost Gross Subtotal, Net	37,750.4	37,233.1
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Amortized Cost, Net	658	592.1
Debt Securities, Available-for-sale, Amortized Cost, Net of Allowance for Credit Losses	38,408.4	37,825.2
Available for Sale Securities Unrealized Gain Position Gross Gain [Abstract]
Available For Sale Securities Debt Maturities Within One Year Unrealized Gain Position Gross Gain	0.9	2.9
Available For Sale Securities Debt Maturities After One Through Five Years Unrealized Gain Position Gross Gain	128.2	86.7
Available For Sale Securities Debt Maturities After Five Through Ten Years Unrealized Gain Position Gross Gain	372.1	294.8
Available For Sale Securities Debt Maturities After Ten Years Unrealized Gain Position Gross Gain	678.1	351
Available For Sale Securities Debt Maturities Unrealized Gain Position Gross Gain Gross Subtotal	1,179.3	735.4
Available For Sale Securities Debt Maturities Without Single Maturity Date Unrealized Gain Position Gross Gain	10.1	8.2
Available for sale Securities, Debt Maturities Unrealized Gain Position Gross Gain	1,189.4	743.6
Available for Sale Securities Unrealized Loss Position Gross Loss [Abstract]
Available For Sale Securities Debt Maturities Within One Year Unrealized Loss Position Gross Loss	7.5	5.7
Available For Sale Securities Debt Maturities After One Through Five Years Unrealized Loss Position Gross Loss	179	238.4
Available For Sale Securities Debt Maturities After Five Through Ten Years Unrealized Loss Position Gross Loss	610.8	863.8
Available For Sale Securities Debt Maturities After Ten Years Unrealized Loss Position Gross Loss	1,942.6	2,593.1
Available For Sale Securities Debt Maturities Unrealized Gain Position Gross Loss Gross Subtotal	2,739.9	3,701
Available For Sale Securities Debt Maturities Without Single Maturity Date Unrealized Loss Position Gross Loss	24	27
Available For Sale Securities Unrealized Loss Position Gross Loss Subtotal	2,763.9	3,728
Fair Value Maturity Distribution [Abstract]
Debt Securities, Available-for-sale, Total	36,833.9	34,840.8
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	140.8	339.1
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Fair Value	2,685.7	1,953.2
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Fair Value	4,100	3,538.9
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after 10 Years, Fair Value	8,524.4	5,013.2
Available for sale Securities Debt Maturities Fair Value Gross Subtotal	15,450.9	10,844.4
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Fair Value	267.1	186.6
Debt Securities, Available-for-sale, Total	15,718	11,031
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	787.6	791.6
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Fair Value	4,857.9	4,985.9
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Fair Value	5,091.6	5,988.8
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after 10 Years, Fair Value	10,001.8	11,656.8
Available for sale Securities Debt Maturities Fair Value Gross Subtotal	20,738.9	23,423.1
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Fair Value	377	386.7
Debt Securities, Available-for-sale, Total	$ 21,115.9	$ 23,809.8

Investments Distribution by Ext

Investments Distribution by External Credit Rating for Fixed Maturity Securities (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale
Fixed Maturity Securities	$ 36,833.9	$ 34,840.8
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1,189.4
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	$ 2,763.9
Fixed maturity securities in unrealized loss position percent of total	100%
External Credit Rating, Investment Grade
Debt Securities, Available-for-sale
Fixed Maturity Securities	$ 35,344.9
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1,169.1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	$ 2,660.3
Fixed maturity securities in unrealized loss position percent of total	96.30%
External Credit Rating, Below-Investment-Grade
Debt Securities, Available-for-sale
Fixed Maturity Securities	$ 1,489
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	20.3
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	$ 103.6
Fixed maturity securities in unrealized loss position percent of total	3.70%

Debt Securities, Available-for-

Debt Securities, Available-for-sale, Allowance for Credit Losses Rollforward (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale, Allowance for Credit Loss
Debt Securities, Available-for-Sale, Allowance for Credit Loss, Beginning Balance	$ 0
Debt Securities, Available-for-Sale, Allowance for Credit Loss, Ending Balance	2.2	$ 0
All Other Corporate Bonds
Debt Securities, Available-for-sale, Allowance for Credit Loss
Debt Securities, Available-for-Sale, Allowance for Credit Loss, Beginning Balance	0
Debt Securities, Available-for-sale, Allowance for Credit Loss, Not Previously Recorded	2.2
Debt Securities, Available-for-sale, Allowance for Credit Loss, Securities Sold	0
Debt Securities, Available-for-Sale, Allowance for Credit Loss, Ending Balance	2.2	0
Public Utilities
Debt Securities, Available-for-sale, Allowance for Credit Loss
Debt Securities, Available-for-Sale, Allowance for Credit Loss, Beginning Balance	0	0
Debt Securities, Available-for-sale, Allowance for Credit Loss, Not Previously Recorded		4.6
Debt Securities, Available-for-sale, Allowance for Credit Loss, Securities Sold		(4.6)
Debt Securities, Available-for-Sale, Allowance for Credit Loss, Ending Balance	$ 0	$ 0

Investments Low Income Housing

Investments Low Income Housing Tax Credits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Low Income Housing Tax Credits [Abstract]
Affordable Housing Tax Credits	$ 1.1	$ 8	$ 21.6
Amortization of Affordable Housing Tax Credit Investments	(0.5)	(5.9)	(15)
Tax Benefits from Low Income Housing Investments	$ 0.6	$ 2.1	$ 6.6

Mortgage Loans by Property Type

Mortgage Loans by Property Type and Geographic Region (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Mortgage Loans on Real Estate
Mortgage Loans	$ 2,318.2	$ 2,435.4
Percent of Total	100%	100%
New England
Mortgage Loans on Real Estate
Mortgage Loans	$ 55.1	$ 52.4
Percent of Total	2.40%	2.20%
Mid-Atlantic
Mortgage Loans on Real Estate
Mortgage Loans	$ 155.1	$ 192.4
Percent of Total	6.70%	7.90%
East North Central
Mortgage Loans on Real Estate
Mortgage Loans	$ 314.4	$ 313
Percent of Total	13.60%	12.90%
West North Central
Mortgage Loans on Real Estate
Mortgage Loans	$ 163.5	$ 181.4
Percent of Total	7%	7.40%
South Atlantic
Mortgage Loans on Real Estate
Mortgage Loans	$ 553	$ 539.3
Percent of Total	23.80%	22.10%
East South Central
Mortgage Loans on Real Estate
Mortgage Loans	$ 110.7	$ 101.8
Percent of Total	4.80%	4.20%
West South Central
Mortgage Loans on Real Estate
Mortgage Loans	$ 200.9	$ 212.6
Percent of Total	8.70%	8.70%
Mountain
Mortgage Loans on Real Estate
Mortgage Loans	$ 282.7	$ 298.7
Percent of Total	12.20%	12.30%
Pacific
Mortgage Loans on Real Estate
Mortgage Loans	$ 482.8	$ 543.8
Percent of Total	20.80%	22.30%
Apartment
Mortgage Loans on Real Estate
Mortgage Loans	$ 685.8	$ 688.6
Percent of Total	29.60%	28.30%
Industrial
Mortgage Loans on Real Estate
Mortgage Loans	$ 706	$ 745.3
Percent of Total	30.50%	30.60%
Office
Mortgage Loans on Real Estate
Mortgage Loans	$ 379.9	$ 423
Percent of Total	16.40%	17.40%
Retail
Mortgage Loans on Real Estate
Mortgage Loans	$ 503.9	$ 534.5
Percent of Total	21.70%	21.90%
Other Property
Mortgage Loans on Real Estate
Mortgage Loans	$ 42.6	$ 44
Percent of Total	1.80%	1.80%

Schedule of Participating Mortg

Schedule of Participating Mortgage Loans by Internal Credit Rating and Loan to Value (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Mortgage Loans on Real Estate
Mortgage Loans	$ 2,318.2	$ 2,435.4
Percent of Total	100%	100%
Loan to Value Ratio Below or Equal to 65 Percent
Mortgage Loans on Real Estate
Mortgage Loans	$ 1,409.9	$ 1,389.6
Percent of Total	60.80%	57%
Loan To Value Ratio Above 65 To 75 Percent
Mortgage Loans on Real Estate
Mortgage Loans	$ 707	$ 937.2
Percent of Total	30.50%	38.50%
Loan To Value Ratio Above 75 To 85 Percent
Mortgage Loans on Real Estate
Mortgage Loans	$ 136.5	$ 75
Percent of Total	5.90%	3.10%
Loan To Value Ratio Above 85 Percent
Mortgage Loans on Real Estate
Mortgage Loans	$ 64.8	$ 33.6
Percent of Total	2.80%	1.40%
AA Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans	$ 85.2	$ 92.3
Percent of Total	3.70%	3.80%
A Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans	$ 942.5	$ 843.9
Percent of Total	40.60%	34.60%
BBB Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans	$ 1,249.5	$ 1,458
Percent of Total	53.90%	59.90%
BB Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans	$ 41	$ 41.2
Percent of Total	1.80%	1.70%

Mortgage Loans Sorted by Applic

Mortgage Loans Sorted by Applicable Credit Quality Indicators (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Financing Receivable, Credit Quality Indicator
Financing Receivable, Allowance for Credit Loss	$ (10.2)
Mortgage Loans	2,318.2	$ 2,435.4
Loan to Value Ratio Below or Equal to 65 Percent
Financing Receivable, Credit Quality Indicator
Mortgage Loans	1,409.9	1,389.6
Loan To Value Ratio Above 65 To 75 Percent
Financing Receivable, Credit Quality Indicator
Mortgage Loans	707	937.2
Loan To Value Ratio Above 75 To 85 Percent
Financing Receivable, Credit Quality Indicator
Mortgage Loans	136.5	75
Loan To Value Ratio Above 85 Percent
Financing Receivable, Credit Quality Indicator
Mortgage Loans	64.8	33.6
Originated Five or More Years before Last Fiscal Year
Financing Receivable, Credit Quality Indicator
Mortgage Loans	1,317.6	1,104.2
Originated Four Years before Last Fiscal Year
Financing Receivable, Credit Quality Indicator
Mortgage Loans	334.8	374.7
Originated Three Years before Last Fiscal Year
Financing Receivable, Credit Quality Indicator
Mortgage Loans	164.9	343.5
Originated Two Years before Last Fiscal Year
Financing Receivable, Credit Quality Indicator
Mortgage Loans	347.1	169.3
Originated in Fiscal Year before Latest Fiscal Year
Financing Receivable, Credit Quality Indicator
Mortgage Loans	87	355.6
Originated in Current Fiscal Year
Financing Receivable, Credit Quality Indicator
Mortgage Loans	66.8	88.1
AA Credit Rating
Financing Receivable, Credit Quality Indicator
Mortgage Loans	85.2	92.3
A Credit Rating
Financing Receivable, Credit Quality Indicator
Mortgage Loans	942.5	843.9
BBB Credit Rating
Financing Receivable, Credit Quality Indicator
Mortgage Loans	1,249.5	1,458
BB Credit Rating
Financing Receivable, Credit Quality Indicator
Mortgage Loans	41	41.2
Commercial Real Estate
Financing Receivable, Credit Quality Indicator
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,323.9	1,108.5
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	336.1	376.5
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	165.5	344.8
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	348.1	169.9
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	87.6	356.4
Financing Receivable, Year One, Originated, Current Fiscal Year	67.2	88.6
Financing Receivable, before Allowance for Credit Loss	2,328.4	2,444.7
Financing Receivable, Allowance for Credit Loss	(10.2)	(9.3)	$ (8.3)
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	908.3	782.6
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	197.7	189
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	116.4	193.9
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	145.2	81.3
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	16.2	128.9
Financing Receivable, Year One, Originated, Current Fiscal Year	30	16.9
Financing Receivable, before Allowance for Credit Loss	1,413.8	1,392.6
Financing Receivable, Allowance for Credit Loss	(3.8)	(3)	(2.6)
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	252.1	230.2
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	138.4	181.6
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	40.8	150.9
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	171	80.1
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	71.4	227.5
Financing Receivable, Year One, Originated, Current Fiscal Year	37.2	71.7
Financing Receivable, before Allowance for Credit Loss	710.9	942
Financing Receivable, Allowance for Credit Loss	(3.8)	(4.7)	(4.7)
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	97.3	67.5
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	8.3	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	31.9	8.5
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	0
Financing Receivable, Year One, Originated, Current Fiscal Year	0	0
Financing Receivable, before Allowance for Credit Loss	137.5	76
Financing Receivable, Allowance for Credit Loss	(1.2)	(1.1)	(0.7)
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	66.2	28.2
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0	5.9
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0	0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	0
Financing Receivable, Year One, Originated, Current Fiscal Year	0	0
Financing Receivable, before Allowance for Credit Loss	66.2	34.1
Financing Receivable, Allowance for Credit Loss	(1.4)	(0.5)	$ (0.3)
Commercial Real Estate | Originated Five or More Years before Last Fiscal Year
Financing Receivable, Credit Quality Indicator
Financing Receivable, Allowance for Credit Loss	(6.3)	(4.3)
Commercial Real Estate | Originated Four Years before Last Fiscal Year
Financing Receivable, Credit Quality Indicator
Financing Receivable, Allowance for Credit Loss	(1.3)	(1.8)
Commercial Real Estate | Originated Three Years before Last Fiscal Year
Financing Receivable, Credit Quality Indicator
Financing Receivable, Allowance for Credit Loss	(0.6)	(1.3)
Commercial Real Estate | Originated Two Years before Last Fiscal Year
Financing Receivable, Credit Quality Indicator
Financing Receivable, Allowance for Credit Loss	(1)	(0.6)
Commercial Real Estate | Originated in Fiscal Year before Latest Fiscal Year
Financing Receivable, Credit Quality Indicator
Financing Receivable, Allowance for Credit Loss	(0.6)	(0.8)
Commercial Real Estate | Originated in Current Fiscal Year
Financing Receivable, Credit Quality Indicator
Financing Receivable, Allowance for Credit Loss	(0.4)	(0.5)
Commercial Real Estate | AA Credit Rating
Financing Receivable, Credit Quality Indicator
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	74.3	53.8
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	11	27.5
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0	11.1
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0	0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	0
Financing Receivable, Year One, Originated, Current Fiscal Year	0	0
Financing Receivable, before Allowance for Credit Loss	85.3	92.4
Commercial Real Estate | A Credit Rating
Financing Receivable, Credit Quality Indicator
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	589	485
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	100.3	123.3
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	94.1	96.8
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	100.1	35.9
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	23.2	80.6
Financing Receivable, Year One, Originated, Current Fiscal Year	38	24
Financing Receivable, before Allowance for Credit Loss	944.7	845.6
Commercial Real Estate | BBB Credit Rating
Financing Receivable, Credit Quality Indicator
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	618.4	534
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	224.8	219.8
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	71.4	236.9
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	248	134
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	64.4	275.8
Financing Receivable, Year One, Originated, Current Fiscal Year	29.2	64.6
Financing Receivable, before Allowance for Credit Loss	1,256.2	1,465.1
Commercial Real Estate | BB Credit Rating
Financing Receivable, Credit Quality Indicator
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	42.2	35.7
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0	5.9
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0	0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	0
Financing Receivable, Year One, Originated, Current Fiscal Year	0	0
Financing Receivable, before Allowance for Credit Loss	$ 42.2	$ 41.6

Mortgage Loans, Allowance for C

Mortgage Loans, Allowance for Credit Losses Rollforward (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Writeoff	$ 0	$ 0
Financing Receivable, Allowance for Credit Loss, Ending Balance	10.2
Commercial Real Estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance	9.3	8.3
Financing Receivable, Credit Loss, Expense (Reversal)	0.9	1
Financing Receivable, Allowance for Credit Loss, Writeoff	0	0
Financing Receivable, Allowance for Credit Loss, Recovery	0	0
Financing Receivable, Allowance for Credit Loss, Ending Balance	10.2	9.3
Commercial Real Estate | Loan to Value Ratio Below or Equal to 65 Percent
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance	3	2.6
Financing Receivable, Credit Loss, Expense (Reversal)	0.8	0.4
Financing Receivable, Allowance for Credit Loss, Writeoff	0	0
Financing Receivable, Allowance for Credit Loss, Recovery	0	0
Financing Receivable, Allowance for Credit Loss, Ending Balance	3.8	3
Commercial Real Estate | Loan To Value Ratio Above 65 To 75 Percent
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance	4.7	4.7
Financing Receivable, Credit Loss, Expense (Reversal)	(0.9)	0
Financing Receivable, Allowance for Credit Loss, Writeoff	0	0
Financing Receivable, Allowance for Credit Loss, Recovery	0	0
Financing Receivable, Allowance for Credit Loss, Ending Balance	3.8	4.7
Commercial Real Estate | Loan To Value Ratio Above 75 To 85 Percent
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance	1.1	0.7
Financing Receivable, Credit Loss, Expense (Reversal)	0.1	0.4
Financing Receivable, Allowance for Credit Loss, Writeoff	0	0
Financing Receivable, Allowance for Credit Loss, Recovery	0	0
Financing Receivable, Allowance for Credit Loss, Ending Balance	1.2	1.1
Commercial Real Estate | Loan To Value Ratio Above 85 Percent
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance	0.5	0.3
Financing Receivable, Credit Loss, Expense (Reversal)	0.9	0.2
Financing Receivable, Allowance for Credit Loss, Writeoff	0	0
Financing Receivable, Allowance for Credit Loss, Recovery	0	0
Financing Receivable, Allowance for Credit Loss, Ending Balance	$ 1.4	$ 0.5

Investments Remaining Contractu

Investments Remaining Contractual Maturity of Security Lending Agreements (Details) - Overnight and Continuous - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
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	$ 63.1	$ 88.5
Securities Loaned and Securities Sold under Agreement to Repurchase, Gross Including Not Subject to Master Netting Arrangement	63.1	88.5
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	0.3
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	1.8	6.3
All Other Corporate Bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred	$ 61.3	$ 81.9

Investments Federal Home Loan B

Investments Federal Home Loan Bank Carrying Amount, Collateral Posted and Advances Received (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Federal Home Loan Bank Carrying Value of Common Stock, Collateral Posted and Advances
Federal Home Loan Bank Common Stock	$ 15.7	$ 17.1
Federal Home Loan Bank, Advances	64.5	99.1
Federal Home Loan Bank, Collateral Posted to FHLB	1,575.8	1,329
Fixed Maturity Securities
Federal Home Loan Bank Carrying Value of Common Stock, Collateral Posted and Advances
Federal Home Loan Bank, Collateral Posted to FHLB	589	527.1
Commercial Mortgage Loans
Federal Home Loan Bank Carrying Value of Common Stock, Collateral Posted and Advances
Federal Home Loan Bank, Collateral Posted to FHLB	$ 986.8	$ 801.9

Investments Schedule of Financi

Investments Schedule of Financial Instrument and Derivative Offsetting (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Offsetting Derivative Assets
Net Derivative Assets Reported in Balance Sheet	$ 99.9	$ 89.1
Offsetting Securities Loaned
Gross Securities Loaned	(72)	(152.4)
Assets Offsetting Securities Loaned in Balance Sheet	0	0
Securities Loaned	(72)	(152.4)
Securities Given as Collateral on Securities Loaned	(8.9)	(63.9)
Cash Given as Collateral on Securities Loaned	(63.1)	(88.5)
Securities Loaned Net of Collateral	0	0
Offsetting Financial Assets
Gross Financial Assets	171.9	241.5
Financial Liabilities Offsetting Financial Assets in Balance Sheet	0	0
Net Financial Assets Reported in Balance Sheet	171.9	241.5
Securities Received as Collateral on Financial Assets	(100.8)	(101.9)
Cash Received as Collateral on Financial Assets	(69.5)	(137.9)
Financial Assets Net of Collateral	1.6	1.7
Offsetting Derivative Liabilities
Net Derivative Liabilities Reported in Balance Sheet	117.7	87.9
Offsetting Securities Borrowed
Security Borrowed, Subject to Master Netting Arrangement, before Offset	63.1	88.5
Security Borrowed, Subject to Master Netting Arrangement, Liability Offset	0	0
Securities Borrowed	63.1	88.5
Securities Received as Collateral on Securities Borrowed	(63.1)	(88.5)
Cash Received as Collateral on Securities Borrowed	0	0
Security Borrowed, Including Not Subject to Master Netting Arrangement, after Offset and Deduction	0	0
Offsetting Financial Liabilities
Gross Financial Liability	179.3	162.5
Financial Assets Offsetting Financial Liabilities in Balance Sheet	0	0
Net Financial Liabilities Reported in Balance Sheet	179.3	162.5
Securities Given as Collateral on Financial Liabilities	(172.5)	(161.7)
Cash Given as Collateral on Financial Liabilities	0	0
Financial Liabilities Net of Collateral	6.8	0.8
Over the Counter
Offsetting Derivative Assets
Derivative Asset, Fair Value, Gross Asset	99.9	89.1
Derivative Liabilities Offsetting Derivative Assets in Balance Sheet	0	0
Net Derivative Assets Reported in Balance Sheet	99.9	89.1
Securities Received as Collateral on Derivative Assets	(91.9)	(38)
Derivative Asset, Subject to Master Netting Arrangement, Collateral, Obligation to Return Cash Not Offset	(6.4)	(49.4)
Derivative Assets Net of Collateral	1.6	1.7
Offsetting Derivative Liabilities
Gross Derivative Liability	116.2	74
Derivative Assets Offsetting Derivative Liabilities in Balance Sheet	0	0
Net Derivative Liabilities Reported in Balance Sheet	116.2	74
FMS Collateral Posted to Counterparties	(109.4)	(73.2)
Derivative Liability, Subject to Master Netting Arrangement, Collateral, Right to Reclaim Cash Not Offset	0	0
Derivative Liabilities Net of Collateral	$ 6.8	$ 0.8

Investments Investment Income (

Investments Investment Income (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Net Investment Income
Investment Income, Interest and Dividend		$ 2,170.6	$ 2,173.6	$ 2,260.6
Less Investment Expenses		61.8	39.4	35.1
Less Investment Income on PFA Assets		12.1	12	12.3
Net Investment Income		2,096.7	2,122.2	2,213.2
Fixed Maturity Securities
Net Investment Income
Investment Income, Interest and Dividend		1,853.7	1,849.8	1,888.2
Derivatives
Net Investment Income
Investment Income, Interest and Dividend		45.1	57.8	68.6
Mortgage Loans
Net Investment Income
Investment Income, Interest and Dividend		92.5	101.5	105
Policy Loans
Net Investment Income
Investment Income, Interest and Dividend		20.8	20	19.7
Perpetual Preferred Securities
Net Investment Income
Investment Income, Interest and Dividend	[1]	2.5	5	6.9
Private Equity Partnerships
Net Investment Income
Investment Income, Interest and Dividend	[2]	78.1	110.1	165.4
Other Long-term Investments
Net Investment Income
Investment Income, Interest and Dividend		9.2	9.4	5.5
Short-term Investments
Net Investment Income
Investment Income, Interest and Dividend		$ 68.7	$ 20	$ 1.3
[1]The net unrealized gain (loss) recognized in net investment income for the year ended December 31, 2023 related to perpetual preferred securities still held at December 31, 2023 was nominal . The net unrealized gain (loss) recognized in net investment income for the years ended December 31, 2022 and 2021 related to perpetual preferred securities still held at year-end was $2.8 million and $4.4 million, respectively. $(14.0) million and $(12.3) million, respectively. See Note 2 for further discussion of private equity partnerships.

Investment Gains and Losses Rep

Investment Gains and Losses Reported in Consolidated Statements of Income (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Fixed Maturity Securities
Debt Securities, Available-for-sale, Realized Gain	$ 4.4	$ 2.3	$ 76.2	[1]
Gross Losses on Sales	(53.1)	(28.8)	(11.5)
Credit Losses	(2.2)	(4.6)	(9.3)
Mortgage Loans and Other Invested Assets
Gross Gains on Sales	6	1.4	5.8
Gross Losses on Sales	(1)	0	0
Impairment Loss	(3)	0	0
Credit Losses	(0.9)	(1)	4.7
Gain (Loss) on Embedded Derivative	12.4	16.2	9.7
All Other Derivatives	(0.6)	2.6	3.1
Foreign Currency Transactions	2	(3.8)	(2)
Net Investment Gain (Loss)	$ (36)	$ (15.7)	$ 76.7
[1] Gross gains on sales of fixed maturity securities for the year ended December 31, 2021 includes gains of $67.6 million as a result of the second phase of the reinsurance transaction that we completed during the first quarter of 2021. See Note 14 for further discussion.

Investments - Additional Inform

Investments - Additional Information (Detail)		12 Months Ended
		Dec. 31, 2023 USD ($) Integer	Dec. 31, 2022 USD ($) Integer	Dec. 31, 2021 USD ($) Integer
Schedule of Investments
Financing Receivable, Troubled Debt Restructuring, Postmodification		$ 8,000,000
Other Long-term Investments		1,579,400,000	$ 1,440,100,000
Unfunded Commitments		200,000
Financing Receivable, Allowance for Credit Losses		10,200,000
Accrued Investment Income		633,900,000	615,000,000
Financing Receivable, Allowance for Credit Loss, Writeoff		$ 0	0
Financing Receivable, Modified, Weighted Average Term Increase from Modification		18 months
Foreclosed Real Estate Expense		$ 0	0	$ 0
Committments to Fund Commercial Mortgage Loans		0	5,000,000
Real Estate Investment Property, Net		64,400,000	71,600,000
Real Estate Held-for-sale		$ 40,900,000	40,900,000
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%
Gross Securities Loaned		$ 72,000,000	152,400,000
Outstanding Repurchase Agreements		0	0
Perpetual Preferred Securities
Schedule of Investments
Unrealized Gain (Loss) on Investments	[1]	0	2,800,000	4,400,000
Private Equity Partnerships
Schedule of Investments
Unrealized Gain (Loss) on Investments		102,900,000	124,100,000	177,700,000
Management Fee Expense		24,800,000	14,000,000	12,300,000
Off Balance Sheet Amount
Schedule of Investments
Cash Collateral for Borrowed Securities		63,100,000	88,500,000
Securities Received as Collateral		12,500,000	69,800,000
Commercial Real Estate
Schedule of Investments
Financing Receivable, Troubled Debt Restructuring, Postmodification		14,200,000
Financing Receivable, before Allowance for Credit Loss		2,328,400,000	2,444,700,000
Financing Receivable, Allowance for Credit Losses		10,200,000	9,300,000	$ 8,300,000
Accrued Investment Income		7,200,000	7,700,000
Financing Receivable, Allowance for Credit Loss, Writeoff		$ 0	$ 0
Financing Receivable, Modifications, Number of Contracts | Integer		0	0	0
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing		$ 0	$ 0	$ 0
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment		0	0	$ 0
Unfunded Mortgage Loan Commitments
Schedule of Investments
Allowance for Credit Losses, Unfunded Mortgage Loan Commitments		0	0
Variable Interest Entity, Not Primary Beneficiary
Schedule of Investments
Other Long-term Investments		1,326,500,000	1,195,300,000
Tax Credit Partnership | Variable Interest Entity, Not Primary Beneficiary
Schedule of Investments
Other Long-term Investments		300,000	1,000,000
Private Equity Partnerships | Variable Interest Entity, Not Primary Beneficiary
Schedule of Investments
Other Long-term Investments		1,326,200,000	1,194,300,000
Private Placement Fixed Maturity
Schedule of Investments
Fair Value Disclosure, off-Balance-Sheet Risks, Amount, Liability		$ 122,000,000
Public Utilities | Principal Forgiveness
Schedule of Investments
Financing Receivable, Troubled Debt Restructuring			4,800,000
Private Equity Funds
Schedule of Investments
Financing Receivable, Troubled Debt Restructuring, Postmodification			$ 4,900,000
External Credit Rating, Investment Grade
Schedule of Investments
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions		832
Number of Fixed Maturity Securities in an Unrealized Loss Position Continuously for Over One Year		787
External Credit Rating, Below-Investment-Grade
Schedule of Investments
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions		75
Number of Fixed Maturity Securities in an Unrealized Loss Position Continuously for Over One Year		70
[1] The net unrealized gain (loss) recognized in net investment income for the year ended December 31, 2023 related to perpetual preferred securities still held at December 31, 2023 was nominal . The net unrealized gain (loss) recognized in net investment income for the years ended December 31, 2022 and 2021 related to perpetual preferred securities still held at year-end was $2.8 million and $4.4 million, respectively.

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, 2023	Dec. 31, 2022
Derivative
Derivative Asset, Fair Value, Amount Offset Against Collateral	$ 37.4	$ 49.4
Derivative Liability, Subject to Master Netting Arrangement, Deduction of Financial Instrument Not Offset	39.8	44.7
Cash
Derivative
Cash Collateral from Counterparties	11.1	49.4
Cash Collateral Posted to Counterparties	0	5.1
Fixed Maturity Securities
Derivative
Carrying Value of Fixed Maturity Securities Received as Collateral from Counterparties	26.3	0
FMS Collateral Posted to Counterparties	$ 39.8	$ 39.6

Derivative Financial Instrume_4

Derivative Financial Instruments Fair Value Hedges Carrying Amount of Hedged Assets and Liabilities and Cumulative Basis Adjustments (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Derivative Instruments and Hedging Activities Disclosures
Hedged Asset, Statement of Financial Position [Extensible Enumeration]	Fixed Maturity Securities - at fair value (amortized cost of $38,410.6; $37,825.2; allowance for credit losses of $2.2; $—)	Fixed Maturity Securities - at fair value (amortized cost of $38,410.6; $37,825.2; allowance for credit losses of $2.2; $—)
Interest Rate Swaps | Receive Fixed/Pay Fixed | Designated as Hedging Instrument | Fair Value Hedging
Derivative Instruments and Hedging Activities Disclosures
Hedged Asset, Fair Value Hedge	$ 529.2	$ 394.4
Interest Rate Swaps | Receive Fixed/Pay Fixed | Designated as Hedging Instrument | Fair Value Hedging | Fixed Maturity Securities
Derivative Instruments and Hedging Activities Disclosures
Hedged Asset, Fair Value Hedge, Cumulative Increase (Decrease)	$ (6.1)	$ (24.8)

Location and Fair Values of Der

Location and Fair Values of Derivative Financial Instruments (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Derivative
Derivative, Notional Amount	$ 2,983.7	$ 1,753.9
Other Long-term Investments
Derivative
Asset Derivatives Fair Value	99.9	89.1
Other Liabilities
Derivative
Liability Derivatives Fair Value	117.7	87.9
Designated as Hedging Instrument
Derivative
Derivative, Notional Amount	2,697	1,490.7
Designated as Hedging Instrument | Cash Flow Hedging
Derivative
Derivative, Notional Amount	2,054.5	932.9
Designated as Hedging Instrument | Forwards | Cash Flow Hedging
Derivative
Derivative, Notional Amount	1,905	764
Designated as Hedging Instrument | Interest Rate Swaps | Cash Flow Hedging
Derivative
Derivative, Notional Amount	149.5	168.9
Designated as Hedging Instrument | Interest Rate Swaps | Fair Value Hedging
Derivative
Derivative, Notional Amount	642.5	557.8
Designated as Hedging Instrument | Other Long-term Investments
Derivative
Asset Derivatives Fair Value	96.9	85.1
Designated as Hedging Instrument | Other Long-term Investments | Cash Flow Hedging
Derivative
Asset Derivatives Fair Value	58.7	19.1
Designated as Hedging Instrument | Other Long-term Investments | Forwards | Cash Flow Hedging
Derivative
Asset Derivatives Fair Value	44.5	1.6
Designated as Hedging Instrument | Other Long-term Investments | Interest Rate Swaps | Cash Flow Hedging
Derivative
Asset Derivatives Fair Value	14.2	17.5
Designated as Hedging Instrument | Other Long-term Investments | Interest Rate Swaps | Fair Value Hedging
Derivative
Asset Derivatives Fair Value	38.2	66
Designated as Hedging Instrument | Other Liabilities
Derivative
Liability Derivatives Fair Value	99	56.9
Designated as Hedging Instrument | Other Liabilities | Cash Flow Hedging
Derivative
Liability Derivatives Fair Value	82.3	51.5
Designated as Hedging Instrument | Other Liabilities | Forwards | Cash Flow Hedging
Derivative
Liability Derivatives Fair Value	77.8	48.4
Designated as Hedging Instrument | Other Liabilities | Interest Rate Swaps | Cash Flow Hedging
Derivative
Liability Derivatives Fair Value	4.5	3.1
Designated as Hedging Instrument | Other Liabilities | Interest Rate Swaps | Fair Value Hedging
Derivative
Liability Derivatives Fair Value	16.7	5.4
Not Designated as Hedging Instrument
Derivative
Derivative, Notional Amount	286.7	263.2
Not Designated as Hedging Instrument | Forwards
Derivative
Derivative, Notional Amount	52.5	54.3
Not Designated as Hedging Instrument | Interest Rate Swaps
Derivative
Derivative, Notional Amount	132	132
Not Designated as Hedging Instrument | Total Return Swap
Derivative
Derivative, Notional Amount	102.2	76.9
Not Designated as Hedging Instrument | Embedded Derivative in Modified Coinsurance Arrangement
Derivative
Derivative, Notional Amount	0	0
Not Designated as Hedging Instrument | Other Long-term Investments
Derivative
Asset Derivatives Fair Value	3	4
Not Designated as Hedging Instrument | Other Long-term Investments | Forwards
Derivative
Asset Derivatives Fair Value	3	4
Not Designated as Hedging Instrument | Other Long-term Investments | Interest Rate Swaps
Derivative
Asset Derivatives Fair Value	0	0
Not Designated as Hedging Instrument | Other Long-term Investments | Total Return Swap
Derivative
Asset Derivatives Fair Value	0	0
Not Designated as Hedging Instrument | Other Long-term Investments | Embedded Derivative in Modified Coinsurance Arrangement
Derivative
Asset Derivatives Fair Value	0	0
Not Designated as Hedging Instrument | Other Liabilities
Derivative
Liability Derivatives Fair Value	18.7	31
Not Designated as Hedging Instrument | Other Liabilities | Forwards
Derivative
Liability Derivatives Fair Value	0.2	0.1
Not Designated as Hedging Instrument | Other Liabilities | Interest Rate Swaps
Derivative
Liability Derivatives Fair Value	17	17
Not Designated as Hedging Instrument | Other Liabilities | Total Return Swap
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	$ 1.5	$ 13.9

Derivative Financial Instrume_5

Derivative Financial Instruments Location of Gains and Losses Designated as Hedging Instruments, Consolidated Statements of Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Derivative Instruments, Gain (Loss)
Net Investment Income	$ 2,096.7	$ 2,122.2	$ 2,213.2
Net Investment Gain (Loss)	(36)	(15.7)	76.7
Interest and Debt Expense	194.8	188.5	185
Derivative, Gain (Loss) on Derivative, Net	0.6	(2.6)	(3.1)
Designated as Hedging Instrument | Interest Rate Swaps | Net Investment Income | Cash Flow Hedging
Derivative Instruments, Gain (Loss)
Net Investment Income	198.6	200	220.4
Derivative, Gain (Loss) on Derivative, Net	35.2	51	64.6
Designated as Hedging Instrument | Interest Rate Swaps | Net Realized Investment Gain (Loss) | Cash Flow Hedging
Derivative Instruments, Gain (Loss)
Net Investment Gain (Loss)	0.8	0	2.7
Derivative, Gain (Loss) on Derivative, Net	0	0	2
Designated as Hedging Instrument | Interest Rate Swaps | Interest and Debt Expense | Cash Flow Hedging
Derivative Instruments, Gain (Loss)
Interest and Debt Expense	2.9	2.9	29.2
Derivative, Gain (Loss) on Derivative, Net	0	0	5
Designated as Hedging Instrument | Foreign Exchange Contracts | Net Investment Income | Cash Flow Hedging
Derivative Instruments, Gain (Loss)
Net Investment Income	9.6	12.3	13
Derivative, Gain (Loss) on Derivative, Net	0	(0.8)	1.8
Designated as Hedging Instrument | Foreign Exchange Contracts | Net Investment Income | Fair Value Hedging
Derivative Instruments, Gain (Loss)
Net Investment Income	14.5	11.6	9.8
Derivative, Gain (Loss) on Derivative, Net	11.1	7.3	4.6
Designated as Hedging Instrument | Foreign Exchange Contracts | Net Realized Investment Gain (Loss) | Cash Flow Hedging
Derivative Instruments, Gain (Loss)
Net Investment Gain (Loss)	0.4	(2.3)	(0.1)
Derivative, Gain (Loss) on Derivative, Net	(0.4)	1.8	(0.1)
Designated as Hedging Instrument | Foreign Exchange Contracts | Net Realized Investment Gain (Loss) | Fair Value Hedging
Derivative Instruments, Gain (Loss)
Net Investment Gain (Loss)	18.7	(26.8)	(22.3)
Derivative, Gain (Loss) on Derivative, Net	(18.7)	26.8	22.3
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	0	$ 0
Designated as Hedging Instrument | Forwards | Net Investment Income | Cash Flow Hedging
Derivative Instruments, Gain (Loss)
Net Investment Income	18.5	0.5
Derivative, Gain (Loss) on Derivative, Net	(0.5)	0
Designated as Hedging Instrument | Forwards | Net Realized Investment Gain (Loss) | Cash Flow Hedging
Derivative Instruments, Gain (Loss)
Net Investment Gain (Loss)	0	0
Derivative, Gain (Loss) on Derivative, Net	0	0
Designated as Hedging Instrument | Forwards | Interest and Debt Expense | Cash Flow Hedging
Derivative Instruments, Gain (Loss)
Interest and Debt Expense	0	0
Derivative, Gain (Loss) on Derivative, Net	$ 0	$ 0

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, 2023	Dec. 31, 2022	Dec. 31, 2021
Derivative Instruments, Gain (Loss)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification and Tax	$ (26.8)	$ (42.4)	$ 1.6
Forwards
Derivative Instruments, Gain (Loss)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification and Tax	(22.5)	(49.8)	(0.6)
Foreign Exchange Contracts
Derivative Instruments, Gain (Loss)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification and Tax	$ (4.3)	$ 7.4	$ 2.2

Gains and Losses on Derivatives

Gains and Losses on Derivatives Not Designated as Hedging Instruments (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Derivative Instruments, Gain (Loss)
Net Gain (Loss) on Derivatives	$ (0.6)	$ 2.6	$ 3.1
Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss)
Net Gain (Loss) on Derivatives	11.8	18.9	12.8
Credit Default 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	(0.6)	2.7	3.4
Embedded Derivative in Modified Coinsurance Arrangement | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss)
Net Gain (Loss) on Derivatives	12.4	16.2	9.7
Total Return Swap | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss)
Net Gain (Loss) on Derivatives	$ (13.6)	$ 18.9	$ (8.5)

Derivative Financial Instrume_6

Derivative Financial Instruments - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Derivative
Aggregate fair value of all derivative instruments with credit risk-related contingent features in a liability position	$ 116.2	$ 74
Derivative, Notional Amount	2,983.7	1,753.9
Interest Rate Cash Flow Hedge Gain (Loss) Reclassified to Earnings, Net			$ 0.6
Approximate amount of net deferred gains on derivative instruments expected to be amortized during the next twelve months	$ 16.7
Maximum Length of Time Hedged in Cash Flow Hedge	40 years
Component of Derivative Gain (Loss) Excluded from the Assessment of Hedge Effectiveness	$ (21.1)	17.6	16.6
Discontinued Hedge Accounting Due to Instrument No Longer Qualifying as Fair Value Hedge	0	0	0
Designated as Hedging Instrument
Derivative
Derivative, Notional Amount	2,697	1,490.7
Not Designated as Hedging Instrument
Derivative
Derivative, Notional Amount	286.7	263.2
Cash Flow Hedging | Designated as Hedging Instrument
Derivative
Derivative, Notional Amount	2,054.5	932.9
Interest Rate Swaps | Not Designated as Hedging Instrument
Derivative
Derivative, Notional Amount	132	132
Interest Rate Swaps | Cash Flow Hedging | Designated as Hedging Instrument
Derivative
Derivative, Notional Amount	149.5	168.9
Interest Rate Swaps | Fair Value Hedging | Designated as Hedging Instrument
Derivative
Derivative, Notional Amount	642.5	557.8
Credit Risk Contract | Credit Default Swaps | Not Designated as Hedging Instrument
Derivative
Derivative, Notional Amount	0	0	11.6
Forwards | Not Designated as Hedging Instrument
Derivative
Derivative, Notional Amount	52.5	54.3
Forwards | Cash Flow Hedging | Designated as Hedging Instrument
Derivative
Derivative, Notional Amount	1,905	764
Derivative, Loss on Derivative			1.2
Notional Amount Of Derivatives Terminations			250
Notional Amount Of Derivatives Additions			$ 250
Total Return Swap | Not Designated as Hedging Instrument
Derivative
Derivative, Notional Amount	102.2	76.9
Receive Fixed/Pay Fixed | Interest Rate Swaps | Not Designated as Hedging Instrument
Derivative
Derivative, Notional Amount	132	132
Receive Fixed/Pay Fixed | Interest Rate Swaps | Cash Flow Hedging | Designated as Hedging Instrument
Derivative
Derivative, Notional Amount	149.5	168.9
Receive Fixed/Pay Fixed | Interest Rate Swaps | Fair Value Hedging | Designated as Hedging Instrument
Derivative
Derivative, Notional Amount	642.5	557.8
Credit Exposure
Derivative
Credit Exposure on Derivatives	$ 1.6	$ 1.7

Schedule of Accumulated Other C

Schedule of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Jan. 01, 2021	Dec. 31, 2020
Accumulated Other Comprehensive Income (Loss)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ (3,308)	$ (3,448.3)	$ (5,164.6)	$ 4,166	$ (6,310.2)
Other Comprehensive Income (Loss) Before Reclassifications	121.7	1,721.9	1,219.3
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	(18.6)	5.6	73.7
Total Other Comprehensive Income	140.3	1,716.3	1,145.6
Net Unrealized Gain (Loss) on Securities
Accumulated Other Comprehensive Income (Loss)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(1,919.1)	(3,028.4)	4,014.4		5,315.8
Other Comprehensive Income (Loss) Before Reclassifications	1,069.3	(7,066)	(1,260.7)
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	(40)	(23.2)	40.7
Total Other Comprehensive Income	1,109.3	(7,042.8)	(1,301.4)
AOCI, Liability for Future Policy Benefit, Parent
Accumulated Other Comprehensive Income (Loss)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(648.4)	313.9	(8,570.7)	$ (10,932.5)
Other Comprehensive Income (Loss) Before Reclassifications	(962.3)	8,884.6	2,361.8
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	0	0	0
Total Other Comprehensive Income	(962.3)	8,884.6	2,361.8
Net Gain on Hedges
Accumulated Other Comprehensive Income (Loss)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(73.7)	(9.6)	61.8		97.8
Other Comprehensive Income (Loss) Before Reclassifications	(37.4)	(30.4)	14.7
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	26.7	41	50.7
Total Other Comprehensive Income	(64.1)	(71.4)	(36)
Foreign Currency Translation Adjustment
Accumulated Other Comprehensive Income (Loss)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(321.1)	(390.1)	(274.1)		(261.3)
Other Comprehensive Income (Loss) Before Reclassifications	69	(116)	(12.8)
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	0	0	0
Total Other Comprehensive Income	69	(116)	(12.8)
Unrecognized Pension and Postretirement Benefit Costs
Accumulated Other Comprehensive Income (Loss)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(345.7)	(334.1)	(396)		$ (530)
Other Comprehensive Income (Loss) Before Reclassifications	(16.9)	49.7	116.3
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	(5.3)	(12.2)	(17.7)
Total Other Comprehensive Income	$ (11.6)	$ 61.9	$ 134

Schedule of Reclassifications O

Schedule of Reclassifications Out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Net Investment Gain (Loss)	$ (36)	$ (15.7)	$ 76.7
Net Investment Income	2,096.7	2,122.2	2,213.2
Other Expenses	(1,112)	(1,006.7)	(999.3)
Income Tax Expense (Benefit)	356.3	342.8	279.6
Net Income	1,283.8	1,407.2	981
Reclassification out of Accumulated Other Comprehensive Income | Net Unrealized Gain (Loss) on Securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Net Investment Gain (Loss)	(48.7)	(24.8)	60.8
Other-Than-Temporary Impairment Loss	(2.2)	(4.6)	(9.3)
Income Before Income Tax	(50.9)	(29.4)	51.5
Income Tax Expense (Benefit)	(10.9)	(6.2)	10.8
Net Income	(40)	(23.2)	40.7
Reclassification out of Accumulated Other Comprehensive Income | Net Gain on Hedges
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Income Before Income Tax	33.8	51.9	64.2
Income Tax Expense (Benefit)	7.1	10.9	13.5
Net Income	26.7	41	50.7
Reclassification out of Accumulated Other Comprehensive Income | Net Gain on Hedges | Interest Rate Swaps
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Net Investment Gain (Loss)	0	0	2
Net Investment Income	34.7	51.1	60.6
Reclassification out of Accumulated Other Comprehensive Income | Net Gain on Hedges | Foreign Exchange Contracts
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Net Investment Gain (Loss)	(0.4)	1.8	(0.1)
Net Investment Income	(0.5)	(1)	1.7
Reclassification out of Accumulated Other Comprehensive Income | Net Actuarial Loss
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Other Expenses	(7.2)	(15.7)	(22.6)
Reclassification out of Accumulated Other Comprehensive Income | Prior Service Credit
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Other Expenses	0.2	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	(7)	(15.5)	(22.4)
Income Tax Expense (Benefit)	(1.7)	(3.3)	(4.7)
Net Income	$ (5.3)	$ (12.2)	$ (17.7)

Liability for Future Policy Ben

Liability for Future Policy Benefit, Activity (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022		Dec. 31, 2021	Jan. 01, 2021		Dec. 31, 2020
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Future Policy Benefits		$ 40,009.4	$ 38,577.1	[1]
Unum US
Liability for Future Policy Benefit, Expected Net Premium [Roll Forward]
Liability for Future Policy Benefit, Expected Net Premium, before Reinsurance, after Discount Rate Change, balance beginning of year		2,071.1	2,619.1		$ 2,753.5
Liability for Future Policy Benefit, Expected Net Premium, Original Discount Rate, before Cash Flow and Reinsurance, balance beginning of year		2,166	2,311.9		2,355.7
Liability for Future Policy Benefit, Expected Net Premium, Cumulative Increase (Decrease) from Cash Flow Change			185.7		(97.1)			$ (48.5)
Liability for Future Policy Benefit, Expected Net Premium, Cumulative Increase (Decrease) of Actual Variance from Expected Experience			(90.2)		(96.1)			(127.9)
Liability for Future Policy Benefit, Expected Net Premium, Original Discount Rate, before Reinsurance, after Cash Flow Change			2,261.5		2,118.7			2,179.3
Liability for Future Policy Benefit, Expected Net Premium, Issuance		486.5	304.8		407.8
Liability for Future Policy Benefit, Expected Net Premium, Interest Income		77.2	78.9		96.2
Liability for Future Policy Benefit, Expected Net Premium, Net Premium Collected		(338.3)	(336.4)		(371.4)
Liability for Future Policy Benefit, Expected Net Premium, Original Discount Rate, before Cash Flow and Reinsurance, balance end of period		2,486.9	2,166		2,311.9
AOCI, Liability for Future Policy Benefit, Expected Net Premium, before Tax		(55.5)	(94.9)		307.2
Liability for Future Policy Benefit, Expected Net Premium, before Reinsurance, after Discount Rate Change, balance end of period		2,431.4	2,071.1		2,619.1
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Liability for Future Policy Benefit, Expected Future Policy Benefit, before Reinsurance, after Discount Rate Change, balance beginning of year		11,698.2	14,564.4		15,402.6
Liability for Future Policy Benefit, Expected Future Policy Benefit, Original Discount Rate, before Cash Flow and Reinsurance, balance at beginning of year		12,177.3	12,671.7		12,874
Liability for Future Policy Benefit, Expected Future Policy Benefit, Cumulative Increase (Decrease) from Cash Flow Change			77.8		(228.2)			(249.2)
Liability for Future Policy Benefit, Expected Future Policy Benefit, Cumulative Increase (Decrease) of Actual Variance from Expected Experience			(377.2)		(384.6)			(404.1)
Liability for Future Policy Benefit, Expected Future Benefit, Original Discount Rate, before Reinsurance, after Cash Flow Change			11,877.9		12,058.9			12,220.7
Liability for Future Policy Benefit, Expected Future Policy Benefit, Issuance	[2]	2,007.7	2,083.8		2,382
Liability for Future Policy Benefit, Expected Future Policy Benefit, Interest Expense		442.1	476.4		531.8
Liability for Future Policy Benefit, Expected Future Policy Benefit, Benefit Payment		(2,378.2)	(2,441.8)		(2,462.8)
Liability for Future Policy Benefit, Expected Future Policy Benefit, Original Discount Rate, before Cash Flow and Reinsurance, balance at end of period		11,949.5	12,177.3		12,671.7
AOCI, Liability for Future Policy Benefit, Expected Future Policy Benefit, before Tax		(197)	(479.1)		1,892.7
Liability for Future Policy Benefit, Expected Future Policy Benefit, before Reinsurance, after Discount Rate Change, balance end of period		11,752.5	11,698.2		14,564.4
Liability for Future Policy Benefit, before Reinsurance, before Other		9,321.1	9,627.1		11,945.3
Liability for Future Policy Benefits, Other Contracts		31.6	41.6		74.7
Liability for Future Policy Benefit, before Reinsurance, after Other		9,352.7	9,668.7		12,020	$ 12,861.4
Liability for Future Policy Benefit, Reinsurance Recoverable, after Allowance		208.6	251.2		308.4	357.7	[3]
Liability for Future Policy Benefit, after Reinsurance		9,144.1	9,417.5		11,711.6	12,503.7
Gross premiums or assessments		6,263.2	6,021.7		5,853.8
interest accretion		364.9	397.5		435.6
Liability for Future Policy Benefit, Expected Future Policy Benefit, Undiscounted, before Reinsurance		17,926.6	17,850.4		18,166.1
Liability for Future Policy Benefit, Expected Future Gross Premium, Undiscounted, before Reinsurance		11,175.4	9,504.7		9,734.2
Liability for Future Policy Benefit, Expected Future Gross Premium, Discounted, before Reinsurance		$ 7,830.4	$ 6,901.2		$ 7,115.3
Liability for Future Policy Benefit, Weighted-Average Interest Accretion Rate		4.20%	4%		4.10%
Liability for Future Policy Benefit, Current Weighted-Average Discount Rate		4.50%	4.70%		2.10%
Liability for Future Policy Benefit, Weighted-Average Duration		7 years	6 years 9 months 18 days		6 years 6 months
Future Policy Benefits	[4]	$ 9,352.7	$ 9,668.7		$ 12,020
Unum International
Liability for Future Policy Benefit, Expected Net Premium [Roll Forward]
Liability for Future Policy Benefit, Expected Net Premium, before Reinsurance, after Discount Rate Change, balance beginning of year		197.1	260.5		311.7
Liability for Future Policy Benefit, Expected Net Premium, Original Discount Rate, before Cash Flow and Reinsurance, balance beginning of year		246.8	258.1		251.4
Liability for Future Policy Benefit, Expected Net Premium, Cumulative Increase (Decrease) from Cash Flow Change			(5.1)		(0.3)			0
Liability for Future Policy Benefit, Expected Net Premium, Cumulative Increase (Decrease) of Actual Variance from Expected Experience			17.1		5.6			9.3
Liability for Future Policy Benefit, Expected Net Premium, Original Discount Rate, before Reinsurance, after Cash Flow Change			258.8		263.4			260.7
Liability for Future Policy Benefit, Expected Net Premium, Issuance		23.5	17.8		31.4
Liability for Future Policy Benefit, Expected Net Premium, Interest Income		9.4	8.4		8.9
Liability for Future Policy Benefit, Expected Net Premium, Net Premium Collected		(23)	(22.2)		(22.6)
Liability for Future Policy Benefit, Expected Net Premium, Increase (Decrease) for Other Change		29.7	(20.6)		(20.3)
Liability for Future Policy Benefit, Expected Net Premium, Original Discount Rate, before Cash Flow and Reinsurance, balance end of period		298.4	246.8		258.1
AOCI, Liability for Future Policy Benefit, Expected Net Premium, before Tax		(28.1)	(49.7)		2.4
Liability for Future Policy Benefit, Expected Net Premium, before Reinsurance, after Discount Rate Change, balance end of period		270.3	197.1		260.5
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Liability for Future Policy Benefit, Expected Future Policy Benefit, before Reinsurance, after Discount Rate Change, balance beginning of year		2,231.4	3,181.8		3,465.9
Liability for Future Policy Benefit, Expected Future Policy Benefit, Original Discount Rate, before Cash Flow and Reinsurance, balance at beginning of year		2,495.5	2,703.8		2,644.5
Liability for Future Policy Benefit, Expected Future Policy Benefit, Cumulative Increase (Decrease) from Cash Flow Change			17.7		(20.1)			(5.5)
Liability for Future Policy Benefit, Expected Future Policy Benefit, Cumulative Increase (Decrease) of Actual Variance from Expected Experience			1.3		46.3			15.9
Liability for Future Policy Benefit, Expected Future Benefit, Original Discount Rate, before Reinsurance, after Cash Flow Change			2,514.5		2,730			2,654.9
Liability for Future Policy Benefit, Expected Future Policy Benefit, Issuance	[5]	335.2	327.7		391.6
Liability for Future Policy Benefit, Expected Future Policy Benefit, Interest Expense		63.5	64.9		75.9
Liability for Future Policy Benefit, Expected Future Policy Benefit, Benefit Payment		(388.3)	(346.7)		(360.3)
Liability for Future Policy Benefit, Expected Future Policy Benefit, Increase (Decrease) for Other Change		162.2	(280.4)		(58.3)
Liability for Future Policy Benefit, Expected Future Policy Benefit, Original Discount Rate, before Cash Flow and Reinsurance, balance at end of period		2,687.1	2,495.5		2,703.8
AOCI, Liability for Future Policy Benefit, Expected Future Policy Benefit, before Tax		(159.7)	(264.1)		478
Liability for Future Policy Benefit, Expected Future Policy Benefit, before Reinsurance, after Discount Rate Change, balance end of period		2,527.4	2,231.4		3,181.8
Liability for Future Policy Benefit, before Reinsurance, before Other		2,257.1	2,034.3		2,921.3
Liability for Future Policy Benefits, Other Contracts		36.1	28.9		34.5
Liability for Future Policy Benefit, before Reinsurance, after Other		2,293.2	2,063.2		2,955.8	3,203.4
Liability for Future Policy Benefit, Reinsurance Recoverable, after Allowance		78.7	70.3		125.3	132.5	[3]
Liability for Future Policy Benefit, after Reinsurance		2,214.5	1,992.9		2,830.5	3,070.9
Gross premiums or assessments		849	786.8		793.9
interest accretion		54.1	56.5		67
Liability for Future Policy Benefit, Expected Future Policy Benefit, Undiscounted, before Reinsurance		4,261.1	3,905.4		4,292.2
Liability for Future Policy Benefit, Expected Future Gross Premium, Undiscounted, before Reinsurance		1,196.6	943.9		914.9
Liability for Future Policy Benefit, Expected Future Gross Premium, Discounted, before Reinsurance		$ 778.6	$ 626.2		$ 620.8
Liability for Future Policy Benefit, Weighted-Average Interest Accretion Rate		4%	4%		4%
Liability for Future Policy Benefit, Current Weighted-Average Discount Rate		4.60%	5%		2%
Liability for Future Policy Benefit, Weighted-Average Duration		8 years 7 months 6 days	8 years 7 months 6 days		8 years 9 months 18 days
Future Policy Benefits		$ 2,293.2	$ 2,063.2		$ 2,955.8
Colonial Life
Liability for Future Policy Benefit, Expected Net Premium [Roll Forward]
Liability for Future Policy Benefit, Expected Net Premium, before Reinsurance, after Discount Rate Change, balance beginning of year		3,745.4	4,597		4,671.9
Liability for Future Policy Benefit, Expected Net Premium, Original Discount Rate, before Cash Flow and Reinsurance, balance beginning of year		4,046.4	4,158.9		4,233.7
Liability for Future Policy Benefit, Expected Net Premium, Cumulative Increase (Decrease) from Cash Flow Change			(322.7)		(32.3)			(157.1)
Liability for Future Policy Benefit, Expected Net Premium, Cumulative Increase (Decrease) of Actual Variance from Expected Experience			(53.5)		(145.6)			(60.4)
Liability for Future Policy Benefit, Expected Net Premium, Original Discount Rate, before Reinsurance, after Cash Flow Change			3,670.2		3,981			4,016.2
Liability for Future Policy Benefit, Expected Net Premium, Issuance		544.9	554.9		644.7
Liability for Future Policy Benefit, Expected Net Premium, Interest Income		122.7	129.7		156.2
Liability for Future Policy Benefit, Expected Net Premium, Net Premium Collected		(583.5)	(619.2)		(658.2)
Liability for Future Policy Benefit, Expected Net Premium, Original Discount Rate, before Cash Flow and Reinsurance, balance end of period		3,754.3	4,046.4		4,158.9
AOCI, Liability for Future Policy Benefit, Expected Net Premium, before Tax		(161.7)	(301)		438.1
Liability for Future Policy Benefit, Expected Net Premium, before Reinsurance, after Discount Rate Change, balance end of period		3,592.6	3,745.4		4,597
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Liability for Future Policy Benefit, Expected Future Policy Benefit, before Reinsurance, after Discount Rate Change, balance beginning of year		5,581.1	7,054.8		7,022.9
Liability for Future Policy Benefit, Expected Future Policy Benefit, Original Discount Rate, before Cash Flow and Reinsurance, balance at beginning of year		6,163.9	6,201.5		6,169.6
Liability for Future Policy Benefit, Expected Future Policy Benefit, Cumulative Increase (Decrease) from Cash Flow Change			(402.9)		(85.9)			(178.1)
Liability for Future Policy Benefit, Expected Future Policy Benefit, Cumulative Increase (Decrease) of Actual Variance from Expected Experience			(52)		(191.3)			(95.2)
Liability for Future Policy Benefit, Expected Future Benefit, Original Discount Rate, before Reinsurance, after Cash Flow Change			5,709		5,924.3			5,896.3
Liability for Future Policy Benefit, Expected Future Policy Benefit, Issuance		605.9	628.5		704.1
Liability for Future Policy Benefit, Expected Future Policy Benefit, Interest Expense		211.3	217		243.1
Liability for Future Policy Benefit, Expected Future Policy Benefit, Benefit Payment		(601)	(605.9)		(642)
Liability for Future Policy Benefit, Expected Future Policy Benefit, Original Discount Rate, before Cash Flow and Reinsurance, balance at end of period		5,925.2	6,163.9		6,201.5
AOCI, Liability for Future Policy Benefit, Expected Future Policy Benefit, before Tax		(359.2)	(582.8)		853.3
Liability for Future Policy Benefit, Expected Future Policy Benefit, before Reinsurance, after Discount Rate Change, balance end of period		5,566	5,581.1		7,054.8
Liability for Future Policy Benefit, before Reinsurance, before Other		1,973.4	1,835.7		2,457.8
Liability for Future Policy Benefits, Other Contracts		24.4	22.7		25.1
Liability for Future Policy Benefit, before Reinsurance, after Other		1,997.8	1,858.4		2,482.9	2,528.6
Liability for Future Policy Benefit, Reinsurance Recoverable, after Allowance		1.8	1.1		2.3	4.4	[3]
Liability for Future Policy Benefit, after Reinsurance		1,996	1,857.3		2,480.6	2,524.2
Gross premiums or assessments		1,658.6	1,635.8		1,615.8
interest accretion		88.6	87.3		86.9
Liability for Future Policy Benefit, Expected Future Policy Benefit, Undiscounted, before Reinsurance		9,796.7	10,011.9		9,583.1
Liability for Future Policy Benefit, Expected Future Gross Premium, Undiscounted, before Reinsurance		11,903.1	12,221.3		11,487.9
Liability for Future Policy Benefit, Expected Future Gross Premium, Discounted, before Reinsurance		$ 8,702.2	$ 8,966.3		$ 8,566.7
Liability for Future Policy Benefit, Weighted-Average Interest Accretion Rate		4.30%	4.30%		4.40%
Liability for Future Policy Benefit, Current Weighted-Average Discount Rate		4.80%	5.20%		2.70%
Liability for Future Policy Benefit, Weighted-Average Duration		17 years	17 years 6 months		16 years 4 months 24 days
Future Policy Benefits		$ 1,997.8	$ 1,858.4		$ 2,482.9
Closed Block
Liability for Future Policy Benefit, Expected Net Premium [Roll Forward]
Liability for Future Policy Benefit, Expected Net Premium, before Reinsurance, after Discount Rate Change, balance beginning of year		6,412.6	8,404.7		9,358.8
Liability for Future Policy Benefit, Expected Net Premium, Original Discount Rate, before Cash Flow and Reinsurance, balance beginning of year		6,236.1	6,457.3		6,782.7
Liability for Future Policy Benefit, Expected Net Premium, Cumulative Increase (Decrease) from Cash Flow Change			1,641.3		27.8			28.5
Liability for Future Policy Benefit, Expected Net Premium, Cumulative Increase (Decrease) of Actual Variance from Expected Experience			44.1		(33.5)			(149.3)
Liability for Future Policy Benefit, Expected Net Premium, Original Discount Rate, before Reinsurance, after Cash Flow Change			7,921.5		6,451.6			6,661.9
Liability for Future Policy Benefit, Expected Net Premium, Interest Income		374.7	349		370.6
Liability for Future Policy Benefit, Expected Net Premium, Net Premium Collected		(592.6)	(564.5)		(575.2)
Liability for Future Policy Benefit, Expected Net Premium, Original Discount Rate, before Cash Flow and Reinsurance, balance end of period		7,703.6	6,236.1		6,457.3
AOCI, Liability for Future Policy Benefit, Expected Net Premium, before Tax		419.9	176.5		1,947.4
Liability for Future Policy Benefit, Expected Net Premium, before Reinsurance, after Discount Rate Change, balance end of period		8,123.5	6,412.6		8,404.7
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Liability for Future Policy Benefit, Expected Future Policy Benefit, before Reinsurance, after Discount Rate Change, balance beginning of year		29,418.7	40,504		43,639.1
Liability for Future Policy Benefit, Expected Future Policy Benefit, Original Discount Rate, before Cash Flow and Reinsurance, balance at beginning of year		28,852.3	28,820.2		29,064.3
Liability for Future Policy Benefit, Expected Future Policy Benefit, Cumulative Increase (Decrease) from Cash Flow Change			2,009.4		241.8			52.9
Liability for Future Policy Benefit, Expected Future Policy Benefit, Cumulative Increase (Decrease) of Actual Variance from Expected Experience			117.1		(5.5)			(152.5)
Liability for Future Policy Benefit, Expected Future Benefit, Original Discount Rate, before Reinsurance, after Cash Flow Change			30,978.8		29,056.5			28,964.7
Liability for Future Policy Benefit, Expected Future Policy Benefit, Issuance	[6]	123.4	154.5		197.3
Liability for Future Policy Benefit, Expected Future Policy Benefit, Interest Expense		1,510.3	1,477.9		1,508.8
Liability for Future Policy Benefit, Expected Future Policy Benefit, Benefit Payment		(1,868.6)	(1,836.6)		(1,850.6)
Liability for Future Policy Benefit, Expected Future Policy Benefit, Original Discount Rate, before Cash Flow and Reinsurance, balance at end of period		30,743.9	28,852.3		28,820.2
AOCI, Liability for Future Policy Benefit, Expected Future Policy Benefit, before Tax		1,833.8	566.4		11,683.8
Liability for Future Policy Benefit, Expected Future Policy Benefit, before Reinsurance, after Discount Rate Change, balance end of period		32,577.7	29,418.7		40,504
Liability for Future Policy Benefit, before Reinsurance, before Other		24,454.2	23,006.1		32,099.3
Liability for Future Policy Benefits, Other Contracts	[7]	1,661.2	1,761.3		2,221.6
Liability for Future Policy Benefit, before Reinsurance, after Other		26,115.4	24,767.4		34,320.9	36,992
Liability for Future Policy Benefit, Reinsurance Recoverable, after Allowance		7,466.9	7,805.5		9,912.1	10,001.4	[3]
Liability for Future Policy Benefit, after Reinsurance		18,648.5	16,961.9		24,408.8	26,990.6
Gross premiums or assessments		919.9	947.5		999.9
interest accretion		1,135.6	1,128.9		1,138.2
Liability for Future Policy Benefit, Expected Future Policy Benefit, Undiscounted, before Reinsurance		73,341.4	65,293		66,533.5
Liability for Future Policy Benefit, Expected Future Gross Premium, Undiscounted, before Reinsurance		14,486.4	12,629.9		13,159
Liability for Future Policy Benefit, Expected Future Gross Premium, Discounted, before Reinsurance		$ 8,241.7	$ 7,333.5		$ 7,518.9
Liability for Future Policy Benefit, Weighted-Average Interest Accretion Rate		5.20%	5.20%		5.20%
Liability for Future Policy Benefit, Current Weighted-Average Discount Rate		4.90%	5.20%		2.70%
Liability for Future Policy Benefit, Weighted-Average Duration		13 years 2 months 12 days	12 years 4 months 24 days		12 years 8 months 12 days
Future Policy Benefits	[4]	$ 26,115.4	$ 24,767.4		$ 34,320.9
Other Products
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Future Policy Benefits	[4]	250.3	219.4		212
Group Disability | Unum US
Liability for Future Policy Benefit, Expected Net Premium [Roll Forward]
Liability for Future Policy Benefit, Expected Net Premium, before Reinsurance, after Discount Rate Change, balance beginning of year		0	0		0
Liability for Future Policy Benefit, Expected Net Premium, Original Discount Rate, before Cash Flow and Reinsurance, balance beginning of year		0	0		0
Liability for Future Policy Benefit, Expected Net Premium, Cumulative Increase (Decrease) from Cash Flow Change			0		0			0
Liability for Future Policy Benefit, Expected Net Premium, Cumulative Increase (Decrease) of Actual Variance from Expected Experience			0		0			0
Liability for Future Policy Benefit, Expected Net Premium, Original Discount Rate, before Reinsurance, after Cash Flow Change			0		0			0
Liability for Future Policy Benefit, Expected Net Premium, Issuance		0	0		0
Liability for Future Policy Benefit, Expected Net Premium, Interest Income		0	0		0
Liability for Future Policy Benefit, Expected Net Premium, Net Premium Collected		0	0		0
Liability for Future Policy Benefit, Expected Net Premium, Original Discount Rate, before Cash Flow and Reinsurance, balance end of period		0	0		0
AOCI, Liability for Future Policy Benefit, Expected Net Premium, before Tax		0	0		0
Liability for Future Policy Benefit, Expected Net Premium, before Reinsurance, after Discount Rate Change, balance end of period		0	0		0
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Liability for Future Policy Benefit, Expected Future Policy Benefit, before Reinsurance, after Discount Rate Change, balance beginning of year		5,533.3	6,725.7		7,281.3
Liability for Future Policy Benefit, Expected Future Policy Benefit, Original Discount Rate, before Cash Flow and Reinsurance, balance at beginning of year		5,793.1	6,158.3		6,369.4
Liability for Future Policy Benefit, Expected Future Policy Benefit, Cumulative Increase (Decrease) from Cash Flow Change			(100.2)		(102)			(186)
Liability for Future Policy Benefit, Expected Future Policy Benefit, Cumulative Increase (Decrease) of Actual Variance from Expected Experience			(204)		(239.4)			(229.3)
Liability for Future Policy Benefit, Expected Future Benefit, Original Discount Rate, before Reinsurance, after Cash Flow Change			5,488.9		5,816.9			5,954.1
Liability for Future Policy Benefit, Expected Future Policy Benefit, Issuance	[2]	1,094.5	1,304.3		1,471.4
Liability for Future Policy Benefit, Expected Future Policy Benefit, Interest Expense		171.2	210.5		241.5
Liability for Future Policy Benefit, Expected Future Policy Benefit, Benefit Payment		(1,477.5)	(1,538.6)		(1,508.7)
Liability for Future Policy Benefit, Expected Future Policy Benefit, Original Discount Rate, before Cash Flow and Reinsurance, balance at end of period		5,277.1	5,793.1		6,158.3
AOCI, Liability for Future Policy Benefit, Expected Future Policy Benefit, before Tax		(129.7)	(259.8)		567.4
Liability for Future Policy Benefit, Expected Future Policy Benefit, before Reinsurance, after Discount Rate Change, balance end of period		5,147.4	5,533.3		6,725.7
Liability for Future Policy Benefit, before Reinsurance, before Other		5,147.4	5,533.3		6,725.7
Liability for Future Policy Benefits, Other Contracts		0.2	0.4		0.5
Liability for Future Policy Benefit, before Reinsurance, after Other		5,147.6	5,533.7		6,726.2	7,295.7
Liability for Future Policy Benefit, Reinsurance Recoverable, after Allowance		30.7	36		40.9	58.3
Liability for Future Policy Benefit, after Reinsurance		5,116.9	5,497.7		6,685.3	7,237.4
Gross premiums or assessments		2,958.7	2,791.7		2,672.4
interest accretion		171.2	210.5		241.5
Liability for Future Policy Benefit, Expected Future Policy Benefit, Undiscounted, before Reinsurance		6,376.6	6,988.1		7,538.7
Liability for Future Policy Benefit, Expected Future Gross Premium, Undiscounted, before Reinsurance		0	0		0
Liability for Future Policy Benefit, Expected Future Gross Premium, Discounted, before Reinsurance		$ 0	$ 0		$ 0
Liability for Future Policy Benefit, Weighted-Average Interest Accretion Rate		4%	3.80%		4%
Liability for Future Policy Benefit, Current Weighted-Average Discount Rate		4.60%	4.90%		2.10%
Liability for Future Policy Benefit, Weighted-Average Duration		4 years 3 months 18 days	4 years 4 months 24 days		4 years 6 months
Group Life and AD&D | Unum US
Liability for Future Policy Benefit, Expected Net Premium [Roll Forward]
Liability for Future Policy Benefit, Expected Net Premium, before Reinsurance, after Discount Rate Change, balance beginning of year		$ 0	$ 0		$ 0
Liability for Future Policy Benefit, Expected Net Premium, Original Discount Rate, before Cash Flow and Reinsurance, balance beginning of year		0	0		0
Liability for Future Policy Benefit, Expected Net Premium, Cumulative Increase (Decrease) from Cash Flow Change			0		0			0
Liability for Future Policy Benefit, Expected Net Premium, Cumulative Increase (Decrease) of Actual Variance from Expected Experience			0		0			0
Liability for Future Policy Benefit, Expected Net Premium, Original Discount Rate, before Reinsurance, after Cash Flow Change			0		0			0
Liability for Future Policy Benefit, Expected Net Premium, Issuance		0	0		0
Liability for Future Policy Benefit, Expected Net Premium, Interest Income		0	0		0
Liability for Future Policy Benefit, Expected Net Premium, Net Premium Collected		0	0		0
Liability for Future Policy Benefit, Expected Net Premium, Original Discount Rate, before Cash Flow and Reinsurance, balance end of period		0	0		0
AOCI, Liability for Future Policy Benefit, Expected Net Premium, before Tax		0	0		0
Liability for Future Policy Benefit, Expected Net Premium, before Reinsurance, after Discount Rate Change, balance end of period		0	0		0
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Liability for Future Policy Benefit, Expected Future Policy Benefit, before Reinsurance, after Discount Rate Change, balance beginning of year		972.6	1,124.1		1,126.3
Liability for Future Policy Benefit, Expected Future Policy Benefit, Original Discount Rate, before Cash Flow and Reinsurance, balance at beginning of year		998.5	1,058.3		1,034.4
Liability for Future Policy Benefit, Expected Future Policy Benefit, Cumulative Increase (Decrease) from Cash Flow Change			0		(32.9)			0
Liability for Future Policy Benefit, Expected Future Policy Benefit, Cumulative Increase (Decrease) of Actual Variance from Expected Experience			(37)		(34.3)			4
Liability for Future Policy Benefit, Expected Future Benefit, Original Discount Rate, before Reinsurance, after Cash Flow Change			961.5		991.1			1,038.4
Liability for Future Policy Benefit, Expected Future Policy Benefit, Issuance	[2]	394.2	444.1		467.5
Liability for Future Policy Benefit, Expected Future Policy Benefit, Interest Expense		20	24.5		34.9
Liability for Future Policy Benefit, Expected Future Policy Benefit, Benefit Payment		(439.2)	(461.2)		(482.5)
Liability for Future Policy Benefit, Expected Future Policy Benefit, Original Discount Rate, before Cash Flow and Reinsurance, balance at end of period		936.5	998.5		1,058.3
AOCI, Liability for Future Policy Benefit, Expected Future Policy Benefit, before Tax		(14.5)	(25.9)		65.8
Liability for Future Policy Benefit, Expected Future Policy Benefit, before Reinsurance, after Discount Rate Change, balance end of period		922	972.6		1,124.1
Liability for Future Policy Benefit, before Reinsurance, before Other		922	972.6		1,124.1
Liability for Future Policy Benefits, Other Contracts		1	0.9		1.2
Liability for Future Policy Benefit, before Reinsurance, after Other		923	973.5		1,125.3	1,127.3
Liability for Future Policy Benefit, Reinsurance Recoverable, after Allowance		7.2	7.5		4.4	3
Liability for Future Policy Benefit, after Reinsurance		915.8	966		1,120.9	1,124.3
Gross premiums or assessments		1,878	1,864.9		1,827.5
interest accretion		20	24.5		34.9
Liability for Future Policy Benefit, Expected Future Policy Benefit, Undiscounted, before Reinsurance		1,063.2	1,133		1,224.7
Liability for Future Policy Benefit, Expected Future Gross Premium, Undiscounted, before Reinsurance		0	0		0
Liability for Future Policy Benefit, Expected Future Gross Premium, Discounted, before Reinsurance		$ 0	$ 0		$ 0
Liability for Future Policy Benefit, Weighted-Average Interest Accretion Rate		2.20%	2.20%		2.30%
Liability for Future Policy Benefit, Current Weighted-Average Discount Rate		2.60%	2.70%		1.30%
Liability for Future Policy Benefit, Weighted-Average Duration		2 years 7 months 6 days	2 years 7 months 6 days		2 years 10 months 24 days
Voluntary Benefits | Unum US
Liability for Future Policy Benefit, Expected Net Premium [Roll Forward]
Liability for Future Policy Benefit, Expected Net Premium, before Reinsurance, after Discount Rate Change, balance beginning of year		$ 868.2	$ 1,124.8		$ 1,239.3
Liability for Future Policy Benefit, Expected Net Premium, Original Discount Rate, before Cash Flow and Reinsurance, balance beginning of year		937.9	1,032.3		1,146.9
Liability for Future Policy Benefit, Expected Net Premium, Cumulative Increase (Decrease) from Cash Flow Change			180.7		(23.4)			(29.6)
Liability for Future Policy Benefit, Expected Net Premium, Cumulative Increase (Decrease) of Actual Variance from Expected Experience			(79.8)		(70.9)			(117.5)
Liability for Future Policy Benefit, Expected Net Premium, Original Discount Rate, before Reinsurance, after Cash Flow Change			1,038.8		938			999.8
Liability for Future Policy Benefit, Expected Net Premium, Issuance		288.6	136.2		196.5
Liability for Future Policy Benefit, Expected Net Premium, Interest Income		29	29.1		38.3
Liability for Future Policy Benefit, Expected Net Premium, Net Premium Collected		(163.9)	(165.4)		(202.3)
Liability for Future Policy Benefit, Expected Net Premium, Original Discount Rate, before Cash Flow and Reinsurance, balance end of period		1,192.5	937.9		1,032.3
AOCI, Liability for Future Policy Benefit, Expected Net Premium, before Tax		(57.8)	(69.7)		92.5
Liability for Future Policy Benefit, Expected Net Premium, before Reinsurance, after Discount Rate Change, balance end of period		1,134.7	868.2		1,124.8
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Liability for Future Policy Benefit, Expected Future Policy Benefit, before Reinsurance, after Discount Rate Change, balance beginning of year		1,999.5	2,697.3		2,768.1
Liability for Future Policy Benefit, Expected Future Policy Benefit, Original Discount Rate, before Cash Flow and Reinsurance, balance at beginning of year		2,141.2	2,201.8		2,272.6
Liability for Future Policy Benefit, Expected Future Policy Benefit, Cumulative Increase (Decrease) from Cash Flow Change			170.1		(39.9)			(40.3)
Liability for Future Policy Benefit, Expected Future Policy Benefit, Cumulative Increase (Decrease) of Actual Variance from Expected Experience			(90.9)		(74.9)			(136.5)
Liability for Future Policy Benefit, Expected Future Benefit, Original Discount Rate, before Reinsurance, after Cash Flow Change			2,220.4		2,087			2,095.8
Liability for Future Policy Benefit, Expected Future Policy Benefit, Issuance	[2]	303.7	154		220.6
Liability for Future Policy Benefit, Expected Future Policy Benefit, Interest Expense		86.2	86.1		96.9
Liability for Future Policy Benefit, Expected Future Policy Benefit, Benefit Payment		(188.3)	(185.9)		(211.5)
Liability for Future Policy Benefit, Expected Future Policy Benefit, Original Discount Rate, before Cash Flow and Reinsurance, balance at end of period		2,422	2,141.2		2,201.8
AOCI, Liability for Future Policy Benefit, Expected Future Policy Benefit, before Tax		(87.5)	(141.7)		495.5
Liability for Future Policy Benefit, Expected Future Policy Benefit, before Reinsurance, after Discount Rate Change, balance end of period		2,334.5	1,999.5		2,697.3
Liability for Future Policy Benefit, before Reinsurance, before Other		1,199.8	1,131.3		1,572.5
Liability for Future Policy Benefits, Other Contracts		2.6	15.6		14
Liability for Future Policy Benefit, before Reinsurance, after Other		1,202.4	1,146.9		1,586.5	1,659.2
Liability for Future Policy Benefit, Reinsurance Recoverable, after Allowance		14	14.1		31.2	35.7
Liability for Future Policy Benefit, after Reinsurance		1,188.4	1,132.8		1,555.3	1,623.5
Gross premiums or assessments		789.9	773.6		773.8
interest accretion		57.2	57		58.6
Liability for Future Policy Benefit, Expected Future Policy Benefit, Undiscounted, before Reinsurance		5,173.1	4,561.1		4,192.1
Liability for Future Policy Benefit, Expected Future Gross Premium, Undiscounted, before Reinsurance		5,450.6	3,979.6		4,136.9
Liability for Future Policy Benefit, Expected Future Gross Premium, Discounted, before Reinsurance		$ 3,717.5	$ 2,939.1		$ 3,156.5
Liability for Future Policy Benefit, Weighted-Average Interest Accretion Rate		5%	5.10%		5.10%
Liability for Future Policy Benefit, Current Weighted-Average Discount Rate		4.90%	5.20%		2.80%
Liability for Future Policy Benefit, Weighted-Average Duration		18 years 1 month 6 days	17 years 9 months 18 days		15 years 9 months 18 days
Individual Disability | Unum US
Liability for Future Policy Benefit, Expected Net Premium [Roll Forward]
Liability for Future Policy Benefit, Expected Net Premium, before Reinsurance, after Discount Rate Change, balance beginning of year		$ 1,202.9	$ 1,494.3		$ 1,514.2
Liability for Future Policy Benefit, Expected Net Premium, Original Discount Rate, before Cash Flow and Reinsurance, balance beginning of year		1,228.1	1,279.6		1,208.8
Liability for Future Policy Benefit, Expected Net Premium, Cumulative Increase (Decrease) from Cash Flow Change			5		(73.7)			(18.9)
Liability for Future Policy Benefit, Expected Net Premium, Cumulative Increase (Decrease) of Actual Variance from Expected Experience			(10.4)		(25.2)			(10.4)
Liability for Future Policy Benefit, Expected Net Premium, Original Discount Rate, before Reinsurance, after Cash Flow Change			1,222.7		1,180.7			1,179.5
Liability for Future Policy Benefit, Expected Net Premium, Issuance		197.9	168.6		211.3
Liability for Future Policy Benefit, Expected Net Premium, Interest Income		48.2	49.8		57.9
Liability for Future Policy Benefit, Expected Net Premium, Net Premium Collected		(174.4)	(171)		(169.1)
Liability for Future Policy Benefit, Expected Net Premium, Original Discount Rate, before Cash Flow and Reinsurance, balance end of period		1,294.4	1,228.1		1,279.6
AOCI, Liability for Future Policy Benefit, Expected Net Premium, before Tax		2.3	(25.2)		214.7
Liability for Future Policy Benefit, Expected Net Premium, before Reinsurance, after Discount Rate Change, balance end of period		1,296.7	1,202.9		1,494.3
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Liability for Future Policy Benefit, Expected Future Policy Benefit, before Reinsurance, after Discount Rate Change, balance beginning of year		3,192.8	4,017.3		4,226.9
Liability for Future Policy Benefit, Expected Future Policy Benefit, Original Discount Rate, before Cash Flow and Reinsurance, balance at beginning of year		3,244.5	3,253.3		3,197.6
Liability for Future Policy Benefit, Expected Future Policy Benefit, Cumulative Increase (Decrease) from Cash Flow Change			7.9		(53.4)			(22.9)
Liability for Future Policy Benefit, Expected Future Policy Benefit, Cumulative Increase (Decrease) of Actual Variance from Expected Experience			(45.3)		(36)			(42.3)
Liability for Future Policy Benefit, Expected Future Benefit, Original Discount Rate, before Reinsurance, after Cash Flow Change			3,207.1		3,163.9			3,132.4
Liability for Future Policy Benefit, Expected Future Policy Benefit, Issuance	[2]	215.3	181.4		222.5
Liability for Future Policy Benefit, Expected Future Policy Benefit, Interest Expense		164.7	155.3		158.5
Liability for Future Policy Benefit, Expected Future Policy Benefit, Benefit Payment		(273.2)	(256.1)		(260.1)
Liability for Future Policy Benefit, Expected Future Policy Benefit, Original Discount Rate, before Cash Flow and Reinsurance, balance at end of period		3,313.9	3,244.5		3,253.3
AOCI, Liability for Future Policy Benefit, Expected Future Policy Benefit, before Tax		34.7	(51.7)		764
Liability for Future Policy Benefit, Expected Future Policy Benefit, before Reinsurance, after Discount Rate Change, balance end of period		3,348.6	3,192.8		4,017.3
Liability for Future Policy Benefit, before Reinsurance, before Other		2,051.9	1,989.9		2,523
Liability for Future Policy Benefits, Other Contracts		27.8	24.7		59
Liability for Future Policy Benefit, before Reinsurance, after Other		2,079.7	2,014.6		2,582	2,767.7
Liability for Future Policy Benefit, Reinsurance Recoverable, after Allowance		156.7	193.6		231.9	260.6
Liability for Future Policy Benefit, after Reinsurance		1,923	1,821		2,350.1	2,507.1
Gross premiums or assessments		636.6	591.5		580.1
interest accretion		116.5	105.5		100.6
Liability for Future Policy Benefit, Expected Future Policy Benefit, Undiscounted, before Reinsurance		5,313.7	5,168.2		5,210.6
Liability for Future Policy Benefit, Expected Future Gross Premium, Undiscounted, before Reinsurance		5,724.8	5,525.1		5,597.3
Liability for Future Policy Benefit, Expected Future Gross Premium, Discounted, before Reinsurance		$ 4,112.9	$ 3,962.1		$ 3,958.8
Liability for Future Policy Benefit, Weighted-Average Interest Accretion Rate		5.10%	5.10%		5%
Liability for Future Policy Benefit, Current Weighted-Average Discount Rate		4.80%	5.10%		2.40%
Liability for Future Policy Benefit, Weighted-Average Duration		9 years 7 months 6 days	9 years 4 months 24 days		9 years 6 months
Long-term Care | Closed Block
Liability for Future Policy Benefit, Expected Net Premium [Roll Forward]
Liability for Future Policy Benefit, Expected Net Premium, before Reinsurance, after Discount Rate Change, balance beginning of year		$ 6,412.6	$ 8,404.7		$ 9,358.8
Liability for Future Policy Benefit, Expected Net Premium, Original Discount Rate, before Cash Flow and Reinsurance, balance beginning of year		6,236.1	6,457.3		6,782.7
Liability for Future Policy Benefit, Expected Net Premium, Cumulative Increase (Decrease) from Cash Flow Change			1,641.3		27.8			28.5
Liability for Future Policy Benefit, Expected Net Premium, Cumulative Increase (Decrease) of Actual Variance from Expected Experience			44.1		(33.5)			(149.3)
Liability for Future Policy Benefit, Expected Net Premium, Original Discount Rate, before Reinsurance, after Cash Flow Change			7,921.5		6,451.6			6,661.9
Liability for Future Policy Benefit, Expected Net Premium, Interest Income		374.7	349		370.6
Liability for Future Policy Benefit, Expected Net Premium, Net Premium Collected		(592.6)	(564.5)		(575.2)
Liability for Future Policy Benefit, Expected Net Premium, Original Discount Rate, before Cash Flow and Reinsurance, balance end of period		7,703.6	6,236.1		6,457.3
AOCI, Liability for Future Policy Benefit, Expected Net Premium, before Tax		419.9	176.5		1,947.4
Liability for Future Policy Benefit, Expected Net Premium, before Reinsurance, after Discount Rate Change, balance end of period		8,123.5	6,412.6		8,404.7
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Liability for Future Policy Benefit, Expected Future Policy Benefit, before Reinsurance, after Discount Rate Change, balance beginning of year		21,199.9	30,089.6		32,047.2
Liability for Future Policy Benefit, Expected Future Policy Benefit, Original Discount Rate, before Cash Flow and Reinsurance, balance at beginning of year		20,221.6	19,870.8		19,549.7
Liability for Future Policy Benefit, Expected Future Policy Benefit, Cumulative Increase (Decrease) from Cash Flow Change			2,009.4		24.9			52.9
Liability for Future Policy Benefit, Expected Future Policy Benefit, Cumulative Increase (Decrease) of Actual Variance from Expected Experience			113.1		(36.2)			(170.8)
Liability for Future Policy Benefit, Expected Future Benefit, Original Discount Rate, before Reinsurance, after Cash Flow Change			22,344.1		19,859.5			19,431.8
Liability for Future Policy Benefit, Expected Future Policy Benefit, Issuance	[6]	0	0		0
Liability for Future Policy Benefit, Expected Future Policy Benefit, Interest Expense		1,151.4	1,105.1		1,111.6
Liability for Future Policy Benefit, Expected Future Policy Benefit, Benefit Payment		(846.2)	(743)		(672.6)
Liability for Future Policy Benefit, Expected Future Policy Benefit, Original Discount Rate, before Cash Flow and Reinsurance, balance at end of period		22,649.3	20,221.6		19,870.8
AOCI, Liability for Future Policy Benefit, Expected Future Policy Benefit, before Tax		2,048.4	978.3		10,218.8
Liability for Future Policy Benefit, Expected Future Policy Benefit, before Reinsurance, after Discount Rate Change, balance end of period		24,697.7	21,199.9		30,089.6
Liability for Future Policy Benefit, before Reinsurance, before Other		16,574.2	14,787.3		21,684.9
Liability for Future Policy Benefits, Other Contracts	[7]	23.1	24.3		29.8
Liability for Future Policy Benefit, before Reinsurance, after Other		16,597.3	14,811.6		21,714.7	22,740.9
Liability for Future Policy Benefit, Reinsurance Recoverable, after Allowance		4.5	5.7		7.4	44.4
Liability for Future Policy Benefit, after Reinsurance		16,592.8	14,805.9		21,707.3	22,696.5
Gross premiums or assessments		696.1	697.5		705
interest accretion		776.7	756.1		741
Liability for Future Policy Benefit, Expected Future Policy Benefit, Undiscounted, before Reinsurance		61,447.7	52,544		53,395.1
Liability for Future Policy Benefit, Expected Future Gross Premium, Undiscounted, before Reinsurance		14,486.4	12,629.9		13,159
Liability for Future Policy Benefit, Expected Future Gross Premium, Discounted, before Reinsurance		$ 8,241.7	$ 7,333.5		$ 7,518.9
Liability for Future Policy Benefit, Weighted-Average Interest Accretion Rate		5.60%	5.50%		5.60%
Liability for Future Policy Benefit, Current Weighted-Average Discount Rate		5%	5.20%		2.80%
Liability for Future Policy Benefit, Weighted-Average Duration		16 years 4 months 24 days	15 years 6 months		16 years 3 months 18 days
Other Insurance Product Line | Closed Block
Liability for Future Policy Benefit, Expected Net Premium [Roll Forward]
Liability for Future Policy Benefit, Expected Net Premium, before Reinsurance, after Discount Rate Change, balance beginning of year		$ 0	$ 0		$ 0
Liability for Future Policy Benefit, Expected Net Premium, Original Discount Rate, before Cash Flow and Reinsurance, balance beginning of year		0	0		0
Liability for Future Policy Benefit, Expected Net Premium, Cumulative Increase (Decrease) from Cash Flow Change			0		0			0
Liability for Future Policy Benefit, Expected Net Premium, Cumulative Increase (Decrease) of Actual Variance from Expected Experience			0		0			0
Liability for Future Policy Benefit, Expected Net Premium, Original Discount Rate, before Reinsurance, after Cash Flow Change			0		0			0
Liability for Future Policy Benefit, Expected Net Premium, Interest Income		0	0		0
Liability for Future Policy Benefit, Expected Net Premium, Net Premium Collected		0	0		0
Liability for Future Policy Benefit, Expected Net Premium, Original Discount Rate, before Cash Flow and Reinsurance, balance end of period		0	0		0
AOCI, Liability for Future Policy Benefit, Expected Net Premium, before Tax		0	0		0
Liability for Future Policy Benefit, Expected Net Premium, before Reinsurance, after Discount Rate Change, balance end of period		0	0		0
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Liability for Future Policy Benefit, Expected Future Policy Benefit, before Reinsurance, after Discount Rate Change, balance beginning of year		8,218.8	10,414.4		11,591.9
Liability for Future Policy Benefit, Expected Future Policy Benefit, Original Discount Rate, before Cash Flow and Reinsurance, balance at beginning of year		8,630.7	8,949.4		9,514.6
Liability for Future Policy Benefit, Expected Future Policy Benefit, Cumulative Increase (Decrease) from Cash Flow Change			0		216.9			0
Liability for Future Policy Benefit, Expected Future Policy Benefit, Cumulative Increase (Decrease) of Actual Variance from Expected Experience			4		30.7			18.3
Liability for Future Policy Benefit, Expected Future Benefit, Original Discount Rate, before Reinsurance, after Cash Flow Change			8,634.7		9,197			9,532.9
Liability for Future Policy Benefit, Expected Future Policy Benefit, Issuance	[6]	123.4	154.5		197.3
Liability for Future Policy Benefit, Expected Future Policy Benefit, Interest Expense		358.9	372.8		397.2
Liability for Future Policy Benefit, Expected Future Policy Benefit, Benefit Payment		(1,022.4)	(1,093.6)		(1,178)
Liability for Future Policy Benefit, Expected Future Policy Benefit, Original Discount Rate, before Cash Flow and Reinsurance, balance at end of period		8,094.6	8,630.7		8,949.4
AOCI, Liability for Future Policy Benefit, Expected Future Policy Benefit, before Tax		(214.6)	(411.9)		1,465
Liability for Future Policy Benefit, Expected Future Policy Benefit, before Reinsurance, after Discount Rate Change, balance end of period		7,880	8,218.8		10,414.4
Liability for Future Policy Benefit, before Reinsurance, before Other		7,880	8,218.8		10,414.4
Liability for Future Policy Benefits, Other Contracts	[7]	1,638.1	1,737		2,191.8
Liability for Future Policy Benefit, before Reinsurance, after Other		9,518.1	9,955.8		12,606.2	14,251.1
Liability for Future Policy Benefit, Reinsurance Recoverable, after Allowance		7,462.4	7,799.8		9,904.7	9,957
Liability for Future Policy Benefit, after Reinsurance		2,055.7	2,156		2,701.5	4,294.1
Gross premiums or assessments		223.8	250		294.9
interest accretion		358.9	372.8		397.2
Liability for Future Policy Benefit, Expected Future Policy Benefit, Undiscounted, before Reinsurance		11,893.7	12,749		13,138.4
Liability for Future Policy Benefit, Expected Future Gross Premium, Undiscounted, before Reinsurance		0	0		0
Liability for Future Policy Benefit, Expected Future Gross Premium, Discounted, before Reinsurance		$ 0	$ 0		$ 0
Liability for Future Policy Benefit, Weighted-Average Interest Accretion Rate		4.60%	4.60%		4.60%
Liability for Future Policy Benefit, Current Weighted-Average Discount Rate		4.90%	5.10%		2.50%
Liability for Future Policy Benefit, Weighted-Average Duration		7 years 3 months 18 days	7 years 4 months 24 days		7 years 3 months 18 days
Operating Segments
Liability for Future Policy Benefit, Expected Net Premium [Roll Forward]
Liability for Future Policy Benefit, Expected Net Premium, before Reinsurance, after Discount Rate Change, balance beginning of year		$ 12,426.2	$ 15,881.3		$ 17,095.9
Liability for Future Policy Benefit, Expected Net Premium, Original Discount Rate, before Cash Flow and Reinsurance, balance beginning of year		12,695.3	13,186.2		13,623.5
Liability for Future Policy Benefit, Expected Net Premium, Cumulative Increase (Decrease) from Cash Flow Change			1,499.2		(101.9)			(177.1)
Liability for Future Policy Benefit, Expected Net Premium, Cumulative Increase (Decrease) of Actual Variance from Expected Experience			(82.5)		(269.6)			(328.3)
Liability for Future Policy Benefit, Expected Net Premium, Original Discount Rate, before Reinsurance, after Cash Flow Change			14,112		12,814.7			13,118.1
Liability for Future Policy Benefit, Expected Net Premium, Issuance		1,054.9	877.5		1,083.9
Liability for Future Policy Benefit, Expected Net Premium, Interest Income		584	566		631.9
Liability for Future Policy Benefit, Expected Net Premium, Net Premium Collected		(1,537.4)	(1,542.3)		(1,627.4)
Liability for Future Policy Benefit, Expected Net Premium, Increase (Decrease) for Other Change		29.7	(20.6)		(20.3)
Liability for Future Policy Benefit, Expected Net Premium, Original Discount Rate, before Cash Flow and Reinsurance, balance end of period		14,243.2	12,695.3		13,186.2
AOCI, Liability for Future Policy Benefit, Expected Net Premium, before Tax		174.6	(269.1)		2,695.1
Liability for Future Policy Benefit, Expected Net Premium, before Reinsurance, after Discount Rate Change, balance end of period		14,417.8	12,426.2		15,881.3
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Liability for Future Policy Benefit, Expected Future Policy Benefit, before Reinsurance, after Discount Rate Change, balance beginning of year		48,929.4	65,305		69,530.5
Liability for Future Policy Benefit, Expected Future Policy Benefit, Original Discount Rate, before Cash Flow and Reinsurance, balance at beginning of year		49,689	50,397.2		50,752.4
Liability for Future Policy Benefit, Expected Future Policy Benefit, Cumulative Increase (Decrease) from Cash Flow Change			1,702		(92.4)			(379.9)
Liability for Future Policy Benefit, Expected Future Policy Benefit, Cumulative Increase (Decrease) of Actual Variance from Expected Experience			(310.8)		(535.1)			(635.9)
Liability for Future Policy Benefit, Expected Future Benefit, Original Discount Rate, before Reinsurance, after Cash Flow Change			51,080.2		49,769.7			$ 49,736.6
Liability for Future Policy Benefit, Expected Future Policy Benefit, Issuance	[8]	3,072.2	3,194.5		3,675
Liability for Future Policy Benefit, Expected Future Policy Benefit, Interest Expense		2,227.2	2,236.2		2,359.6
Liability for Future Policy Benefit, Expected Future Policy Benefit, Benefit Payment		(5,236.1)	(5,231)		(5,315.7)
Liability for Future Policy Benefit, Expected Future Policy Benefit, Increase (Decrease) for Other Change		162.2	(280.4)		(58.3)
Liability for Future Policy Benefit, Expected Future Policy Benefit, Original Discount Rate, before Cash Flow and Reinsurance, balance at end of period		51,305.7	49,689		50,397.2
AOCI, Liability for Future Policy Benefit, Expected Future Policy Benefit, before Tax		1,117.9	(759.6)		14,907.8
Liability for Future Policy Benefit, Expected Future Policy Benefit, before Reinsurance, after Discount Rate Change, balance end of period		52,423.6	48,929.4		65,305
Liability for Future Policy Benefit, before Reinsurance, before Other		38,005.8	36,503.2		49,423.7
Liability for Future Policy Benefits, Other Contracts		1,753.3	1,854.5		2,355.9
Liability for Future Policy Benefit, before Reinsurance, after Other		39,759.1	38,357.7		51,779.6	55,585.4
Liability for Future Policy Benefit, Reinsurance Recoverable, after Allowance		7,756.1	8,128.2		10,348.2	10,496	[3]
Liability for Future Policy Benefit, after Reinsurance		32,003	30,229.5		41,431.4	$ 45,089.4
Gross premiums or assessments		9,690.7	9,391.8		9,263.4
interest accretion		1,643.2	1,670.2		1,727.7
Liability for Future Policy Benefit, Expected Future Policy Benefit, Undiscounted, before Reinsurance		105,325.8	97,060.7		98,574.9
Liability for Future Policy Benefit, Expected Future Gross Premium, Undiscounted, before Reinsurance		38,761.5	35,299.8		35,296
Liability for Future Policy Benefit, Expected Future Gross Premium, Discounted, before Reinsurance		$ 25,552.9	$ 23,827.2		$ 23,821.7
Liability for Future Policy Benefit, Weighted-Average Interest Accretion Rate		4.80%	4.80%		4.80%
Liability for Future Policy Benefit, Current Weighted-Average Discount Rate		4.80%	5%		2.50%
Liability for Future Policy Benefit, Weighted-Average Duration		11 years 6 months	10 years 10 months 24 days		10 years 10 months 24 days
Future Policy Benefits		$ 40,009.4	$ 38,577.1		$ 51,991.6
[1] 2 We previously reported policy and contract benefits and reserves for future policy and contract benefits liabilities in our consolidated balance sheet as of December 31, 2022 of $1,839.8 million and $42,330.2 million, respectively, resulting in total policyholder liabilities of $44,170.0 million. These balances were reclassified into new line items, future policy benefits and policyholders' account balances, which would have reported balances of $38,443.2 million and $5,726.8 million, respectively, as of December 31, 2022, resulting in total policyholder liabilities of $44,170.0 million under the historical accounting method. 1 Issuances include new policy issuances for most product lines. Issuances for Unum US group disability and Unum US group life and AD&D represents new claim incurrals. 5 These amounts represent the portion of reinsurance recoverable related to the liability for future policy benefits. These amounts include the adjustments for the removal of shadow adjustments and for the effect of change in discount rate assumptions for the liability for future policy benefits ceded to third party reinsurers. 1 Unum US excludes dental & vision and medical stop-loss product lines and Closed Block excludes our participating fund account, which represents policies issued by one of our subsidiaries prior to its 1986 conversion from a mutual stock life insurance company. The liabilities associated with these products are included within Other products. 1 Issuances for Unum International primarily represent new claim incurrals. 1 Issuances for Closed Block - All Other represents new claim incurrals. 2 Other for Closed Block - All Other primarily includes our closed block group pension products and certain of our ceded closed block individual life products. 1 Issuances include new policy issuances for most product lines. For our Unum US group disability, Unum US group life and AD&D and Closed Block - All Other product lines and certain of our Unum International product lines, this line represents new claim incurrals.

Liability for Future Policy B_2

Liability for Future Policy Benefit, Activity - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($)
Long-term Care | Closed Block
Liability for Future Policy Benefit, Activity [Line Items]
Liability for Future Policy Benefit, Adverse Development, Expense	$ (226.5)

Policyholders' Account Balances

Policyholders' Account Balances (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023		Dec. 31, 2022		Dec. 31, 2021
Policyholder Account Balance [Roll Forward]
Policyholders' Account Balances	$ 5,667.7		$ 5,740.2	[1]
Operating Segments
Policyholder Account Balance [Roll Forward]
Policyholder Account Balance, before Reserves in excess of Account Balance, beginning of year	5,598.6		5,679.6		$ 5,678.5
Policyholder Account Balance, Premium Received	175.1		187.6		204.5
Policyholder Account Balance, Policy Charge	(242.3)	[2]	(248)	[2]	(252.9)
Policyholder Account Balance, Surrender and Withdrawal	(88.9)		(90.4)		(89.5)
Policyholder Account Balance, Benefit Payment	(233.1)		(311.5)		(254)
Policyholder Account Balance, Interest Expense	378.5		369.2		373.1
Policyholder Account Balance, Increase (Decrease) from Other Change	(73.7)		12.1		19.9
Policyholder Account Balance, before Reserves in excess of Account Balance, end of period	5,514.2		5,598.6		5,679.6
Policyholder Account Balance, Reserves in excess of Account Balance	153.5		141.6		135.2
Policyholders' Account Balances	5,667.7		5,740.2		5,814.8
Policyholder Account Balance, Reinsurance recoverable	4,120.7		4,192.7		4,264
Policyholder Account Balance, After reinsurance recoverable	$ 1,547		$ 1,547.5		$ 1,550.8
Policyholder Account Balance, Weighted Average Crediting Rate	7%		6.70%		6.80%
Policyholder Account Balance, Net Amount at Risk	$ 15,080	[3]	$ 16,178.1	[3]	$ 17,408.7
Policyholder Account Balance, Cash Surrender Value	5,442.7		5,430.1		5,504.1
Colonial Life
Policyholder Account Balance [Roll Forward]
Policyholder Account Balance, before Reserves in excess of Account Balance, beginning of year	852.4		849.2		843.8
Policyholder Account Balance, Premium Received	84.9		90.9		97.5
Policyholder Account Balance, Policy Charge	(74.7)	[2]	(78)	[2]	(82.4)
Policyholder Account Balance, Surrender and Withdrawal	(36.8)		(36.2)		(35.7)
Policyholder Account Balance, Benefit Payment	(7.2)		(8)		(8.5)
Policyholder Account Balance, Interest Expense	34.2		34.2		34
Policyholder Account Balance, Increase (Decrease) from Other Change	0.1		0.3		0.5
Policyholder Account Balance, before Reserves in excess of Account Balance, end of period	852.9		852.4		849.2
Policyholder Account Balance, Reserves in excess of Account Balance	16.9		16.7		21.5
Policyholders' Account Balances	869.8		869.1		870.7
Policyholder Account Balance, Reinsurance recoverable	0		0.2		0.3
Policyholder Account Balance, After reinsurance recoverable	$ 869.8		$ 868.9		$ 870.4
Policyholder Account Balance, Weighted Average Crediting Rate	4.10%		4.10%		4.10%
Policyholder Account Balance, Net Amount at Risk	$ 8,760.1	[3]	$ 9,338.5	[3]	$ 10,000.6
Policyholder Account Balance, Cash Surrender Value	813.5		800.9		784.6
Voluntary Benefits | Unum US
Policyholder Account Balance [Roll Forward]
Policyholder Account Balance, before Reserves in excess of Account Balance, beginning of year	586.8		598.7		616.7
Policyholder Account Balance, Premium Received	58.5		64.5		69.6
Policyholder Account Balance, Policy Charge	(60.4)	[2]	(64.5)	[2]	(69.3)
Policyholder Account Balance, Surrender and Withdrawal	(33.3)		(32.9)		(39.5)
Policyholder Account Balance, Benefit Payment	(9.7)		(10.7)		(11.4)
Policyholder Account Balance, Interest Expense	22.2		23.5		23.7
Policyholder Account Balance, Increase (Decrease) from Other Change	14.5		8.2		8.9
Policyholder Account Balance, before Reserves in excess of Account Balance, end of period	578.6		586.8		598.7
Policyholder Account Balance, Reserves in excess of Account Balance	99.5		92.9		82.9
Policyholders' Account Balances	678.1		679.7		681.6
Policyholder Account Balance, Reinsurance recoverable	0.9		1.1		1.2
Policyholder Account Balance, After reinsurance recoverable	$ 677.2		$ 678.6		$ 680.4
Policyholder Account Balance, Weighted Average Crediting Rate	3.90%		4%		3.90%
Policyholder Account Balance, Net Amount at Risk	$ 4,495.6	[3]	$ 4,908	[3]	$ 5,356.1
Policyholder Account Balance, Cash Surrender Value	566.9		583.3		584.8
Other Insurance Product Line | Closed Block
Policyholder Account Balance [Roll Forward]
Policyholder Account Balance, before Reserves in excess of Account Balance, beginning of year	4,159.4		4,231.7		4,218
Policyholder Account Balance, Premium Received	31.7		32.2		37.4
Policyholder Account Balance, Policy Charge	(107.2)	[2]	(105.5)	[2]	(101.2)
Policyholder Account Balance, Surrender and Withdrawal	(18.8)		(21.3)		(14.3)
Policyholder Account Balance, Benefit Payment	(216.2)		(292.8)		(234.1)
Policyholder Account Balance, Interest Expense	322.1		311.5		315.4
Policyholder Account Balance, Increase (Decrease) from Other Change	(88.3)		3.6		10.5
Policyholder Account Balance, before Reserves in excess of Account Balance, end of period	4,082.7		4,159.4		4,231.7
Policyholder Account Balance, Reserves in excess of Account Balance	37.1		32		30.8
Policyholders' Account Balances	4,119.8		4,191.4		4,262.5
Policyholder Account Balance, Reinsurance recoverable	4,119.8		4,191.4		4,262.5
Policyholder Account Balance, After reinsurance recoverable	$ 0		$ 0		$ 0
Policyholder Account Balance, Weighted Average Crediting Rate	8%		7.60%		7.80%
Policyholder Account Balance, Net Amount at Risk	$ 1,824.3	[3]	$ 1,931.6	[3]	$ 2,052
Policyholder Account Balance, Cash Surrender Value	$ 4,062.3		$ 4,045.9		$ 4,134.7
[1] 2 We previously reported policy and contract benefits and reserves for future policy and contract benefits liabilities in our consolidated balance sheet as of December 31, 2022 of $1,839.8 million and $42,330.2 million, respectively, resulting in total policyholder liabilities of $44,170.0 million. These balances were reclassified into new line items, future policy benefits and policyholders' account balances, which would have reported balances of $38,443.2 million and $5,726.8 million, respectively, as of December 31, 2022, resulting in total policyholder liabilities of $44,170.0 million under the historical accounting method. 1 Contracts included in the policyholder account balances are generally charged a premium and/or monthly assessments on the basis of the account balance. 2 For those guarantees of benefits that are payable in the event of death, the net amount at risk is generally defined as the current guaranteed minimum death benefit in excess of the current account balance at the balance sheet date.

Policyholder Account Balance, G

Policyholder Account Balance, Guaranteed Minimum Crediting (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Operating Segments
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	$ 5,514.2	$ 5,598.6	$ 5,679.6	$ 5,678.5
Colonial Life
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	852.9	852.4	849.2	843.8
Voluntary Benefits | Unum US
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	578.6	586.8	598.7	616.7
Other Insurance Product Line | Closed Block
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	4,082.7	4,159.4	4,231.7	$ 4,218
Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0300 to 0399 | Voluntary Benefits | Unum US
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	$ 91.9	$ 94.4	$ 98
Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0300 to 0399 | Minimum | Voluntary Benefits | Unum US
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, Guaranteed Minimum Credit Rating	3%	3%	3%
Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0300 to 0399 | Maximum | Voluntary Benefits | Unum US
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, Guaranteed Minimum Credit Rating	3.99%	3.99%	3.99%
Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0400 and 0499 | Voluntary Benefits | Unum US
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	$ 454.9	$ 458.4	$ 465.8
Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0400 and 0499 | Minimum | Voluntary Benefits | Unum US
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, Guaranteed Minimum Credit Rating	4%	4%	4%
Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0400 and 0499 | Maximum | Voluntary Benefits | Unum US
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, Guaranteed Minimum Credit Rating	4.99%	4.99%	4.99%
Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0500 and 0600 | Voluntary Benefits | Unum US
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	$ 31.8	$ 34	$ 34.9
Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0500 and 0600 | Minimum | Voluntary Benefits | Unum US
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, Guaranteed Minimum Credit Rating	5%	5%	5%
Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0500 and 0600 | Maximum | Voluntary Benefits | Unum US
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, Guaranteed Minimum Credit Rating	6%	6%	6%
Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0400 and 0500 | Colonial Life
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	$ 852.9	$ 852.4	$ 849.2
Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0400 and 0500 | Minimum | Colonial Life
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, Guaranteed Minimum Credit Rating	4%	4%	4%
Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0400 and 0500 | Maximum | Colonial Life
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, Guaranteed Minimum Credit Rating	5%	5%	5%
Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0300 and 0599 | Other Insurance Product Line | Closed Block
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	$ 1,639.3	$ 1,697.2	$ 1,852.7
Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0300 and 0599 | Minimum | Other Insurance Product Line | Closed Block
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, Guaranteed Minimum Credit Rating	3%	3%	3%
Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0300 and 0599 | Maximum | Other Insurance Product Line | Closed Block
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, Guaranteed Minimum Credit Rating	5.99%	5.99%	5.99%
Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0600 and 0899 | Other Insurance Product Line | Closed Block
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	$ 32.3	$ 31.4	$ 29.6
Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0600 and 0899 | Minimum | Other Insurance Product Line | Closed Block
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, Guaranteed Minimum Credit Rating	6%	6%	6%
Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0600 and 0899 | Maximum | Other Insurance Product Line | Closed Block
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, Guaranteed Minimum Credit Rating	8.99%	8.99%	8.99%
Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0900 and 1199 | Other Insurance Product Line | Closed Block
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	$ 2,354.9	$ 2,378.2	$ 2,300.4
Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0900 and 1199 | Minimum | Other Insurance Product Line | Closed Block
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, Guaranteed Minimum Credit Rating	9%	9%	9%
Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0900 and 1199 | Maximum | Other Insurance Product Line | Closed Block
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, Guaranteed Minimum Credit Rating	11.99%	11.99%	11.99%
Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 1200 and 1500 | Other Insurance Product Line | Closed Block
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	$ 56.2	$ 52.6	$ 49
Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 1200 and 1500 | Minimum | Other Insurance Product Line | Closed Block
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, Guaranteed Minimum Credit Rating	12%	12%	12%
Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 1200 and 1500 | Maximum | Other Insurance Product Line | Closed Block
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, Guaranteed Minimum Credit Rating	15%	15%	15%
Policyholder Account Balance, at Guaranteed Minimum Crediting Rate | Operating Segments
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	$ 2,044	$ 5,373.2	$ 5,460.2
Policyholder Account Balance, at Guaranteed Minimum Crediting Rate | Voluntary Benefits | Unum US
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	350.8	402.9	421.7
Policyholder Account Balance, at Guaranteed Minimum Crediting Rate | Other Insurance Product Line | Closed Block
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	846.5	4,123.9	4,195.1
Policyholder Account Balance, at Guaranteed Minimum Crediting Rate | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0300 to 0399 | Voluntary Benefits | Unum US
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	91.9	94.4	98
Policyholder Account Balance, at Guaranteed Minimum Crediting Rate | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0400 and 0499 | Voluntary Benefits | Unum US
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	227.1	274.5	288.8
Policyholder Account Balance, at Guaranteed Minimum Crediting Rate | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0500 and 0600 | Voluntary Benefits | Unum US
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	31.8	34	34.9
Policyholder Account Balance, at Guaranteed Minimum Crediting Rate | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0400 and 0500 | Colonial Life
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	846.7	846.4	843.4
Policyholder Account Balance, at Guaranteed Minimum Crediting Rate | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0300 and 0599 | Other Insurance Product Line | Closed Block
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	526.8	1,661.7	1,816.1
Policyholder Account Balance, at Guaranteed Minimum Crediting Rate | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0600 and 0899 | Other Insurance Product Line | Closed Block
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	1.3	31.4	29.6
Policyholder Account Balance, at Guaranteed Minimum Crediting Rate | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0900 and 1199 | Other Insurance Product Line | Closed Block
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	318.4	2,378.2	2,300.4
Policyholder Account Balance, at Guaranteed Minimum Crediting Rate | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 1200 and 1500 | Other Insurance Product Line | Closed Block
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	0	52.6	49
Policyholder Account Balance, above Guaranteed Minimum Crediting Rate, Range from 0001 to 0050 | Operating Segments
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	3,401.8	219	213
Policyholder Account Balance, above Guaranteed Minimum Crediting Rate, Range from 0001 to 0050 | Voluntary Benefits | Unum US
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	190.1	183.9	177
Policyholder Account Balance, above Guaranteed Minimum Crediting Rate, Range from 0001 to 0050 | Other Insurance Product Line | Closed Block
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	3,205.5	29.1	30.2
Policyholder Account Balance, above Guaranteed Minimum Crediting Rate, Range from 0001 to 0050 | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0300 to 0399 | Voluntary Benefits | Unum US
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	0	0	0
Policyholder Account Balance, above Guaranteed Minimum Crediting Rate, Range from 0001 to 0050 | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0400 and 0499 | Voluntary Benefits | Unum US
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	190.1	183.9	177
Policyholder Account Balance, above Guaranteed Minimum Crediting Rate, Range from 0001 to 0050 | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0500 and 0600 | Voluntary Benefits | Unum US
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	0	0	0
Policyholder Account Balance, above Guaranteed Minimum Crediting Rate, Range from 0001 to 0050 | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0400 and 0500 | Colonial Life
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	6.2	6	5.8
Policyholder Account Balance, above Guaranteed Minimum Crediting Rate, Range from 0001 to 0050 | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0300 and 0599 | Other Insurance Product Line | Closed Block
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	1,081.8	29.1	30.2
Policyholder Account Balance, above Guaranteed Minimum Crediting Rate, Range from 0001 to 0050 | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0600 and 0899 | Other Insurance Product Line | Closed Block
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	31	0	0
Policyholder Account Balance, above Guaranteed Minimum Crediting Rate, Range from 0001 to 0050 | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0900 and 1199 | Other Insurance Product Line | Closed Block
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	2,036.5	0	0
Policyholder Account Balance, above Guaranteed Minimum Crediting Rate, Range from 0001 to 0050 | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 1200 and 1500 | Other Insurance Product Line | Closed Block
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	56.2	0	0
Policyholder Account Balance, above Guaranteed Minimum Crediting Rate, Range from 0051 to 0150 | Operating Segments
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	68.4	6.4	6.4
Policyholder Account Balance, above Guaranteed Minimum Crediting Rate, Range from 0051 to 0150 | Voluntary Benefits | Unum US
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	37.7	0	0
Policyholder Account Balance, above Guaranteed Minimum Crediting Rate, Range from 0051 to 0150 | Other Insurance Product Line | Closed Block
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	30.7	6.4	6.4
Policyholder Account Balance, above Guaranteed Minimum Crediting Rate, Range from 0051 to 0150 | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0300 to 0399 | Voluntary Benefits | Unum US
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	0	0	0
Policyholder Account Balance, above Guaranteed Minimum Crediting Rate, Range from 0051 to 0150 | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0400 and 0499 | Voluntary Benefits | Unum US
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	37.7	0	0
Policyholder Account Balance, above Guaranteed Minimum Crediting Rate, Range from 0051 to 0150 | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0500 and 0600 | Voluntary Benefits | Unum US
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	0	0	0
Policyholder Account Balance, above Guaranteed Minimum Crediting Rate, Range from 0051 to 0150 | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0400 and 0500 | Colonial Life
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	0	0	0
Policyholder Account Balance, above Guaranteed Minimum Crediting Rate, Range from 0051 to 0150 | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0300 and 0599 | Other Insurance Product Line | Closed Block
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	30.7	6.4	6.4
Policyholder Account Balance, above Guaranteed Minimum Crediting Rate, Range from 0051 to 0150 | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0600 and 0899 | Other Insurance Product Line | Closed Block
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	0	0	0
Policyholder Account Balance, above Guaranteed Minimum Crediting Rate, Range from 0051 to 0150 | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0900 and 1199 | Other Insurance Product Line | Closed Block
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	0	0	0
Policyholder Account Balance, above Guaranteed Minimum Crediting Rate, Range from 0051 to 0150 | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 1200 and 1500 | Other Insurance Product Line | Closed Block
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	0	0	0
Policyholder Account Balance, above Guaranteed Minimum Crediting Rate, Range from 0151 and Greater | Operating Segments
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	0	0	0
Policyholder Account Balance, above Guaranteed Minimum Crediting Rate, Range from 0151 and Greater | Voluntary Benefits | Unum US
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	0	0	0
Policyholder Account Balance, above Guaranteed Minimum Crediting Rate, Range from 0151 and Greater | Other Insurance Product Line | Closed Block
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	0	0	0
Policyholder Account Balance, above Guaranteed Minimum Crediting Rate, Range from 0151 and Greater | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0300 to 0399 | Voluntary Benefits | Unum US
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	0	0	0
Policyholder Account Balance, above Guaranteed Minimum Crediting Rate, Range from 0151 and Greater | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0400 and 0499 | Voluntary Benefits | Unum US
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	0	0	0
Policyholder Account Balance, above Guaranteed Minimum Crediting Rate, Range from 0151 and Greater | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0500 and 0600 | Voluntary Benefits | Unum US
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	0	0	0
Policyholder Account Balance, above Guaranteed Minimum Crediting Rate, Range from 0151 and Greater | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0400 and 0500 | Colonial Life
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	0	0	0
Policyholder Account Balance, above Guaranteed Minimum Crediting Rate, Range from 0151 and Greater | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0300 and 0599 | Other Insurance Product Line | Closed Block
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	0	0	0
Policyholder Account Balance, above Guaranteed Minimum Crediting Rate, Range from 0151 and Greater | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0600 and 0899 | Other Insurance Product Line | Closed Block
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	0	0	0
Policyholder Account Balance, above Guaranteed Minimum Crediting Rate, Range from 0151 and Greater | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0900 and 1199 | Other Insurance Product Line | Closed Block
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	0	0	0
Policyholder Account Balance, above Guaranteed Minimum Crediting Rate, Range from 0151 and Greater | Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 1200 and 1500 | Other Insurance Product Line | Closed Block
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]
Policyholder Account Balance, before Reserves in excess of Account Balance	$ 0	$ 0	$ 0

Deferred Policy Acquisition Cos

Deferred Policy Acquisition Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Movement Analysis of Deferred Policy Acquisition Costs
Deferred Acquisition Costs at Beginning of Year	$ 2,560
Deferred Policy Acquisition Costs, Amortization Expense	(481.4)	$ (421.1)	$ (452.1)
Deferred Acquisition Costs at End of Year	2,714.5	2,560
Operating Segments
Movement Analysis of Deferred Policy Acquisition Costs
Deferred Acquisition Costs at Beginning of Year	2,560	2,427.4	2,357.7
Deferral of Acquisition Costs	632.2	556.9	523.2
Deferred Policy Acquisition Costs, Amortization Expense	(481.4)	(421.1)	(452.1)
Deferred Policy Acquisition Cost, Foreign Currency Translation Adjustment and Other	3.7	(3.2)	(1.4)
Deferred Acquisition Costs at End of Year	2,714.5	2,560	2,427.4
Unum US
Movement Analysis of Deferred Policy Acquisition Costs
Deferred Acquisition Costs at Beginning of Year	1,185.1	1,152.9	1,181
Deferral of Acquisition Costs	314.7	273.1	257.8
Deferred Policy Acquisition Costs, Amortization Expense	(267.6)	(240.9)	(285.9)
Deferred Policy Acquisition Cost, Foreign Currency Translation Adjustment and Other	0	0	0
Deferred Acquisition Costs at End of Year	1,232.2	1,185.1	1,152.9
Unum US | Operating Segments
Movement Analysis of Deferred Policy Acquisition Costs
Deferred Policy Acquisition Costs, Amortization Expense	(267.6)	(240.9)	(285.9)
Unum International
Movement Analysis of Deferred Policy Acquisition Costs
Deferred Acquisition Costs at Beginning of Year	37	36.4	32
Deferral of Acquisition Costs	14.6	12	12.8
Deferred Policy Acquisition Costs, Amortization Expense	(8.4)	(8.2)	(7)
Deferred Policy Acquisition Cost, Foreign Currency Translation Adjustment and Other	3.7	(3.2)	(1.4)
Deferred Acquisition Costs at End of Year	46.9	37	36.4
Unum International | Operating Segments
Movement Analysis of Deferred Policy Acquisition Costs
Deferred Policy Acquisition Costs, Amortization Expense	(8.4)	(8.2)	(7)
Colonial Life
Movement Analysis of Deferred Policy Acquisition Costs
Deferred Acquisition Costs at Beginning of Year	1,337.9	1,238.1	1,144.7
Deferral of Acquisition Costs	302.9	271.8	252.6
Deferred Policy Acquisition Costs, Amortization Expense	(205.4)	(172)	(159.2)
Deferred Policy Acquisition Cost, Foreign Currency Translation Adjustment and Other	0	0	0
Deferred Acquisition Costs at End of Year	1,435.4	1,337.9	1,238.1
Colonial Life | Operating Segments
Movement Analysis of Deferred Policy Acquisition Costs
Deferred Policy Acquisition Costs, Amortization Expense	(205.4)	(172)	(159.2)
Group Disability | Unum US
Movement Analysis of Deferred Policy Acquisition Costs
Deferred Acquisition Costs at Beginning of Year	61	60.9	95.3
Deferral of Acquisition Costs	60.2	53.1	49.8
Deferred Policy Acquisition Costs, Amortization Expense	(57.6)	(53)	(84.2)
Deferred Acquisition Costs at End of Year	63.6	61	60.9
Group Life and AD&D | Unum US
Movement Analysis of Deferred Policy Acquisition Costs
Deferred Acquisition Costs at Beginning of Year	49.3	53.9	76.4
Deferral of Acquisition Costs	38.6	37.3	36.1
Deferred Policy Acquisition Costs, Amortization Expense	(39)	(41.9)	(58.6)
Deferred Acquisition Costs at End of Year	48.9	49.3	53.9
Voluntary Benefits | Unum US
Movement Analysis of Deferred Policy Acquisition Costs
Deferred Acquisition Costs at Beginning of Year	601	588.6	569.7
Deferral of Acquisition Costs	115.8	100	99.4
Deferred Policy Acquisition Costs, Amortization Expense	(106.2)	(87.6)	(80.5)
Deferred Acquisition Costs at End of Year	610.6	601	588.6
Individual Disability | Unum US
Movement Analysis of Deferred Policy Acquisition Costs
Deferred Acquisition Costs at Beginning of Year	464.4	441.8	423.6
Deferral of Acquisition Costs	87.4	72	63.9
Deferred Policy Acquisition Costs, Amortization Expense	(54)	(49.4)	(45.7)
Deferred Acquisition Costs at End of Year	497.8	464.4	441.8
Dental and Vision | Unum US
Movement Analysis of Deferred Policy Acquisition Costs
Deferred Acquisition Costs at Beginning of Year	9.4	7.7	16
Deferral of Acquisition Costs	12.7	10.7	8.6
Deferred Policy Acquisition Costs, Amortization Expense	(10.8)	(9)	(16.9)
Deferred Acquisition Costs at End of Year	$ 11.3	$ 9.4	$ 7.7

Income Tax Expense (Benefit) (D

Income Tax Expense (Benefit) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax [Abstract]
Income Tax Expense	$ 356.3	$ 342.8	$ 279.6
Total Income Tax Expense	381.6	836.7	592
Other Comprehensive Income (Loss), Tax
Change in Net Unrealized Gain on Securities Before Adjustment	300.6	(1,890.8)	(346.9)
OCI, Liability for Future Policy Benefit, Gain (Loss), after Reclassification Adjustment, Tax	(256.5)	2,385.1	622.8
Change in Net Gain on Hedges	(17)	(19.2)	(9.8)
Change in Foreign Currency Translation Adjustment	0.9	(0.1)	4.2
Change in Unrecognized Pension and Postretirement Benefit Costs	$ (2.7)	$ 18.9	$ 42.1

Reconciliation of income tax co

Reconciliation of income tax computed at US Federal tax rates (Detail)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax [Abstract]
Statutory Income Tax	21%	21%	21%
Policyholder Reserves	(0.60%)	(1.70%)	2%
Other Items, Net	1.30%	0.30%	(0.80%)
Effective Tax	21.70%	19.60%	22.20%

Schedule of deferred income tax

Schedule of deferred income tax assets and liabilities (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Income Tax [Abstract]
Deferred Tax Assets, Investments	$ 354.5	$ 664.9
Deferred Tax Asset, Reserves	462.6	116.4
Deferred Tax Asset, Employee Benefits	161.9	158.3
Deferred Tax Asset, Other	35.8	34.4
Deferred Tax Assets, Gross, Total	1,014.8	974
Less: Valuation Allowance	11	10.3
Deferred Tax Assets, Net of Valuation Allowance, Total	1,003.8	963.7
Deferred Tax Liabilities for Deferred Acquisition Cost	175.1	177.7
Deferred Tax Liabilities for Fixed Assets	36.7	48.9
Deferred Tax Liabilities on Cost of Reinsurance	119.7	131.6
Deferred Tax Liability, Other	49.9	44.7
Gross Deferred Tax Liability	381.4	402.9
Deferred Income Tax	$ 622.4	$ 560.8

Schedule of Income subject to d

Schedule of Income subject to domestic and foreign taxation (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax [Abstract]
Income Before Tax, Domestic	$ 1,506.2	$ 1,596.8	$ 1,150.5
Income Before Tax, Foreign	133.9	153.2	110.1
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	1,640.1	1,750	1,260.6
Current Tax Expense (Benefit), Domestic	440.4	306.5	180.7
Current State and Local Tax Expense (Benefit)	(2.5)	12.7	2.6
Current Tax Expense (Benefit), Foreign	14.1	154.3	29.5
Income Tax (Benefit) - Current	452	473.5	212.8
Deferred Tax Expense (Benefit), Federal	(106.2)	42.7	54
Deferred State and Local Income Tax Expense (Benefit)	(1.5)	1.1	(2.2)
Deferred Tax Expense (Benefit), Foreign	12	(174.5)	15
Deferred Income Tax Expense (Benefit)	(95.7)	(130.7)	66.8
Income Tax Expense	$ 356.3	$ 342.8	$ 279.6

Unrecognized tax benefits (Deta

Unrecognized tax benefits (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax [Abstract]
Balance at Beginning of Year	$ 177.4	$ 198.8	$ 219.7
Decreases for Tax Positions Related to Prior Years	(20.7)	(21)	(20.9)
Lapse of the Applicable Statute of Limitations	0	(0.4)	0
Balance at End of Year	156.7	177.4	198.8
Less Tax Attributable to Temporary Items Included Above	(42.4)	(63.5)	(84.7)
Total Unrecognized Tax Benefits that if Recognized Would Affect the Effective Tax Rate	$ 114.3	$ 113.9	$ 114.1

Income Tax Additional Informati

Income Tax Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2018
Federal Income Tax Note
Less Tax Attributable to Temporary Items Included Above	$ (42.4)	$ (63.5)	$ (84.7)
Unrecognized Tax Benefits, Interest on Income Taxes Expense	12.2	7.8	5.5
Unrecognized Tax Benefits, Interest on Income Taxes Accrued	46.2	34	26.2
Valuation Allowance on Deferred Tax Assets	11	10.3
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	0.7	2.4
Income Taxes Paid, Net	446	$ 375	(51)
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			$ (23.6)
State and Local Jurisdiction
Federal Income Tax Note
Operating Loss Carryforwards	$ 183.9

Debt Schedule (Detail)

Debt Schedule (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Debt Instrument
Long-term Debt, Excluding Current Maturities	$ 3,430.4	$ 3,427.8
Debt Instrument, Unamortized Premium (Discount), Net	(2.5)	(2.5)
Debt Issuance Costs, Noncurrent, Net	(30.6)	(33.2)
Long-term Debt	3,430.4	3,429.8
Five-Year Term Loan Facility
Debt Instrument
Line of Credit Facility, Fair Value of Amount Outstanding	350	350
Notes Issued in 1998 with 2028 Maturity Date | Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	335.8	335.8
Notes Payable due 2032 | Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	39.5	39.5
Notes Payable due 2042 | Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	500	500
Notes Payable due 2025 | Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	275	275
Notes Payable due 2029 | Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	400	400
Notes Payable due 2049 | Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	450	450
Notes Payable due 2051 | Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	600	600
Medium Term Notes Payable Due 2028 | Medium-term Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	18.5	18.5
Notes Issued in 1998 with 2038 Maturity Date | Junior Subordinated Debt
Debt Instrument
Long-term Debt, Excluding Current Maturities	189.7	189.7
Notes Payable due 2058 | Junior Subordinated Debt
Debt Instrument
Long-term Debt, Excluding Current Maturities	300	300
Notes Issued 1990 to 1996 | Medium-term Notes
Debt Instrument
Short-term Debt, outstanding principal	$ 0	$ 2

Debt - Additional Information (

Debt - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 1998
Debt Additional Information
Repayments of Principal in 2023	$ 275
Repayments of Principal in 2025	350
Repayments of Principal in 2027	354.3
Repayments of Principal Thereafter	$ 2,479.2
Unum Group Percentage Ownership of Provident Financing Trust	100%
Interest Paid, Including Capitalized Interest, Operating and Investing Activities	$ 183.6	$ 172.9	$ 181.6
Five-year Unsecured Revolving Credit Facility
Debt Additional Information
Letters of Credit Outstanding	0.4
Line of Credit Facility, Maximum Borrowing Capacity	500
Line of Credit Facility, Additional Borrowing Capacity If Requested	200
Five-year Unsecured Revolving Credit Facility | Parent Company
Debt Additional Information
Letters of Credit Outstanding	$ 0
Facility agreement for contingent issuance of senior notes
Debt Additional Information
Line of Credit Facility, Maximum Borrowing Capacity			$ 400
Facility agreement for contingent issuance of senior notes | Parent Company
Debt Additional Information
Line of Credit Facility, Commitment Fee Percentage	2.225%
Debt Instrument, Covenant Description	2.0 billion
Notes Issued in 1998 with 2038 Maturity Date | Junior Subordinated Debt
Debt Additional Information
Stated Interest Rate of Debt				7.405%
Proceeds from Issuance of Senior Long-term Debt				$ 300
Liquidation value per capital security	$ 1,000
7.405% junior subordinated debt securities due 2038
Debt Additional Information
Debt Instrument, Repurchased Face Amount		14
Costs Related to Early Retirement of Debt		$ 1.2
4.500% Senior Notes due 2025
Debt Additional Information
Stated Interest Rate of Debt			4.50%
Costs Related to Early Retirement of Debt			$ 67.3
4.500% Senior Notes due 2025 | Senior Notes
Debt Additional Information
Debt Instrument, Repurchased Face Amount			500
4.125% Senior Notes due 2051 | Senior Notes
Debt Additional Information
Proceeds from Issuance of Debt			$ 600
Stated Interest Rate of Debt			4.125%
4.000% Notes due 2024
Debt Additional Information
Stated Interest Rate of Debt		4%
Debt Instrument, Repurchased Face Amount		$ 350
Costs Related to Early Retirement of Debt		$ 3
Junior Subordinated Debt | Junior Subordinated Notes Payable Due 2038
Debt Additional Information
Stated Interest Rate of Debt				7.405%

Employee Benefit Plans Change i

Employee Benefit Plans Change in Projected Benefit Obligation Amount (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pension Plan | UNITED STATES
Defined Benefit Plan, Change in Benefit Obligation
Benefit Obligation at Beginning of Year	$ 1,585.5	$ 2,207.5
Service Cost	9.2	7.7	$ 9.6
Interest Cost	87.9	67.2	65
Plan Participant Contributions	0	0
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	61	(604.1)
Benefits and Expenses Paid	(168.3)	(92.8)
Change in Foreign Exchange Rates	0	0
Benefit Obligation at End of Year	1,575.3	1,585.5	2,207.5
Defined Benefit Plan, Change in Fair Value of Plan Assets
Fair Value of Plan Assets at Beginning of Year	1,308.3	1,801.7
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	145.6	(410.6)
Employer Contributions to Defined Benefit Plan	10.3	10
Plan Participant Contributions	0	0
Benefits and Expenses Paid	(168.3)	(92.8)
Effect of Foreign Exchange Rates on Plan Assets	0	0
Fair Value of Plan Assets at End of Year	1,295.9	1,308.3	1,801.7
Accumulated Benefit Obligation	1,575.3	1,585.5
Funded Status of Plan	279.4	277.2
Pension Plan | Foreign Plan
Defined Benefit Plan, Change in Benefit Obligation
Benefit Obligation at Beginning of Year	157.9	278.3
Service Cost	0	0	0
Interest Cost	7.7	5	4.2
Plan Participant Contributions	0	0
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	3.8	(92.4)
Benefits and Expenses Paid	(5.7)	(5.4)
Change in Foreign Exchange Rates	8.6	(27.6)
Benefit Obligation at End of Year	172.3	157.9	278.3
Defined Benefit Plan, Change in Fair Value of Plan Assets
Fair Value of Plan Assets at Beginning of Year	140.5	303.7
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	3.1	(128.4)
Employer Contributions to Defined Benefit Plan	0	0
Plan Participant Contributions	0	0
Benefits and Expenses Paid	(5.7)	(5.4)
Effect of Foreign Exchange Rates on Plan Assets	7.5	(29.4)
Fair Value of Plan Assets at End of Year	145.4	140.5	303.7
Accumulated Benefit Obligation	172.3	158
Funded Status of Plan	26.9	17.4
Other Postretirement Benefit Plans
Defined Benefit Plan, Change in Benefit Obligation
Benefit Obligation at Beginning of Year	83.9	110.3
Service Cost	0	0	0
Interest Cost	4.5	3	3
Plan Participant Contributions	0.1	0.1
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	(0.5)	(19.4)
Benefits and Expenses Paid	(9)	(10.1)
Change in Foreign Exchange Rates	0	0
Benefit Obligation at End of Year	79	83.9	110.3
Defined Benefit Plan, Change in Fair Value of Plan Assets
Fair Value of Plan Assets at Beginning of Year	8.5	9
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	0	0.1
Employer Contributions to Defined Benefit Plan	8.6	9.4
Plan Participant Contributions	0.1	0.1
Benefits and Expenses Paid	(9)	(10.1)
Effect of Foreign Exchange Rates on Plan Assets	0	0
Fair Value of Plan Assets at End of Year	8.2	8.5	$ 9
Funded Status of Plan	$ 70.8	$ 75.4

Employee Benefit Plans Amounts

Employee Benefit Plans Amounts Recognized in Balance Sheet (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pension Plan | UNITED STATES
Defined Benefit Plans and Other Postretirement Benefit Plans
Current Pension Liability	$ 9.1	$ 8.8
Noncurrent Pension Liability	270.3	268.4
Funded Status of Plan	279.4	277.2
Net Actuarial Gain (Loss) in Balance Sheet	(510.2)	(517.8)
Prior Service Credit in Balance Sheet	(0.6)	(0.6)
Pension Recognized in Balance Sheet, Gross of Deferred Tax	(510.8)	(518.4)
Pension Deferred Tax Asset in Balance Sheet	211.2	213.5
Pension Recognized in Balance Sheet, Net of Deferred Tax	(299.6)	(304.9)	$ (383.2)
Pension Plan | Foreign Plan
Defined Benefit Plans and Other Postretirement Benefit Plans
Current Pension Liability	0	0
Noncurrent Pension Liability	26.9	17.4
Funded Status of Plan	26.9	17.4
Net Actuarial Gain (Loss) in Balance Sheet	(95)	(83.7)
Prior Service Credit in Balance Sheet	(0.2)	(0.2)
Pension Recognized in Balance Sheet, Gross of Deferred Tax	(95.2)	(83.9)
Pension Deferred Tax Asset in Balance Sheet	22.2	19.5
Pension Recognized in Balance Sheet, Net of Deferred Tax	(73)	(64.4)	(34)
Other Postretirement Benefit Plans
Defined Benefit Plans and Other Postretirement Benefit Plans
Current Pension Liability	0.7	1.1
Noncurrent Pension Liability	70.1	74.3
Funded Status of Plan	70.8	75.4
Net Actuarial Gain (Loss) in Balance Sheet	21.2	31.6
Prior Service Credit in Balance Sheet	2.3	2.5
Pension Recognized in Balance Sheet, Gross of Deferred Tax	23.5	34.1
Pension Deferred Tax Asset in Balance Sheet	3.4	1.1
Pension Recognized in Balance Sheet, Net of Deferred Tax	$ 26.9	$ 35.2	$ 21.2

Employee Benefit Plans Amount_2

Employee Benefit Plans Amounts Recognized in Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pension Plan | UNITED STATES
Defined Benefit Plans and Other Postretirement Benefit Plans
Pension Recognized in Balance Sheet, Net of Deferred Tax, Beginning of Year	$ (304.9)	$ (383.2)
Amortization of Net Actuarial Loss (Gain)	15.2	16.3	$ 21.3
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, before Tax	(7.6)	87.7
Amortization of Prior Service Cost (Credit)	0	0	0
Change in Unrecognized Pension and Postretirement Benefit Costs, Tax Expense	(2.3)	(25.7)
Pension Recognized in Balance Sheet, Net of Deferred Tax, End of Year	(299.6)	(304.9)	(383.2)
Pension Plan | Foreign Plan
Defined Benefit Plans and Other Postretirement Benefit Plans
Pension Recognized in Balance Sheet, Net of Deferred Tax, Beginning of Year	(64.4)	(34)
Amortization of Net Actuarial Loss (Gain)	2.5	0.4	1.3
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, before Tax	(13.8)	(41.2)
Amortization of Prior Service Cost (Credit)	0	0	0
Change in Unrecognized Pension and Postretirement Benefit Costs, Tax Expense	2.7	10.4
Pension Recognized in Balance Sheet, Net of Deferred Tax, End of Year	(73)	(64.4)	(34)
Other Postretirement Benefit Plans
Defined Benefit Plans and Other Postretirement Benefit Plans
Pension Recognized in Balance Sheet, Net of Deferred Tax, Beginning of Year	35.2	21.2
Amortization of Net Actuarial Loss (Gain)	(10.5)	(1)	0
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, before Tax	0.1	19
Amortization of Prior Service Cost (Credit)	(0.2)	(0.2)	(0.2)
Change in Unrecognized Pension and Postretirement Benefit Costs, Tax Expense	2.3	(3.8)
Pension Recognized in Balance Sheet, Net of Deferred Tax, End of Year	$ 26.9	$ 35.2	$ 21.2

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, 2023	Dec. 31, 2022
Equity Funds
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	$ 445.8	$ 463.1
Equity Funds | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	55	57.4
Equity Funds | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	0	0
Equity Funds | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	0	0
Equity Funds | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	390.8	405.7
U.S. Government and Agencies
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	256.7	215.7
U.S. Government and Agencies | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	215.9	194
U.S. Government and Agencies | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	40.8	21.7
U.S. Government and Agencies | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	0	0
U.S. Government and Agencies | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	0	0
Corporate
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	130	129.6
Corporate | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	0	0
Corporate | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	0	0
Corporate | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	0	0
Corporate | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	130	129.6
Foreign Emerging Market Fixed Income Securities
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	27.9	54
Foreign Emerging Market Fixed Income Securities | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	0	0
Foreign Emerging Market Fixed Income Securities | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	0	0
Foreign Emerging Market Fixed Income Securities | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	0	0
Foreign Emerging Market Fixed Income Securities | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	27.9	54
Opportunistic Credits
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	150.6	132.3
Opportunistic Credits | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	0	0
Opportunistic Credits | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	0	0
Opportunistic Credits | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	0	0
Opportunistic Credits | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	150.6	132.3
Real Estate
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	162.8	164.2
Real Estate | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	0	0
Real Estate | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	0	0
Real Estate | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	0	0
Real Estate | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	162.8	164.2
Private Equity Direct Investments
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	68.5	74.5
Private Equity Direct Investments | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	0	0
Private Equity Direct Investments | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	0	0
Private Equity Direct Investments | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	0	0
Private Equity Direct Investments | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	68.5	74.5
Private Equity Funds of Funds
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	40.7	47.6
Private Equity Funds of Funds | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	0	0
Private Equity Funds of Funds | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	0	0
Private Equity Funds of Funds | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	0	0
Private Equity Funds of Funds | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	40.7	47.6
Cash Equivalents
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	16	20.5
Cash Equivalents | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	16	20.5
Cash Equivalents | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	0	0
Cash Equivalents | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	0	0
Cash Equivalents | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	0	0
Total Invested Assets
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	1,299	1,301.5
Total Invested Assets | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	286.9	271.9
Total Invested Assets | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	40.8	21.7
Total Invested Assets | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	0	0
Total Invested Assets | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	$ 971.3	$ 1,007.9

Employee Benefit Plans UK Pensi

Employee Benefit Plans UK Pension Assets, Fair Value Measurement by Input Level (Details) - Pension Plan - Foreign Plan - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Diversified Growth Assets
Defined Benefit Plans and Other Postretirement Benefit Plans
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	$ 34	$ 40.6
Diversified Growth Assets | Fair Value, Inputs, Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	28.1	32.3
Diversified Growth Assets | Fair Value, Inputs, Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	0	0
Diversified Growth Assets | Fair Value, Inputs, Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	0	0
Diversified Growth Assets | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plans and Other Postretirement Benefit Plans
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	5.9	8.3
Fixed Income and Index-linked Securities
Defined Benefit Plans and Other Postretirement Benefit Plans
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	75.3	70.6
Fixed Income and Index-linked Securities | Fair Value, Inputs, Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	75.3	70.6
Fixed Income and Index-linked Securities | Fair Value, Inputs, Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	0	0
Fixed Income and Index-linked Securities | Fair Value, Inputs, Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	0	0
Fixed Income and Index-linked Securities | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plans and Other Postretirement Benefit Plans
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	0	0
Alternative Investments
Defined Benefit Plans and Other Postretirement Benefit Plans
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	34.8	28.1
Alternative Investments | Fair Value, Inputs, Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	0	0
Alternative Investments | Fair Value, Inputs, Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	0	0
Alternative Investments | Fair Value, Inputs, Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	0	0
Alternative Investments | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plans and Other Postretirement Benefit Plans
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	34.8	28.1
Cash Equivalents
Defined Benefit Plans and Other Postretirement Benefit Plans
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	1.3	1.9
Cash Equivalents | Fair Value, Inputs, Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	1.3	1.9
Cash Equivalents | Fair Value, Inputs, Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	0	0
Cash Equivalents | Fair Value, Inputs, Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	0	0
Cash Equivalents | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plans and Other Postretirement Benefit Plans
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	0	0
Total Invested Assets
Defined Benefit Plans and Other Postretirement Benefit Plans
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	145.4	141.2
Total Invested Assets | Fair Value, Inputs, Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	104.7	104.8
Total Invested Assets | Fair Value, Inputs, Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	0	0
Total Invested Assets | Fair Value, Inputs, Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	0	0
Total Invested Assets | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plans and Other Postretirement Benefit Plans
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	$ 40.7	$ 36.4

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, 2023	Dec. 31, 2022
Defined Benefit Plans and Other Postretirement Benefit Plans
Life Settlement Contracts, Fair Value Method, Face Value	$ 8.2	$ 8.5
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	$ 8.2	$ 8.5

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, 2023	Dec. 31, 2022
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Fair Value of Plan Assets at Beginning of Year	$ 8.5	$ 9
Fair Value of Plan Assets at End of Year	8.2	8.5
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	8.5	9
Actual Return on Plan Assets Still Held	0	0.1
Plan Participant Contributions	8.7	9.5
Defined Benefit Plan, Plan Assets, Benefits Paid	9	10.1
Fair Value of Plan Assets at End of Year	$ 8.2	$ 8.5

Employee Benefit Plans Measurem

Employee Benefit Plans Measurement Assumptions (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Pension Plan | UNITED STATES
Defined Benefit Plans and Other Postretirement Benefit Plans
Discount Rate Assumptions Used Calculating Benefit Obligation	5.40%	5.70%
Discount Rate Assumptions Used Calculating Net Periodic Benefit Cost	5.70%	3.10%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets	7.25%	6%
Pension Plan | Foreign Plan
Defined Benefit Plans and Other Postretirement Benefit Plans
Discount Rate Assumptions Used Calculating Benefit Obligation	4.50%	4.80%
Rate of Compensation Increase Assumptions Used Calculating Benefit Obligation	2.40%	2.50%
Discount Rate Assumptions Used Calculating Net Periodic Benefit Cost	4.80%	2%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets	6.70%	4.20%
Rate of Compensation Increase Assumptions Used Calculating Net Periodic Benefit Cost	2.50%	2.90%
Other Postretirement Benefit Plans
Defined Benefit Plans and Other Postretirement Benefit Plans
Discount Rate Assumptions Used Calculating Benefit Obligation	5.40%	5.70%
Discount Rate Assumptions Used Calculating Net Periodic Benefit Cost	5.70%	2.90%
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, 2023	Dec. 31, 2022	Dec. 31, 2021
Pension Plan | UNITED STATES
Defined Benefit Plans and Other Postretirement Benefit Plans
Service Cost	$ 9.2	$ 7.7	$ 9.6
Interest Cost	87.9	67.2	65
Expected Return on Plan Assets	(92)	(105.9)	(100.6)
Amortization of Net Actuarial Loss (Gain)	15.2	16.3	21.3
Amortization of Prior Service Cost (Credit)	0	0	0
Net Periodic Benefit Cost	20.3	(14.7)	(4.7)
Pension Plan | Foreign Plan
Defined Benefit Plans and Other Postretirement Benefit Plans
Service Cost	0	0	0
Interest Cost	7.7	5	4.2
Expected Return on Plan Assets	(8.5)	(10.9)	(9.8)
Amortization of Net Actuarial Loss (Gain)	2.5	0.4	1.3
Amortization of Prior Service Cost (Credit)	0	0	0
Net Periodic Benefit Cost	1.7	(5.5)	(4.3)
Other Postretirement Benefit Plans
Defined Benefit Plans and Other Postretirement Benefit Plans
Service Cost	0	0	0
Interest Cost	4.5	3	3
Expected Return on Plan Assets	(0.5)	(0.5)	(0.5)
Amortization of Net Actuarial Loss (Gain)	(10.5)	(1)	0
Amortization of Prior Service Cost (Credit)	(0.2)	(0.2)	(0.2)
Net Periodic Benefit Cost	$ (6.7)	$ 1.3	$ 2.3

Employee Benefit Plans Expected

Employee Benefit Plans Expected Benefit Payments (Details) $ in Millions	Dec. 31, 2023 USD ($)
Pension Plan | UNITED STATES
Defined Benefit Plans and Other Postretirement Benefit Plans
Benefit Payments in Year One	$ 83.5
Benefit Payments in Year Two	87
Benefit Payments in Year Three	91.2
Benefit Payments in Year Four	95.1
Benefit Payments in Year Five	98.8
Benefit Payments in Five Fiscal Years Thereafter	533.2
Pension Plan | Foreign Plan
Defined Benefit Plans and Other Postretirement Benefit Plans
Benefit Payments in Year One	6.7
Benefit Payments in Year Two	7.1
Benefit Payments in Year Three	7.7
Benefit Payments in Year Four	8.2
Benefit Payments in Year Five	8.5
Benefit Payments in Five Fiscal Years Thereafter	47
Other Postretirement Benefit Plans
Defined Benefit Plans and Other Postretirement Benefit Plans
Benefit Payments in Year One	9.1
Prescription Drug Subsidy Receipts in Year One	0
Net OPEB Payments in Year One	9.1
Benefit Payments in Year Two	8.7
Prescription Drug Subsidy Receipts in Year Two	0
Net OPEB Payments in Year Two	8.7
Benefit Payments in Year Three	8.3
Prescription Drug Subsidy Receipts in Year Three	0
Net OPEB Payments in Year Three	8.3
Benefit Payments in Year Four	8
Prescription Drug Subsidy Receipts in Year Four	0
Net OPEB Payments in Year Four	8
Benefit Payments in Year Five	7.6
Prescription Drug Subsidy Receipts in Year Five	0
Net OPEB Payments in Year Five	7.6
Benefit Payments in Five Fiscal Years Thereafter	31.9
Prescription Drug Subsidy Receipts in Five Fiscal Years Thereafter	0.1
Net OPEB Payments in Five Fiscal Years Thereafter	$ 31.8

Employee Benefit Plans - Additi

Employee Benefit Plans - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pension and Other Postretirement Benefits Disclosure
Health Care Cost Trend Rate Assumed for Next Fiscal Year	6.75%	7%
Ultimate Health Care Cost Trend Rate	5%
Defined Benefit Plan, Year Health Care Cost Trend Rate Reaches Ultimate Trend Rate	2031
Pension Plan | UNITED STATES
Pension and Other Postretirement Benefits Disclosure
Average Remaining Life Expectancy of Plan Participants	24 years
Alternative Investments, Unfunded Commitments	$ 17.5	$ 24.5
Pension Plan | Foreign Plan
Pension and Other Postretirement Benefits Disclosure
Average Remaining Life Expectancy of Plan Participants	27 years
Alternative Investments, Unfunded Commitments	$ 9.9	17.3
Other Postretirement Benefit Plans
Pension and Other Postretirement Benefits Disclosure
Average Remaining Life Expectancy of Plan Participants	12 years
Investment Level 3 Transfers Into	$ 0	0
Investment Level 3 Transfers Out of	$ 0	$ 0
Interest Rate During Period	4.46%	4.31%
Other Postretirement Benefit Plans | UNITED STATES
Pension and Other Postretirement Benefits Disclosure
Matching Contribution Percent of Employees' Gross Pay	5%
Employer Discretionary Contribution Percentage of earnings	4.50%
Cost Recognized	$ 74.3	$ 70.9	$ 71
Other Postretirement Benefit Plans | Foreign Plan
Pension and Other Postretirement Benefits Disclosure
Defined Contribution Plan, Minimum Employee Contribution Eligible for Matching	1%
Defined Contribution Plan, Maximum Employee Contribution Eligible for Matching	5%
Cost Recognized	$ 5.7	$ 4.9	$ 4.9
Equity Funds | Pension Plan | UNITED STATES
Pension and Other Postretirement Benefits Disclosure
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	38%
Fixed Maturity Securities | Pension Plan | UNITED STATES
Pension and Other Postretirement Benefits Disclosure
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	30%
All Other Asset Categories | Pension Plan | UNITED STATES
Pension and Other Postretirement Benefits Disclosure
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	32%
Diversified Growth Assets | Pension Plan | Foreign Plan
Pension and Other Postretirement Benefits Disclosure
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	48%
Fixed Income and Index-linked Securities | Pension Plan | Foreign Plan
Pension and Other Postretirement Benefits Disclosure
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	52%
Minimum | Pension Plan | UNITED STATES
Pension and Other Postretirement Benefits Disclosure
Private Equity Partnership Future Liquidation Term	5 years
Minimum | Other Postretirement Benefit Plans | Foreign Plan
Pension and Other Postretirement Benefits Disclosure
Matching Contribution Percent of Employees' Gross Pay	8%
Maximum | Pension Plan | UNITED STATES
Pension and Other Postretirement Benefits Disclosure
Private Equity Partnership Future Liquidation Term	8 years
Maximum | Other Postretirement Benefit Plans | Foreign Plan
Pension and Other Postretirement Benefits Disclosure
Matching Contribution Percent of Employees' Gross Pay	12%

Basic and Diluted Earnings Per

Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Numerator
Net Income	$ 1,283.8	$ 1,407.2	$ 981
Denominator
Weighted Average Common Shares - Basic	196,659,700	200,647,200	204,232,900
Dilution for Assumed Exercises of Stock Options and Nonvested Stock Awards	942,300	1,462,200	615,000
Weighted Average Common Shares - Assuming Dilution	197,602,000	202,109,400	204,847,900
Net Income Per Common Share
Basic	$ 6.53	$ 7.01	$ 4.80
Assuming Dilution	$ 6.50	$ 6.96	$ 4.79

Treasury Stock Transactions (De

Treasury Stock Transactions (Details) - USD ($) shares in Millions, $ in Millions		3 Months Ended	12 Months Ended
		Mar. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Equity, Class of Treasury Stock
Number of Treasury Shares Repurchased			5.7	5.7	1.9
Cost of Shares Repurchased	[1]		$ 252	$ 200.1	$ 50
Commission Paid on Stock Repurchases			0.1
Share Repurchases Excise Tax			1.9	0	0
Accelerated Share Repurchase Agreement
Equity, Class of Treasury Stock
Cost of Shares Repurchased			50	$ 50	$ 50
Repurchase Program Authorized in December 2023
Equity, Class of Treasury Stock
Stock Repurchase Program, Authorized Amount			$ 500
Repurchase Program Authorized in December 2022
Equity, Class of Treasury Stock
Stock Repurchase Program Expiration Date			Dec. 31, 2023
Stock Repurchase Program, Authorized Amount			$ 250
Remaining Amount of Treasury Share Repurchases Authorized Under Stock Repurchase Program			$ 0
Repurchase Program Authorized in October 2021
Equity, Class of Treasury Stock
Stock Repurchase Program Expiration Date			Dec. 31, 2022
Stock Repurchase Program, Authorized Amount			$ 250
Remaining Amount of Treasury Share Repurchases Authorized Under Stock Repurchase Program			$ 0
Subsequent Event | Accelerated Share Repurchase Agreement
Equity, Class of Treasury Stock
Cost of Shares Repurchased		$ 100
[1]Includes $0.1 million of commissions for the years ended December 31, 2023 and 2022, respectively. There were no commissions for the year ended December 31, 2021. Also includes $1.9 million of excise tax for the year ended December 31, 2023. There were no excise taxes during the years ended December 31, 2022 and 2021.

Stockholders' Equity and Earn_3

Stockholders' Equity and Earnings Per Common Share - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Stockholders Equity and Earnings Per Common Share Additional Information [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share	500,000	100,000	1,100,000
Treasury Stock, Retired, Cost Method, Amount	$ 3,642.5
Authorized Shares of Preferred Stock	25,000,000
Par Value Per Share of Preferred Stock	$ 0.10
Issued Shares of Preferred Stock	0
Common Class A
Stockholders Equity and Earnings Per Common Share Additional Information [Line Items]
Treasury Stock, Shares, Retired	115,000,000

Stock-Based Compensation - Valu

Stock-Based Compensation - Valuation Assumptions on PSU Grants (Details) - Performance Share Units	12 Months Ended
	Dec. 31, 2020 Rate
Share-based Compensation Arrangement by Share-based Payment Award
Expected Volatility Rate	23%
Expected Life	3 years
Risk Free Interest Rate	0.85%

Stock-Based Compensation - Acti

Stock-Based Compensation - Activity for CIUs (Details) - Cash Incentive Units (CIUs) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award, Liability Instruments, Nonvested, Number of Shares
Shares Outstanding Beginning Balance	15,247
Shares Granted	9,004	8,000	7,200
Share Vested	(7,223)
Shares Outstanding Ending Balance	17,028	15,247

Stock-Based Compensation - Va_2

Stock-Based Compensation - Valuation Assumptions on CIU Grants (Details) - Cash Incentive Units (CIUs)	12 Months Ended
	Dec. 31, 2023 Rate	Dec. 31, 2022 Rate	Dec. 31, 2021 Rate
2023 CIUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award
Expected Volatility Rate	30%
Expected Life	2 years
Risk Free Interest Rate	4.26%
2022 CIUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award
Expected Volatility Rate	27%	30%
Expected Life	1 year	2 years
Risk Free Interest Rate	4.75%	4.26%
2021 CIUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award
Expected Volatility Rate		33%	50%
Expected Life		1 year	2 years
Risk Free Interest Rate		4.60%	0.71%

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, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares
Shares Outstanding Beginning Balance	2,182
Shares Granted	780
Shares Vested	(1,691)
Shares Forfeited	(58)
Shares Outstanding Ending Balance	1,213	2,182
Weighted Average Grant Date Fair Value at Beginning of Period	$ 27.20
Weighted Average Grant Date Fair Value of Shares Granted	45.56	$ 28.21	$ 27.02
Weighted Average Grant Date Fair Value of Shares Vested	29.54
Weighted Average Grant Date Fair Value of Shares Forfeited	31.86
Weighted Average Grant Date Fair Value at End of Period	$ 35.51	$ 27.20

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, 2023 shares
Share-based Compensation Arrangement by Share-based Payment Award, Liability Instruments, Nonvested, Number of Shares
Shares Outstanding Beginning Balance	23
Shares Vested	(23)
Shares Outstanding Ending Balance	0

Stock-Based Compensation Expens

Stock-Based Compensation Expense (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award
Allocated Share-based Compensation Expense, Before Tax	$ 64,100,000	$ 52,700,000	$ 35,400,000
Allocated Share-based Compensation Expense, Net of Tax	57,500,000	47,300,000	31,100,000
Performance Share Units
Share-based Compensation Arrangement by Share-based Payment Award
Allocated Share-based Compensation Expense, Before Tax	300,000	5,700,000	3,300,000
Cash Incentive Units (CIUs)
Share-based Compensation Arrangement by Share-based Payment Award
Allocated Share-based Compensation Expense, Before Tax	21,700,000	12,800,000	3,200,000
Restricted Stock Units and Cash-Settled Awards
Share-based Compensation Arrangement by Share-based Payment Award
Allocated Share-based Compensation Expense, Before Tax	40,600,000	32,700,000	25,500,000
Stock Success Units (SSUs)
Share-based Compensation Arrangement by Share-based Payment Award
Allocated Share-based Compensation Expense, Before Tax	900,000	900,000	2,800,000
Other Awards
Share-based Compensation Arrangement by Share-based Payment Award
Allocated Share-based Compensation Expense, Before Tax	$ 600,000	$ 600,000	$ 600,000

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award
Cash Received Under Share-based Payment Arrangements	$ 5.2	$ 4.2	$ 3.8
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
Stock Incentive Plan 2022
Share-based Compensation Arrangement by Share-based Payment Award
Number of Shares Authorized	6,800,000
Number of Shares for Each Full Value Award	1
Total Duration of the Stock Incentive Plan	10 years
Number of Shares Available for Grant	5,900,000
Performance Share Units
Share-based Compensation Arrangement by Share-based Payment Award
Award Vesting Period	3 years
Shares Outstanding	0	0
Shares Granted	245,000	0	0
Fair Value of Awards Vested During the Period	$ 5.8	$ 4.2	$ 6.6
Compensation Cost Not yet Recognized	$ 0
Shares Forfeited	0
Shares Vested	(245,000)
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award
Shares Outstanding	1,213,000	2,182,000
Weighted Average Grant Date Fair Value of Shares Granted	$ 45.56	$ 28.21	$ 27.02
Shares Granted	780,000
Fair Value of Awards Vested During the Period	$ 49.9	$ 28	$ 23.9
Compensation Cost Not yet Recognized	$ 26
Period for Recognition of Compensation Cost Not Yet Recognized	10 months 24 days
Shares Forfeited	(58,000)
Shares Vested	(1,691,000)
Stock Success Units (SSUs)
Share-based Compensation Arrangement by Share-based Payment Award
Shares Outstanding	105,000	208,000
Weighted Average Grant Date Fair Value of Shares Granted	$ 18.78	$ 18.78
Shares Granted	0	0	0
Fair Value of Awards Vested During the Period	$ 1.9	$ 0	$ 1.9
Compensation Cost Not yet Recognized	$ 0.7
Period for Recognition of Compensation Cost Not Yet Recognized	1 year 18 days
Shares Forfeited	0
Cash Settled RSUs
Share-based Compensation Arrangement by Share-based Payment Award
Compensation Cost Not yet Recognized	$ 0
Shares Granted	0	0	0
Deferred Compensation Cash-Based Arrangements, Liability, Current and Noncurrent		$ 0.8	$ 0.5
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Share-Based Liabilities Paid	$ 1.1	$ 0.6	$ 0.6
Cash Incentive Units (CIUs)
Share-based Compensation Arrangement by Share-based Payment Award
Award Vesting Period	3 years
Compensation Cost Not yet Recognized	$ 3.4
Period for Recognition of Compensation Cost Not Yet Recognized	1 year 8 months 12 days
Shares Granted	9,004,000	8,000,000	7,200,000
Deferred Compensation Cash-Based Arrangements, Liability, Current and Noncurrent	$ 37.7	$ 16	$ 3.2
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Share-Based Liabilities Paid
Minimum | Performance Share Units
Share-based Compensation Arrangement by Share-based Payment Award
Percentage of Stock-based Awards Possible to be Earned	40%
Minimum | Restricted Stock Units (RSUs)
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%
Maximum | Restricted Stock Units (RSUs)
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
Maximum | Cash Incentive Units (CIUs)
Share-based Compensation Arrangement by Share-based Payment Award
Percentage of Stock-based Awards Possible to be Earned	200%

Reinsurance - Premium Income Da

Reinsurance - Premium Income Data (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022		Dec. 31, 2021
Reinsurance Disclosures [Abstract]
Direct Premium Income	$ 10,286.8	$ 9,893.6		$ 9,736.8
Reinsurance Assumed	80.4	78.7		90.6
Reinsurance Ceded	(321.2)	(355.8)		(352.4)
Premium Income	10,046	9,616.5		9,475
Policyholder Benefits and Claims Incurred, Direct	8,001.8	8,205.3		8,817.1
Policyholder Benefits and Claims Incurred, Assumed	138.7	135.1		145
Ceded Benefits and Change in Reserves for Future Benefits	(828.6)	(798.3)		(848.8)
Policy Benefits	7,311.9	7,542.1	[1]	8,113.3	[1]
Liability for Future Policy Benefit, Remeasurement Gain (Loss), Direct	(49.2)	(372.5)		(546.2)
Liability for Future Policy Benefit, Remeasurement Gain (Loss), Assumed	(0.1)	36.4		1.9
Liability for Future Policy Benefit, Remeasurement Gain (Loss), Ceded	(5.5)	(211.4)		(15.6)
Liability for Future Policy Benefit, Remeasurement Gain (Loss)	$ (54.8)	$ (547.5)		$ (559.9)
[1] 1 Previously disclosed as Benefits and Change in Reserves for Future Benefits

Reinsurance - Additional Inform

Reinsurance - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Mar. 31, 2021 USD ($)
Negative Ceding Commission			$ 18.2
Net Realized Gain Related to the Transfer of Investments	$ (36)	$ (15.7)	76.7
Transaction Costs Related to Reinsurance Transaction	1,112	1,006.7	999.3
reduction in cost of reinsurance	$ (44.1)	(50.3)	(69.8)
Number of companies that make up majority of reinsurance recoverable	9
Closed Block Individual Disability Reinsurance Transaction
Net Realized Gain Related to the Transfer of Investments			67.6
Transaction Costs Related to Reinsurance Transaction			6.2
Reinsurance Recoverables, Incurred but Not Reported Claims				$ 1,132.5
reduction in cost of reinsurance			(99.4)
Deposit Contracts, Assets				$ 5
Amortization of Prepaid Reinsurance Premium	$ 44.1	$ 50.3	$ 69.8
AM Best A Rating or Better | Reinsurer Concentration Risk | Reinsurance Recoverable | Commonwealth Annuity and Life Insurance Company
Percentage of Concentration Risk	56%
AM Best A Rating or Better | Reinsurer Concentration Risk | Reinsurance Recoverable | Top 9 Reinsurers
Percentage of Concentration Risk	39%
AM Best, A- Rating | Reinsurer Concentration Risk | Reinsurance Recoverable | Other Reinsurers
Percentage of Concentration Risk	4%
AM Best, Below A- or Not Rated | Reinsurer Concentration Risk | Reinsurance Recoverable | Other Reinsurers
Percentage of Concentration Risk	1%

Premium Income by Major Line of

Premium Income by Major Line of Business within Each Segment (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Segment Reporting Information
Premium Income	$ 10,046	$ 9,616.5	$ 9,475
Accident, Sickness, and Disability
Segment Reporting Information
Premium Income	7,398.5	7,060.8	7,072.9
Life
Segment Reporting Information
Premium Income	2,647.5	2,555.7	2,402.1
Operating Segments
Segment Reporting Information
Premium Income	10,046	9,616.5	9,475
Operating Segments | Unum US
Segment Reporting Information
Premium Income	6,579.2	6,251.4	6,072
Operating Segments | Unum US | Group Long-term Disability
Segment Reporting Information
Premium Income	2,057.2	1,911.7	1,827.8
Operating Segments | Unum US | Group Short-term Disability
Segment Reporting Information
Premium Income	1,012.3	926.3	864
Operating Segments | Unum US | Group Life
Segment Reporting Information
Premium Income	1,679	1,669.1	1,641.9
Operating Segments | Unum US | Accidental Death & Dismemberment
Segment Reporting Information
Premium Income	175.5	173.7	165.1
Operating Segments | Unum US | Voluntary Benefits
Segment Reporting Information
Premium Income	850.1	833.7	840.7
Operating Segments | Unum US | Individual Disability
Segment Reporting Information
Premium Income	527	461.1	459.8
Operating Segments | Unum US | Dental and Vision
Segment Reporting Information
Premium Income	278.1	275.8	272.7
Operating Segments | Unum International
Segment Reporting Information
Premium Income	825.2	718.8	717
Operating Segments | Unum International | Group Long-term Disability
Segment Reporting Information
Premium Income	396.1	376.9	401.9
Operating Segments | Unum International | Group Life
Segment Reporting Information
Premium Income	169.3	138.2	112.3
Operating Segments | Unum International | Supplemental
Segment Reporting Information
Premium Income	141.5	114	112.6
Operating Segments | Unum International | Unum Poland
Segment Reporting Information
Premium Income	118.3	89.7	90.2
Operating Segments | Colonial Life
Segment Reporting Information
Premium Income	1,726.1	1,702	1,690.2
Operating Segments | Colonial Life | Accident, Sickness, and Disability
Segment Reporting Information
Premium Income	946.1	948.9	953.3
Operating Segments | Colonial Life | Life
Segment Reporting Information
Premium Income	426.5	401.1	384.7
Operating Segments | Colonial Life | Cancer and Critical Illness Colonial
Segment Reporting Information
Premium Income	353.5	352	352.2
Operating Segments | Closed Block
Segment Reporting Information
Premium Income	915.5	944.3	995.8
Operating Segments | Closed Block | Long-term Care
Segment Reporting Information
Premium Income	696	697.4	704.3
Operating Segments | Closed Block | Other Insurance Product Line
Segment Reporting Information
Premium Income	$ 219.5	$ 246.9	$ 291.5

Selected Operating Statement Da

Selected Operating Statement Data by Segment (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Segment Reporting Information
Premium Income	$ 10,046	$ 9,616.5	$ 9,475
Net Investment Income	2,096.7	2,122.2	2,213.2
Other Income	279.2	261.1	242.9
Interest and Debt Expense	194.8	188.5	185
Cost Related to Early Retirement of Debt	0	4.2	67.3
Amortization of Deferred Acquisition Costs	481.4	421.1	452.1
Unum US
Segment Reporting Information
Amortization of Deferred Acquisition Costs	267.6	240.9	285.9
Unum International
Segment Reporting Information
Amortization of Deferred Acquisition Costs	8.4	8.2	7
Colonial Life
Segment Reporting Information
Amortization of Deferred Acquisition Costs	205.4	172	159.2
Operating Segments
Segment Reporting Information
Premium Income	10,046	9,616.5	9,475
Net Investment Income	2,096.7	2,122.2	2,213.2
Other Income	279.2	261.1	242.9
Adjusted Operating Revenue	12,421.9	11,999.8	11,931.1
Adjusted Operating Income (Loss)	1,932.2	1,607.1	1,151.1
Interest and Debt Expense	194.8	188.5	185
Cost Related to Early Retirement of Debt		4.2	67.3
Amortization of Deferred Acquisition Costs	481.4	421.1	452.1
Depreciation and Amortization	110.3	110.4	117
Operating Segments | Unum US
Segment Reporting Information
Premium Income	6,579.2	6,251.4	6,072
Net Investment Income	639.9	676.3	721.6
Other Income	220.5	196.3	170
Adjusted Operating Revenue	7,439.6	7,124	6,963.6
Adjusted Operating Income (Loss)	1,355.5	972.6	398.9
Interest and Debt Expense	0	0	0
Cost Related to Early Retirement of Debt		0	0
Amortization of Deferred Acquisition Costs	267.6	240.9	285.9
Depreciation and Amortization	76.3	75.7	81.9
Operating Segments | Unum International
Segment Reporting Information
Premium Income	825.2	718.8	717
Net Investment Income	137.2	170.1	132.7
Other Income	1.6	0.9	0.6
Adjusted Operating Revenue	964	889.8	850.3
Adjusted Operating Income (Loss)	158.1	134	105.7
Interest and Debt Expense	0	0	0
Cost Related to Early Retirement of Debt		0	0
Amortization of Deferred Acquisition Costs	8.4	8.2	7
Depreciation and Amortization	14.6	14.4	13
Operating Segments | Colonial Life
Segment Reporting Information
Premium Income	1,726.1	1,702	1,690.2
Net Investment Income	153.5	152.7	172
Other Income	1.2	1.1	1
Adjusted Operating Revenue	1,880.8	1,855.8	1,863.2
Adjusted Operating Income (Loss)	400.1	412.9	404.3
Interest and Debt Expense	0	0	0
Cost Related to Early Retirement of Debt		0	0
Amortization of Deferred Acquisition Costs	205.4	172	159.2
Depreciation and Amortization	13.6	15	16.3
Operating Segments | Closed Block
Segment Reporting Information
Premium Income	915.5	944.3	995.8
Net Investment Income	1,066.3	1,070.6	1,159
Other Income	52.6	58	65.1
Adjusted Operating Revenue	2,034.4	2,072.9	2,219.9
Adjusted Operating Income (Loss)	164.9	251.9	420.1
Interest and Debt Expense	0	0	0
Cost Related to Early Retirement of Debt		0	0
Amortization of Deferred Acquisition Costs	0	0	0
Depreciation and Amortization	5.2	4.7	5.1
Operating Segments | Corporate and Other Segment
Segment Reporting Information
Premium Income	0	0	0
Net Investment Income	99.8	52.5	27.9
Other Income	3.3	4.8	6.2
Adjusted Operating Revenue	103.1	57.3	34.1
Adjusted Operating Income (Loss)	(146.4)	(164.3)	(177.9)
Interest and Debt Expense	194.8	188.5	185
Amortization of Deferred Acquisition Costs	0	0	0
Depreciation and Amortization	$ 0.6	$ 0.6	$ 0.7

Assets by Segment (Detail)

Assets by Segment (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Segment Reporting Information
Total Assets	$ 63,255.2	$ 61,148.5
Operating Segments | Unum US
Segment Reporting Information
Total Assets	15,561.1	16,356.3
Operating Segments | Unum International
Segment Reporting Information
Total Assets	3,372.9	3,129.4
Operating Segments | Colonial Life
Segment Reporting Information
Total Assets	4,830.4	4,575
Operating Segments | Closed Block
Segment Reporting Information
Total Assets	35,272.8	33,776.6
Operating Segments | Corporate and Other Segment
Segment Reporting Information
Total Assets	$ 4,218	$ 3,311.2

Reconciliation of Total Revenue

Reconciliation of Total Revenue and Income Before Income Tax to Operating Revenue and Operating Income (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Segment Reporting, Revenue Reconciling Item
Total Revenue	$ 12,385.9	$ 11,984.1	$ 12,007.8
Net Investment Gain (Loss)	(36)	(15.7)	76.7
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	1,640.1	1,750	1,260.6
Operating Lease, Impairment Loss			(13.9)
Closed Block Individual Disability Reinsurance Transaction
Segment Reporting, Revenue Reconciling Item
Net Investment Gain (Loss)			67.6
Amortization of the Cost of Reinsurance	(44.1)	(50.3)	(69.8)
Operating Segments
Segment Reporting, Revenue Reconciling Item
Total Revenue	12,385.9	11,984.1	12,007.8
Net Investment Gain (Loss)	(36)	(15.7)	76.7
Adjusted Operating Revenue	12,421.9	11,999.8	11,931.1
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	1,640.1	1,750	1,260.6
Net Reserve Decrease Related to Reserve Assumption Updates, Before Tax	(177.2)	243.3	235
Capitalized Computer Software, Impairments	0	0	(12.1)
Costs Related to Early Retirement of Debt	0	0	(67.3)
Operating Lease, Impairment Loss	0	0	(13.9)
Adjusted Operating Income	1,932.2	1,607.1	1,151.1
Operating Segments | Closed Block Individual Disability Reinsurance Transaction
Segment Reporting, Revenue Reconciling Item
Net Investment Gain (Loss)	0	0	67.6
Amortization of the Cost of Reinsurance		(50.3)
Non-Contemporaneous Reinsurance	(34.8)	(34.4)	(32.9)
Transaction Costs	0	0	(6.2)
Operating Segments | Unrelated to Significant Transaction
Segment Reporting, Revenue Reconciling Item
Net Investment Gain (Loss)	$ (36)	$ (15.7)	$ 9.1

Segment Information Segments -

Segment Information Segments - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($) Integer	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Supplementary Insurance Information, by Segment
Number of Operating Segments | Integer	3
Goodwill	$ 349.9	$ 347.6
Operating Segments
Supplementary Insurance Information, by Segment
Capitalized Computer Software, Impairments	0	0	$ 12.1
Unum US
Supplementary Insurance Information, by Segment
Goodwill	280	280
Unum International
Supplementary Insurance Information, by Segment
Goodwill	42.2	39.9
Colonial Life
Supplementary Insurance Information, by Segment
Goodwill	$ 27.7	$ 27.7

Leases, Cost (Details)

Leases, Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Leases [Abstract]
Operating Lease Cost	$ 16.4	$ 19.6	$ 35.2
Sublease Income	1.5	1.1	1
Total Lease Cost	14.9	18.5	34.2
Cash Paid for Amounts Included in the Measurement of Lease Liabilities	$ 20.3	$ 23.1	$ 29.9
Weighted-Average Remaining Lease Term	5 years	6 years	6 years
Weighted-Average Discount Rate	4.85%	4.32%	4.45%

Lessee, Operating Lease, Liabil

Lessee, Operating Lease, Liability, Payment, Due (Details) $ in Millions	Dec. 31, 2023 USD ($)
Leases [Abstract]
Lessee, Operating Lease, Liability, Payments, Due Next Twelve Months	$ 19.2
Lessee, Operating Lease, Liability, Payments, Due Year Two	13.9
Lessee, Operating Lease, Liability, Payments, Due Year Three	11.1
Lessee, Operating Lease, Liability, Payments, Due Year Four	9.3
Lessee, Operating Lease, Liability, Payments, Due Year Five	9
Lessee, Operating Lease, Liability, Payments, Due after Year Five	9.1
Lessee, Operating Lease, Liability, Payments, Due	71.6
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	$ 9
Operating Lease, Liability	Other Liabilities
Operating Lease, Liability	$ 62.6

Leases - Additional Information

Leases - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2023	Dec. 31, 2022
Leases [Abstract]
Operating Lease, Impairment Loss	$ 13.9
Operating Lease, Right-of-Use Asset		$ 35.8	$ 37.7
Operating Lease, Right-of-Use-Asset		Other Assets	Other Assets

Statutory Permitted Practice In

Statutory Permitted Practice Information (Detail) - Unum Life Insurance Company of America - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Statutory Accounting Practices
Statutory Accounting Practices, Permitted Practice, Cumulative Amount	$ 1,604	$ 1,191	$ 667
Statutory Accounting Practices, Permitted Practice, Reserve Deficiency	$ 0	$ 1,660	$ 2,310

Statutory Financial Informati_3

Statutory Financial Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Traditional U.S. Life Insurance Subsidiaries
Statutory Accounting Practices
Statutory Net Income (Loss)	$ 1,329.9	$ 965.4	$ 779.5
Statutory Combined Net Gain (Loss) from Operations	1,351.5	965.4	681.1
Statutory Combined Capital and Surplus	3,751.3	3,816.3
Captive Reinsurers
Statutory Accounting Practices
Statutory Net Income (Loss)	(318.3)	(432.2)	(159)
Statutory Combined Net Gain (Loss) from Operations	(279.4)	(428.6)	$ (247.4)
Statutory Combined Capital and Surplus	$ 1,534.9	$ 1,229.6

Statutory Financial Informati_4

Statutory Financial Information - Additional Details (Detail) £ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2022 GBP (£)	Dec. 31, 2021 USD ($)	Dec. 31, 2023 GBP (£)	Dec. 31, 2022 GBP (£)
Unum Life Insurance Company of America
Statutory Accounting Practices
Statutory Accounting Practices, Permitted Practice, Amount	$ 413	$ 524		$ 438
Fairwind Insurance Company
Statutory Accounting Practices
Statutory Accounting Practices, Permitted Practice, Amount	469	351
Unum Limited
Statutory Accounting Practices
Statutory Net Income | £			£ 569.2
Statutory Combined Capital and Surplus | £						£ 622.7
Statutory Accounting Practices, Statutory Amount Available for Dividend Payments | £					£ 140
Traditional U.S. Life Insurance Subsidiaries
Statutory Accounting Practices
Statutory Net Income	1,329.9	965.4		$ 779.5
Statutory Combined Capital and Surplus	3,751.3	3,816.3
Statutory Accounting Practices, Statutory Amount Available for Dividend Payments	1,289
Cash and Securities Segregated under Federal and Other Regulations	$ 119.1	$ 118.8

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, 2023 USD ($)
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost of Investments	$ 47,253.7
Amount Shown on the Balance Sheet	45,962.4
Commercial Real Estate
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost of Investments	2,328.4	[1]
Amount Shown on the Balance Sheet	2,318.2
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	618.6	[1]
Fair Value of Investments	624.8
Amount Shown on the Balance Sheet	624.8
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	4,041.3	[1]
Fair Value of Investments	3,678.4
Amount Shown on the Balance Sheet	3,678.4
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	982.1	[1]
Fair Value of Investments	890.7
Amount Shown on the Balance Sheet	890.7
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	5,398.2	[1]
Fair Value of Investments	5,321.6
Amount Shown on the Balance Sheet	5,321.6
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	658	[1]
Fair Value of Investments	644.1
Amount Shown on the Balance Sheet	644.1
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	26,708.4	[1]
Fair Value of Investments	25,670.7
Amount Shown on the Balance Sheet	25,670.7
Redeemable Preferred Stocks
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost of Investments	4	[1]
Fair Value of Investments	3.6
Amount Shown on the Balance Sheet	3.6
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	38,410.6	[1]
Fair Value of Investments	36,833.9
Amount Shown on the Balance Sheet	36,833.9
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	3,620.2
Amount Shown on the Balance Sheet	3,620.2
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
Amount Shown on the Balance Sheet	99.9	[2]
Perpetual Preferred Securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost of Investments	27.8
Amount Shown on the Balance Sheet	31.9	[3]
Private Equity Funds
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost of Investments	1,134.6
Amount Shown on the Balance Sheet	1,326.2	[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	121.4
Amount Shown on the Balance Sheet	121.4
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	1,610.7
Amount Shown on the Balance Sheet	$ 1,610.7
[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 credit losses. Derivatives are carried at fair value. The difference between amortized cost and carrying value for private equity partnerships and perpetual preferred and equity securities primarily results from changes in the partnership owner's equity and the security's market valuation since acquisition, respectively.

Parent Company Balance Sheet (D

Parent Company Balance Sheet (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022		Dec. 31, 2021	Jan. 01, 2021
Assets
Fixed Maturity Securities - at fair value (amortized cost: $656.2; $748.1)	$ 36,833.9	$ 34,840.8
Other Long-term Investments	1,579.4	1,440.1
Short-term Investments	1,610.7	1,394.8
Deferred Income Tax Assets, Net	649.4	586
Other Assets	1,661.7	1,666.6	[1]
Total Assets	63,255.2	61,148.5
Liabilities
Short-term debt	0	2
Long-term Debt	3,430.4	3,427.8
Other Liabilities	2,283.4	2,334.4
Liabilities	53,603.8	52,413.5
Stockholders' Equity
Common Stock	19.4	30.8
Additional Paid-in Capital	1,547.8	2,441
Accumulated Other Comprehensive Income	(3,308)	(3,448.3)		$ (5,164.6)	$ (6,310.2)
Retained Earnings	11,431.5	13,141.3		11,989.4	$ 11,249
Treasury Stock	(39.3)	(3,429.8)
Total Stockholders' Equity	9,651.4	8,735		$ 6,033.9
Total Liabilities and Stockholders' Equity	63,255.2	61,148.5
Amortized Cost of Fixed Maturity Securities	38,410.6	37,825.2
Parent Company
Assets
Fixed Maturity Securities - at fair value (amortized cost: $656.2; $748.1)	596.1	657.7
Other Long-term Investments	27	19.3
Short-term Investments	970.9	845.8
Investments in Subsidiaries	11,663.6	10,815.7
Deferred Income Tax Assets, Net	118.1	114.9
Other Assets	593.6	555.5
Total Assets	13,969.3	13,008.9
Liabilities
Short-term debt	0	2
Long-term Debt	3,430.4	3,427.8
Pension and Postretirement Benefits	350.2	352.6
Other Liabilities	537.3	491.5
Liabilities	4,317.9	4,273.9
Stockholders' Equity
Common Stock	19.4	30.8
Additional Paid-in Capital	1,547.8	2,441
Accumulated Other Comprehensive Income	(3,308)	(3,448.3)
Retained Earnings	11,431.5	13,141.3
Treasury Stock	(39.3)	(3,429.8)
Total Stockholders' Equity	9,651.4	8,735
Total Liabilities and Stockholders' Equity	13,969.3	13,008.9
Amortized Cost of Fixed Maturity Securities	$ 656.2	$ 748.1
[1] 1 The change in other assets is driven by the cost of reinsurance associated with the second phase of our Closed Block individual disability reinsurance transaction which was completed in the first quarter of 2021. In accordance with the provisions of the ASU related to non-contemporaneous reinsurance, we were then required to establish the ceded reserves using an upper-medium grade fixed-income instrument as of the reinsurance transaction date in March 2021 which resulted in higher ceded reserves compared to that which was reported historically.

Parent Company Balance Sheet Ca

Parent Company Balance Sheet Captions (Detail) - $ / shares	Dec. 31, 2023	Dec. 31, 2022
Stockholders' Equity, Number of Shares, Par Value and Other Disclosure
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	194,588,625	308,306,490
Treasury Stock, Shares at Cost	1,216,528	110,551,977

Parent Company Statement of Inc

Parent Company Statement of Income (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Condensed Income Statements, Captions
Other Income	$ 279.2	$ 261.1	$ 242.9
Total Revenue	12,385.9	11,984.1	12,007.8
Cost Related to Early Retirement of Debt	0	4.2	67.3
Income Tax Expense (Benefit)	356.3	342.8	279.6
Net Income	1,283.8	1,407.2	981
Other Comprehensive Income (Loss), Net of Tax	140.3	1,716.3	1,145.6
Comprehensive Income (Loss)	1,424.1	3,123.5	2,126.6
Parent Company
Condensed Income Statements, Captions
Other Income	90.3	81.8	53.5
Total Revenue	1,671.4	1,411.4	1,682.9
Interest and Debt Expense	194.8	188.5	185.9
Cost Related to Early Retirement of Debt	0	4.2	67.3
Other Expenses	54.2	35.6	39.1
Operating Expenses, Total	249	228.3	292.3
Income Before Income Tax	1,422.4	1,183.1	1,390.6
Income Tax Expense (Benefit)	(9.5)	14.7	(24.1)
Income of Parent Company	1,431.9	1,168.4	1,414.7
Equity in Undistributed Earnings (Loss) of Subsidiaries	(148.1)	238.8	(433.7)
Net Income	1,283.8	1,407.2	981
Other Comprehensive Income (Loss), Net of Tax	140.3	1,716.3	1,145.6
Comprehensive Income (Loss)	1,424.1	3,123.5	2,126.6
Parent Company | Cash Dividend
Condensed Income Statements, Captions
Dividends from Subsidiaries	1,581.1	1,306.6	909.8
Parent Company | Non-Cash Dividend
Condensed Income Statements, Captions
Dividends from Subsidiaries	$ 0	$ 23	$ 719.6

Parent Company Cash Flow Statem

Parent Company Cash Flow Statement (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash Flows from Operating Activities
Cash Provided by Operating Activities	$ 1,202.8	$ 1,418.7	$ 1,387.5
Cash Flows from Investing Activities
Proceeds from Maturities of Fixed Maturity Securities	1,578.1	1,532.5	2,611.4
Proceeds from Sales and Maturities of Other Investments	360	445.9	403.1
Purchase of Fixed Maturity Securities	(2,991.4)	(2,835.3)	(4,106.3)
Purchase of Other Investments	(361.2)	(482.9)	(606.8)
Net Sales (Purchases) of Short-term Investments	(141)	(22.6)	76.5
Net Purchases of Property and Equipment	(134.8)	(102.2)	(110.3)
Cash Used by Investing Activities	(725.9)	(955.9)	(1,340.6)
Cash Flows from Financing Activities
Short-term Debt Repayment	(2)	0	0
Issuance of Long-term Debt	0	349.2	588.1
Long-term Debt Repayment	0	(364)	(500)
Cost Related to Early Retirement of Debt	0	3.6	62.8
Issuance of Common Stock	5.2	4	3.4
Repurchase of Common Stock	(250.1)	(200.1)	(50)
Dividends Paid to Stockholders	(277.1)	(254.2)	(239.4)
Other, Net	(1.1)	(2.9)	4
Cash Used by Financing Activities	(450.1)	(418.6)	(168.9)
Net Increase (Decrease) in Cash and Bank Deposits	26.8	44.2	(122)
Parent Company
Cash Flows from Operating Activities
Cash Provided by Operating Activities	1,548	1,250.2	861
Cash Flows from Investing Activities
Proceeds from Maturities of Fixed Maturity Securities	97.1	192.1	245.5
Proceeds from Sales and Maturities of Other Investments	23.9	7.4	20.1
Purchase of Fixed Maturity Securities	(44.5)	(102.7)	(2)
Purchase of Other Investments	(23.4)	(32)	(0.9)
Net Sales (Purchases) of Short-term Investments	(104.4)	(209.6)	(465)
Cash Distributions to Subsidiaries	(854.5)	(540.2)	(300.9)
Net Purchases of Property and Equipment	(113.1)	(94)	(91.3)
Cash Used by Investing Activities	(1,018.9)	(779)	(594.5)
Cash Flows from Financing Activities
Short-term Debt Repayment	(2)	0	0
Issuance of Long-term Debt	0	349.2	588.1
Long-term Debt Repayment	0	(364)	(500)
Cost Related to Early Retirement of Debt	0	3.6	62.8
Issuance of Common Stock	5.2	4	3.4
Repurchase of Common Stock	(250.1)	(200.1)	(50)
Dividends Paid to Stockholders	(277.1)	(254.2)	(239.4)
Other, Net	0	0.7	(1.6)
Cash Used by Financing Activities	(524)	(468)	(262.3)
Net Increase (Decrease) in Cash and Bank Deposits	$ 5.1	$ 3.2	$ 4.2

Schedule III Supplementary In_2

Schedule III Supplementary Insurance Information (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Supplementary Insurance Information, by Segment
Deferred Acquisition Costs		$ 2,714.5	$ 2,560
Reserves for Future Policy Contract Benefits		40,009.4	38,577.1
Policyholder Account Balances		5,667.7	5,740.2
Unearned Premiums		380.2	365.5
Premium Income		10,046	9,616.5	$ 9,475
Net Investment Income	[1]	2,096.7	2,122.2	2,213.2
Benefits and Change in Reserves for Future Benefits		7,257.1	6,994.6	7,553.4
Amortization of Deferred Acquisition Costs		481.4	421.1	452.1
All Other Expenses	[2]	3,007.3	2,818.4	2,741.7
Unum US
Supplementary Insurance Information, by Segment
Deferred Acquisition Costs		1,232.2	1,185.1
Reserves for Future Policy Contract Benefits		9,419.1	9,710.3
Policyholder Account Balances		678.1	679.7
Unearned Premiums		54.6	55.8
Premium Income		6,579.2	6,251.4	6,072
Net Investment Income	[1]	639.9	676.3	721.6
Benefits and Change in Reserves for Future Benefits	[3]	3,808.5	3,970.9	4,430.3
Amortization of Deferred Acquisition Costs		267.6	240.9	285.9
All Other Expenses	[2]	1,879.2	1,768.8	1,616.8
Premiums Written	[4]	4,634.3	4,335.7	4,168.9
Unum International
Supplementary Insurance Information, by Segment
Deferred Acquisition Costs		46.9	37
Reserves for Future Policy Contract Benefits		2,305.3	2,063.3
Policyholder Account Balances		0	0
Unearned Premiums		151.4	130.4
Premium Income		825.2	718.8	717
Net Investment Income	[1]	137.2	170.1	132.7
Benefits and Change in Reserves for Future Benefits	[3]	579.8	549.6	553
Amortization of Deferred Acquisition Costs		8.4	8.2	7
All Other Expenses	[2]	235.6	190.4	180.4
Premiums Written	[4]	544.4	504.1	520.6
Colonial Life
Supplementary Insurance Information, by Segment
Deferred Acquisition Costs		1,435.4	1,337.9
Reserves for Future Policy Contract Benefits		1,997.8	1,858.4
Policyholder Account Balances		869.8	869.1
Unearned Premiums		44.5	42.7
Premium Income		1,726.1	1,702	1,690.2
Net Investment Income	[1]	153.5	152.7	172
Benefits and Change in Reserves for Future Benefits	[3]	798.1	826.1	911.7
Amortization of Deferred Acquisition Costs		205.4	172	159.2
All Other Expenses	[2]	396.5	389.6	364.5
Premiums Written	[4]	1,221.8	1,221.8	1,223.3
Closed Block
Supplementary Insurance Information, by Segment
Deferred Acquisition Costs		0	0
Reserves for Future Policy Contract Benefits		26,287.2	24,945.1
Policyholder Account Balances		4,119.8	4,191.4
Unearned Premiums		129.7	136.6
Premium Income		915.5	944.3	995.8
Net Investment Income	[1]	1,066.3	1,070.6	1,159
Benefits and Change in Reserves for Future Benefits	[3]	2,070.7	1,648	1,658.4
Amortization of Deferred Acquisition Costs		0	0	0
All Other Expenses	[2]	246.5	248	274.7
Premiums Written	[4]	904.2	936.8	983
Corporate and Other Segment
Supplementary Insurance Information, by Segment
Premium Income		0	0	0
Net Investment Income	[1]	99.8	52.5	27.9
Benefits and Change in Reserves for Future Benefits		0	0	0
Amortization of Deferred Acquisition Costs		0	0	0
All Other Expenses	[2]	249.5	221.6	305.3
Premiums Written	[4]	0	0	0
Closed Block Individual Disability Reinsurance Transaction
Supplementary Insurance Information, by Segment
Amortization of Prepaid Reinsurance Premium		44.1	50.3	69.8
Operating Segments | Closed Block Individual Disability Reinsurance Transaction
Supplementary Insurance Information, by Segment
Non-Contemporaneous Reinsurance		$ 34.8	34.4	$ 32.9
Amortization of Prepaid Reinsurance Premium			$ 50.3
[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] Includes commissions, interest and debt expense, 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. Also included in all other expenses were the following: • In 2023, 2022, and 2021 the amortization of the cost of reinsurance of $44.1 million, $50.3 million, and $69.8 million respectively, in the Closed Block segment. • In 2021, an impairment loss of $12.1 million was recorded in our Corporate segment for previously capitalized internal-use software that we no longer plan to utilize. • In 2021, costs related to early retirement of debt of $67.3 million in the Corporate segment. • In 2021, transaction costs of $6.2 million related to the Closed Block individual disability reinsurance transaction. • In 2021, a right-of-use asset impairment of $13.9 million related to one of our operating leases for office space that we do not plan to continue using to support general operations in the Corporate segment. • In 2023, reserve assumption updates resulting in a net decrease in policy benefits including remeasurement gain or loss in the Unum US and Colonial Life segments of $128.8 million and $80.7 million, respectively and a net increase in policy benefits including remeasurement gain or loss in the Unum International and Closed Block segments of $17.9 million and $368.8 million, respectively. • In 2022, reserve assumption updates resulting in a net decrease in policy benefits including remeasurement gain or loss in the Unum US, Unum International, Colonial Life, and Closed Block segments of $170.8 million, $7.6 million, $55.2 million, and $9.7 million, respectively. • In 2021, reserve assumption updates resulting in a net decrease in policy benefits including remeasurement gain or loss in the Unum US, Unum International, and Colonial Life segments of $231.7 million, $4.2 million, and $23.5 million, respectively and a net increase in policy benefits including remeasurement gain or loss in the Closed Block segment of $24.4 million. • In 2023, 2022, and 2021 the impact of non-contemporaneous reinsurance of $34.8 million, $34.4 million, and $32.9 million respectively, in the Closed Block segment.

Schedule IV Reinsurance (Detail

Schedule IV Reinsurance (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Reinsurance Premiums for Insurance Companies, by Product Segment
Direct Premiums, Life Insurance in Force	$ 1,079,042.5	$ 1,057,312.2	$ 1,007,562.2
Ceded Premiums, Life Insurance in Force	21,210.7	35,773.9	37,794.6
Assumed Premiums, Life Insurance in Force	921.6	931.9	920.3
Premiums, Net, Life Insurance in Force	$ 1,058,753.4	$ 1,022,470.2	$ 970,687.9
Life Insurance in Force Premiums, Percentage Assumed to Net	0.10%	0.10%	0.10%
Gross Amount	$ 10,286.8	$ 9,893.6	$ 9,736.8
Reinsurance Ceded	321.2	355.8	352.4
Assumed Premiums Earned	80.4	78.7	90.6
Net Amount	$ 10,046	$ 9,616.5	$ 9,475
Percentage of Amount Assumed to Net	0.80%	0.80%	1%
Life Insurance
Reinsurance Premiums for Insurance Companies, by Product Segment
Gross Amount	$ 2,799	$ 2,704.3	$ 2,544.7
Reinsurance Ceded	157.5	155.1	150.2
Assumed Premiums Earned	6	6.5	7.6
Net Amount	$ 2,647.5	$ 2,555.7	$ 2,402.1
Percentage of Amount Assumed to Net	0.20%	0.30%	0.30%
Accident, Health, and Other Insurance
Reinsurance Premiums for Insurance Companies, by Product Segment
Gross Amount	$ 7,487.8	$ 7,189.3	$ 7,192.1
Reinsurance Ceded	163.7	200.7	202.2
Assumed Premiums Earned	74.4	72.2	83
Net Amount	$ 7,398.5	$ 7,060.8	$ 7,072.9
Percentage of Amount Assumed to Net	1%	1%	1.20%

Schedule V Valuation and Qual_2

Schedule V Valuation and Qualifying Accounts (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Allowance for expected credit losses (deducted from accounts and premiums receivable)
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year		$ 32.5	$ 34.2	$ 38.8
Additions Charged to Costs and Expenses		11.3	10.8	18.2
Deductions	[1]	14.3	12.5	22.8
Balance at End of Year		29.5	32.5	34.2
Allowance for expected credit losses (deducted from reinsurance recoverable)
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year		1.7	2.3	11.7
Additions Charged to Costs and Expenses		0.1	0	0.7
Deductions	[1]	0.1	0.6	10.1
Balance at End of Year		$ 1.7	$ 1.7	$ 2.3
[1] Deductions include amounts deemed to reduce exposure of expected losses on premium and accounts receivables and reinsurance recoverable, amounts deemed uncollectible, and amounts related to fluctuations in the foreign currency exchange rate.