Unum (UNM) 10-K 19 Feb 19 2018 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2018	Feb. 15, 2019	Jun. 30, 2018
Document Document and Entity Information [Abstract]
Entity Registrant Name	Unum Group
Trading Symbol	UNM
Entity Central Index Key	5,513
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Document Type	10-K
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Common Stock, Shares Outstanding		214,625,710
Entity Well-known Seasoned Issuer	Yes
Entity Shell Company	false
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 8.1

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Investments
Fixed Maturity Securities - at fair value (amortized cost: $40,275.2; $39,780.5)	$ 43,011.7	$ 45,457.8
Mortgage Loans	2,295	2,213.2
Policy Loans	3,729.9	3,571.1
Other Long-term Investments	702.9	646.8
Short-term Investments	968.1	1,155.1
Total Investments	50,707.6	53,044
Other Assets
Cash and Bank Deposits	94	77.4
Accounts and Premiums Receivable	1,615.5	1,665.7
Reinsurance Recoverable	4,662.4	4,879.2
Accrued Investment Income	690.6	690.1
Deferred Acquisition Costs	2,309.4	2,184.6
Goodwill	350.3	338.6
Property and Equipment	546.9	504.8
Deferred Income Tax	109.9	0
Other Assets	789	628.7
Total Assets	61,875.6	64,013.1
Liabilities
Policy and Contract Benefits	1,695.7	1,605.2
Reserves for Future Policy and Contract Benefits	44,841.9	45,601.6
Unearned Premiums	363.3	373.1
Other Policyholders' Funds	1,594.8	1,595
Income Tax Payable	24	2.9
Deferred Income Tax	0	199
Short-term Debt	0	199.9
Long-term Debt	2,971.3	2,738.4
Payables for Collateral on Investments	128.1	396.2
Other Liabilities	1,634.7	1,726.9
Total Liabilities	53,253.8	54,438.2
Commitments and Contingent Liabilities - Note 14
Stockholders' Equity
Common Stock, $0.10 par; authorized: 725,000,000 shares; issued: 305,104,548 and 304,448,032 shares	30.5	30.5
Additional Paid-in Capital	2,321.7	2,303.3
Accumulated Other Comprehensive Income (Loss)	(814.2)	127.5
Retained Earnings	9,863.1	9,542.2
Treasury Stock - at cost: 90,551,513 and 81,900,950 shares	(2,779.3)	(2,428.6)
Total Stockholders' Equity	8,621.8	9,574.9
Total Liabilities and Stockholders' Equity	$ 61,875.6	$ 64,013.1

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Investments
Amortized Cost of Fixed Maturity Securities	$ 40,275.2	$ 39,780.5
Stockholders' Equity
Common Stock, Par	$ 0.10	$ 0.10
Common Stock, Authorized	725,000,000	725,000,000
Common Stock, Issued	305,104,548	304,448,032
Treasury Stock, Shares	90,551,513	81,900,950

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue
Premium Income	$ 8,986.1	$ 8,597.1	$ 8,357.7
Net Investment Income	2,453.7	2,451.7	2,459
Realized Investment Gain (Loss)
Other-Than-Temporary Impairment Loss on Fixed Maturity Securities	(17.5)	(8.1)	(30.5)
Net Realized Investment Gain (Loss), Excluding Other-Than-Temporary Impairment Loss on Fixed Maturity Securities	(22)	48.4	54.7
Net Realized Investment Gain (Loss)	(39.5)	40.3	24.2
Other Income	198.2	197.7	205.6
Total Revenue	11,598.5	11,286.8	11,046.5
Benefits and Expenses
Benefits and Change in Reserves for Future Benefits	8,020.4	7,055.7	6,941.8
Commissions	1,108.4	1,060.8	1,026.7
Interest and Debt Expense	167.3	159.9	166
Deferral of Acquisition Costs	(668)	(628)	(592.4)
Amortization of Deferred Acquisition Costs	565.5	527.1	493
Compensation Expense	885.9	852.3	839.1
Other Expenses	891.2	855	824.6
Total Benefits and Expenses	10,970.7	9,882.8	9,698.8
Income Before Income Tax	627.8	1,404	1,347.7
Income Tax
Current	227.4	401.3	385.7
Deferred	(123)	8.5	30.6
Total Income Tax	104.4	409.8	416.3
Net Income	$ 523.4	$ 994.2	$ 931.4
Net Income Per Common Share
Basic	$ 2.38	$ 4.39	$ 3.96
Assuming Dilution	$ 2.38	$ 4.37	$ 3.95

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net Income	$ 523.4	$ 994.2	$ 931.4
Other Comprehensive Income (Loss)
Change in Net Unrealized Gain on Securities Before Adjustment (net of tax expense (benefit) of $(614.2); $328.1; $318.0	(2,314.5)	721.7	661.9
Change in Adjustment to Deferred Acquisition Costs and Reserves for Future Policy and Contract Benefits, Net of Reinsurance (net of tax expense (benefit) of $371.7; $(245.0); $(200.6)	1,411.8	(554.5)	(425.6)
Change in Net Gain on Hedges (net of tax benefit of $8.2; $24.4; $25.4)	(31.7)	(45.2)	(50.5)
Change in Foreign Currency Translation Adjustment (net of tax benefit of $0.6; $-; $-)	(50.7)	99.5	(180.4)
Change in Unrecognized Pension and Postretirement Benefit Costs (net of tax expense (benefit) of $17.0; $(8.3); $(34.2))	60.9	(43)	(72.5)
Total Other Comprehensive Income (Loss)	(924.2)	178.5	(67.1)
Comprehensive Income	$ (400.8)	$ 1,172.7	$ 864.3

CONSOLIDATED STATEMENTS OF CO_2

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Change in Net Unrealized Gain on Securities Before Adjustment, Tax Expense (Benefit)	$ (614.2)	$ 328.1	$ 318
Change in Adjustment to Deferred Acquisition Costs and Reserves for Future Policy and Contract Benefits, Net of Reinsurance, Tax Expense (Benefit)	371.7	(245)	(200.6)
Change in Net Gain on Cash Flow Hedges, Tax Benefit	8.2	24.4	25.4
Change in Foreign Currency Translation Adjustment, Tax Benefit	0.6	0	0
Change in Unrecognized Pension and Postretirement Benefit Costs, Tax Expense (Benefit)	$ 17	$ (8.3)	$ (34.2)

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
Balance at Beginning of Year at Dec. 31, 2015			$ 30.3	$ 2,247.2	$ 16.1	$ 7,995.2	$ (1,624.9)
Increase (Decrease) in Stockholders' Equity
Common Stock Activity			0.1	25.6
Recognition and Measurement of Financial Assets and Financial Liabilities, Reclassification from AOCI to Retained Earnings					0	0
Other Comprehensive Income (Loss)	$ (67.1)				(67.1)
Net Income	931.4					931.4
Dividends to Stockholders (per common share: $0.98; $0.86; $0.77)						(182.6)
Purchases of Treasury Stock	(403.3)	[1]					(403.3)
Balance at End of Year at Dec. 31, 2016	8,968		30.4	2,272.8	(51)	8,744	(2,028.2)
Increase (Decrease) in Stockholders' Equity
Common Stock Activity			0.1	30.5
Recognition and Measurement of Financial Assets and Financial Liabilities, Reclassification from AOCI to Retained Earnings					0	0
Other Comprehensive Income (Loss)	178.5				178.5
Net Income	994.2					994.2
Dividends to Stockholders (per common share: $0.98; $0.86; $0.77)						(196)
Purchases of Treasury Stock	(400.4)	[1]					(400.4)
Balance at End of Year at Dec. 31, 2017	9,574.9		30.5	2,303.3	127.5	9,542.2	(2,428.6)
Increase (Decrease) in Stockholders' Equity
Common Stock Activity			0	18.4
Recognition and Measurement of Financial Assets and Financial Liabilities, Reclassification from AOCI to Retained Earnings	(17.5)				(17.5)	14.5
Other Comprehensive Income (Loss)	(924.2)				(924.2)
Net Income	523.4					523.4
Dividends to Stockholders (per common share: $0.98; $0.86; $0.77)						(217)
Purchases of Treasury Stock	(350.7)	[1]					(350.7)
Balance at End of Year at Dec. 31, 2018	$ 8,621.8		$ 30.5	$ 2,321.7	$ (814.2)	$ 9,863.1	$ (2,779.3)
[1]	Includes commissions of $0.7 million, $0.3 million, and $0.2 million for the years ended December 31, 2018, 2017, and 2016, respectively.

CONSOLIDATED STATEMENTS OF ST_2

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Retained Earnings
Dividends to Stockholders (per common share: $0.98; $0.86; $0.77)	$ 0.980	$ 0.860	$ 0.770

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash Flows from Operating Activities
Net Income	$ 523.4	$ 994.2	$ 931.4
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities
Change in Receivables	(4.7)	(101.8)	(167.3)
Change in Deferred Acquisition Costs	(102.5)	(100.9)	(99.4)
Change in Insurance Reserves and Liabilities	1,193.1	441.9	368.2
Change in Income Taxes	(39.1)	25.6	34.7
Change in Other Accrued Liabilities	(10.1)	14.6	125.8
Non-cash Components of Net Investment Income	(211.1)	(200.1)	(187.7)
Net Realized Investment (Gain) Loss	39.5	(40.3)	(24.2)
Depreciation	101.4	103.4	101.7
Other, Net	46.6	27.5	38.4
Net Cash Provided by Operating Activities	1,536.5	1,164.1	1,121.6
Cash Flows from Investing Activities
Proceeds from Sales of Fixed Maturity Securities	642.5	436.3	911.5
Proceeds from Maturities of Fixed Maturity Securities	2,815.4	2,560.8	2,197.8
Proceeds from Sales and Maturities of Other Investments	454	257.9	331.3
Purchase of Fixed Maturity Securities	(3,861.7)	(2,808.5)	(3,362.8)
Purchase of Other Investments	(623.2)	(474.3)	(576)
Net Sales (Purchases) of Short-term Investments	200.5	(356.4)	6.3
Net Increase (Decrease) in Payables for Collateral on Investments	(268.1)	(9.8)	(9.4)
Acquisition of Business (Net of Cash Acquired)	(145.4)	0	(129.2)
Net Purchases of Property and Equipment	(144.1)	(105.3)	(85)
Net Cash Used by Investing Activities	(930.1)	(499.3)	(715.5)
Cash Flows from Financing Activities
Short-term Debt Repayment	(200)	0	0
Issuance of Long-term Debt	290.7	0	609.1
Long-term Debt Repayment	(60)	(63.5)	(414)
Issuance of Common Stock	4.6	10.8	8.5
Repurchase of Common Stock	(356.2)	(401.8)	(405.2)
Dividends Paid to Stockholders	(215.6)	(196)	(182.6)
Other, Net	(53.3)	(37.3)	(34.4)
Net Cash Used by Financing Activities	(589.8)	(687.8)	(418.6)
Net Increase (Decrease) in Cash and Bank Deposits	16.6	(23)	(12.5)
Cash and Bank Deposits at Beginning of Year	77.4	100.4	112.9
Cash and Bank Deposits at End of Year	$ 94	$ 77.4	$ 100.4

Significant Accounting Policies

Significant Accounting Policies	12 Months Ended
	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Significant Accounting Policies	Basis of Presentation : The accompanying consolidated financial statements of Unum Group and its subsidiaries (the Company) have been prepared in accordance with U.S. generally accepted accounting principles (GAAP). Such accounting principles differ from statutory accounting principles (see Note 15). Intercompany transactions have been eliminated. Description of Business : We are a leading provider of financial protection benefits in the United States and the United Kingdom. Our products include disability, life, accident, critical illness, dental and vision, and other related services. We market our products primarily through the workplace. We have three principal operating business segments: Unum US, Unum International, and Colonial Life. Our other reporting segments are Closed Block and Corporate. See Note 13 for further discussion of our operating segments. Use of Estimates : The preparation of financial statements in conformity with GAAP requires us to make estimates and assumptions that affect amounts reported in the financial statements and accompanying notes. Such estimates and assumptions could change in the future as more information becomes known, which could impact the amounts reported and disclosed herein. Fixed Maturity Securities : Fixed maturity securities include long-term bonds and redeemable preferred stocks. Our fixed maturity securities are classified as available-for-sale and reported at fair value. Changes in the fair value of available-for-sale fixed maturity securities, except for amounts related to other-than-temporary impairment losses recognized in earnings, are reported as a component of other comprehensive income. These amounts are net of income tax and valuation adjustments to deferred acquisition costs and reserves for future policy and contract benefits which would have been recorded had the related unrealized gain or loss on these securities been realized. Interest income is recorded as part of net investment income when earned, using an effective yield method giving effect to amortization of premium and accretion of discount. Included within fixed maturity securities are mortgage-backed and asset-backed securities. We recognize investment income on these securities using a constant effective yield based on projected prepayments of the underlying loans and the estimated economic life of the securities. Actual prepayment experience is reviewed periodically, and effective yields are recalculated when differences arise between prepayments originally projected and the actual prepayments received and currently projected. The effective yield is recalculated on a retrospective basis, and the adjustment is reflected in net investment income. For fixed maturity securities on which collection of investment income is uncertain, we discontinue the accrual of investment income and recognize investment income when interest and dividends are received. Payment terms specified for fixed maturity securities may include a prepayment penalty for unscheduled payoff of the investment. Prepayment penalties are recognized as investment income when received. In determining when a decline in fair value below amortized cost of a fixed maturity security is other than temporary, 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 are other than temporary. The significance of the decline in value and the length of time during which there has been a significant decline are also important factors, but we generally do not record an impairment loss based solely on these two factors, since often other more relevant factors will impact our evaluation of a security. If we determine that the decline in value of an investment is other than temporary, the investment is written down to fair value, and an impairment loss is recognized in the current period, either in earnings or in both earnings and other comprehensive income, as applicable. Other-than-temporary impairment losses on fixed maturity securities which we intend to sell or more likely than not will be required to sell before recovery in value are recognized in earnings and equal the entire difference between the security's amortized cost basis and its fair value. For securities 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, other-than-temporary impairment losses recognized in earnings generally represent 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. For fixed maturity securities for which we have recognized an other-than-temporary impairment loss through earnings, if through subsequent evaluation there is a significant increase in expected cash flows, the difference between the new amortized cost basis and the cash flows expected to be collected is accreted as net investment income over the remaining life of the investment. See Notes 2 and 3. Mortgage Loans : Mortgage loans are generally held for investment and are carried at amortized cost less an allowance for probable 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. If we determine that it is probable we will be unable to collect all amounts due under the contractual terms of a mortgage loan, we establish an allowance for credit loss. If we expect to foreclose on the property, the amount of the allowance typically equals the excess carrying value of the mortgage loan over the fair value of the underlying collateral. If we expect to retain the mortgage loan until payoff, the allowance equals the excess carrying value of the mortgage loan over the expected future cash flows of the loan. Additions and reductions to our allowance for credit losses on mortgage loans are reported as a component of net realized investment gains and losses. We do not purchase mortgage loans with existing credit impairments. See Note 3. Policy Loans : Policy loans are presented at unpaid balances directly related to policyholders. Interest income is accrued on the principal amount of the loan based on the loan's contractual interest rate. Included in policy loans are $3,449.3 million and $3,307.5 million of policy loans ceded to reinsurers at December 31, 2018 and 2017 , respectively. Other Long-term Investments : Other long-term investments are comprised primarily of tax credit partnerships and private equity partnerships. Tax credit partnerships in which we have invested were formed for the purpose of investing in the construction and rehabilitation of low-income housing. Because the partnerships are structured such that there is no return of principal, the primary sources of investment return from our tax credit partnerships are tax credits and tax benefits derived from passive losses on the investments, both of which may exhibit variability over the life of the investment. These partnerships are accounted for using either the proportional or the effective yield method, depending primarily on whether the tax credits are guaranteed through a letter of credit, a tax indemnity agreement, or another similar arrangement. Tax credits received from these partnerships are reported in our consolidated statements of income as either a reduction of premium tax or a reduction of income tax. The amortization of the principal amount invested in these partnerships is reported as a component of either premium tax or income tax. Our investments in private equity partnerships are passive in nature and represent funds that are primarily invested in private credit, private equity, and real assets. We account for our investments in these partnerships using either the equity method or at fair value through net income depending on the level of ownership and the degree of our influence over partnership operating and financial policies. For investments in partnerships accounted for under the equity method, we report our investments at our share of the partnership's net asset value (NAV) and record our portion of partnership earnings is recorded 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. See notes 2 and 3 for further discussion of our other long-term investments. Short-term Investments : Short-term investments are carried at cost. Short-term investments include investments maturing within one year of purchase, such as corporate commercial paper and U.S. Treasury bills, bank term deposits, and other cash accounts and cash equivalents earning interest. Cash and Bank Deposits : Cash and bank deposits include cash on hand and non-interest bearing cash and deposit accounts. Derivative Financial Instruments : Derivative financial instruments (including certain derivative instruments embedded in other contracts) are recognized as either other long-term investments or other liabilities in our consolidated balance sheets and are reported at fair value. The accounting for a derivative depends on whether it has been designated and qualifies as part of a hedging relationship, and further, on the type of hedging relationship. To qualify for hedge accounting, at the inception of the hedging transaction, we formally document the risk management objective and strategy for undertaking the hedging transaction, as well as the designation of the hedge as either a fair value hedge or a cash flow hedge. Included in this documentation is how the hedging instrument is expected to hedge the designated risk(s) related to specific assets or liabilities on the balance sheet or to specific forecasted transactions as well as a description of the method that will be used to retrospectively and prospectively assess the hedging instrument's effectiveness. A derivative designated as a hedging instrument must be assessed as being highly effective in offsetting the designated risk(s) of the hedged item. Hedge effectiveness is formally assessed at inception and periodically throughout the life of the designated hedging relationship, using qualitative and quantitative methods. Qualitative methods include comparison of critical terms of the derivative to the hedged item. Quantitative methods include regression or other statistical analysis of changes in fair value or cash flows associated with the hedge relationship. Changes in the fair value of a derivative designated as a fair value hedge and changes in the fair value of the hedged item attributable to the risk being hedged are recognized in earnings as a component of net realized investment gain or loss during the period of change in fair value. For gains or losses on the derivative instrument that are excluded from the assessment of hedge effectiveness, those gains and losses are recognized in other comprehensive income or loss and amortized into earnings in the same income statement line as the related hedged item. The gain or loss on the termination of a fair value hedge is recognized in earnings as a component of net realized investment gain or loss during the period in which the termination occurs. When interest rate swaps are used in hedge accounting relationships, periodic settlements are recorded in the same income statement line as the related settlements of the hedged items. Changes in the fair value of a derivative designated as a cash flow hedge are reported in other comprehensive income and reclassified into earnings and reported on the same income statement line item as the hedged item and in the same period or periods during which the hedged item affects earnings. The gain or loss on the termination of an effective cash flow hedge is reported in other comprehensive income and reclassified into earnings and reported on the same income statement line item as the hedged item and in the same period or periods during which the hedged item affects earnings. Gains or losses on the termination of ineffective fair value or cash flow hedges are reported in earnings as a component of net realized investment gain or loss. In the event a hedged item is disposed of or the anticipated transaction being hedged is no longer likely to occur, we will terminate the related derivative and recognize the gain or loss on termination in current earnings as a component of net realized investment gain or loss. In the event a hedged item is disposed of subsequent to the termination of the hedging transaction, we reclassify any remaining gain or loss on the hedge out of accumulated other comprehensive income into earnings as a component of the same income statement line item wherein we report the gain or loss on disposition of the hedged item. For a derivative not designated as a hedging instrument, changes in the fair value of the derivative, together with the payment of periodic fees, if applicable, are recognized in earnings as a component of net realized investment gain or loss during the period of change in fair value. Cash flow activity from the settlement of derivative contracts is reported in the consolidated statements of cash flows as a component of proceeds from sales and maturities of other investments. In our consolidated balance sheets, we do not offset fair value amounts recognized for derivatives executed with the same counterparty under a master netting agreement and fair value amounts recognized for the right to reclaim cash collateral or the obligation to return cash collateral arising from those master netting agreements. See Notes 2, 3 and 4. Fair Value Measurement : Certain assets and liabilities are reported at fair value in our consolidated balance sheets and in our notes to our consolidated financial statements. We define fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. Therefore, fair value represents an exit price, not an entry price. The exit price objective applies regardless of our intent and/or ability to sell the asset or transfer the liability at the measurement date. Assets or liabilities with readily available actively quoted prices or for which fair value can be measured from actively quoted prices in active markets generally have more pricing observability and less judgment utilized in measuring fair value. When actively quoted prices are not available, fair values are based on quoted prices in markets that are not active, quoted prices for similar but not identical assets or liabilities, or other observable inputs. If observable inputs are not available, unobservable inputs and/or adjustments to observable inputs requiring management judgment are used to determine fair value. We categorize our assets and liabilities measured at estimated fair value into a three-level hierarchy, based on the significance of the inputs. The fair value hierarchy gives the highest priority to inputs which are unadjusted and represent quoted prices in active markets for identical assets or liabilities (Level 1) and the lowest priority to unobservable inputs (Level 3). See Note 2. Realized Investment Gains and Losses : Realized investment gains and losses are reported as a component of revenue in the consolidated statements of income and are based upon specific identification of the investments sold. See Note 3. Deferred Acquisition Costs : Incremental direct costs associated with the successful acquisition of new or renewal insurance contracts have been deferred. Such costs include commissions, other agency compensation, certain selection and policy issue expenses, and certain field expenses. Acquisition costs that do not vary with the production of new business, such as commissions on group products which are generally level throughout the life of the policy, are excluded from deferral. Deferred acquisition costs are subject to recoverability testing at the time of policy issue and loss recognition testing in subsequent years. Deferred acquisition costs related to non-interest sensitive policies are amortized in proportion to the premium income we expect to receive over the lives of the policies. Deferred acquisition costs related to interest sensitive policies are amortized over the lives of the policies in relation to the present value of estimated gross profits from surrender charges, mortality margins, investment returns, and expense margins. Deviations from projections result in a change to the rate of amortization in the period during which such events occur. Generally, the amortization periods for these policies approximate the estimated lives of the policies. For certain products, policyholders can elect to modify product benefits, features, rights, or coverages by exchanging a contract for a new contract or by amendment, endorsement, or rider to a contract, or by the election of a feature or coverage within a contract. These transactions are known as internal replacement transactions. Internal replacement transactions wherein the modification does not substantially change the policy are accounted for as continuations of the replaced contracts. Unamortized deferred acquisition costs from the original policy continue to be amortized over the expected life of the new policy, and the costs of replacing the policy are accounted for as policy maintenance costs and expensed as incurred. Internal replacement transactions, principally on group contracts, that result in a policy that is substantially changed are accounted for as an extinguishment of the original policy and the issuance of a new policy. Unamortized deferred acquisition costs on the original policy that was replaced are immediately expensed, and the costs of acquiring the new policy are capitalized and amortized in accordance with our accounting policies for deferred acquisition costs. Loss recognition is performed on an annual basis, or more frequently if appropriate, using best estimate assumptions as to future experience as of the date of the test. Insurance contracts are grouped for each major product line within a segment when we perform the loss recognition tests. If loss recognition testing indicates that deferred acquisition costs are not recoverable, the deficiency is charged to expense. Goodwill : Goodwill is the excess of the amount paid to acquire a business over the fair value of the net assets acquired. We review the carrying amount of goodwill for impairment on an annual basis, or more frequently if events or changes in circumstances indicate that the carrying amount might not be recoverable. Goodwill impairment testing compares the fair value of a reporting unit with its carrying amount, including goodwill. The fair values of the reporting units are determined using discounted cash flow models. The critical estimates necessary in determining fair value are projected earnings and the discount rate. We set our discount rate assumption based on an expected risk adjusted cost of capital. If the fair value of the reporting unit to which the goodwill relates is less than the carrying amount of the unamortized goodwill, the impairment charge is determined by calculating the implied fair value of goodwill by assigning the fair value of a reporting unit to all of its assets and liabilities. The carrying amount of goodwill is then reduced with a corresponding charge to expense. 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 $1,151.8 million and $1,067.7 million as of December 31, 2018 and 2017 , 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 $96.7 million and $27.9 million at December 31, 2018 and 2017 , respectively. The accumulated amortization for value of business acquired was $133.0 million and $130.4 million as of December 31, 2018 and 2017 , respectively. The amortization of value of business acquired, which is included in other expenses in the consolidated statements of income, was $6.4 million , $4.8 million , and $5.1 million for the years ended December 31, 2018 , 2017 , and 2016 , respectively. We periodically review the carrying amount of value of business acquired using the same methods used to evaluate deferred acquisition costs. Policy and Contract Benefits : Policy and contract benefits represent amounts paid and expected to be paid based on reported losses and estimates of incurred but not reported losses for non-interest sensitive life and accident and health products. For interest sensitive products, benefits are the amounts paid and expected to be paid on insured claims in excess of the policyholders' policy fund balances. Reserves for Policy and Contract Benefits : Policy reserves represent future policy and contract benefits for claims not yet incurred. Policy reserves for non-interest sensitive life and accident and health products are determined using the net level premium method. The reserves are calculated based upon assumptions as to interest, persistency, morbidity, and mortality that were appropriate at the date of issue. Discount rate assumptions are based on actual and expected net investment returns. Persistency assumptions are based on our actual historical experience adjusted for future expectations. Claim incidence and claim resolution rate assumptions related to morbidity and mortality are based on actual experience or industry standards adjusted as appropriate to reflect our actual experience and future expectations. The assumptions vary by plan, year of issue, and policy duration and include a provision for adverse deviation. Policy reserves for group single premium annuities are developed on a net single premium method. The reserves are calculated based on assumptions as to interest, mortality, and retirement that were appropriate at the date of issue. Mortality assumptions are based upon industry standards adjusted as appropriate to reflect our actual experience and future expectations. The assumptions vary by year of issue. Policy reserves for interest sensitive products are principally policyholder account values. Policy reserves require ongoing loss recognition testing. We perform loss recognition tests on our policy reserves annually, or more frequently if appropriate, using best estimate assumptions as of the date of the test, without a provision for adverse deviation. We group the policy reserves for each major product line within a segment when we perform the loss recognition tests. If the policy reserves determined using these best estimate assumptions are higher than our existing policy reserves net of any deferred acquisition cost balance, the existing policy reserves are increased or deferred acquisition costs are reduced to immediately recognize the deficiency. This becomes the new basis for policy reserves going forward, subject to future loss recognition testing. Claim reserves represent future policy and contract benefits for claims that have been incurred or are estimated to have been incurred but not yet reported to us. Our claim reserves relate primarily to disability and long-term care policies and are calculated based on assumptions as to interest and claim resolution rates that are currently appropriate. Claim resolution rate assumptions are based on our actual experience. The interest rate assumptions used for discounting claim reserves are based on projected portfolio yield rates, after consideration for defaults and investment expenses, for the assets supporting the liabilities for the various product lines. Unlike policy reserves for which assumptions are generally established and locked in at the time of policy issuance, claim reserves are subject to revision as current claim experience and projections of future factors affecting claim experience change. Claim reserves do not include a provision for adverse deviation. See Note 6. Policyholders' Funds : Policyholders' funds represent customer deposits plus interest credited at contract rates. We control interest rate risk by investing in quality assets which have an aggregate duration that closely matches the expected duration of the liabilities. Income Tax : Deferred taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial statement purposes and the amounts used for income tax purposes. Deferred taxes have been measured using enacted statutory income tax rates and laws that are currently in effect. We record adjustments to our deferred taxes resulting from tax rate changes through income as of the date of enactment. We record deferred tax assets for tax positions taken in the U.S. and other tax jurisdictions based on our assessment of whether a position is more likely than not to be sustained upon examination based solely on its technical merits. A valuation allowance is established for deferred tax assets when it is more likely than not that an amount will not be realized. See Note 7. Short-term and Long-term Debt : Debt is generally carried at the unpaid principal balance, net of unamortized discount or premium and deferred debt issuance costs. Short-term debt consists of debt due within the next twelve months, including that portion of debt otherwise classified as long-term. Original issue discount or premium as well as debt issuance costs are recognized as a component of interest expense over the period the debt is expected to be outstanding. The carrying amount of long-term debt that is part of a fair value hedge program includes an adjustment to reflect the effect of the change in fair value attributable to the risk being hedged. Net interest settlements for fair value hedges on our long-term debt are recognized as a component of interest expense. See Note 8. Treasury Stock and Retirement of Common Stock : Treasury stock is reflected as a reduction of stockholders' equity at cost. When shares are retired, the par value is removed from common stock, and the excess of the repurchase price over par is allocated between additional paid-in capital and retained earnings. See Note 10. Revenue Recognition: 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. Fees from our administrative-services only and family medical leave products are reported as other income when services are rendered. Reinsurance : We routinely enter into reinsurance agreements with other insurance companies to spread risk and thereby limit losses from large exposures. For each of our reinsurance agreements, we determine if the agreement provides indemnification against loss or liability relating to insurance risk in accordance with applicable accounting standards. If we determine that a reinsurance agreement does not expose the reinsurer to a reasonable possibility of a significant loss from insurance risk, we record the agreement using the deposit method of accounting. Reinsurance activity is accounted for on a basis consistent with the terms of the reinsurance contracts and the accounting used for the original policies issued. Premium income and benefits and change in reserves for future benefits are presented in our consolidated statements of income net of reinsurance ceded. Ceded liabilities for policy and contract benefits, future policy and contract benefits, and unearned premiums are reported on a gross basis in our consolidated balance sheets, as are ceded policy loans. Our reinsurance recoverable includes the balances due from reinsurers under the terms of the reinsurance agreements for these ceded balances as well as settlement amounts currently due. Where applicable, gains or losses on reinsurance transactions are 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. The deferred gain on reinsurance included in other liabilities in our consolidated balance sheets at December 31, 2018 and 2017 was $12.5 million and $17.7 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. In the event that reinsurers do not meet their obligations to us under the terms of the reinsurance agreements, certain amounts reported in our reinsurance recoverable could become uncollectible, in which case the reinsurance recoverable balances are stated net of allowances for uncollectible reinsurance. See Note 12. Premium Tax Expense : Premium tax expense is included in other expenses in the consolidated statements of income. For the years ended December 31, 2018 , 2017 , and 2016 , premium tax expense was $155.8 million , $158.0 million , and $152.5 million , respectively. Stock-Based Compensation : The cost of stock-based compensation is generally measured based on the grant-date fai

Fair Values of Financial Instru

Fair Values of Financial Instruments	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Fair Values of Financial Instruments	Fair Value Measurements for Financial Instruments Carried at Fair Value We report fixed maturity securities, which are classified as available-for-sale securities, derivative financial instruments, and unrestricted equity securities at fair value in our consolidated balance sheets. We report our investments in private equity partnerships at our share of the partnerships' net asset value per share or its equivalent (NAV) as a practical expedient for fair value. See Note 1. The degree of judgment utilized in measuring the fair value of financial instruments generally correlates to the level of pricing observability. Financial instruments with readily available active quoted prices or for which fair value can be measured from actively quoted prices in active markets generally have more pricing observability and less judgment utilized in measuring fair value. An active market for a financial instrument is a market in which transactions for an asset or a similar asset occur with sufficient frequency and volume to provide pricing information on an ongoing basis. A quoted price in an active market provides the most reliable evidence of fair value and should be used to measure fair value whenever available. Conversely, financial instruments rarely traded or not quoted have less observability and are measured at fair value using valuation techniques that require more judgment. Pricing observability is generally impacted by a number of factors, including the type of financial instrument, whether the financial instrument is new to the market and not yet established, the characteristics specific to the transaction, and overall market conditions. We classify financial instruments in accordance with a fair value hierarchy consisting of three levels based on the observability of valuation inputs: • Level 1 - the highest category of the fair value hierarchy classification wherein inputs are unadjusted and represent quoted prices in active markets for identical assets or liabilities at the measurement date. • Level 2 - valued using inputs (other than prices included in Level 1) that are either directly or indirectly observable for the asset or liability through correlation with market data at the measurement date and for the duration of the instrument's anticipated life. • Level 3 - the lowest category of the fair value hierarchy and reflects the judgment of management regarding what market participants would use in pricing assets or liabilities at the measurement date. Financial assets and liabilities categorized as Level 3 are generally those that are valued using unobservable inputs to extrapolate an estimated fair value. Valuation Methodologies of Financial Instruments Measured at Fair Value Valuation techniques used for assets and liabilities accounted for at fair value are generally categorized into three types. The market approach uses prices and other relevant information from market transactions involving identical or comparable assets or liabilities. The income approach converts future amounts, such as cash flows or earnings, to a single present amount, or a discounted amount. The cost approach is based upon the amount that currently would be required to replace the service capacity of an asset, or the current replacement cost. We use valuation techniques that are appropriate in the circumstances and for which sufficient data are available that can be obtained without undue cost and effort. In some cases, a single valuation technique will be appropriate (for example, when valuing an asset or liability using quoted prices in an active market for identical assets or liabilities). In other cases, multiple valuation techniques will be appropriate. If we use multiple valuation techniques to measure fair value, we evaluate and weigh the results, as appropriate, considering the reasonableness of the range indicated by those results. A fair value measurement is the point within that range that is most representative of fair value in the circumstances. The selection of the valuation method(s) to apply considers the definition of an exit price and depends on the nature of the asset or liability being valued. For assets and liabilities accounted for at fair value, we generally use valuation techniques consistent with the market approach, and to a lesser extent, the income approach. We believe the market approach provides more observable data than the income approach, considering the type of investments we hold. Our fair value measurements could differ significantly based on the valuation technique and available inputs. When using a pricing service, we obtain the vendor's pricing documentation to ensure we understand their methodologies. We periodically review and approve the selection of our pricing vendors to ensure we are in agreement with their current methodologies. When markets are less active, brokers may rely more on models with inputs based on the information available only to the broker. Our internal investment management professionals, which include portfolio managers and analysts, monitor securities priced by brokers and evaluate their prices for reasonableness based on benchmarking to available primary and secondary market information. In weighing a broker quote as an input to fair value, we place less reliance on quotes that do not reflect the result of market transactions. We also consider the nature of the quote, particularly whether the quote is a binding offer. 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 2018 , 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 2017 . Fixed Maturity and Equity Securities We use observable and unobservable inputs in measuring the fair value of our fixed maturity and equity securities. For securities categorized as Level 1, fair values equal active Trade Reporting and Compliance Engine (TRACE) pricing or unadjusted broker market maker prices. For securities categorized as Level 2 or Level 3, inputs that may be used in valuing each class of securities at any given time period are disclosed below. Actual inputs used to determine fair values will vary for each reporting period depending on the availability of inputs which may, at times, be affected by the lack of market liquidity. Level 2 Level 3 Instrument Observable Inputs Unobservable Inputs United States Government and Government Agencies and Authorities Valuation Method Principally the market approach Not applicable Valuation Techniques / Inputs Prices obtained from external pricing services States, Municipalities, and Political Subdivisions Valuation Method Principally the market approach Principally the market approach Valuation Techniques / Inputs Prices obtained from external pricing services Analysis of similar bonds, adjusted for comparability Relevant reports issued by analysts and rating agencies Non-binding broker quotes Audited financial statements Security and issuer level spreads 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 Non-binding broker quotes Call provisions Security and issuer level spreads Public Utilities Valuation Method Principally the market and income approaches Principally the market and income approaches Valuation Techniques / Inputs TRACE pricing Change in benchmark reference Level 2 Level 3 Instrument Observable Inputs Unobservable Inputs Public Utilities - Continued Prices obtained from external pricing services Analysis of similar bonds, adjusted for comparability Non-binding broker quotes Discount for size - illiquidity Benchmark yields Non-binding broker quotes Transactional data for new issuances and secondary trades Lack of marketability Security cash flows and structures Security and issuer level spreads Recent issuance / supply Volatility of credit Matrix pricing Matrix pricing 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 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 Non-binding broker quotes Security cash flows and structures Security and issuer level spreads Underlying collateral Prepayment speeds/loan performance/delinquencies Relevant reports issued by analysts and rating agencies Audited financial statements All Other Corporate Bonds Valuation Method Principally the market and income approaches Principally the market and income approaches Valuation Techniques / Inputs TRACE pricing Change in benchmark reference Prices obtained from external pricing services Analysis of similar bonds, adjusted for comparability Non-binding broker quotes Discount for size - illiquidity Benchmark yields Non-binding broker quotes Transactional data for new issuances and secondary trades Lack of marketability Security cash flows and structures Security and issuer level spreads Recent issuance / supply Volatility of credit Matrix pricing Matrix pricing Level 2 Level 3 Instrument Observable Inputs Unobservable Inputs All Other Corporate Bonds - Continued 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 Non-binding broker quotes Benchmark yields Comparative bond analysis Call provisions Relevant reports issued by analysts and rating agencies Audited financial statements 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 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 obtained to ensure they are consistent with a variety of observable market inputs and to verify the validity of a security's price. In the event we receive a vendor's market price that does not appear reasonable based on our market analysis, we may challenge the price and request further information about the assumptions and methodologies used by the vendor to price the security. We may change the vendor price based on a better data source such as an actual trade. We also review all price changes from the prior month which fall outside a predetermined corridor. 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 combining matrix pricing with vendor purchased software programs, 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, 2018 , approximately 11.7 percent of our fixed maturity securities were valued using active trades from TRACE pricing or broker market maker prices for which there was current market activity in that specific security (comparable to receiving one binding quote). The prices obtained were not adjusted, and the assets were classified as Level 1. The remaining 88.3 percent of our fixed maturity securities were valued based on non-binding quotes or other observable and unobservable inputs, as discussed below: • 75.0 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. • 3.6 percent of our fixed maturity securities were valued based on one or more non-binding broker quotes, if validated by observable market data, or on TRACE prices for identical or similar assets absent current market activity. 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. • 9.7 percent of our fixed maturity securities were valued based on prices of comparable securities, matrix pricing, market models, and/or internal models or were valued based on non-binding quotes with no other observable market data. These assets were classified as either Level 2 or Level 3, with the categorization dependent on whether there was other observable market data. Derivatives Fair values for derivatives other than embedded derivatives in modified coinsurance arrangements are based on market quotes or pricing models and represent the net amount of cash we would have paid or received if the contracts had been settled or closed as of the last day of the period. We analyze credit default swap spreads relative to the average credit spread embedded within the LIBOR-setting syndicate in determining the effect of credit risk on our derivatives' fair values. If net counterparty credit risk for a derivative asset is determined to be material and is not adequately reflected in the LIBOR-based fair value obtained from our pricing sources, we adjust the valuations obtained from our pricing sources. For purposes of valuing net counterparty risk, we measure the fair value of a group of financial assets and financial liabilities on the basis of the price that would be received to sell a net long position or transfer a net short position for a particular risk exposure in an orderly transaction between market participants at the measurement date under current market conditions. In regard to our own credit risk component, we adjust the valuation of derivative liabilities wherein the counterparty is exposed to our credit risk when the LIBOR-based valuation of our derivatives obtained from pricing sources does not effectively include an adequate credit component for our own credit risk. Fair values for our embedded derivative in a modified coinsurance arrangement are estimated using internal pricing models and represent the hypothetical value of the duration mismatch of assets and liabilities, interest rate risk, and third party credit risk embedded in the modified coinsurance arrangement. We consider transactions in inactive markets to be less representative of fair value. We use all available observable inputs when measuring fair value, but when significant unobservable inputs are used, we classify these assets or liabilities as Level 3. Private Equity Partnerships Our private equity partnerships represent funds that are primarily invested in private credit, private equity, and real assets, as described below. Distributions received from the funds arise from income generated by the underlying investments as well as the liquidation of the underlying investments. There is generally not a public market for these investments. The following table presents additional information about our private equity partnerships as of December 31, 2018 , including commitments for additional investments which may or may not be funded: Investment Category Fair Value Redemption Term / Redemption Notice Unfunded Commitments (in millions of dollars) (in millions of dollars) Private Credit (a) $ 168.6 Not redeemable $ 99.5 25.7 Initial 2 year lock on each new investment / Quarterly after 2 year lock with 90 days notice 10.3 Total Private Credit 194.3 109.8 Private Equity (b) 128.3 Not redeemable 169.5 Real Assets (c) 131.0 Not redeemable 106.0 30.2 Quarterly / 90 days notice — Total Real Assets 161.2 106.0 Total Partnerships $ 483.8 $ 385.3 (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, 2018 , the estimated remaining life of the investments that do not allow for redemptions is approximately 20 percent in the next 3 years, 46 percent during the period from 3 to 5 years, 30 percent during the period from 5 to 10 years, and 4 percent after the period of 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, 2018 , the estimated remaining life of the investments that do not allow for redemptions is approximately 40 percent in the next 3 years, 9 percent during the period from 3 to 5 years, 49 percent during the period from 5 to 10 years, 1 percent during the period from 10 to 15 years, and 1 percent after the period of 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, 2018 , the estimated remaining life of the investments that do not allow for redemptions is approximately 2 percent in the next 3 years, 19 percent during period from 3 to 5 years, 75 percent during the period from 5 to 10 years, and 4 percent during the period from 10 to 15 years. 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, 2018 Level 1 Level 2 Level 3 NAV Total (in millions of dollars) Assets Fixed Maturity Securities United States Government and Government Agencies and Authorities $ 513.4 $ 1,301.0 $ — $ — $ 1,814.4 States, Municipalities, and Political Subdivisions — 2,424.2 — — 2,424.2 Foreign Governments — 952.3 31.4 — 983.7 Public Utilities 286.4 7,041.7 84.7 — 7,412.8 Mortgage/Asset-Backed Securities — 1,582.7 — — 1,582.7 All Other Corporate Bonds 4,232.1 23,026.1 1,495.8 — 28,754.0 Redeemable Preferred Stocks — 18.8 21.1 — 39.9 Total Fixed Maturity Securities 5,031.9 36,346.8 1,633.0 — 43,011.7 Other Long-term Investments Derivatives Foreign Exchange Contracts — 30.4 — — 30.4 Credit Default Swaps — 0.5 — — 0.5 Equity Securities — 24.6 4.6 — 29.2 Private Equity Partnerships — — — 483.8 483.8 Total Other Long-term Investments — 55.5 4.6 483.8 543.9 Total Financial Instrument Assets Carried at Fair Value $ 5,031.9 $ 36,402.3 $ 1,637.6 $ 483.8 $ 43,555.6 Liabilities Other Liabilities Derivatives Interest Rate Swaps $ — $ 5.2 $ — $ — $ 5.2 Foreign Exchange Contracts — 32.8 — — 32.8 Embedded Derivative in Modified Coinsurance Arrangement — — 31.1 — 31.1 Total Derivatives — 38.0 31.1 — 69.1 Total Financial Instrument Liabilities Carried at Fair Value $ — $ 38.0 $ 31.1 $ — $ 69.1 December 31, 2017 Level 1 Level 2 Level 3 NAV Total (in millions of dollars) Assets Fixed Maturity Securities United States Government and Government Agencies and Authorities $ 460.1 $ 1,022.4 $ — $ — $ 1,482.5 States, Municipalities, and Political Subdivisions — 2,336.9 — — 2,336.9 Foreign Governments — 863.9 — — 863.9 Public Utilities 154.2 7,874.6 207.7 — 8,236.5 Mortgage/Asset-Backed Securities — 1,973.6 — — 1,973.6 All Other Corporate Bonds 3,556.1 25,816.2 1,150.1 — 30,522.4 Redeemable Preferred Stocks — 19.2 22.8 — 42.0 Total Fixed Maturity Securities 4,170.4 39,906.8 1,380.6 — 45,457.8 Other Long-term Investments Derivatives Foreign Exchange Contracts — 19.5 — — 19.5 Equity Securities 0.2 10.4 1.1 — 11.7 Private Equity Partnerships — — — 407.2 407.2 Total Other Long-term Investments 0.2 29.9 1.1 407.2 438.4 Total Financial Instrument Assets Carried at Fair Value $ 4,170.6 $ 39,936.7 $ 1,381.7 $ 407.2 $ 45,896.2 Liabilities Other Liabilities Derivatives Interest Rate Swaps $ — $ 5.1 $ — $ — $ 5.1 Foreign Exchange Contracts — 46.9 — — 46.9 Credit Default Swaps — 0.2 — — 0.2 Embedded Derivative in Modified Coinsurance Arrangement — — 15.9 — 15.9 Total Derivatives — 52.2 15.9 — 68.1 Total Financial Instrument Liabilities Carried at Fair Value $ — $ 52.2 $ 15.9 $ — $ 68.1 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, 2018 Total Realized and Unrealized Investment Gains (Losses) Included in Fair Value Beginning of Year Earnings Other Comprehensive Income or Loss Purchases Sales Level 3 Transfers Fair Value End of Year Into Out of (in millions of dollars) Fixed Maturity Securities Foreign Governments $ — $ — $ (1.4 ) $ — $ — $ 32.8 $ — $ 31.4 Public Utilities 207.7 — (2.3 ) — — 39.0 (159.7 ) 84.7 All Other Corporate Bonds 1,150.1 5.8 (118.1 ) 95.1 (148.7 ) 968.6 (457.0 ) 1,495.8 Redeemable Preferred Stocks 22.8 — (1.7 ) — — — — 21.1 Total Fixed Maturity Securities 1,380.6 5.8 (123.5 ) 95.1 (148.7 ) 1,040.4 (616.7 ) 1,633.0 Equity Securities 1.1 — — 3.5 — — — 4.6 Embedded Derivative in Modified Coinsurance Arrangement (15.9 ) (15.2 ) — — — — — (31.1 ) Year Ended December 31, 2017 Total Realized and Unrealized Investment Gains (Losses) Included in Fair Value Beginning Earnings Other Comprehensive Income or Loss Purchases Sales Level 3 Transfers Fair Value End of Into Out of (in millions of dollars) Fixed Maturity Securities States, Municipalities, and Political Subdivisions $ 89.5 $ — $ — $ — $ — $ — $ (89.5 ) $ — Public Utilities 265.3 — 0.3 8.0 (4.8 ) 125.2 (186.3 ) 207.7 All Other Corporate Bonds 1,459.7 (0.6 ) 2.8 118.9 (149.2 ) 524.7 (806.2 ) 1,150.1 Redeemable Preferred Stocks 23.2 — (0.4 ) — — — — 22.8 Total Fixed Maturity Securities 1,837.7 (0.6 ) 2.7 126.9 (154.0 ) 649.9 (1,082.0 ) 1,380.6 Equity Securities 1.2 — — — — — (0.1 ) 1.1 Embedded Derivative in Modified Coinsurance Arrangement (46.7 ) 30.8 — — — — — (15.9 ) Realized and unrealized investment gains and losses presented in the preceding tables represent gains and losses only for the time during which the applicable financial instruments were classified as Level 3. The transfers between levels resulted primarily from a change in observability of three inputs used to determine fair values of the securities transferred: (1) transactional data for new issuance and secondary trades, (2) broker/dealer quotes and pricing, primarily related to changes in the level of activity in the market and whether the market was considered orderly, and (3) comparable bond metrics from which to perform an analysis. For fair value measurements of financial instruments that were transferred either into or out of Level 3, we reflect the transfers using the fair value at the beginning of the period. We believe this allows for greater transparency, as all changes in fair value that arise during the reporting period of the transfer are disclosed as a component of our Level 3 reconciliation. Gains (losses) which are included in earnings and are attributable to the change in fair value of assets or liabilities valued using significant unobservable inputs and still held at each year end were $(15.2) million and $30.8 million for the years ended December 31, 2018 and 2017 , respectively. These amounts relate entirely to the change in fair value of an embedded derivative in a modified coinsurance arrangement and are reported as a component of realized investment gains and losses. The table below provides quantitative information regarding the significant unobservable inputs used in Level 3 fair value measurements derived from internal models. 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, 2018 Fair Value Valuation Method Unobservable Input Range/Weighted Average (in millions of dollars) Fixed Maturity Securities All Other Corporate Bonds - Private $ 148.5 Market Approach Lack of Marketability Equity Securities - Private 4.6 Market Approach Market Convention (d) Priced at Cost or Owner's Equity Embedded Derivative in Modified Coinsurance Arrangement (31.1 ) Discounted Cash Flows Projected Liability Cash Flows (e) Actuarial Assumptions December 31, 2017 Fair Value Valuation Method Unobservable Input Range/Weighted Average (in millions of dollars) Fixed Maturity Securities All Other Corporate Bonds - Private $ 244.4 Market Approach Comparability Adjustment (a) 0.20% - 0.20% / 0.20% Equity Securities - Private 1.1 Market Approach Market Convention (d) Priced at Cost or Owner's Equity Embedded Derivative in Modified Coinsurance Arrangement (15.9 ) Discounted Cash Flows Projected Liability Cash Flows (e) Actuarial Assumptions (a) Represents basis point adjustments for changes in benchmark spreads associated with various industry sectors (b) Represents basis point adjustments to apply a discount due to the illiquidity of an investment (c) Represents basis point adjustments for credit-specific factors (d) Represents a decision to price based on par value, cost, or owner's equity when limited data is available (e) Represents various actuarial assumptions required to derive the liability cash flows including incidence, termination, and lapse rates Isolated increases in unobservable inputs other than market convention will result in a lower fair value measurement, whereas isolated decreases will result in a higher fair value measurement. The unobservable input for market convention is not sensitive to input movements. The projected liability cash flows used in the fair value measurement of our Level 3 embedded derivative are based on expected claim payments. If claim payments increase, the projected liability cash flows will increase, resulting in a decrease in the fair value of the embedded derivative. Decreases in projected liability cash flows will result in an increase in the fair value of the embedded derivative. Fair Value Measurements for Financial Instruments Not Carried at Fair Value The methods and assumptions used to estimate fair values of financial instruments not carried at fair value are discussed as follows: Mortgage Loans: Fair values are estimated using discounted cash flow analyses and interest rates currently being offered for similar loans to borrowers with similar credit ratings and maturities. Loans with similar characteristics are aggregated for purposes of the calculations. Policy Loans: Fair values for policy loans, net of reinsurance ceded, are estimated using discounted cash flow analyses and interest rates currently being offered to policyholders with similar policies. Carrying amounts for ceded policy loans, which equal $3,449.3 million and $3,307.5 million as of December 31, 2018 and 2017 , respectively, approximate fair value and are reported on a gross basis in our consolidated balance sheets. A change in interest rates for ceded policy loans will not impact our financial position because the benefits and risks are fully ceded to reinsuring counterparties. Miscellaneous Long-term Investments: Carrying amounts for tax credit partnerships equal the unamortized balance of our contractual commitments and approximate fair value. Our shares of FHLB common stock are carried at cost, which approximates fair value. Long-term Debt: Fair values for long-term debt are obtained from independent pricing services or discounted cash flow analyses based on current incremental borrowing rates for similar types of borrowing arrangements. 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, 2018 Estimated Fair Value Level 1 Level 2 Level 3 Total Carrying Value (in millions of dollars) Assets Mortgage Loans $ — $ 2,317.4 $ — $ 2,317.4 $ 2,295.0 Policy Loans — — 3,831.1 3,831.1 3,729.9 Other Long-term Investments Miscellaneous Long-term Investments — 24.1 91.5 115.6 115.6 Total Financial Instrument Assets Not Carried at Fair Value $ — $ 2,341.5 $ 3,922.6 $ 6,264.1 $ 6,140.5 Liabilities Long-term Debt $ 1,429.8 $ 1,639.4 $ — $ 3,069.2 $ 2,971.3 Payables for Collateral on Investments Federal Home Loan Bank (FHLB) Funding Agreements — 104.0 — 104.0 104.0 Other Liabilities Unfunded Commitments — 2.3 — 2.3 2.3 Total Financial Instrument Liabilities Not Carried at Fair Value $ 1,429.8 $ 1,745.7 $ — $ 3,175.5 $ 3,077.6 December 31, 2017 Estimated Fair Value Level 1 Level 2 Level 3 Total Carrying Value (in millions of dollars) Assets Mortgage Loans $ — $ 2,306.2 $ — $ 2,306.2 $ 2,213.2 Policy Loans — — 3,677.5 3,677.5 3

Investments

Investments	12 Months Ended
	Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Investments	Fixed Maturity Securities At December 31, 2018 and 2017 , 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, 2018 Amortized Cost Gross Unrealized Gain Gross Unrealized Loss Fair Value (in millions of dollars) United States Government and Government Agencies and Authorities $ 1,702.1 $ 123.2 $ 10.9 $ 1,814.4 States, Municipalities, and Political Subdivisions 2,121.5 307.1 4.4 2,424.2 Foreign Governments 825.8 162.7 4.8 983.7 Public Utilities 6,626.2 850.0 63.4 7,412.8 Mortgage/Asset-Backed Securities 1,523.8 67.2 8.3 1,582.7 All Other Corporate Bonds 27,436.8 1,981.6 664.4 28,754.0 Redeemable Preferred Stocks 39.0 1.1 0.2 39.9 Total Fixed Maturity Securities $ 40,275.2 $ 3,492.9 $ 756.4 $ 43,011.7 December 31, 2017 Amortized Cost Gross Unrealized Gain Gross Unrealized Loss Fair Value (in millions of dollars) United States Government and Government Agencies and Authorities $ 1,311.1 $ 176.1 $ 4.7 $ 1,482.5 States, Municipalities, and Political Subdivisions 1,942.8 395.4 1.3 2,336.9 Foreign Governments 673.0 191.3 0.4 863.9 Public Utilities 6,952.7 1,296.4 12.6 8,236.5 Mortgage/Asset-Backed Securities 1,873.2 105.1 4.7 1,973.6 All Other Corporate Bonds 26,988.7 3,633.5 99.8 30,522.4 Redeemable Preferred Stocks 39.0 3.0 — 42.0 Total Fixed Maturity Securities $ 39,780.5 $ 5,800.8 $ 123.5 $ 45,457.8 The following charts indicate the length of time our fixed maturity securities have been in a gross unrealized loss position. December 31, 2018 Less Than 12 Months 12 Months or Greater Fair Value Gross Unrealized Loss Fair Value Gross Unrealized Loss (in millions of dollars) United States Government and Government Agencies and Authorities $ 68.8 $ 1.7 $ 212.5 $ 9.2 States, Municipalities, and Political Subdivisions 183.2 2.1 65.0 2.3 Foreign Governments 58.4 3.8 12.0 1.0 Public Utilities 740.1 31.3 325.7 32.1 Mortgage/Asset-Backed Securities 81.5 1.2 201.6 7.1 All Other Corporate Bonds 9,240.2 462.2 1,704.9 202.2 Redeemable Preferred Stocks 18.8 0.2 — — Total Fixed Maturity Securities $ 10,391.0 $ 502.5 $ 2,521.7 $ 253.9 December 31, 2017 Less Than 12 Months 12 Months or Greater Fair Value Gross Unrealized Loss Fair Value Gross Unrealized Loss (in millions of dollars) United States Government and Government Agencies and Authorities $ 157.9 $ 3.0 $ 58.8 $ 1.8 States, Municipalities, and Political Subdivisions 45.7 0.5 22.3 0.7 Foreign Governments 13.2 0.4 — — Public Utilities 213.2 7.9 133.5 4.7 Mortgage/Asset-Backed Securities 252.5 1.4 144.7 3.3 All Other Corporate Bonds 1,355.1 26.8 785.2 73.0 Total Fixed Maturity Securities $ 2,037.6 $ 40.0 $ 1,144.5 $ 83.5 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, 2018 Total Amortized Cost Unrealized Gain Position Unrealized Loss Position Gross Gain Fair Value Gross Loss Fair Value (in millions of dollars) 1 year or less $ 1,073.3 $ 14.5 $ 1,020.1 $ 8.4 $ 59.3 Over 1 year through 5 years 6,267.5 300.6 5,186.9 80.2 1,301.0 Over 5 years through 10 years 12,573.4 795.0 6,812.7 303.9 6,251.8 Over 10 years 18,837.2 2,315.6 15,779.7 355.6 5,017.5 38,751.4 3,425.7 28,799.4 748.1 12,629.6 Mortgage/Asset-Backed Securities 1,523.8 67.2 1,299.6 8.3 283.1 Total Fixed Maturity Securities $ 40,275.2 $ 3,492.9 $ 30,099.0 $ 756.4 $ 12,912.7 December 31, 2017 Total Amortized Cost Unrealized Gain Position Unrealized Loss Position Gross Gain Fair Value Gross Loss Fair Value (in millions of dollars) 1 year or less $ 1,625.1 $ 30.9 $ 1,638.8 $ 3.1 $ 14.1 Over 1 year through 5 years 5,579.9 453.6 5,810.9 18.5 204.1 Over 5 years through 10 years 12,091.1 1,169.8 11,916.5 53.2 1,291.2 Over 10 years 18,611.2 4,041.4 21,333.1 44.0 1,275.5 37,907.3 5,695.7 40,699.3 118.8 2,784.9 Mortgage/Asset-Backed Securities 1,873.2 105.1 1,576.4 4.7 397.2 Total Fixed Maturity Securities $ 39,780.5 $ 5,800.8 $ 42,275.7 $ 123.5 $ 3,182.1 The following chart depicts an analysis of our fixed maturity security portfolio between investment-grade and below-investment-grade categories as of December 31, 2018 : Gross Unrealized Loss Fair Value Gross Unrealized Gain Amount Percent of Total Gross Unrealized Loss (in millions of dollars) Investment-Grade $ 39,973.1 $ 3,464.2 $ 529.5 70.0 % Below-Investment-Grade 3,038.6 28.7 226.9 30.0 Total Fixed Maturity Securities $ 43,011.7 $ 3,492.9 $ 756.4 100.0 % 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, 2018 , 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 an other-than-temporary impairment will recover in value. As of December 31, 2018 , we held 552 individual investment-grade fixed maturity securities and 135 individual below-investment-grade fixed maturity securities that were in an unrealized loss position, of which 204 investment-grade fixed maturity securities and 32 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 is other than temporary, 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 • The time period during which there has been a significant 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 other-than-temporary impairments is a judgmental area, we utilize a formal, well-defined, and disciplined process to monitor and evaluate our fixed income investment portfolio, supported by issuer specific research and documentation as of the end of each period. The process results in a thorough evaluation of problem investments and the recording of losses on a timely basis for investments determined to have an other-than-temporary impairment. We held no fixed maturity securities as of December 31, 2018 and 2017 , for which a portion of an other-than-temporary impairment was recognized in accumulated other comprehensive income. At December 31, 2018 , we had commitments of $117.3 million to fund private placement fixed maturity securities, the amount of which may or may not be funded. Variable Interest Entities We invest in variable interests issued by variable interest entities. These investments include tax credit partnerships, private equity partnerships, and special purpose entities. For those variable interests that are not consolidated in our financial statements, we are not the primary beneficiary because we have neither the power to direct the activities that are most significant to economic performance nor the responsibility to absorb a majority of the expected losses. The determination of whether we are the primary beneficiary is performed at the time of our initial investment and at the date of each subsequent reporting period. As of December 31, 2018 , the carrying amount of our variable interest entity investments that are not consolidated in our financial statements was $575.3 million , comprised of $91.5 million of tax credit partnerships and $483.8 million of private equity partnerships. At December 31, 2017 , the carrying amount of our variable interest entity investments that are not consolidated in our financial statements was $535.4 million , comprised of $128.2 million of tax credit partnerships and $407.2 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 2018 2017 2016 (in millions of dollars) Income Tax Credits $ 41.4 $ 41.8 $ 41.8 Amortization, Net of Tax (28.1 ) (23.2 ) (23.2 ) Income Tax Benefit $ 13.3 $ 18.6 $ 18.6 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 $2.3 million of unfunded unconditional commitments at December 31, 2018 . See Note 2 for commitments to fund private equity partnerships. We are the sole beneficiary of a special purpose entity which is consolidated in our financial statements. This entity is a securitized asset trust containing a highly rated bond for principal protection which we contributed into the trust at the time it was established. There are no restrictions on the asset held in this trust, and the trust is free to dispose of the asset at any time. The fair values of the bond were $156.7 million and $154.1 million as of December 31, 2018 and 2017 , respectively. The bond is reported as a component of fixed maturity securities in our consolidated balance sheets. At December 31, 2016 , the trust also contained a private equity partnership which we contributed into the trust at the time it was established with a fair value of $1.0 million . During 2017 , we received the final distribution from the private equity partnership and recorded a loss of $0.2 million on the disposal. The loss is reported as a component of net realized investments gains and losses in our consolidated statements of income. Mortgage Loans Our mortgage loan portfolio is well diversified by both geographic region and property type to reduce risk of concentration. All of our mortgage loans are collateralized by commercial real estate. When issuing a new loan, our general policy is not to exceed a loan-to-value ratio, or the ratio of the loan balance to the estimated fair value of the underlying collateral, of 75 percent. We update the loan-to-value ratios at least every three years for each loan, and properties undergo a general inspection at least every two years. Our general policy for newly issued loans is to have a debt service coverage ratio greater than 1.25 times on a normalized 25 year amortization period. We update our debt service coverage ratios annually. Mortgage loans by property type and geographic region are presented below. December 31 2018 2017 (in millions of dollars) Carrying Percent of Carrying Percent of Amount Total Amount Total Property Type Apartment $ 491.0 21.4 % $ 360.0 16.3 % Industrial 635.6 27.7 601.2 27.2 Office 604.2 26.3 692.3 31.3 Retail 519.5 22.6 527.6 23.8 Other 44.7 2.0 32.1 1.4 Total $ 2,295.0 100.0 % $ 2,213.2 100.0 % Region New England $ 45.9 2.0 % $ 56.1 2.5 % Mid-Atlantic 160.6 7.0 155.5 7.0 East North Central 354.4 15.4 282.0 12.8 West North Central 190.3 8.3 210.1 9.5 South Atlantic 485.2 21.1 494.4 22.3 East South Central 105.5 4.6 88.8 4.0 West South Central 240.6 10.5 247.4 11.2 Mountain 242.7 10.6 251.2 11.4 Pacific 469.8 20.5 427.7 19.3 Total $ 2,295.0 100.0 % $ 2,213.2 100.0 % We evaluate each of our mortgage loans individually for impairment and assign an internal credit quality rating based on a comprehensive rating system used to evaluate the credit risk of the loan. The factors we use to derive our internal credit ratings may include the following: • Loan-to-value ratio • Debt service coverage ratio based on current operating income • Property location, including regional economics, trends and demographics • Age, condition, and construction quality of property • Current and historical occupancy of property • Lease terms relative to market • Tenant size and financial strength • Borrower's financial strength • Borrower's equity in transaction • Additional collateral, if any Although all available and applicable factors are considered in our analysis, loan-to-value and debt service coverage ratios are the most critical factors in determining whether we will initially issue the loan and also in assigning values and determining impairment. We assign an overall rating to each loan using an internal rating scale of Aa (highest quality) to B (lowest quality). We review and adjust, as needed, our internal credit quality ratings on an annual basis. This review process is performed more frequently for mortgage loans deemed to have a higher risk of delinquency. Mortgage loans, sorted by the applicable credit quality indicators, are as follows: December 31 2018 2017 (in millions of dollars) Internal Rating Aa $ — $ 0.4 A 477.5 445.7 Baa 1,814.1 1,753.0 Ba 3.4 14.1 Total $ 2,295.0 $ 2,213.2 Loan-to-Value Ratio <= 65% $ 1,204.8 $ 1,101.7 > 65% <= 75% 1,049.1 1,041.6 > 75% <= 85% 11.8 49.3 > 85% 29.3 20.6 Total $ 2,295.0 $ 2,213.2 At December 31, 2018 , we held one mortgage loan that was greater than 90 days past due regarding principal and/or interest payments which was modified in a troubled debt restructuring during the second quarter of 2018 . The loan had a principal balance of $3.6 million prior to the restructuring, wherein the terms of the loan were modified to reduce monthly payments to interest-only at the current note rate and to permit a discounted payoff by September 2018. At the time of restructuring in the second quarter of 2018 , we recorded an allowance for credit losses and recognized an impairment loss of $0.2 million resulting in a net realizable value for the loan of $3.4 million . The payoff of the loan did not occur in September 2018 and therefore, the loan was considered impaired as of December 31, 2018 . At December 31, 2017 , we held no mortgage loans that were greater than 90 days past due regarding principal and/or interest payments. There were no troubled debt restructurings during 2017 . During 2016 , we foreclosed on a mortgage loan with a carrying value of $5.4 million . We did not recognize a loss at foreclosure as the value of the underlying property exceeded the carrying value of the loan. We had no realized losses on loan foreclosures for the years ended December 31, 2018 , 2017 , and 2016 other than any initial impairment loss recognized prior to foreclosure. There have been no changes to our accounting policies or methodology from the prior period regarding estimating the allowance for credit losses on our mortgage loans. There was no activity in the allowance for credit losses for the years ended December 31, 2018 , 2017 or 2016 other than previously mentioned impairment loss of $0.2 million . Our average investment in impaired mortgage loans was $2.3 million and $2.2 million for the years ended December 31, 2018 and 2016 , respectively. We did not hold any impaired mortgage loans for the year ended December 31, 2017 . We did not recognize any interest income during 2018 , 2017 or 2016 on mortgage loans subsequent to impairment. At December 31, 2018 , we had commitments of $13.0 million to fund certain commercial mortgage loans, the amount of which may or may not be funded. 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, 2018 , the carrying amount of fixed maturity securities loaned to third parties under our securities lending program was $164.1 million , for which we received collateral in the form of cash and securities of $0.1 million and $171.4 million , respectively. As of December 31, 2017 , the carrying amount of fixed maturity securities loaned to third parties under our securities lending program was $159.2 million , for which we received collateral in the form of cash and securities of $30.5 million and $135.6 million , respectively. We had no outstanding repurchase agreements at December 31, 2018 or 2017 . The remaining contractual maturities of our securities lending agreements disaggregated by class of collateral pledged are as follows: December 31 2018 2017 Overnight and Continuous (in millions of dollars) United States Government and Government Agencies and Authorities $ — $ 0.2 Public Utilities — 0.5 All Other Corporate Bonds 0.1 29.8 Total Borrowings 0.1 30.5 Gross Amount of Recognized Liability for Securities Lending Transactions 0.1 30.5 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, 2018 December 31, 2017 (in millions of dollars) Carrying Value of FHLB Common Stock $ 24.1 $ 34.1 Advances from FHLB $ 104.0 $ 350.0 Carrying Value of Collateral Posted to FHLB Fixed Maturity Securities $ 219.8 $ 213.3 Commercial Mortgage Loans 179.9 331.5 Total Carrying Value of Collateral Posted to FHLB $ 399.7 $ 544.8 Offsetting of Financial Instruments We enter into master netting agreements with each of our derivatives counterparties. These agreements provide for conditional rights of set-off upon the occurrence of an early termination event. An early termination event is considered a default, and it allows the non-defaulting party to offset its contracts in a loss position against any gain positions or payments due to the defaulting party. Under our agreements, default type events are defined as failure to pay or deliver as contractually agreed, misrepresentation, bankruptcy, or merger without assumption. See Note 4 for further discussion of collateral related to our derivative contracts. We have securities lending agreements with unaffiliated financial institutions that post collateral to us in return for the use of our fixed maturity securities. A right of set-off exists that allows us to keep and apply collateral received in the event of default by the counterparty. Default within a securities lending agreement would typically occur if the counterparty failed to return the securities borrowed from us as contractually agreed. In addition, if we default by not returning collateral received, the counterparty has a right of set-off against our securities or any other amounts due to us. Shown below are our financial instruments that either meet the accounting requirements that allow them to be offset in our balance sheets or that are subject to an enforceable master netting arrangement or similar agreement. Our accounting policy is to not offset these financial instruments in our balance sheets. Net amounts disclosed below have been reduced by the amount of collateral pledged to or received from our counterparties. December 31, 2018 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 $ 30.9 $ — $ 30.9 $ (6.9 ) $ (24.0 ) $ — Securities Lending 164.1 — 164.1 (164.0 ) (0.1 ) — Total $ 195.0 $ — $ 195.0 $ (170.9 ) $ (24.1 ) $ — Financial Liabilities: Derivatives $ 38.0 $ — $ 38.0 $ (33.2 ) $ — $ 4.8 Securities Lending 0.1 — 0.1 (0.1 ) — — Total $ 38.1 $ — $ 38.1 $ (33.3 ) $ — $ 4.8 December 31, 2017 Gross Amount Gross Amount Not of Recognized Gross Amount Net Amount Offset in Balance Sheet Financial Offset in Presented in Financial Cash Net Instruments Balance Sheet Balance Sheet Instruments Collateral Amount (in millions of dollars) Financial Assets: Derivatives $ 19.5 $ — $ 19.5 $ (4.2 ) $ (15.3 ) $ — Securities Lending 159.2 — 159.2 (128.7 ) (30.5 ) — Total $ 178.7 $ — $ 178.7 $ (132.9 ) $ (45.8 ) $ — Financial Liabilities: Derivatives $ 52.2 $ — $ 52.2 $ (42.9 ) $ — $ 9.3 Securities Lending 30.5 — 30.5 (30.5 ) — — Total $ 82.7 $ — $ 82.7 $ (73.4 ) $ — $ 9.3 Net Investment Income Net investment income reported in our consolidated statements of income is as follows: Year Ended December 31 2018 2017 2016 (in millions of dollars) Fixed Maturity Securities $ 2,239.7 $ 2,271.8 $ 2,293.9 Derivatives 66.1 56.4 49.8 Mortgage Loans 110.1 104.2 114.0 Policy Loans 18.6 17.9 17.3 Other Long-term Investments Equity Securities 1 (0.2 ) 1.5 1.2 Private Equity Partnerships 2 36.0 25.5 11.4 Other 8.4 10.0 10.0 Short-term Investments 23.7 11.3 7.5 Gross Investment Income 2,502.4 2,498.6 2,505.1 Less Investment Expenses 35.2 32.8 31.9 Less Investment Income on Participation Fund Account Assets 13.5 14.1 14.2 Net Investment Income $ 2,453.7 $ 2,451.7 $ 2,459.0 1 The net unrealized loss recognized in net investment income for the year ended December 31, 2018 related to equity securities still held at December 31, 2018 was $3.9 million . 2 The net unrealized gain recognized in net investment income for the year ended December 31, 2018 related to private equity partnerships still held at December 31, 2018 was $7.1 million . Realized Investment Gain and Loss Realized investment gains and losses are as follows: Year Ended December 31 2018 2017 2016 (in millions of dollars) Fixed Maturity Securities Gross Gains on Sales $ 9.7 $ 13.8 $ 34.3 Gross Losses on Sales (15.2 ) (4.4 ) (17.2 ) Other-Than-Temporary Impairment Loss (17.5 ) (8.1 ) (30.5 ) Mortgage Loans and Other Invested Assets Gross Gains on Sales 0.5 9.4 5.5 Gross Losses on Sales — (0.2 ) (0.7 ) Impairment Loss (1.4 ) (0.9 ) (5.7 ) Embedded Derivative in Modified Coinsurance Arrangement (15.2 ) 30.8 40.9 All Other Derivatives 0.3 (0.1 ) (1.5 ) Foreign Currency Transactions (0.7 ) — (0.9 ) Net Realized Investment Gain (Loss) $ (39.5 ) $ 40.3 $ 24.2

Derivative Financial Instrument

Derivative Financial Instruments	12 Months Ended
	Dec. 31, 2018
Notes to Financial Statements [Abstract]
Derivative Financial Instruments	Purpose of Derivatives We are exposed to certain risks relating to our ongoing business operations. The primary risks managed by using derivative instruments are interest rate risk, risk related to matching duration for our assets and liabilities, foreign currency risk, and credit risk. Historically, we have utilized current and forward interest rate swaps, current and forward currency swaps, forward treasury locks, currency forward contracts, forward contracts on specific fixed income securities, and credit default swaps. Transactions hedging interest rate risk are primarily associated with our individual and group long-term care and individual and group disability products. All other product portfolios are periodically reviewed to determine if hedging strategies would be appropriate for risk management purposes. We do not use derivative financial instruments for speculative purposes. Derivatives designated as cash flow hedges and used to reduce our exposure to interest rate and duration risk are as follows: • Interest rate swaps are used to hedge interest rate risks and to improve the matching of assets and liabilities. An interest rate swap is an agreement in which we agree with other parties to exchange, at specified intervals, the difference between fixed rate and variable rate interest amounts. We use interest rate swaps to hedge the anticipated purchase of fixed maturity securities thereby protecting us from the potential adverse impact of declining interest rates on the associated policy reserves. We also use interest rate swaps to hedge the potential adverse impact of rising interest rates in anticipation of issuing fixed rate long-term debt. • Forward treasury locks are used to minimize interest rate risk associated with the anticipated purchase or disposal of fixed maturity securities. A forward treasury lock is a derivative contract without an initial investment where we and the counterparty agree to purchase or sell a specific U.S. Treasury bond at a future date at a pre-determined price. Derivatives designated as fair value hedges and used to reduce our exposure to interest rate and duration risk are as follows: • Interest rate swaps are used to effectively convert certain of our fixed rate securities into floating rate securities which are used to fund our floating rate long-term debt. Under these swap agreements, we receive a variable rate of interest and pay a fixed rate of interest. Additionally, we use interest rate swaps to effectively convert certain fixed rate, long-term debt into floating rate long-term debt. Under these swap agreements, we receive a fixed rate of interest and pay a variable rate of interest. Derivatives designated as either cash flow or fair value hedges and used to reduce our exposure to foreign currency risk are as follows: • Foreign currency interest rate swaps are used to hedge the currency risk of certain foreign currency-denominated fixed maturity securities owned for portfolio diversification. Under these swap agreements, we agree to pay, at specified intervals, fixed rate foreign currency-denominated principal and interest payments in exchange for fixed rate payments in the functional currency of the operating segment. Derivatives not designated as hedging instruments and used to reduce our exposure to foreign currency risk, credit losses on securities owned, and interest rate risk are as follows: • Foreign currency interest rate swaps previously designated as hedges were used to hedge the currency risk of certain foreign currency-denominated fixed maturity securities owned for portfolio diversification. These derivatives were effective hedges prior to novation to a new counterparty. In conjunction with the novation, these derivatives were de-designated as hedges. We agree to pay, at specified intervals, fixed rate foreign currency-denominated principal and interest payments in exchange for fixed rate payments in the functional currency of the operating segment. We hold offsetting swaps wherein we agree to pay fixed rate principal and interest payments in the functional currency of the operating segment in exchange for fixed rate foreign currency-denominated payments. • Credit default swaps are used as economic hedges against credit risk but do not qualify for hedge accounting. A credit default swap is an agreement in which we agree with another party to pay, at specified intervals, a fixed-rate fee in exchange for insurance against a credit event on a specific investment. If a defined credit event occurs, our counterparty may either pay us a net cash settlement, or we may surrender the specific investment to them in exchange for cash equal to the full notional amount of the swap. Credit events typically include events such as bankruptcy, failure to pay, or certain types of debt restructuring. • Interest rate swap was used to effectively convert certain of our floating rate, long-term debt into fixed rate long-term debt. Under this swap agreement, we received a variable rate of interest and paid a fixed rate of interest. Derivative Risks The basic types of risks associated with derivatives are market risk (that the value of the derivative will be adversely impacted by changes in the market, primarily the change in interest and exchange rates) and credit risk (that the counterparty will not perform according to the terms of the contract). The market risk of the derivatives should generally offset the market risk associated with the hedged financial instrument or liability. To help limit the credit exposure of the derivatives, we enter into master netting agreements with our counterparties whereby contracts in a gain position can be offset against contracts in a loss position. We also typically enter into bilateral, cross-collateralization agreements with our counterparties to help limit the credit exposure of the derivatives. These agreements require the counterparty in a loss position to submit acceptable collateral with the other counterparty in the event the net loss position meets or exceeds an agreed upon amount. Our credit exposure on derivatives, which is limited to the value of those contracts in a net gain position, including accrued interest receivable less collateral held, was $0.9 million at December 31, 2018 . As of December 31, 2017 we did not have any credit exposure on derivatives. The table below summarizes the nature and amount of collateral received from and posted to our derivative counterparties. December 31, 2018 December 31, 2017 (in millions of dollars) Carrying Value of Collateral Received from Counterparties Cash $ 24.0 $ 15.7 Carrying Value of Collateral Posted to Counterparties Fixed Maturity Securities $ 33.4 $ 46.4 See Note 3 for further discussion of our master netting agreements. The majority of our derivative instruments contain provisions that require us to maintain specified issuer credit ratings and financial strength ratings. Should our ratings fall below these specified levels, we would be in violation of the provisions, and our derivatives counterparties could terminate our contracts and request immediate payment. The aggregate fair value of all derivative instruments with credit risk-related contingent features that were in a liability position was $38.0 million and $52.2 million at December 31, 2018 and 2017 , respectively. Derivative Transactions The table below summarizes, by notional amounts, the activity for each category of derivatives. The notional amounts represent the basis upon which our counterparty pay and receive amounts are calculated. Swaps Receive Variable/Pay Fixed Receive Fixed/Pay Fixed Receive Fixed/Pay Variable Credit Default Forwards Total (in millions of dollars) Balance at December 31, 2015 $ 150.0 $ 650.3 $ 600.0 $ 70.0 $ — $ 1,470.3 Additions 3.5 — — — 30.0 33.5 Terminations 48.0 33.8 350.0 — 20.0 451.8 Balance at December 31, 2016 105.5 616.5 250.0 70.0 10.0 1,052.0 Additions — 26.4 — — 65.7 92.1 Terminations 57.5 106.4 — — 75.7 239.6 Balance at December 31, 2017 48.0 536.5 250.0 70.0 — 904.5 Additions — 78.1 — 11.0 47.4 136.5 Terminations 48.0 76.4 — 70.0 47.4 241.8 Balance at December 31, 2018 $ — $ 538.2 $ 250.0 $ 11.0 $ — $ 799.2 Cash Flow Hedges As of December 31, 2018 and 2017 , we had $286.4 million and $343.9 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, 2018 , we expect to amortize approximately $70.0 million of net deferred gains on derivative instruments during the next twelve months. This amount will be reclassified from accumulated other comprehensive income into earnings and reported on the same income statement line item as the hedged item. The income statement line items that will be affected by this amortization are net investment income and interest and debt expense. Additional amounts that may be reclassified from accumulated other comprehensive income into earnings to offset the earnings impact of foreign currency translation of hedged items are not estimable. As of December 31, 2018 , we are hedging the variability of future cash flows associated with forecasted transactions through the year 2038 . Fair Value Hedges As of December 31, 2017 , we had $48.0 million of notional amount of receive variable, pay fixed interest rate swaps to hedge the changes in fair value of certain fixed rate securities held which matured in 2018 along with the hedged securities. These swaps effectively converted the associated fixed rate securities into floating rate securities, which were used to fund our floating rate long-term debt. During 2016 , we terminated $24.0 million notional amount of receive variable, pay fixed interest rate swaps in connection with the sale of the hedged securities and recorded a loss on the swap terminations of $1.2 million in our consolidated statements of income as a component of net realized investment gains and losses. As of December 31, 2018 , we had $ 78.1 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. As of December 31, 2018 and 2017 , we had 250.0 million notional amount of receive fixed, pay variable interest rate swaps to hedge the changes in the fair value of certain fixed rate long-term debt. These swaps effectively convert the associated fixed rate long-term debt into floating rate debt and provide for a better matching of interest rates with our short-term investments, which have frequent interest rate resets similar to a floating rate security. During 2016, $350.0 million notional amount of receive fixed, pay variable interest rate swaps matured in conjunction with the maturity of the $350.0 million hedged fixed rate debt. See Note 8. The following table summarizes the carrying amount of hedged assets and liabilities and the related cumulative basis adjustments related to our fair value hedges: Carrying Amount of Hedged Assets (Liabilities) Cumulative Amount of Fair Value Hedging Adjustment Included in the Carrying Amount of the Hedged Assets (Liabilities) December 31, 2018 December 31, 2017 December 31, 2018 December 31, 2017 (in millions of dollars) Fixed maturity securities: Receive variable interest rate, pay fixed interest rate $ — $ 48.5 $ — $ 0.6 Receive fixed functional currency interest, pay fixed foreign currency interest $ 56.2 $ — $ (2.7 ) $ — Long-term Debt $ (244.4 ) $ (244.8 ) $ 5.1 $ 4.5 For the year ended December 31, 2018 , $ 2.5 million of the derivative instruments' gain was excluded from the assessment of hedge effectiveness. For the year ended December 31, 2017 , no component of the derivative instruments' gain or loss was excluded from the assessment of hedge effectiveness. There were no instances wherein we discontinued fair value hedge accounting due to a hedged firm commitment no longer qualifying as a fair value hedge. Derivatives not Designated as Hedging Instruments As of December 31, 2018 and 2017 , we held $173.7 million and $192.6 million , respectively, notional amount of receive fixed, pay fixed, foreign currency interest rate swaps. These derivatives are not designated as hedges, and as such, changes in fair value related to these derivatives are reported in earnings as a component of net realized investment gain or loss. As of December 31, 2018 and 2017 , we held $11.0 million and $70.0 million , respectively, notional amount of single name credit default swaps. We entered into these swaps in order to mitigate the credit risk associated with specific securities owned. As of December 31, 2016 , we held $3.5 million notional amount of a receive variable, pay fixed interest rate swap acquired through our purchase of Starmount during 2016 . This swap effectively converted Starmount's floating rate long-term debt into fixed rate debt. During 2017 , we purchased and retired the debt and terminated the interest rate swap. We recorded a loss of $0.1 million on the swap termination in our consolidated statements of income as a component of net realized investment gains and losses. See Note 8. We have an embedded derivative in a modified coinsurance arrangement for which we include in our realized investment gains and losses a calculation intended to estimate the value of the option of our reinsurance counterparty to cancel the reinsurance contract with us. However, neither party can unilaterally terminate the reinsurance agreement except in extreme circumstances resulting from regulatory supervision, delinquency proceedings, or other direct regulatory action. Cash settlements or collateral related to this embedded derivative are not required at any time during the reinsurance contract or at termination of the reinsurance contract. There are no credit-related counterparty triggers, and any accumulated embedded derivative gain or loss reduces to zero over time as the reinsured business winds down. Locations and Amounts of Derivative Financial Instruments The following tables summarize the location and fair values of derivative financial instruments, as reported in our consolidated balance sheets. December 31, 2018 Derivative Assets Derivative Liabilities Balance Sheet Location Fair Value Balance Sheet Location Fair Value (in millions of dollars) Designated as Hedging Instruments Cash Flow Hedges Foreign Exchange Contracts Other L-T Investments $ 25.0 Other Liabilities $ 7.9 Fair Value Hedges Interest Rate Swaps Other L-T Investments — Other Liabilities 5.2 Foreign Exchange Contracts Other L-T Investments 5.4 Other Liabilities 0.4 Total Fair Value Hedges 5.4 5.6 Total Designated as Hedging Instruments $ 30.4 $ 13.5 Not Designated as Hedging Instruments Credit Default Swaps Other L-T Investments $ 0.5 Other Liabilities $ — Foreign Exchange Contracts Other L-T Investments — Other Liabilities 24.5 Embedded Derivative in Modified Coinsurance Arrangement Other L-T Investments — Other Liabilities 31.1 Total Not Designated as Hedging Instruments $ 0.5 $ 55.6 December 31, 2017 Derivative Assets Derivative Liabilities Balance Sheet Location Fair Value Balance Sheet Location Fair Value (in millions of dollars) Designated as Hedging Instruments Cash Flow Hedges Foreign Exchange Contracts Other L-T Investments $ 19.5 Other Liabilities $ 19.4 Fair Value Hedges Interest Rate Swaps Other L-T Investments — Other Liabilities 5.1 Total Designated as Hedging Instruments $ 19.5 $ 24.5 Not Designated as Hedging Instruments Credit Default Swaps Other Liabilities $ 0.2 Foreign Exchange Contracts Other Liabilities 27.5 Embedded Derivative in Modified Coinsurance Arrangement Other Liabilities 15.9 Total Not Designated as Hedging Instruments $ 43.6 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, 2018 Net Investment Income Net Realized Investment Gain (Loss) Interest and Debt Expense (in millions of dollars) Total Income and Expense Presented in the Consolidated Statements of Income of Which Hedged Items are Recorded $ 2,453.7 $ (39.5 ) $ 167.3 Gain (Loss) on Cash Flow Hedging Relationships Interest Rate Swaps: Hedged items 310.3 0.1 38.4 Derivatives Designated as Hedging Instruments 67.1 (0.3 ) 2.3 Foreign Exchange Contracts: Hedged items 18.1 1.5 — Derivatives Designated as Hedging Instruments (0.9 ) (1.5 ) — Gain (Loss) on Fair Value Hedging Relationships Interest Rate Swaps: Hedged items 1.0 0.1 14.3 Derivatives Designated as Hedging Instruments (0.5 ) (0.1 ) 1.8 Foreign Exchange Contracts Hedged items 0.6 (2.7 ) — Derivatives Designated as Hedging Instruments 0.5 2.7 — Year Ended December 31, 2017 Net Investment Income Net Realized Investment Gain (Loss) Interest and Debt Expense (in millions of dollars) Total Income and Expense Presented in the Consolidated Statements of Income of Which Hedged Items are Recorded $ 2,451.7 $ 40.3 $ 159.9 Gain (Loss) on Cash Flow Hedging Relationships Interest Rate Swaps: Hedged items 321.1 2.5 44.9 Derivatives Designated as Hedging Instruments 60.4 0.2 2.2 Foreign Exchange Contracts: Hedged items 21.7 8.9 — Derivatives Designated as Hedging Instruments (1.2 ) (9.2 ) — Gain (Loss) on Fair Value Hedging Relationships Interest Rate Swaps: Hedged items 4.8 (1.7 ) 14.3 Derivatives Designated as Hedging Instruments (3.2 ) 1.7 (0.6 ) Year Ended December 31, 2016 Net Investment Income Net Realized Investment Gain (Loss) Interest and Debt Expense (in millions of dollars) Total Income and Expense Presented in the Consolidated Statements of Income of Which Hedged Items are Recorded $ 2,459.0 $ 24.2 $ 166.0 Gain (Loss) on Cash Flow Hedging Relationships Interest Rate Swaps: Hedged items 337.7 7.2 44.9 Derivatives Designated as Hedging Instruments 55.7 3.4 2.1 Foreign Exchange Contracts: Hedged items 23.1 1.5 — Derivatives Designated as Hedging Instruments (0.6 ) (1.4 ) — Gain (Loss) on Fair Value Hedging Relationships Interest Rate Swaps: Hedged items 7.1 (3.1 ) 39.7 Derivatives Designated as Hedging Instruments (5.3 ) 3.1 (4.7 ) The following table summarizes the location of gains and losses of derivative financial instruments designated as cash flow hedging instruments, as reported in our consolidated statements of comprehensive income (loss). Year Ended December 31 2018 2017 2016 (in millions of dollars) Gain (Loss) Recognized in Other Comprehensive Income (Loss) on Derivatives Interest Rate Swaps and Forwards $ (0.1 ) $ (0.1 ) $ (0.1 ) Foreign Exchange Contracts 16.9 (23.0 ) (22.2 ) Total $ 16.8 $ (23.1 ) $ (22.3 ) 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 2018 2017 2016 (in millions of dollars) Net Realized Investment Gain (Loss) Credit Default Swaps $ (0.3 ) $ (0.4 ) $ (0.9 ) Interest Rate Swaps (0.3 ) (0.1 ) 0.4 Foreign Exchange Contracts 0.9 0.4 0.2 Embedded Derivative in Modified Coinsurance Arrangement (15.2 ) 30.8 40.9 Total $ (14.9 ) $ 30.7 $ 40.6

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income	12 Months Ended
	Dec. 31, 2018
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss)	Components of our accumulated other comprehensive income (loss), after tax, and related changes are as follows: Net Unrealized Gain (Loss) on Securities Net Gain on Hedges Foreign Currency Translation Adjustment Unrecognized Pension and Postretirement Benefit Costs Total (in millions of dollars) Balance at December 31, 2015 $ 204.3 $ 378.0 $ (173.6 ) $ (392.6 ) $ 16.1 Other Comprehensive Income (Loss) Before Reclassifications 226.5 (15.8 ) (180.4 ) (82.8 ) (52.5 ) Amounts Reclassified from Accumulated Other Comprehensive Income or Loss 9.8 (34.7 ) — 10.3 (14.6 ) Net Other Comprehensive Income (Loss) 236.3 (50.5 ) (180.4 ) (72.5 ) (67.1 ) Balance at December 31, 2016 440.6 327.5 (354.0 ) (465.1 ) (51.0 ) Other Comprehensive Income (Loss) Before Reclassifications 176.7 (14.7 ) 99.5 (55.9 ) 205.6 Amounts Reclassified from Accumulated Other Comprehensive Income or Loss (9.5 ) (30.5 ) — 12.9 (27.1 ) Net Other Comprehensive Income (Loss) 167.2 (45.2 ) 99.5 (43.0 ) 178.5 Balance at December 31, 2017 607.8 282.3 (254.5 ) (508.1 ) 127.5 Adjustment to Adopt Accounting Standard Update - Note 1 (17.5 ) — — — (17.5 ) Other Comprehensive Income (Loss) Before Reclassifications (920.3 ) 16.8 (50.7 ) 43.6 (910.6 ) Amounts Reclassified from Accumulated Other Comprehensive Income or Loss 17.6 (48.5 ) — 17.3 (13.6 ) Net Other Comprehensive Income (Loss) (902.7 ) (31.7 ) (50.7 ) 60.9 (924.2 ) Balance at December 31, 2018 $ (312.4 ) $ 250.6 $ (305.2 ) $ (447.2 ) $ (814.2 ) The net unrealized gain (loss) on securities consists of the following components: December 31 January 1 December 31 Change for the Year Ended December 31 2018 2017 2016 2015 2018 2017 2016 (in millions of dollars) Fixed Maturity Securities $ 2,736.5 $ 5,665.2 $ 5,677.3 $ 4,664.6 $ 3,695.7 $ (2,928.7 ) $ 1,012.7 $ 968.9 Other Investments — — 14.4 (22.7 ) (33.7 ) — 37.1 11.0 Deferred Acquisition Costs (27.9 ) (51.4 ) (51.4 ) (38.9 ) (29.4 ) 23.5 (12.5 ) (9.5 ) Reserves for Future Policy and Contract Benefits (3,220.3 ) (5,094.7 ) (5,094.7 ) (4,253.2 ) (3,578.4 ) 1,874.4 (841.5 ) (674.8 ) Reinsurance Recoverable 261.4 375.8 375.8 321.3 263.2 (114.4 ) 54.5 58.1 Income Tax (62.1 ) (304.6 ) (313.6 ) (230.5 ) (113.1 ) 242.5 (83.1 ) (117.4 ) Total $ (312.4 ) $ 590.3 $ 607.8 $ 440.6 $ 204.3 $ (902.7 ) $ 167.2 $ 236.3 Amounts reclassified from accumulated other comprehensive income (loss) were recognized in our consolidated statements of income as follows: Year Ended December 31 2018 2017 2016 (in millions of dollars) Net Unrealized Gain (Loss) on Securities Net Realized Investment Gain (Loss) Gain (Loss) on Sales of Securities and Other Invested Assets $ (4.8 ) $ 22.7 $ 15.3 Other-Than-Temporary Impairment Loss (17.5 ) (8.1 ) (30.5 ) (22.3 ) 14.6 (15.2 ) Income Tax Expense (Benefit) (4.7 ) 5.1 (5.4 ) Total $ (17.6 ) $ 9.5 $ (9.8 ) Net Gain on Hedges Net Investment Income Gain on Interest Rate Swaps and Forwards $ 65.9 $ 59.0 $ 54.5 Loss on Foreign Exchange Contracts (1.1 ) (1.2 ) (1.1 ) Net Realized Investment Gain (Loss) Gain on Interest Rate Swaps 0.2 0.2 3.2 Loss on Foreign Exchange Contracts (1.5 ) (9.2 ) (1.4 ) Interest and Debt Expense Loss on Interest Rate Swaps (2.1 ) (2.0 ) (1.9 ) 61.4 46.8 53.3 Income Tax Expense 12.9 16.3 18.6 Total $ 48.5 $ 30.5 $ 34.7 Unrecognized Pension and Postretirement Benefit Costs Other Expenses Amortization of Net Actuarial Loss $ (22.3 ) $ (20.3 ) $ (16.3 ) Amortization of Prior Service Credit 0.2 0.7 0.5 (22.1 ) (19.6 ) (15.8 ) Income Tax Benefit (4.8 ) (6.7 ) (5.5 ) Total $ (17.3 ) $ (12.9 ) $ (10.3 )

Liability for Unpaid Claims

Liability for Unpaid Claims	12 Months Ended
	Dec. 31, 2018
Insurance [Abstract]
Liability for Unpaid Claims Disclosure	Changes in the liability for unpaid claims and claim adjustment expenses are as follows: 2018 2017 2016 (in millions of dollars) Balance at January 1 $ 23,222.0 $ 23,249.5 $ 23,796.1 Less Reinsurance Recoverable 2,182.0 2,163.6 2,064.6 Net Balance at January 1 21,040.0 21,085.9 21,731.5 Incurred Related to Current Year 5,832.3 5,422.9 5,243.0 Prior Years Interest 1,049.8 1,089.7 1,136.7 All Other Incurred (106.2 ) (158.2 ) (198.3 ) Foreign Currency (110.7 ) 167.5 (340.2 ) Total Incurred 6,665.2 6,521.9 5,841.2 Paid Related to Current Year (2,354.7 ) (2,156.9 ) (2,035.4 ) Prior Years (4,428.8 ) (4,410.9 ) (4,451.4 ) Total Paid (6,783.5 ) (6,567.8 ) (6,486.8 ) Net Balance at December 31 20,921.7 21,040.0 21,085.9 Plus Reinsurance Recoverable 2,227.3 2,182.0 2,163.6 Balance at December 31 $ 23,149.0 $ 23,222.0 $ 23,249.5 The majority of the net balances are related to disability claims with long-tail payouts on which interest earned on assets backing liabilities is an integral part of pricing and reserving. Interest accrued on prior year reserves has been calculated on the opening reserve balance less one-half of the year’s claim payments relative to prior years at our average reserve discount rate for the respective periods. "Incurred Related to Prior Years - All Other Incurred" shown in the preceding chart includes the reserve adjustments as discussed in the following paragraphs, which impact the comparability between the years presented. Excluding those adjustments, the variability exhibited year over year is primarily caused by the level of claim resolutions in the period relative to the long-term expectations reflected in the reserves. Our claim resolution rate assumption used in determining reserves is our expectation of the resolution rate we will experience over the life of the block of business and will vary from actual experience in any one period, both favorably and unfavorably. 2018 Long-term Care Reserve Increase Policy reserves for our long-term care block of business are determined using the gross premium valuation method and, prior to the third quarter of 2018 , were valued based on assumptions established as of December 31, 2014, the date of our last assumption update under loss recognition. Gross premium valuation assumptions do not change after the date of loss recognition unless reserves are again determined to be deficient. We undertake a review of policy reserve adequacy annually during the fourth quarter of each year, or more frequently if appropriate, using best estimate assumptions as of the date of the review. During the third quarter of 2018 , we completed our annual review of policy reserve adequacy, which incorporated our most recent experience and included a review of all assumptions, including active policy terminations, claims incidence, claim terminations, morbidity, premium rate increases, and new money yield rates. The review utilized internal and external data and outside consulting firms for quality assurance and industry benchmarking. Based on our analysis, during the third quarter of 2018, we updated our reserve assumptions and determined that our policy and claim reserves should be increased by $750.8 million , or $593.1 million after tax, to reflect our current estimate of future benefit obligations. This increase was primarily driven by the update to our liability and interest rate assumptions, particularly claims incidence and claim termination rates, which resulted in an increase to reserves of approximately $2.2 billion . Partially offsetting the increase was the update to our assumptions for premium rate increases which decreased reserves approximately $1.4 billion , resulting in the net increase to reserves of $750.8 million . Of this amount, approximately $236.0 million was related to our liability for unpaid claims and claims adjustment expenses, which can be primarily attributed to prior year incurred claims, thereby impacting the results shown in the preceding chart. 2017 Unclaimed Death Benefits Reserve Increase Beginning in 2011, a number of state regulators began requiring insurers to cross-check specified insurance policies with the Social Security Administration's Death Master File to identify potential matches. If a potential match was identified, insurers were requested to determine if benefits were due, locate beneficiaries, and make payments where appropriate. We initiated this process where requested, and in 2012 we began implementing this process in all states on a forward-looking basis. In addition to implementing this on a forward-looking basis, in 2013 we began an initiative to search for potential claims from previous years. During 2013, we completed our assessment of benefits which we estimated would be paid under this initiative, and as such, established additional reserves for payment of these benefits. Similar to other insurers, we are undergoing an examination by a third party acting on behalf of a number of state treasurers concerning our compliance with the unclaimed property laws of the participating states. In the fourth quarter of 2017 , we started the process to reach a Global Resolution Agreement with the third party regarding settlement of the examination, which we finalized in January of 2018. During the fourth quarter of 2017 , we established reserves which reflect our estimate of the liability expected to be paid as we execute on the terms of the settlement. Claim reserves were increased $18.5 million for Unum US group life, $8.1 million for Unum US voluntary life, and $12.4 million for Colonial Life voluntary life, for a total reserve increase of $39.0 million before tax. The reserves established were attributed to prior years incurred claims, thereby impacting the results shown in the preceding chart. Reconciliation A reconciliation of policy and contract benefits and reserves for future policy and contract benefits as reported in our consolidated balance sheets to the liability for unpaid claims and claim adjustment expenses is as follows: December 31 2018 2017 2016 (in millions of dollars) Policy and Contract Benefits $ 1,695.7 $ 1,605.2 $ 1,507.9 Reserves for Future Policy and Contract Benefits 44,841.9 45,601.6 44,245.9 Total 46,537.6 47,206.8 45,753.8 Less: Life Reserves for Future Policy and Contract Benefits 8,330.9 8,231.3 8,078.2 Accident and Health Active Life Reserves 11,837.4 10,658.8 10,172.9 Adjustment Related to Unrealized Investment Gains and Losses 3,220.3 5,094.7 4,253.2 Liability for Unpaid Claims and Claim Adjustment Expenses $ 23,149.0 $ 23,222.0 $ 23,249.5 The adjustment related to unrealized investment gains and losses reflects the changes that would be necessary to policyholder liabilities if the unrealized investment gains and losses related to the corresponding available-for-sale securities had been realized. Changes in this adjustment are reported as a component of other comprehensive income or loss.

Income Tax

Income Tax	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Income Tax Disclosure	Total income tax expense (benefit) is allocated as follows: Year Ended December 31 2018 2017 2016 (in millions of dollars) Net Income $ 104.4 $ 409.8 $ 416.3 Stockholders' Equity - Additional Paid-in Capital Stock-Based Compensation — — (0.3 ) Stockholders' Equity - Accumulated Other Comprehensive Income (Loss) Change in Net Unrealized Gain on Securities Before Adjustment (614.2 ) 328.1 318.0 Change in Adjustment to Deferred Acquisition Costs and Reserves for Future Policy and Contract Benefits, Net of Reinsurance 371.7 (245.0 ) (200.6 ) Change in Net Gain on Hedges (8.2 ) (24.4 ) (25.4 ) Change in Foreign Currency Translation Adjustment (0.6 ) — — Change in Unrecognized Pension and Postretirement Benefit Costs 17.0 (8.3 ) (34.2 ) Total $ (129.9 ) $ 460.2 $ 473.8 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. Certain prior year amounts have been reclassified to conform to current year reporting. Year Ended December 31 2018 2017 2016 Statutory Income Tax 21.0 % 35.0 % 35.0 % Foreign Rate Differential, Inclusive of Foreign Rate Changes (0.3 ) (1.1 ) (2.2 ) U.S. Deferred Tax Liability Remeasurement — (7.0 ) — Deemed Repatriation Tax on Foreign Earnings and Profit (E&P) 1.8 4.7 — Tax Exempt Income (1.3 ) (0.8 ) (0.8 ) Tax Credits (2.4 ) (1.5 ) (1.6 ) Policyholder Reserves (2.4 ) — — Other Items, Net 0.2 (0.1 ) 0.5 Effective Tax 16.6 % 29.2 % 30.9 % Our net deferred tax (asset) liability consists of the following: December 31 2018 2017 (in millions of dollars) Deferred Tax Liability Deferred Acquisition Costs $ 129.7 $ 118.6 Fixed Assets 56.2 52.8 Invested Assets 493.4 1,074.0 Intangible Assets 24.0 6.5 Other 34.1 35.8 Gross Deferred Tax Liability 737.4 1,287.7 Deferred Tax Asset Reserves 668.5 908.0 Employee Benefits 179.5 188.7 Other 17.7 12.3 Gross Deferred Tax Asset 865.7 1,109.0 Less: Valuation Allowance 18.4 20.3 Net Deferred Tax Asset 847.3 1,088.7 Net Deferred Tax (Asset) Liability $ (109.9 ) $ 199.0 Our consolidated statements of income include amounts subject to both domestic and foreign taxation. The income and related tax expense (benefit) are as follows. The federal statutory rates used were 21 percent for 2018 and 35 percent for 2017 and 2016: Year Ended December 31 2018 2017 2016 (in millions of dollars) Income Before Tax Domestic $ 492.6 $ 1,289.0 $ 1,215.8 Foreign 135.2 115.0 131.9 Total $ 627.8 $ 1,404.0 $ 1,347.7 Current Tax Expense (Benefit) Federal $ 194.6 $ 374.9 $ 414.8 State and Local (0.6 ) 0.4 0.3 Foreign 33.4 26.0 (29.4 ) Total 227.4 401.3 385.7 Deferred Tax Expense (Benefit) Federal (114.6 ) 14.2 (14.6 ) State and Local (0.2 ) (0.3 ) (2.1 ) Foreign (8.2 ) (5.4 ) 47.3 Total (123.0 ) 8.5 30.6 Total Tax Expense $ 104.4 $ 409.8 $ 416.3 On December 22, 2017, the U.S. Federal government enacted the TCJA, which reduced the federal corporate tax rate from 35 percent to 21 percent effective January 1, 2018. Although the TCJA's 21 percent corporate tax rate became effective on January 1, 2018, we are required to adjust deferred tax assets and liabilities through continuing operations on the date of enactment. As a result, in 2017 we recorded an income tax benefit of $97.9 million for the TCJA's corporate tax rate reduction and an income tax expense of $66.4 million for the deemed repatriation transition tax on accumulated foreign E&P. TCJA brought a large number of complex changes to many areas of the tax code. The Securities and Exchange Commission issued Staff Accounting Bulletin No. 118 (SAB 118) allowing a one-year measurement period after the enactment date of TCJA to finalize the calculation and record the related tax impacts. We finalized and recorded adjustments to our initial estimates during 2018 . As a result of guidance from the IRS, we recorded additional deemed repatriation transition tax on accumulated foreign E&P of $ 11.5 million , for a total of $77.9 million . We recorded no other material changes to our calculations of the impact of the TCJA during the one-year measurement period after the enactment period as allowed by SAB 118. Effective January 1, 2018, the TCJA created a U.S. shareholder tax on certain foreign subsidiary income above a routine equity return on tangible depreciable business assets, or a tax on Global Intangible Low-taxed Income (GILTI). The FASB has provided additional guidance to address the accounting effects of GILTI, requiring companies to elect to either recognize deferred taxes related to GILTI or include in tax expense in the period incurred. We have elected to treat GILTI as a period cost. Under the TCJA, a modified territorial tax system was adopted that required a one-time deemed repatriation tax on accumulated foreign E&P. Future repatriation of foreign E&P subject to the one-time deemed repatriation tax will not be subject to further U.S. taxation other than tax on foreign currency translation gain or loss. As of December 31, 2018, our plans for the future repatriations of cash from our foreign subsidiaries include only the amount of capital above that which is required by Solvency II. The remainder of our investment in our foreign subsidiaries is indefinitely reinvested and we have not recorded any deferred taxes on the approximately $0.7 billion of the excess of the U.S. GAAP carrying values over the tax basis of investments in our foreign subsidiaries. Our consolidated statements of income include the following changes in unrecognized tax benefits. Certain prior year amounts have been reclassified to conform to current year reporting. December 31 2018 2017 2016 (in millions of dollars) Balance at Beginning of Year $ 1.4 $ 1.5 $ 0.8 Additions for Tax Positions Related to Prior Years 261.5 0.3 0.7 Additions for Tax Positions Related to Current Year — — — Settlements with Tax Authorities — — — Lapse of the Applicable Statute of Limitations (0.7 ) (0.4 ) — Balance at End of Year 262.2 1.4 1.5 Less Tax Attributable to Temporary Items Included Above (148.2 ) — — Total Unrecognized Tax Benefits That if Recognized Would Affect the Effective Tax Rate $ 114.0 $ 1.4 $ 1.5 During 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 . Included in the balance at December 31, 2018 , is $148.2 million of unrecognized tax benefits for which the ultimate deductibility is highly certain but for which there is uncertainty about the timing of such deductibility. It is reasonably possible that this item could reverse in the next 12 months following review by the Internal Revenue Service (IRS). We recognize interest expense and penalties, if applicable, related to unrecognized tax benefits in tax expense. We recognized a de minimis amount of interest expense related to unrecognized tax benefits during 2018 , 2017 and 2016 . We held a de minimis liability in our consolidated balance sheets for accrued interest related to unrecognized tax benefits at December 31, 2018 , 2017 and 2016 . We file federal and state income tax returns in the United States and in foreign jurisdictions. Tax years subsequent to 2014 remain subject to examination by the IRS. All other major foreign jurisdictions remain subject to examination for tax years subsequent to 2016 with the exception of Poland for which tax years subsequent to 2013 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 2013 remain subject to examination depending on the statute of limitation established by the various states, which is generally three to four years. Tax years subsequent to 2010 remain subject to examination in California. We have an accumulated federal net operating loss carryforward of $6.5 million as of December 31, 2018 and had none as of December 31, 2017 . Current year net operating losses relate to subsidiaries not yet included in the consolidated U.S. federal tax return and are not expected to expire unused. Our federal capital loss carryforward, also related to subsidiaries not included in the consolidated U.S. federal return, was $0.7 million at both December 31, 2018 and 2017 and is expected to be utilized by the time it expires in 2022 . We have net operating loss carryforwards for state and local income tax of approximately $195 million most of which is expected to expire unused between 2019 and 2038 . 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 $18.4 million and $20.3 million at December 31, 2018 and 2017 , 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. Total income taxes paid net of refunds during 2018 , 2017 , and 2016 were $139.7 million , $377.0 million , and $384.3 million , respectively.

Debt

Debt	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Debt Disclosure	Debt consists of the following: December 31 2018 2017 Interest Rates Maturities (in millions of dollars) Long-term Debt Outstanding Principal Senior Secured Notes issued 2007 Variable 2037 $ 140.0 $ 200.0 Senior Notes issued 1998 6.750 - 7.250% 2028 365.8 365.8 Senior Notes issued 2002 7.375% 2032 39.5 39.5 Senior Notes issued 2010 5.625% 2020 400.0 400.0 Senior Notes issued 2012 and 2016 5.750% 2042 500.0 500.0 Senior Notes issued 2014 4.000% 2024 350.0 350.0 Senior Notes issued 2015 3.875% 2025 275.0 275.0 Senior Notes issued 2016 3.000% 2021 350.0 350.0 Medium-term Notes issued 1990 - 1996 7.000 - 7.190% 2023 - 2028 50.8 50.8 Junior Subordinated Debt Securities issued 1998 7.405% 2038 226.5 226.5 Junior Subordinated Debt Securities issued 2018 6.250% 2058 300.0 — Fair Value Hedge Adjustment (5.1 ) (4.5 ) Less: Unamortized Net Premium 9.6 9.7 Unamortized Debt Issuance Costs (30.8 ) (24.4 ) Total Long-term Debt 2,971.3 2,738.4 Short-term Debt Outstanding Principal Senior Notes issued 1998 7.000% 2018 — 200.0 Less Unamortized Debt Issuance Costs — (0.1 ) Total Short-term Debt — 199.9 Total Debt $ 2,971.3 $ 2,938.3 Collateralized debt is comprised of our senior secured notes and ranks highest in priority, followed by unsecured notes, which consist of senior notes and medium-term notes, followed by junior subordinated debt securities. The medium-term notes are non-callable and the junior subordinated debt securities are callable under limited, specified circumstances. The remaining debt is callable and may be redeemed, in whole or in part, at any time. The aggregate contractual principal maturities are $400.0 million in 2020, $350.0 million in 2021, $2.0 million in 2023, and $2,245.6 million thereafter. Senior Secured Notes In 2007, Northwind Holdings, LLC (Northwind Holdings), a wholly-owned subsidiary of Unum Group, issued $800.0 million of insured, senior secured notes (the Northwind notes) in a private offering. The Northwind notes bear interest at a floating rate equal to the three-month LIBOR plus 0.78% . Northwind Holdings’ ability to meet its obligations to pay principal, interest, and other amounts due on the Northwind notes will be dependent principally on its receipt of dividends from Northwind Reinsurance Company (Northwind Re), the sole subsidiary of Northwind Holdings. Northwind Re reinsured the risks attributable to specified individual disability insurance policies issued by or reinsured by Provident Life and Accident Insurance Company, Unum Life Insurance Company of America, and The Paul Revere Life Insurance Company (collectively, the ceding insurers) pursuant to separate reinsurance agreements between Northwind Re and each of the ceding insurers. The ability of Northwind Re to pay dividends to Northwind Holdings will depend on its satisfaction of applicable regulatory requirements and the performance of the reinsured policies. Recourse for the payment of principal, interest and other amounts due on the Northwind notes is limited to the collateral for the Northwind notes and the other assets, if any, of Northwind Holdings. The collateral consists of a first priority, perfected security interest in (a) the debt service coverage account (DSCA) that Northwind Holdings is required to maintain in accordance with the indenture pursuant to which the Northwind notes were issued (the Northwind indenture), (b) the capital stock of Northwind Re and the dividends and distributions on such capital stock, and (c) Northwind Holdings' rights under the transaction documents related to the Northwind notes to which Northwind Holdings is a party. At December 31, 2018 , the amount in the DSCA was $73.8 million . None of Unum Group, the ceding insurers, Northwind Re, or any other affiliate of Northwind Holdings is an obligor or guarantor with respect to the Northwind notes. Northwind Holdings is required to repay a portion of the outstanding principal under the Northwind notes at par on the quarterly scheduled payment dates under the Northwind notes in an amount equal to the lesser of (i) a targeted amortization amount as defined in the Northwind indenture and (ii) the amount of the remaining available funds in the DSCA minus an amount equal to the minimum balance that is required to be maintained in the DSCA under the Northwind indenture, provided that Northwind Holdings has sufficient funds available to pay its other expenses, including interest payments on the Northwind notes, and to maintain the minimum balance in the DSCA as required under the Northwind indenture. Northwind Holdings made principal payments on the Northwind notes of $60.0 million in both 2018 and 2017 , and $64.0 million in 2016 . In 2017, we purchased and retired the remaining $3.4 million of principal on our senior secured floating rate notes acquired through our purchase of Starmount Life Insurance Company. In conjunction with this retirement, we also terminated the interest rate swap associated with the hedge of these notes and recorded a $0.1 million loss in our consolidated statements of income as a component of net realized investment gains and losses. See Note 4 for further discussion on the interest rate swap. Unsecured Notes In July 2018, our $200.0 million 7.00% senior unsecured notes matured. In September 2016, our $350.0 million 7.125% senior unsecured notes matured. In May 2016, we issued a total of $600.0 million aggregate principal amount of senior notes: (i) $350.0 million aggregate principal amount of senior notes due in 2021 with an annual coupon rate of 3.00% , and (ii) $250.0 million aggregate principal amount of senior notes due in 2042 with an annual coupon rate of 5.75% , pursuant to a reopening of the $250.0 million aggregate principal amount outstanding of our 5.75% senior notes due 2042 issued in 2012. Both issuances are callable at or above par and rank equally in the right of payment with all of our other unsecured and unsubordinated debt. Fair Value Hedges As of December 31, 2018 and 2017 , we had $250.0 million notional amount of an interest rate swap which effectively converts certain of our unsecured senior notes into floating rate debt. Under this agreement, we receive a fixed rate of interest and pay a variable rate of interest, based off of three-month LIBOR. See Note 4 for further information on the interest rate swap. Junior Subordinated Debt Securities In May 2018, we issued $300.0 million of 6.25% junior subordinated notes due 2058. The notes are redeemable at or above par on or after June 15, 2023 and rank equally in the right of payment with our other junior subordinated debt securities. In 1998, Provident Financing Trust I (the trust), a 100 percent -owned finance subsidiary of Unum Group, issued $300.0 million of 7.405% capital securities 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. Unum Group issued 7.405% junior subordinated deferrable interest debentures to the trust in connection with the capital securities offering. The debentures mature in 2038. The sole assets of the trust are the junior subordinated debt securities. Interest Paid Interest paid on long-term and short-term debt and related securities during 2018 , 2017 , and 2016 was $167.3 million , $154.4 million , and $153.6 million , respectively. Credit Facility In March 2016, we amended the terms of our five -year, $400.0 million unsecured revolving credit facility, which was previously set to expire in 2018, to extend through March 2021. Under the terms of the agreement, we may request that the credit facility be increased up to $600.0 million . Borrowings under the credit facility are for general corporate uses and are subject to financial covenants, negative covenants, and events of default that are customary. The credit facility provides for borrowing at an interest rate based either on the prime rate or LIBOR. In addition, the credit facility provides for the issuance of letters of credit subject to certain terms and limitations. At December 31, 2018 and 2017 , letters of credit totaling $2.1 million had been issued from the credit facility, but there were no borrowed amounts outstanding.

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2018
Retirement Benefits [Abstract]
Pension and Other Postretirement Benefits Disclosure	Employee Benefit Plans Defined Benefit Pension and Other Postretirement Benefit (OPEB) Plans We sponsor several defined benefit pension and OPEB plans for our employees, including non-qualified pension plans. The U.S. qualified and non-qualified defined benefit pension plans comprise the majority of our total benefit obligation and benefit cost. We maintain a separate defined benefit plan for eligible employees in our U.K. operation. The U.S. defined benefit pension plans were closed to new entrants on December 31, 2013, the OPEB plan was closed to new entrants on December 31, 2012, and the U.K. plan was closed to new entrants on December 31, 2002. Amendments to Pension Plan In 2017 , we amended our U.S. qualified defined benefit pension plan by modifying the qualified pre-retirement survivor annuity form of payment for married participants from a 67 percent joint and survivor annuity to a 100 percent joint and survivor benefit to the participant's spousal beneficiary in the event a participant pre-deceased prior to reaching pension eligibility and affirmatively electing a form of benefit. This amendment became effective January 1, 2018. As a result of this amendment, we recognized an increase in the net pension liability of $7.6 million , with a corresponding prior service cost included in accumulated other comprehensive income. Amendment to OPEB Plan Effective August 1, 2016, we amended the retiree medical benefits portion of our OPEB plan to transition a majority of participants to a private exchange for their health insurance coverage. Prior to the plan amendment, participants paid a subsidized premium for their health insurance coverage, but if they elect to continue participation in the plan they will now purchase coverage on a private exchange and will subsequently be reimbursed through a Health Reimbursement Account (HRA) for an amount equivalent to the subsidy that was previously provided. Participants who continued in the plan received a one-time subsidy to minimize the initial out-of-pocket cost of purchasing health insurance. The amendment did not materially change the benefit obligation of the plan. Amortization Period of Actuarial Gain or Loss and Prior Service Cost or Credit Because all participants in the U.S. and U.K. pension plans are considered inactive, we amortize the net actuarial loss and prior service credit for these plans over the average remaining life expectancy of the plans. As of December 31, 2018 , the estimate of the average remaining life expectancy of the plans was approximately 24 years for the U.S. plan and 31 years for U.K. plan. The following table provides the changes in the benefit obligation and fair value of plan assets and the funded status of the plans. Pension Benefits U.S. Plans U.K. Plan OPEB 2018 2017 2018 2017 2018 2017 (in millions of dollars) Change in Benefit Obligation Benefit Obligation at Beginning of Year $ 2,136.9 $ 1,955.3 $ 243.8 $ 223.0 $ 139.5 $ 147.9 Service Cost 9.1 7.9 — — — — Interest Cost 79.8 84.5 5.9 6.2 4.9 5.9 Plan Participant Contributions — — — — 0.2 0.2 Actuarial (Gain) Loss (210.3 ) 159.3 (18.9 ) 1.7 (7.6 ) (4.2 ) Benefits and Expenses Paid (82.2 ) (77.7 ) (7.3 ) (8.3 ) (11.1 ) (10.3 ) Plan Amendment — 7.6 0.3 — — — Change in Foreign Exchange Rates — — (12.8 ) 21.2 — — Benefit Obligation at End of Year $ 1,933.3 $ 2,136.9 $ 211.0 $ 243.8 $ 125.9 $ 139.5 Accumulated Benefit Obligation at December 31 $ 1,933.3 $ 2,136.9 $ 205.0 $ 234.3 N/A N/A Change in Fair Value of Plan Assets Fair Value of Plan Assets at Beginning of Year $ 1,582.6 $ 1,454.1 $ 253.5 $ 228.4 $ 10.5 $ 10.8 Actual Return on Plan Assets (53.6 ) 198.5 (16.0 ) 11.6 0.1 0.1 Employer Contributions 8.1 7.7 — — 10.4 9.7 Plan Participant Contributions — — — — 0.2 0.2 Benefits and Expenses Paid (82.2 ) (77.7 ) (7.3 ) (8.3 ) (11.1 ) (10.3 ) Change in Foreign Exchange Rates — — (13.2 ) 21.8 — — Fair Value of Plan Assets at End of Year $ 1,454.9 $ 1,582.6 $ 217.0 $ 253.5 $ 10.1 $ 10.5 Underfunded (Overfunded) Status $ 478.4 $ 554.3 $ (6.0 ) $ (9.7 ) $ 115.8 $ 129.0 The amounts recognized in our consolidated balance sheets for our pension and OPEB plans at December 31, 2018 and 2017 are as follows. Pension Benefits U.S. Plans U.K. Plan OPEB 2018 2017 2018 2017 2018 2017 (in millions of dollars) Current Liability $ 7.3 $ 7.2 $ — $ — $ 1.6 $ 1.2 Noncurrent Liability 471.1 547.1 — — 114.2 127.8 Noncurrent Asset — — (6.0 ) (9.7 ) — — Underfunded (Overfunded) Status $ 478.4 $ 554.3 $ (6.0 ) $ (9.7 ) $ 115.8 $ 129.0 Unrecognized Pension and Postretirement Benefit Costs Net Actuarial Gain (Loss) $ (672.6 ) $ (746.4 ) $ (48.9 ) $ (46.3 ) $ 20.9 $ 13.7 Prior Service Credit (Cost) (0.7 ) (0.7 ) (0.3 ) — 3.3 3.5 (673.3 ) (747.1 ) (49.2 ) (46.3 ) 24.2 17.2 Income Tax 236.0 251.8 11.9 11.6 3.2 4.7 Total Included in Accumulated Other Comprehensive Income (Loss) $ (437.3 ) $ (495.3 ) $ (37.3 ) $ (34.7 ) $ 27.4 $ 21.9 The following table provides the changes recognized in other comprehensive income for the years ended December 31, 2018 and 2017 . Pension Benefits U.S. Plans U.K. Plan OPEB 2018 2017 2018 2017 2018 2017 (in millions of dollars) Accumulated Other Comprehensive Income (Loss) at Beginning of Year $ (495.3 ) $ (451.3 ) $ (34.7 ) $ (33.1 ) $ 21.9 $ 19.3 Net Actuarial Gain (Loss) Amortization 21.7 19.6 0.6 0.7 — — All Other Changes 52.1 (63.9 ) (3.2 ) (3.0 ) 7.2 3.6 Prior Service Credit (Cost) Amortization — (0.3 ) — — (0.2 ) (0.4 ) Plan Amendment — (7.6 ) (0.3 ) — — — Change in Income Tax (15.8 ) 8.2 0.3 0.7 (1.5 ) (0.6 ) Accumulated Other Comprehensive Income (Loss) at End of Year $ (437.3 ) $ (495.3 ) $ (37.3 ) $ (34.7 ) $ 27.4 $ 21.9 Plan Assets The objective of our U.S. pension and OPEB plans is to maximize long-term return, within acceptable risk levels, in a manner that is consistent with the fiduciary standards of the Employee Retirement Income Security Act (ERISA), while maintaining sufficient liquidity to pay current benefits and expenses. Our U.S. qualified defined benefit pension plan assets include a diversified blend of domestic, international, global, and emerging market equity securities, fixed income securities, opportunistic credit securities, real estate investments, alternative investments, and cash equivalents. Equity securities are comprised of funds and individual securities that are benchmarked against the respective indices specified below. International and global equity funds may allocate a certain percentage of assets to forward currency contracts. Fixed income securities include U.S. government and agency asset-backed securities, corporate investment-grade bonds, private placement securities, and bonds issued by states or other municipalities. Opportunistic credits consist of investments in funds that hold varied fixed income investments purchased at depressed values with the intention to later sell those investments for a gain. Real estate investments consist primarily of funds that hold commercial real estate investments. Alternative investments, which include private equity direct investments, private equity funds of funds, and hedge funds of funds, utilize proprietary strategies that are intended to have a low correlation to the U.S. stock market. Prohibited investments include, but are not limited to, unlisted securities, futures contracts, options, short sales, and investments in securities issued by Unum Group or its affiliates. The invested asset classes, asset types, and benchmark indices for our U.S. qualified defined benefit pension plan is as follows. We target approximately 36 percent to equity securities, 40 percent to fixed income securities, and 24 percent to opportunistic credits, alternative, and real estate investments. Asset Class Asset Type Benchmark Indices Equity Securities Collective funds; Individual holdings Standard & Poor's 500; Russell 2000 Value and Growth; MSCI Europe Australasia Far East Small Cap; MSCI Emerging Markets; MSCI World and World Minimum Volatility; FTSE RAFI All-World Low Volatility Fixed Income Individual holdings Bloomberg Barclays Long Government/Corporate Index Opportunistic Credits Collective fund Custom Index Real Estate Collective fund National Council of Real Estate Investment Fund Open-end Diversified Core Equity Index Alternative Investments (Hedge and Private Equity) Fund of funds; Direct investments Hedge Fund Research Institute Fund of Funds; Russell 2000 Assets for our U.K. pension plan are primarily invested in a pooled diversified growth fund. This fund invests in assets such as global equities, hedge funds, commodities, below-investment-grade fixed income securities, and currencies. The objectives of the fund are to generate capital appreciation over the course of a complete economic and market cycle and to deliver equity-like returns in the medium-to-long term while maintaining approximately two thirds of the volatility of equity markets. Performance of this fund is measured against the U.K. inflation rate plus four percent. The remaining assets in the U.K. plan are invested in leveraged interest rate and inflation swap and gilt funds of varying durations designed to broadly match the interest rate and inflation sensitivities of the plan's liabilities. The current target allocation for the assets is 65 percent diversified growth assets and 35 percent interest rate and inflation swap funds. There are no categories of investments that are specifically prohibited by the U.K. plan, but there are general guidelines that ensure prudent investment action is taken. Such guidelines include the prevention of the plan from using derivatives for speculative purposes and limiting the concentration of risk in any one type of investment. Assets for the OPEB plan are invested in life insurance contracts issued by one of our insurance subsidiaries. The assets support life insurance benefits payable to certain former retirees covered under the OPEB plan. The terms of these contracts are consistent in all material respects with those the subsidiary offers to unaffiliated parties that are similarly situated. There are no categories of investments specifically prohibited by the OPEB plan. We believe our investment portfolios are well diversified by asset class and sector, with no undue risk concentrations in any one category. The categorization of fair value measurements by input level for the invested assets in our U.S. pension plans is shown below. The carrying values of investment-related receivables and payables approximate fair value due to the short-term nature of the securities and are not included in the following chart. Investments valued using net asset value (NAV) as a practical expedient are not required to be categorized by input level, but these investments are included as follows to reconcile to total invested assets. December 31, 2018 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) NAV as a Practical Total (in millions of dollars) Invested Assets Equity Securities: U.S. Large Cap $ — $ — $ — $ 83.0 $ 83.0 U.S. Small Cap 18.9 — — — 18.9 Global — — — 290.3 290.3 International — — — 24.6 24.6 Emerging Markets — — — 44.1 44.1 Fixed Income Securities: U.S. Government and Agencies 257.4 — — — 257.4 Corporate — 311.2 — — 311.2 State and Municipal Securities — 5.7 — — 5.7 Opportunistic Credits — — — 192.0 192.0 Real Estate — — — 102.8 102.8 Alternative Investments: Private Equity Direct Investments — — — 53.5 53.5 Private Equity Funds of Funds — — — 34.0 34.0 Hedge Funds of Funds — — — 0.1 0.1 Cash Equivalents 39.2 — — — 39.2 Total Invested Assets $ 315.5 $ 316.9 $ — $ 824.4 $ 1,456.8 December 31, 2017 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) NAV as a Practical Total (in millions of dollars) Invested Assets Equity Securities: U.S. Large Cap $ — $ — $ — $ 103.3 $ 103.3 U.S. Small Cap 45.2 — — — 45.2 Global — — — 325.9 325.9 International — — — 35.7 35.7 Emerging Markets — — — 61.5 61.5 Fixed Income Securities: U.S. Government and Agencies 248.5 11.9 — — 260.4 Corporate — 335.5 — — 335.5 State and Municipal Securities — 6.3 — — 6.3 Opportunistic Credits — — — 193.3 193.3 Real Estate — — — 96.1 96.1 Alternative Investments: Private Equity Direct Investments — — — 45.1 45.1 Private Equity Funds of Funds — — — 34.5 34.5 Hedge Funds of Funds — — — 0.2 0.2 Cash Equivalents 32.0 — — — 32.0 Total Invested Assets $ 325.7 $ 353.7 $ — $ 895.6 $ 1,575.0 Level 1 investments consist of individual holdings that are valued based on unadjusted quoted prices from active markets for identical securities. Level 2 investments consist of individual holdings that are valued using observable inputs through market corroborated pricing. Certain equity, opportunistic credit, and real estate investments are valued based on the NAV of the underlying holdings. We made no adjustments to the NAV for 2018 or 2017 . These investments have no unfunded commitments and no specific redemption restrictions. Alternative investments are valued based on NAV in a period ranging from one month to one quarter in arrears. We evaluate the need for adjustments to the NAV based on market conditions and discussions with fund managers in the period subsequent to the valuation date and prior to issuance of the financial statements. We made no adjustments to the NAV for 2018 or 2017 . 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 and eight years from the formation of the fund. The categorization of fair value measurements by input level for the invested assets in our U.K. pension plan is shown below. Investments valued using NAV as a practical expedient are not required to be categorized by input level, but these investments are included as follows to reconcile to total invested assets. December 31, 2018 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) NAV as a Practical Total (in millions of dollars) Plan Assets Diversified Growth Assets $ — $ — $ — $ 133.0 $ 133.0 Fixed Interest and Index-linked Securities 81.3 — — — 81.3 Cash Equivalents 2.7 — — — 2.7 Total Plan Assets $ 84.0 $ — $ — $ 133.0 $ 217.0 December 31, 2017 Quoted Prices Significant Significant NAV as a Practical Total (in millions of dollars) Plan Assets Diversified Growth Assets $ — $ — $ — $ 154.7 $ 154.7 Fixed Interest and Index-linked Securities 98.4 — — — 98.4 Cash Equivalents 0.4 — — — 0.4 Total Plan Assets $ 98.8 $ — $ — $ 154.7 $ 253.5 Level 1 fixed interest and index-linked securities consist of individual funds that are valued based on unadjusted quoted prices from active markets for identical securities. Diversified growth assets are valued based on the NAV of the underlying holdings. We made no adjustments to the NAV for 2018 or 2017 . These investments have no unfunded commitments and no specific redemption restrictions. The categorization of fair value measurements by input level for the assets in our OPEB plan is as follows: December 31, 2018 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total (in millions of dollars) Assets Life Insurance Contracts $ — $ — $ 10.1 $ 10.1 December 31, 2017 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total (in millions of dollars) Assets Life Insurance Contracts $ — $ — $ 10.5 $ 10.5 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, 2018 and 2017 are as follows: Year Ended December 31, 2018 Beginning of Year Actual Return on Plan Assets Contributions Net Benefits and Expenses Paid End of Year (in millions of dollars) Life Insurance Contracts $ 10.5 $ 0.1 $ 10.6 $ (11.1 ) $ 10.1 Year Ended December 31, 2017 Beginning of Year Actual Return on Plan Assets Contributions Net Benefits and Expenses Paid End of Year (in millions of dollars) Life Insurance Contracts $ 10.8 $ 0.1 $ 9.9 $ (10.3 ) $ 10.5 For the years ended December 31, 2018 and 2017 , 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 2018 or 2017 . 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 2018 2017 2018 2017 2018 2017 Benefit Obligations Discount Rate 4.40 % 3.80 % 2.90 % 2.50 % 4.40 % 3.70 % Rate of Compensation Increase N/A N/A 3.70 % 3.70 % N/A N/A Net Periodic Benefit Cost Discount Rate 3.80 % 4.40 % 2.50 % 2.70 % 3.70 % 4.20 % Expected Return on Plan Assets 6.75 % 7.25 % 3.90 % 3.90 % 5.75 % 5.75 % Rate of Compensation Increase N/A N/A 3.70 % 3.80 % N/A N/A We set the discount rate assumption annually for each of our retirement-related benefit plans at the measurement date to reflect the yield on a portfolio of high quality fixed income corporate debt instruments matched against the projected cash flows for future benefits. Our long-term rate of return on plan assets assumption is selected from a range of probable return outcomes from an analysis of the asset portfolio. Our expectations for the future investment returns of the asset categories are based on a combination of historical market performance, evaluations of investment forecasts obtained from external consultants and economists, and current market yields. The methodology underlying the return assumption includes the various elements of the expected return for each asset class such as long-term rates of return, volatility of returns, and the correlation of returns between various asset classes. The expected return for the total portfolio is calculated based on the plan's strategic asset allocation. Investment risk is measured and monitored on an ongoing basis through annual liability measurements, periodic asset/liability studies, and quarterly investment portfolio reviews. Risk tolerance is established through consideration of plan liabilities, plan funded status, and corporate financial condition. Our mortality rate assumption reflects our best estimate, as of the measurement date, of the life expectancies of plan participants in order to determine the expected length of time for benefit payments. We derive our assumptions from industry mortality tables. The expected return assumption for the life insurance reserve for our OPEB plan is based on full investment in fixed income securities with an average book yield of 4.73 percent and 4.76 percent in 2018 and 2017 , respectively. The rate of compensation increase assumption for our U.K. pension plan is generally based on periodic studies of compensation trends. At December 31, 2018 and 2017 , the annual rates of increase in the per capita cost of covered postretirement health care benefits assumed for the next calendar year are 7.00 percent for benefits payable to both retirees prior to Medicare eligibility as well as Medicare eligible retirees. The rates are assumed to change gradually to 5.00 percent by 2024 for measurement at December 31, 2018 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 2018 2017 2016 2018 2017 2016 2018 2017 2016 (in millions of dollars) Service Cost $ 9.1 $ 7.9 $ 7.0 $ — $ — $ — $ — $ — $ — Interest Cost 79.8 84.5 85.2 5.9 6.2 7.0 4.9 5.9 7.2 Expected Return on Plan Assets (104.5 ) (103.1 ) (102.8 ) (8.9 ) (8.8 ) (10.0 ) (0.6 ) (0.6 ) (0.6 ) Amortization of: Net Actuarial Loss 21.7 19.6 16.2 0.6 0.7 0.1 — — — Prior Service Credit — (0.3 ) (0.3 ) — — — (0.2 ) (0.4 ) (0.2 ) Plan Amendment — — — — — — — — 0.9 Total Net Periodic Benefit Cost $ 6.1 $ 8.6 $ 5.3 $ (2.4 ) $ (1.9 ) $ (2.9 ) $ 4.1 $ 4.9 $ 7.3 The service cost component of net periodic pension and postretirement benefit cost is included as a component of compensation expense in our consolidated statements of income. All other components of net periodic pension and postretirement benefit cost are included in other expenses. A one percent increase or decrease in the assumed health care cost trend rate at December 31, 2018 would have increased (decreased) the service cost and interest cost by a de minimis amount, respectively, and the postretirement benefit obligation by $0.6 million and $(0.5) million , respectively. The unrecognized net actuarial loss and the prior service credit included in accumulated other comprehensive income and expected to be amortized and included in net periodic pension cost during 2019 is $18.4 million and $0.2 million before tax, respectively. 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 2019 $ 77.1 $ 5.3 $ 12.1 $ 0.2 $ 11.9 2020 80.2 5.3 11.7 0.2 11.5 2021 83.8 5.6 11.2 0.1 11.1 2022 87.2 5.9 10.7 0.2 10.5 2023 90.9 6.4 10.1 0.1 10.0 2024-2028 513.7 39.4 43.7 0.4 43.3 Funding Policy The funding policy for our U.S. qualified defined benefit plan is to contribute annually an amount at least equal to the minimum annual contribution required under ERISA and other applicable laws, but generally not greater than the maximum amount that can be deducted for federal income tax purposes. We had no regulatory contribution requirements for our U.S. qualified defined benefit plan in 2018 and made a de minimis amount of voluntary contributions during 2018 . We do not expect to make any contributions in 2019 . The funding policy for our U.S. non-qualified defined benefit pension plan is to contribute the amount of the benefit payments made during the year. Our expected return on plan assets and discount rate will not affect the cash contributions we are required to make to our U.S. pension plan because such contributions are determined under the minimum funding requirements as set forth in ERISA. We made no contributions to our U.K. plan during 2018 , nor do we expect to make any contributions in 2019 , either voluntary or those required to meet the minimum funding requirements under U.K. legislation. Our OPEB plan represents a non-vested, non-guaranteed obligation, and current regulations do not require specific funding levels for these benefits, which are comprised of retiree life, medical, and dental benefits. It is our practice to use general assets to pay medical and dental claims as they come due in lieu of utilizing plan assets for the medical and dental benefit portions of our OPEB plan. Defined Contribution Plans We offer a 401(k) plan to all eligible U.S. employees under which a portion of employee contributions is matched. We match dollar-for-dollar up to 5.0 percent of base salary and any recognized sales and performance-based incentive compensation for employee contributions into the plan. We also make an additional non-elective contribution of 4.5 percent of earnings for all eligible employees and a separate transition contribution for eligible employees who met certain age and years of service criteria as of December 31, 2013. The 401(k) plan remains in compliance with ERISA guidelines and continues to qualify for a “safe harbor” from annual discrimination testing. We also offer a defined contribution plan to all eligible U.K. employees under which a portion of employee contributions is matched. We match two pounds for every one pound on the first 1.0 percent of employee contributions into the plan and match additional employee contributions pound-for-pound up to 5.0 percent of base salary. We also make an additional non-elective contribution of 6.0 percent of base salary for all eligible employees who met certain age and years of service criteria as of March 31, 2016. During the years ended December 31, 2018 , 2017 , and 2016 , we recognized costs of $72.7 million , $78.4 million , and $72.2 million , respectively, for our U.S. defined contribution plan. We recognized costs of $4.2 million in both 2018 and 2017 , and $4.9 million in 2016 for our U.K. defined contribution plan.

Stockholders' Equity and Earnin

Stockholders' Equity and Earnings Per Common Share	12 Months Ended
	Dec. 31, 2018
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 2018 2017 2016 (in millions of dollars, except share data) Numerator Net Income $ 523.4 $ 994.2 $ 931.4 Denominator (000s) Weighted Average Common Shares - Basic 219,635.6 226,492.4 235,445.7 Dilution for Assumed Exercises of Stock Options and Nonvested Stock Awards 423.0 842.8 533.5 Weighted Average Common Shares - Assuming Dilution 220,058.6 227,335.2 235,979.2 Net Income Per Common Share Basic $ 2.38 $ 4.39 $ 3.96 Assuming Dilution $ 2.38 $ 4.37 $ 3.95 We use the treasury stock method to account for the effect of outstanding stock options, nonvested restricted stock units, and nonvested performance share units on the computation of diluted earnings per share. Under this method, these potential common shares will each have a dilutive effect, as individually measured, when the average market price of Unum Group common stock during the period exceeds the exercise price of the stock options and the grant price of the nonvested restricted stock units and the nonvested performance share units. The outstanding stock options have exercise prices ranging from $23.35 to $26.29 ; the nonvested restricted stock units have grant prices ranging from $27.85 to $55.26 ; and the nonvested performance share units have grant prices ranging from $27.85 to $49.86 . See Note 11. In computing earnings per share assuming dilution, only potential common shares that are dilutive (those that reduce earnings per share) are included. Potential common shares not included in the computation of diluted earnings per share because the impact would be antidilutive, based on then current market prices, approximated 0.6 million , 0.3 million , and 0.4 million for the years ended December 31, 2018 , 2017 , and 2016 , respectively.
Stockholders' Equity Disclosure	Common Stock Our board of directors has authorized the repurchase of Unum Group's common stock under the following repurchase programs: Share Repurchase Program Authorized During May 2018 May 2017 May 2016 (in millions of dollars) Authorized Repurchase Amount $ 750.0 $ 750.0 $ 750.0 Remaining Repurchase Amount at Year End 2018 $ 500.0 $ — $ — The May 2018 share repurchase program has an expiration date of November 24, 2019 . 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 2018 2017 2016 (in millions) Shares Repurchased 8.7 8.2 11.9 Cost of Shares Repurchased (1) $ 350.7 $ 400.4 $ 403.3 (1) Includes commissions of $0.7 million , $0.3 million , and $0.2 million for the years ended December 31, 2018 , 2017 , and 2016 , respectively. Preferred Stock Unum Group has 25.0 million shares of preferred stock authorized with a par value of $0.10 per share. No preferred stock has been issued to date.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Disclosure of Compensation Related Costs, Share-based Payments	Stock-Based Compensation Description of Stock Plans Under the Stock Incentive Plan of 2017 (the 2017 Plan), up to 17 million shares of common stock are available for awards to our employees, officers, consultants, and directors. Awards may be in the form of stock options, stock appreciation rights, restricted stock, restricted stock units, performance share units, and other stock-based awards. Each full-value award, defined as any award other than a stock option or stock appreciation right, is counted as 1.76 shares. The exercise price for stock options issued cannot be less than the fair value of the underlying common stock as of the grant date. Stock options generally have a term of eight years after the date of grant and fully vest after three years. At December 31, 2018 , approximately 15.7 million shares were available for future grants under the 2017 Plan. Under the Stock Incentive Plan of 2012 (the 2012 Plan), which was terminated in May 2017 for the purposes of any further grants, up to 20 million shares of common stock were available for awards to our employees, officers, consultants, and directors. Awards could be in the form of stock options, stock appreciation rights, restricted stock, restricted stock units, performance share units, and other stock-based awards. Each full-value award, defined as any award other than a stock option or stock appreciation right, is counted as 1.76 shares. Awards granted before the termination of the 2012 Plan remain outstanding in accordance with the plan's terms. Stock options generally have a term of eight years after the date of grant and fully vest after three years. Under the Stock Incentive Plan of 2007 (the 2007 Plan), which was terminated in May 2012 for purposes of any further grants, up to 35 million shares of common stock were available for awards to our employees, officers, consultants, and directors. Awards could be in the form of stock options, stock appreciation rights, restricted stock, restricted stock units, performance share units, and other stock-based awards. Each full-value award, defined as any award other than a stock option or stock appreciation right, is counted as 2.7 shares. Awards granted before the termination of the 2007 Plan remain outstanding in accordance with the plan's terms. Stock options generally have a term of eight years after the date of grant and fully vest after three years. We issue new shares of common stock for all of our stock plan vestings and exercises. Performance Share Units (PSUs) Activity for PSUs classified as equity is as follows: Weighted Average Shares Grant Date (000s) Fair Value Outstanding at December 31, 2017 331 $ 37.62 Granted 255 44.19 Vested (301 ) 30.18 Forfeited (2 ) 46.79 Outstanding at December 31, 2018 283 51.33 During 2018 , 2017 , and 2016 , we issued PSUs with a weighted average grant date fair value per share of $44.19 , $51.37 , and $28.41 , respectively. Vesting for the PSUs occurs at the end of a three-year period and is contingent upon our achievement of prospective company performance goals and our total shareholder return relative to a board-approved peer group during the three -year period. Actual perform ance, including modification for relative total shareholder return, may result in the ultimate award of 40 to 180 percent of the initial number of PSUs issued, with the potential for no award if company performance goals are not achieved during the three-year period. Forfeitable dividend equivalents on PSUs are accrued in the form of additional PSUs. PSU shares in the preceding table represent aggregate initial target awards and accrued dividend equivalents and do not reflect potential increases or decreases resulting from the application of the performance factor determined after the end of the performance periods. At December 31, 2018 , the three -year performance period for the 2016 PSU grant was completed and the related shares vested, but the performance factor had not yet been applied. The performance factor will be applied during the first quarter of 2019 , with distribution of the stock thereafter. Granted and vested amounts in the preceding table also include the additional shares awarded as a result of the application of the performance factor to the 2015 PSU grant, which occurred during the first quarter of 2018. At December 31, 2018 , w e had approximately $5.9 million of unrecognized compensation cost related to PSUs that will be recognized over a weighted average period of 1.6 years . The estimated compensation expense is adjusted for actual performance experience and is recognized ratably during the service period, or remaining service period, if and when it becomes probable that the performance conditions will be satisfied. Compensation cost for PSUs subject to accelerated vesting at the date of retirement eligibility is recognized over the implicit service period. The fair value of PSUs is estimated on the date of initial grant using the Monte-Carlo simulation m odel. Key assumptions used to value PSUs granted during the years shown are as follows: Year Ended December 31 2018 2017 2016 Expected Volatility (based on our and our peer group historical daily stock prices) 24 % 24 % 22 % Expected Life (equals the performance period) 3.0 years 3.0 years 3.0 years Risk Free Interest Rate (based on U.S. Treasury yields at the date of grant) 2.32 % 1.52 % 0.88 % Restricted Stock Units (RSUs) Activity for RSUs classified as equity is as follows: Weighted Average Shares Grant Date (000s) Fair Value Outstanding at December 31, 2017 871 $ 38.75 Granted 496 47.76 Vested (486 ) 37.32 Forfeited (54 ) 44.65 Outstanding at December 31, 2018 827 44.62 During 2018 , 2017 , and 2016 , we issued RSUs with a weighted average grant date fair value per share of $47.76 , $48.92 , and $28.80 , respectively. RSUs vest over a one to three -year service period, beginning at the date of grant, and the compensation cost is recognized ratably during the vesting period. Forfeitable dividend equivalents on RSUs are accrued in the form of additional RSUs. Compensation cost for RSUs subject to accelerated vesting at the date of retirement eligibility is recognized over the implicit service period. The total fair value of shares vested during 2018 , 2017 , and 2016 was $18.1 million , $13.3 million , and $18.3 million , respectively. At December 31, 2018 , we had $16.5 million of unrecognized compensation cost related to RSUs that will be recognized over a weighted average period of 0.9 years. Stock Options Stock option activity is summarized as follows: Remaining Intrinsic Shares Weighted Average Contractual Term Value (000s) Exercise Price (in years) (in millions) Outstanding at December 31, 2017 124 $ 23.86 Exercised (19 ) 20.78 Outstanding at December 31, 2018 105 24.41 1.4 $ 0.5 Exercisable at December 31, 2018 105 $ 24.41 1.4 $ 0.5 All outstanding stock options at December 31, 2018 have vested. Stock options vest over a one to three -year service period, beginning at the date of grant, and the compensation cost is recognized ratably during the vesting period. Compensation cost for stock options subject to accelerated vesting at the date of retirement eligibility is recognized over the implicit service period. At December 31, 2018 , we had no unrecognized compensation cost related to stock options. The intrinsic value of options exercised and fair value of options vested are as follows: Year Ended December 31 2018 2017 2016 (in millions of dollars) Total Intrinsic Value of Options Exercised $ 0.7 $ 10.0 $ 3.4 Total Fair Value of Options Vested $ — $ — $ 0.1 There were no stock options granted in the years 2016 through 2018 . Expense Compensation expense for the stock plans, as reported in our consolidated statements of income, is as follows: Year Ended December 31 2018 2017 2016 (in millions of dollars) Performance Share Units $ 6.8 $ 11.5 $ 6.6 Restricted Stock Units 19.0 17.5 14.9 Other 0.5 0.5 0.4 Total Compensation Expense, Before Income Tax $ 26.3 $ 29.5 $ 21.9 Total Compensation Expense, Net of Income Tax $ 20.9 $ 19.5 $ 14.4 Cash received under all share-based payment arrangements for the years ended December 31, 2018 , 2017 , and 2016 was $4.6 million , $10.8 million , and $8.5 million , respectively.

Reinsurance

Reinsurance	12 Months Ended
	Dec. 31, 2018
Reinsurance Disclosures [Abstract]
Reinsurance	Reinsurance Thirteen major companies account for approximately 92 percent of our reinsurance recoverable at December 31, 2018 , and all are rated A or better by A.M. Best Company (AM Best) or are fully securitized by letters of credit or investment-grade fixed maturity securities held in trust. Approximately seven percent of our reinsurance recoverable relates to business reinsured either with companies rated A- or better by AM Best, with overseas entities with equivalent ratings or backed by letters of credit or trust agreements, or through reinsurance arrangements wherein we retain the assets in our general account. The remaining one percent of our reinsurance recoverable is held by companies either rated below A- by AM Best or not rated. Reinsurance data is as follows: Year Ended December 31 2018 2017 2016 (in millions of dollars) Direct Premium Income $ 9,171.1 $ 8,677.2 $ 8,385.0 Reinsurance Assumed 142.6 230.0 236.3 Reinsurance Ceded (327.6 ) (310.1 ) (263.6 ) Net Premium Income $ 8,986.1 $ 8,597.1 $ 8,357.7 Ceded Benefits and Change in Reserves for Future Benefits $ 667.2 $ 655.4 $ 648.3 Effective October 1, 2016, we entered into a reinsurance agreement under which we ceded 30 percent of the risk for certain blocks of Unum US individual disability policies, as well as some related claims development risk for a limited period of time. The agreement is on a non-proportional modified coinsurance basis with a provision for experience refunds.

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2018
Segment Reporting [Abstract]
Segment Information	We have three principal operating business segments: Unum US, Unum International, and Colonial Life. Our other segments are Closed Block and Corporate. The Unum US segment is comprised of group long-term disability, which includes our new medical stop-loss product, and short-term disability insurance, group life and accidental death and dismemberment products, and supplemental and voluntary lines of business. The supplemental and voluntary lines of business are comprised of individual disability, voluntary benefits, and dental and vision products. These products are marketed through our field sales personnel who work in conjunction with independent brokers and consultants. In connection with our acquisition of Pramerica Zycie TUiR S.A., (which we have subsequently renamed Unum Zycie TUiR S.A. and refer to as Unum Poland) in the fourth quarter of 2018, we changed the name of our Unum UK segment to Unum International. The Unum International segment is now comprised of our Unum UK line of business and the newly acquired Unum Poland line of business. See "Acquisitions of Business" below for further information. Unum UK's business includes insurance for group long-term disability, group life, and supplemental lines of business which include dental, individual disability, and critical illness products. Unum UK's products are sold primarily in the United Kingdom through field sales personnel and independent brokers and consultants. Unum Poland's business primarily includes insurance for individual and group life with accident and health riders. Unum Poland's products are sold only in Poland, primarily through a combination of independent agents and field sales personnel. Unum Poland 's results are included within the supplemental product of the Unum International segment in U.S. dollars. The Colonial Life segment includes insurance for accident, sickness, and disability products, which includes our expanded dental and vision products, life products, and cancer and critical illness products marketed to employees, on both a group and an individual basis, at the workplace through an independent contractor agency sales force and brokers. The Closed Block segment consists of individual disability, group and individual long-term care, and other insurance products no longer actively marketed. Individual disability in this segment generally consists of policies we sold prior to the mid-1990s and entirely discontinued selling in 2004, other than update features contractually allowable on existing policies. We discontinued offering individual long-term care in 2009 and group long-term care in 2012. Other insurance products include group pension, individual life and corporate-owned life insurance, reinsurance pools and management operations, and other miscellaneous product lines. The Corporate segment includes investment income on corporate assets not specifically allocated to a line of business, interest expense on corporate debt other than non-recourse debt, and certain other corporate income and expense not allocated to a line of business. Acquisitions of Business 2018 Acquisitions On November 1, 2018, we acquired 100 percent of the shares and voting interests in Jaimini Health, Inc. (Jaimini Health) , a dental health maintenance organization. The acquisition of Jaimini Health will broaden our employee benefit dental offerings in the U.S., particularly in the state of California, and is reported in our Unum US segment. On October 1, 2018, we acquired 100 percent of the shares and voting interests in Unum Poland , a financial protection benefits provider in Poland. This acquisition will expand our European presence, which we believe to be an attractive market for financial protection benefits. On January 1, 2018, we acquired 100 percent of the shares and voting interests in Leavelogic, Inc (Leavelogic) , a leave management technology provider. The acquisition of Leavelogic will enhance our current leave management offerings by providing tools for employers and employees to better manage the family leave process and is reported in our Unum US segment. Aggregate revenues for all three acquired entities totaled approximately $61 million in 2017. Aggregate assets were valued at approximately $344 million as of the respective acquisition dates and were primarily comprised of bonds, short-term investments, and intangible assets attributable to the value of business acquired, the value of distribution networks, and licenses. Aggregate liabilities were valued at approximately $206 million as of the respective acquisition dates and were primarily comprised of outstanding claim liabilities, reserves for future claims, and income tax liabilities. The aggregate purchase price for all three transactions was approximately $151 million and exceeded the fair value of the identifiable net assets by approximately $13 million , which was identified as goodwill, primarily attributable to the value of adding individual and group financial protection products in Poland to our current employee benefit offerings and the value of enhancing our technology capabilities around our leave management offerings. The goodwill is not deductible for income tax purposes except upon disposition of the acquired entities. These acquisitions, the results of which are included in our consolidated financial statements for the periods subsequent to the respective dates of acquisition, did not have a material impact on revenue or results of operations for 2018. 2016 Acquisition In 2016 , we acquired 100 percent of the shares and voting interests in H&J Capital, L.L.C., parent of Starmount Life Insurance Company and AlwaysCare Benefits (Starmount) , for a total cash purchase price of $140.3 million plus contingent cash consideration of $10.0 million that was paid in two increments of $5.0 million each, at 18 and 24 months from the date of acquisition upon satisfaction of certain conditions. Starmount Life Insurance Company is an independent provider of dental and vision insurance in the U.S. workplace, and AlwaysCare Benefits is a nationally licensed, third-party administrator. The acquisition of Starmount broadens our employee benefit offerings in the U.S. Starmount's dental and vision products and new dental and vision products marketed by Unum US are reported in our Unum US segment within our supplemental and voluntary product lines. Colonial Life dental and vision products were introduced in 2018 and are reported in our Colonial Life segment within our accident, sickness, and disability product line. Total assets were valued at $93.1 million as of the acquisition date and were primarily comprised of bonds, cash, accounts receivable, and intangible assets attributable to the value of business acquired and the value of existing state licenses. Total liabilities were valued at $55.7 million as of the acquisition date and were primarily comprised of outstanding claim liabilities and reserves for future claims. The total purchase price exceeded the fair value of the identifiable net assets by $111.2 million and has been identified as goodwill, primarily attributable to the value of adding dental and vision to our current employee benefit offerings. Goodwill was allocated to the reporting units expected to benefit from the acquisition. Approximately 75 percent was allocated to our Unum US supplemental and voluntary product lines and approximately 25 percent to Colonial Life. The goodwill is not deductible for income tax purposes except upon disposition of the acquired entity. Segment information is as follows: Year Ended December 31 2018 2017 2016 (in millions of dollars) Premium Income Unum US Group Disability Group Long-term Disability $ 1,766.2 $ 1,749.6 $ 1,726.6 Group Short-term Disability 706.3 639.8 626.1 Group Life and Accidental Death & Dismemberment Group Life 1,583.7 1,467.5 1,410.0 Accidental Death & Dismemberment 156.3 147.5 140.3 Supplemental and Voluntary Individual Disability 425.4 420.2 480.3 Voluntary Benefits 895.7 849.4 796.5 Dental and Vision 202.8 169.5 61.1 5,736.4 5,443.5 5,240.9 Unum International Group Long-term Disability 358.9 340.3 355.2 Group Life 110.8 103.1 105.7 Supplemental 99.1 69.6 68.4 568.8 513.0 529.3 Colonial Life Accident, Sickness, and Disability 929.3 884.2 830.0 Life 328.4 300.4 273.8 Cancer and Critical Illness 346.1 326.8 313.3 1,603.8 1,511.4 1,417.1 Closed Block Individual Disability 420.8 471.8 521.9 Long-term Care 648.3 648.7 643.9 All Other 8.0 8.7 4.6 1,077.1 1,129.2 1,170.4 Total Premium Income $ 8,986.1 $ 8,597.1 $ 8,357.7 Unum US Unum International Colonial Life Closed Block Corporate Total (in millions of dollars) Year Ended December 31, 2018 Premium Income $ 5,736.4 $ 568.8 $ 1,603.8 $ 1,077.1 $ — $ 8,986.1 Net Investment Income 778.7 117.2 151.2 1,377.1 29.5 2,453.7 Other Income 118.5 0.4 1.2 75.4 2.7 198.2 Adjusted Operating Revenue $ 6,633.6 $ 686.4 $ 1,756.2 $ 2,529.6 $ 32.2 $ 11,638.0 Adjusted Operating Income (Loss) $ 1,014.6 $ 113.9 $ 335.2 $ 125.5 $ (171.1 ) $ 1,418.1 Interest and Debt Expense $ — $ — $ — $ 6.9 $ 160.4 $ 167.3 Depreciation and Amortization $ 389.6 $ 17.6 $ 257.3 $ 8.3 $ 1.0 $ 673.8 Year Ended December 31, 2017 Premium Income $ 5,443.5 $ 513.0 $ 1,511.4 $ 1,129.2 $ — $ 8,597.1 Net Investment Income 811.2 120.2 144.9 1,354.0 21.4 2,451.7 Other Income 113.2 0.7 1.1 79.8 2.9 197.7 Adjusted Operating Revenue $ 6,367.9 $ 633.9 $ 1,657.4 $ 2,563.0 $ 24.3 $ 11,246.5 Adjusted Operating Income (Loss) $ 1,009.5 $ 111.7 $ 325.0 $ 123.9 $ (146.8 ) $ 1,423.3 Interest and Debt Expense $ — $ — $ — $ 6.7 $ 153.2 $ 159.9 Depreciation and Amortization $ 371.3 $ 17.3 $ 239.9 $ 6.7 $ 0.9 $ 636.1 Year Ended December 31, 2016 Premium Income $ 5,240.9 $ 529.3 $ 1,417.1 $ 1,170.4 $ — $ 8,357.7 Net Investment Income 828.7 118.1 141.5 1,352.2 18.5 2,459.0 Other Income 113.3 0.2 1.2 86.0 4.9 205.6 Adjusted Operating Revenue $ 6,182.9 $ 647.6 $ 1,559.8 $ 2,608.6 $ 23.4 $ 11,022.3 Adjusted Operating Income (Loss) $ 914.2 $ 128.6 $ 314.2 $ 129.5 $ (163.0 ) $ 1,323.5 Interest and Debt Expense $ — $ — $ — $ 6.9 $ 159.1 $ 166.0 Depreciation and Amortization $ 353.0 $ 16.4 $ 222.9 $ 6.9 $ 1.0 $ 600.2 Unum Colonial Unum US International Life Total (in millions of dollars) Deferred Acquisition Costs Year Ended December 31, 2018 Beginning of Year $ 1,205.4 $ 21.3 $ 957.9 $ 2,184.6 Capitalization 344.0 8.1 315.9 668.0 Amortization (315.1 ) (8.2 ) (242.2 ) (565.5 ) Adjustment Related to Unrealized Investment Gains and Losses 5.1 — 18.4 23.5 Foreign Currency — (1.2 ) — (1.2 ) End of Year $ 1,239.4 $ 20.0 $ 1,050.0 $ 2,309.4 Year Ended December 31, 2017 Beginning of Year $ 1,176.5 $ 21.4 $ 896.3 $ 2,094.2 Capitalization 325.5 7.0 295.5 628.0 Amortization (293.6 ) (9.1 ) (224.4 ) (527.1 ) Adjustment Related to Unrealized Investment Gains and Losses (3.0 ) — (9.5 ) (12.5 ) Foreign Currency — 2.0 — 2.0 End of Year $ 1,205.4 $ 21.3 $ 957.9 $ 2,184.6 Year Ended December 31, 2016 Beginning of Year $ 1,136.4 $ 27.1 $ 845.0 $ 2,008.5 Capitalization 314.1 8.2 270.1 592.4 Amortization (275.2 ) (9.7 ) (208.1 ) (493.0 ) Adjustment Related to Unrealized Investment Gains and Losses 1.2 — (10.7 ) (9.5 ) Foreign Currency — (4.2 ) — (4.2 ) End of Year $ 1,176.5 $ 21.4 $ 896.3 $ 2,094.2 December 31 2018 2017 (in millions of dollars) Assets Unum US $ 17,510.9 $ 18,109.1 Unum International 3,426.8 3,428.1 Colonial Life 4,237.9 4,184.1 Closed Block 34,527.6 35,051.2 Corporate 2,172.4 3,240.6 Total Assets $ 61,875.6 $ 64,013.1 Revenue is primarily derived from sources in the United States and the United Kingdom. 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, 2018 and 2017 goodwill was $350.3 million and $338.6 million , respectively, with $280.0 million and $271.1 million , respectively, attributable to Unum US, $42.6 million and $39.8 million , respectively, attributable to Unum International, and $27.7 million attributable to Colonial Life in each year. Stockholders' equity is allocated to the operating segments on the basis of an internal allocation formula that reflects the volume and risk components of each operating segment's business and aligns allocated equity with our target capital levels for regulatory and rating agency purposes. We modify this formula periodically to recognize changes in the views of capital requirements. We measure and analyze our segment performance on the basis of "adjusted operating revenue" and "adjusted operating income" or "adjusted operating loss", which differ from total revenue and income before income tax as presented in our consolidated statements of income due to the exclusion of net realized investment gains and losses and certain other items specified in the reconciliations below. We believe adjusted operating revenue and adjusted operating income or loss are better performance measures and better indicators of the revenue and profitability and underlying trends in our business. These performance measures are in accordance with GAAP guidance for segment reporting, but they should not be viewed as a substitute for total revenue, income before income tax, or net income. Realized investment gains or losses depend on market conditions and do not necessarily relate to decisions regarding the underlying business of our segments. Our investment focus is on investment income to support our insurance liabilities as opposed to the generation of realized investment gains or losses. Although we may experience realized investment gains or losses which will affect future earnings levels, a long-term focus is necessary to maintain profitability over the life of the business since our underlying business is long-term in nature, and we need to earn the interest rates assumed in calculating our liabilities. 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 "Executive Summary" contained herein in Item 7 and Notes 6, 7, and 14 of the "Notes to Consolidated Financial Statements" contained herein in Item 8 for further discussion regarding the impacts of the long-term care reserve increase, the TCJA, the unclaimed death benefit reserve increase, and the loss from a guaranty fund assessment, respectively. 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 2018 2017 2016 (in millions of dollars) Total Revenue $ 11,598.5 $ 11,286.8 $ 11,046.5 Excluding: Net Realized Investment Gain (Loss) (39.5 ) 40.3 24.2 Adjusted Operating Revenue $ 11,638.0 $ 11,246.5 $ 11,022.3 Income Before Income Tax $ 627.8 $ 1,404.0 $ 1,347.7 Excluding: Net Realized Investment Gain (Loss) (39.5 ) 40.3 24.2 Loss from Guaranty Fund Assessment — (20.6 ) — Unclaimed Death Benefit Reserve Increase — (39.0 ) — Long-term Care Reserve Increase (750.8 ) — — Adjusted Operating Income $ 1,418.1 $ 1,423.3 $ 1,323.5

Commitments and Contingent Liab

Commitments and Contingent Liabilities	12 Months Ended
	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies Disclosure	Commitments We have noncancelable lease obligations on certain office space and equipment. As of December 31, 2018 , the aggregate net minimum lease payments were $157.7 million payable as follows: $30.4 million in 2019 , $26.3 million in 2020 , $22.2 million in 2021 , $18.2 million in 2022 , $12.3 million in 2023 , and $48.3 million thereafter. Rental expense for the years ended December 31, 2018 , 2017 and 2016 was $64.3 million , $54.2 million , and $51.4 million , respectively. At December 31, 2018 , we had unfunded commitments of $515.6 million for certain of our investments, the amount of which may or may not be funded. Contingent Liabilities We are a defendant in a number of litigation matters that have arisen in the normal course of business. Further, state insurance regulatory authorities and other federal and state authorities regularly make inquiries and conduct investigations concerning our compliance with applicable insurance and other laws and regulations. Given the complexity and scope of our litigation and regulatory matters, it is not possible to predict the ultimate outcome of all pending investigations or legal proceedings or provide reasonable estimates of potential losses, except if noted in connection with specific matters. In some of these matters, no specified amount is sought. In others, very large or indeterminate amounts, including punitive and treble damages, are asserted. There is a wide variation of pleading practice permitted in the United States courts with respect to requests for monetary damages, including some courts in which no specified amount is required and others which allow the plaintiff to state only that the amount sought is sufficient to invoke the jurisdiction of that court. Further, some jurisdictions permit plaintiffs to allege damages well in excess of reasonably possible verdicts. Based on our extensive experience and that of others in the industry with respect to litigating or resolving claims through settlement over an extended period of time, we believe that the monetary damages asserted in a lawsuit or claim bear little relation to the merits of the case, or the likely disposition value. Therefore, the specific monetary relief sought is not stated. Unless indicated otherwise in the descriptions below, reserves have not been established for litigation and contingencies. An estimated loss is accrued when it is both probable that a liability has been incurred and the amount of the loss can be reasonably estimated. Claims Handling Matters We and our insurance subsidiaries, in the ordinary course of our business, are engaged in claim litigation where disputes arise as a result of a denial or termination of benefits. Most typically these lawsuits are filed on behalf of a single claimant or policyholder, and in some of these individual actions punitive damages are sought, such as claims alleging bad faith in the handling of insurance claims. For our general claim litigation, we maintain reserves based on experience to satisfy judgments and settlements in the normal course. We expect that the ultimate liability, if any, with respect to general claim litigation, after consideration of the reserves maintained, will not be material to our consolidated financial condition. Nevertheless, given the inherent unpredictability of litigation, it is possible that an adverse outcome in certain claim litigation involving punitive damages could, from time to time, have a material adverse effect on our consolidated results of operations in a period, depending on the results of operations for the particular period. From time to time class action allegations are pursued where the claimant or policyholder purports to represent a larger number of individuals who are similarly situated. Since each insurance claim is evaluated based on its own merits, there is rarely a single act or series of actions which can properly be addressed by a class action. Nevertheless, we monitor these cases closely and defend ourselves appropriately where these allegations are made. Miscellaneous Matters Similar to other insurers, we were the subject of an examination by a third party acting on behalf of a number of state treasurers concerning our compliance with the unclaimed property laws of the participating states. We cooperated fully with this examination and in the fourth quarter of 2017 , we started the process to reach a Global Resolution Agreement with the third party regarding settlement of the examination, which we finalized in January of 2018 . Under the terms of the agreement, the third party acting on behalf of the signatory states compared insured data to the Social Security Administration's Death Master File (SSDMF) to identify deceased insureds and contract holders where a valid claim has not been made. During the fourth quarter of 2017 , we established reserves which reflect our estimate of the liability expected to be paid as we execute on the terms of the settlement. We also are cooperating with a Delaware Market Conduct examination involving the same issue, which is currently inactive. The legal and regulatory environment around unclaimed death benefits continues to evolve. It is possible that the current settlement and/or similar investigations by other state jurisdictions may result in payments to beneficiaries, the payment of abandoned funds under state law, and/or administrative penalties, the total of which may be in excess of the reserves established. In 2009, a Pennsylvania-based insurance company and its affiliates were ordered into rehabilitation, and the Pennsylvania Insurance Commissioner, who was appointed as the Rehabilitator, filed petitions for liquidation with the Commonwealth Court of Pennsylvania. Under Pennsylvania law, payment of covered claims and other related insurance obligations are provided, within prescribed limits, by state guaranty associations. These guaranty associations assess fees to meet these obligations on insurance companies that sell insurance within the state, which are generally based on a company's pro rata portion of average premiums written or received for several years prior to the insolvency. In March 2017 , a formal order of liquidation was issued, and as such, we were subject to an assessment by those guaranty associations that are responsible for policyholder claims, and accordingly accrued, in the first quarter of 2017 , an estimated loss contingency. We continue to submit payment to satisfy this assessment as requests for payment are received from the guaranty associations. Securities Class Actions: Three alleged securities class action lawsuits have been filed against Unum Group and individual defendants as follows: • On June 13, 2018, an alleged securities class action lawsuit entitled Cynthia Pittman v. Unum Group, Richard McKenney, John McGarry, and Daniel Waxenberg was filed in the United States District Court for the Eastern District of Tennessee. The plaintiff seeks to represent purchasers of Unum Group publicly traded securities between January 31, 2018 and May 2, 2018. The plaintiff alleges the Company caused its shares to trade at artificially high levels by failing to disclose information about the rate of long-term care policy terminations and long-term care claim incidence resulting in misleading statements about capital management plans and long-term care reserves. The complaint asserts claims under Sections 10(b) and 20(a) of the Securities Exchange Act of 1934 and Rule 10b-5 thereunder and seeks compensatory damages in an amount to be proven at trial. The Company strongly denies these allegations and will vigorously defend the litigation. • On July 13, 2018, an alleged securities class action lawsuit entitled Scott Cunningham v. Unum Group, Richard McKenney, John McGarry, and Daniel Waxenberg was filed in the United States District Court for the Eastern District of Tennessee. The allegations, class period, and damages claimed mirror those in the Pittman matter. The Company strongly denies these allegations and will vigorously defend the litigation. • On July 25, 2018, an alleged securities class action lawsuit entitled City of Taylor Police and Fire Retirement System v. Unum Group, Richard McKenney, John McGarry, Steve Zabel, and Daniel Waxenberg was filed in the United States District Court for the Eastern District of Tennessee. The plaintiff seeks to represent purchasers of Unum Group publicly traded securities between October 27, 2016 and May 1, 2018. The allegations and damages claimed mirror those in the Pittman matter. The Company strongly denies these allegations and will vigorously defend the litigation. On November 9, 2018, the court consolidated the Pittman , Cunningham , and City of Taylor Police and Fire Retirement System cases into one matter entitled In re Unum Group Securities Litigation , appointed a lead plaintiff and lead plaintiff’s counsel, and directed the plaintiff to file a consolidated amended complaint. On January 15, 2019, the plaintiff filed a consolidated amended complaint asserting claims under Sections 10(b) and 20(a) of the Securities Exchange Act of 1934 and Rule 10b-5 thereunder and seeks compensatory damages in an amount to be proven at trial as well as costs, expenses, and attorney’s fees. The Company strongly denies these allegations and will vigorously defend the litigation. These lawsuits are in a very preliminary stage, the outcome is uncertain, and the Company is unable to estimate a range of reasonably possible losses. Reserves have not been established for these matters. Although we believe these claims lack merit, an adverse outcome in one or more of these actions could, depending on the nature, scope, and amount of the ruling, materially adversely affect our consolidated results of operations in a period. Shareholder Derivative Actions: Three alleged derivative lawsuits have been filed against individual defendants and Unum Group, as nominal defendant, as follows: • On September 27, 2018, a purported shareholder derivative lawsuit entitled Vladimir Gusinsky Revocable Trust, Derivatively on Behalf of Unum Group v. Richard P. McKenney, John F. McGarry, Daniel J. Waxenberg, Steve Zabel, Kevin T. Kabat, E. Michael Caulfield, Gloria C. Larson, Timothy F. Keaney, Theodore H. Bunting, Jr., Cynthia L. Egan, Ronald P. O'Hanley, Francis L. Shammo, Joseph J. Echevarria, Thomas R. Watjen, Pamela H. Godwin, Edward J. Muhl, and Unum Group as nominal defendant was filed in the United States District Court for the District of Delaware. The complaint purports to assert claims on behalf of the Company against certain current and past members of our Board of Directors and Mr. McKenney for alleged misleading statements about the Company's long-term care business in the Company's proxy statement filed with the Securities and Exchange Commission on April 13, 2017 in violation of Section 14(a) of the Securities Exchange Act of 1934. The complaint also purports to assert claims on behalf of the Company against all individual defendants arising out of the Company's long-term care business for breach of fiduciary duties, waste of corporate assets and unjust enrichment. The complaint seeks compensatory damages in an amount to be proven at trial, changes to corporate governance and internal procedures, equitable and injunctive relief, restitution, costs, expenses, and attorney's fees. The Company strongly denies these allegations and will vigorously defend the litigation. • On October 23, 2018, a purported shareholder derivative lawsuit entitled Steven Jenkins, Derivatively on Behalf of Unum Group v. Richard P. McKenney, John F. McGarry, Daniel J. Waxenberg, Steve Zabel, Kevin T. Kabat, E. Michael Caulfield, Gloria C. Larson, Timothy F. Keaney, Theodore H. Bunting, Jr., Cynthia L. Egan, Ronald P. O'Hanley, Francis J. Shammo, Joseph J. Echevarria, Thomas R. Watjen, Pamela H. Godwin, Edward J. Muhl, and Unum Group as nominal defendant was filed in the United States District Court for the District of Delaware. The defendants, allegations, and damages claimed mirror those in the Gusinsky matter. The Company strongly denies these allegations and will vigorously defend the litigation. • On November 1, 2018, a purported shareholder derivative lawsuit entitled Julie Nguyen, Derivatively on Behalf of Unum Group v. Richard P. McKenney, John F. McGarry, Daniel J. Waxenberg, Steve Zabel, Kevin T. Kabat, E. Michael Caulfield, Gloria C. Larson, Timothy F. Keaney, Theodore H. Bunting, Jr., Cynthia L. Egan, Ronald P. O'Hanley, Francis J. Shammo, Joseph J. Echevarria, Thomas R. Watjen, Pamela H. Godwin, Edward J. Muhl, and Unum Group as nominal defendant was filed in the United States District Court for the District of Delaware. The defendants, allegations, and damages claimed mirror those in the Gusinsky matter. The Company strongly denies these allegations and will vigorously defend the litigation. On December 10, 2018, the court consolidated the Gusinsky , Jenkins , and Nguyen cases into one matter entitled In re Unum Group Stockholder Derivative Litigation , appointed co-lead counsel and liaison counsel for plaintiffs and directed the parties to propose a schedule of proceedings for the consolidated matter. These lawsuits are in a very preliminary stage, the outcome is uncertain, and the Company is unable to estimate a range of reasonably possible losses. Reserves have not been established for these matters. Although we believe these claims lack merit, an adverse outcome in one or more of these actions could, depending on the nature, scope, and amount of the ruling, materially adversely affect our consolidated results of operations in a period.

Statutory Financial Information

Statutory Financial Information	12 Months Ended
	Dec. 31, 2018
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. Our 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. Certain of our traditional U.S. life insurance subsidiaries cede blocks of business to Northwind Re and Fairwind Insurance Company (Fairwind), both of which are affiliated captive reinsurance subsidiaries (captive reinsurers) domiciled in the United States, with Unum Group as the ultimate parent. These captive reinsurers were established for the limited purpose of reinsuring risks attributable to specified policies issued or reinsured by our life insurance subsidiaries. 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 allows for 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 $137 million and $142 million as of December 31, 2018 and 2017 respectively. Included in the 2018 results for Fairwind was the assumed portion of the statutory impact of the long-term care reserve increase from Unum America. Included in the 2017 results for Fairwind was the revaluation of the deferred tax asset at the new corporate rate of 21 percent resulting from the enactment of TCJA. Northwind Re has no material state prescribed accounting practices that differ from statutory accounting principles prescribed by the NAIC. 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 2018 2017 2016 (in millions of dollars) Combined Net Income (Loss) Traditional U.S. Life Insurance Subsidiaries $ 953.0 $ 807.4 $ 855.1 Captive Reinsurers $ (109.6 ) $ (137.1 ) $ 48.4 Combined Net Gain (Loss) from Operations Traditional U.S. Life Insurance Subsidiaries $ 959.8 $ 812.4 $ 884.6 Captive Reinsurers $ (110.9 ) $ (143.1 ) $ 50.6 December 31 2018 2017 (in millions of dollars) Combined Capital and Surplus Traditional U.S. Life Insurance Subsidiaries $ 3,572.7 $ 3,448.3 Captive Reinsurers $ 1,766.2 $ 1,606.9 Solvency II, a European Union directive prescribes capital requirements and risk management standards for the European insurance industry. As derived from the most recent annual financial statements based on Solvency II requirements, regulatory net income and own funds available of our United Kingdom insurance subsidiary, Unum Limited, were £78.7 million and £672.3 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 impacts of the TCJA, particularly the decrease in the U.S. corporate tax rate, resulted in both the reduction of our admitted deferred tax assets and the increase of RBC factors adopted by the NAIC, which has reduced our RBC ratios; however, the total adjusted capital of each of our U.S. insurance subsidiaries at December 31, 2018 is in excess of those RBC levels. Restrictions under applicable state insurance laws limit the amount of dividends that can be paid to a parent company from its insurance subsidiaries in any 12-month period without prior approval by regulatory authorities. For life insurance companies domiciled in the U.S., that limitation generally equals, depending on the state of domicile, either ten percent of an insurer's statutory surplus with respect to policyholders as of the preceding year end or the statutory net gain from operations, excluding realized investment gains and losses, of the preceding year. The payment of dividends to a parent company from a life insurance subsidiary is generally further limited to the amount of unassigned funds. Based on the restrictions under current law, $994.9 million is available, without prior approval by regulatory authorities, during 2019 for the payment of dividends to Unum Group from its traditional U.S. life insurance subsidiaries. The ability of our captive insurers to pay dividends to their respective parent companies will depend on their satisfaction of applicable regulatory requirements and on the performance of the business reinsured. We also have the ability to receive dividends from our foreign subsidiaries, primarily in the U.K., for which the payment may be subject to applicable insurance company regulations and capital guidance. We have £140.0 million available for the payment of dividends from Unum Limited during 2019 , subject to regulatory approval. Deposits Our U.S. insurance subsidiaries had on deposit with U.S. regulatory authorities securities with a book value of $155.7 million at both December 31, 2018 and 2017 , held for the protection of policyholders.

Unaudited Quarterly Results

Unaudited Quarterly Results	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information	The following is a summary of our unaudited quarterly results of operations for 2018 and 2017 : 2018 4 th 3 rd 2 nd 1 st (in millions of dollars, except share data) Premium Income $ 2,263.3 $ 2,251.8 $ 2,221.0 $ 2,250.0 Net Investment Income 608.6 619.2 623.6 602.3 Net Realized Investment Gain (Loss) (41.4 ) 6.7 (2.6 ) (2.2 ) Total Revenue 2,880.8 2,927.8 2,890.3 2,899.6 Income (Loss) Before Income Tax 309.7 (377.8 ) 354.8 341.1 Net Income (Loss) 249.1 (284.7 ) 285.5 273.5 Net Income (Loss) Per Common Share Basic 1.15 (1.30 ) 1.29 1.23 Assuming Dilution 1.15 (1.30 ) 1.29 1.23 2017 4 th 3 rd 2 nd 1 st (in millions of dollars, except share data) Premium Income $ 2,158.4 $ 2,153.6 $ 2,142.2 $ 2,142.9 Net Investment Income 619.8 609.0 620.5 602.4 Net Realized Investment Gain 11.4 9.8 8.1 11.0 Total Revenue 2,839.2 2,819.1 2,822.0 2,806.5 Income Before Income Tax 345.3 366.8 361.6 330.3 Net Income 266.9 252.3 245.1 229.9 Net Income Per Common Share Basic 1.19 1.12 1.08 1.00 Assuming Dilution 1.19 1.12 1.07 1.00 Items affecting the comparability of our financial results are as follows: • Third quarter of 2018 reserve increase of $750.8 million before tax and $593.1 million after tax related to long-term care. • Fourth quarter of 2017 reserve increase of $39.0 million before tax and $25.4 million after tax related to unclaimed death benefits. • Fourth quarter of 2017 net tax benefit of $31.5 million related to the TCJA. • First quarter of 2017 loss from a guaranty fund assessment related to an unaffiliated insurer that was declared insolvent of $20.6 million before tax and $13.4 million after tax. See Notes 6, 7, and 14 for further discussion of the above items.

Schedule I - Summary of Investm

Schedule I - Summary of Investments, Other Than Investments in Related Parties Schedule I - Summary of Investments, Other Than Investments in Related Parties	12 Months Ended
	Dec. 31, 2018
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, 2018 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 $ 1,702.1 $ 1,814.4 $ 1,814.4 States, Municipalities, and Political Subdivisions 2,121.5 2,424.2 2,424.2 Foreign Governments 825.8 983.7 983.7 Public Utilities 6,626.2 7,412.8 7,412.8 Mortgage/Asset-Backed Securities 1,523.8 1,582.7 1,582.7 All Other Corporate Bonds 27,436.8 28,754.0 28,754.0 Redeemable Preferred Stocks 39.0 39.9 39.9 Total Fixed Maturity Securities 40,275.2 $ 43,011.7 43,011.7 Mortgage Loans 2,295.0 2,295.0 Policy Loans 3,729.9 3,729.9 Other Long-term Investments Derivatives — 30.9 (2) Equity Securities 32.6 29.2 Miscellaneous Long-term Investments 613.4 642.8 (3) Short-term Investments 968.1 968.1 Total Investments $ 47,914.2 $ 50,707.6 (1) The amortized cost for fixed maturity securities and mortgage loans represents original cost reduced by repayments, write-downs from other-than-temporary declines in fair value, amortization of premiums, and/or accretion of discounts. (2) Derivatives are carried at fair value. (3) The difference between amortized cost and carrying value primarily results from changes in the partnership owner's equity since acquisition.

Schedule II Condensed Finacial

Schedule II Condensed Finacial Information of Registrant	12 Months Ended
	Dec. 31, 2018
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 2018 2017 (in millions of dollars) Assets Fixed Maturity Securities - at fair value (amortized cost: $139.0; $153.9) $ 135.9 $ 154.1 Other Long-term Investments 38.8 16.8 Short-term Investments 285.2 477.8 Investment in Subsidiaries 11,383.6 12,157.1 Deferred Income Tax 116.7 121.5 Other Assets 446.9 455.4 Total Assets $ 12,407.1 $ 13,382.7 Liabilities and Stockholders' Equity Liabilities Short-term Debt $ — $ 199.9 Long-term Debt 2,831.3 2,538.4 Pension and Postretirement Benefits 594.2 683.3 Other Liabilities 359.8 386.2 Total Liabilities 3,785.3 3,807.8 Stockholders' Equity Common Stock 30.5 30.5 Additional Paid-in Capital 2,321.7 2,303.3 Accumulated Other Comprehensive Income (Loss) (814.2 ) 127.5 Retained Earnings 9,863.1 9,542.2 Treasury Stock (2,779.3 ) (2,428.6 ) Total Stockholders' Equity 8,621.8 9,574.9 Total Liabilities and Stockholders' Equity $ 12,407.1 $ 13,382.7 See notes to condensed financial information. SCHEDULE II--CONDENSED FINANCIAL INFORMATION OF REGISTRANT (Continued) Unum Group (Parent Company) STATEMENTS OF OPERATIONS Year Ended December 31 2018 2017 2016 (in millions of dollars) Cash Dividends from Subsidiaries $ 1,135.4 $ 830.2 $ 676.5 Other Income 66.6 66.6 58.4 Total Revenue 1,202.0 896.8 734.9 Interest and Debt Expense 161.4 154.2 160.1 Other Expenses 53.4 37.1 32.3 Total Expenses 214.8 191.3 192.4 Income of Parent Company Before Income Tax 987.2 705.5 542.5 Income Tax Expense (Benefit) (1.7 ) 115.3 (20.2 ) Income of Parent Company 988.9 590.2 562.7 Equity in Undistributed Earnings (Loss) of Subsidiaries (465.5 ) 404.0 368.7 Net Income 523.4 994.2 931.4 Other Comprehensive Income (Loss), Net of Tax (924.2 ) 178.5 (67.1 ) Comprehensive Income (Loss) $ (400.8 ) $ 1,172.7 $ 864.3 See notes to condensed financial information. SCHEDULE II--CONDENSED FINANCIAL INFORMATION OF REGISTRANT (Continued) Unum Group (Parent Company) STATEMENTS OF CASH FLOWS Year Ended December 31 2018 2017 2016 (in millions of dollars) Cash Provided by Operating Activities $ 1,052.1 $ 740.6 $ 685.4 Cash Flows from Investing Activities Proceeds from Sales of Fixed Maturity Securities — — 2.6 Proceeds from Maturities of Fixed Maturity Securities 52.5 194.3 111.2 Proceeds from Sales and Maturities of Other Investments — 35.2 0.4 Purchase of Fixed Maturity Securities (47.9 ) (121.2 ) (56.5 ) Purchase of Other Investments (22.3 ) — (23.3 ) Net Sales (Purchases) of Short-term Investments 192.6 (99.9 ) (89.8 ) Cash Distributions to Subsidiaries (530.8 ) (79.5 ) (143.6 ) Net Purchases of Property and Equipment (73.2 ) (83.3 ) (55.5 ) Acquisition of Business (146.1 ) — (140.3 ) Other, Net — — 0.2 Cash Used by Investing Activities (575.2 ) (154.4 ) (394.6 ) Cash Flows from Financing Activities Short-term Debt Repayment (200.0 ) — — Issuance of Long-term Debt 290.7 — 609.1 Long-term Debt Repayment — — (350.0 ) Issuance of Common Stock 4.6 10.8 8.5 Repurchase of Common Stock (356.2 ) (401.8 ) (405.2 ) Dividends Paid to Stockholders (215.6 ) (196.0 ) (182.6 ) Other, Net (9.3 ) 0.2 (1.0 ) Cash Used by Financing Activities (485.8 ) (586.8 ) (321.2 ) Decrease in Cash $ (8.9 ) $ (0.6 ) $ (30.4 ) See notes to condensed financial information. SCHEDULE II--CONDENSED FINANCIAL INFORMATION OF REGISTRANT (Continued) Unum Group (Parent Company) NOTES TO CONDENSED FINANCIAL INFORMATION Note 1 - Basis of Presentation The accompanying condensed financial statements should be read in conjunction with the consolidated financial statements and notes thereto of Unum Group and subsidiaries. Note 2 - Debt Debt consists of the following: December 31 2018 2017 Interest Rates Maturities (in millions of dollars) Long-term Debt Outstanding Principal Senior Notes issued 1998 6.750 - 7.250% 2028 $ 365.8 $ 365.8 Senior Notes issued 2002 7.375% 2032 39.5 39.5 Senior Notes issued 2010 5.625% 2020 400.0 400.0 Senior Notes issued 2012 and 2016 5.750% 2042 500.0 500.0 Senior Notes issued 2014 4.000% 2024 350.0 350.0 Senior Notes issued 2015 3.875% 2025 275.0 275.0 Senior Notes issued 2016 3.000% 2021 350.0 350.0 Medium-term Notes issued 1990 - 1996 7.000 - 7.190% 2023 - 2028 50.8 50.8 Junior Subordinated Debt Securities issued 1998 7.405% 2038 226.5 226.5 Junior Subordinated Debt Securities issued 2018 6.250% 2058 300.0 — Fair Value Hedge Adjustment (5.1 ) (4.5 ) Less: Unamortized Net Premium 9.6 9.7 Unamortized Debt Issuance Costs (30.8 ) (24.4 ) Total Long-term Debt 2,831.3 2,538.4 Short-term Debt Outstanding Principal Senior Notes issued 1998 7.000% 2018 — 200.0 Less Unamortized Debt Issuance Costs — (0.1 ) Total Short-term Debt — 199.9 Total Debt $ 2,831.3 $ 2,738.3 The medium-term notes are non-callable. The junior subordinated debt securities are callable under limited, specified circumstances. The remaining debt is callable and may be redeemed, in whole or in part, at any time. The aggregate contractual principal maturities are $400.0 million in 2020, $350.0 million in 2021, $2.0 million in 2023, and $2,105.6 million thereafter. SCHEDULE II--CONDENSED FINANCIAL INFORMATION OF REGISTRANT (Continued) Unum Group (Parent Company) NOTES TO CONDENSED FINANCIAL INFORMATION - CONTINUED Unsecured Notes In July 2018, our $200.0 million 7.00% senior unsecured notes matured. In September 2016, our $350.0 million 7.125% senior unsecured notes matured. In May 2016, we issued a total of $600.0 million aggregate principal amount of senior notes: (i) $350.0 million aggregate principal amount of senior notes due in 2021 with an annual coupon rate of 3.00% , and (ii) $250.0 million aggregate principal amount of senior notes due in 2042 with an annual coupon rate of 5.75% , pursuant to a reopening of the $250.0 million aggregate principal amount outstanding of our 5.75% senior notes due 2042 issued in 2012. Both issuances are callable at or above par and rank equally in the right of payment with all of our other unsecured and unsubordinated debt. Fair Value Hedges As of December 31, 2018 and 2017 , we had $250.0 million notional amount of an interest rate swap which effectively converts certain of our unsecured senior notes into floating rate debt. Under this agreement, we receive a fixed rate of interest and pay a variable rate of interest, based off of the three-month LIBOR. Junior Subordinated Debt Securities In May 2018, we issued $300.0 million of 6.25% junior subordinated notes due 2058. The notes are redeemable at or above par on or after June 15, 2023 and rank equally in the right of payment with our other junior subordinated debt securities. In 1998, Provident Financing Trust I (the trust), a 100 percent-owned finance subsidiary of Unum Group, issued $300.0 million of 7.405% capital securities 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. Unum Group issued 7.405% junior subordinated deferrable interest debentures to the trust in connection with the capital securities offering. The debentures mature in 2038. The sole assets of the trust are the junior subordinated debt securities. Interest Paid Interest paid on debt and related securities during 2018 , 2017 , and 2016 was $161.4 million , $148.7 million , and $147.8 million , respectively. Credit Facility In 2016, we amended the terms of our five-year, $400.0 million unsecured revolving credit facility, which was previously set to expire in 2018, to extend through March 2021. Under the terms of the agreement, we may request that the credit facility be increased up to $600.0 million . Borrowings under the credit facility are for general corporate uses and are subject to financial covenants, negative covenants, and events of default that are customary. The credit facility provides for borrowing at an interest rate based either on the prime rate or LIBOR. In addition, the credit facility provides for the issuance of letters of credit subject to certain terms and limitations. At December 31, 2018 and 2017 , letters of credit totaling $2.1 million had been issued from the credit facility, but there were no borrowed amounts outstanding.

Schedule III Supplementary Insu

Schedule III Supplementary Insurance Information	12 Months Ended
	Dec. 31, 2018
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Abstract]
Supplementary Insurance Information, for Insurance Companies Disclosure	SCHEDULE III--SUPPLEMENTARY INSURANCE INFORMATION Unum Group and Subsidiaries Segment Deferred Acquisition Costs Reserves for Future Policy Contract Benefits Unearned Premiums Policy and Contract Benefits (in millions of dollars) December 31, 2018 Unum US $ 1,239.4 $ 10,840.9 $ 47.2 $ 1,091.5 Unum International 20.0 2,340.5 123.3 115.6 Colonial Life 1,050.0 2,330.2 36.3 206.2 Closed Block — 29,330.3 156.5 282.4 Total $ 2,309.4 $ 44,841.9 $ 363.3 $ 1,695.7 December 31, 2017 Unum US $ 1,205.4 $ 11,382.1 $ 49.0 $ 1,059.8 Unum International 21.3 2,361.6 125.7 108.5 Colonial Life 957.9 2,224.2 34.7 212.1 Closed Block — 29,633.7 163.7 224.8 Total $ 2,184.6 $ 45,601.6 $ 373.1 $ 1,605.2 SCHEDULE III--SUPPLEMENTARY INSURANCE INFORMATION Unum Group and Subsidiaries (continued from preceding page) Segment Premium Income Net Investment Income (1) Benefits and Change in Reserves for Future Benefits (2) Amortization of Deferred Acquisition Costs All Other Expenses (3) Premiums Written (4) (in millions of dollars) December 31, 2018 Unum US $ 5,736.4 $ 778.7 $ 3,856.5 $ 315.1 $ 1,447.4 $ 3,873.0 Unum International 568.8 117.2 419.8 8.2 144.5 455.5 Colonial Life 1,603.8 151.2 824.9 242.2 353.9 1,277.3 Closed Block 1,077.1 1,377.1 2,919.2 — 235.7 1,065.7 Corporate — 29.5 — — 203.3 — Total $ 8,986.1 $ 2,453.7 $ 8,020.4 $ 565.5 $ 2,384.8 December 31, 2017 Unum US $ 5,443.5 $ 811.2 $ 3,693.4 $ 293.6 $ 1,398.0 $ 3,701.3 Unum International 513.0 120.2 381.9 9.1 131.2 404.2 Colonial Life 1,511.4 144.9 788.6 224.4 331.8 1,210.6 Closed Block 1,129.2 1,354.0 2,191.8 — 247.3 1,109.8 Corporate — 21.4 — — 191.7 — Total $ 8,597.1 $ 2,451.7 $ 7,055.7 $ 527.1 $ 2,300.0 December 31, 2016 Unum US $ 5,240.9 $ 828.7 $ 3,624.3 $ 275.2 $ 1,369.2 $ 3,564.4 Unum International 529.3 118.1 367.4 9.7 141.9 435.4 Colonial Life 1,417.1 141.5 726.4 208.1 311.1 1,145.0 Closed Block 1,170.4 1,352.2 2,223.7 — 255.4 1,161.8 Corporate — 18.5 — — 186.4 — Total $ 8,357.7 $ 2,459.0 $ 6,941.8 $ 493.0 $ 2,264.0 (1) Net investment income is allocated based upon segmentation. Each segment has its own specifically identified assets and receives the investment income generated by those assets. (2) Included in 2018 is a reserve charge of $750.8 million in the Closed Block segment related to our long-term care business. Included in 2017 are unclaimed death benefits reserve increases of $26.6 million in Unum US and $12.4 million in Colonial Life. (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. Included in 2017 is a loss contingency accrual for a guaranty fund assessment of $20.6 million in Corporate. (4) Excludes life insurance.

Schedule IV Reinsurance

Schedule IV Reinsurance	12 Months Ended
	Dec. 31, 2018
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, 2018 Life Insurance in Force $ 937,300.8 $ 40,902.8 $ 1,089.3 $ 897,487.3 0.1 % Premium Income: Life Insurance $ 2,442.1 $ 138.2 $ 8.7 $ 2,312.6 0.4 % Accident, Health, and Other Insurance 6,729.0 189.4 133.9 6,673.5 2.0 % Total $ 9,171.1 $ 327.6 $ 142.6 $ 8,986.1 1.6 % Year Ended December 31, 2017 Life Insurance in Force $ 887,857.2 $ 36,545.0 $ 1,045.8 $ 852,358.0 0.1 % Premium Income: Life Insurance $ 2,272.7 $ 135.7 $ 10.2 $ 2,147.2 0.5 % Accident, Health, and Other Insurance 6,404.5 174.4 219.8 6,449.9 3.4 % Total $ 8,677.2 $ 310.1 $ 230.0 $ 8,597.1 2.7 % Year Ended December 31, 2016 Life Insurance in Force $ 854,783.9 $ 31,882.5 $ 1,004.7 $ 823,906.1 0.1 % Premium Income: Life Insurance $ 2,202.6 $ 151.3 $ 9.7 $ 2,061.0 0.5 % Accident, Health, and Other Insurance 6,182.4 112.3 226.6 6,296.7 3.6 % Total $ 8,385.0 $ 263.6 $ 236.3 $ 8,357.7 2.8 %

Schedule V Valuation and Qualif

Schedule V Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2018
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 Additions Charged to Other Accounts (1) Deductions (2) Balance at End of Year (in millions of dollars) Year Ended December 31, 2018 Real Estate reserve (deducted from other long-term investments) $ 4.2 $ 0.6 $ — $ 3.3 $ 1.5 Allowance for doubtful accounts (deducted from accounts and premiums receivable) $ 6.4 $ 5.6 $ — $ 2.1 $ 9.9 Year Ended December 31, 2017 Real Estate reserve (deducted from other long-term investments) $ 4.2 $ — $ — $ — $ 4.2 Allowance for doubtful accounts (deducted from accounts and premiums receivable) $ 6.2 $ 2.3 $ 0.1 $ 2.2 $ 6.4 Year Ended December 31, 2016 Real Estate reserve (deducted from other long-term investments) $ 1.2 $ 3.0 $ — $ — $ 4.2 Allowance for doubtful accounts (deducted from accounts and premiums receivable) $ 6.2 $ 3.1 $ — $ 3.1 $ 6.2 (1) Additions charged to other accounts are comprised of amounts related to fluctuations in the foreign currency exchange rate. (2) Deductions include amounts deemed to reduce exposure of probable losses, amounts deemed uncollectible, and amounts related to fluctuations in the foreign currency exchange rate. See Notes 3 and 7 of the "Notes to Consolidated Financial Statements" contained herein in Item 8 for a discussion of the mortgage loan allowance for credit losses and the deferred tax asset valuation allowance not included in the amounts reported above.

Signficant Accounting Policies

Signficant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation : The accompanying consolidated financial statements of Unum Group and its subsidiaries (the Company) have been prepared in accordance with U.S. generally accepted accounting principles (GAAP). Such accounting principles differ from statutory accounting principles (see Note 15). Intercompany transactions have been eliminated.
Use of Estimates	Use of Estimates : The preparation of financial statements in conformity with GAAP requires us to make estimates and assumptions that affect amounts reported in the financial statements and accompanying notes. Such estimates and assumptions could change in the future as more information becomes known, which could impact the amounts reported and disclosed herein.
Fixed Maturity Securities	Fixed Maturity Securities : Fixed maturity securities include long-term bonds and redeemable preferred stocks. Our fixed maturity securities are classified as available-for-sale and reported at fair value. Changes in the fair value of available-for-sale fixed maturity securities, except for amounts related to other-than-temporary impairment losses recognized in earnings, are reported as a component of other comprehensive income. These amounts are net of income tax and valuation adjustments to deferred acquisition costs and reserves for future policy and contract benefits which would have been recorded had the related unrealized gain or loss on these securities been realized. Interest income is recorded as part of net investment income when earned, using an effective yield method giving effect to amortization of premium and accretion of discount. Included within fixed maturity securities are mortgage-backed and asset-backed securities. We recognize investment income on these securities using a constant effective yield based on projected prepayments of the underlying loans and the estimated economic life of the securities. Actual prepayment experience is reviewed periodically, and effective yields are recalculated when differences arise between prepayments originally projected and the actual prepayments received and currently projected. The effective yield is recalculated on a retrospective basis, and the adjustment is reflected in net investment income. For fixed maturity securities on which collection of investment income is uncertain, we discontinue the accrual of investment income and recognize investment income when interest and dividends are received. Payment terms specified for fixed maturity securities may include a prepayment penalty for unscheduled payoff of the investment. Prepayment penalties are recognized as investment income when received. In determining when a decline in fair value below amortized cost of a fixed maturity security is other than temporary, 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 are other than temporary. The significance of the decline in value and the length of time during which there has been a significant decline are also important factors, but we generally do not record an impairment loss based solely on these two factors, since often other more relevant factors will impact our evaluation of a security. If we determine that the decline in value of an investment is other than temporary, the investment is written down to fair value, and an impairment loss is recognized in the current period, either in earnings or in both earnings and other comprehensive income, as applicable. Other-than-temporary impairment losses on fixed maturity securities which we intend to sell or more likely than not will be required to sell before recovery in value are recognized in earnings and equal the entire difference between the security's amortized cost basis and its fair value. For securities 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, other-than-temporary impairment losses recognized in earnings generally represent 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. For fixed maturity securities for which we have recognized an other-than-temporary impairment loss through earnings, if through subsequent evaluation there is a significant increase in expected cash flows, the difference between the new amortized cost basis and the cash flows expected to be collected is accreted as net investment income over the remaining life of the investment. 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 probable 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. If we determine that it is probable we will be unable to collect all amounts due under the contractual terms of a mortgage loan, we establish an allowance for credit loss. If we expect to foreclose on the property, the amount of the allowance typically equals the excess carrying value of the mortgage loan over the fair value of the underlying collateral. If we expect to retain the mortgage loan until payoff, the allowance equals the excess carrying value of the mortgage loan over the expected future cash flows of the loan. Additions and reductions to our allowance for credit losses on mortgage loans are reported as a component of net realized investment gains and losses. We do not purchase mortgage loans with existing credit impairments. See Note 3.
Policy Loans	Policy Loans : Policy loans are presented at unpaid balances directly related to policyholders. Interest income is accrued on the principal amount of the loan based on the loan's contractual interest rate. Included in policy loans are $3,449.3 million and $3,307.5 million of policy loans ceded to reinsurers at December 31, 2018 and 2017 , respectively.
Investments	Other Long-term Investments : Other long-term investments are comprised primarily of tax credit partnerships and private equity partnerships. Tax credit partnerships in which we have invested were formed for the purpose of investing in the construction and rehabilitation of low-income housing. Because the partnerships are structured such that there is no return of principal, the primary sources of investment return from our tax credit partnerships are tax credits and tax benefits derived from passive losses on the investments, both of which may exhibit variability over the life of the investment. These partnerships are accounted for using either the proportional or the effective yield method, depending primarily on whether the tax credits are guaranteed through a letter of credit, a tax indemnity agreement, or another similar arrangement. Tax credits received from these partnerships are reported in our consolidated statements of income as either a reduction of premium tax or a reduction of income tax. The amortization of the principal amount invested in these partnerships is reported as a component of either premium tax or income tax. Our investments in private equity partnerships are passive in nature and represent funds that are primarily invested in private credit, private equity, and real assets. We account for our investments in these partnerships using either the equity method or at fair value through net income depending on the level of ownership and the degree of our influence over partnership operating and financial policies. For investments in partnerships accounted for under the equity method, we report our investments at our share of the partnership's net asset value (NAV) and record our portion of partnership earnings is recorded 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. See notes 2 and 3 for further discussion of our other long-term investments. Short-term Investments : Short-term investments are carried at cost. Short-term investments include investments maturing within one year of purchase, such as corporate commercial paper and U.S. Treasury bills, bank term deposits, and other cash accounts and cash equivalents earning interest.
Cash and Bank Deposits	Cash and Bank Deposits : Cash and bank deposits include cash on hand and non-interest bearing cash and deposit accounts.
Derivative Financial Instruments	Derivative Financial Instruments : Derivative financial instruments (including certain derivative instruments embedded in other contracts) are recognized as either other long-term investments or other liabilities in our consolidated balance sheets and are reported at fair value. The accounting for a derivative depends on whether it has been designated and qualifies as part of a hedging relationship, and further, on the type of hedging relationship. To qualify for hedge accounting, at the inception of the hedging transaction, we formally document the risk management objective and strategy for undertaking the hedging transaction, as well as the designation of the hedge as either a fair value hedge or a cash flow hedge. Included in this documentation is how the hedging instrument is expected to hedge the designated risk(s) related to specific assets or liabilities on the balance sheet or to specific forecasted transactions as well as a description of the method that will be used to retrospectively and prospectively assess the hedging instrument's effectiveness. A derivative designated as a hedging instrument must be assessed as being highly effective in offsetting the designated risk(s) of the hedged item. Hedge effectiveness is formally assessed at inception and periodically throughout the life of the designated hedging relationship, using qualitative and quantitative methods. Qualitative methods include comparison of critical terms of the derivative to the hedged item. Quantitative methods include regression or other statistical analysis of changes in fair value or cash flows associated with the hedge relationship. Changes in the fair value of a derivative designated as a fair value hedge and changes in the fair value of the hedged item attributable to the risk being hedged are recognized in earnings as a component of net realized investment gain or loss during the period of change in fair value. For gains or losses on the derivative instrument that are excluded from the assessment of hedge effectiveness, those gains and losses are recognized in other comprehensive income or loss and amortized into earnings in the same income statement line as the related hedged item. The gain or loss on the termination of a fair value hedge is recognized in earnings as a component of net realized investment gain or loss during the period in which the termination occurs. When interest rate swaps are used in hedge accounting relationships, periodic settlements are recorded in the same income statement line as the related settlements of the hedged items. Changes in the fair value of a derivative designated as a cash flow hedge are reported in other comprehensive income and reclassified into earnings and reported on the same income statement line item as the hedged item and in the same period or periods during which the hedged item affects earnings. The gain or loss on the termination of an effective cash flow hedge is reported in other comprehensive income and reclassified into earnings and reported on the same income statement line item as the hedged item and in the same period or periods during which the hedged item affects earnings. Gains or losses on the termination of ineffective fair value or cash flow hedges are reported in earnings as a component of net realized investment gain or loss. In the event a hedged item is disposed of or the anticipated transaction being hedged is no longer likely to occur, we will terminate the related derivative and recognize the gain or loss on termination in current earnings as a component of net realized investment gain or loss. In the event a hedged item is disposed of subsequent to the termination of the hedging transaction, we reclassify any remaining gain or loss on the hedge out of accumulated other comprehensive income into earnings as a component of the same income statement line item wherein we report the gain or loss on disposition of the hedged item. For a derivative not designated as a hedging instrument, changes in the fair value of the derivative, together with the payment of periodic fees, if applicable, are recognized in earnings as a component of net realized investment gain or loss during the period of change in fair value. Cash flow activity from the settlement of derivative contracts is reported in the consolidated statements of cash flows as a component of proceeds from sales and maturities of other investments. 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	Fair Value Measurement : Certain assets and liabilities are reported at fair value in our consolidated balance sheets and in our notes to our consolidated financial statements. We define fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. Therefore, fair value represents an exit price, not an entry price. The exit price objective applies regardless of our intent and/or ability to sell the asset or transfer the liability at the measurement date. Assets or liabilities with readily available actively quoted prices or for which fair value can be measured from actively quoted prices in active markets generally have more pricing observability and less judgment utilized in measuring fair value. When actively quoted prices are not available, fair values are based on quoted prices in markets that are not active, quoted prices for similar but not identical assets or liabilities, or other observable inputs. If observable inputs are not available, unobservable inputs and/or adjustments to observable inputs requiring management judgment are used to determine fair value. We categorize our assets and liabilities measured at estimated fair value into a three-level hierarchy, based on the significance of the inputs. The fair value hierarchy gives the highest priority to inputs which are unadjusted and represent quoted prices in active markets for identical assets or liabilities (Level 1) and the lowest priority to unobservable inputs (Level 3). See Note 2.
Realized Investment Gains and Losses	Realized Investment Gains and Losses : Realized investment gains and losses are reported as a component of revenue in the consolidated statements of income and are based upon specific identification of the investments sold. See Note 3.
Deferred Acquisition Costs	Deferred Acquisition Costs : Incremental direct costs associated with the successful acquisition of new or renewal insurance contracts have been deferred. Such costs include commissions, other agency compensation, certain selection and policy issue expenses, and certain field expenses. Acquisition costs that do not vary with the production of new business, such as commissions on group products which are generally level throughout the life of the policy, are excluded from deferral. Deferred acquisition costs are subject to recoverability testing at the time of policy issue and loss recognition testing in subsequent years. Deferred acquisition costs related to non-interest sensitive policies are amortized in proportion to the premium income we expect to receive over the lives of the policies. Deferred acquisition costs related to interest sensitive policies are amortized over the lives of the policies in relation to the present value of estimated gross profits from surrender charges, mortality margins, investment returns, and expense margins. Deviations from projections result in a change to the rate of amortization in the period during which such events occur. Generally, the amortization periods for these policies approximate the estimated lives of the policies. For certain products, policyholders can elect to modify product benefits, features, rights, or coverages by exchanging a contract for a new contract or by amendment, endorsement, or rider to a contract, or by the election of a feature or coverage within a contract. These transactions are known as internal replacement transactions. Internal replacement transactions wherein the modification does not substantially change the policy are accounted for as continuations of the replaced contracts. Unamortized deferred acquisition costs from the original policy continue to be amortized over the expected life of the new policy, and the costs of replacing the policy are accounted for as policy maintenance costs and expensed as incurred. Internal replacement transactions, principally on group contracts, that result in a policy that is substantially changed are accounted for as an extinguishment of the original policy and the issuance of a new policy. Unamortized deferred acquisition costs on the original policy that was replaced are immediately expensed, and the costs of acquiring the new policy are capitalized and amortized in accordance with our accounting policies for deferred acquisition costs. Loss recognition is performed on an annual basis, or more frequently if appropriate, using best estimate assumptions as to future experience as of the date of the test. Insurance contracts are grouped for each major product line within a segment when we perform the loss recognition tests. If loss recognition testing indicates that deferred acquisition costs are not recoverable, the deficiency is charged to expense.
Goodwill	Goodwill : 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. The fair values of the reporting units are determined using discounted cash flow models. The critical estimates necessary in determining fair value are projected earnings and the discount rate. We set our discount rate assumption based on an expected risk adjusted cost of capital. If the fair value of the reporting unit to which the goodwill relates is less than the carrying amount of the unamortized goodwill, the impairment charge is determined by calculating the implied fair value of goodwill by assigning the fair value of a reporting unit to all of its assets and liabilities. The carrying amount of goodwill is then reduced with a corresponding charge to expense.
Property and Equipment	Property and Equipment : Property and equipment is reported at cost less accumulated depreciation, which is calculated on the straight-line method over the estimated useful life. The accumulated depreciation for property and equipment was $1,151.8 million and $1,067.7 million as of December 31, 2018 and 2017 , respectively.
Value of Business Acquired	Value of Business Acquired : Value of business acquired represents the present value of future profits recorded in connection with the acquisition of a block of insurance policies. The asset is amortized based upon expected future premium income for non-interest sensitive insurance policies and estimated future gross profits from surrender charges, mortality margins, investment returns, and expense margins for interest sensitive insurance policies. The value of business acquired, which is included in other assets in our consolidated balance sheets, was $96.7 million and $27.9 million at December 31, 2018 and 2017 , respectively. The accumulated amortization for value of business acquired was $133.0 million and $130.4 million as of December 31, 2018 and 2017 , respectively. The amortization of value of business acquired, which is included in other expenses in the consolidated statements of income, was $6.4 million , $4.8 million , and $5.1 million for the years ended December 31, 2018 , 2017 , and 2016 , respectively. We periodically review the carrying amount of value of business acquired using the same methods used to evaluate deferred acquisition costs.
Policy and Contract Benefits	Policy and Contract Benefits : Policy and contract benefits represent amounts paid and expected to be paid based on reported losses and estimates of incurred but not reported losses for non-interest sensitive life and accident and health products. For interest sensitive products, benefits are the amounts paid and expected to be paid on insured claims in excess of the policyholders' policy fund balances.
Reserves for Policy and Contract Benefits	Reserves for Policy and Contract Benefits : Policy reserves represent future policy and contract benefits for claims not yet incurred. Policy reserves for non-interest sensitive life and accident and health products are determined using the net level premium method. The reserves are calculated based upon assumptions as to interest, persistency, morbidity, and mortality that were appropriate at the date of issue. Discount rate assumptions are based on actual and expected net investment returns. Persistency assumptions are based on our actual historical experience adjusted for future expectations. Claim incidence and claim resolution rate assumptions related to morbidity and mortality are based on actual experience or industry standards adjusted as appropriate to reflect our actual experience and future expectations. The assumptions vary by plan, year of issue, and policy duration and include a provision for adverse deviation. Policy reserves for group single premium annuities are developed on a net single premium method. The reserves are calculated based on assumptions as to interest, mortality, and retirement that were appropriate at the date of issue. Mortality assumptions are based upon industry standards adjusted as appropriate to reflect our actual experience and future expectations. The assumptions vary by year of issue. Policy reserves for interest sensitive products are principally policyholder account values. Policy reserves require ongoing loss recognition testing. We perform loss recognition tests on our policy reserves annually, or more frequently if appropriate, using best estimate assumptions as of the date of the test, without a provision for adverse deviation. We group the policy reserves for each major product line within a segment when we perform the loss recognition tests. If the policy reserves determined using these best estimate assumptions are higher than our existing policy reserves net of any deferred acquisition cost balance, the existing policy reserves are increased or deferred acquisition costs are reduced to immediately recognize the deficiency. This becomes the new basis for policy reserves going forward, subject to future loss recognition testing. Claim reserves represent future policy and contract benefits for claims that have been incurred or are estimated to have been incurred but not yet reported to us. Our claim reserves relate primarily to disability and long-term care policies and are calculated based on assumptions as to interest and claim resolution rates that are currently appropriate. Claim resolution rate assumptions are based on our actual experience. The interest rate assumptions used for discounting claim reserves are based on projected portfolio yield rates, after consideration for defaults and investment expenses, for the assets supporting the liabilities for the various product lines. Unlike policy reserves for which assumptions are generally established and locked in at the time of policy issuance, claim reserves are subject to revision as current claim experience and projections of future factors affecting claim experience change. Claim reserves do not include a provision for adverse deviation. See Note 6.
Policyholders' Funds	Policyholders' Funds : Policyholders' funds represent customer deposits plus interest credited at contract rates. We control interest rate risk by investing in quality assets which have an aggregate duration that closely matches the expected duration of the liabilities.
Income Tax	Income Tax : Deferred taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial statement purposes and the amounts used for income tax purposes. Deferred taxes have been measured using enacted statutory income tax rates and laws that are currently in effect. We record adjustments to our deferred taxes resulting from tax rate changes through income as of the date of enactment. We record deferred tax assets for tax positions taken in the U.S. and other tax jurisdictions based on our assessment of whether a position is more likely than not to be sustained upon examination based solely on its technical merits. A valuation allowance is established for deferred tax assets when it is more likely than not that an amount will not be realized. See Note 7.
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. Original issue discount or premium as well as debt issuance costs are recognized as a component of interest expense over the period the debt is expected to be outstanding. The carrying amount of long-term debt that is part of a fair value hedge program includes an adjustment to reflect the effect of the change in fair value attributable to the risk being hedged. Net interest settlements for fair value hedges on our long-term debt are recognized as a component of interest expense. See Note 8.
Treasury Stock and Retirement of Common Stock	Treasury Stock and Retirement of Common Stock : Treasury stock is reflected as a reduction of stockholders' equity at cost. When shares are retired, the par value is removed from common stock, and the excess of the repurchase price over par is allocated between additional paid-in capital and retained earnings. See Note 10.
Revenue Recognition	Revenue Recognition: Our non-interest sensitive life and accident and health products are long-duration contracts, and premium income is recognized as revenue when due from policyholders. If the contracts are experience rated, the estimated ultimate premium is recognized as revenue over the period of the contract. The estimated ultimate premium, which is revised to reflect current experience, is based on estimated claim costs, expenses, and profit margins. For interest sensitive products, the amounts collected from policyholders are considered deposits, and only the deductions during the period for cost of insurance, policy administration, and surrenders are included in revenue. Policyholders' funds represent funds deposited by contract holders and are not included in revenue.
Revenue from Service Fees	Fees from our administrative-services only and family medical leave products are reported as other income when services are rendered.
Reinsurance	Reinsurance : We routinely enter into reinsurance agreements with other insurance companies to spread risk and thereby limit losses from large exposures. For each of our reinsurance agreements, we determine if the agreement provides indemnification against loss or liability relating to insurance risk in accordance with applicable accounting standards. If we determine that a reinsurance agreement does not expose the reinsurer to a reasonable possibility of a significant loss from insurance risk, we record the agreement using the deposit method of accounting. Reinsurance activity is accounted for on a basis consistent with the terms of the reinsurance contracts and the accounting used for the original policies issued. Premium income and benefits and change in reserves for future benefits are presented in our consolidated statements of income net of reinsurance ceded. Ceded liabilities for policy and contract benefits, future policy and contract benefits, and unearned premiums are reported on a gross basis in our consolidated balance sheets, as are ceded policy loans. Our reinsurance recoverable includes the balances due from reinsurers under the terms of the reinsurance agreements for these ceded balances as well as settlement amounts currently due. Where applicable, gains or losses on reinsurance transactions are 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. The deferred gain on reinsurance included in other liabilities in our consolidated balance sheets at December 31, 2018 and 2017 was $12.5 million and $17.7 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. In the event that reinsurers do not meet their obligations to us under the terms of the reinsurance agreements, certain amounts reported in our reinsurance recoverable could become uncollectible, in which case the reinsurance recoverable balances are stated net of allowances for uncollectible reinsurance. See Note 12.
Premium Tax Expense	Premium Tax Expense : Premium tax expense is included in other expenses in the consolidated statements of income. For the years ended December 31, 2018 , 2017 , and 2016 , premium tax expense was $155.8 million , $158.0 million , and $152.5 million , respectively.
Stock-Based Compensation	Stock-Based Compensation : The cost of stock-based compensation is generally measured based on the grant-date fair value of the award. The Black-Scholes options valuation model is used for estimating the fair value of stock options, and the Monte-Carlo valuation model is used for estimating the fair value of performance share units. Restricted stock units are valued based on the fair value of common stock at the grant date. Stock-based awards are expensed over the requisite service period, or for performance share units over the requisite service period, or remaining service period, if and when it becomes probable that the performance conditions will be satisfied, with an offsetting increase to additional paid-in capital in stockholders' equity. Forfeitures of stock-based awards are recognized as they occur. See Note 11.
Earnings Per Share	Earnings Per Share : We compute basic earnings per share by dividing net income by the weighted average number of common shares outstanding for the period. Earnings per share assuming dilution is computed by dividing net income by the weighted average number of shares outstanding for the period plus the shares representing the dilutive effect of stock-based awards. In computing earnings per share assuming dilution, only potential common shares resulting from stock-based awards that are dilutive (those that reduce earnings per share) are included. We use the treasury stock method to account for the effect of outstanding stock options and nonvested stock awards on the computation of earnings per share assuming dilution. See Note 10.
Translation of Foreign Curency	Translation of Foreign Currency : Revenues and expenses of our foreign operations are translated at average exchange rates. Assets and liabilities are translated at the rate of exchange on the balance sheet dates. The translation gain or loss is generally reported in accumulated other comprehensive income, net of deferred 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 $301.2 million and $328.3 million at December 31, 2018 and 2017 , respectively.
Accounting Updates Outstanding	Accounting Updates Outstanding: ASC Description Date of Adoption Effect on Financial Statements ASC 220 "Income Statement - Reporting Comprehensive Income" This update allows entities to make an optional accounting policy election to reclassify the stranded tax effects arising as a result of the recognition of the enactment of the tax bill, H.R.1, An Act to Provide Reconciliation Pursuant to Titles II and V of the Concurrent Resolution on the Budget for Fiscal Year 2018, more commonly known as the Tax Cuts and Jobs Act (TCJA) from accumulated other comprehensive income to retained earnings. Tax effects that are stranded in accumulated other comprehensive income for reasons other than the TCJA may not be reclassified. This update requires additional disclosures on whether an entity elects to reclassify the stranded tax effects and its policy for releasing tax effects from accumulated other comprehensive income. This guidance may be applied in the period of adoption or retrospectively to each period in which the effect of the change in federal income tax rate in the TCJA is recognized, with early adoption permitted. January 1, 2019 The adoption of this update will expand certain of our disclosures but will have no impact on our financial position or results of operations because we do not intend to make the optional accounting policy election to reclassify the stranded tax effects resulting from the TCJA from accumulated other comprehensive income to retained earnings. ASC 310 "Receivables - Nonrefundable Fees and Other Costs" This update shortens the amortization period to the earliest call date for certain callable debt securities held at a premium. This update does not impact securities held at a discount. The guidance is to be applied using a modified retrospective approach through a cumulative-effect adjustment to retained earnings as of the beginning of the period of adoption, with early adoption permitted. January 1, 2019 We have determined that certain of our callable debt securities are within the scope of this update. The adoption of this update will not have a material impact on our financial position or results of operations. ASC Description Date of Adoption Effect on Financial Statements ASC 718 "Compensation - Stock Compensation" This update generally aligns the accounting guidance for share-based payments issued to non-employees with guidance for share-based payments issued to employees. Specifically, the update requires non-employee share-based payments to be measured using the grant date fair value of the equity instruments that an entity is obligated to issue when the good has been delivered or the service has been rendered rather than being remeasured through the performance completion date. Additionally, for non-employee share-based payments that contain performance conditions, the update will change the criteria regarding the recognition of compensation cost to when achievement of a performance condition is probable rather than upon actual achievement of the performance condition. The guidance is to be applied using a modified retrospective approach through a cumulative-effect adjustment to retained earnings as of the beginning of the period of adoption, with early adoption permitted. For purposes of determining the cumulative effect adjustment, the guidance shall be applied only to equity-classified non-employee share-based payments for which a measurement date has not been established and liability-classified non-employee share-based payments that have not been settled as of the date of adoption. January 1, 2019 The adoption of this update will not have an impact on our financial position or results of operations. ASC 842 "Leases" This update changes the accounting for leases, requiring lessees to report most leases on their balance sheets, regardless of whether the lease is classified as a finance lease or an operating lease. For lessees, the initial lease liability is equal to the present value of lease payments, and a corresponding right-of-use asset, adjusted for certain items, is also recorded. Expense recognition for lessees will remain similar to current accounting requirements for capital and operating leases. For lessors, the guidance modifies the classification criteria and the accounting for sales-type and direct financing leases. The guidance may be applied using a modified retrospective approach at either the beginning of the earliest comparative period presented or as of the beginning of the period of adoption. The guidance also allows practical expedients related to adoption considerations for leases that commenced before the date of adoption. Early adoption is permitted. January 1, 2019 We will adopt this update using the modified retrospective transition option that allows for application of the guidance at the beginning of the period of adoption. The adoption of this update on January 1, 2019 will result in the recognition of a lease liability of approximately $125 million with a corresponding right-of-use asset, less an immaterial cumulative-effect decrease to retained earnings related to our operating leases. We will elect to apply the package of practical expedients available to leases that commenced prior to the date of adoption. We do not expect this update to have an impact to our results of operations but it will expand our disclosures. ASC Description Date of Adoption Effect on Financial Statements ASC 326 "Financial Instruments - Credit Losses" This update amends the guidance on the impairment of financial instruments. The update adds an impairment model known as the current expected credit loss model that is based on expected losses rather than incurred losses and will generally result in earlier recognition of allowances for losses. The current expected credit loss model applies to financial instruments such as mortgage loans, fixed maturity securities classified as held-to-maturity, and certain receivables. The update also modifies the other-than-temporary impairment model used for available-for-sale fixed maturity securities such that credit losses are recognized as an allowance rather than as a reduction in the amortized cost of the security. The reversal of previously recognized credit losses on available-for-sale fixed maturity securities is allowed under specified circumstances. Additional disclosures will also be required, including information used to develop the allowance for losses. The guidance is to be applied to most instruments in scope using a modified retrospective approach through a cumulative-effect adjustment to retained earnings as of the beginning of the period of adoption. For available-for-sale fixed maturity securities, the update is applied prospectively. Other-than-temporary impairment losses recognized on available-for-sale fixed maturity securities prior to adoption of the update cannot be reversed. Early adoption is permitted. January 1, 2020 We have not yet determined the expected impact on our financial position or results of operations. ASC 350 "Intangibles - Goodwill and Other" This update eliminates the requirement to calculate the implied fair value of goodwill (the second step in the current two-step test) to measure a goodwill impairment charge. Instead, entities should perform the goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount and recognize an impairment charge for the excess of the carrying amount over the fair value, with the loss not to exceed the total amount of goodwill allocated to that reporting unit. The guidance is to be applied prospectively, with early adoption permitted for goodwill impairment tests performed on testing dates after January 1, 2017. January 1, 2020 The adoption of this update will not have a material effect on our financial position or results of operations. ASC 715 "Compensation - Retirement Benefits" This update amends the defined benefit pension and other postretirement benefit guidance by removing or clarifying certain existing disclosures requirements, while also adding new disclosure requirements. Specifically, this update removes the requirement to disclose the effects of a one-percentage point change in the assumed healthcare cost trend and the requirement to disclose amounts in accumulated other comprehensive income expected to be recognized as part of net periodic benefit cost of the next year. This update adds a requirement to describe the reasons for significant gains and losses related to changes in the benefit obligation for the period. The update also clarifies that the projected benefit obligation (PBO) and accumulated benefit obligation (ABO) and fair value of plan assets are to be disclosed for plans with PBOs or ABOs in excess of plan assets. The guidance is to be applied retrospectively and early adoption is permitted. December 31, 2020 We have not yet determined the expected impact on our disclosures. ASC Description Date of Adoption Effect on Financial Statements ASC 944 "Financial Services - Insurance" This update significantly amends the accounting and disclosure requirements for long-duration insurance contracts. These changes include a requirement to review, and if necessary, update cash flow assumptions used to measure the liability for future policy benefits for traditional and limited-payment contracts at least annually, with changes recognized in earnings. In addition, an entity will be required to update the discount rate assumption at each reporting date using a yield that is reflective of an upper-medium grade fixed-income instrument, with changes recognized in other comprehensive income. These changes result in the elimination of the provision for risk of adverse deviation and premium deficiency (or loss recognition) testing. The update also requires that an entity measure all market risk benefits associated with deposit contracts at fair value, with changes recognized in earnings except for the portion attributable to a change in the instrument-specific credit risk, which is to be recognized in other comprehensive income. This update also simplifies the amortization of deferred acquisition costs by requiring amortization on a constant level basis over the expected term of the related contracts. Deferred acquisition costs are required to be written off for unexpected contract terminations but are no longer subject to an impairment test. Significant additional disclosures will also be required, which include disaggregated rollforwards of certain liability balances and the disclosure of qualitative and quantitative information about expected cash flows, estimates, and assumptions. The application of this guidance will vary based upon the specific requirements of the update but will generally result in either a modified retrospective or full retrospective approach with changes applied as of the beginning of the earliest period presented. Early adoption is permitted. January 1, 2021 We have not yet determined the expected impact on our financial position or results of operations.

Significant Accounting Polici_2

Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of New Accounting Pronouncements	Accounting Updates Adopted in 2018: Accounting Standards Codification (ASC) Description Date of Adoption Effect on Financial Statements ASC 230 "Statement of Cash Flows" This update provided clarifying guidance intended to reduce the diversity in practice in how certain cash receipts and cash payments are presented and classified in the statement of cash flows. The update addressed eight specific cash flow issues that relate to various types of transactions. The guidance was applied retrospectively. January 1, 2018 The adoption of this update resulted in the reclassification of certain cash inflows between investing activities and operating activities within our consolidated statements of cash flows. The reclassification primarily related to cash distributions from equity method investees and the bifurcation of those distributions as either returns on investment or returns of investment which resulted in a reclassification of cash inflows from investing activities to operating activities. The remaining portion of the reclassification related to the receipt of proceeds from corporate-owned life insurance benefits which resulted in a reclassification of cash inflows from operating activities to investing activities. The adoption of this update had no effect on our financial position or results of operations. See the summary tables contained herein for the financial statement impacts of this retrospective adoption. ASC 606 "Revenue from Contracts with Customers" These updates superseded virtually all existing guidance regarding the recognition of revenue from customers. Specifically excluded from the scope of these updates are insurance contracts, although our fee-based service products are included within the scope. Our fee-based service products, which are primarily sold in our Unum US segment, are reported in other income within our consolidated statements of income and represent less than one percent of our total revenue. The core principle of this guidance is that revenue recognition should depict the transfer of goods or services to customers in an amount that reflects the consideration to which an entity expects to be entitled in exchange for those goods or services. Accordingly, we continue to recognize revenue for these fee-based service products as services are rendered. The guidance was applied retrospectively for all periods presented or retrospectively with a cumulative-effect adjustment at the date of adoption. January 1, 2018 The adoption of these updates did not have an impact on our financial position or results of operations and did not result in expanded disclosures due to the immaterial nature of our fee-based service products relative to our overall business. ASC Description Date of Adoption Effect on Financial Statements ASC 715 "Compensation - Retirement Benefits" This update required the service cost component of net periodic pension and postretirement benefit costs to be included as a component of compensation costs in an entity's statement of income. Other components of net periodic pension and postretirement benefit costs are required to be presented separately from the service cost along with a disclosure identifying the line items in which these costs are presented in the statement of income. The amendments in this update were applied retrospectively or prospectively depending on the specific requirement of the update. January 1, 2018 The adoption of this update resulted in the reclassification of service cost from the other expenses line item to the compensation expense line item on our consolidated statements of income but had no effect on our financial position or results of operations. We elected to use the practical expedient for the retrospective application of this update. See the summary tables contained herein for the financial statement impacts of this retrospective adoption. ASC 740 "Income Taxes" This update eliminated the exception that required the tax effect of intra-entity asset transfers other than inventory to be deferred until the transferred asset is sold to a third party or otherwise recovered through use. It required recognition of tax expense from the sale of the asset in the seller’s tax jurisdiction when the transfer occurs, even though the pre-tax effects of that transaction are eliminated in consolidation. The guidance was applied retrospectively. January 1, 2018 The adoption of this update did not have an impact on our financial position or results of operations. ASC 815 "Derivatives and Hedge Accounting" This update provided targeted improvements to accounting for hedging activities for both nonfinancial and financial risk components, aligns the recognition and presentation of the effects of the hedging instrument and the hedged item in the financial statements, eases certain documentation and effectiveness assessment requirements, and enhances transparency through expanded disclosures. For cash flow and net investment hedges existing at the date of adoption, the guidance was applied using a modified retrospective approach through a cumulative-effect adjustment to accumulated other comprehensive income with a corresponding adjustment to retained earnings as of the beginning of the fiscal year the guidance is adopted. The amended presentation and disclosure guidance were required prospectively. Early adoption was permitted. January 1, 2018 We elected to early adopt this update. The adoption of this update did not have an impact on our financial position or results of operations; however, it expanded our disclosures. This update also simplified hedge documentation requirements and expanded available hedging strategies. ASC Description Date of Adoption Effect on Financial Statements ASC 820 "Fair Value Measurement" This update amended the fair value measurement guidance by removing or clarifying certain existing disclosure requirements, while also adding new disclosure requirements. Specifically, this update removed certain disclosures related to Level 1 and Level 2 transfers and also removed the discussion regarding valuation processes of Level 3 fair value measurements. The update modifies guidance related to investments in certain entities that calculate net asset value to explicitly require disclosure regarding timing of liquidation of the investee's assets and timing of redemption restrictions. The update adds disclosures around the changes in unrealized gains and losses in other comprehensive income for recurring Level 3 investments held at the end of the reporting period and adds disclosures regarding certain unobservable inputs on Level 3 fair value measurements. The guidance was applied retrospectively or prospectively depending on the specific requirement of the update. Entities are permitted to early adopt any removed or modified disclosures and may delay adoption of the additional disclosures until their effective date. December 31, 2018 for the removal and modification of certain disclosures and January 1, 2020 for the addition of certain disclosures. We elected to early adopt the removal and modification of disclosures, as permitted by the update. We have elected to delay the adoption of the additional disclosures until the effective date. The adoption of this update will modify our disclosures but will not have an impact on our financial position or results of operations. ASC 825 "Financial Instruments - Overall" This update changed the accounting and disclosure requirements for certain financial instruments. These changes include a requirement to measure equity investments, other than those that result in consolidation or are accounted for under the equity method, at fair value through net income unless the investment qualifies for certain practicability exceptions. In addition, the update clarified guidance related to the valuation allowance assessment when recognizing deferred tax assets resulting from unrealized losses on available-for-sale fixed maturity securities. Changes also included the modification of certain disclosures around the fair value of financial instruments, including the requirement for separate presentation of financial assets and liabilities by measurement category, as well as the elimination of certain disclosures around methods and significant assumptions used to estimate fair value. The guidance was applied using a modified retrospective approach through a cumulative-effect adjustment to accumulated other comprehensive income with a corresponding adjustment to retained earnings as of the beginning of the fiscal year of adoption. January 1, 2018 See the summary tables contained herein for the financial statement impacts of this modified retrospective adoption on our financial statement line items at January 1, 2018. Summary of Financial Statement Impacts of Accounting Updates Adopted in 2018: For the Year Ended December 31 2017 2016 Historical Accounting Method As Adjusted Effect of Change Historical Accounting Method As Adjusted Effect of Change (in millions of dollars) Adjustments due to ASC 230 Consolidated Statements of Cash Flow Cash Flows from Operating Activities Other, Net $ 12.8 $ 27.5 $ 14.7 $ 32.9 $ 38.4 $ 5.5 Cash Flows from Investing Activities Proceeds from Sales and Maturities of Other Investments 272.6 257.9 (14.7 ) 336.8 331.3 (5.5 ) For the Year Ended December 31 2017 2016 Historical Accounting Method As Adjusted Effect of Change Historical Accounting Method As Adjusted Effect of Change (in millions of dollars) Adjustments due to ASC 715 Consolidated Statements of Income Compensation Expense $ 844.4 $ 852.3 $ 7.9 $ 832.1 $ 839.1 $ 7.0 Other Expenses 862.9 855.0 (7.9 ) 831.6 824.6 (7.0 ) Balance at December 31, 2017 Balance at January 1, 2018 Effect of Change (in millions of dollars) Adjustments due to ASC 825 Consolidated Balance Sheets Assets Investments Other Long-term Investments $ 646.8 $ 643.0 $ (3.8 ) Liabilities Deferred Income Tax 199.0 198.2 (0.8 ) Stockholders' Equity Accumulated Other Comprehensive Income (Loss) 127.5 110.0 (17.5 ) Retained Earnings 9,542.2 9,556.7 14.5 For the adoption of these updates, certain reclassifications have been made to prior year amounts in order to conform to current year presentation. Accounting Updates Adopted in 2017: ASC Description Date of Adoption Effect on Financial Statements ASC 944 "Financial Services - Insurance" This update changed the disclosure requirements for certain insurance contracts. These changes included a requirement to disclose the rollforward of the liability for unpaid claims and claim adjustment expenses in both interim and annual reporting periods for long-duration and short-duration insurance contracts. Additional claims disclosures were also required for short-duration contracts. The guidance was applied retrospectively. January 1, 2016 for annual reporting period disclosures and January 1, 2017 for interim reporting period disclosures. The adoption of this update expanded our interim reporting period disclosures but had no effect on our financial position or results of operations. The annual reporting period disclosure requirements were only applicable to our individual dental products, which we deem immaterial, and therefore did not alter our annual disclosures. ASC 718 "Compensation - Stock Compensation" This update changed the accounting and disclosure requirements for certain aspects of share-based payments to employees. The update required all income tax effects of stock-based compensation awards to be recognized in the income statement when the awards vest or are settled. The update also allows an employer to repurchase more of an employee's shares than it can today for tax withholding purposes without triggering liability accounting and to make a policy election to account for forfeitures as they occur. Additionally, the update required reclassification of tax-related cash flows resulting from share-based payments to be classified as operating activities instead of financing activities on the statement of cash flows. Transition guidance for the amendments varied between the retrospective, modified retrospective, and prospective methods depending on the specific requirement of the update. January 1, 2017 The adoption of this update did not have a material effect on our financial position or results of operations. The impact of the update reduced our effective income tax rate by a de minimis amount for the year ended December 31, 2017. During periods in which the vesting date fair value differs from the grant date fair value of certain stock-based compensation awards, we may experience volatility in the income tax recognized in our results of operations. The amendment related to the reclassification of tax-related cash flows in our consolidated statements of cash flows has been applied prospectively. Accounting Updates Adopted in 2016: ASC Description Date of Adoption Effect on Financial Statements ASC 820 "Fair Value Measurement" This update eliminated the requirement to categorize within the fair value hierarchy table investments whose fair value is measured at net asset value using the practical expedient. Instead, entities are required to disclose the fair value of these investments so that financial statement users can reconcile amounts reported in the fair value hierarchy table to the amounts reported on the consolidated balance sheets. The guidance was applied retrospectively. January 1, 2016 The adoption of this update modified certain of our annual reporting period disclosures for invested assets held in our employee benefit plans but had no effect on our financial position or results of operations. ASC 835 "Interest - Imputation of Interest" This update simplified the presentation of deferred debt issuance costs by requiring these costs to be presented in the balance sheet as a reduction of the carrying amount of the debt liability to which the deferred costs relate, rather than classifying the deferred costs as an asset. This classification is consistent with the treatment of debt discounts. We applied the amendments in the update retrospectively, adjusting all prior periods in our consolidated financial statements and accompanying notes. January 1, 2016 The adoption of this update resulted in reclassification adjustments to our consolidated balance sheets but had no effect on our financial position or results of operations.
New Accounting Pronouncements and Changes in Accounting Principles [Text Block]	Summary of Financial Statement Impacts of Accounting Updates Adopted in 2018: For the Year Ended December 31 2017 2016 Historical Accounting Method As Adjusted Effect of Change Historical Accounting Method As Adjusted Effect of Change (in millions of dollars) Adjustments due to ASC 230 Consolidated Statements of Cash Flow Cash Flows from Operating Activities Other, Net $ 12.8 $ 27.5 $ 14.7 $ 32.9 $ 38.4 $ 5.5 Cash Flows from Investing Activities Proceeds from Sales and Maturities of Other Investments 272.6 257.9 (14.7 ) 336.8 331.3 (5.5 ) For the Year Ended December 31 2017 2016 Historical Accounting Method As Adjusted Effect of Change Historical Accounting Method As Adjusted Effect of Change (in millions of dollars) Adjustments due to ASC 715 Consolidated Statements of Income Compensation Expense $ 844.4 $ 852.3 $ 7.9 $ 832.1 $ 839.1 $ 7.0 Other Expenses 862.9 855.0 (7.9 ) 831.6 824.6 (7.0 ) Balance at December 31, 2017 Balance at January 1, 2018 Effect of Change (in millions of dollars) Adjustments due to ASC 825 Consolidated Balance Sheets Assets Investments Other Long-term Investments $ 646.8 $ 643.0 $ (3.8 ) Liabilities Deferred Income Tax 199.0 198.2 (0.8 ) Stockholders' Equity Accumulated Other Comprehensive Income (Loss) 127.5 110.0 (17.5 ) Retained Earnings 9,542.2 9,556.7 14.5 For the adoption of these updates, certain reclassifications have been made to prior year amounts in order to conform to current year presentation.

Fair Values of Financial Inst_2

Fair Values of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share	The following table presents additional information about our private equity partnerships as of December 31, 2018 , including commitments for additional investments which may or may not be funded: Investment Category Fair Value Redemption Term / Redemption Notice Unfunded Commitments (in millions of dollars) (in millions of dollars) Private Credit (a) $ 168.6 Not redeemable $ 99.5 25.7 Initial 2 year lock on each new investment / Quarterly after 2 year lock with 90 days notice 10.3 Total Private Credit 194.3 109.8 Private Equity (b) 128.3 Not redeemable 169.5 Real Assets (c) 131.0 Not redeemable 106.0 30.2 Quarterly / 90 days notice — Total Real Assets 161.2 106.0 Total Partnerships $ 483.8 $ 385.3 (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, 2018 , the estimated remaining life of the investments that do not allow for redemptions is approximately 20 percent in the next 3 years, 46 percent during the period from 3 to 5 years, 30 percent during the period from 5 to 10 years, and 4 percent after the period of 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, 2018 , the estimated remaining life of the investments that do not allow for redemptions is approximately 40 percent in the next 3 years, 9 percent during the period from 3 to 5 years, 49 percent during the period from 5 to 10 years, 1 percent during the period from 10 to 15 years, and 1 percent after the period of 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, 2018 , the estimated remaining life of the investments that do not allow for redemptions is approximately 2 percent in the next 3 years, 19 percent during period from 3 to 5 years, 75 percent during the period from 5 to 10 years, and 4 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, 2018 Level 1 Level 2 Level 3 NAV Total (in millions of dollars) Assets Fixed Maturity Securities United States Government and Government Agencies and Authorities $ 513.4 $ 1,301.0 $ — $ — $ 1,814.4 States, Municipalities, and Political Subdivisions — 2,424.2 — — 2,424.2 Foreign Governments — 952.3 31.4 — 983.7 Public Utilities 286.4 7,041.7 84.7 — 7,412.8 Mortgage/Asset-Backed Securities — 1,582.7 — — 1,582.7 All Other Corporate Bonds 4,232.1 23,026.1 1,495.8 — 28,754.0 Redeemable Preferred Stocks — 18.8 21.1 — 39.9 Total Fixed Maturity Securities 5,031.9 36,346.8 1,633.0 — 43,011.7 Other Long-term Investments Derivatives Foreign Exchange Contracts — 30.4 — — 30.4 Credit Default Swaps — 0.5 — — 0.5 Equity Securities — 24.6 4.6 — 29.2 Private Equity Partnerships — — — 483.8 483.8 Total Other Long-term Investments — 55.5 4.6 483.8 543.9 Total Financial Instrument Assets Carried at Fair Value $ 5,031.9 $ 36,402.3 $ 1,637.6 $ 483.8 $ 43,555.6 Liabilities Other Liabilities Derivatives Interest Rate Swaps $ — $ 5.2 $ — $ — $ 5.2 Foreign Exchange Contracts — 32.8 — — 32.8 Embedded Derivative in Modified Coinsurance Arrangement — — 31.1 — 31.1 Total Derivatives — 38.0 31.1 — 69.1 Total Financial Instrument Liabilities Carried at Fair Value $ — $ 38.0 $ 31.1 $ — $ 69.1 December 31, 2017 Level 1 Level 2 Level 3 NAV Total (in millions of dollars) Assets Fixed Maturity Securities United States Government and Government Agencies and Authorities $ 460.1 $ 1,022.4 $ — $ — $ 1,482.5 States, Municipalities, and Political Subdivisions — 2,336.9 — — 2,336.9 Foreign Governments — 863.9 — — 863.9 Public Utilities 154.2 7,874.6 207.7 — 8,236.5 Mortgage/Asset-Backed Securities — 1,973.6 — — 1,973.6 All Other Corporate Bonds 3,556.1 25,816.2 1,150.1 — 30,522.4 Redeemable Preferred Stocks — 19.2 22.8 — 42.0 Total Fixed Maturity Securities 4,170.4 39,906.8 1,380.6 — 45,457.8 Other Long-term Investments Derivatives Foreign Exchange Contracts — 19.5 — — 19.5 Equity Securities 0.2 10.4 1.1 — 11.7 Private Equity Partnerships — — — 407.2 407.2 Total Other Long-term Investments 0.2 29.9 1.1 407.2 438.4 Total Financial Instrument Assets Carried at Fair Value $ 4,170.6 $ 39,936.7 $ 1,381.7 $ 407.2 $ 45,896.2 Liabilities Other Liabilities Derivatives Interest Rate Swaps $ — $ 5.1 $ — $ — $ 5.1 Foreign Exchange Contracts — 46.9 — — 46.9 Credit Default Swaps — 0.2 — — 0.2 Embedded Derivative in Modified Coinsurance Arrangement — — 15.9 — 15.9 Total Derivatives — 52.2 15.9 — 68.1 Total Financial Instrument Liabilities Carried at Fair Value $ — $ 52.2 $ 15.9 $ — $ 68.1
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, 2018 Total Realized and Unrealized Investment Gains (Losses) Included in Fair Value Beginning of Year Earnings Other Comprehensive Income or Loss Purchases Sales Level 3 Transfers Fair Value End of Year Into Out of (in millions of dollars) Fixed Maturity Securities Foreign Governments $ — $ — $ (1.4 ) $ — $ — $ 32.8 $ — $ 31.4 Public Utilities 207.7 — (2.3 ) — — 39.0 (159.7 ) 84.7 All Other Corporate Bonds 1,150.1 5.8 (118.1 ) 95.1 (148.7 ) 968.6 (457.0 ) 1,495.8 Redeemable Preferred Stocks 22.8 — (1.7 ) — — — — 21.1 Total Fixed Maturity Securities 1,380.6 5.8 (123.5 ) 95.1 (148.7 ) 1,040.4 (616.7 ) 1,633.0 Equity Securities 1.1 — — 3.5 — — — 4.6 Embedded Derivative in Modified Coinsurance Arrangement (15.9 ) (15.2 ) — — — — — (31.1 ) Year Ended December 31, 2017 Total Realized and Unrealized Investment Gains (Losses) Included in Fair Value Beginning Earnings Other Comprehensive Income or Loss Purchases Sales Level 3 Transfers Fair Value End of Into Out of (in millions of dollars) Fixed Maturity Securities States, Municipalities, and Political Subdivisions $ 89.5 $ — $ — $ — $ — $ — $ (89.5 ) $ — Public Utilities 265.3 — 0.3 8.0 (4.8 ) 125.2 (186.3 ) 207.7 All Other Corporate Bonds 1,459.7 (0.6 ) 2.8 118.9 (149.2 ) 524.7 (806.2 ) 1,150.1 Redeemable Preferred Stocks 23.2 — (0.4 ) — — — — 22.8 Total Fixed Maturity Securities 1,837.7 (0.6 ) 2.7 126.9 (154.0 ) 649.9 (1,082.0 ) 1,380.6 Equity Securities 1.2 — — — — — (0.1 ) 1.1 Embedded Derivative in Modified Coinsurance Arrangement (46.7 ) 30.8 — — — — — (15.9 ) Realized and unrealized investment gains and losses presented in the preceding tables represent gains and losses only for the time during which the applicable financial instruments were classified as Level 3. The transfers between levels resulted primarily from a change in observability of three inputs used to determine fair values of the securities transferred: (1) transactional data for new issuance and secondary trades, (2) broker/dealer quotes and pricing, primarily related to changes in the level of activity in the market and whether the market was considered orderly, and (3) comparable bond metrics from which to perform an analysis. For fair value measurements of financial instruments that were transferred either into or out of Level 3, we reflect the transfers using the fair value at the beginning of the period. We believe this allows for greater transparency, as all changes in fair value that arise during the reporting period of the transfer are disclosed as a component of our Level 3 reconciliation. Gains (losses) which are included in earnings and are attributable to the change in fair value of assets or liabilities valued using significant unobservable inputs and still held at each year end were $(15.2) million and $30.8 million for the years ended December 31, 2018 and 2017 , respectively. These amounts relate entirely to the change in fair value of an embedded derivative in a modified coinsurance arrangement and are reported as a component of realized investment gains and losses.
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. 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, 2018 Fair Value Valuation Method Unobservable Input Range/Weighted Average (in millions of dollars) Fixed Maturity Securities All Other Corporate Bonds - Private $ 148.5 Market Approach Lack of Marketability Equity Securities - Private 4.6 Market Approach Market Convention (d) Priced at Cost or Owner's Equity Embedded Derivative in Modified Coinsurance Arrangement (31.1 ) Discounted Cash Flows Projected Liability Cash Flows (e) Actuarial Assumptions December 31, 2017 Fair Value Valuation Method Unobservable Input Range/Weighted Average (in millions of dollars) Fixed Maturity Securities All Other Corporate Bonds - Private $ 244.4 Market Approach Comparability Adjustment (a) 0.20% - 0.20% / 0.20% Equity Securities - Private 1.1 Market Approach Market Convention (d) Priced at Cost or Owner's Equity Embedded Derivative in Modified Coinsurance Arrangement (15.9 ) Discounted Cash Flows Projected Liability Cash Flows (e) Actuarial Assumptions (a) Represents basis point adjustments for changes in benchmark spreads associated with various industry sectors (b) Represents basis point adjustments to apply a discount due to the illiquidity of an investment (c) Represents basis point adjustments for credit-specific factors (d) Represents a decision to price based on par value, cost, or owner's equity when limited data is available (e) Represents various actuarial assumptions required to derive the liability cash flows including incidence, termination, and lapse rates
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, 2018 Estimated Fair Value Level 1 Level 2 Level 3 Total Carrying Value (in millions of dollars) Assets Mortgage Loans $ — $ 2,317.4 $ — $ 2,317.4 $ 2,295.0 Policy Loans — — 3,831.1 3,831.1 3,729.9 Other Long-term Investments Miscellaneous Long-term Investments — 24.1 91.5 115.6 115.6 Total Financial Instrument Assets Not Carried at Fair Value $ — $ 2,341.5 $ 3,922.6 $ 6,264.1 $ 6,140.5 Liabilities Long-term Debt $ 1,429.8 $ 1,639.4 $ — $ 3,069.2 $ 2,971.3 Payables for Collateral on Investments Federal Home Loan Bank (FHLB) Funding Agreements — 104.0 — 104.0 104.0 Other Liabilities Unfunded Commitments — 2.3 — 2.3 2.3 Total Financial Instrument Liabilities Not Carried at Fair Value $ 1,429.8 $ 1,745.7 $ — $ 3,175.5 $ 3,077.6 December 31, 2017 Estimated Fair Value Level 1 Level 2 Level 3 Total Carrying Value (in millions of dollars) Assets Mortgage Loans $ — $ 2,306.2 $ — $ 2,306.2 $ 2,213.2 Policy Loans — — 3,677.5 3,677.5 3,571.1 Other Long-term Investments Miscellaneous Long-term Investments — 34.1 128.2 162.3 162.3 Total Financial Instrument Assets Not Carried at Fair Value $ — $ 2,340.3 $ 3,805.7 $ 6,146.0 $ 5,946.6 Liabilities Long-term Debt $ 1,171.8 $ 1,876.9 $ — $ 3,048.7 $ 2,738.4 Payables for Collateral on Investments Federal Home Loan Bank (FHLB) Funding Agreements — 350.0 — 350.0 350.0 Other Liabilities Unfunded Commitments — 3.7 — 3.7 3.7 Total Financial Instrument Liabilities Not Carried at Fair Value $ 1,171.8 $ 2,230.6 $ — $ 3,402.4 $ 3,092.1

Investments (Tables)

Investments (Tables)	12 Months Ended
	Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Amortized Cost and Fair Values of Securities by Security Type	At December 31, 2018 and 2017 , 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, 2018 Amortized Cost Gross Unrealized Gain Gross Unrealized Loss Fair Value (in millions of dollars) United States Government and Government Agencies and Authorities $ 1,702.1 $ 123.2 $ 10.9 $ 1,814.4 States, Municipalities, and Political Subdivisions 2,121.5 307.1 4.4 2,424.2 Foreign Governments 825.8 162.7 4.8 983.7 Public Utilities 6,626.2 850.0 63.4 7,412.8 Mortgage/Asset-Backed Securities 1,523.8 67.2 8.3 1,582.7 All Other Corporate Bonds 27,436.8 1,981.6 664.4 28,754.0 Redeemable Preferred Stocks 39.0 1.1 0.2 39.9 Total Fixed Maturity Securities $ 40,275.2 $ 3,492.9 $ 756.4 $ 43,011.7 December 31, 2017 Amortized Cost Gross Unrealized Gain Gross Unrealized Loss Fair Value (in millions of dollars) United States Government and Government Agencies and Authorities $ 1,311.1 $ 176.1 $ 4.7 $ 1,482.5 States, Municipalities, and Political Subdivisions 1,942.8 395.4 1.3 2,336.9 Foreign Governments 673.0 191.3 0.4 863.9 Public Utilities 6,952.7 1,296.4 12.6 8,236.5 Mortgage/Asset-Backed Securities 1,873.2 105.1 4.7 1,973.6 All Other Corporate Bonds 26,988.7 3,633.5 99.8 30,522.4 Redeemable Preferred Stocks 39.0 3.0 — 42.0 Total Fixed Maturity Securities $ 39,780.5 $ 5,800.8 $ 123.5 $ 45,457.8
Length of Time Fixed Maturity Securities had been in a Gross Unrealized Loss Position	The following charts indicate the length of time our fixed maturity securities have been in a gross unrealized loss position. December 31, 2018 Less Than 12 Months 12 Months or Greater Fair Value Gross Unrealized Loss Fair Value Gross Unrealized Loss (in millions of dollars) United States Government and Government Agencies and Authorities $ 68.8 $ 1.7 $ 212.5 $ 9.2 States, Municipalities, and Political Subdivisions 183.2 2.1 65.0 2.3 Foreign Governments 58.4 3.8 12.0 1.0 Public Utilities 740.1 31.3 325.7 32.1 Mortgage/Asset-Backed Securities 81.5 1.2 201.6 7.1 All Other Corporate Bonds 9,240.2 462.2 1,704.9 202.2 Redeemable Preferred Stocks 18.8 0.2 — — Total Fixed Maturity Securities $ 10,391.0 $ 502.5 $ 2,521.7 $ 253.9 December 31, 2017 Less Than 12 Months 12 Months or Greater Fair Value Gross Unrealized Loss Fair Value Gross Unrealized Loss (in millions of dollars) United States Government and Government Agencies and Authorities $ 157.9 $ 3.0 $ 58.8 $ 1.8 States, Municipalities, and Political Subdivisions 45.7 0.5 22.3 0.7 Foreign Governments 13.2 0.4 — — Public Utilities 213.2 7.9 133.5 4.7 Mortgage/Asset-Backed Securities 252.5 1.4 144.7 3.3 All Other Corporate Bonds 1,355.1 26.8 785.2 73.0 Total Fixed Maturity Securities $ 2,037.6 $ 40.0 $ 1,144.5 $ 83.5
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, 2018 Total Amortized Cost Unrealized Gain Position Unrealized Loss Position Gross Gain Fair Value Gross Loss Fair Value (in millions of dollars) 1 year or less $ 1,073.3 $ 14.5 $ 1,020.1 $ 8.4 $ 59.3 Over 1 year through 5 years 6,267.5 300.6 5,186.9 80.2 1,301.0 Over 5 years through 10 years 12,573.4 795.0 6,812.7 303.9 6,251.8 Over 10 years 18,837.2 2,315.6 15,779.7 355.6 5,017.5 38,751.4 3,425.7 28,799.4 748.1 12,629.6 Mortgage/Asset-Backed Securities 1,523.8 67.2 1,299.6 8.3 283.1 Total Fixed Maturity Securities $ 40,275.2 $ 3,492.9 $ 30,099.0 $ 756.4 $ 12,912.7 December 31, 2017 Total Amortized Cost Unrealized Gain Position Unrealized Loss Position Gross Gain Fair Value Gross Loss Fair Value (in millions of dollars) 1 year or less $ 1,625.1 $ 30.9 $ 1,638.8 $ 3.1 $ 14.1 Over 1 year through 5 years 5,579.9 453.6 5,810.9 18.5 204.1 Over 5 years through 10 years 12,091.1 1,169.8 11,916.5 53.2 1,291.2 Over 10 years 18,611.2 4,041.4 21,333.1 44.0 1,275.5 37,907.3 5,695.7 40,699.3 118.8 2,784.9 Mortgage/Asset-Backed Securities 1,873.2 105.1 1,576.4 4.7 397.2 Total Fixed Maturity Securities $ 39,780.5 $ 5,800.8 $ 42,275.7 $ 123.5 $ 3,182.1
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, 2018 : Gross Unrealized Loss Fair Value Gross Unrealized Gain Amount Percent of Total Gross Unrealized Loss (in millions of dollars) Investment-Grade $ 39,973.1 $ 3,464.2 $ 529.5 70.0 % Below-Investment-Grade 3,038.6 28.7 226.9 30.0 Total Fixed Maturity Securities $ 43,011.7 $ 3,492.9 $ 756.4 100.0 %
Low Income Housing Tax Credits	The Company invests in tax credit partnerships primarily for the receipt of income tax credits and tax benefits derived from passive losses on the investments. Amounts recognized in the consolidated statements of income are as follows: Year Ended December 31 2018 2017 2016 (in millions of dollars) Income Tax Credits $ 41.4 $ 41.8 $ 41.8 Amortization, Net of Tax (28.1 ) (23.2 ) (23.2 ) Income Tax Benefit $ 13.3 $ 18.6 $ 18.6
Mortgage Loans by Property Type and Geographic Region	Mortgage loans by property type and geographic region are presented below. December 31 2018 2017 (in millions of dollars) Carrying Percent of Carrying Percent of Amount Total Amount Total Property Type Apartment $ 491.0 21.4 % $ 360.0 16.3 % Industrial 635.6 27.7 601.2 27.2 Office 604.2 26.3 692.3 31.3 Retail 519.5 22.6 527.6 23.8 Other 44.7 2.0 32.1 1.4 Total $ 2,295.0 100.0 % $ 2,213.2 100.0 % Region New England $ 45.9 2.0 % $ 56.1 2.5 % Mid-Atlantic 160.6 7.0 155.5 7.0 East North Central 354.4 15.4 282.0 12.8 West North Central 190.3 8.3 210.1 9.5 South Atlantic 485.2 21.1 494.4 22.3 East South Central 105.5 4.6 88.8 4.0 West South Central 240.6 10.5 247.4 11.2 Mountain 242.7 10.6 251.2 11.4 Pacific 469.8 20.5 427.7 19.3 Total $ 2,295.0 100.0 % $ 2,213.2 100.0 %
Mortgage Loans by Credit Quality Indicators	Mortgage loans, sorted by the applicable credit quality indicators, are as follows: December 31 2018 2017 (in millions of dollars) Internal Rating Aa $ — $ 0.4 A 477.5 445.7 Baa 1,814.1 1,753.0 Ba 3.4 14.1 Total $ 2,295.0 $ 2,213.2 Loan-to-Value Ratio <= 65% $ 1,204.8 $ 1,101.7 > 65% <= 75% 1,049.1 1,041.6 > 75% <= 85% 11.8 49.3 > 85% 29.3 20.6 Total $ 2,295.0 $ 2,213.2
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 2018 2017 Overnight and Continuous (in millions of dollars) United States Government and Government Agencies and Authorities $ — $ 0.2 Public Utilities — 0.5 All Other Corporate Bonds 0.1 29.8 Total Borrowings 0.1 30.5 Gross Amount of Recognized Liability for Securities Lending Transactions 0.1 30.5 Amounts Related to Agreements Not Included in Offsetting Disclosure Contained Herein $ — $ —
Federal Home Loan Bank Common Stock Carrying Amounts, Amounts Posted, and Advances Received [Table Text Block]	The carrying value of common stock owned, collateral posted, and advances received are as follows: December 31, 2018 December 31, 2017 (in millions of dollars) Carrying Value of FHLB Common Stock $ 24.1 $ 34.1 Advances from FHLB $ 104.0 $ 350.0 Carrying Value of Collateral Posted to FHLB Fixed Maturity Securities $ 219.8 $ 213.3 Commercial Mortgage Loans 179.9 331.5 Total Carrying Value of Collateral Posted to FHLB $ 399.7 $ 544.8
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, 2018 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 $ 30.9 $ — $ 30.9 $ (6.9 ) $ (24.0 ) $ — Securities Lending 164.1 — 164.1 (164.0 ) (0.1 ) — Total $ 195.0 $ — $ 195.0 $ (170.9 ) $ (24.1 ) $ — Financial Liabilities: Derivatives $ 38.0 $ — $ 38.0 $ (33.2 ) $ — $ 4.8 Securities Lending 0.1 — 0.1 (0.1 ) — — Total $ 38.1 $ — $ 38.1 $ (33.3 ) $ — $ 4.8 December 31, 2017 Gross Amount Gross Amount Not of Recognized Gross Amount Net Amount Offset in Balance Sheet Financial Offset in Presented in Financial Cash Net Instruments Balance Sheet Balance Sheet Instruments Collateral Amount (in millions of dollars) Financial Assets: Derivatives $ 19.5 $ — $ 19.5 $ (4.2 ) $ (15.3 ) $ — Securities Lending 159.2 — 159.2 (128.7 ) (30.5 ) — Total $ 178.7 $ — $ 178.7 $ (132.9 ) $ (45.8 ) $ — Financial Liabilities: Derivatives $ 52.2 $ — $ 52.2 $ (42.9 ) $ — $ 9.3 Securities Lending 30.5 — 30.5 (30.5 ) — — Total $ 82.7 $ — $ 82.7 $ (73.4 ) $ — $ 9.3
Net Investment Income	Net Investment Income Net investment income reported in our consolidated statements of income is as follows: Year Ended December 31 2018 2017 2016 (in millions of dollars) Fixed Maturity Securities $ 2,239.7 $ 2,271.8 $ 2,293.9 Derivatives 66.1 56.4 49.8 Mortgage Loans 110.1 104.2 114.0 Policy Loans 18.6 17.9 17.3 Other Long-term Investments Equity Securities 1 (0.2 ) 1.5 1.2 Private Equity Partnerships 2 36.0 25.5 11.4 Other 8.4 10.0 10.0 Short-term Investments 23.7 11.3 7.5 Gross Investment Income 2,502.4 2,498.6 2,505.1 Less Investment Expenses 35.2 32.8 31.9 Less Investment Income on Participation Fund Account Assets 13.5 14.1 14.2 Net Investment Income $ 2,453.7 $ 2,451.7 $ 2,459.0 1 The net unrealized loss recognized in net investment income for the year ended December 31, 2018 related to equity securities still held at December 31, 2018 was $3.9 million . 2 The net unrealized gain recognized in net investment income for the year ended December 31, 2018 related to private equity partnerships still held at December 31, 2018 was $7.1 million .
Realized Investment Gains and Losses Reported in Consolidated Statements of Income	Realized Investment Gain and Loss Realized investment gains and losses are as follows: Year Ended December 31 2018 2017 2016 (in millions of dollars) Fixed Maturity Securities Gross Gains on Sales $ 9.7 $ 13.8 $ 34.3 Gross Losses on Sales (15.2 ) (4.4 ) (17.2 ) Other-Than-Temporary Impairment Loss (17.5 ) (8.1 ) (30.5 ) Mortgage Loans and Other Invested Assets Gross Gains on Sales 0.5 9.4 5.5 Gross Losses on Sales — (0.2 ) (0.7 ) Impairment Loss (1.4 ) (0.9 ) (5.7 ) Embedded Derivative in Modified Coinsurance Arrangement (15.2 ) 30.8 40.9 All Other Derivatives 0.3 (0.1 ) (1.5 ) Foreign Currency Transactions (0.7 ) — (0.9 ) Net Realized Investment Gain (Loss) $ (39.5 ) $ 40.3 $ 24.2

Derivative Financial Instrume_2

Derivative Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2018
Notes to Financial Statements [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, 2018 December 31, 2017 (in millions of dollars) Carrying Value of Collateral Received from Counterparties Cash $ 24.0 $ 15.7 Carrying Value of Collateral Posted to Counterparties Fixed Maturity Securities $ 33.4 $ 46.4
Notional Amounts for Each Category of Derivative Activity	The table below summarizes, by notional amounts, the activity for each category of derivatives. The notional amounts represent the basis upon which our counterparty pay and receive amounts are calculated. Swaps Receive Variable/Pay Fixed Receive Fixed/Pay Fixed Receive Fixed/Pay Variable Credit Default Forwards Total (in millions of dollars) Balance at December 31, 2015 $ 150.0 $ 650.3 $ 600.0 $ 70.0 $ — $ 1,470.3 Additions 3.5 — — — 30.0 33.5 Terminations 48.0 33.8 350.0 — 20.0 451.8 Balance at December 31, 2016 105.5 616.5 250.0 70.0 10.0 1,052.0 Additions — 26.4 — — 65.7 92.1 Terminations 57.5 106.4 — — 75.7 239.6 Balance at December 31, 2017 48.0 536.5 250.0 70.0 — 904.5 Additions — 78.1 — 11.0 47.4 136.5 Terminations 48.0 76.4 — 70.0 47.4 241.8 Balance at December 31, 2018 $ — $ 538.2 $ 250.0 $ 11.0 $ — $ 799.2
Fair Value Hedges Carrying Amount of Hedged Assets and Liabilities and Cumulative Basis Adjustments	The following table summarizes the carrying amount of hedged assets and liabilities and the related cumulative basis adjustments related to our fair value hedges: Carrying Amount of Hedged Assets (Liabilities) Cumulative Amount of Fair Value Hedging Adjustment Included in the Carrying Amount of the Hedged Assets (Liabilities) December 31, 2018 December 31, 2017 December 31, 2018 December 31, 2017 (in millions of dollars) Fixed maturity securities: Receive variable interest rate, pay fixed interest rate $ — $ 48.5 $ — $ 0.6 Receive fixed functional currency interest, pay fixed foreign currency interest $ 56.2 $ — $ (2.7 ) $ — Long-term Debt $ (244.4 ) $ (244.8 ) $ 5.1 $ 4.5
Location and Fair Values of Derivative Financial Instruments	The following tables summarize the location and fair values of derivative financial instruments, as reported in our consolidated balance sheets. December 31, 2018 Derivative Assets Derivative Liabilities Balance Sheet Location Fair Value Balance Sheet Location Fair Value (in millions of dollars) Designated as Hedging Instruments Cash Flow Hedges Foreign Exchange Contracts Other L-T Investments $ 25.0 Other Liabilities $ 7.9 Fair Value Hedges Interest Rate Swaps Other L-T Investments — Other Liabilities 5.2 Foreign Exchange Contracts Other L-T Investments 5.4 Other Liabilities 0.4 Total Fair Value Hedges 5.4 5.6 Total Designated as Hedging Instruments $ 30.4 $ 13.5 Not Designated as Hedging Instruments Credit Default Swaps Other L-T Investments $ 0.5 Other Liabilities $ — Foreign Exchange Contracts Other L-T Investments — Other Liabilities 24.5 Embedded Derivative in Modified Coinsurance Arrangement Other L-T Investments — Other Liabilities 31.1 Total Not Designated as Hedging Instruments $ 0.5 $ 55.6 December 31, 2017 Derivative Assets Derivative Liabilities Balance Sheet Location Fair Value Balance Sheet Location Fair Value (in millions of dollars) Designated as Hedging Instruments Cash Flow Hedges Foreign Exchange Contracts Other L-T Investments $ 19.5 Other Liabilities $ 19.4 Fair Value Hedges Interest Rate Swaps Other L-T Investments — Other Liabilities 5.1 Total Designated as Hedging Instruments $ 19.5 $ 24.5 Not Designated as Hedging Instruments Credit Default Swaps Other Liabilities $ 0.2 Foreign Exchange Contracts Other Liabilities 27.5 Embedded Derivative in Modified Coinsurance Arrangement Other Liabilities 15.9 Total Not Designated as Hedging Instruments $ 43.6
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, 2018 Net Investment Income Net Realized Investment Gain (Loss) Interest and Debt Expense (in millions of dollars) Total Income and Expense Presented in the Consolidated Statements of Income of Which Hedged Items are Recorded $ 2,453.7 $ (39.5 ) $ 167.3 Gain (Loss) on Cash Flow Hedging Relationships Interest Rate Swaps: Hedged items 310.3 0.1 38.4 Derivatives Designated as Hedging Instruments 67.1 (0.3 ) 2.3 Foreign Exchange Contracts: Hedged items 18.1 1.5 — Derivatives Designated as Hedging Instruments (0.9 ) (1.5 ) — Gain (Loss) on Fair Value Hedging Relationships Interest Rate Swaps: Hedged items 1.0 0.1 14.3 Derivatives Designated as Hedging Instruments (0.5 ) (0.1 ) 1.8 Foreign Exchange Contracts Hedged items 0.6 (2.7 ) — Derivatives Designated as Hedging Instruments 0.5 2.7 — Year Ended December 31, 2017 Net Investment Income Net Realized Investment Gain (Loss) Interest and Debt Expense (in millions of dollars) Total Income and Expense Presented in the Consolidated Statements of Income of Which Hedged Items are Recorded $ 2,451.7 $ 40.3 $ 159.9 Gain (Loss) on Cash Flow Hedging Relationships Interest Rate Swaps: Hedged items 321.1 2.5 44.9 Derivatives Designated as Hedging Instruments 60.4 0.2 2.2 Foreign Exchange Contracts: Hedged items 21.7 8.9 — Derivatives Designated as Hedging Instruments (1.2 ) (9.2 ) — Gain (Loss) on Fair Value Hedging Relationships Interest Rate Swaps: Hedged items 4.8 (1.7 ) 14.3 Derivatives Designated as Hedging Instruments (3.2 ) 1.7 (0.6 ) Year Ended December 31, 2016 Net Investment Income Net Realized Investment Gain (Loss) Interest and Debt Expense (in millions of dollars) Total Income and Expense Presented in the Consolidated Statements of Income of Which Hedged Items are Recorded $ 2,459.0 $ 24.2 $ 166.0 Gain (Loss) on Cash Flow Hedging Relationships Interest Rate Swaps: Hedged items 337.7 7.2 44.9 Derivatives Designated as Hedging Instruments 55.7 3.4 2.1 Foreign Exchange Contracts: Hedged items 23.1 1.5 — Derivatives Designated as Hedging Instruments (0.6 ) (1.4 ) — Gain (Loss) on Fair Value Hedging Relationships Interest Rate Swaps: Hedged items 7.1 (3.1 ) 39.7 Derivatives Designated as Hedging Instruments (5.3 ) 3.1 (4.7 )
Schedule of Cash Flow Hedges Included in Accumulated Other Comprehensive Income (Loss)	The following table summarizes the location of gains and losses of derivative financial instruments designated as cash flow hedging instruments, as reported in our consolidated statements of comprehensive income (loss). Year Ended December 31 2018 2017 2016 (in millions of dollars) Gain (Loss) Recognized in Other Comprehensive Income (Loss) on Derivatives Interest Rate Swaps and Forwards $ (0.1 ) $ (0.1 ) $ (0.1 ) Foreign Exchange Contracts 16.9 (23.0 ) (22.2 ) Total $ 16.8 $ (23.1 ) $ (22.3 )
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 2018 2017 2016 (in millions of dollars) Net Realized Investment Gain (Loss) Credit Default Swaps $ (0.3 ) $ (0.4 ) $ (0.9 ) Interest Rate Swaps (0.3 ) (0.1 ) 0.4 Foreign Exchange Contracts 0.9 0.4 0.2 Embedded Derivative in Modified Coinsurance Arrangement (15.2 ) 30.8 40.9 Total $ (14.9 ) $ 30.7 $ 40.6

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Income (Tables)	12 Months Ended
	Dec. 31, 2018
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss)	Components of our accumulated other comprehensive income (loss), after tax, and related changes are as follows: Net Unrealized Gain (Loss) on Securities Net Gain on Hedges Foreign Currency Translation Adjustment Unrecognized Pension and Postretirement Benefit Costs Total (in millions of dollars) Balance at December 31, 2015 $ 204.3 $ 378.0 $ (173.6 ) $ (392.6 ) $ 16.1 Other Comprehensive Income (Loss) Before Reclassifications 226.5 (15.8 ) (180.4 ) (82.8 ) (52.5 ) Amounts Reclassified from Accumulated Other Comprehensive Income or Loss 9.8 (34.7 ) — 10.3 (14.6 ) Net Other Comprehensive Income (Loss) 236.3 (50.5 ) (180.4 ) (72.5 ) (67.1 ) Balance at December 31, 2016 440.6 327.5 (354.0 ) (465.1 ) (51.0 ) Other Comprehensive Income (Loss) Before Reclassifications 176.7 (14.7 ) 99.5 (55.9 ) 205.6 Amounts Reclassified from Accumulated Other Comprehensive Income or Loss (9.5 ) (30.5 ) — 12.9 (27.1 ) Net Other Comprehensive Income (Loss) 167.2 (45.2 ) 99.5 (43.0 ) 178.5 Balance at December 31, 2017 607.8 282.3 (254.5 ) (508.1 ) 127.5 Adjustment to Adopt Accounting Standard Update - Note 1 (17.5 ) — — — (17.5 ) Other Comprehensive Income (Loss) Before Reclassifications (920.3 ) 16.8 (50.7 ) 43.6 (910.6 ) Amounts Reclassified from Accumulated Other Comprehensive Income or Loss 17.6 (48.5 ) — 17.3 (13.6 ) Net Other Comprehensive Income (Loss) (902.7 ) (31.7 ) (50.7 ) 60.9 (924.2 ) Balance at December 31, 2018 $ (312.4 ) $ 250.6 $ (305.2 ) $ (447.2 ) $ (814.2 )
Schedule of Components of Unrealized Gain on Securities	The net unrealized gain (loss) on securities consists of the following components: December 31 January 1 December 31 Change for the Year Ended December 31 2018 2017 2016 2015 2018 2017 2016 (in millions of dollars) Fixed Maturity Securities $ 2,736.5 $ 5,665.2 $ 5,677.3 $ 4,664.6 $ 3,695.7 $ (2,928.7 ) $ 1,012.7 $ 968.9 Other Investments — — 14.4 (22.7 ) (33.7 ) — 37.1 11.0 Deferred Acquisition Costs (27.9 ) (51.4 ) (51.4 ) (38.9 ) (29.4 ) 23.5 (12.5 ) (9.5 ) Reserves for Future Policy and Contract Benefits (3,220.3 ) (5,094.7 ) (5,094.7 ) (4,253.2 ) (3,578.4 ) 1,874.4 (841.5 ) (674.8 ) Reinsurance Recoverable 261.4 375.8 375.8 321.3 263.2 (114.4 ) 54.5 58.1 Income Tax (62.1 ) (304.6 ) (313.6 ) (230.5 ) (113.1 ) 242.5 (83.1 ) (117.4 ) Total $ (312.4 ) $ 590.3 $ 607.8 $ 440.6 $ 204.3 $ (902.7 ) $ 167.2 $ 236.3
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 2018 2017 2016 (in millions of dollars) Net Unrealized Gain (Loss) on Securities Net Realized Investment Gain (Loss) Gain (Loss) on Sales of Securities and Other Invested Assets $ (4.8 ) $ 22.7 $ 15.3 Other-Than-Temporary Impairment Loss (17.5 ) (8.1 ) (30.5 ) (22.3 ) 14.6 (15.2 ) Income Tax Expense (Benefit) (4.7 ) 5.1 (5.4 ) Total $ (17.6 ) $ 9.5 $ (9.8 ) Net Gain on Hedges Net Investment Income Gain on Interest Rate Swaps and Forwards $ 65.9 $ 59.0 $ 54.5 Loss on Foreign Exchange Contracts (1.1 ) (1.2 ) (1.1 ) Net Realized Investment Gain (Loss) Gain on Interest Rate Swaps 0.2 0.2 3.2 Loss on Foreign Exchange Contracts (1.5 ) (9.2 ) (1.4 ) Interest and Debt Expense Loss on Interest Rate Swaps (2.1 ) (2.0 ) (1.9 ) 61.4 46.8 53.3 Income Tax Expense 12.9 16.3 18.6 Total $ 48.5 $ 30.5 $ 34.7 Unrecognized Pension and Postretirement Benefit Costs Other Expenses Amortization of Net Actuarial Loss $ (22.3 ) $ (20.3 ) $ (16.3 ) Amortization of Prior Service Credit 0.2 0.7 0.5 (22.1 ) (19.6 ) (15.8 ) Income Tax Benefit (4.8 ) (6.7 ) (5.5 ) Total $ (17.3 ) $ (12.9 ) $ (10.3 )

Liability for Unpaid Claims (Ta

Liability for Unpaid Claims (Tables)	12 Months Ended
	Dec. 31, 2018
Insurance [Abstract]
Schedule of Liability for Unpaid Claims and Claims Adjustment Expense	Changes in the liability for unpaid claims and claim adjustment expenses are as follows: 2018 2017 2016 (in millions of dollars) Balance at January 1 $ 23,222.0 $ 23,249.5 $ 23,796.1 Less Reinsurance Recoverable 2,182.0 2,163.6 2,064.6 Net Balance at January 1 21,040.0 21,085.9 21,731.5 Incurred Related to Current Year 5,832.3 5,422.9 5,243.0 Prior Years Interest 1,049.8 1,089.7 1,136.7 All Other Incurred (106.2 ) (158.2 ) (198.3 ) Foreign Currency (110.7 ) 167.5 (340.2 ) Total Incurred 6,665.2 6,521.9 5,841.2 Paid Related to Current Year (2,354.7 ) (2,156.9 ) (2,035.4 ) Prior Years (4,428.8 ) (4,410.9 ) (4,451.4 ) Total Paid (6,783.5 ) (6,567.8 ) (6,486.8 ) Net Balance at December 31 20,921.7 21,040.0 21,085.9 Plus Reinsurance Recoverable 2,227.3 2,182.0 2,163.6 Balance at December 31 $ 23,149.0 $ 23,222.0 $ 23,249.5
Reconciliation of Policy and Contract Benefits and Reserves for Future Policy and Contract Benefits to Balance Sheet Amounts	A reconciliation of policy and contract benefits and reserves for future policy and contract benefits as reported in our consolidated balance sheets to the liability for unpaid claims and claim adjustment expenses is as follows: December 31 2018 2017 2016 (in millions of dollars) Policy and Contract Benefits $ 1,695.7 $ 1,605.2 $ 1,507.9 Reserves for Future Policy and Contract Benefits 44,841.9 45,601.6 44,245.9 Total 46,537.6 47,206.8 45,753.8 Less: Life Reserves for Future Policy and Contract Benefits 8,330.9 8,231.3 8,078.2 Accident and Health Active Life Reserves 11,837.4 10,658.8 10,172.9 Adjustment Related to Unrealized Investment Gains and Losses 3,220.3 5,094.7 4,253.2 Liability for Unpaid Claims and Claim Adjustment Expenses $ 23,149.0 $ 23,222.0 $ 23,249.5 The adjustment related to unrealized investment gains and losses reflects the changes that would be necessary to policyholder liabilities if the unrealized investment gains and losses related to the corresponding available-for-sale securities had been realized. Changes in this adjustment are reported as a component of other comprehensive income or loss.

Income Tax (Tables)

Income Tax (Tables)	12 Months Ended
	Dec. 31, 2018
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 2018 2017 2016 (in millions of dollars) Net Income $ 104.4 $ 409.8 $ 416.3 Stockholders' Equity - Additional Paid-in Capital Stock-Based Compensation — — (0.3 ) Stockholders' Equity - Accumulated Other Comprehensive Income (Loss) Change in Net Unrealized Gain on Securities Before Adjustment (614.2 ) 328.1 318.0 Change in Adjustment to Deferred Acquisition Costs and Reserves for Future Policy and Contract Benefits, Net of Reinsurance 371.7 (245.0 ) (200.6 ) Change in Net Gain on Hedges (8.2 ) (24.4 ) (25.4 ) Change in Foreign Currency Translation Adjustment (0.6 ) — — Change in Unrecognized Pension and Postretirement Benefit Costs 17.0 (8.3 ) (34.2 ) Total $ (129.9 ) $ 460.2 $ 473.8
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. Certain prior year amounts have been reclassified to conform to current year reporting. Year Ended December 31 2018 2017 2016 Statutory Income Tax 21.0 % 35.0 % 35.0 % Foreign Rate Differential, Inclusive of Foreign Rate Changes (0.3 ) (1.1 ) (2.2 ) U.S. Deferred Tax Liability Remeasurement — (7.0 ) — Deemed Repatriation Tax on Foreign Earnings and Profit (E&P) 1.8 4.7 — Tax Exempt Income (1.3 ) (0.8 ) (0.8 ) Tax Credits (2.4 ) (1.5 ) (1.6 ) Policyholder Reserves (2.4 ) — — Other Items, Net 0.2 (0.1 ) 0.5 Effective Tax 16.6 % 29.2 % 30.9 %
Schedule of Deferred Tax Assets and Liabilities	Our net deferred tax (asset) liability consists of the following: December 31 2018 2017 (in millions of dollars) Deferred Tax Liability Deferred Acquisition Costs $ 129.7 $ 118.6 Fixed Assets 56.2 52.8 Invested Assets 493.4 1,074.0 Intangible Assets 24.0 6.5 Other 34.1 35.8 Gross Deferred Tax Liability 737.4 1,287.7 Deferred Tax Asset Reserves 668.5 908.0 Employee Benefits 179.5 188.7 Other 17.7 12.3 Gross Deferred Tax Asset 865.7 1,109.0 Less: Valuation Allowance 18.4 20.3 Net Deferred Tax Asset 847.3 1,088.7 Net Deferred Tax (Asset) Liability $ (109.9 ) $ 199.0
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. The federal statutory rates used were 21 percent for 2018 and 35 percent for 2017 and 2016: Year Ended December 31 2018 2017 2016 (in millions of dollars) Income Before Tax Domestic $ 492.6 $ 1,289.0 $ 1,215.8 Foreign 135.2 115.0 131.9 Total $ 627.8 $ 1,404.0 $ 1,347.7 Current Tax Expense (Benefit) Federal $ 194.6 $ 374.9 $ 414.8 State and Local (0.6 ) 0.4 0.3 Foreign 33.4 26.0 (29.4 ) Total 227.4 401.3 385.7 Deferred Tax Expense (Benefit) Federal (114.6 ) 14.2 (14.6 ) State and Local (0.2 ) (0.3 ) (2.1 ) Foreign (8.2 ) (5.4 ) 47.3 Total (123.0 ) 8.5 30.6 Total Tax Expense $ 104.4 $ 409.8 $ 416.3
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. Certain prior year amounts have been reclassified to conform to current year reporting. December 31 2018 2017 2016 (in millions of dollars) Balance at Beginning of Year $ 1.4 $ 1.5 $ 0.8 Additions for Tax Positions Related to Prior Years 261.5 0.3 0.7 Additions for Tax Positions Related to Current Year — — — Settlements with Tax Authorities — — — Lapse of the Applicable Statute of Limitations (0.7 ) (0.4 ) — Balance at End of Year 262.2 1.4 1.5 Less Tax Attributable to Temporary Items Included Above (148.2 ) — — Total Unrecognized Tax Benefits That if Recognized Would Affect the Effective Tax Rate $ 114.0 $ 1.4 $ 1.5

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Schedule of Debt	Debt consists of the following: December 31 2018 2017 Interest Rates Maturities (in millions of dollars) Long-term Debt Outstanding Principal Senior Secured Notes issued 2007 Variable 2037 $ 140.0 $ 200.0 Senior Notes issued 1998 6.750 - 7.250% 2028 365.8 365.8 Senior Notes issued 2002 7.375% 2032 39.5 39.5 Senior Notes issued 2010 5.625% 2020 400.0 400.0 Senior Notes issued 2012 and 2016 5.750% 2042 500.0 500.0 Senior Notes issued 2014 4.000% 2024 350.0 350.0 Senior Notes issued 2015 3.875% 2025 275.0 275.0 Senior Notes issued 2016 3.000% 2021 350.0 350.0 Medium-term Notes issued 1990 - 1996 7.000 - 7.190% 2023 - 2028 50.8 50.8 Junior Subordinated Debt Securities issued 1998 7.405% 2038 226.5 226.5 Junior Subordinated Debt Securities issued 2018 6.250% 2058 300.0 — Fair Value Hedge Adjustment (5.1 ) (4.5 ) Less: Unamortized Net Premium 9.6 9.7 Unamortized Debt Issuance Costs (30.8 ) (24.4 ) Total Long-term Debt 2,971.3 2,738.4 Short-term Debt Outstanding Principal Senior Notes issued 1998 7.000% 2018 — 200.0 Less Unamortized Debt Issuance Costs — (0.1 ) Total Short-term Debt — 199.9 Total Debt $ 2,971.3 $ 2,938.3

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2018
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 2018 2017 2018 2017 2018 2017 (in millions of dollars) Change in Benefit Obligation Benefit Obligation at Beginning of Year $ 2,136.9 $ 1,955.3 $ 243.8 $ 223.0 $ 139.5 $ 147.9 Service Cost 9.1 7.9 — — — — Interest Cost 79.8 84.5 5.9 6.2 4.9 5.9 Plan Participant Contributions — — — — 0.2 0.2 Actuarial (Gain) Loss (210.3 ) 159.3 (18.9 ) 1.7 (7.6 ) (4.2 ) Benefits and Expenses Paid (82.2 ) (77.7 ) (7.3 ) (8.3 ) (11.1 ) (10.3 ) Plan Amendment — 7.6 0.3 — — — Change in Foreign Exchange Rates — — (12.8 ) 21.2 — — Benefit Obligation at End of Year $ 1,933.3 $ 2,136.9 $ 211.0 $ 243.8 $ 125.9 $ 139.5 Accumulated Benefit Obligation at December 31 $ 1,933.3 $ 2,136.9 $ 205.0 $ 234.3 N/A N/A Change in Fair Value of Plan Assets Fair Value of Plan Assets at Beginning of Year $ 1,582.6 $ 1,454.1 $ 253.5 $ 228.4 $ 10.5 $ 10.8 Actual Return on Plan Assets (53.6 ) 198.5 (16.0 ) 11.6 0.1 0.1 Employer Contributions 8.1 7.7 — — 10.4 9.7 Plan Participant Contributions — — — — 0.2 0.2 Benefits and Expenses Paid (82.2 ) (77.7 ) (7.3 ) (8.3 ) (11.1 ) (10.3 ) Change in Foreign Exchange Rates — — (13.2 ) 21.8 — — Fair Value of Plan Assets at End of Year $ 1,454.9 $ 1,582.6 $ 217.0 $ 253.5 $ 10.1 $ 10.5 Underfunded (Overfunded) Status $ 478.4 $ 554.3 $ (6.0 ) $ (9.7 ) $ 115.8 $ 129.0
Schedule of Amounts Recognized in Balance Sheet	The amounts recognized in our consolidated balance sheets for our pension and OPEB plans at December 31, 2018 and 2017 are as follows. Pension Benefits U.S. Plans U.K. Plan OPEB 2018 2017 2018 2017 2018 2017 (in millions of dollars) Current Liability $ 7.3 $ 7.2 $ — $ — $ 1.6 $ 1.2 Noncurrent Liability 471.1 547.1 — — 114.2 127.8 Noncurrent Asset — — (6.0 ) (9.7 ) — — Underfunded (Overfunded) Status $ 478.4 $ 554.3 $ (6.0 ) $ (9.7 ) $ 115.8 $ 129.0 Unrecognized Pension and Postretirement Benefit Costs Net Actuarial Gain (Loss) $ (672.6 ) $ (746.4 ) $ (48.9 ) $ (46.3 ) $ 20.9 $ 13.7 Prior Service Credit (Cost) (0.7 ) (0.7 ) (0.3 ) — 3.3 3.5 (673.3 ) (747.1 ) (49.2 ) (46.3 ) 24.2 17.2 Income Tax 236.0 251.8 11.9 11.6 3.2 4.7 Total Included in Accumulated Other Comprehensive Income (Loss) $ (437.3 ) $ (495.3 ) $ (37.3 ) $ (34.7 ) $ 27.4 $ 21.9
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, 2018 and 2017 . Pension Benefits U.S. Plans U.K. Plan OPEB 2018 2017 2018 2017 2018 2017 (in millions of dollars) Accumulated Other Comprehensive Income (Loss) at Beginning of Year $ (495.3 ) $ (451.3 ) $ (34.7 ) $ (33.1 ) $ 21.9 $ 19.3 Net Actuarial Gain (Loss) Amortization 21.7 19.6 0.6 0.7 — — All Other Changes 52.1 (63.9 ) (3.2 ) (3.0 ) 7.2 3.6 Prior Service Credit (Cost) Amortization — (0.3 ) — — (0.2 ) (0.4 ) Plan Amendment — (7.6 ) (0.3 ) — — — Change in Income Tax (15.8 ) 8.2 0.3 0.7 (1.5 ) (0.6 ) Accumulated Other Comprehensive Income (Loss) at End of Year $ (437.3 ) $ (495.3 ) $ (37.3 ) $ (34.7 ) $ 27.4 $ 21.9
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, 2018 Level 1 Level 2 Level 3 NAV Total (in millions of dollars) Assets Fixed Maturity Securities United States Government and Government Agencies and Authorities $ 513.4 $ 1,301.0 $ — $ — $ 1,814.4 States, Municipalities, and Political Subdivisions — 2,424.2 — — 2,424.2 Foreign Governments — 952.3 31.4 — 983.7 Public Utilities 286.4 7,041.7 84.7 — 7,412.8 Mortgage/Asset-Backed Securities — 1,582.7 — — 1,582.7 All Other Corporate Bonds 4,232.1 23,026.1 1,495.8 — 28,754.0 Redeemable Preferred Stocks — 18.8 21.1 — 39.9 Total Fixed Maturity Securities 5,031.9 36,346.8 1,633.0 — 43,011.7 Other Long-term Investments Derivatives Foreign Exchange Contracts — 30.4 — — 30.4 Credit Default Swaps — 0.5 — — 0.5 Equity Securities — 24.6 4.6 — 29.2 Private Equity Partnerships — — — 483.8 483.8 Total Other Long-term Investments — 55.5 4.6 483.8 543.9 Total Financial Instrument Assets Carried at Fair Value $ 5,031.9 $ 36,402.3 $ 1,637.6 $ 483.8 $ 43,555.6 Liabilities Other Liabilities Derivatives Interest Rate Swaps $ — $ 5.2 $ — $ — $ 5.2 Foreign Exchange Contracts — 32.8 — — 32.8 Embedded Derivative in Modified Coinsurance Arrangement — — 31.1 — 31.1 Total Derivatives — 38.0 31.1 — 69.1 Total Financial Instrument Liabilities Carried at Fair Value $ — $ 38.0 $ 31.1 $ — $ 69.1 December 31, 2017 Level 1 Level 2 Level 3 NAV Total (in millions of dollars) Assets Fixed Maturity Securities United States Government and Government Agencies and Authorities $ 460.1 $ 1,022.4 $ — $ — $ 1,482.5 States, Municipalities, and Political Subdivisions — 2,336.9 — — 2,336.9 Foreign Governments — 863.9 — — 863.9 Public Utilities 154.2 7,874.6 207.7 — 8,236.5 Mortgage/Asset-Backed Securities — 1,973.6 — — 1,973.6 All Other Corporate Bonds 3,556.1 25,816.2 1,150.1 — 30,522.4 Redeemable Preferred Stocks — 19.2 22.8 — 42.0 Total Fixed Maturity Securities 4,170.4 39,906.8 1,380.6 — 45,457.8 Other Long-term Investments Derivatives Foreign Exchange Contracts — 19.5 — — 19.5 Equity Securities 0.2 10.4 1.1 — 11.7 Private Equity Partnerships — — — 407.2 407.2 Total Other Long-term Investments 0.2 29.9 1.1 407.2 438.4 Total Financial Instrument Assets Carried at Fair Value $ 4,170.6 $ 39,936.7 $ 1,381.7 $ 407.2 $ 45,896.2 Liabilities Other Liabilities Derivatives Interest Rate Swaps $ — $ 5.1 $ — $ — $ 5.1 Foreign Exchange Contracts — 46.9 — — 46.9 Credit Default Swaps — 0.2 — — 0.2 Embedded Derivative in Modified Coinsurance Arrangement — — 15.9 — 15.9 Total Derivatives — 52.2 15.9 — 68.1 Total Financial Instrument Liabilities Carried at Fair Value $ — $ 52.2 $ 15.9 $ — $ 68.1
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation	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, 2018 Total Realized and Unrealized Investment Gains (Losses) Included in Fair Value Beginning of Year Earnings Other Comprehensive Income or Loss Purchases Sales Level 3 Transfers Fair Value End of Year Into Out of (in millions of dollars) Fixed Maturity Securities Foreign Governments $ — $ — $ (1.4 ) $ — $ — $ 32.8 $ — $ 31.4 Public Utilities 207.7 — (2.3 ) — — 39.0 (159.7 ) 84.7 All Other Corporate Bonds 1,150.1 5.8 (118.1 ) 95.1 (148.7 ) 968.6 (457.0 ) 1,495.8 Redeemable Preferred Stocks 22.8 — (1.7 ) — — — — 21.1 Total Fixed Maturity Securities 1,380.6 5.8 (123.5 ) 95.1 (148.7 ) 1,040.4 (616.7 ) 1,633.0 Equity Securities 1.1 — — 3.5 — — — 4.6 Embedded Derivative in Modified Coinsurance Arrangement (15.9 ) (15.2 ) — — — — — (31.1 ) Year Ended December 31, 2017 Total Realized and Unrealized Investment Gains (Losses) Included in Fair Value Beginning Earnings Other Comprehensive Income or Loss Purchases Sales Level 3 Transfers Fair Value End of Into Out of (in millions of dollars) Fixed Maturity Securities States, Municipalities, and Political Subdivisions $ 89.5 $ — $ — $ — $ — $ — $ (89.5 ) $ — Public Utilities 265.3 — 0.3 8.0 (4.8 ) 125.2 (186.3 ) 207.7 All Other Corporate Bonds 1,459.7 (0.6 ) 2.8 118.9 (149.2 ) 524.7 (806.2 ) 1,150.1 Redeemable Preferred Stocks 23.2 — (0.4 ) — — — — 22.8 Total Fixed Maturity Securities 1,837.7 (0.6 ) 2.7 126.9 (154.0 ) 649.9 (1,082.0 ) 1,380.6 Equity Securities 1.2 — — — — — (0.1 ) 1.1 Embedded Derivative in Modified Coinsurance Arrangement (46.7 ) 30.8 — — — — — (15.9 ) Realized and unrealized investment gains and losses presented in the preceding tables represent gains and losses only for the time during which the applicable financial instruments were classified as Level 3. The transfers between levels resulted primarily from a change in observability of three inputs used to determine fair values of the securities transferred: (1) transactional data for new issuance and secondary trades, (2) broker/dealer quotes and pricing, primarily related to changes in the level of activity in the market and whether the market was considered orderly, and (3) comparable bond metrics from which to perform an analysis. For fair value measurements of financial instruments that were transferred either into or out of Level 3, we reflect the transfers using the fair value at the beginning of the period. We believe this allows for greater transparency, as all changes in fair value that arise during the reporting period of the transfer are disclosed as a component of our Level 3 reconciliation. Gains (losses) which are included in earnings and are attributable to the change in fair value of assets or liabilities valued using significant unobservable inputs and still held at each year end were $(15.2) million and $30.8 million for the years ended December 31, 2018 and 2017 , respectively. These amounts relate entirely to the change in fair value of an embedded derivative in a modified coinsurance arrangement and are reported as a component of realized investment gains and losses.
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 2018 2017 2018 2017 2018 2017 Benefit Obligations Discount Rate 4.40 % 3.80 % 2.90 % 2.50 % 4.40 % 3.70 % Rate of Compensation Increase N/A N/A 3.70 % 3.70 % N/A N/A Net Periodic Benefit Cost Discount Rate 3.80 % 4.40 % 2.50 % 2.70 % 3.70 % 4.20 % Expected Return on Plan Assets 6.75 % 7.25 % 3.90 % 3.90 % 5.75 % 5.75 % Rate of Compensation Increase N/A N/A 3.70 % 3.80 % N/A N/A
Schedule of Net Benefit Costs	Net Periodic Benefit Cost The following table provides the components of the net periodic benefit cost (credit) for the years ended December 31. Pension Benefits U.S. Plans U.K. Plan OPEB 2018 2017 2016 2018 2017 2016 2018 2017 2016 (in millions of dollars) Service Cost $ 9.1 $ 7.9 $ 7.0 $ — $ — $ — $ — $ — $ — Interest Cost 79.8 84.5 85.2 5.9 6.2 7.0 4.9 5.9 7.2 Expected Return on Plan Assets (104.5 ) (103.1 ) (102.8 ) (8.9 ) (8.8 ) (10.0 ) (0.6 ) (0.6 ) (0.6 ) Amortization of: Net Actuarial Loss 21.7 19.6 16.2 0.6 0.7 0.1 — — — Prior Service Credit — (0.3 ) (0.3 ) — — — (0.2 ) (0.4 ) (0.2 ) Plan Amendment — — — — — — — — 0.9 Total Net Periodic Benefit Cost $ 6.1 $ 8.6 $ 5.3 $ (2.4 ) $ (1.9 ) $ (2.9 ) $ 4.1 $ 4.9 $ 7.3
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 2019 $ 77.1 $ 5.3 $ 12.1 $ 0.2 $ 11.9 2020 80.2 5.3 11.7 0.2 11.5 2021 83.8 5.6 11.2 0.1 11.1 2022 87.2 5.9 10.7 0.2 10.5 2023 90.9 6.4 10.1 0.1 10.0 2024-2028 513.7 39.4 43.7 0.4 43.3
Other Postretirement Benefit Plans
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Values by Fair Value Hierarchy Input Level	The categorization of fair value measurements by input level for the assets in our OPEB plan is as follows: December 31, 2018 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total (in millions of dollars) Assets Life Insurance Contracts $ — $ — $ 10.1 $ 10.1 December 31, 2017 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total (in millions of dollars) Assets Life Insurance Contracts $ — $ — $ 10.5 $ 10.5
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation	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, 2018 and 2017 are as follows: Year Ended December 31, 2018 Beginning of Year Actual Return on Plan Assets Contributions Net Benefits and Expenses Paid End of Year (in millions of dollars) Life Insurance Contracts $ 10.5 $ 0.1 $ 10.6 $ (11.1 ) $ 10.1 Year Ended December 31, 2017 Beginning of Year Actual Return on Plan Assets Contributions Net Benefits and Expenses Paid End of Year (in millions of dollars) Life Insurance Contracts $ 10.8 $ 0.1 $ 9.9 $ (10.3 ) $ 10.5
Domestic Plan | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans
Schedule of Defined Benefit Plans Disclosures [Table Text Block]	The categorization of fair value measurements by input level for the invested assets in our U.S. pension plans is shown below. The carrying values of investment-related receivables and payables approximate fair value due to the short-term nature of the securities and are not included in the following chart. Investments valued using net asset value (NAV) as a practical expedient are not required to be categorized by input level, but these investments are included as follows to reconcile to total invested assets. December 31, 2018 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) NAV as a Practical Total (in millions of dollars) Invested Assets Equity Securities: U.S. Large Cap $ — $ — $ — $ 83.0 $ 83.0 U.S. Small Cap 18.9 — — — 18.9 Global — — — 290.3 290.3 International — — — 24.6 24.6 Emerging Markets — — — 44.1 44.1 Fixed Income Securities: U.S. Government and Agencies 257.4 — — — 257.4 Corporate — 311.2 — — 311.2 State and Municipal Securities — 5.7 — — 5.7 Opportunistic Credits — — — 192.0 192.0 Real Estate — — — 102.8 102.8 Alternative Investments: Private Equity Direct Investments — — — 53.5 53.5 Private Equity Funds of Funds — — — 34.0 34.0 Hedge Funds of Funds — — — 0.1 0.1 Cash Equivalents 39.2 — — — 39.2 Total Invested Assets $ 315.5 $ 316.9 $ — $ 824.4 $ 1,456.8 December 31, 2017 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) NAV as a Practical Total (in millions of dollars) Invested Assets Equity Securities: U.S. Large Cap $ — $ — $ — $ 103.3 $ 103.3 U.S. Small Cap 45.2 — — — 45.2 Global — — — 325.9 325.9 International — — — 35.7 35.7 Emerging Markets — — — 61.5 61.5 Fixed Income Securities: U.S. Government and Agencies 248.5 11.9 — — 260.4 Corporate — 335.5 — — 335.5 State and Municipal Securities — 6.3 — — 6.3 Opportunistic Credits — — — 193.3 193.3 Real Estate — — — 96.1 96.1 Alternative Investments: Private Equity Direct Investments — — — 45.1 45.1 Private Equity Funds of Funds — — — 34.5 34.5 Hedge Funds of Funds — — — 0.2 0.2 Cash Equivalents 32.0 — — — 32.0 Total Invested Assets $ 325.7 $ 353.7 $ — $ 895.6 $ 1,575.0
Foreign Plan | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Values by Fair Value Hierarchy Input Level	The categorization of fair value measurements by input level for the invested assets in our U.K. pension plan is shown below. Investments valued using NAV as a practical expedient are not required to be categorized by input level, but these investments are included as follows to reconcile to total invested assets. December 31, 2018 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) NAV as a Practical Total (in millions of dollars) Plan Assets Diversified Growth Assets $ — $ — $ — $ 133.0 $ 133.0 Fixed Interest and Index-linked Securities 81.3 — — — 81.3 Cash Equivalents 2.7 — — — 2.7 Total Plan Assets $ 84.0 $ — $ — $ 133.0 $ 217.0 December 31, 2017 Quoted Prices Significant Significant NAV as a Practical Total (in millions of dollars) Plan Assets Diversified Growth Assets $ — $ — $ — $ 154.7 $ 154.7 Fixed Interest and Index-linked Securities 98.4 — — — 98.4 Cash Equivalents 0.4 — — — 0.4 Total Plan Assets $ 98.8 $ — $ — $ 154.7 $ 253.5

Stockholders' Equity and Earn_2

Stockholders' Equity and Earnings Per Common Share (Tables)	12 Months Ended
	Dec. 31, 2018
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 2018 2017 2016 (in millions of dollars, except share data) Numerator Net Income $ 523.4 $ 994.2 $ 931.4 Denominator (000s) Weighted Average Common Shares - Basic 219,635.6 226,492.4 235,445.7 Dilution for Assumed Exercises of Stock Options and Nonvested Stock Awards 423.0 842.8 533.5 Weighted Average Common Shares - Assuming Dilution 220,058.6 227,335.2 235,979.2 Net Income Per Common Share Basic $ 2.38 $ 4.39 $ 3.96 Assuming Dilution $ 2.38 $ 4.37 $ 3.95
Treasury Stock Transactions	Our board of directors has authorized the repurchase of Unum Group's common stock under the following repurchase programs: Share Repurchase Program Authorized During May 2018 May 2017 May 2016 (in millions of dollars) Authorized Repurchase Amount $ 750.0 $ 750.0 $ 750.0 Remaining Repurchase Amount at Year End 2018 $ 500.0 $ — $ — The May 2018 share repurchase program has an expiration date of November 24, 2019 . 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 2018 2017 2016 (in millions) Shares Repurchased 8.7 8.2 11.9 Cost of Shares Repurchased (1) $ 350.7 $ 400.4 $ 403.3 (1) Includes commissions of $0.7 million , $0.3 million , and $0.2 million for the years ended December 31, 2018 , 2017 , and 2016 , respectively.

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award
Schedule of Compensation Cost for Share-based Payment Arrangements	Compensation expense for the stock plans, as reported in our consolidated statements of income, is as follows: Year Ended December 31 2018 2017 2016 (in millions of dollars) Performance Share Units $ 6.8 $ 11.5 $ 6.6 Restricted Stock Units 19.0 17.5 14.9 Other 0.5 0.5 0.4 Total Compensation Expense, Before Income Tax $ 26.3 $ 29.5 $ 21.9 Total Compensation Expense, Net of Income Tax $ 20.9 $ 19.5 $ 14.4
Performance Share Units
Share-based Compensation Arrangement by Share-based Payment Award
Activity for PSUs Classified as Equity	Activity for PSUs classified as equity is as follows: Weighted Average Shares Grant Date (000s) Fair Value Outstanding at December 31, 2017 331 $ 37.62 Granted 255 44.19 Vested (301 ) 30.18 Forfeited (2 ) 46.79 Outstanding at December 31, 2018 283 51.33
Valuation Assumptions on PSU Grants	The fair value of PSUs is estimated on the date of initial grant using the Monte-Carlo simulation m odel. Key assumptions used to value PSUs granted during the years shown are as follows: Year Ended December 31 2018 2017 2016 Expected Volatility (based on our and our peer group historical daily stock prices) 24 % 24 % 22 % Expected Life (equals the performance period) 3.0 years 3.0 years 3.0 years Risk Free Interest Rate (based on U.S. Treasury yields at the date of grant) 2.32 % 1.52 % 0.88 %
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award
Activity for Restricted Stock Units	Activity for RSUs classified as equity is as follows: Weighted Average Shares Grant Date (000s) Fair Value Outstanding at December 31, 2017 871 $ 38.75 Granted 496 47.76 Vested (486 ) 37.32 Forfeited (54 ) 44.65 Outstanding at December 31, 2018 827 44.62
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award
Fair Value and Intrinsic Value of Cash Settled Awards and Stock Options	The intrinsic value of options exercised and fair value of options vested are as follows: Year Ended December 31 2018 2017 2016 (in millions of dollars) Total Intrinsic Value of Options Exercised $ 0.7 $ 10.0 $ 3.4 Total Fair Value of Options Vested $ — $ — $ 0.1
Schedule of Stock Option Activity	Stock option activity is summarized as follows: Remaining Intrinsic Shares Weighted Average Contractual Term Value (000s) Exercise Price (in years) (in millions) Outstanding at December 31, 2017 124 $ 23.86 Exercised (19 ) 20.78 Outstanding at December 31, 2018 105 24.41 1.4 $ 0.5 Exercisable at December 31, 2018 105 $ 24.41 1.4 $ 0.5

Reinsurance (Tables)

Reinsurance (Tables)	12 Months Ended
	Dec. 31, 2018
Reinsurance Disclosures [Abstract]
Reinsurance Premiums for Insurance Companies	Reinsurance data is as follows: Year Ended December 31 2018 2017 2016 (in millions of dollars) Direct Premium Income $ 9,171.1 $ 8,677.2 $ 8,385.0 Reinsurance Assumed 142.6 230.0 236.3 Reinsurance Ceded (327.6 ) (310.1 ) (263.6 ) Net Premium Income $ 8,986.1 $ 8,597.1 $ 8,357.7 Ceded Benefits and Change in Reserves for Future Benefits $ 667.2 $ 655.4 $ 648.3

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2018
Segment Reporting [Abstract]
Premium Income by Major Line of Business within Each Segment	Segment information is as follows: Year Ended December 31 2018 2017 2016 (in millions of dollars) Premium Income Unum US Group Disability Group Long-term Disability $ 1,766.2 $ 1,749.6 $ 1,726.6 Group Short-term Disability 706.3 639.8 626.1 Group Life and Accidental Death & Dismemberment Group Life 1,583.7 1,467.5 1,410.0 Accidental Death & Dismemberment 156.3 147.5 140.3 Supplemental and Voluntary Individual Disability 425.4 420.2 480.3 Voluntary Benefits 895.7 849.4 796.5 Dental and Vision 202.8 169.5 61.1 5,736.4 5,443.5 5,240.9 Unum International Group Long-term Disability 358.9 340.3 355.2 Group Life 110.8 103.1 105.7 Supplemental 99.1 69.6 68.4 568.8 513.0 529.3 Colonial Life Accident, Sickness, and Disability 929.3 884.2 830.0 Life 328.4 300.4 273.8 Cancer and Critical Illness 346.1 326.8 313.3 1,603.8 1,511.4 1,417.1 Closed Block Individual Disability 420.8 471.8 521.9 Long-term Care 648.3 648.7 643.9 All Other 8.0 8.7 4.6 1,077.1 1,129.2 1,170.4 Total Premium Income $ 8,986.1 $ 8,597.1 $ 8,357.7
Selected Operating Statement Data by Segment	Unum US Unum International Colonial Life Closed Block Corporate Total (in millions of dollars) Year Ended December 31, 2018 Premium Income $ 5,736.4 $ 568.8 $ 1,603.8 $ 1,077.1 $ — $ 8,986.1 Net Investment Income 778.7 117.2 151.2 1,377.1 29.5 2,453.7 Other Income 118.5 0.4 1.2 75.4 2.7 198.2 Adjusted Operating Revenue $ 6,633.6 $ 686.4 $ 1,756.2 $ 2,529.6 $ 32.2 $ 11,638.0 Adjusted Operating Income (Loss) $ 1,014.6 $ 113.9 $ 335.2 $ 125.5 $ (171.1 ) $ 1,418.1 Interest and Debt Expense $ — $ — $ — $ 6.9 $ 160.4 $ 167.3 Depreciation and Amortization $ 389.6 $ 17.6 $ 257.3 $ 8.3 $ 1.0 $ 673.8 Year Ended December 31, 2017 Premium Income $ 5,443.5 $ 513.0 $ 1,511.4 $ 1,129.2 $ — $ 8,597.1 Net Investment Income 811.2 120.2 144.9 1,354.0 21.4 2,451.7 Other Income 113.2 0.7 1.1 79.8 2.9 197.7 Adjusted Operating Revenue $ 6,367.9 $ 633.9 $ 1,657.4 $ 2,563.0 $ 24.3 $ 11,246.5 Adjusted Operating Income (Loss) $ 1,009.5 $ 111.7 $ 325.0 $ 123.9 $ (146.8 ) $ 1,423.3 Interest and Debt Expense $ — $ — $ — $ 6.7 $ 153.2 $ 159.9 Depreciation and Amortization $ 371.3 $ 17.3 $ 239.9 $ 6.7 $ 0.9 $ 636.1 Year Ended December 31, 2016 Premium Income $ 5,240.9 $ 529.3 $ 1,417.1 $ 1,170.4 $ — $ 8,357.7 Net Investment Income 828.7 118.1 141.5 1,352.2 18.5 2,459.0 Other Income 113.3 0.2 1.2 86.0 4.9 205.6 Adjusted Operating Revenue $ 6,182.9 $ 647.6 $ 1,559.8 $ 2,608.6 $ 23.4 $ 11,022.3 Adjusted Operating Income (Loss) $ 914.2 $ 128.6 $ 314.2 $ 129.5 $ (163.0 ) $ 1,323.5 Interest and Debt Expense $ — $ — $ — $ 6.9 $ 159.1 $ 166.0 Depreciation and Amortization $ 353.0 $ 16.4 $ 222.9 $ 6.9 $ 1.0 $ 600.2
Deferred Policy Acquisition Costs by Segment	Unum Colonial Unum US International Life Total (in millions of dollars) Deferred Acquisition Costs Year Ended December 31, 2018 Beginning of Year $ 1,205.4 $ 21.3 $ 957.9 $ 2,184.6 Capitalization 344.0 8.1 315.9 668.0 Amortization (315.1 ) (8.2 ) (242.2 ) (565.5 ) Adjustment Related to Unrealized Investment Gains and Losses 5.1 — 18.4 23.5 Foreign Currency — (1.2 ) — (1.2 ) End of Year $ 1,239.4 $ 20.0 $ 1,050.0 $ 2,309.4 Year Ended December 31, 2017 Beginning of Year $ 1,176.5 $ 21.4 $ 896.3 $ 2,094.2 Capitalization 325.5 7.0 295.5 628.0 Amortization (293.6 ) (9.1 ) (224.4 ) (527.1 ) Adjustment Related to Unrealized Investment Gains and Losses (3.0 ) — (9.5 ) (12.5 ) Foreign Currency — 2.0 — 2.0 End of Year $ 1,205.4 $ 21.3 $ 957.9 $ 2,184.6 Year Ended December 31, 2016 Beginning of Year $ 1,136.4 $ 27.1 $ 845.0 $ 2,008.5 Capitalization 314.1 8.2 270.1 592.4 Amortization (275.2 ) (9.7 ) (208.1 ) (493.0 ) Adjustment Related to Unrealized Investment Gains and Losses 1.2 — (10.7 ) (9.5 ) Foreign Currency — (4.2 ) — (4.2 ) End of Year $ 1,176.5 $ 21.4 $ 896.3 $ 2,094.2
Assets by Segment	December 31 2018 2017 (in millions of dollars) Assets Unum US $ 17,510.9 $ 18,109.1 Unum International 3,426.8 3,428.1 Colonial Life 4,237.9 4,184.1 Closed Block 34,527.6 35,051.2 Corporate 2,172.4 3,240.6 Total Assets $ 61,875.6 $ 64,013.1
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 2018 2017 2016 (in millions of dollars) Total Revenue $ 11,598.5 $ 11,286.8 $ 11,046.5 Excluding: Net Realized Investment Gain (Loss) (39.5 ) 40.3 24.2 Adjusted Operating Revenue $ 11,638.0 $ 11,246.5 $ 11,022.3 Income Before Income Tax $ 627.8 $ 1,404.0 $ 1,347.7 Excluding: Net Realized Investment Gain (Loss) (39.5 ) 40.3 24.2 Loss from Guaranty Fund Assessment — (20.6 ) — Unclaimed Death Benefit Reserve Increase — (39.0 ) — Long-term Care Reserve Increase (750.8 ) — — Adjusted Operating Income $ 1,418.1 $ 1,423.3 $ 1,323.5

Statutory Financial Informati_2

Statutory Financial Information (Tables)	12 Months Ended
	Dec. 31, 2018
Statutory Financial Information [Abstract]
Statutory Earnings and Surplus	The operating results and capital and surplus of our traditional U.S. life insurance subsidiaries and our captive reinsurers, prepared in accordance with prescribed or permitted accounting practices of the NAIC or states of domicile, are presented separately below. Year Ended December 31 2018 2017 2016 (in millions of dollars) Combined Net Income (Loss) Traditional U.S. Life Insurance Subsidiaries $ 953.0 $ 807.4 $ 855.1 Captive Reinsurers $ (109.6 ) $ (137.1 ) $ 48.4 Combined Net Gain (Loss) from Operations Traditional U.S. Life Insurance Subsidiaries $ 959.8 $ 812.4 $ 884.6 Captive Reinsurers $ (110.9 ) $ (143.1 ) $ 50.6 December 31 2018 2017 (in millions of dollars) Combined Capital and Surplus Traditional U.S. Life Insurance Subsidiaries $ 3,572.7 $ 3,448.3 Captive Reinsurers $ 1,766.2 $ 1,606.9

Unaudited Quarterly Results (Ta

Unaudited Quarterly Results (Tables)	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Financial Information	The following is a summary of our unaudited quarterly results of operations for 2018 and 2017 : 2018 4 th 3 rd 2 nd 1 st (in millions of dollars, except share data) Premium Income $ 2,263.3 $ 2,251.8 $ 2,221.0 $ 2,250.0 Net Investment Income 608.6 619.2 623.6 602.3 Net Realized Investment Gain (Loss) (41.4 ) 6.7 (2.6 ) (2.2 ) Total Revenue 2,880.8 2,927.8 2,890.3 2,899.6 Income (Loss) Before Income Tax 309.7 (377.8 ) 354.8 341.1 Net Income (Loss) 249.1 (284.7 ) 285.5 273.5 Net Income (Loss) Per Common Share Basic 1.15 (1.30 ) 1.29 1.23 Assuming Dilution 1.15 (1.30 ) 1.29 1.23 2017 4 th 3 rd 2 nd 1 st (in millions of dollars, except share data) Premium Income $ 2,158.4 $ 2,153.6 $ 2,142.2 $ 2,142.9 Net Investment Income 619.8 609.0 620.5 602.4 Net Realized Investment Gain 11.4 9.8 8.1 11.0 Total Revenue 2,839.2 2,819.1 2,822.0 2,806.5 Income Before Income Tax 345.3 366.8 361.6 330.3 Net Income 266.9 252.3 245.1 229.9 Net Income Per Common Share Basic 1.19 1.12 1.08 1.00 Assuming Dilution 1.19 1.12 1.07 1.00 Items affecting the comparability of our financial results are as follows: • Third quarter of 2018 reserve increase of $750.8 million before tax and $593.1 million after tax related to long-term care. • Fourth quarter of 2017 reserve increase of $39.0 million before tax and $25.4 million after tax related to unclaimed death benefits. • Fourth quarter of 2017 net tax benefit of $31.5 million related to the TCJA. • First quarter of 2017 loss from a guaranty fund assessment related to an unaffiliated insurer that was declared insolvent of $20.6 million before tax and $13.4 million after tax.

Schedule II Condensed Financial

Schedule II Condensed Financial Information of Registrant (Tables)	12 Months Ended
	Dec. 31, 2018
Condensed Financial Statements, Captions
Schedule of Debt Instruments Parent Company Only	Debt consists of the following: December 31 2018 2017 Interest Rates Maturities (in millions of dollars) Long-term Debt Outstanding Principal Senior Secured Notes issued 2007 Variable 2037 $ 140.0 $ 200.0 Senior Notes issued 1998 6.750 - 7.250% 2028 365.8 365.8 Senior Notes issued 2002 7.375% 2032 39.5 39.5 Senior Notes issued 2010 5.625% 2020 400.0 400.0 Senior Notes issued 2012 and 2016 5.750% 2042 500.0 500.0 Senior Notes issued 2014 4.000% 2024 350.0 350.0 Senior Notes issued 2015 3.875% 2025 275.0 275.0 Senior Notes issued 2016 3.000% 2021 350.0 350.0 Medium-term Notes issued 1990 - 1996 7.000 - 7.190% 2023 - 2028 50.8 50.8 Junior Subordinated Debt Securities issued 1998 7.405% 2038 226.5 226.5 Junior Subordinated Debt Securities issued 2018 6.250% 2058 300.0 — Fair Value Hedge Adjustment (5.1 ) (4.5 ) Less: Unamortized Net Premium 9.6 9.7 Unamortized Debt Issuance Costs (30.8 ) (24.4 ) Total Long-term Debt 2,971.3 2,738.4 Short-term Debt Outstanding Principal Senior Notes issued 1998 7.000% 2018 — 200.0 Less Unamortized Debt Issuance Costs — (0.1 ) Total Short-term Debt — 199.9 Total Debt $ 2,971.3 $ 2,938.3
Parent Company
Condensed Financial Statements, Captions
Condensed Financial Information of Parent Company Only Balance Sheets	BALANCE SHEETS December 31 2018 2017 (in millions of dollars) Assets Fixed Maturity Securities - at fair value (amortized cost: $139.0; $153.9) $ 135.9 $ 154.1 Other Long-term Investments 38.8 16.8 Short-term Investments 285.2 477.8 Investment in Subsidiaries 11,383.6 12,157.1 Deferred Income Tax 116.7 121.5 Other Assets 446.9 455.4 Total Assets $ 12,407.1 $ 13,382.7 Liabilities and Stockholders' Equity Liabilities Short-term Debt $ — $ 199.9 Long-term Debt 2,831.3 2,538.4 Pension and Postretirement Benefits 594.2 683.3 Other Liabilities 359.8 386.2 Total Liabilities 3,785.3 3,807.8 Stockholders' Equity Common Stock 30.5 30.5 Additional Paid-in Capital 2,321.7 2,303.3 Accumulated Other Comprehensive Income (Loss) (814.2 ) 127.5 Retained Earnings 9,863.1 9,542.2 Treasury Stock (2,779.3 ) (2,428.6 ) Total Stockholders' Equity 8,621.8 9,574.9 Total Liabilities and Stockholders' Equity $ 12,407.1 $ 13,382.7 See notes to condensed financial information.
Condensed Financial Information of Parent Company Only Statement of Earnings	STATEMENTS OF OPERATIONS Year Ended December 31 2018 2017 2016 (in millions of dollars) Cash Dividends from Subsidiaries $ 1,135.4 $ 830.2 $ 676.5 Other Income 66.6 66.6 58.4 Total Revenue 1,202.0 896.8 734.9 Interest and Debt Expense 161.4 154.2 160.1 Other Expenses 53.4 37.1 32.3 Total Expenses 214.8 191.3 192.4 Income of Parent Company Before Income Tax 987.2 705.5 542.5 Income Tax Expense (Benefit) (1.7 ) 115.3 (20.2 ) Income of Parent Company 988.9 590.2 562.7 Equity in Undistributed Earnings (Loss) of Subsidiaries (465.5 ) 404.0 368.7 Net Income 523.4 994.2 931.4 Other Comprehensive Income (Loss), Net of Tax (924.2 ) 178.5 (67.1 ) Comprehensive Income (Loss) $ (400.8 ) $ 1,172.7 $ 864.3 See notes to condensed financial information.
Condensed Financial Information of Parent Company Only Statements of Cash Flows	STATEMENTS OF CASH FLOWS Year Ended December 31 2018 2017 2016 (in millions of dollars) Cash Provided by Operating Activities $ 1,052.1 $ 740.6 $ 685.4 Cash Flows from Investing Activities Proceeds from Sales of Fixed Maturity Securities — — 2.6 Proceeds from Maturities of Fixed Maturity Securities 52.5 194.3 111.2 Proceeds from Sales and Maturities of Other Investments — 35.2 0.4 Purchase of Fixed Maturity Securities (47.9 ) (121.2 ) (56.5 ) Purchase of Other Investments (22.3 ) — (23.3 ) Net Sales (Purchases) of Short-term Investments 192.6 (99.9 ) (89.8 ) Cash Distributions to Subsidiaries (530.8 ) (79.5 ) (143.6 ) Net Purchases of Property and Equipment (73.2 ) (83.3 ) (55.5 ) Acquisition of Business (146.1 ) — (140.3 ) Other, Net — — 0.2 Cash Used by Investing Activities (575.2 ) (154.4 ) (394.6 ) Cash Flows from Financing Activities Short-term Debt Repayment (200.0 ) — — Issuance of Long-term Debt 290.7 — 609.1 Long-term Debt Repayment — — (350.0 ) Issuance of Common Stock 4.6 10.8 8.5 Repurchase of Common Stock (356.2 ) (401.8 ) (405.2 ) Dividends Paid to Stockholders (215.6 ) (196.0 ) (182.6 ) Other, Net (9.3 ) 0.2 (1.0 ) Cash Used by Financing Activities (485.8 ) (586.8 ) (321.2 ) Decrease in Cash $ (8.9 ) $ (0.6 ) $ (30.4 ) See notes to condensed financial information.
Schedule of Debt Instruments Parent Company Only	Debt consists of the following: December 31 2018 2017 Interest Rates Maturities (in millions of dollars) Long-term Debt Outstanding Principal Senior Notes issued 1998 6.750 - 7.250% 2028 $ 365.8 $ 365.8 Senior Notes issued 2002 7.375% 2032 39.5 39.5 Senior Notes issued 2010 5.625% 2020 400.0 400.0 Senior Notes issued 2012 and 2016 5.750% 2042 500.0 500.0 Senior Notes issued 2014 4.000% 2024 350.0 350.0 Senior Notes issued 2015 3.875% 2025 275.0 275.0 Senior Notes issued 2016 3.000% 2021 350.0 350.0 Medium-term Notes issued 1990 - 1996 7.000 - 7.190% 2023 - 2028 50.8 50.8 Junior Subordinated Debt Securities issued 1998 7.405% 2038 226.5 226.5 Junior Subordinated Debt Securities issued 2018 6.250% 2058 300.0 — Fair Value Hedge Adjustment (5.1 ) (4.5 ) Less: Unamortized Net Premium 9.6 9.7 Unamortized Debt Issuance Costs (30.8 ) (24.4 ) Total Long-term Debt 2,831.3 2,538.4 Short-term Debt Outstanding Principal Senior Notes issued 1998 7.000% 2018 — 200.0 Less Unamortized Debt Issuance Costs — (0.1 ) Total Short-term Debt — 199.9 Total Debt $ 2,831.3 $ 2,738.3

Significant Accounting Polici_3

Significant Accounting Policies Schedule of New Accounting Pronouncements (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2018
New Accounting Pronouncements or Change in Accounting Principle
Other Noncash Income (Expense)	$ (46.6)	$ (27.5)	$ (38.4)
Proceeds from Sales and Maturities of Other Investments	454	257.9	331.3
Compensation Expense	885.9	852.3	839.1
Other Expenses	891.2	855	824.6
Other Long-term Investments	702.9	646.8
Deferred Income Tax	0	199
Accumulated Other Comprehensive Income (Loss)	(814.2)	127.5
Retained Earnings	$ 9,863.1	9,542.2
Accounting Standards Update 2016-15
New Accounting Pronouncements or Change in Accounting Principle
Other Noncash Income (Expense)		27.5	38.4
Proceeds from Sales and Maturities of Other Investments		257.9	331.3
Accounting Standards Update 2016-15 | Historical Accounting Method
New Accounting Pronouncements or Change in Accounting Principle
Other Noncash Income (Expense)		12.8	32.9
Proceeds from Sales and Maturities of Other Investments		272.6	336.8
Accounting Standards Update 2016-15 | Effect of Change
New Accounting Pronouncements or Change in Accounting Principle
Other Noncash Income (Expense)		14.7	5.5
Proceeds from Sales and Maturities of Other Investments		(14.7)	(5.5)
Accounting Standards Update 2017-07
New Accounting Pronouncements or Change in Accounting Principle
Compensation Expense		852.3	839.1
Other Expenses		855	824.6
Accounting Standards Update 2017-07 | Historical Accounting Method
New Accounting Pronouncements or Change in Accounting Principle
Compensation Expense		844.4	832.1
Other Expenses		862.9	831.6
Accounting Standards Update 2017-07 | Effect of Change
New Accounting Pronouncements or Change in Accounting Principle
Compensation Expense		7.9	7
Other Expenses		(7.9)	$ (7)
Accounting Standards Update 2016-01
New Accounting Pronouncements or Change in Accounting Principle
Other Long-term Investments		646.8		$ 643
Deferred Income Tax		199		198.2
Accumulated Other Comprehensive Income (Loss)		127.5		110
Retained Earnings		$ 9,542.2		9,556.7
Accounting Standards Update 2016-01 | Effect of Change
New Accounting Pronouncements or Change in Accounting Principle
Other Long-term Investments				(3.8)
Deferred Income Tax				(0.8)
Accumulated Other Comprehensive Income (Loss)				(17.5)
Retained Earnings				$ 14.5

Significant Accounting Polici_4

Significant Accounting Policies - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)Integer	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of Operating Segments | Integer	3
Ceded Policy Loans	$ 3,449.3	$ 3,307.5
Accumulated Depreciation for Property and Equipment	1,151.8	1,067.7
Value of Business Acquired	96.7	27.9
Accumulated Amortization of Value of Business Acquired	133	130.4
Amortization of Value of Business Acquired	6.4	4.8	$ 5.1
Deferred Gain on Reinsurance	12.5	17.7
Premium tax expense	155.8	158	$ 152.5
Participation Fund Account Assets (PFA)	$ 301.2	$ 328.3

Fair Values of Financial Inst_3

Fair Values of Financial Instruments Private Equity Partnerships (Details) - Private Equity Funds of Funds $ in Millions	Dec. 31, 2018USD ($)
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share
Alternative Investments	$ 483.8
Alternative Investments, Unfunded Commitments	385.3
Private Credit
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share
Alternative Investments	194.3	[1]
Alternative Investments, Unfunded Commitments	109.8
Private Credit | Not Redeemable
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share
Alternative Investments	168.6	[1]
Alternative Investments, Unfunded Commitments	99.5
Private Credit | Quarterly after 2 year lock with 90 days notice
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share
Alternative Investments	25.7	[1]
Alternative Investments, Unfunded Commitments	10.3
Private Equity Limited Partnership | Not Redeemable
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share
Alternative Investments	128.3	[2]
Alternative Investments, Unfunded Commitments	169.5
Real Assets
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share
Alternative Investments	161.2	[3]
Alternative Investments, Unfunded Commitments	106
Real Assets | Not Redeemable
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share
Alternative Investments	131	[3]
Alternative Investments, Unfunded Commitments	106
Real Assets | Quarterly
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share
Alternative Investments	30.2	[3]
Alternative Investments, Unfunded Commitments	$ 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, 2018, the estimated remaining life of the investments that do not allow for redemptions is approximately 20 percent in the next 3 years, 46 percent during the period from 3 to 5 years, 30 percent during the period from 5 to 10 years, and 4 percent after the period of 15 years.
[2]	Private Equity - The limited partnerships described in this category employ various strategies generally investing in controlling or minority control equity positions directly in companies and/or assets across various industries (including manufacturing, healthcare, energy, business services, technology, materials, and retail), primarily in private markets within North America and, to a lesser extent, outside of North America. As of December 31, 2018, the estimated remaining life of the investments that do not allow for redemptions is approximately 40 percent in the next 3 years, 9 percent during the period from 3 to 5 years, 49 percent during the period from 5 to 10 years, 1 percent during the period from 10 to 15 years, and 1 percent after the period of 15 years.
[3]	Real Assets - The limited partnerships described in this category employ various strategies, which include investing in the equity and/or debt financing of physical assets, including infrastructure (energy, power, water/wastewater, communications), transportation (including airports, ports, toll roads, aircraft, railcars) and real estate in North America, Europe, South America, and Asia. As of December 31, 2018, the estimated remaining life of the investments that do not allow for redemptions is approximately 2 percent in the next 3 years, 19 percent during period from 3 to 5 years, 75 percent during the period from 5 to 10 years, and 4 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, 2018	Dec. 31, 2017
Fixed Maturity Securities
Fixed Maturity Securities	$ 43,011.7	$ 45,457.8
Derivative Assets	30.9	19.5
Other Long-term Investments	702.9	646.8
Liabilities
Liabilities, Fair Value Disclosure	3,175.5	3,402.4
Fair Value, Inputs, Level 1
Liabilities
Liabilities, Fair Value Disclosure	1,429.8	1,171.8
Fair Value, Inputs, Level 2
Liabilities
Liabilities, Fair Value Disclosure	1,745.7	2,230.6
Fair Value, Inputs, Level 3
Liabilities
Liabilities, Fair Value Disclosure	0	0
Fair Value, Measurements, Recurring
Fixed Maturity Securities
Fixed Maturity Securities	43,011.7	45,457.8
Equity Securities	29.2	11.7
Other Long-term Investments	543.9	438.4
Assets, Fair Value Disclosure	43,555.6	45,896.2
Liabilities
Liabilities, Fair Value Disclosure	69.1	68.1
Fair Value, Measurements, Recurring | Interest Rate Swaps
Liabilities
Derivative Liabilities	5.2	5.1
Fair Value, Measurements, Recurring | Foreign Exchange Contracts
Liabilities
Derivative Liabilities	32.8	46.9
Fair Value, Measurements, Recurring | Credit Default Swaps
Liabilities
Derivative Liabilities		0.2
Fair Value, Measurements, Recurring | Embedded Derivative in Modified Coinsurance Arrangement
Liabilities
Derivative Liabilities	31.1	15.9
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Fixed Maturity Securities
Fixed Maturity Securities	5,031.9	4,170.4
Equity Securities	0	0.2
Other Long-term Investments	0	0.2
Assets, Fair Value Disclosure	5,031.9	4,170.6
Liabilities
Liabilities, Fair Value Disclosure	0	0
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1 | Interest Rate Swaps
Liabilities
Derivative Liabilities	0	0
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1 | Foreign Exchange Contracts
Liabilities
Derivative Liabilities	0	0
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1 | Credit Default Swaps
Liabilities
Derivative Liabilities		0
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1 | Embedded Derivative in Modified Coinsurance Arrangement
Liabilities
Derivative Liabilities	0	0
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Fixed Maturity Securities
Fixed Maturity Securities	36,346.8	39,906.8
Equity Securities	24.6	10.4
Other Long-term Investments	55.5	29.9
Assets, Fair Value Disclosure	36,402.3	39,936.7
Liabilities
Liabilities, Fair Value Disclosure	38	52.2
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | Interest Rate Swaps
Liabilities
Derivative Liabilities	5.2	5.1
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | Foreign Exchange Contracts
Liabilities
Derivative Liabilities	32.8	46.9
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | Credit Default Swaps
Liabilities
Derivative Liabilities		0.2
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | Embedded Derivative in Modified Coinsurance Arrangement
Liabilities
Derivative Liabilities	0	0
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fixed Maturity Securities
Fixed Maturity Securities	1,633	1,380.6
Equity Securities	4.6	1.1
Other Long-term Investments	4.6	1.1
Assets, Fair Value Disclosure	1,637.6	1,381.7
Liabilities
Liabilities, Fair Value Disclosure	31.1	15.9
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3 | Interest Rate Swaps
Liabilities
Derivative Liabilities	0	0
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3 | Foreign Exchange Contracts
Liabilities
Derivative Liabilities	0	0
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3 | Credit Default Swaps
Liabilities
Derivative Liabilities		0
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3 | Embedded Derivative in Modified Coinsurance Arrangement
Liabilities
Derivative Liabilities	31.1	15.9
Fair Value, Measurements, Recurring | Fair Value Measured at Net Asset Value Per Share
Fixed Maturity Securities
Fixed Maturity Securities	0	0
Equity Securities	0	0
Other Long-term Investments	483.8	407.2
Assets, Fair Value Disclosure	483.8	407.2
Liabilities
Liabilities, Fair Value Disclosure	0	0
Fair Value, Measurements, Recurring | Fair Value Measured at Net Asset Value Per Share | Interest Rate Swaps
Liabilities
Derivative Liabilities	0	0
Fair Value, Measurements, Recurring | Fair Value Measured at Net Asset Value Per Share | Foreign Exchange Contracts
Liabilities
Derivative Liabilities	0	0
Fair Value, Measurements, Recurring | Fair Value Measured at Net Asset Value Per Share | Credit Default Swaps
Liabilities
Derivative Liabilities		0
Fair Value, Measurements, Recurring | Fair Value Measured at Net Asset Value Per Share | Embedded Derivative in Modified Coinsurance Arrangement
Liabilities
Derivative Liabilities	0	0
U.S. Government and Agencies
Fixed Maturity Securities
Fixed Maturity Securities	1,814.4	1,482.5
U.S. Government and Agencies | Fair Value, Measurements, Recurring
Fixed Maturity Securities
Fixed Maturity Securities	1,814.4	1,482.5
U.S. Government and Agencies | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Fixed Maturity Securities
Fixed Maturity Securities	513.4	460.1
U.S. Government and Agencies | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Fixed Maturity Securities
Fixed Maturity Securities	1,301	1,022.4
U.S. Government and Agencies | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fixed Maturity Securities
Fixed Maturity Securities	0	0
U.S. Government and Agencies | Fair Value, Measurements, Recurring | Fair Value Measured at Net Asset Value Per Share
Fixed Maturity Securities
Fixed Maturity Securities	0	0
State and Municipal Securities
Fixed Maturity Securities
Fixed Maturity Securities	2,424.2	2,336.9
State and Municipal Securities | Fair Value, Measurements, Recurring
Fixed Maturity Securities
Fixed Maturity Securities	2,424.2	2,336.9
State and Municipal Securities | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Fixed Maturity Securities
Fixed Maturity Securities	0	0
State and Municipal Securities | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Fixed Maturity Securities
Fixed Maturity Securities	2,424.2	2,336.9
State and Municipal Securities | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fixed Maturity Securities
Fixed Maturity Securities	0	0
State and Municipal Securities | Fair Value, Measurements, Recurring | Fair Value Measured at Net Asset Value Per Share
Fixed Maturity Securities
Fixed Maturity Securities	0	0
Foreign Governments
Fixed Maturity Securities
Fixed Maturity Securities	983.7	863.9
Foreign Governments | Fair Value, Measurements, Recurring
Fixed Maturity Securities
Fixed Maturity Securities	983.7	863.9
Foreign Governments | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Fixed Maturity Securities
Fixed Maturity Securities	0	0
Foreign Governments | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Fixed Maturity Securities
Fixed Maturity Securities	952.3	863.9
Foreign Governments | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fixed Maturity Securities
Fixed Maturity Securities	31.4	0
Foreign Governments | Fair Value, Measurements, Recurring | Fair Value Measured at Net Asset Value Per Share
Fixed Maturity Securities
Fixed Maturity Securities	0	0
Public Utilities
Fixed Maturity Securities
Fixed Maturity Securities	7,412.8	8,236.5
Public Utilities | Fair Value, Measurements, Recurring
Fixed Maturity Securities
Fixed Maturity Securities	7,412.8	8,236.5
Public Utilities | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Fixed Maturity Securities
Fixed Maturity Securities	286.4	154.2
Public Utilities | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Fixed Maturity Securities
Fixed Maturity Securities	7,041.7	7,874.6
Public Utilities | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fixed Maturity Securities
Fixed Maturity Securities	84.7	207.7
Public Utilities | Fair Value, Measurements, Recurring | Fair Value Measured at Net Asset Value Per Share
Fixed Maturity Securities
Fixed Maturity Securities	0	0
Mortgage/Asset-backed Securities
Fixed Maturity Securities
Fixed Maturity Securities	1,582.7	1,973.6
Mortgage/Asset-backed Securities | Fair Value, Measurements, Recurring
Fixed Maturity Securities
Fixed Maturity Securities	1,582.7	1,973.6
Mortgage/Asset-backed Securities | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Fixed Maturity Securities
Fixed Maturity Securities	0	0
Mortgage/Asset-backed Securities | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Fixed Maturity Securities
Fixed Maturity Securities	1,582.7	1,973.6
Mortgage/Asset-backed Securities | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fixed Maturity Securities
Fixed Maturity Securities	0	0
Mortgage/Asset-backed Securities | Fair Value, Measurements, Recurring | Fair Value Measured at Net Asset Value Per Share
Fixed Maturity Securities
Fixed Maturity Securities	0	0
Corporate | Fair Value, Measurements, Recurring
Fixed Maturity Securities
Fixed Maturity Securities	28,754	30,522.4
Corporate | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Fixed Maturity Securities
Fixed Maturity Securities	4,232.1	3,556.1
Corporate | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Fixed Maturity Securities
Fixed Maturity Securities	23,026.1	25,816.2
Corporate | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fixed Maturity Securities
Fixed Maturity Securities	1,495.8	1,150.1
Corporate | Fair Value, Measurements, Recurring | Fair Value Measured at Net Asset Value Per Share
Fixed Maturity Securities
Fixed Maturity Securities	0	0
Redeemable Preferred Stocks
Fixed Maturity Securities
Fixed Maturity Securities	39.9	42
Redeemable Preferred Stocks | Fair Value, Measurements, Recurring
Fixed Maturity Securities
Fixed Maturity Securities	39.9	42
Redeemable Preferred Stocks | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Fixed Maturity Securities
Fixed Maturity Securities	0	0
Redeemable Preferred Stocks | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Fixed Maturity Securities
Fixed Maturity Securities	18.8	19.2
Redeemable Preferred Stocks | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fixed Maturity Securities
Fixed Maturity Securities	21.1	22.8
Redeemable Preferred Stocks | Fair Value, Measurements, Recurring | Fair Value Measured at Net Asset Value Per Share
Fixed Maturity Securities
Fixed Maturity Securities	0	0
Foreign Exchange Contracts | Fair Value, Measurements, Recurring
Fixed Maturity Securities
Derivative Assets	30.4	19.5
Foreign Exchange Contracts | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Fixed Maturity Securities
Derivative Assets	0	0
Foreign Exchange Contracts | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Fixed Maturity Securities
Derivative Assets	30.4	19.5
Foreign Exchange Contracts | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fixed Maturity Securities
Derivative Assets	0	0
Foreign Exchange Contracts | Fair Value, Measurements, Recurring | Fair Value Measured at Net Asset Value Per Share
Fixed Maturity Securities
Derivative Assets	0	0
Credit Default Swaps | Fair Value, Measurements, Recurring
Fixed Maturity Securities
Derivative Assets	0.5
Credit Default Swaps | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Fixed Maturity Securities
Derivative Assets	0
Credit Default Swaps | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Fixed Maturity Securities
Derivative Assets	0.5
Credit Default Swaps | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fixed Maturity Securities
Derivative Assets	0
Credit Default Swaps | Fair Value, Measurements, Recurring | Fair Value Measured at Net Asset Value Per Share
Fixed Maturity Securities
Derivative Assets	0
Private Equity Funds of Funds
Fixed Maturity Securities
Alternative Investments	483.8
Private Equity Funds of Funds | Fair Value, Measurements, Recurring
Fixed Maturity Securities
Alternative Investments	483.8	407.2
Private Equity Funds of Funds | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Fixed Maturity Securities
Alternative Investments	0	0
Private Equity Funds of Funds | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Fixed Maturity Securities
Alternative Investments	0	0
Private Equity Funds of Funds | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fixed Maturity Securities
Alternative Investments	0	0
Private Equity Funds of Funds | Fair Value, Measurements, Recurring | Fair Value Measured at Net Asset Value Per Share
Fixed Maturity Securities
Alternative Investments	483.8	407.2
Derivatives | Fair Value, Measurements, Recurring
Liabilities
Derivative Liabilities	69.1	68.1
Derivatives | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Liabilities
Derivative Liabilities	0	0
Derivatives | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Liabilities
Derivative Liabilities	38	52.2
Derivatives | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Liabilities
Derivative Liabilities	31.1	15.9
Derivatives | Fair Value, Measurements, Recurring | Fair Value Measured at Net Asset Value Per Share
Liabilities
Derivative Liabilities	$ 0	$ 0

Changes in Assets and Liabiliti

Changes in Assets and Liabilities Measured at Fair Value on a Recurring Basis using Significant Unobservable Inputs (Level 3) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Embedded Derivative in Modified Coinsurance Arrangement
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Derivatives Measured with Unobservable Inputs, Beginning Balance	$ (15.9)	$ (46.7)
Derivative Liability Gain (Loss) Included in Earnings	(15.2)	30.8
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	(31.1)	(15.9)
State and Municipal Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Assets Measured with Unobservable Inputs, Beginning Balance	0	89.5
Investment Gain (Loss) included in Earnings		0
Investment Gain (Loss) included in OCI		0
Investment Purchases		0
Investment Sales		0
Investment Level 3 Transfers Into		0
Investment Level 3 Transfers Out of		(89.5)
Assets Measured with Unobservable Inputs, Ending Balance		0
Foreign Governments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Assets Measured with Unobservable Inputs, Beginning Balance	0
Investment Gain (Loss) included in Earnings	0
Investment Gain (Loss) included in OCI	(1.4)
Investment Purchases	0
Investment Sales	0
Investment Level 3 Transfers Into	32.8
Investment Level 3 Transfers Out of	0
Assets Measured with Unobservable Inputs, Ending Balance	31.4	0
Public Utilities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Assets Measured with Unobservable Inputs, Beginning Balance	207.7	265.3
Investment Gain (Loss) included in Earnings	0	0
Investment Gain (Loss) included in OCI	(2.3)	0.3
Investment Purchases	0	8
Investment Sales	0	(4.8)
Investment Level 3 Transfers Into	39	125.2
Investment Level 3 Transfers Out of	(159.7)	(186.3)
Assets Measured with Unobservable Inputs, Ending Balance	84.7	207.7
Corporate
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Assets Measured with Unobservable Inputs, Beginning Balance	1,150.1	1,459.7
Investment Gain (Loss) included in Earnings	5.8	(0.6)
Investment Gain (Loss) included in OCI	(118.1)	2.8
Investment Purchases	95.1	118.9
Investment Sales	(148.7)	(149.2)
Investment Level 3 Transfers Into	968.6	524.7
Investment Level 3 Transfers Out of	(457)	(806.2)
Assets Measured with Unobservable Inputs, Ending Balance	1,495.8	1,150.1
Redeemable Preferred Stocks
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Assets Measured with Unobservable Inputs, Beginning Balance	22.8	23.2
Investment Gain (Loss) included in Earnings	0	0
Investment Gain (Loss) included in OCI	(1.7)	(0.4)
Investment Purchases	0	0
Investment Sales	0	0
Investment Level 3 Transfers Into	0	0
Investment Level 3 Transfers Out of	0	0
Assets Measured with Unobservable Inputs, Ending Balance	21.1	22.8
Fixed Maturity Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Assets Measured with Unobservable Inputs, Beginning Balance	1,380.6	1,837.7
Investment Gain (Loss) included in Earnings	5.8	(0.6)
Investment Gain (Loss) included in OCI	(123.5)	2.7
Investment Purchases	95.1	126.9
Investment Sales	(148.7)	(154)
Investment Level 3 Transfers Into	1,040.4	649.9
Investment Level 3 Transfers Out of	(616.7)	(1,082)
Assets Measured with Unobservable Inputs, Ending Balance	1,633	1,380.6
Equity Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Assets Measured with Unobservable Inputs, Beginning Balance	1.1	1.2
Investment Gain (Loss) included in Earnings	0	0
Investment Gain (Loss) included in OCI	0	0
Investment Purchases	3.5	0
Investment Sales	0	0
Investment Level 3 Transfers Into	0	0
Investment Level 3 Transfers Out of	0	(0.1)
Assets Measured with Unobservable Inputs, Ending Balance	$ 4.6	$ 1.1

Quantitative Information Regard

Quantitative Information Regarding Significant Unobservable Inputs (Details) - Fair Value, Inputs, Level 3 $ in Millions		Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Discounted Cash Flow | Embedded Derivative in Modified Coinsurance Arrangement
Fair Value Inputs, Assets and Liabilities, Quantitative Information
Embedded Derivative in Modified Coinsurance Arrangement		$ (31.1)	$ (15.9)
Embedded Derivative in Modified Coinsurance Arrangement, Measurement Input		us-gaap:ProjectedCashFlowsActuarialAssumptionsMember	us-gaap:ProjectedCashFlowsActuarialAssumptionsMember	[1]
All Other Corporate Bonds - Private | Market Approach
Fair Value Inputs, Assets and Liabilities, Quantitative Information
All Other Corporate Bonds - Private		$ 148.5	$ 244.4
All Other Corporate Bonds - Private, Market Convention, Measurement Input	[2]	us-gaap:MarketConventionPricedatParMember	us-gaap:MarketConventionPricedatParMember
All Other Corporate Bonds - Private | Comparability Adjustment | Market Approach | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information
All Other Corporate Bonds - Private, Measurement Input	[3]		0.0020
All Other Corporate Bonds - Private | Comparability Adjustment | Market Approach | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information
All Other Corporate Bonds - Private, Measurement Input	[3]		0.0020
All Other Corporate Bonds - Private | Comparability Adjustment | Market Approach | Weighted Average
Fair Value Inputs, Assets and Liabilities, Quantitative Information
All Other Corporate Bonds - Private, Measurement Input	[3]		0.0020
All Other Corporate Bonds - Private | Lack of Marketability | Market Approach | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information
All Other Corporate Bonds - Private, Measurement Input	[4]	0.0025	0.0025
All Other Corporate Bonds - Private | Lack of Marketability | Market Approach | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information
All Other Corporate Bonds - Private, Measurement Input	[4]	0.0025	0.0025
All Other Corporate Bonds - Private | Lack of Marketability | Market Approach | Weighted Average
Fair Value Inputs, Assets and Liabilities, Quantitative Information
All Other Corporate Bonds - Private, Measurement Input	[4]	0.0025	0.0025
All Other Corporate Bonds - Private | Volatility of Credit | Market Approach | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information
All Other Corporate Bonds - Private, Measurement Input	[5]	0.0025	0.0012
All Other Corporate Bonds - Private | Volatility of Credit | Market Approach | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information
All Other Corporate Bonds - Private, Measurement Input	[5]	0.1099	0.0625
All Other Corporate Bonds - Private | Volatility of Credit | Market Approach | Weighted Average
Fair Value Inputs, Assets and Liabilities, Quantitative Information
All Other Corporate Bonds - Private, Measurement Input	[5]	0.0100	0.0050
Equity Securities | Market Approach
Fair Value Inputs, Assets and Liabilities, Quantitative Information
Equity Securities - Private		$ 4.6	$ 1.1
Equity Securities - Private, Measurement Input	[2]	us-gaap:MarketConventionPricedatCostorOwnersEquityMember	us-gaap:MarketConventionPricedatCostorOwnersEquityMember
[1]	Represents various actuarial assumptions required to derive the liability cash flows including incidence, termination, and lapse rates
[2]	Represents a decision to price based on par value, cost, or owner's equity when limited data is available
[3]	Represents basis point adjustments for changes in benchmark spreads associated with various industry sectors
[4]	Represents basis point adjustments to apply a discount due to the illiquidity of an investment
[5]	Represents basis point adjustments for credit-specific factors

Fair Values of Financial Inst_4

Fair Values of Financial Instruments Carrying Amounts and Estimated Fair value of Financial Instruments Not Measured at Fair Value (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Mortgage Loans, Fair Value Disclosure	$ 2,317.4	$ 2,306.2
Mortgage Loans	2,295	2,213.2
Policy Loans, Fair Value Disclosure	3,831.1	3,677.5
Policy Loans	3,729.9	3,571.1
Miscellaneous Long-Term Investments, Fair Value Disclosure	115.6	162.3
Financial Instruments, Financial Assets Fair Value Disclosure	6,264.1	6,146
Long-term Debt, Fair Value Disclosure	3,069.2	3,048.7
Long-term Debt	2,971.3	2,738.4
Federal Home Loan Bank Funding Agreements, Fair Value Disclosure	104	350
Unfunded Commitments	2.3	3.7
Liabilities, Fair Value Disclosure	3,175.5	3,402.4
Fair Value, Inputs, Level 1
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	1,429.8	1,171.8
Federal Home Loan Bank Funding Agreements, Fair Value Disclosure	0	0
Unfunded Commitments	0	0
Liabilities, Fair Value Disclosure	1,429.8	1,171.8
Fair Value, Inputs, Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Mortgage Loans, Fair Value Disclosure	2,317.4	2,306.2
Policy Loans, Fair Value Disclosure	0	0
Miscellaneous Long-Term Investments, Fair Value Disclosure	24.1	34.1
Financial Instruments, Financial Assets Fair Value Disclosure	2,341.5	2,340.3
Long-term Debt, Fair Value Disclosure	1,639.4	1,876.9
Federal Home Loan Bank Funding Agreements, Fair Value Disclosure	104	350
Unfunded Commitments	2.3	3.7
Liabilities, Fair Value Disclosure	1,745.7	2,230.6
Fair Value, Inputs, Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Mortgage Loans, Fair Value Disclosure	0	0
Policy Loans, Fair Value Disclosure	3,831.1	3,677.5
Miscellaneous Long-Term Investments, Fair Value Disclosure	91.5	128.2
Financial Instruments, Financial Assets Fair Value Disclosure	3,922.6	3,805.7
Long-term Debt, Fair Value Disclosure	0	0
Federal Home Loan Bank Funding Agreements, Fair Value Disclosure	0	0
Unfunded Commitments	0	0
Liabilities, Fair Value Disclosure	0	0
Reported Value Measurement
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Mortgage Loans	2,295	2,213.2
Policy Loans	3,729.9	3,571.1
Miscellaneous Long-Term Investments	115.6	162.3
Total Financial Instrument Assets Not Carried at Fair Value	6,140.5	5,946.6
Long-term Debt	2,971.3	2,738.4
Federal Home Loan Bank Funding Agreements	104	350
Unfunded Commitments	2.3	3.7
Total Financial Instrument Liabilities Not Carried at Fair Value	$ 3,077.6	$ 3,092.1

Fair Value of Financial Instrum

Fair Value of Financial Instruments Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Gain (Loss) on Embedded Derivative	$ (15.2)	$ 30.8	$ 40.9
Ceded Policy Loans	$ 3,449.3	$ 3,307.5
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	11.70%
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	75.00%
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	3.60%
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	88.30%
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	9.70%

Amortized Cost and Fair Values

Amortized Cost and Fair Values of Securities by Security Type (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale
Debt Securities, Available-for-sale, Amortized Cost	$ 40,275.2	$ 39,780.5
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	3,492.9
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	756.4
Fixed Maturity Securities	43,011.7	45,457.8
U.S. Government and Agencies
Debt Securities, Available-for-sale
Debt Securities, Available-for-sale, Amortized Cost	1,702.1	1,311.1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	123.2	176.1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	10.9	4.7
Fixed Maturity Securities	1,814.4	1,482.5
State and Municipal Securities
Debt Securities, Available-for-sale
Debt Securities, Available-for-sale, Amortized Cost	2,121.5	1,942.8
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	307.1	395.4
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	4.4	1.3
Fixed Maturity Securities	2,424.2	2,336.9
Foreign Governments
Debt Securities, Available-for-sale
Debt Securities, Available-for-sale, Amortized Cost	825.8	673
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	162.7	191.3
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	4.8	0.4
Fixed Maturity Securities	983.7	863.9
Public Utilities
Debt Securities, Available-for-sale
Debt Securities, Available-for-sale, Amortized Cost	6,626.2	6,952.7
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	850	1,296.4
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	63.4	12.6
Fixed Maturity Securities	7,412.8	8,236.5
Mortgage/Asset-backed Securities
Debt Securities, Available-for-sale
Debt Securities, Available-for-sale, Amortized Cost	1,523.8	1,873.2
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	67.2	105.1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	8.3	4.7
Fixed Maturity Securities	1,582.7	1,973.6
All Other Corporate Bonds
Debt Securities, Available-for-sale
Debt Securities, Available-for-sale, Amortized Cost	27,436.8	26,988.7
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1,981.6	3,633.5
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	664.4	99.8
Fixed Maturity Securities	28,754	30,522.4
Redeemable Preferred Stocks
Debt Securities, Available-for-sale
Debt Securities, Available-for-sale, Amortized Cost	39	39
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1.1	3
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0.2	0
Fixed Maturity Securities	39.9	42
Fixed Maturity Securities
Debt Securities, Available-for-sale
Debt Securities, Available-for-sale, Amortized Cost	40,275.2	39,780.5
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	3,492.9	5,800.8
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	756.4	123.5
Fixed Maturity Securities	$ 43,011.7	$ 45,457.8

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, 2018	Dec. 31, 2017
U.S. Government and Agencies
Debt Securities, Available-for-sale
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 68.8	$ 157.9
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	1.7	3
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	212.5	58.8
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	9.2	1.8
State and Municipal Securities
Debt Securities, Available-for-sale
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	183.2	45.7
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	2.1	0.5
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	65	22.3
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	2.3	0.7
Foreign Governments
Debt Securities, Available-for-sale
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	58.4	13.2
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	3.8	0.4
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	12	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	1	0
Public Utilities
Debt Securities, Available-for-sale
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	740.1	213.2
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	31.3	7.9
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	325.7	133.5
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	32.1	4.7
Mortgage/Asset-backed Securities
Debt Securities, Available-for-sale
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	81.5	252.5
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	1.2	1.4
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	201.6	144.7
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	7.1	3.3
All Other Corporate Bonds
Debt Securities, Available-for-sale
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	9,240.2	1,355.1
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	462.2	26.8
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	1,704.9	785.2
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	202.2	73
Redeemable Preferred Stocks
Debt Securities, Available-for-sale
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	18.8
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0.2
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0
Fixed Maturity Securities
Debt Securities, Available-for-sale
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	10,391	2,037.6
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	502.5	40
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	2,521.7	1,144.5
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 253.9	$ 83.5

Investments Distribution of the

Investments Distribution of the Maturity Dates for Fixed Maturity Securities (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale, Amortized Cost, Fiscal Year Maturity [Abstract]
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Amortized Cost	$ 1,073.3	$ 1,625.1
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Amortized Cost	6,267.5	5,579.9
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Amortized Cost	12,573.4	12,091.1
Debt Securities, Available-for-sale, Allocated and Single Maturity Date, Maturity, after 10 Years, Amortized Cost	18,837.2	18,611.2
Available for sale Securities Debt Maturities Amortized Cost Gross Subtotal	38,751.4	37,907.3
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Amortized Cost	1,523.8	1,873.2
Debt Securities, Available-for-sale, Amortized Cost	40,275.2	39,780.5
Available for Sale Securities Unrealized Gain Position Gross Gain
Available For Sale Securities Debt Maturities Within One Year Unrealized Gain Position Gross Gain	14.5	30.9
Available For Sale Securities Debt Maturities After One Through Five Years Unrealized Gain Position Gross Gain	300.6	453.6
Available For Sale Securities Debt Maturities After Five Through Ten Years Unrealized Gain Position Gross Gain	795	1,169.8
Available For Sale Securities Debt Maturities After Ten Years Unrealized Gain Position Gross Gain	2,315.6	4,041.4
Available For Sale Securities Debt Maturities Unrealized Gain Position Gross Gain Gross Subtotal	3,425.7	5,695.7
Available For Sale Securities Debt Maturities Without Single Maturity Date Unrealized Gain Position Gross Gain	67.2	105.1
Available for sale Securities, Debt Maturities Unrealized Gain Position Gross Gain	3,492.9	5,800.8
Available for Sale Securities Unrealized Loss Position Gross Loss
Available For Sale Securities Debt Maturities Within One Year Unrealized Loss Position Gross Loss	8.4	3.1
Available For Sale Securities Debt Maturities After One Through Five Years Unrealized Loss Position Gross Loss	80.2	18.5
Available For Sale Securities Debt Maturities After Five Through Ten Years Unrealized Loss Position Gross Loss	303.9	53.2
Available For Sale Securities Debt Maturities After Ten Years Unrealized Loss Position Gross Loss	355.6	44
Available For Sale Securities Debt Maturities Unrealized Gain Position Gross Loss Gross Subtotal	748.1	118.8
Available For Sale Securities Debt Maturities Without Single Maturity Date Unrealized Loss Position Gross Loss	8.3	4.7
Available For Sale Securities Unrealized Loss Position Gross Loss Subtotal	756.4	123.5
Fair Value Maturity Distribution [Abstract]
Fixed Maturity Securities	43,011.7	45,457.8
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	1,020.1	1,638.8
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Fair Value	5,186.9	5,810.9
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Fair Value	6,812.7	11,916.5
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after 10 Years, Fair Value	15,779.7	21,333.1
Available for sale Securities Debt Maturities Fair Value Gross Subtotal	28,799.4	40,699.3
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Fair Value	1,299.6	1,576.4
Fixed Maturity Securities	30,099	42,275.7
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	59.3	14.1
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Fair Value	1,301	204.1
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Fair Value	6,251.8	1,291.2
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after 10 Years, Fair Value	5,017.5	1,275.5
Available for sale Securities Debt Maturities Fair Value Gross Subtotal	12,629.6	2,784.9
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Fair Value	283.1	397.2
Fixed Maturity Securities	$ 12,912.7	$ 3,182.1

Investments Distribution by Ext

Investments Distribution by External Credit Rating for Fixed Maturity Securities (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale
Fixed Maturity Securities	$ 43,011.7	$ 45,457.8
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	3,492.9
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	$ 756.4
Fixed maturity securities in unrealized loss position percent of total	100.00%
External Credit Rating, Investment Grade
Debt Securities, Available-for-sale
Fixed Maturity Securities	$ 39,973.1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	3,464.2
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	$ 529.5
Fixed maturity securities in unrealized loss position percent of total	70.00%
External Credit Rating, Below-Investment-Grade
Debt Securities, Available-for-sale
Fixed Maturity Securities	$ 3,038.6
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	28.7
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	$ 226.9
Fixed maturity securities in unrealized loss position percent of total	30.00%

Investments Low Income Housing

Investments Low Income Housing Tax Credits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Low Income Housing Tax Credits [Abstract]
Affordable Housing Tax Credits	$ 41.4	$ 41.8	$ 41.8
Amortization of Affordable Housing Tax Credit Investments	(28.1)	(23.2)	(23.2)
Tax Benefits from Low Income Housing Investments	$ 13.3	$ 18.6	$ 18.6

Mortgage Loans by Property Type

Mortgage Loans by Property Type and Geographic Region (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Mortgage Loans on Real Estate
Mortgage Loans	$ 2,295	$ 2,213.2
Percent of Total	100.00%	100.00%
New England
Mortgage Loans on Real Estate
Mortgage Loans	$ 45.9	$ 56.1
Percent of Total	2.00%	2.50%
Mid-Atlantic
Mortgage Loans on Real Estate
Mortgage Loans	$ 160.6	$ 155.5
Percent of Total	7.00%	7.00%
East North Central
Mortgage Loans on Real Estate
Mortgage Loans	$ 354.4	$ 282
Percent of Total	15.40%	12.80%
West North Central
Mortgage Loans on Real Estate
Mortgage Loans	$ 190.3	$ 210.1
Percent of Total	8.30%	9.50%
South Atlantic
Mortgage Loans on Real Estate
Mortgage Loans	$ 485.2	$ 494.4
Percent of Total	21.10%	22.30%
East South Central
Mortgage Loans on Real Estate
Mortgage Loans	$ 105.5	$ 88.8
Percent of Total	4.60%	4.00%
West South Central
Mortgage Loans on Real Estate
Mortgage Loans	$ 240.6	$ 247.4
Percent of Total	10.50%	11.20%
Mountain
Mortgage Loans on Real Estate
Mortgage Loans	$ 242.7	$ 251.2
Percent of Total	10.60%	11.40%
Pacific
Mortgage Loans on Real Estate
Mortgage Loans	$ 469.8	$ 427.7
Percent of Total	20.50%	19.30%
Apartment
Mortgage Loans on Real Estate
Mortgage Loans	$ 491	$ 360
Percent of Total	21.40%	16.30%
Industrial
Mortgage Loans on Real Estate
Mortgage Loans	$ 635.6	$ 601.2
Percent of Total	27.70%	27.20%
Office
Mortgage Loans on Real Estate
Mortgage Loans	$ 604.2	$ 692.3
Percent of Total	26.30%	31.30%
Retail
Mortgage Loans on Real Estate
Mortgage Loans	$ 519.5	$ 527.6
Percent of Total	22.60%	23.80%
Other Property
Mortgage Loans on Real Estate
Mortgage Loans	$ 44.7	$ 32.1
Percent of Total	2.00%	1.40%

Mortgage Loans, Sorted by Appli

Mortgage Loans, Sorted by Applicable Credit Quality Indicators (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Mortgage Loans on Real Estate
Mortgage Loans	$ 2,295	$ 2,213.2
Aa Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans	0	0.4
A Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans	477.5	445.7
Baa Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans	1,814.1	1,753
Ba Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans	3.4	14.1
Loan to Value Ratio Below or Equal to 65 Percent
Mortgage Loans on Real Estate
Mortgage Loans	1,204.8	1,101.7
Loan To Value Ratio Above 65 To 75 Percent
Mortgage Loans on Real Estate
Mortgage Loans	1,049.1	1,041.6
Loan To Value Ratio Above 75 To 85 Percent
Mortgage Loans on Real Estate
Mortgage Loans	11.8	49.3
Loan To Value Ratio Above 85 Percent
Mortgage Loans on Real Estate
Mortgage Loans	$ 29.3	$ 20.6

Investments Remaining Contractu

Investments Remaining Contractual Maturity of Security Lending Agreements (Details) - Overnight and Continuous - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Transfer of Certain Financial Assets Accounted for as Secured Borrowings
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred	$ 0.1	$ 30.5
Securities Loaned and Securities Sold under Agreement to Repurchase, Gross Including Not Subject to Master Netting Arrangement	0.1	30.5
Secured Borrowings, Gross, Difference, Amount	0	0
U.S. Government and Agencies
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	0.2
Public Utilities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred	0	0.5
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	$ 0.1	$ 29.8

Investments Federal Home Loan B

Investments Federal Home Loan Bank Carrying Amount, Collateral Posted and Advances Received (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Federal Home Loan Bank Carrying Value of Common Stock, Collateral Posted and Advances
Federal Home Loan Bank Common Stock	$ 24.1	$ 34.1
Federal Home Loan Bank, Advances	104	350
Federal Home Loan Bank, Collateral Posted to FHLB	399.7	544.8
Fixed Maturity Securities
Federal Home Loan Bank Carrying Value of Common Stock, Collateral Posted and Advances
Federal Home Loan Bank, Collateral Posted to FHLB	219.8	213.3
Commercial Mortgage Loans
Federal Home Loan Bank Carrying Value of Common Stock, Collateral Posted and Advances
Federal Home Loan Bank, Collateral Posted to FHLB	$ 179.9	$ 331.5

Investments Schedule of Financi

Investments Schedule of Financial Instrument and Derivative Offsetting (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Offsetting Derivative Assets
Gross Derivative Asset	$ 30.9	$ 19.5
Derivative Liabilities Offsetting Derivative Assets in Balance Sheet	0	0
Net Derivative Assets Reported in Balance Sheet	30.9	19.5
Securities Received as Collateral on Derivative Assets	(6.9)	(4.2)
Cash Collateral from Counterparties	(24)	(15.3)
Derivative Assets Net of Collateral	0	0
Offsetting Securities Borrowed
Gross Securities Borrowed	164.1	159.2
Liabilities Offsetting Securities Borrowed in Balance Sheet	0	0
Net Securities Borrowed Reported in Balance Sheet	164.1	159.2
Securities Received as Collateral on Securities Borrowed	(164)	(128.7)
Cash Received as Collateral on Securities Borrowed	(0.1)	(30.5)
Securities Borrowed Net of Collateral	0	0
Offsetting Financial Assets
Gross Financial Assets	195	178.7
Financial Liabilities Offsetting Financial Assets in Balance Sheet	0	0
Net Financial Assets Reported in Balance Sheet	195	178.7
Securities Received as Collateral on Financial Assets	(170.9)	(132.9)
Cash Received as Collateral on Financial Assets	(24.1)	(45.8)
Financial Assets Net of Collateral	0	0
Offsetting Securities Loaned
Gross Securities Loaned	0.1	30.5
Assets Offsetting Securities Loaned in Balance Sheet	0	0
Net Securities Loaned Reported in Balance Sheet	0.1	30.5
Securities Given as Collateral on Securities Loaned	(0.1)	(30.5)
Cash Given as Collateral on Securities Loaned	0	0
Securities Loaned Net of Collateral	0	0
Offsetting Financial Liabilities
Gross Financial Liability	38.1	82.7
Financial Assets Offsetting Financial Liabilities in Balance Sheet	0	0
Net Financial Liabilities Reported in Balance Sheet	38.1	82.7
Securities Given as Collateral on Financial Liabilities	(33.3)	(73.4)
Cash Given as Collateral on Financial Liabilities	0	0
Financial Liabilities Net of Collateral	4.8	9.3
Over the Counter
Offsetting Derivative Liabilities
Gross Derivative Liability	38	52.2
Derivative Assets Offsetting Derivative Liabilities in Balance Sheet	0	0
Net Derivative Liabilities Reported in Balance Sheet	38	52.2
Securities Given as Collateral on Derivative Liabilities	(33.2)	(42.9)
Cash Collateral to counterparties	0	0
Derivative Liabilities Net of Collateral	$ 4.8	$ 9.3

Investments Investment Income (

Investments Investment Income (Detail) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net Investment Income
Investment Income, Interest and Dividend										$ 2,502.4	$ 2,498.6	$ 2,505.1
Less Investment Expenses										35.2	32.8	31.9
Less Investment Income on PFA Assets										13.5	14.1	14.2
Net Investment Income		$ 608.6	$ 619.2	$ 623.6	$ 602.3	$ 619.8	$ 609	$ 620.5	$ 602.4	2,453.7	2,451.7	2,459
Fixed Maturity Securities
Net Investment Income
Investment Income, Interest and Dividend										2,239.7	2,271.8	2,293.9
Derivatives
Net Investment Income
Investment Income, Interest and Dividend										66.1	56.4	49.8
Mortgage Loans
Net Investment Income
Investment Income, Interest and Dividend										110.1	104.2	114
Policy Loans
Net Investment Income
Investment Income, Interest and Dividend										18.6	17.9	17.3
Equity Securities
Net Investment Income
Investment Income, Interest and Dividend	[1]									(0.2)	1.5	1.2
Partnership Interest
Net Investment Income
Investment Income, Interest and Dividend	[2]									36	25.5	11.4
Miscellaneous Long-term Investments
Net Investment Income
Investment Income, Interest and Dividend										8.4	10	10
Short-term Investments
Net Investment Income
Investment Income, Interest and Dividend										$ 23.7	$ 11.3	$ 7.5
[1]	The net unrealized loss recognized in net investment income for the year ended December 31, 2018 related to equity securities still held at December 31, 2018 was $3.9 million.
[2]	The net unrealized gain recognized in net investment income for the year ended December 31, 2018 related to private equity partnerships still held at December 31, 2018 was $7.1 million.

Realized Investment Gains and L

Realized Investment Gains and Losses Reported in Consolidated Statements of Income (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fixed Maturity Securities
Gross Gains on Sales									$ 9.7	$ 13.8	$ 34.3
Gross Losses on Sales									(15.2)	(4.4)	(17.2)
Other-Than-Temporary Impairment Loss									(17.5)	(8.1)	(30.5)
Mortgage Loans and Other Invested Assets
Gross Gains on Sales									0.5	9.4	5.5
Gross Losses on Sales									0	(0.2)	(0.7)
Impairment Loss									(1.4)	(0.9)	(5.7)
Gain (Loss) on Embedded Derivative									(15.2)	30.8	40.9
All Other Derivatives									0.3	(0.1)	(1.5)
Foreign Currency Transactions									(0.7)	0	(0.9)
Net Realized Investment Gain (Loss)	$ (41.4)	$ 6.7	$ (2.6)	$ (2.2)	$ 11.4	$ 9.8	$ 8.1	$ 11	$ (39.5)	$ 40.3	$ 24.2

Investments - Additional Inform

Investments - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2018USD ($)Integer	Dec. 31, 2017USD ($)Integer	Dec. 31, 2016USD ($)Integer
Schedule of Investments
Fixed Maturity Securities Other Than Temporary Impairments in Accumulated Other Comprehensive Income Loss	$ 0	$ 0
Commitment to Fund Private Placement Fixed Maturity Securities	117,300,000
Carrying Amount of Variable Interest Entity Investments	575,300,000	535,400,000
Unfunded Commitments	2,300,000	3,700,000
Fixed Maturity Securities	43,011,700,000	45,457,800,000
Other Long-term Investments	$ 702,900,000	646,800,000
Mortgage Loan Policy is not to Exceed a Loan-to-value Ratio, Percent	75.00%
Loan to Value Ratio Update Frequency	three
Mortgage Loan Inspection Frequency	two
Mortgage Loan Policy Debt Service Coverage Ratio, Lower Range	125.00%
Mortgage Loans Issuance, Term Years	25
Number of Changes to Accounting Policy for Estimating Credit Losses on Mortgage Loans	0
Financing Receivable, Allowance for Credit Losses			$ 0
Foreclosed Real Estate Expense	$ 0	0	0
Average Recorded Investment of Impaired Mortgage Loans	2,300,000	0	2,200,000
Interest Income on Mortgage Loans Subsequent to Impairment	0	0	0
Committments to Fund Commercial Mortgage Loans	$ 13,000,000
Repurchase agreements - Typical Days outstanding	30
Minimum percent of the fair value of securities loaned or securities purchased under repurchase agreements be maintained as collateral	102.00%
Gross Securities Borrowed	$ 164,100,000	159,200,000
Outstanding Repurchase Agreements	0	0
Off Balance Sheet Amount
Schedule of Investments
Cash Collateral for Borrowed Securities	100,000	30,500,000
Securities Received as Collateral	171,400,000	135,600,000
Commercial Real Estate Portfolio Segment
Schedule of Investments
Loans and Leases Receivable, Allowance	200,000	0	0
Provision for Loan and Lease Losses	200,000	0	$ 0
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	0	0
Fixed Maturity Securities
Schedule of Investments
Fixed Maturity Securities	$ 43,011,700,000	$ 45,457,800,000
Commercial Real Estate Portfolio Segment
Schedule of Investments
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | Integer			1
Financing Receivable, Modifications, Number of Contracts | Integer	1	0
Impaired Financing Receivable, with No Related Allowance, Recorded Investment			$ 5,400,000
Financing Receivable, Modifications, Pre-Modification Recorded Investment	$ 3,600,000
Impaired Financing Receivable, with Related Allowance, Recorded Investment	3,400,000
Special Purpose Entity | Bonds
Schedule of Investments
Fixed Maturity Securities	156,700,000	$ 154,100,000
Special Purpose Entity | Partnership Interest
Schedule of Investments
Other Long-term Investments			$ 1,000,000
Gain (Loss) on Investments, Excluding Other than Temporary Impairments		(200,000)
Partnership Interests In Tax Credit Investments
Schedule of Investments
Carrying Amount of Variable Interest Entity Investments	91,500,000	128,200,000
Equity Method Investments
Schedule of Investments
Carrying Amount of Variable Interest Entity Investments	$ 483,800,000	$ 407,200,000
External Credit Rating, Investment Grade
Schedule of Investments
Number of Fixed Maturity Securities in an Unrealized Loss Position	552
Number of Fixed Maturity Securities in an Unrealized Loss Position Continuously for Over One Year	204
Fixed Maturity Securities	$ 39,973,100,000
External Credit Rating, Below-Investment-Grade
Schedule of Investments
Number of Fixed Maturity Securities in an Unrealized Loss Position	135
Number of Fixed Maturity Securities in an Unrealized Loss Position Continuously for Over One Year	32
Fixed Maturity Securities	$ 3,038,600,000

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, 2018	Dec. 31, 2017
Derivative
Cash Collateral from Counterparties	$ 24	$ 15.3
Carrying Value of Fixed Maturity Securities Posted as Collaterial to Counterparties	6.9	4.2
Total Amount
Derivative
Cash Collateral from Counterparties	24	15.7
Fixed Maturity Securities
Derivative
Carrying Value of Fixed Maturity Securities Posted as Collaterial to Counterparties	$ 33.4	$ 46.4

Notional Amounts for Each Categ

Notional Amounts for Each Category of Derivative Activity (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Derivative
Balance at beginning of period	$ 904.5	$ 1,052	$ 1,470.3
Additions	136.5	92.1	33.5
Terminations	241.8	239.6	451.8
Balance at ending of period	799.2	904.5	1,052
Interest Rate Swaps | Receive Variable/Pay Fixed
Derivative
Balance at beginning of period	48	105.5	150
Additions	0	0	3.5
Terminations	48	57.5	48
Balance at ending of period	0	48	105.5
Interest Rate Swaps | Receive Fixed/Pay Fixed
Derivative
Balance at beginning of period	536.5	616.5	650.3
Additions	78.1	26.4	0
Terminations	76.4	106.4	33.8
Balance at ending of period	538.2	536.5	616.5
Interest Rate Swaps | Receive Fixed/Pay Variable
Derivative
Balance at beginning of period	250	250	600
Additions	0	0	0
Terminations	0	0	350
Balance at ending of period	250	250	250
Credit Default Swaps | Credit Default Swaps
Derivative
Balance at beginning of period	70	70	70
Additions	11	0	0
Terminations	70	0	0
Balance at ending of period	11	70	70
Forwards
Derivative
Balance at beginning of period	0	10	0
Additions	47.4	65.7	30
Terminations	47.4	75.7	20
Balance at ending of period	$ 0	$ 0	$ 10

Derivative Financial Instrume_4

Derivative Financial Instruments Fair Value Hedges Carrying Amount of Hedged Assets and Liabilities and Cumulative Basis Adjustments (Details) - Interest Rate Swaps - Designated as Hedging Instrument - Fair Value Hedging - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Fixed Maturity Securities | Receive Variable/Pay Fixed
Derivative Instruments and Hedging Activities Disclosures
Hedged Asset, Fair Value Hedge	$ 0	$ 48.5
Hedged Asset, Fair Value Hedge, Cumulative Increase (Decrease)	0	0.6
Fixed Maturity Securities | Receive Fixed/Pay Fixed
Derivative Instruments and Hedging Activities Disclosures
Hedged Asset, Fair Value Hedge	56.2	0
Hedged Asset, Fair Value Hedge, Cumulative Increase (Decrease)	(2.7)	0
Long-term Debt | Receive Fixed/Pay Variable
Derivative Instruments and Hedging Activities Disclosures
Hedged Liability, Fair Value Hedge	(244.4)	(244.8)
Hedged Liability, Fair Value Hedge, Cumulative Increase (Decrease)	$ 5.1	$ 4.5

Location and Fair Values of Der

Location and Fair Values of Derivative Financial Instruments (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Derivative
Asset Derivatives Fair Value	$ 30.9	$ 19.5
Designated as Hedging Instrument | Miscellaneous Long-term Investments
Derivative
Asset Derivatives Fair Value	30.4	19.5
Designated as Hedging Instrument | Other Liabilities
Derivative
Liability Derivatives Fair Value	13.5	24.5
Not Designated as Hedging Instrument | Miscellaneous Long-term Investments
Derivative
Asset Derivatives Fair Value	0.5
Not Designated as Hedging Instrument | Other Liabilities
Derivative
Liability Derivatives Fair Value	55.6	43.6
Not Designated as Hedging Instrument | Foreign Exchange Contracts | Miscellaneous Long-term Investments
Derivative
Asset Derivatives Fair Value	0
Not Designated as Hedging Instrument | Foreign Exchange Contracts | Other Liabilities
Derivative
Liability Derivatives Fair Value	24.5	27.5
Not Designated as Hedging Instrument | Credit Default Swaps | Miscellaneous Long-term Investments
Derivative
Asset Derivatives Fair Value	0.5
Not Designated as Hedging Instrument | Credit Default Swaps | Other Liabilities
Derivative
Liability Derivatives Fair Value	0	0.2
Not Designated as Hedging Instrument | Embedded Derivative in Modified Coinsurance Arrangement | Miscellaneous Long-term Investments
Derivative
Asset Derivatives Fair Value	0
Not Designated as Hedging Instrument | Embedded Derivative in Modified Coinsurance Arrangement | Other Liabilities
Derivative
Liability Derivatives Fair Value	31.1	15.9
Cash Flow Hedging | Designated as Hedging Instrument | Foreign Exchange Contracts | Miscellaneous Long-term Investments
Derivative
Asset Derivatives Fair Value	25	19.5
Cash Flow Hedging | Designated as Hedging Instrument | Foreign Exchange Contracts | Other Liabilities
Derivative
Liability Derivatives Fair Value	7.9	19.4
Fair Value Hedging | Designated as Hedging Instrument | Miscellaneous Long-term Investments
Derivative
Asset Derivatives Fair Value	5.4
Fair Value Hedging | Designated as Hedging Instrument | Other Liabilities
Derivative
Liability Derivatives Fair Value	5.6
Fair Value Hedging | Designated as Hedging Instrument | Foreign Exchange Contracts | Miscellaneous Long-term Investments
Derivative
Asset Derivatives Fair Value	5.4
Fair Value Hedging | Designated as Hedging Instrument | Foreign Exchange Contracts | Other Liabilities
Derivative
Liability Derivatives Fair Value	0.4
Fair Value Hedging | Designated as Hedging Instrument | Interest Rate Swaps | Miscellaneous Long-term Investments
Derivative
Asset Derivatives Fair Value		0
Fair Value Hedging | Designated as Hedging Instrument | Interest Rate Swaps | Other Liabilities
Derivative
Liability Derivatives Fair Value	$ 5.2	$ 5.1

Derivative Financial Instrume_5

Derivative Financial Instruments Location of Gains and Losses Designated as Hedging Instruments, Consolidated Statements of Income (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Derivative Instruments, Gain (Loss)
Net Investment Income	$ 608.6	$ 619.2	$ 623.6	$ 602.3	$ 619.8	$ 609	$ 620.5	$ 602.4	$ 2,453.7	$ 2,451.7	$ 2,459
Net Realized Investment Gain (Loss)	$ (41.4)	$ 6.7	$ (2.6)	$ (2.2)	$ 11.4	$ 9.8	$ 8.1	$ 11	(39.5)	40.3	24.2
Interest and Debt Expense									167.3	159.9	166
Derivative, Gain (Loss) on Derivative, Net									(0.3)	0.1	1.5
Interest Rate Swaps | Net Investment Income | Designated as Hedging Instrument | Cash Flow Hedging
Derivative Instruments, Gain (Loss)
Net Investment Income									310.3	321.1	337.7
Derivative, Gain (Loss) on Derivative, Net									67.1	60.4	55.7
Interest Rate Swaps | Net Investment Income | Designated as Hedging Instrument | Fair Value Hedging
Derivative Instruments, Gain (Loss)
Net Investment Income									1	4.8	7.1
Derivative, Gain (Loss) on Derivative, Net									(0.5)	(3.2)	(5.3)
Interest Rate Swaps | Net Realized Investment Gain (Loss) | Designated as Hedging Instrument | Cash Flow Hedging
Derivative Instruments, Gain (Loss)
Net Realized Investment Gain (Loss)									0.1	2.5	7.2
Derivative, Gain (Loss) on Derivative, Net									(0.3)	0.2	3.4
Interest Rate Swaps | Net Realized Investment Gain (Loss) | Designated as Hedging Instrument | Fair Value Hedging
Derivative Instruments, Gain (Loss)
Net Realized Investment Gain (Loss)									0.1	(1.7)	(3.1)
Derivative, Gain (Loss) on Derivative, Net									(0.1)	1.7	3.1
Interest Rate Swaps | Interest and Debt Expense | Designated as Hedging Instrument | Cash Flow Hedging
Derivative Instruments, Gain (Loss)
Interest and Debt Expense									38.4	44.9	44.9
Derivative, Gain (Loss) on Derivative, Net									2.3	2.2	2.1
Interest Rate Swaps | Interest and Debt Expense | Designated as Hedging Instrument | Fair Value Hedging
Derivative Instruments, Gain (Loss)
Interest and Debt Expense									14.3	14.3	39.7
Derivative, Gain (Loss) on Derivative, Net									1.8	(0.6)	(4.7)
Foreign Exchange Contracts | Net Investment Income | Designated as Hedging Instrument | Cash Flow Hedging
Derivative Instruments, Gain (Loss)
Net Investment Income									18.1	21.7	23.1
Derivative, Gain (Loss) on Derivative, Net									(0.9)	(1.2)	(0.6)
Foreign Exchange Contracts | Net Investment Income | Designated as Hedging Instrument | Fair Value Hedging
Derivative Instruments, Gain (Loss)
Net Investment Income									0.6
Derivative, Gain (Loss) on Derivative, Net									0.5
Foreign Exchange Contracts | Net Realized Investment Gain (Loss) | Designated as Hedging Instrument | Cash Flow Hedging
Derivative Instruments, Gain (Loss)
Net Realized Investment Gain (Loss)									1.5	8.9	1.5
Derivative, Gain (Loss) on Derivative, Net									(1.5)	(9.2)	(1.4)
Foreign Exchange Contracts | Net Realized Investment Gain (Loss) | Designated as Hedging Instrument | Fair Value Hedging
Derivative Instruments, Gain (Loss)
Net Realized Investment Gain (Loss)									(2.7)
Derivative, Gain (Loss) on Derivative, Net									2.7
Foreign Exchange Contracts | Interest and Debt Expense | Designated as Hedging Instrument | Cash Flow Hedging
Derivative Instruments, Gain (Loss)
Interest and Debt Expense									0	0	0
Derivative, Gain (Loss) on Derivative, Net									0	$ 0	$ 0
Foreign Exchange Contracts | Interest and Debt Expense | Designated as Hedging Instrument | Fair Value Hedging
Derivative Instruments, Gain (Loss)
Interest and Debt Expense									0
Derivative, Gain (Loss) on Derivative, Net									$ 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, 2018	Dec. 31, 2017	Dec. 31, 2016
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in OCI on Derivatives (Effective Portion)	$ 16.8	$ (23.1)	$ (22.3)
Interest Rate Swaps
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in OCI on Derivatives (Effective Portion)	(0.1)	(0.1)	(0.1)
Foreign Exchange Contracts
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in OCI on Derivatives (Effective Portion)	$ 16.9	$ (23)	$ (22.2)

Gains and Losses on Derivatives

Gains and Losses on Derivatives Not Designated as Hedging Instruments (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Derivative Instruments, Gain (Loss)
Net Gain (Loss) on Derivatives	$ 0.3	$ (0.1)	$ (1.5)
Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss)
Net Gain (Loss) on Derivatives	(14.9)	30.7	40.6
Not Designated as Hedging Instrument | Credit Default Swaps
Derivative Instruments, Gain (Loss)
Net Gain (Loss) on Derivatives	(0.3)	(0.4)	(0.9)
Not Designated as Hedging Instrument | Interest Rate Swaps
Derivative Instruments, Gain (Loss)
Net Gain (Loss) on Derivatives	(0.3)	(0.1)	0.4
Not Designated as Hedging Instrument | Foreign Exchange Contracts
Derivative Instruments, Gain (Loss)
Net Gain (Loss) on Derivatives	0.9	0.4	0.2
Not Designated as Hedging Instrument | Embedded Derivative in Modified Coinsurance Arrangement
Derivative Instruments, Gain (Loss)
Net Gain (Loss) on Derivatives	$ (15.2)	$ 30.8	$ 40.9

Derivative Financial Instrume_6

Derivative Financial Instruments - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative
Aggregate fair value of all derivative instruments with credit risk-related contingent features in a liability position	$ 38	$ 52.2
Notional Amount of Derivatives	799.2	904.5	$ 1,052	$ 1,470.3
Approximate amount of net deferred gains on derivative instruments expected to be amortized during the next twelve months	70
Notional Amount Of Derivatives Terminations	241.8	239.6	451.8
Component of Derivative Gain (Loss) Excluded from the Assessment of Hedge Effectiveness	2.5	0
Discontinued Hedge Accounting Due to Instrument No Longer Qualifying as Fair Value Hedge	0	0
Credit Risk Contract | Credit Default Swaps
Derivative
Notional Amount of Derivatives	11	70	70	$ 70
Notional Amount Of Derivatives Terminations	70	0	0
Credit Risk Contract | Credit Default Swaps | Not Designated as Hedging Instrument
Derivative
Notional Amount of Derivatives	11	70
Credit Exposure
Derivative
Credit Exposure on Derivatives	0.9	0
Receive Fixed/Pay Fixed | Interest Rate Swaps | Not Designated as Hedging Instrument
Derivative
Notional Amount of Derivatives	173.7	192.6
Receive Fixed/Pay Fixed | Interest Rate Swaps | Cash Flow Hedging | Designated as Hedging Instrument
Derivative
Notional Amount of Derivatives	286.4	343.9
Receive Fixed/Pay Fixed | Interest Rate Swaps | Fair Value Hedging | Designated as Hedging Instrument
Derivative
Notional Amount of Derivatives	78.1
Receive Variable/Pay Fixed | Interest Rate Swaps
Derivative
Loss on Contract Termination		0.1
Receive Variable/Pay Fixed | Interest Rate Swaps | Not Designated as Hedging Instrument
Derivative
Notional Amount of Derivatives			3.5
Loss on Contract Termination		0.1
Receive Variable/Pay Fixed | Interest Rate Swaps | Fair Value Hedging | Designated as Hedging Instrument
Derivative
Notional Amount of Derivatives		48
Notional Amount Of Derivatives Terminations			24
Loss on Contract Termination			1.2
Receive Fixed/Pay Variable | Interest Rate Swaps
Derivative
Notional Amount of Derivatives	250	250
Receive Fixed/Pay Variable | Interest Rate Swaps | Fair Value Hedging | Designated as Hedging Instrument
Derivative
Notional Amount of Derivatives	$ 250	$ 250
Notional Amount Of Derivatives Terminations			350
Derivative, Amount of Hedged Item			$ 350

Schedule of Accumulated Other C

Schedule of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss)
Balance at Beginning of Year	$ 127.5	$ (51)	$ 16.1
Recognition and Measurement of Financial Assets and Financial Liabilities, Reclassification from AOCI to Retained Earnings	(17.5)
Other Comprehensive Income (Loss) Before Reclassifications, Net of Tax	(910.6)	205.6	(52.5)
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	(13.6)	(27.1)	(14.6)
Total Other Comprehensive Income (Loss)	(924.2)	178.5	(67.1)
Balance at End of Year	(814.2)	127.5	(51)
Net Unrealized Gain (Loss) on Securities
Accumulated Other Comprehensive Income (Loss)
Balance at Beginning of Year	607.8	440.6	204.3
Recognition and Measurement of Financial Assets and Financial Liabilities, Reclassification from AOCI to Retained Earnings	(17.5)
Other Comprehensive Income (Loss) Before Reclassifications, Net of Tax	(920.3)	176.7	226.5
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	17.6	(9.5)	9.8
Total Other Comprehensive Income (Loss)	(902.7)	167.2	236.3
Balance at End of Year	(312.4)	607.8	440.6
Net Gain on Hedges
Accumulated Other Comprehensive Income (Loss)
Balance at Beginning of Year	282.3	327.5	378
Recognition and Measurement of Financial Assets and Financial Liabilities, Reclassification from AOCI to Retained Earnings	0
Other Comprehensive Income (Loss) Before Reclassifications, Net of Tax	16.8	(14.7)	(15.8)
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	(48.5)	(30.5)	(34.7)
Total Other Comprehensive Income (Loss)	(31.7)	(45.2)	(50.5)
Balance at End of Year	250.6	282.3	327.5
Foreign Currency Translation Adjustment
Accumulated Other Comprehensive Income (Loss)
Balance at Beginning of Year	(254.5)	(354)	(173.6)
Recognition and Measurement of Financial Assets and Financial Liabilities, Reclassification from AOCI to Retained Earnings	0
Other Comprehensive Income (Loss) Before Reclassifications, Net of Tax	(50.7)	99.5	(180.4)
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	0	0	0
Total Other Comprehensive Income (Loss)	(50.7)	99.5	(180.4)
Balance at End of Year	(305.2)	(254.5)	(354)
Unrecognized Pension and Postretirement Benefit Costs
Accumulated Other Comprehensive Income (Loss)
Balance at Beginning of Year	(508.1)	(465.1)	(392.6)
Recognition and Measurement of Financial Assets and Financial Liabilities, Reclassification from AOCI to Retained Earnings	0
Other Comprehensive Income (Loss) Before Reclassifications, Net of Tax	43.6	(55.9)	(82.8)
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	17.3	12.9	10.3
Total Other Comprehensive Income (Loss)	60.9	(43)	(72.5)
Balance at End of Year	$ (447.2)	$ (508.1)	$ (465.1)

Schedule of Components of Unrea

Schedule of Components of Unrealized Gain (Loss) on Securities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Change in Components of Net Unrealized Gain on Securities
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, after Tax	$ (2,314.5)	$ 721.7	$ 661.9
Fixed Maturity Securities
Change in Components of Net Unrealized Gain on Securities
Beginning of Year Balance	5,677.3	4,664.6	3,695.7
Accumulated Other Comprehensive Income (Loss), Debt Securities, Available-for-sale, Beginning Balance Adjustment, After-tax	(12.1)
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, after Tax	(2,928.7)	1,012.7	968.9
End of Year Balance	2,736.5	5,677.3	4,664.6
Other Investments
Change in Components of Net Unrealized Gain on Securities
Beginning of Year Balance	14.4	(22.7)	(33.7)
Accumulated Other Comprehensive Income (Loss), Debt Securities, Available-for-sale, Beginning Balance Adjustment, After-tax	(14.4)
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, after Tax	0	37.1	11
End of Year Balance	0	14.4	(22.7)
Deferred Acquisition Costs
Change in Components of Net Unrealized Gain on Securities
Beginning of Year Balance	(51.4)	(38.9)	(29.4)
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, after Tax	23.5	(12.5)	(9.5)
End of Year Balance	(27.9)	(51.4)	(38.9)
Reserve for Future Policy and Contract Benefits
Change in Components of Net Unrealized Gain on Securities
Beginning of Year Balance	(5,094.7)	(4,253.2)	(3,578.4)
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, after Tax	1,874.4	(841.5)	(674.8)
End of Year Balance	(3,220.3)	(5,094.7)	(4,253.2)
Reinsurance Recoverable
Change in Components of Net Unrealized Gain on Securities
Beginning of Year Balance	375.8	321.3	263.2
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, after Tax	(114.4)	54.5	58.1
End of Year Balance	261.4	375.8	321.3
Income Tax
Change in Components of Net Unrealized Gain on Securities
Beginning of Year Balance	(313.6)	(230.5)	(113.1)
Accumulated Other Comprehensive Income (Loss), Debt Securities, Available-for-sale, Beginning Balance Adjustment, After-tax	9
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, after Tax	242.5	(83.1)	(117.4)
End of Year Balance	(62.1)	(313.6)	(230.5)
Net Unrealized Gain (Loss) on Securities
Change in Components of Net Unrealized Gain on Securities
Beginning of Year Balance	607.8	440.6	204.3
Accumulated Other Comprehensive Income (Loss), Debt Securities, Available-for-sale, Beginning Balance Adjustment, After-tax	(17.5)
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, after Tax	(902.7)	167.2	236.3
End of Year Balance	$ (312.4)	$ 607.8	$ 440.6

Schedule of Reclassifications O

Schedule of Reclassifications Out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended											12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018		Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017		Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Other-Than-Temporary Impairment Loss												$ (17.5)	$ (8.1)	$ (30.5)
Net Investment Income	$ 608.6	$ 619.2		$ 623.6	$ 602.3	$ 619.8		$ 609	$ 620.5	$ 602.4		2,453.7	2,451.7	2,459
Interest and Debt Expense												(167.3)	(159.9)	(166)
Other Expenses												(891.2)	(855)	(824.6)
Income Before Income Tax	309.7	(377.8)	[1]	354.8	341.1	345.3	[2]	366.8	361.6	330.3	[3]	627.8	1,404	1,347.7
Income Tax Expense (Benefit)												104.4	409.8	416.3
Net Income	$ 249.1	$ (284.7)	[1]	$ 285.5	$ 273.5	$ 266.9	[2],[4]	$ 252.3	$ 245.1	$ 229.9	[3]	523.4	994.2	931.4
Reclassification out of Accumulated Other Comprehensive Income | Net Unrealized Gain (Loss) on Securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Net Realized Investment Gain (Loss), Excluding Other-Than-Temporary Impairment Loss on Fixed Maturity Securities												(4.8)	22.7	15.3
Other-Than-Temporary Impairment Loss												(17.5)	(8.1)	(30.5)
Income Before Income Tax												(22.3)	14.6	(15.2)
Income Tax Expense (Benefit)												(4.7)	5.1	(5.4)
Net Income												(17.6)	9.5	(9.8)
Reclassification out of Accumulated Other Comprehensive Income | Net Gain on Hedges
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Income Before Income Tax												61.4	46.8	53.3
Income Tax Expense (Benefit)												12.9	16.3	18.6
Net Income												48.5	30.5	34.7
Reclassification out of Accumulated Other Comprehensive Income | Net Gain on Hedges | Interest Rate Swaps
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Net Realized Investment Gain (Loss), Excluding Other-Than-Temporary Impairment Loss on Fixed Maturity Securities												0.2	0.2	3.2
Net Investment Income												65.9	59	54.5
Interest and Debt Expense												(2.1)	(2)	(1.9)
Reclassification out of Accumulated Other Comprehensive Income | Net Gain on Hedges | Foreign Exchange Contracts
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Net Realized Investment Gain (Loss), Excluding Other-Than-Temporary Impairment Loss on Fixed Maturity Securities												(1.5)	(9.2)	(1.4)
Net Investment Income												(1.1)	(1.2)	(1.1)
Reclassification out of Accumulated Other Comprehensive Income | Net Actuarial Loss
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Other Expenses												(22.3)	(20.3)	(16.3)
Reclassification out of Accumulated Other Comprehensive Income | Prior Service Credit
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Other Expenses												0.2	0.7	0.5
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												(22.1)	(19.6)	(15.8)
Income Tax Expense (Benefit)												(4.8)	(6.7)	(5.5)
Net Income												$ (17.3)	$ (12.9)	$ (10.3)
[1]	Third quarter of 2018 reserve increase of $750.8 million before tax and $593.1 million after tax related to long-term care.
[2]	Fourth quarter of 2017 reserve increase of $39.0 million before tax and $25.4 million after tax related to unclaimed death benefits.
[3]	First quarter of 2017 loss from a guaranty fund assessment related to an unaffiliated insurer that was declared insolvent of $20.6 million before tax and $13.4 million after tax.
[4]	Fourth quarter of 2017 net tax benefit of $31.5 million related to the TCJA.

Liability for Unpaid Claims and

Liability for Unpaid Claims and Claims Adjustment Expense (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense
Balance at January 1	$ 23,222	$ 23,249.5	$ 23,796.1
Less Reinsurance Recoverable	2,182	2,163.6	2,064.6
Net Balance at January 1	21,040	21,085.9	21,731.5
Incurred Related to
Current Year	5,832.3	5,422.9	5,243
Paid Related to
Current Year	(2,354.7)	(2,156.9)	(2,035.4)
Prior Years	(4,428.8)	(4,410.9)	(4,451.4)
Total Paid	(6,783.5)	(6,567.8)	(6,486.8)
Net Balance at December 31	20,921.7	21,040	21,085.9
Plus Reinsurance Recoverable	2,227.3	2,182	2,163.6
Balance at December 31	23,149	23,222	23,249.5
Amount Related to Interest
Incurred Related to
Prior Years	1,049.8	1,089.7	1,136.7
Incurred Claims
Incurred Related to
Prior Years	(106.2)	(158.2)	(198.3)
Foreign Currency
Incurred Related to
Prior Years	(110.7)	167.5	(340.2)
Operating Expense
Incurred Related to
Total Incurred	$ 6,665.2	$ 6,521.9	$ 5,841.2

Reconciliation of Policy and Co

Reconciliation of Policy and Contract Benefits and Reserves for Future Policy and Contract Benefits (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Insurance [Abstract]
Policy and Contract Benefits	$ 1,695.7	$ 1,605.2	$ 1,507.9
Reserves for Future Policy and Contract Benefits	44,841.9	45,601.6	44,245.9
Total Policy and Contract Benefits and Reserves for Future Policy and Contract Benefits	46,537.6	47,206.8	45,753.8
Life Reserves for Future Policy and Contract Benefits	8,330.9	8,231.3	8,078.2
Accident and Health Active Life Reserves	11,837.4	10,658.8	10,172.9
Adjustment Related to Unrealized Investment Gains and Losses	3,220.3	5,094.7	4,253.2
Liability for Claims and Claims Adjustment Expense	$ 23,149	$ 23,222	$ 23,249.5	$ 23,796.1

Liability for Unpaid Claims - A

Liability for Unpaid Claims - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Liability for Unpaid Claims and CAE Narrative Information
Long-term Care Reserve Increase, Before Tax	$ 750.8
Long-term Care Reserve Increase, After Tax	593.1
Unclaimed Death Benefit Reserve Increase Before Taxes		$ 39
Operating Segments
Liability for Unpaid Claims and CAE Narrative Information
Unclaimed Death Benefit Reserve Increase Before Taxes	0	39	$ 0
Operating Segments | Unum US | Group Life
Liability for Unpaid Claims and CAE Narrative Information
Unclaimed Death Benefit Reserve Increase Before Taxes		18.5
Operating Segments | Unum US | Voluntary Benefits
Liability for Unpaid Claims and CAE Narrative Information
Unclaimed Death Benefit Reserve Increase Before Taxes		8.1
Operating Segments | Colonial Life | Life Insurance
Liability for Unpaid Claims and CAE Narrative Information
Unclaimed Death Benefit Reserve Increase Before Taxes		$ 12.4
Claim Reserve
Liability for Unpaid Claims and CAE Narrative Information
Long-term Care Reserve Increase, Before Tax	$ 236

Income Tax Expense (Benefit) (D

Income Tax Expense (Benefit) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax [Abstract]
Income Tax Expense	$ 104.4	$ 409.8	$ 416.3
Additional Paid in Capital
Stock-Based Compensation	0	0	(0.3)
Other Comprehensive Income (Loss), Tax
Other Comprehensive Income (Loss), Unrealized Holding Gain on Securities Arising During Period, Tax	(614.2)	328.1	318
Change in Adjustment to Deferred Acquisition Costs and Reserves for Future Policy and Contract Benefits, Net of Reinsurance, Tax Expense	371.7	(245)	(200.6)
Change in Net Gain on Cash Flow Hedges	(8.2)	(24.4)	(25.4)
Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax	(0.6)	0	0
Change in Unrecognized Pension and Postretirement Benefit Costs	17	(8.3)	(34.2)
Total	$ (129.9)	$ 460.2	$ 473.8

Reconciliation of income tax co

Reconciliation of income tax computed at US Federal tax rates (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax [Abstract]
Statutory Income Tax	21.00%	35.00%	35.00%
Foreign Rate Differential, Inclusive of Foreign Rate Changes	(0.30%)	(1.10%)	(2.20%)
U.S. Deferred Tax Liability Remeasurement	0.00%	(7.00%)	0.00%
Deemed Repatriation Tax on Foreign Earnings and Profit (E&P)	1.80%	4.70%	0.00%
Tax Exempt Income	(1.30%)	(0.80%)	(0.80%)
Tax Credits	(2.40%)	(1.50%)	(1.60%)
Policyholder Reserves	(2.40%)	0.00%	0.00%
Other Items, Net	0.20%	(0.10%)	0.50%
Effective Tax	16.60%	29.20%	30.90%

Schedule of deferred income tax

Schedule of deferred income tax assets and liabilities (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Income Tax [Abstract]
Deferred Acquisition Cost	$ 129.7	$ 118.6
Deferred Tax Liabilities for Fixed Assets	56.2	52.8
Deferred Tax Liabilities on Invested Assets	493.4	1,074
Deferred Tax Liabilities, Intangible Assets	24	6.5
Deferred Tax Liability, Other	34.1	35.8
Gross Deferred Tax Liability	737.4	1,287.7
Deferred Tax Asset, Reserves	668.5	908
Deferred Tax Asset, Employee Benefits	179.5	188.7
Deferred Tax Asset, Other	17.7	12.3
Gross Deferred Tax Asset	865.7	1,109
Less: Valuation Allowance	18.4	20.3
Net Deferred Tax Asset	847.3	1,088.7
Deferred Tax Assets, Net	(109.9)
Net Deferred Tax Liability	$ 0	$ 199

Schedule of Income subject to d

Schedule of Income subject to domestic and foreign taxation (Detail) - USD ($) $ in Millions	3 Months Ended											12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	[1]	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	[2]	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	[3]	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax [Abstract]
Income Before Tax, Domestic												$ 492.6	$ 1,289	$ 1,215.8
Income Before Tax, Foreign												135.2	115	131.9
Income Before Income Tax	$ 309.7	$ (377.8)		$ 354.8	$ 341.1	$ 345.3		$ 366.8	$ 361.6	$ 330.3		627.8	1,404	1,347.7
Current Tax Expense, Domestic												194.6	374.9	414.8
Current State and Local Tax Expense (Benefit)												(0.6)	0.4	0.3
Current Tax Expense, Foreign												33.4	26	(29.4)
Income Tax - Current												227.4	401.3	385.7
Deferred Tax Expense (Benefit), Federal												(114.6)	14.2	(14.6)
Deferred State and Local Income Tax Expense (Benefit)												(0.2)	(0.3)	(2.1)
Deferred Tax Expense (Benefit), Foreign												(8.2)	(5.4)	47.3
Income Tax - Deferred												(123)	8.5	30.6
Income Tax Expense												$ 104.4	$ 409.8	$ 416.3
[1]	Third quarter of 2018 reserve increase of $750.8 million before tax and $593.1 million after tax related to long-term care.
[2]	Fourth quarter of 2017 reserve increase of $39.0 million before tax and $25.4 million after tax related to unclaimed death benefits.
[3]	First quarter of 2017 loss from a guaranty fund assessment related to an unaffiliated insurer that was declared insolvent of $20.6 million before tax and $13.4 million after tax.

Unrecognized tax benefits (Deta

Unrecognized tax benefits (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax [Abstract]
Balance at Beginning of Year	$ 1.4	$ 1.5	$ 0.8
Additions to Tax Positions Taken During Prior Years	261.5	0.3	0.7
Unrecognized Tax Benefits, Increase Resulting from Current Period Tax Positions	0	0	0
Settlements with Tax Authorities	0	0	0
Lapse of the Applicable Statute of Limitations	(0.7)	(0.4)	0
Balance at End of Year	262.2	1.4	1.5
Less Tax Attributable to Temporary Items Included Above	(148.2)	0	0
Total Unrecognized Tax Benefits that if Recognized Would Affect the Effective Tax Rate	$ 114	$ 1.4	$ 1.5

Income Tax Additional Informati

Income Tax Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Federal Income Tax Note
Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Change in Tax Rate, Deferred Tax Liability, Provisional Income Tax Benefit		$ 97.9
Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Transition Tax for Accumulated Foreign Earnings, Provisional Income Tax Expense		66.4
Tax Cuts and Jobs Act of 2017, Complete Accounting, Transition Tax for Accumulated Foreign Earnings, Provisional Income Tax Expense	$ 11.5
Tax Cuts and Jobs Act of 2017, Complete Accounting, Undistributed Accumulated Earnings of Foreign Subsidiary for which Unrecognized Deferred Tax Liabilities Have Not Been Recorded	$ 700
Tax Cuts and Jobs Act of 2017, Accounting Complete	true
Additions to Tax Positions Taken During Prior Years	$ 261.5	0.3	$ 0.7
Valuation Allowance on Deferred Tax Assets	18.4	20.3
Income Taxes Paid, Net	139.7	$ 377	$ 384.3
U.S. Federal
Federal Income Tax Note
Operating Loss Carryforwards	$ 6.5
Operating Loss Carryforwards, Expiration Date	Dec. 31, 2022
State and Local Jurisdiction
Federal Income Tax Note
Operating Loss Carryforwards	$ 195
Minimum | State and Local Jurisdiction
Federal Income Tax Note
Operating Loss Carryforwards, Expiration Date	Dec. 31, 2019
Maximum | State and Local Jurisdiction
Federal Income Tax Note
Operating Loss Carryforwards, Expiration Date	Dec. 31, 2038
Subsidiary Return | U.S. Federal
Federal Income Tax Note
Operating Loss Carryforwards	$ 0.7
Tax Year 2017
Federal Income Tax Note
Additions to Tax Positions Taken During Prior Years	$ 261.1

Debt Schedule (Detail)

Debt Schedule (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument
Long-term Debt, Excluding Current Maturities	$ 2,971.3			$ 2,738.4
Debt Instrument, Unamortized Premium (Discount), Net	9.6			9.7
Debt Issuance Costs, Noncurrent, Net	(30.8)			(24.4)
Current Maturities of Long-term Debt	0			199.9
Debt Issuance Costs, Current, Net	0			(0.1)
Long-term Debt	2,971.3			2,938.3
Fair Value Hedge Adjustment, LT Debt
Debt Instrument
Long-term Debt, Excluding Current Maturities	(5.1)			(4.5)
Secured Notes Issued in 2007 | Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	$ 140			200
Interest Rate Terms	Variable
Year of Maturity	Dec. 31, 2037
Notes Issued in 1998 with 2028 Maturity Date | Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	$ 365.8			365.8
Interest Rate Terms	6.750 - 7.250%
Year of Maturity	Dec. 31, 2028
Notes Issued in 1998 with 2028 Maturity Date | Senior Notes | Minimum
Debt Instrument
Stated Interest Rate of Debt			6.75%
Notes Issued in 1998 with 2028 Maturity Date | Senior Notes | Maximum
Debt Instrument
Stated Interest Rate of Debt			7.25%
Notes Issued in 2002 | Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	$ 39.5			39.5
Stated Interest Rate of Debt			7.375%
Year of Maturity	Dec. 31, 2032
Notes Issued in 2010 | Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	$ 400			400
Stated Interest Rate of Debt			5.625%
Year of Maturity	Dec. 31, 2020
Notes Payable due 2042 | Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	$ 500			500
Stated Interest Rate of Debt			5.75%
Year of Maturity	Dec. 31, 2042
Notes Issued in 2014 | Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	$ 350			350
Stated Interest Rate of Debt			4.00%
Year of Maturity	Dec. 31, 2024
Notes Issued in 2015 | Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	$ 275			275
Stated Interest Rate of Debt			3.875%
Year of Maturity	Dec. 31, 2025
Notes Issued in 2016 | Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	$ 350			350
Stated Interest Rate of Debt			3.00%
Year of Maturity	May 15, 2021
Notes Issued 1990 to 1996 | Medium-term Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	$ 50.8			50.8
Interest Rate Terms	7.000 - 7.190%
Debt Instrument, Maturity Date Range, Start	Dec. 31, 2023
Debt Instrument, Maturity Date Range, End	Dec. 31, 2028
Notes Issued 1990 to 1996 | Medium-term Notes | Minimum
Debt Instrument
Stated Interest Rate of Debt			7.00%
Notes Issued 1990 to 1996 | Medium-term Notes | Maximum
Debt Instrument
Stated Interest Rate of Debt			7.19%
Notes Issued in 1998 with 2038 Maturity Date | Junior Subordinated Debt
Debt Instrument
Long-term Debt, Excluding Current Maturities	$ 226.5			226.5
Stated Interest Rate of Debt		7.405%	7.405%
Year of Maturity	Dec. 31, 2038
Notes Issued in 2018 with a 2058 Maturity Date | Junior Subordinated Debt
Debt Instrument
Long-term Debt, Excluding Current Maturities	$ 300			0
Stated Interest Rate of Debt			6.25%
Year of Maturity	Dec. 31, 2058
Notes Issued in 1998 with 2018 Maturity Date | Senior Notes
Debt Instrument
Current Maturities of Long-term Debt	$ 0			$ 200
Stated Interest Rate of Debt			7.00%
Year of Maturity	Dec. 31, 2018

Debt - Additional Information D

Debt - Additional Information Domain (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2007	Dec. 31, 1998	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2015
Debt Narrative Detail Information
Repayments of Principal in 2020						$ 400
Repayments of Principal in 2021						350
Repayments of Principal in 2023						2
Repayments of Principal Thereafter						2,245.6
Current Maturities of Long-term Debt		$ 199.9				0
Long-term Debt, Excluding Current Maturities		2,738.4				2,971.3
Notional Amount of Derivatives		904.5	$ 1,052			799.2			$ 1,470.3
Unum Group Percentage Ownership of Provident Financing Trust							100.00%
Interest Paid, Including Capitalized Interest, Operating and Investing Activities	$ 167.3	154.4	153.6
Line of Credit Facility, Maximum Borrowing Capacity						400
Line Of Credit Facility Maximum Borrowing Capacity If Requested						600
Letters of Credit Outstanding		2.1				2.1
Amount Outstanding on Line of Credit		0				0
Secured Notes acquired 2016 | Long-term Debt
Debt Narrative Detail Information
Extinguishment of Debt, Amount	3.4
Notes Issued in 2018 with a 2058 Maturity Date | Junior Subordinated Debt
Debt Narrative Detail Information
Stated Interest Rate of Debt								6.25%
Proceeds from Issuance of Debt	$ 300
Long-term Debt, Excluding Current Maturities		0				300
Notes Issued in 1998 with 2038 Maturity Date | Junior Subordinated Debt
Debt Narrative Detail Information
Proceeds from Issuance of Senior Long-term Debt					$ 300
Stated Interest Rate of Debt							7.405%	7.405%
Long-term Debt, Excluding Current Maturities		226.5				226.5
Liquidation value per capital security	$ 1,000
Northwind Holdings LLC
Debt Narrative Detail Information
Proceeds from Issuance of Senior Long-term Debt				$ 800
Basis Spread on LIBOR	0.78%
Debt service coverage account (DSCA)						73.8
Periodic Principal Payments	$ 60	60	$ 64
Receive Fixed/Pay Variable | Interest Rate Swaps
Debt Narrative Detail Information
Notional Amount of Derivatives		250				$ 250
Receive Variable/Pay Fixed | Interest Rate Swaps
Debt Narrative Detail Information
Loss on Contract Termination		$ 0.1

Employee Benefit Plans Change i

Employee Benefit Plans Change in Projected Benefit Obligation Amount (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Other Postretirement Benefit Plans
Defined Benefit Plan, Change in Benefit Obligation
Benefit Obligation at Beginning of Year	$ 139.5	$ 147.9
Service Cost	0	0	$ 0
Interest Cost	4.9	5.9	7.2
Plan Participant Contributions	0.2	0.2
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	(7.6)	(4.2)
Benefits and Expenses Paid	(11.1)	(10.3)
Plan Amendments	0	0
Change in Foreign Exchange Rates	0	0
Benefit Obligation at End of Year	125.9	139.5	147.9
Defined Benefit Plan, Change in Fair Value of Plan Assets
Fair Value of Plan Assets at Beginning of Year	10.5	10.8
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	0.1	0.1
Employer Contributions to Defined Benefit Plan	10.4	9.7
Plan Participant Contributions	0.2	0.2
Benefits and Expenses Paid	(11.1)	(10.3)
Effect of Foreign Exchange Rates on Plan Assets	0	0
Fair Value of Plan Assets at End of Year	10.1	10.5	10.8
Funded Status of Plan	115.8	129
Domestic Plan
Defined Benefit Plan, Change in Fair Value of Plan Assets
Fair Value of Plan Assets at Beginning of Year	1,575
Fair Value of Plan Assets at End of Year	1,456.8	1,575
Domestic Plan | Pension Plan
Defined Benefit Plan, Change in Benefit Obligation
Benefit Obligation at Beginning of Year	2,136.9	1,955.3
Service Cost	9.1	7.9	7
Interest Cost	79.8	84.5	85.2
Plan Participant Contributions	0	0
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	(210.3)	159.3
Benefits and Expenses Paid	(82.2)	(77.7)
Plan Amendments	0	7.6
Change in Foreign Exchange Rates	0	0
Benefit Obligation at End of Year	1,933.3	2,136.9	1,955.3
Accumulated Benefit Obligation	1,933.3	2,136.9
Defined Benefit Plan, Change in Fair Value of Plan Assets
Fair Value of Plan Assets at Beginning of Year	1,582.6	1,454.1
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	(53.6)	198.5
Employer Contributions to Defined Benefit Plan	8.1	7.7
Plan Participant Contributions	0	0
Benefits and Expenses Paid	(82.2)	(77.7)
Effect of Foreign Exchange Rates on Plan Assets	0	0
Fair Value of Plan Assets at End of Year	1,454.9	1,582.6	1,454.1
Funded Status of Plan	478.4	554.3
Foreign Plan
Defined Benefit Plan, Change in Fair Value of Plan Assets
Fair Value of Plan Assets at Beginning of Year	253.5
Fair Value of Plan Assets at End of Year	217	253.5
Foreign Plan | Pension Plan
Defined Benefit Plan, Change in Benefit Obligation
Benefit Obligation at Beginning of Year	243.8	223
Service Cost	0	0	0
Interest Cost	5.9	6.2	7
Plan Participant Contributions	0	0
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	(18.9)	1.7
Benefits and Expenses Paid	(7.3)	(8.3)
Plan Amendments	0.3	0
Change in Foreign Exchange Rates	(12.8)	21.2
Benefit Obligation at End of Year	211	243.8	223
Accumulated Benefit Obligation	205	234.3
Defined Benefit Plan, Change in Fair Value of Plan Assets
Fair Value of Plan Assets at Beginning of Year	253.5	228.4
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	(16)	11.6
Employer Contributions to Defined Benefit Plan	0	0
Plan Participant Contributions	0	0
Benefits and Expenses Paid	(7.3)	(8.3)
Effect of Foreign Exchange Rates on Plan Assets	(13.2)	21.8
Fair Value of Plan Assets at End of Year	217	253.5	$ 228.4
Funded Status of Plan	$ (6)	$ (9.7)

Employee Benefit Plans Amounts

Employee Benefit Plans Amounts Recognized in Balance Sheet (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Other Postretirement Benefit Plans
Defined Benefit Plans and Other Postretirement Benefit Plans
Current Pension Liability	$ 1.6	$ 1.2
Noncurrent Pension Liability	114.2	127.8
Noncurrent Pension Asset	0	0
Funded Status of Plan	115.8	129
Net Actuarial Gain (Loss) in Balance Sheet	20.9	13.7
Prior Service Credit in Balance Sheet	3.3	3.5
Pension Recognized in Balance Sheet, Gross of Deferred Tax	24.2	17.2
Pension Deferred Tax Asset in Balance Sheet	3.2	4.7
Pension Recognized in Balance Sheet, Net of Deferred Tax	27.4	21.9	$ 19.3
Domestic Plan | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans
Current Pension Liability	7.3	7.2
Noncurrent Pension Liability	471.1	547.1
Noncurrent Pension Asset	0	0
Funded Status of Plan	478.4	554.3
Net Actuarial Gain (Loss) in Balance Sheet	(672.6)	(746.4)
Prior Service Credit in Balance Sheet	(0.7)	(0.7)
Pension Recognized in Balance Sheet, Gross of Deferred Tax	(673.3)	(747.1)
Pension Deferred Tax Asset in Balance Sheet	236	251.8
Pension Recognized in Balance Sheet, Net of Deferred Tax	(437.3)	(495.3)	(451.3)
Foreign Plan | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans
Current Pension Liability	0	0
Noncurrent Pension Liability	0	0
Noncurrent Pension Asset	(6)	(9.7)
Funded Status of Plan	(6)	(9.7)
Net Actuarial Gain (Loss) in Balance Sheet	(48.9)	(46.3)
Prior Service Credit in Balance Sheet	(0.3)	0
Pension Recognized in Balance Sheet, Gross of Deferred Tax	(49.2)	(46.3)
Pension Deferred Tax Asset in Balance Sheet	11.9	11.6
Pension Recognized in Balance Sheet, Net of Deferred Tax	$ (37.3)	$ (34.7)	$ (33.1)

Employee Benefit Plans Amount_2

Employee Benefit Plans Amounts Recognized in Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Other Postretirement Benefit Plans
Defined Benefit Plans and Other Postretirement Benefit Plans
Pension Recognized in Balance Sheet, Net of Deferred Tax, Beginning of Year	$ 21.9	$ 19.3
Amortization of Net Actuarial Loss	0	0	$ 0
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, before Tax	7.2	3.6
Amortization of Prior Service Cost (Credit)	(0.2)	(0.4)	(0.2)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising from Plan Amendment, before Tax	0	0
Change in Unrecognized Pension and Postretirement Benefit Costs, Tax Expense	(1.5)	(0.6)
Pension Recognized in Balance Sheet, Net of Deferred Tax, End of Year	27.4	21.9	19.3
Domestic Plan | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans
Pension Recognized in Balance Sheet, Net of Deferred Tax, Beginning of Year	(495.3)	(451.3)
Amortization of Net Actuarial Loss	21.7	19.6	16.2
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, before Tax	52.1	(63.9)
Amortization of Prior Service Cost (Credit)	0	(0.3)	(0.3)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising from Plan Amendment, before Tax	0	(7.6)
Change in Unrecognized Pension and Postretirement Benefit Costs, Tax Expense	(15.8)	8.2
Pension Recognized in Balance Sheet, Net of Deferred Tax, End of Year	(437.3)	(495.3)	(451.3)
Foreign Plan | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans
Pension Recognized in Balance Sheet, Net of Deferred Tax, Beginning of Year	(34.7)	(33.1)
Amortization of Net Actuarial Loss	0.6	0.7	0.1
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, before Tax	(3.2)	(3)
Amortization of Prior Service Cost (Credit)	0	0	0
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising from Plan Amendment, before Tax	(0.3)	0
Change in Unrecognized Pension and Postretirement Benefit Costs, Tax Expense	0.3	0.7
Pension Recognized in Balance Sheet, Net of Deferred Tax, End of Year	$ (37.3)	$ (34.7)	$ (33.1)

Employee Benefit Plans US Pensi

Employee Benefit Plans US Pension Assets, Fair Value Measurement by Input Level (Details) - Domestic Plan - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	$ 1,456.8	$ 1,575
Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	315.5	325.7
Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	316.9	353.7
Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	824.4	895.6
U.S. Large Cap
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	83	103.3
U.S. Large Cap | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
U.S. Large Cap | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
U.S. Large Cap | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
U.S. Large Cap | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	83	103.3
U.S. Small Cap
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	18.9	45.2
U.S. Small Cap | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	18.9	45.2
U.S. Small Cap | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
U.S. Small Cap | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
U.S. Small Cap | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Global
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	290.3	325.9
Global | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Global | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Global | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Global | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	290.3	325.9
International
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	24.6	35.7
International | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
International | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
International | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
International | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	24.6	35.7
Emerging Markets
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	44.1	61.5
Emerging Markets | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Emerging Markets | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Emerging Markets | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Emerging Markets | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	44.1	61.5
U.S. Government and Agencies
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	257.4	260.4
U.S. Government and Agencies | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	257.4	248.5
U.S. Government and Agencies | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	11.9
U.S. Government and Agencies | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
U.S. Government and Agencies | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Corporate
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	311.2	335.5
Corporate | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Corporate | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	311.2	335.5
Corporate | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Corporate | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
State and Municipal Securities
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	5.7	6.3
State and Municipal Securities | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
State and Municipal Securities | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	5.7	6.3
State and Municipal Securities | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
State and Municipal Securities | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Opportunistic Credits
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	192	193.3
Opportunistic Credits | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Opportunistic Credits | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Opportunistic Credits | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Opportunistic Credits | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	192	193.3
Real Estate
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	102.8	96.1
Real Estate | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Real Estate | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Real Estate | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Real Estate | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	102.8	96.1
Private Equity Direct Investments
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	53.5	45.1
Private Equity Direct Investments | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Private Equity Direct Investments | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Private Equity Direct Investments | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Private Equity Direct Investments | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	53.5	45.1
Private Equity Funds of Funds
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	34	34.5
Private Equity Funds of Funds | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Private Equity Funds of Funds | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Private Equity Funds of Funds | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Private Equity Funds of Funds | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	34	34.5
Hedge Funds of Funds
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0.1	0.2
Hedge Funds of Funds | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Hedge Funds of Funds | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Hedge Funds of Funds | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Hedge Funds of Funds | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0.1	0.2
Cash Equivalents
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	39.2	32
Cash Equivalents | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	39.2	32
Cash Equivalents | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Cash Equivalents | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	0	0
Cash Equivalents | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure
Fair Value of Plan Assets	$ 0	$ 0

Employee Benefit Plans UK Pensi

Employee Benefit Plans UK Pension Assets, Fair Value Measurement by Input Level (Details) - Foreign Plan - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	$ 217	$ 253.5
Fair Value, Inputs, Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	84	98.8
Fair Value, Inputs, Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	0	0
Fair Value, Inputs, Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	0	0
Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	133	154.7
Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	217	253.5	$ 228.4
Diversified Growth Assets
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	133	154.7
Diversified Growth Assets | Fair Value, Inputs, Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	0	0
Diversified Growth Assets | Fair Value, Inputs, Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	0	0
Diversified Growth Assets | Fair Value, Inputs, Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	0	0
Diversified Growth Assets | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	133	154.7
Fixed Interest and Index-linked Securities
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	81.3	98.4
Fixed Interest and Index-linked Securities | Fair Value, Inputs, Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	81.3	98.4
Fixed Interest and Index-linked Securities | Fair Value, Inputs, Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	0	0
Fixed Interest and Index-linked Securities | Fair Value, Inputs, Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	0	0
Fixed Interest and Index-linked Securities | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	0	0
Cash Equivalents
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	2.7	0.4
Cash Equivalents | Fair Value, Inputs, Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	2.7	0.4
Cash Equivalents | Fair Value, Inputs, Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	0	0
Cash Equivalents | Fair Value, Inputs, Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	0	0
Cash Equivalents | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	$ 0	$ 0

Employee Benefit Plans OPEB Pla

Employee Benefit Plans OPEB Plan Assets, Fair Value Measurements by Input Level (Details) - Other Postretirement Benefit Plans - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plans and Other Postretirement Benefit Plans
Life Settlement Contracts, Fair Value Method, Face Value	$ 10.1	$ 10.5
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	$ 10.1	$ 10.5

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, 2018	Dec. 31, 2017
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Plan Participant Contributions	$ 0.2	$ 0.2
Defined Benefit Plan, Plan Assets, Benefits Paid	11.1	10.3
Fair Value, Inputs, Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Assets Measured with Unobservable Inputs, Beginning Balance	10.5	10.8
Actual Return on Plan Assets Still Held	0.1	0.1
Plan Participant Contributions	10.6	9.9
Defined Benefit Plan, Plan Assets, Benefits Paid	11.1	10.3
Assets Measured with Unobservable Inputs, Ending Balance	$ 10.1	$ 10.5

Employee Benefit Plans Measurem

Employee Benefit Plans Measurement Assumptions (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Other Postretirement Benefit Plans
Defined Benefit Plans and Other Postretirement Benefit Plans
Discount Rate Assumptions Used Calculating Benefit Obligation	4.40%	3.70%
Discount Rate Assumptions Used Calculating Net Periodic Benefit Cost	3.70%	4.20%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets	5.75%	5.75%
Domestic Plan | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans
Discount Rate Assumptions Used Calculating Benefit Obligation	4.40%	3.80%
Discount Rate Assumptions Used Calculating Net Periodic Benefit Cost	3.80%	4.40%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets	6.75%	7.25%
Foreign Plan | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans
Discount Rate Assumptions Used Calculating Benefit Obligation	2.90%	2.50%
Rate of Compensation Increase Assumptions Used Calculating Benefit Obligation	3.70%	3.70%
Discount Rate Assumptions Used Calculating Net Periodic Benefit Cost	2.50%	2.70%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets	3.90%	3.90%
Rate of Compensation Increase Assumptions Used Calculating Net Periodic Benefit Cost	3.70%	3.80%

Employee Benefit Plans Net Peri

Employee Benefit Plans Net Periodic Benefit Cost (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Other Postretirement Benefit Plans
Defined Benefit Plans and Other Postretirement Benefit Plans
Service Cost	$ 0	$ 0	$ 0
Interest Cost	4.9	5.9	7.2
Expected Return on Plan Assets	(0.6)	(0.6)	(0.6)
Amortization of Net Actuarial Loss	0	0	0
Amortization of Prior Service Cost (Credit)	(0.2)	(0.4)	(0.2)
Plan Amendment, Other Costs	0	0	0.9
Net Periodic Benefit Cost	4.1	4.9	7.3
Domestic Plan | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans
Service Cost	9.1	7.9	7
Interest Cost	79.8	84.5	85.2
Expected Return on Plan Assets	(104.5)	(103.1)	(102.8)
Amortization of Net Actuarial Loss	21.7	19.6	16.2
Amortization of Prior Service Cost (Credit)	0	(0.3)	(0.3)
Plan Amendment, Other Costs	0	0	0
Net Periodic Benefit Cost	6.1	8.6	5.3
Foreign Plan | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans
Service Cost	0	0	0
Interest Cost	5.9	6.2	7
Expected Return on Plan Assets	(8.9)	(8.8)	(10)
Amortization of Net Actuarial Loss	0.6	0.7	0.1
Amortization of Prior Service Cost (Credit)	0	0	0
Plan Amendment, Other Costs	0	0	0
Net Periodic Benefit Cost	$ (2.4)	$ (1.9)	$ (2.9)

Employee Benefit Plans Expected

Employee Benefit Plans Expected Benefit Payments (Details) $ in Millions	Dec. 31, 2018USD ($)
Other Postretirement Benefit Plans
Defined Benefit Plans and Other Postretirement Benefit Plans
Benefit Payments in Year One	$ 12.1
Prescription Drug Subsidy Receipts in Year One	0.2
Net OPEB Payments in Year One	11.9
Benefit Payments in Year Two	11.7
Prescription Drug Subsidy Receipts in Year Two	0.2
Net OPEB Payments in Year Two	11.5
Benefit Payments in Year Three	11.2
Prescription Drug Subsidy Receipts in Year Three	0.1
Net OPEB Payments in Year Three	11.1
Benefit Payments in Year Four	10.7
Prescription Drug Subsidy Receipts in Year Four	0.2
Net OPEB Payments in Year Four	10.5
Benefit Payments in Year Five	10.1
Prescription Drug Subsidy Receipts in Year Five	0.1
Net OPEB Payments in Year Five	10
Benefit Payments in Five Fiscal Years Thereafter	43.7
Prescription Drug Subsidy Receipts in Five Fiscal Years Thereafter	0.4
Net OPEB Payments in Five Fiscal Years Thereafter	43.3
Domestic Plan | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans
Benefit Payments in Year One	77.1
Benefit Payments in Year Two	80.2
Benefit Payments in Year Three	83.8
Benefit Payments in Year Four	87.2
Benefit Payments in Year Five	90.9
Benefit Payments in Five Fiscal Years Thereafter	513.7
Foreign Plan | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans
Benefit Payments in Year One	5.3
Benefit Payments in Year Two	5.3
Benefit Payments in Year Three	5.6
Benefit Payments in Year Four	5.9
Benefit Payments in Year Five	6.4
Benefit Payments in Five Fiscal Years Thereafter	$ 39.4

Employee Benefit Plans - Additi

Employee Benefit Plans - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2018USD ($)Rate	Dec. 31, 2018GBP (£)Rate	Dec. 31, 2017USD ($)Rate	Dec. 31, 2016USD ($)
Pension and Other Postretirement Benefits Disclosure
Health Care Cost Trend Rate Assumed for Next Fiscal Year | Rate	7.00%		7.00%
Ultimate Health Care Cost Trend Rate | Rate	5.00%
Defined Benefit Plan, Year Health Care Cost Trend Rate Reaches Ultimate Trend Rate	2,024	2,024
Effect of One Percentage Point Increase on Accumulated Postretirement Benefit Obligation	$ 600,000
Effect of One Percentage Point Decrease on Accumulated Postretirement Benefit Obligation	(500,000)
Future Amortization of Actuarial Gain (Loss)	18,400,000
Future Amortization of Prior Service Cost (Credit)	200,000
Other Postretirement Benefit Plans
Pension and Other Postretirement Benefits Disclosure
Plan Amendments	0		$ 0
Investment Level 3 Transfers Into	0		0
Investment Level 3 Transfers Out of	$ 0		$ 0
Interest Rate During Period	4.73%	4.73%	4.76%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets	5.75%	5.75%	5.75%
Domestic Plan | Pension Plan
Pension and Other Postretirement Benefits Disclosure
Plan Amendments	$ 0		$ 7,600,000
Average Remaining Life Expectancy of Plan Participants	24 years	24 years
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets	6.75%	6.75%	7.25%
Retirement Benefits, Description	We had no regulatory contribution requirements for our U.S. qualified defined benefit plan in 2018	We had no regulatory contribution requirements for our U.S. qualified defined benefit plan in 2018
Domestic Plan | Other Postretirement Benefit Plans
Pension and Other Postretirement Benefits Disclosure
Matching Contribution Percent of Employees' Gross Pay | Rate	5.00%	5.00%
Employer Discretionary Contribution Percentage of earnings | Rate	4.50%	4.50%
Cost Recognized	$ 72,700,000		$ 78,400,000	$ 72,200,000
Domestic Plan | Equity Securities | Pension Plan
Pension and Other Postretirement Benefits Disclosure
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	36.00%
Domestic Plan | Fixed Maturity Securities | Pension Plan
Pension and Other Postretirement Benefits Disclosure
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	40.00%
Domestic Plan | Alternative Investments | Pension Plan
Pension and Other Postretirement Benefits Disclosure
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	24.00%
Domestic Plan | Minimum | Private Equity Funds of Funds | Pension Plan
Pension and Other Postretirement Benefits Disclosure
Private Equity Partnership Future Liquidation Term	5 years	5 years
Domestic Plan | Maximum | Private Equity Funds of Funds | Pension Plan
Pension and Other Postretirement Benefits Disclosure
Private Equity Partnership Future Liquidation Term	8 years	8 years
Foreign Plan | Pension Plan
Pension and Other Postretirement Benefits Disclosure
Plan Amendments	$ 300,000		$ 0
Average Remaining Life Expectancy of Plan Participants	31 years	31 years
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets	3.90%	3.90%	3.90%
Payment for Pension Benefits	$ 0
Foreign Plan | Other Postretirement Benefit Plans
Pension and Other Postretirement Benefits Disclosure
Matching Contribution Percent of Employees' Gross Pay	5.00%	5.00%
Employer Discretionary Contribution Percentage of earnings	6.00%	6.00%
Employer Matching Contribution for Every Pound on the First One Percent of Employee Contributions | £		£ 2
Employee Contribution Percentage Received 2-for-1 Employer Match	1.00%	1.00%
Cost Recognized	$ 4,200,000		$ 4,200,000	$ 4,900,000
Foreign Plan | Interest Rate Contract | Pension Plan
Pension and Other Postretirement Benefits Disclosure
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	35.00%
Foreign Plan | Diversified Growth Assets | Pension Plan
Pension and Other Postretirement Benefits Disclosure
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	65.00%

Basic and Diluted Earnings Per

Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended											12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	[1]	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	[2],[3]	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	[4]	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Numerator
Net Income	$ 249.1	$ (284.7)		$ 285.5	$ 273.5	$ 266.9		$ 252.3	$ 245.1	$ 229.9		$ 523.4	$ 994.2	$ 931.4
Denominator
Weighted Average Common Shares - Basic												219,635,600	226,492,400	235,445,700
Dilution for Assumed Exercises of Stock Options and Nonvested Stock Awards												423,000	842,800	533,500
Weighted Average Common Shares - Assuming Dilution												220,058,600	227,335,200	235,979,200
Net Income Per Common Share
Basic	$ 1.15	$ (1.30)		$ 1.29	$ 1.23	$ 1.19		$ 1.12	$ 1.08	$ 1		$ 2.38	$ 4.39	$ 3.96
Assuming Dilution	$ 1.15	$ (1.30)		$ 1.29	$ 1.23	$ 1.19		$ 1.12	$ 1.07	$ 1		$ 2.38	$ 4.37	$ 3.95
[1]	Third quarter of 2018 reserve increase of $750.8 million before tax and $593.1 million after tax related to long-term care.
[2]	Fourth quarter of 2017 net tax benefit of $31.5 million related to the TCJA.
[3]	Fourth quarter of 2017 reserve increase of $39.0 million before tax and $25.4 million after tax related to unclaimed death benefits.
[4]	First quarter of 2017 loss from a guaranty fund assessment related to an unaffiliated insurer that was declared insolvent of $20.6 million before tax and $13.4 million after tax.

Treasury Stock Transactions (De

Treasury Stock Transactions (Details) - USD ($) shares in Millions, $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Equity, Class of Treasury Stock
Expiration Date of Share Repurchase Program Authorized in May 2017		Nov. 24, 2019
Number of Treasury Shares Repurchased		8.7	8.2	11.9
Cost of Shares Repurchased	[1]	$ 350.7	$ 400.4	$ 403.3
Commission Paid on Stock Repurchases		0.7	$ 0.3	$ 0.2
Repurchase Program Authorized in May 2018
Equity, Class of Treasury Stock
Authorized Amount of Treasury Share Repurchases Under Stock Repurchase Program		750
Remaining Amount of Treasury Share Repurchases Authorized Under Stock Repurchase Program		500
Repurchase Program Authorized in May 2017
Equity, Class of Treasury Stock
Authorized Amount of Treasury Share Repurchases Under Stock Repurchase Program		750
Remaining Amount of Treasury Share Repurchases Authorized Under Stock Repurchase Program		0
Repurchase Program Authorized in May 2016
Equity, Class of Treasury Stock
Authorized Amount of Treasury Share Repurchases Under Stock Repurchase Program		750
Remaining Amount of Treasury Share Repurchases Authorized Under Stock Repurchase Program		$ 0
[1]	Includes commissions of $0.7 million, $0.3 million, and $0.2 million for the years ended December 31, 2018, 2017, and 2016, respectively.

Stockholders' Equity and Earn_3

Stockholders' Equity and Earnings Per Common Share - Additional Information (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Stockholders Equity and Earnings Per Common Share Additional Information [Abstract]
Exercise Price Floor on Outstanding Stock Options	$ 23.35
Exercise Price Ceiling on Outstanding Stock Options	26.29
Outstanding Restricted Stock Unit Grant Prices Lower Limit	27.85
Outstanding Restricted Stock Unit Grant Prices Upper Limit	55.26
Outstanding Performance Share Unit Awards Grant Price Range Lower Limit	27.85
Outstanding Performance Share Unit Awards Grant Price Range Upper Limit	$ 49.86
Antidilutive Securities Excluded from Computation of Earnings Per Share	600,000	300,000	400,000
Authorized Shares of Preferred Stock	25,000,000
Par Value Per Share of Preferred Stock	$ 0.10
Issued Shares of Preferred Stock	0

Stock-Based Compensation - Acti

Stock-Based Compensation - Activity for PSUs Classified as Equity (Details) - Performance Share Units - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares
Shares Outstanding Beginning Balance	331
Shares Granted	255
Shares Vested	(301)
Shares Forfeited	(2)
Shares Outstanding Ending Balance	283	331
Weighted Average Grant Date Fair Value at Beginning of Period	$ 37.62
Weighted Average Grant Date Fair Value of Shares Granted	44.19	$ 51.37	$ 28.41
Weighted Average Grant Date Fair Value of Shares Vested	30.18
Weighted Average Grant Date Fair Value of Shares Forfeited	46.79
Weighted Average Grant Date Fair Value at End of Period	$ 51.33	$ 37.62

Stock-Based Compensation - Valu

Stock-Based Compensation - Valuation Assumptions on PSU Grants (Details) - Performance Share Units	12 Months Ended
	Dec. 31, 2018Rate	Dec. 31, 2017Rate	Dec. 31, 2016Rate
Share-based Compensation Arrangement by Share-based Payment Award
Expected Volatility Rate	24.00%	24.00%	22.00%
Expected Life	3 years	3 years	3 years
Risk Free Interest Rate	2.32%	1.52%	0.88%

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, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares
Shares Outstanding Beginning Balance	871
Shares Granted	496
Shares Vested	(486)
Shares Forfeited	(54)
Shares Outstanding Ending Balance	827	871
Weighted Average Grant Date Fair Value at Beginning of Period	$ 38.75
Weighted Average Grant Date Fair Value of Shares Granted	47.76	$ 48.92	$ 28.80
Weighted Average Grant Date Fair Value of Shares Vested	37.32
Weighted Average Grant Date Fair Value of Shares Forfeited	44.65
Weighted Average Grant Date Fair Value at End of Period	$ 44.62	$ 38.75

Stock option activity (Details)

Stock option activity (Details) - Stock Options $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding
Shares Outstanding at Beginning of Period | shares	124
Shares Exercised | shares	(19)
Shares Outstanding at End of Period | shares	105
Shares Exercisable | shares	105
Weighted Average Exercise Price of Shares Outstanding at Beginning of Period | $ / shares	$ 23.86
Weighted Average Exercise Price of Shares Exercised | $ / shares	20.78
Weighted Average Exercise Price of Shares Outstanding at End of Period | $ / shares	24.41
Weighted Average Exercise Price of Exercisable Shares | $ / shares	$ 24.41
Weighted Average Remaining Contractual Term of Outstanding Options	1 year 5 months
Weighted Average Remaining Contractual Term of Exercisable Options	1 year 5 months
Options Outstanding, Intrinsic Value | $	$ 0.5
Options, Exercisable, Intrinsic Value | $	$ 0.5

Intrinsic Value of Options Exer

Intrinsic Value of Options Exercised and Fair Value of Options Vested (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award
Intrinsic Value of Options Exercised	$ 0.7	$ 10	$ 3.4
Fair Value of Options Vested	$ 0	$ 0	$ 0.1

Stock-Based Compensation Expens

Stock-Based Compensation Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award
Allocated Share-based Compensation Expense, Before Tax	$ 26.3	$ 29.5	$ 21.9
Allocated Share-based Compensation Expense, Net of Tax	20.9	19.5	14.4
Performance Share Units
Share-based Compensation Arrangement by Share-based Payment Award
Allocated Share-based Compensation Expense, Before Tax	6.8	11.5	6.6
Restricted Stock Units and Cash-Settled Awards
Share-based Compensation Arrangement by Share-based Payment Award
Allocated Share-based Compensation Expense, Before Tax	19	17.5	14.9
Other Awards
Share-based Compensation Arrangement by Share-based Payment Award
Allocated Share-based Compensation Expense, Before Tax	$ 0.5	$ 0.5	$ 0.4

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award
Cash Received Under Share-based Payment Arrangements	$ 4.6	$ 10.8	$ 8.5
Stock Incentive Plan 2017
Share-based Compensation Arrangement by Share-based Payment Award
Number of Shares Authorized	17,000,000
Number of Shares for Each Full Value Award	1.76
Total Duration of the Stock Incentive Plan	8 years
Award Vesting Period	3 years
Number of Shares Available for Grant	15,700,000
Stock Incentive Plan 2012
Share-based Compensation Arrangement by Share-based Payment Award
Number of Shares Authorized	20,000,000
Number of Shares for Each Full Value Award	1.76
Total Duration of the Stock Incentive Plan	8 years
Award Vesting Period	3 years
Stock Incentive Plan 2007
Share-based Compensation Arrangement by Share-based Payment Award
Number of Shares Authorized	35,000,000
Number of Shares for Each Full Value Award	2.70
Total Duration of the Stock Incentive Plan	8 years
Award Vesting Period	3 years
Performance Share Units
Share-based Compensation Arrangement by Share-based Payment Award
Award Vesting Period	3 years
Weighted Average Grant Date Fair Value of Shares Granted	$ 44.19	$ 51.37	$ 28.41
Compensation Cost Not yet Recognized	$ 5.9
Period for Recognition of Compensation Cost Not Yet Recognized	1 year 7 months
Shares Outstanding Ending Balance	283,000	331,000
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award
Weighted Average Grant Date Fair Value of Shares Granted	$ 47.76	$ 48.92	$ 28.80
Compensation Cost Not yet Recognized	$ 16.5
Period for Recognition of Compensation Cost Not Yet Recognized	10 months 24 days
Fair Value of Awards Vested During the Period	$ 18.1	$ 13.3	$ 18.3
Shares Outstanding Ending Balance	827,000	871,000
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award
Stock Option Compensation Not yet Recognized	$ 0
Options Granted	0	0	0
Minimum | Performance Share Units
Share-based Compensation Arrangement by Share-based Payment Award
Percentage of Stock-based Awards Possible to be Earned	40.00%
Minimum | Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award
Award Vesting Period	1 year
Minimum | Stock Options
Share-based Compensation Arrangement by Share-based Payment Award
Award Vesting Period	1 year
Maximum | Performance Share Units
Share-based Compensation Arrangement by Share-based Payment Award
Percentage of Stock-based Awards Possible to be Earned	180.00%
Maximum | Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award
Award Vesting Period	3 years
Maximum | Stock Options
Share-based Compensation Arrangement by Share-based Payment Award
Award Vesting Period	3 years

Reinsurance - Premium Income Da

Reinsurance - Premium Income Data (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reinsurance Disclosures [Abstract]
Direct Premium Income									$ 9,171.1	$ 8,677.2	$ 8,385
Reinsurance Assumed									142.6	230	236.3
Reinsurance Ceded									(327.6)	(310.1)	(263.6)
Premium Income	$ 2,263.3	$ 2,251.8	$ 2,221	$ 2,250	$ 2,158.4	$ 2,153.6	$ 2,142.2	$ 2,142.9	8,986.1	8,597.1	8,357.7
Ceded Benefits and Change in Reserves for Future Benefits									$ 667.2	$ 655.4	$ 648.3

Reinsurance - Additional Inform

Reinsurance - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2018
Number of companies that make up majority of reinsurance recoverable	13
AM Best A Rating or Better | Reinsurer Concentration Risk | Reinsurance Recoverable | Top 13 Reinsurers
Percentage of Concentration Risk	92.00%
AM Best, A- Rating | Reinsurer Concentration Risk | Reinsurance Recoverable | Other Reinsurers
Percentage of Concentration Risk	7.00%
AM Best, Below A- or Not Rated | Reinsurer Concentration Risk | Reinsurance Recoverable | Other Reinsurers
Percentage of Concentration Risk	1.00%
Individual Disability | Unum US
Reinsurance Retention Policy, Reinsured Risk, Percentage	30.00%

Premium Income by Major Line of

Premium Income by Major Line of Business within Each Segment (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information
Premium Income	$ 2,263.3	$ 2,251.8	$ 2,221	$ 2,250	$ 2,158.4	$ 2,153.6	$ 2,142.2	$ 2,142.9	$ 8,986.1	$ 8,597.1	$ 8,357.7
Accident, Sickness, and Disability
Segment Reporting Information
Premium Income									6,673.5	6,449.9	6,296.7
Life Insurance
Segment Reporting Information
Premium Income									2,312.6	2,147.2	2,061
Operating Segments
Segment Reporting Information
Premium Income									8,986.1	8,597.1	8,357.7
Operating Segments | Unum US
Segment Reporting Information
Premium Income									5,736.4	5,443.5	5,240.9
Operating Segments | Unum US | Group Long-term Disability
Segment Reporting Information
Premium Income									1,766.2	1,749.6	1,726.6
Operating Segments | Unum US | Group Short-term Disability
Segment Reporting Information
Premium Income									706.3	639.8	626.1
Operating Segments | Unum US | Group Life
Segment Reporting Information
Premium Income									1,583.7	1,467.5	1,410
Operating Segments | Unum US | Accidental Death & Dismemberment
Segment Reporting Information
Premium Income									156.3	147.5	140.3
Operating Segments | Unum US | Individual Disability
Segment Reporting Information
Premium Income									425.4	420.2	480.3
Operating Segments | Unum US | Voluntary Benefits
Segment Reporting Information
Premium Income									895.7	849.4	796.5
Operating Segments | Unum US | Dental and Vision
Segment Reporting Information
Premium Income									202.8	169.5	61.1
Operating Segments | Unum International
Segment Reporting Information
Premium Income									568.8	513	529.3
Operating Segments | Unum International | Group Long-term Disability
Segment Reporting Information
Premium Income									358.9	340.3	355.2
Operating Segments | Unum International | Group Life
Segment Reporting Information
Premium Income									110.8	103.1	105.7
Operating Segments | Unum International | Supplemental
Segment Reporting Information
Premium Income									99.1	69.6	68.4
Operating Segments | Colonial Life
Segment Reporting Information
Premium Income									1,603.8	1,511.4	1,417.1
Operating Segments | Colonial Life | Accident, Sickness, and Disability
Segment Reporting Information
Premium Income									929.3	884.2	830
Operating Segments | Colonial Life | Life Insurance
Segment Reporting Information
Premium Income									328.4	300.4	273.8
Operating Segments | Colonial Life | Cancer and Critical Illness Colonial
Segment Reporting Information
Premium Income									346.1	326.8	313.3
Operating Segments | Closed Block
Segment Reporting Information
Premium Income									1,077.1	1,129.2	1,170.4
Operating Segments | Closed Block | Individual Disability
Segment Reporting Information
Premium Income									420.8	471.8	521.9
Operating Segments | Closed Block | Long-term Care
Segment Reporting Information
Premium Income									648.3	648.7	643.9
Operating Segments | Closed Block | Other Insurance Product Line
Segment Reporting Information
Premium Income									$ 8	$ 8.7	$ 4.6

Selected Operating Statement Da

Selected Operating Statement Data by Segment (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information
Premium Income	$ 2,263.3	$ 2,251.8	$ 2,221	$ 2,250	$ 2,158.4	$ 2,153.6	$ 2,142.2	$ 2,142.9	$ 8,986.1	$ 8,597.1	$ 8,357.7
Net Investment Income	$ 608.6	$ 619.2	$ 623.6	$ 602.3	$ 619.8	$ 609	$ 620.5	$ 602.4	2,453.7	2,451.7	2,459
Other Income									198.2	197.7	205.6
Interest and Debt Expense									167.3	159.9	166
Operating Segments
Segment Reporting Information
Premium Income									8,986.1	8,597.1	8,357.7
Net Investment Income									2,453.7	2,451.7	2,459
Other Income									198.2	197.7	205.6
Adjusted Operating Revenue									11,638	11,246.5	11,022.3
Adjusted Operating Income (Loss)									1,418.1	1,423.3	1,323.5
Interest and Debt Expense									167.3	159.9	166
Depreciation and Amortization									673.8	636.1	600.2
Operating Segments | Unum US
Segment Reporting Information
Premium Income									5,736.4	5,443.5	5,240.9
Net Investment Income									778.7	811.2	828.7
Other Income									118.5	113.2	113.3
Adjusted Operating Revenue									6,633.6	6,367.9	6,182.9
Adjusted Operating Income (Loss)									1,014.6	1,009.5	914.2
Interest and Debt Expense									0	0	0
Depreciation and Amortization									389.6	371.3	353
Operating Segments | Unum International
Segment Reporting Information
Premium Income									568.8	513	529.3
Net Investment Income									117.2	120.2	118.1
Other Income									0.4	0.7	0.2
Adjusted Operating Revenue									686.4	633.9	647.6
Adjusted Operating Income (Loss)									113.9	111.7	128.6
Interest and Debt Expense									0	0	0
Depreciation and Amortization									17.6	17.3	16.4
Operating Segments | Colonial Life
Segment Reporting Information
Premium Income									1,603.8	1,511.4	1,417.1
Net Investment Income									151.2	144.9	141.5
Other Income									1.2	1.1	1.2
Adjusted Operating Revenue									1,756.2	1,657.4	1,559.8
Adjusted Operating Income (Loss)									335.2	325	314.2
Interest and Debt Expense									0	0	0
Depreciation and Amortization									257.3	239.9	222.9
Operating Segments | Closed Block
Segment Reporting Information
Premium Income									1,077.1	1,129.2	1,170.4
Net Investment Income									1,377.1	1,354	1,352.2
Other Income									75.4	79.8	86
Adjusted Operating Revenue									2,529.6	2,563	2,608.6
Adjusted Operating Income (Loss)									125.5	123.9	129.5
Interest and Debt Expense									6.9	6.7	6.9
Depreciation and Amortization									8.3	6.7	6.9
Operating Segments | Corporate and Other Segment
Segment Reporting Information
Premium Income									0	0	0
Net Investment Income									29.5	21.4	18.5
Other Income									2.7	2.9	4.9
Adjusted Operating Revenue									32.2	24.3	23.4
Adjusted Operating Income (Loss)									(171.1)	(146.8)	(163)
Interest and Debt Expense									160.4	153.2	159.1
Depreciation and Amortization									$ 1	$ 0.9	$ 1

Segment Information Deferred Ac

Segment Information Deferred Acquisition Costs by Segment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Movement Analysis of Deferred Policy Acquisition Costs
Deferred Acquisition Costs at Beginning of Year	$ 2,184.6
Deferred Policy Acquisition Costs, Amortization Expense	(565.5)	$ (527.1)	$ (493)
Deferred Acquisition Costs at End of Year	2,309.4	2,184.6
Operating Segments
Movement Analysis of Deferred Policy Acquisition Costs
Deferred Acquisition Costs at Beginning of Year	2,184.6	2,094.2	2,008.5
Deferral of Acquisition Costs	668	628	592.4
Deferred Policy Acquisition Costs, Amortization Expense	(565.5)	(527.1)	(493)
Adjustment Related to Unrealized Investment Gains and Losses	23.5	(12.5)	(9.5)
Deferred Policy Acquisition Costs Foreign Currency Translation Adjustment And Other	(1.2)	2	(4.2)
Deferred Acquisition Costs at End of Year	2,309.4	2,184.6	2,094.2
Operating Segments | Unum US
Movement Analysis of Deferred Policy Acquisition Costs
Deferred Acquisition Costs at Beginning of Year	1,205.4	1,176.5	1,136.4
Deferral of Acquisition Costs	344	325.5	314.1
Deferred Policy Acquisition Costs, Amortization Expense	(315.1)	(293.6)	(275.2)
Adjustment Related to Unrealized Investment Gains and Losses	5.1	(3)	1.2
Deferred Policy Acquisition Costs Foreign Currency Translation Adjustment And Other	0	0	0
Deferred Acquisition Costs at End of Year	1,239.4	1,205.4	1,176.5
Operating Segments | Unum International
Movement Analysis of Deferred Policy Acquisition Costs
Deferred Acquisition Costs at Beginning of Year	21.3	21.4	27.1
Deferral of Acquisition Costs	8.1	7	8.2
Deferred Policy Acquisition Costs, Amortization Expense	(8.2)	(9.1)	(9.7)
Adjustment Related to Unrealized Investment Gains and Losses	0	0	0
Deferred Policy Acquisition Costs Foreign Currency Translation Adjustment And Other	(1.2)	2	(4.2)
Deferred Acquisition Costs at End of Year	20	21.3	21.4
Operating Segments | Colonial Life
Movement Analysis of Deferred Policy Acquisition Costs
Deferred Acquisition Costs at Beginning of Year	957.9	896.3	845
Deferral of Acquisition Costs	315.9	295.5	270.1
Deferred Policy Acquisition Costs, Amortization Expense	(242.2)	(224.4)	(208.1)
Adjustment Related to Unrealized Investment Gains and Losses	18.4	(9.5)	(10.7)
Deferred Policy Acquisition Costs Foreign Currency Translation Adjustment And Other	0	0	0
Deferred Acquisition Costs at End of Year	$ 1,050	$ 957.9	$ 896.3

Assets by Segment (Detail)

Assets by Segment (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information
Total Assets	$ 61,875.6	$ 64,013.1
Operating Segments
Segment Reporting Information
Total Assets	61,875.6	64,013.1
Operating Segments | Unum US
Segment Reporting Information
Total Assets	17,510.9	18,109.1
Operating Segments | Unum International
Segment Reporting Information
Total Assets	3,426.8	3,428.1
Operating Segments | Colonial Life
Segment Reporting Information
Total Assets	4,237.9	4,184.1
Operating Segments | Closed Block
Segment Reporting Information
Total Assets	34,527.6	35,051.2
Operating Segments | Corporate and Other Segment
Segment Reporting Information
Total Assets	$ 2,172.4	$ 3,240.6

Reconciliation of Total Revenue

Reconciliation of Total Revenue and Income Before Income Tax to Operating Revenue and Operating Income (Detail) - USD ($) $ in Millions	3 Months Ended											12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018		Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017		Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting, Revenue Reconciling Item
Total Revenue	$ 2,880.8	$ 2,927.8		$ 2,890.3	$ 2,899.6	$ 2,839.2		$ 2,819.1	$ 2,822	$ 2,806.5		$ 11,598.5	$ 11,286.8	$ 11,046.5
Net Realized Investment Gain (Loss)	(41.4)	6.7		(2.6)	(2.2)	11.4		9.8	8.1	11		(39.5)	40.3	24.2
Income Before Income Tax	309.7	(377.8)	[1]	354.8	341.1	345.3	[2]	366.8	361.6	330.3	[3]	627.8	1,404	1,347.7
Net Realized Investment Gain (Loss)	$ (41.4)	$ 6.7		$ (2.6)	$ (2.2)	$ 11.4		$ 9.8	$ 8.1	$ 11		(39.5)	40.3	24.2
Unclaimed Death Benefit Reserve Increase Before Taxes													(39)
Operating Segments
Segment Reporting, Revenue Reconciling Item
Adjusted Operating Revenue												11,638	11,246.5	11,022.3
Total Revenue												11,598.5	11,286.8	11,046.5
Net Realized Investment Gain (Loss)												(39.5)	40.3	24.2
Income Before Income Tax												627.8	1,404	1,347.7
Net Realized Investment Gain (Loss)												(39.5)	40.3	24.2
Loss from Guaranty Fund Assessment												0	(20.6)	0
Unclaimed Death Benefit Reserve Increase Before Taxes												0	(39)	0
Reserve Increase for Long-term Care, Before Tax												(750.8)	0	0
Adjusted Operating Income												$ 1,418.1	$ 1,423.3	$ 1,323.5
[1]	Third quarter of 2018 reserve increase of $750.8 million before tax and $593.1 million after tax related to long-term care.
[2]	Fourth quarter of 2017 reserve increase of $39.0 million before tax and $25.4 million after tax related to unclaimed death benefits.
[3]	First quarter of 2017 loss from a guaranty fund assessment related to an unaffiliated insurer that was declared insolvent of $20.6 million before tax and $13.4 million after tax.

Segment Information Segments -

Segment Information Segments - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)IntegerRate	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)Rate
Segment Reporting [Abstract]
Number of Operating Segments | Integer	3
Supplementary Insurance Information, by Segment
Percentage Ownership of Acquired Business | Rate			100.00%
Name of Acquired Businesses			H&J Capital, L.L.C., parent of Starmount Life Insurance Company and AlwaysCare Benefits (Starmount)
Assets of Acquiree at Acquisition Date			$ 93.1
Total Cash Purchase Price to Acquire Business			140.3
Liabilities of Acquiree at Acquisition Date			55.7
Business Combination, Contingent Consideration, Liability, Noncurrent			10
Goodwill	$ 350.3	$ 338.6
Payable due 18 Months After Acquisition
Supplementary Insurance Information, by Segment
Business Combination, Contingent Consideration, Liability, Noncurrent			5
Payable due 24 Months After Acquisition
Supplementary Insurance Information, by Segment
Business Combination, Contingent Consideration, Liability, Noncurrent			5
Unum US and Colonial
Supplementary Insurance Information, by Segment
Goodwill			$ 111.2
Unum US
Supplementary Insurance Information, by Segment
Percent of Goodwill Allocated to a Business Segment | Rate			75.00%
Goodwill	280	271.1
Unum International
Supplementary Insurance Information, by Segment
Goodwill	42.6	39.8
Colonial Life
Supplementary Insurance Information, by Segment
Percent of Goodwill Allocated to a Business Segment | Rate			25.00%
Goodwill	$ 27.7	27.7
Jaimini Health, Inc.
Supplementary Insurance Information, by Segment
Percentage Ownership of Acquired Business | Rate	100.00%
Name of Acquired Businesses	Jaimini Health, Inc. (Jaimini Health)
Unum Poland
Supplementary Insurance Information, by Segment
Percentage Ownership of Acquired Business | Rate	100.00%
Name of Acquired Businesses	Unum Poland
Leavelogic Inc.
Supplementary Insurance Information, by Segment
Percentage Ownership of Acquired Business | Rate	100.00%
Name of Acquired Businesses	Leavelogic, Inc (Leavelogic)
Series of Individually Immaterial Business Acquisitions
Supplementary Insurance Information, by Segment
Business Acquisition, Revenue Reported by Acquired Entity for Last Annual Period		$ 61
Assets of Acquiree at Acquisition Date	$ 344
Total Cash Purchase Price to Acquire Business	151
Liabilities of Acquiree at Acquisition Date	206
Goodwill	$ 13

Commitments and Contingent Li_2

Commitments and Contingent Liabilities - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Future Minimum Lease Payments Due	$ 157.7
Future Minimum Lease Payments Due Within Twelve Months	30.4
Future Minimum Lease Payments Due Within Two Years	26.3
Future Minimum Lease Payments Due Within Three Years	22.2
Future Minimum Lease Payments Due Within Four Years	18.2
Future Minimum Lease Payments Due Within Five Years	12.3
Future Minimum Lease Payments Due Thereafter	48.3
Rental Expense	64.3	$ 54.2	$ 51.4
Total Unfunded Commitments	$ 515.6

Statutory Financial Informati_3

Statutory Financial Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Traditional U.S. Life Insurance Subsidiaries
Statutory Accounting Practices
Statutory Net Income (Loss)	$ 953	$ 807.4	$ 855.1
Statutory Combined Net Gain (Loss) from Operations	959.8	812.4	884.6
Statutory Combined Capital and Surplus	3,572.7	3,448.3
Captive Reinsurers
Statutory Accounting Practices
Statutory Net Income (Loss)	(109.6)	(137.1)	48.4
Statutory Combined Net Gain (Loss) from Operations	(110.9)	(143.1)	$ 50.6
Statutory Combined Capital and Surplus	$ 1,766.2	$ 1,606.9

Statutory Financial Informati_4

Statutory Financial Information - Additional Details (Detail) £ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2017GBP (£)	Dec. 31, 2016USD ($)	Dec. 31, 2018GBP (£)	Dec. 31, 2017GBP (£)
Fairwind Insurance Company
Statutory Accounting Practices
Statutory Accounting Practices, Permitted Practice, Amount	$ 137	$ 142
Unum Limited
Statutory Accounting Practices
Statutory Net Income | £			£ 78.7
Statutory Combined Capital and Surplus | £						£ 672.3
Statutory Accounting Practices, Statutory Amount Available for Dividend Payments | £					£ 140
Traditional U.S. Life Insurance Subsidiaries
Statutory Accounting Practices
Statutory Net Income	953	807.4		$ 855.1
Statutory Combined Capital and Surplus	3,572.7	3,448.3
Statutory Accounting Practices, Statutory Amount Available for Dividend Payments	994.9
Cash and Securities Segregated under Federal and Other Regulations	$ 155.7	$ 155.7

Schedule of Unaudited Quarterly

Schedule of Unaudited Quarterly Results (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended											12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018		Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017		Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Selected Quarterly Financial Information [Abstract]
Premium Income	$ 2,263.3	$ 2,251.8		$ 2,221	$ 2,250	$ 2,158.4		$ 2,153.6	$ 2,142.2	$ 2,142.9		$ 8,986.1	$ 8,597.1	$ 8,357.7
Net Investment Income	608.6	619.2		623.6	602.3	619.8		609	620.5	602.4		2,453.7	2,451.7	2,459
Net Realized Investment Gain (Loss)	(41.4)	6.7		(2.6)	(2.2)	11.4		9.8	8.1	11		(39.5)	40.3	24.2
Total Revenue	2,880.8	2,927.8		2,890.3	2,899.6	2,839.2		2,819.1	2,822	2,806.5		11,598.5	11,286.8	11,046.5
Income (Loss) Before Income Tax	309.7	(377.8)	[1]	354.8	341.1	345.3	[2]	366.8	361.6	330.3	[3]	627.8	1,404	1,347.7
Net Income (Loss)	$ 249.1	$ (284.7)	[1]	$ 285.5	$ 273.5	$ 266.9	[2],[4]	$ 252.3	$ 245.1	$ 229.9	[3]	$ 523.4	$ 994.2	$ 931.4
Basic Earnings Per Share	$ 1.15	$ (1.30)	[1]	$ 1.29	$ 1.23	$ 1.19	[2],[4]	$ 1.12	$ 1.08	$ 1	[3]	$ 2.38	$ 4.39	$ 3.96
Diluted Earnings Per Share	$ 1.15	$ (1.30)	[1]	$ 1.29	$ 1.23	$ 1.19	[2],[4]	$ 1.12	$ 1.07	$ 1	[3]	$ 2.38	$ 4.37	$ 3.95
[1]	Third quarter of 2018 reserve increase of $750.8 million before tax and $593.1 million after tax related to long-term care.
[2]	Fourth quarter of 2017 reserve increase of $39.0 million before tax and $25.4 million after tax related to unclaimed death benefits.
[3]	First quarter of 2017 loss from a guaranty fund assessment related to an unaffiliated insurer that was declared insolvent of $20.6 million before tax and $13.4 million after tax.
[4]	Fourth quarter of 2017 net tax benefit of $31.5 million related to the TCJA.

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, 2018USD ($)
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost of Investments	$ 47,914.2	[1]
Amount Shown on the Balance Sheet	50,707.6
U.S. Government and Agencies
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost of Investments	1,702.1	[1]
Fair Value of Investments	1,814.4
Amount Shown on the Balance Sheet	1,814.4
State and Municipal Securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost of Investments	2,121.5	[1]
Fair Value of Investments	2,424.2
Amount Shown on the Balance Sheet	2,424.2
Foreign Governments
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost of Investments	825.8	[1]
Fair Value of Investments	983.7
Amount Shown on the Balance Sheet	983.7
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	6,626.2	[1]
Fair Value of Investments	7,412.8
Amount Shown on the Balance Sheet	7,412.8
Mortgage/Asset-backed Securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost of Investments	1,523.8	[1]
Fair Value of Investments	1,582.7
Amount Shown on the Balance Sheet	1,582.7
All Other Corporate Bonds
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost of Investments	27,436.8	[1]
Fair Value of Investments	28,754
Amount Shown on the Balance Sheet	28,754
Redeemable Preferred Stock
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost of Investments	39	[1]
Fair Value of Investments	39.9
Amount Shown on the Balance Sheet	39.9
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	40,275.2	[1]
Fair Value of Investments	43,011.7
Amount Shown on the Balance Sheet	43,011.7
Mortgages
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost of Investments	2,295	[1]
Amount Shown on the Balance Sheet	2,295
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	3,729.9	[1]
Amount Shown on the Balance Sheet	3,729.9
Derivatives
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost of Investments	0	[1]
Amount Shown on the Balance Sheet	30.9	[2]
Equity Securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost of Investments	32.6	[1]
Amount Shown on the Balance Sheet	29.2
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	613.4	[1]
Amount Shown on the Balance Sheet	642.8	[3]
Short-term Investments
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost of Investments	968.1	[1]
Amount Shown on the Balance Sheet	$ 968.1
[1]	The amortized cost for fixed maturity securities and mortgage loans represents original cost reduced by repayments, write-downs from other-than-temporary declines in fair value, amortization of premiums, and/or accretion of discounts.
[2]	Derivatives are carried at fair value.
[3]	The difference between amortized cost and carrying value primarily results from changes in the partnership owner's equity since acquisition.

Parent Company Balance Sheet (D

Parent Company Balance Sheet (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Assets
Other Long-term Investments	$ 702.9	$ 646.8
Short-term Investments	968.1	1,155.1
Deferred Income Tax	109.9
Other Assets	789	628.7
Total Assets	61,875.6	64,013.1
Liabilities
Short-term Debt	0	199.9
Long-term Debt	2,971.3	2,738.4
Other Liabilities	1,634.7	1,726.9
Total Liabilities	53,253.8	54,438.2
Stockholders' Equity
Common Stock	30.5	30.5
Additional Paid-in Capital	2,321.7	2,303.3
Accumulated Other Comprehensive Income (Loss)	(814.2)	127.5
Retained Earnings	9,863.1	9,542.2
Treasury Stock	(2,779.3)	(2,428.6)
Total Stockholders' Equity	8,621.8	9,574.9	$ 8,968
Total Liabilities and Stockholders' Equity	61,875.6	64,013.1
Parent Company
Assets
Fixed Maturity Securities - at fair value (amortized cost: $139.0; $153.9)	135.9	154.1
Other Long-term Investments	38.8	16.8
Short-term Investments	285.2	477.8
Investments in Subsidiaries	11,383.6	12,157.1
Deferred Income Tax	116.7	121.5
Other Assets	446.9	455.4
Total Assets	12,407.1	13,382.7
Liabilities
Short-term Debt	0	199.9
Long-term Debt	2,831.3	2,538.4
Pension and Postretirement Benefits	594.2	683.3
Other Liabilities	359.8	386.2
Total Liabilities	3,785.3	3,807.8
Stockholders' Equity
Common Stock	30.5	30.5
Additional Paid-in Capital	2,321.7	2,303.3
Accumulated Other Comprehensive Income (Loss)	(814.2)	127.5
Retained Earnings	9,863.1	9,542.2
Treasury Stock	(2,779.3)	(2,428.6)
Total Stockholders' Equity	8,621.8	9,574.9
Total Liabilities and Stockholders' Equity	$ 12,407.1	$ 13,382.7

Parent Company Balance Sheet (P

Parent Company Balance Sheet (Parenthetical) (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Condensed Balance Sheet Statements, Captions
Amortized Cost of Fixed Maturity Securities	$ 40,275.2	$ 39,780.5
Parent Company
Condensed Balance Sheet Statements, Captions
Amortized Cost of Fixed Maturity Securities	$ 139	$ 153.9

Parent Company Statement of Inc

Parent Company Statement of Income (Detail) - USD ($) $ in Millions	3 Months Ended											12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018		Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017		Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Condensed Income Statements, Captions
Other Income												$ 198.2	$ 197.7	$ 205.6
Total Revenue	$ 2,880.8	$ 2,927.8		$ 2,890.3	$ 2,899.6	$ 2,839.2		$ 2,819.1	$ 2,822	$ 2,806.5		11,598.5	11,286.8	11,046.5
Income Before Income Tax	309.7	(377.8)	[1]	354.8	341.1	345.3	[2]	366.8	361.6	330.3	[3]	627.8	1,404	1,347.7
Income Tax Expense (Benefit)												104.4	409.8	416.3
Net Income	$ 249.1	$ (284.7)	[1]	$ 285.5	$ 273.5	$ 266.9	[2],[4]	$ 252.3	$ 245.1	$ 229.9	[3]	523.4	994.2	931.4
Other Comprehensive Income (Loss), Net of Tax												(924.2)	178.5	(67.1)
Comprehensive Income (Loss)												(400.8)	1,172.7	864.3
Parent Company
Condensed Income Statements, Captions
Cash Dividends from Subsidiaries												1,135.4	830.2	676.5
Other Income												66.6	66.6	58.4
Total Revenue												1,202	896.8	734.9
Interest and Debt Expense												161.4	154.2	160.1
Other Expenses												53.4	37.1	32.3
Total Expenses												214.8	191.3	192.4
Income Before Income Tax												987.2	705.5	542.5
Income Tax Expense (Benefit)												(1.7)	115.3	(20.2)
Income of Parent Company												988.9	590.2	562.7
Equity in Undistributed Earnings (Loss) of Subsidiaries												(465.5)	404	368.7
Net Income												523.4	994.2	931.4
Other Comprehensive Income (Loss), Net of Tax												(924.2)	178.5	(67.1)
Comprehensive Income (Loss)												$ (400.8)	$ 1,172.7	$ 864.3
[1]	Third quarter of 2018 reserve increase of $750.8 million before tax and $593.1 million after tax related to long-term care.
[2]	Fourth quarter of 2017 reserve increase of $39.0 million before tax and $25.4 million after tax related to unclaimed death benefits.
[3]	First quarter of 2017 loss from a guaranty fund assessment related to an unaffiliated insurer that was declared insolvent of $20.6 million before tax and $13.4 million after tax.
[4]	Fourth quarter of 2017 net tax benefit of $31.5 million related to the TCJA.

Parent Company Cash Flow Statem

Parent Company Cash Flow Statement (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Condensed Cash Flow Statements, Captions
Cash Provided by Operating Activities	$ 1,536.5	$ 1,164.1	$ 1,121.6
Cash Flows from Investing Activities
Proceeds from Sales of Fixed Maturity Securities	642.5	436.3	911.5
Proceeds from Maturities of Fixed Maturity Securities	2,815.4	2,560.8	2,197.8
Proceeds from Sales and Maturities of Other Investments	454	257.9	331.3
Purchase of Fixed Maturity Securities	(3,861.7)	(2,808.5)	(3,362.8)
Purchase of Other Investments	(623.2)	(474.3)	(576)
Net Sales (Purchases) of Short-term Investments	200.5	(356.4)	6.3
Net Purchases of Property and Equipment	(144.1)	(105.3)	(85)
Acquisition of Business			(140.3)
Net Cash Used by Investing Activities	(930.1)	(499.3)	(715.5)
Cash Flows from Financing Activities
Short-term Debt Repayment	(200)	0	0
Issuance of Long-term Debt	290.7	0	609.1
Long-term Debt Repayment	(60)	(63.5)	(414)
Issuance of Common Stock	4.6	10.8	8.5
Repurchase of Common Stock	(356.2)	(401.8)	(405.2)
Dividends Paid to Stockholders	(215.6)	(196)	(182.6)
Other, Net	(53.3)	(37.3)	(34.4)
Net Cash Used by Financing Activities	(589.8)	(687.8)	(418.6)
Net Decrease in Cash and Bank Deposits	16.6	(23)	(12.5)
Parent Company
Condensed Cash Flow Statements, Captions
Cash Provided by Operating Activities	1,052.1	740.6	685.4
Cash Flows from Investing Activities
Proceeds from Sales of Fixed Maturity Securities	0	0	2.6
Proceeds from Maturities of Fixed Maturity Securities	52.5	194.3	111.2
Proceeds from Sales and Maturities of Other Investments	0	35.2	0.4
Purchase of Fixed Maturity Securities	(47.9)	(121.2)	(56.5)
Purchase of Other Investments	(22.3)	0	(23.3)
Net Sales (Purchases) of Short-term Investments	192.6	(99.9)	(89.8)
Cash Distributions to Subsidiaries	(530.8)	(79.5)	(143.6)
Net Purchases of Property and Equipment	(73.2)	(83.3)	(55.5)
Acquisition of Business	(146.1)	0	(140.3)
Other, Net	0	0	0.2
Net Cash Used by Investing Activities	(575.2)	(154.4)	(394.6)
Cash Flows from Financing Activities
Short-term Debt Repayment	(200)	0	0
Issuance of Long-term Debt	290.7	0	609.1
Long-term Debt Repayment	0	0	(350)
Issuance of Common Stock	4.6	10.8	8.5
Repurchase of Common Stock	(356.2)	(401.8)	(405.2)
Dividends Paid to Stockholders	(215.6)	(196)	(182.6)
Other, Net	(9.3)	0.2	(1)
Net Cash Used by Financing Activities	(485.8)	(586.8)	(321.2)
Net Decrease in Cash and Bank Deposits	$ (8.9)	$ (0.6)	$ (30.4)

Parent Company Debt Schedule (D

Parent Company Debt Schedule (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument
Long-term Debt, Excluding Current Maturities	$ 2,971.3			$ 2,738.4
Debt Instrument, Unamortized Premium (Discount), Net	9.6			9.7
Debt Issuance Costs, Noncurrent, Net	(30.8)			(24.4)
Current Maturities of Long-term Debt	0			199.9
Debt Issuance Costs, Current, Net	0			(0.1)
Fair Value Hedge Adjustment, LT Debt
Debt Instrument
Long-term Debt, Excluding Current Maturities	(5.1)			(4.5)
Parent Company
Debt Instrument
Long-term Debt, Excluding Current Maturities	2,831.3			2,538.4
Debt Instrument, Unamortized Premium (Discount), Net	9.6			9.7
Debt Issuance Costs, Noncurrent, Net	(30.8)			(24.4)
Current Maturities of Long-term Debt	0			199.9
Debt Issuance Costs, Current, Net	0			(0.1)
Debt, Long-term and Short-term, Combined Amount	2,831.3			2,738.3
Parent Company | Fair Value Hedge Adjustment, LT Debt
Debt Instrument
Long-term Debt, Excluding Current Maturities	$ (5.1)			(4.5)
Notes Issued in 1998 with 2028 Maturity Date | Senior Notes
Debt Instrument
Year of Maturity	Dec. 31, 2028
Long-term Debt, Excluding Current Maturities	$ 365.8			365.8
Notes Issued in 1998 with 2028 Maturity Date | Parent Company | Senior Notes
Debt Instrument
Year of Maturity	Dec. 31, 2028
Long-term Debt, Excluding Current Maturities	$ 365.8			365.8
Notes Issued in 1998 with 2028 Maturity Date | Minimum | Senior Notes
Debt Instrument
Stated Interest Rate of Debt			6.75%
Notes Issued in 1998 with 2028 Maturity Date | Minimum | Parent Company | Senior Notes
Debt Instrument
Stated Interest Rate of Debt			6.75%
Notes Issued in 1998 with 2028 Maturity Date | Maximum | Senior Notes
Debt Instrument
Stated Interest Rate of Debt			7.25%
Notes Issued in 1998 with 2028 Maturity Date | Maximum | Parent Company | Senior Notes
Debt Instrument
Stated Interest Rate of Debt			7.25%
Notes Issued in 2002 | Senior Notes
Debt Instrument
Stated Interest Rate of Debt			7.375%
Year of Maturity	Dec. 31, 2032
Long-term Debt, Excluding Current Maturities	$ 39.5			39.5
Notes Issued in 2002 | Parent Company | Senior Notes
Debt Instrument
Stated Interest Rate of Debt			7.375%
Year of Maturity	Dec. 31, 2032
Long-term Debt, Excluding Current Maturities	$ 39.5			39.5
Notes Issued in 2010 | Senior Notes
Debt Instrument
Stated Interest Rate of Debt			5.625%
Year of Maturity	Dec. 31, 2020
Long-term Debt, Excluding Current Maturities	$ 400			400
Notes Issued in 2010 | Parent Company | Senior Notes
Debt Instrument
Stated Interest Rate of Debt			5.625%
Year of Maturity	Dec. 31, 2020
Long-term Debt, Excluding Current Maturities	$ 400			400
Notes Issued in 2012 and 2016 | Parent Company | Senior Notes
Debt Instrument
Stated Interest Rate of Debt			5.75%
Year of Maturity	Dec. 31, 2042
Long-term Debt, Excluding Current Maturities	$ 500			500
Notes Issued in 2014 | Senior Notes
Debt Instrument
Stated Interest Rate of Debt			4.00%
Year of Maturity	Dec. 31, 2024
Long-term Debt, Excluding Current Maturities	$ 350			350
Notes Issued in 2014 | Parent Company | Senior Notes
Debt Instrument
Stated Interest Rate of Debt			4.00%
Year of Maturity	Dec. 31, 2024
Long-term Debt, Excluding Current Maturities	$ 350			350
Notes Issued in 2015 | Senior Notes
Debt Instrument
Stated Interest Rate of Debt			3.875%
Year of Maturity	Dec. 31, 2025
Long-term Debt, Excluding Current Maturities	$ 275			275
Notes Issued in 2015 | Parent Company | Senior Notes
Debt Instrument
Stated Interest Rate of Debt			3.875%
Year of Maturity	Dec. 31, 2025
Long-term Debt, Excluding Current Maturities	$ 275			275
Notes Issued in 2016 | Senior Notes
Debt Instrument
Stated Interest Rate of Debt			3.00%
Year of Maturity	May 15, 2021
Long-term Debt, Excluding Current Maturities	$ 350			350
Notes Issued in 2016 | Parent Company | Senior Notes
Debt Instrument
Stated Interest Rate of Debt			3.00%
Year of Maturity	Dec. 31, 2021
Long-term Debt, Excluding Current Maturities	$ 350			350
Notes Issued 1990 to 1996 | Medium-term Notes
Debt Instrument
Debt Instrument, Maturity Date Range, Start	Dec. 31, 2023
Debt Instrument, Maturity Date Range, End	Dec. 31, 2028
Long-term Debt, Excluding Current Maturities	$ 50.8			50.8
Notes Issued 1990 to 1996 | Parent Company | Medium-term Notes
Debt Instrument
Debt Instrument, Maturity Date Range, Start	Dec. 31, 2023
Debt Instrument, Maturity Date Range, End	Dec. 31, 2028
Long-term Debt, Excluding Current Maturities	$ 50.8			50.8
Notes Issued 1990 to 1996 | Minimum | Medium-term Notes
Debt Instrument
Stated Interest Rate of Debt			7.00%
Notes Issued 1990 to 1996 | Minimum | Parent Company | Medium-term Notes
Debt Instrument
Stated Interest Rate of Debt			7.00%
Notes Issued 1990 to 1996 | Maximum | Medium-term Notes
Debt Instrument
Stated Interest Rate of Debt			7.19%
Notes Issued 1990 to 1996 | Maximum | Parent Company | Medium-term Notes
Debt Instrument
Stated Interest Rate of Debt			7.19%
Notes Issued in 1998 with 2038 Maturity Date | Junior Subordinated Debt
Debt Instrument
Stated Interest Rate of Debt		7.405%	7.405%
Year of Maturity	Dec. 31, 2038
Long-term Debt, Excluding Current Maturities	$ 226.5			226.5
Notes Issued in 1998 with 2038 Maturity Date | Parent Company | Junior Subordinated Debt
Debt Instrument
Stated Interest Rate of Debt		7.405%	7.405%
Year of Maturity	Dec. 31, 2038
Long-term Debt, Excluding Current Maturities	$ 226.5			226.5
Notes Issued in 2018 with a 2058 Maturity Date | Junior Subordinated Debt
Debt Instrument
Stated Interest Rate of Debt			6.25%
Year of Maturity	Dec. 31, 2058
Long-term Debt, Excluding Current Maturities	$ 300			0
Notes Issued in 2018 with a 2058 Maturity Date | Parent Company | Junior Subordinated Debt
Debt Instrument
Stated Interest Rate of Debt			6.25%
Year of Maturity	Dec. 31, 2058
Long-term Debt, Excluding Current Maturities	$ 300			0
Notes Issued in 1998 with 2018 Maturity Date | Parent Company
Debt Instrument
Stated Interest Rate of Debt			7.00%
Current Maturities of Long-term Debt	$ 200
Notes Issued in 1998 with 2018 Maturity Date | Senior Notes
Debt Instrument
Stated Interest Rate of Debt			7.00%
Year of Maturity	Dec. 31, 2018
Current Maturities of Long-term Debt	$ 0			200
Notes Issued in 1998 with 2018 Maturity Date | Senior Notes | Parent Company
Debt Instrument
Stated Interest Rate of Debt			7.00%
Year of Maturity	Jul. 15, 2018
Current Maturities of Long-term Debt	$ 0			$ 200

Parent Company Notes - Addition

Parent Company Notes - Additional Details (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 1998	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2015
Repayments of Principal in 2020					$ 400
Repayments of Principal in 2021					350
Repayments of Principal in 2023					2
Repayments of Principal Thereafter					2,245.6
Current Maturities of Long-term Debt		$ 199.9			0
Long-term Debt, Excluding Current Maturities		2,738.4			2,971.3
Notional Amount of Derivatives		904.5	$ 1,052		799.2			$ 1,470.3
Interest Paid, Including Capitalized Interest, Operating and Investing Activities	$ 167.3	154.4	153.6
Line of Credit Facility, Maximum Borrowing Capacity					400
Line Of Credit Facility Maximum Borrowing Capacity If Requested					600
Letters of Credit Outstanding		2.1			2.1
Amount Outstanding on Line of Credit		0			0
Parent Company
Repayments of Principal in 2020					400
Repayments of Principal in 2021					350
Repayments of Principal in 2023					2
Repayments of Principal Thereafter					2,105.6
Current Maturities of Long-term Debt		199.9			0
Proceeds from Issuance of Debt			600
Long-term Debt, Excluding Current Maturities		2,538.4			2,831.3
Interest Paid, Including Capitalized Interest, Operating and Investing Activities	161.4	148.7	$ 147.8
Line of Credit Facility, Maximum Borrowing Capacity					400
Line Of Credit Facility Maximum Borrowing Capacity If Requested					600
Letters of Credit Outstanding		2.1			2.1
Amount Outstanding on Line of Credit		0			0
Notes Payable Due 2021 | Parent Company
Stated Interest Rate of Debt			3.00%
Proceeds from Issuance of Debt			$ 350
Notes Issued in 2018 with a 2058 Maturity Date | Junior Subordinated Debt
Stated Interest Rate of Debt							6.25%
Proceeds from Issuance of Debt	300
Long-term Debt, Excluding Current Maturities		0			300
Notes Issued in 2018 with a 2058 Maturity Date | Junior Subordinated Debt | Parent Company
Stated Interest Rate of Debt							6.25%
Proceeds from Issuance of Debt	$ 300
Long-term Debt, Excluding Current Maturities		0			300
Notes Issued in 1998 with 2018 Maturity Date | Parent Company
Current Maturities of Long-term Debt					200
Stated Interest Rate of Debt							7.00%
Notes Issued in 2009 | Parent Company
Current Maturities of Long-term Debt			$ 350
Stated Interest Rate of Debt			7.125%
Notes Issued in 1998 with 2038 Maturity Date | Junior Subordinated Debt
Stated Interest Rate of Debt						7.405%	7.405%
Long-term Debt, Excluding Current Maturities		226.5			226.5
Proceeds from Issuance of Senior Long-term Debt				$ 300
Liquidation value per capital security	$ 1,000
Notes Issued in 1998 with 2038 Maturity Date | Junior Subordinated Debt | Parent Company
Stated Interest Rate of Debt						7.405%	7.405%
Long-term Debt, Excluding Current Maturities		226.5			226.5
Proceeds from Issuance of Senior Long-term Debt				$ 300
Liquidation value per capital security	$ 1,000
Notes Payable due 2042 | Parent Company
Stated Interest Rate of Debt			5.75%
Proceeds from Issuance of Debt			$ 250
Notes Issued in 2012 | Parent Company
Stated Interest Rate of Debt			5.75%
Long-term Debt, Excluding Current Maturities			$ 250
Receive Fixed/Pay Variable | Interest Rate Swaps
Notional Amount of Derivatives		250			250
Receive Fixed/Pay Variable | Interest Rate Swaps | Parent Company
Notional Amount of Derivatives		$ 250			$ 250

Schedule III Supplementary In_2

Schedule III Supplementary Insurance Information (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Supplementary Insurance Information, by Segment
Deferred Acquisition Costs		$ 2,309.4	$ 2,184.6
Reserves for Future Policy Contract Benefits		44,841.9	45,601.6
Unearned Premiums		363.3	373.1
Policy and Contract Benefits		1,695.7	1,605.2
Premium Income		8,986.1	8,597.1	$ 8,357.7
Net Investment Income	[1]	2,453.7	2,451.7	2,459
Benefits and Change in Reserves for Future Benefits	[2]	8,020.4	7,055.7	6,941.8
Amortization of Deferred Acquisition Costs		565.5	527.1	493
All Other Expenses	[3]	2,384.8	2,300	2,264
Unum US
Supplementary Insurance Information, by Segment
Deferred Acquisition Costs		1,239.4	1,205.4
Reserves for Future Policy Contract Benefits		10,840.9	11,382.1
Unearned Premiums		47.2	49
Policy and Contract Benefits		1,091.5	1,059.8
Premium Income		5,736.4	5,443.5	5,240.9
Net Investment Income	[1]	778.7	811.2	828.7
Benefits and Change in Reserves for Future Benefits	[2]	3,856.5	3,693.4	3,624.3
Amortization of Deferred Acquisition Costs		315.1	293.6	275.2
All Other Expenses	[3]	1,447.4	1,398	1,369.2
Premiums Written	[4]	3,873	3,701.3	3,564.4
Unum International
Supplementary Insurance Information, by Segment
Deferred Acquisition Costs		20	21.3
Reserves for Future Policy Contract Benefits		2,340.5	2,361.6
Unearned Premiums		123.3	125.7
Policy and Contract Benefits		115.6	108.5
Premium Income		568.8	513	529.3
Net Investment Income	[1]	117.2	120.2	118.1
Benefits and Change in Reserves for Future Benefits	[2]	419.8	381.9	367.4
Amortization of Deferred Acquisition Costs		8.2	9.1	9.7
All Other Expenses	[3]	144.5	131.2	141.9
Premiums Written	[4]	455.5	404.2	435.4
Colonial Life
Supplementary Insurance Information, by Segment
Deferred Acquisition Costs		1,050	957.9
Reserves for Future Policy Contract Benefits		2,330.2	2,224.2
Unearned Premiums		36.3	34.7
Policy and Contract Benefits		206.2	212.1
Premium Income		1,603.8	1,511.4	1,417.1
Net Investment Income	[1]	151.2	144.9	141.5
Benefits and Change in Reserves for Future Benefits	[2]	824.9	788.6	726.4
Amortization of Deferred Acquisition Costs		242.2	224.4	208.1
All Other Expenses	[3]	353.9	331.8	311.1
Premiums Written	[4]	1,277.3	1,210.6	1,145
Closed Block
Supplementary Insurance Information, by Segment
Deferred Acquisition Costs		0	0
Reserves for Future Policy Contract Benefits		29,330.3	29,633.7
Unearned Premiums		156.5	163.7
Policy and Contract Benefits		282.4	224.8
Premium Income		1,077.1	1,129.2	1,170.4
Net Investment Income	[1]	1,377.1	1,354	1,352.2
Benefits and Change in Reserves for Future Benefits	[2]	2,919.2	2,191.8	2,223.7
Amortization of Deferred Acquisition Costs		0	0	0
All Other Expenses	[3]	235.7	247.3	255.4
Premiums Written	[4]	1,065.7	1,109.8	1,161.8
Corporate and Other Segment
Supplementary Insurance Information, by Segment
Premium Income		0	0	0
Net Investment Income	[1]	29.5	21.4	18.5
Benefits and Change in Reserves for Future Benefits	[2]	0	0	0
Amortization of Deferred Acquisition Costs		0	0	0
All Other Expenses	[3]	203.3	191.7	186.4
Premiums Written	[4]	$ 0	$ 0	$ 0
[1]	Net investment income is allocated based upon segmentation. Each segment has its own specifically identified assets and receives the investment income generated by those assets.
[2]	Included in 2018 is a reserve charge of $750.8 million in the Closed Block segment related to our long-term care business. Included in 2017 are unclaimed death benefits reserve increases of $26.6 million in Unum US and $12.4 million in Colonial Life.
[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. Included in 2017 is a loss contingency accrual for a guaranty fund assessment of $20.6 million in Corporate.
[4]	Excludes life insurance.

Schedule IV Reinsurance (Detail

Schedule IV Reinsurance (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reinsurance Premiums for Insurance Companies, by Product Segment
Direct Premiums, Life Insurance in Force	$ 937,300.8				$ 887,857.2				$ 937,300.8	$ 887,857.2	$ 854,783.9
Ceded Premiums, Life Insurance in Force	40,902.8				36,545				40,902.8	36,545	31,882.5
Assumed Premiums, Life Insurance in Force	1,089.3				1,045.8				1,089.3	1,045.8	1,004.7
Premiums, Net, Life Insurance in Force	$ 897,487.3				$ 852,358				$ 897,487.3	$ 852,358	$ 823,906.1
Life Insurance in Force Premiums, Percentage Assumed to Net	0.10%				0.10%				0.10%	0.10%	0.10%
Gross Amount									$ 9,171.1	$ 8,677.2	$ 8,385
Reinsurance Ceded									327.6	310.1	263.6
Assumed Premiums Earned									142.6	230	236.3
Net Amount	$ 2,263.3	$ 2,251.8	$ 2,221	$ 2,250	$ 2,158.4	$ 2,153.6	$ 2,142.2	$ 2,142.9	$ 8,986.1	$ 8,597.1	$ 8,357.7
Percentage of Amount Assumed to Net									1.60%	2.70%	2.80%
Life Insurance
Reinsurance Premiums for Insurance Companies, by Product Segment
Gross Amount									$ 2,442.1	$ 2,272.7	$ 2,202.6
Reinsurance Ceded									138.2	135.7	151.3
Assumed Premiums Earned									8.7	10.2	9.7
Net Amount									$ 2,312.6	$ 2,147.2	$ 2,061
Percentage of Amount Assumed to Net									0.40%	0.50%	0.50%
Accident, Health, and Other Insurance
Reinsurance Premiums for Insurance Companies, by Product Segment
Gross Amount									$ 6,729	$ 6,404.5	$ 6,182.4
Reinsurance Ceded									189.4	174.4	112.3
Assumed Premiums Earned									133.9	219.8	226.6
Net Amount									$ 6,673.5	$ 6,449.9	$ 6,296.7
Percentage of Amount Assumed to Net									2.00%	3.40%	3.60%

Schedule V Valuation and Qual_2

Schedule V Valuation and Qualifying Accounts (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Real Estate reserve (deducted from other long-term investments)
Valuation and Qualifying Accounts Disclosure
Balance at Beginning of Year		$ 4.2	$ 4.2	$ 1.2
Additions Charged to Costs and Expenses		0.6	0	3
Additions Charged to Other Accounts	[1]	0	0	0
Deductions	[2]	3.3	0	0
Balance at End of Year		1.5	4.2	4.2
Allowance for doubtful accounts (deducted from accounts and premiums receivable)
Valuation and Qualifying Accounts Disclosure
Balance at Beginning of Year		6.4	6.2	6.2
Additions Charged to Costs and Expenses		5.6	2.3	3.1
Additions Charged to Other Accounts	[1]	0	0.1	0
Deductions	[2]	2.1	2.2	3.1
Balance at End of Year		$ 9.9	$ 6.4	$ 6.2
[1]	Additions charged to other accounts are comprised of amounts related to fluctuations in the foreign currency exchange rate.
[2]	Deductions include amounts deemed to reduce exposure of probable losses, amounts deemed uncollectible, and amounts related to fluctuations in the foreign currency exchange rate.