Cincinnati Financial (CINF) 10-K 23 Feb 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2017	Feb. 19, 2018	Jun. 30, 2017
Document Documentand Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Entity Registrant Name	CINCINNATI FINANCIAL CORP
Entity Central Index Key	20,286
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		163,988,318
Entity Public Float			$ 11,075,393,319

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Investments
Fixed maturities, at fair value (amortized cost: 2017—$10,314; 2016—$9,799)	$ 10,699	$ 10,085
Equity securities, at fair value (cost: 2017—$3,094; 2016—$2,995)	6,249	5,334
Other invested assets	103	81
Total investments	17,051	15,500
Cash and cash equivalents	657	777
Investment income receivable	134	134
Finance receivable	61	51
Premiums receivable	1,589	1,533
Reinsurance recoverable	432	545
Prepaid reinsurance premiums	42	62
Deferred policy acquisition costs	670	637
Land, building and equipment, net, for company use (accumulated depreciation: 2017—$253; 2016—$237)	185	183
Other assets	216	198
Separate accounts	806	766
Total assets	21,843	20,386
Insurance reserves
Loss and loss expense reserves	5,273	5,085
Life policy and investment contract reserves	2,729	2,671
Unearned premiums	2,404	2,307
Other liabilities	792	786
Deferred income tax	745	865
Note payable	24	20
Long-term debt and capital lease obligations	827	826
Separate accounts	806	766
Total liabilities	13,600	13,326
Commitments and contingent liabilities (Note 16)	0	0
Shareholders' Equity
Common stock, par value—$2 per share; (authorized: 2017 and 2016—500 million shares; issued: 2017 and 2016—198.3 million shares)	397	397
Paid-in capital	1,265	1,252
Retained earnings	5,180	5,037
Accumulated other comprehensive income	2,788	1,693
Treasury stock at cost (2017—34.4 million shares and 2016—33.9 million shares)	(1,387)	(1,319)
Total shareholders' equity	8,243	7,060
Total liabilities and shareholders' equity	$ 21,843	$ 20,386

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) shares in Millions, $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Fixed maturities, amortized cost	$ 10,314	$ 9,799
Equity securities, cost	3,094	2,995
Land, building and equipment, accumulated depreciation	$ 253	$ 237
Common stock, par value	$ 2	$ 2
common stock, authorized	500	500
Common stock, issued	198.3	198.3
Common stock, shares outstanding	198.3	198.3
Treasury stock, shares	34.4	33.9

Consolidated Statements Of Inco

Consolidated Statements Of Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues
Earned premiums	$ 4,954	$ 4,710	$ 4,480
Investment income, net of expenses	609	595	572
Total	148	124	70
Fee revenues	16	15	13
Other revenues	5	5	7
Total revenues	5,732	5,449	5,142
Benefits and Expenses
Insurance losses and contract holders' benefits	3,390	3,107	2,808
Underwriting, acquisition and insurance expenses	1,546	1,465	1,387
Interest expense	53	53	53
Other operating expenses	13	12	13
Total benefits and expenses	5,002	4,637	4,261
Income Before Income Taxes	730	812	881
Provision (Benefit) for Income Taxes
Current	129	183	231
Deferred	(444)	38	16
Total provision (benefit) for income taxes	(315)	221	247
Net Income	$ 1,045	$ 591	$ 634
Per Common Share
Net income—basic (in usd per share)	$ 6.36	$ 3.59	$ 3.87
Net income—diluted (in usd per share)	$ 6.29	$ 3.55	$ 3.83

Consolidated Statements Of Comp

Consolidated Statements Of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net Income	$ 1,045	$ 591	$ 634
Other Comprehensive Income
Change in unrealized gains and losses on investments, net of tax of $317, $186 and $(220), respectively	598	345	(405)
Amortization of pension actuarial gains and losses and prior service cost, net of tax of $7, $6 and $(2), respectively	7	10	(4)
Change in life deferred acquisition costs, life policy reserves and other, net of tax of $1, $(4) and $4, respectively	(2)	(6)	9
Other comprehensive income (loss)	603	349	(400)
Comprehensive Income	$ 1,648	$ 940	$ 234

Consolidated Statements of Com6

Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Unrealized gains on investments available-for-sale, net of tax	$ 317	$ 186	$ (220)
Amortization of pension actuarial loss and prior service cost, net of tax	7	6	(2)
Change in life deferred acquisition costs, life policy reserves and other, net of tax	$ 1	$ (4)	$ 4

Consolidated Statements Of Shar

Consolidated Statements Of Shareholders' Equity - USD ($) shares in Thousands, $ in Millions	Total	Common Stock	Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Income	Treasury Stock	New Accounting Pronouncement, Early Adoption, EffectRetained Earnings	New Accounting Pronouncement, Early Adoption, EffectAccumulated Other Comprehensive Income
Beginning Balance at Dec. 31, 2014		$ 397	$ 1,214	$ 4,505	$ 1,744	$ (1,287)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based awards		0	(7)			41
Share-based compensation			20
Other			5			7
Net Income	$ 634			634
Dividends declared				(377)
Other comprehensive income (loss)	(400)				(400)
Shares acquired - share repurchase authorization						(53)
Shares acquired - share-based compensation plans						(16)
Ending Balance at Dec. 31, 2015	6,427	$ 397	1,232	4,762	1,344	(1,308)
Beginning Balance (in shares) at Dec. 31, 2014		163,700
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based awards (in shares)		1,300
Shares acquired—share repurchase authorization (in shares)		(1,000)
Shares acquired - share-based compensation plans (in shares)		(300)
Other (in shares)		200
Ending Balance (in shares) at Dec. 31, 2015		163,900
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adjustment to reclassify certain tax effects from AOCI to retained earnings | Accounting Standards Update 2018-02							$ 0	$ 0
Share-based awards		$ 0	(8)			36
Share-based compensation			23
Other			5			5
Net Income	591			591
Dividends declared				(316)
Other comprehensive income (loss)	349				349
Shares acquired - share repurchase authorization						(39)
Shares acquired - share-based compensation plans						(13)
Ending Balance at Dec. 31, 2016	$ 7,060	$ 397	1,252	5,037	1,693	(1,319)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based awards (in shares)		1,000
Shares acquired—share repurchase authorization (in shares)		(500)
Shares acquired - share-based compensation plans (in shares)		(200)
Other (in shares)		200
Ending Balance (in shares) at Dec. 31, 2016	198,300	164,400
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adjustment to reclassify certain tax effects from AOCI to retained earnings | Accounting Standards Update 2018-02							0	0
Share-based awards		$ 0	(18)			26
Share-based compensation			26
Other			5			5
Net Income	$ 1,045			1,045
Dividends declared				(410)
Other comprehensive income (loss)	603				603
Shares acquired - share repurchase authorization						(92)
Shares acquired - share-based compensation plans						(7)
Ending Balance at Dec. 31, 2017	$ 8,243	$ 397	$ 1,265	$ 5,180	$ 2,788	$ (1,387)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based awards (in shares)	527	800
Shares acquired—share repurchase authorization (in shares)		(1,300)
Shares acquired - share-based compensation plans (in shares)		(100)
Other (in shares)		100
Ending Balance (in shares) at Dec. 31, 2017	198,300	163,900
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adjustment to reclassify certain tax effects from AOCI to retained earnings | Accounting Standards Update 2018-02							$ (492)	$ 492

Consolidated Statements Of Cash

Consolidated Statements Of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash Flows From Operating Activities
Net Income	$ 1,045	$ 591	$ 634
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	55	48	52
Realized investment gains, net	(148)	(124)	(70)
Share-based compensation	26	23	20
Interest credited to contract holders'	48	48	44
Deferred income tax expense	(444)	38	16
Changes in:
Investment income receivable	0	(5)	(6)
Premiums and reinsurance receivable	77	(113)	(48)
Deferred policy acquisition costs	(36)	(26)	(18)
Other assets	(43)	34	(39)
Loss and loss expense reserves	188	367	233
Life policy and investment contract reserves	96	102	101
Unearned premiums	97	106	119
Other liabilities	24	61	55
Current income tax receivable/payable	67	(35)	(18)
Net cash provided by operating activities	1,052	1,115	1,075
Cash Flows From Investing Activities
Sale of fixed maturities	23	15	43
Call or maturity of fixed maturities	1,172	1,511	1,199
Sale of equity securities	523	465	342
Purchase of fixed maturities	(1,723)	(1,994)	(1,722)
Purchase of equity securities	(513)	(439)	(493)
Investment in finance receivables	(32)	(17)	(14)
Collection of finance receivables	23	30	30
Investment in buildings and equipment	(16)	(13)	(10)
Change in other invested assets, net	(15)	(14)	1
Net cash used in investing activities	(558)	(456)	(624)
Cash Flows From Financing Activities
Payment of cash dividends to shareholders	(400)	(306)	(366)
Shares acquired - share repurchase authorization	(92)	(39)	(53)
Changes in note payable	4	(15)	(14)
Proceeds from stock options exercised	13	21	24
Contract holders' funds deposited	79	95	83
Contract holders' funds withdrawn	(164)	(155)	(148)
Excess tax benefits on share-based compensation	0	5	4
Other	(54)	(32)	(28)
Net cash used in financing activities	(614)	(426)	(498)
Net change in cash and cash equivalents	(120)	233	(47)
Cash and cash equivalents at beginning of year	777	544	591
Cash and cash equivalents at end of year	657	777	544
Supplemental Disclosures of Cash Flow Information
Interest paid	52	52	52
Income taxes paid	60	213	245
Noncash Activities
Conversion of securities	5	4	3
Equipment acquired under capital lease obligations	14	20	20
Cashless exercise of stock options	7	13	16
Other assets and other liabilities	$ 75	$ 53	$ 27

Summary Of Significant Accounti

Summary Of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Summary Of Significant Accounting Policies	Summary of Significant Accounting Policies Nature of Operations Cincinnati Financial Corporation (CFC) operates through our insurance group and two complementary subsidiary companies. The Cincinnati Insurance Company leads our insurance group that also includes two subsidiaries: The Cincinnati Casualty Company and The Cincinnati Indemnity Company. This group markets a broad range of standard market commercial and personal policies. The group focuses on delivery of quality customer service to our select group of 1,702 independent insurance agencies with 2,256 reporting locations across 42 states. Other subsidiaries of The Cincinnati Insurance Company include The Cincinnati Life Insurance Company, which markets life and disability income insurance and fixed annuities, and The Cincinnati Specialty Underwriters Insurance Company, which offers excess and surplus lines property casualty insurance products. The Cincinnati Insurance Company also conducts the business of our reinsurance assumed operations, Cincinnati Re SM . The two CFC complementary subsidiaries are CSU Producer Resources Inc., which provides insurance brokerage services to our independent agencies so their clients can access our excess and surplus lines insurance products, and CFC Investment Company, which offers commercial leasing and financing services to our agents, their clients and other customers. Basis of Presentation Our consolidated financial statements include the accounts of the parent and its wholly owned subsidiaries and are presented in conformity with accounting principles generally accepted in the United States of America (GAAP). All intercompany balances and transactions have been eliminated in consolidation. The preparation of the consolidated financial statements in conformity with GAAP requires us to make estimates and assumptions that affect amounts reported in the consolidated financial statements and accompanying notes. Our actual results could differ from those estimates. Investments Our portfolio investments are primarily in publicly traded fixed-maturity and equity security investments. Fixed-maturity investments (taxable bonds, tax-exempt bonds, redeemable preferred equities and commercial mortgage- backed securities) and equity investments (common and nonredeemable preferred equities) are classified as available for sale and recorded at fair value in the consolidated financial statements. The number of fixed-maturity securities with fair value below 100 percent of amortized cost can be expected to fluctuate as interest rates rise or fall. Because of our strong capital and long-term investment horizon, our general intent is to hold fixed-maturity investments until maturity, regardless of short-term fluctuations in fair values. Impairment charges for fixed maturities are recorded for other-than-temporary declines in value if fair value is below amortized cost and, in the asset impairment committee’s judgment, the fair value is not expected to be recouped within a designated recovery period. Our invested asset impairment policy also states that fixed maturities below their amortized cost that the company (1) intends to sell or (2) more likely than not will be required to sell before recovery of their amortized cost basis are deemed to be other-than-temporarily impaired (OTTI). The amortized cost of any such securities is reduced to fair value as the new cost basis, and a realized loss is recorded in the period in which it is recognized. When these two criteria are not met, and the company believes that full collection of interest and/or principal is not likely, we determine the net present value of future cash flows by using the effective interest rate implicit in the security at the date of acquisition as the discount rate and compare that amount with the amortized cost and fair value of the security. The difference between the net present value of the expected future cash flows and amortized cost of the security is considered a credit loss and recognized as a realized loss in the period in which it occurred. The difference between the fair value and the net present value of the cash flows of the security, the noncredit loss, is recognized in other comprehensive income as an unrealized loss. We had no fixed-maturity securities with a noncredit loss for the years ended 2017 , 2016 and 2015 . When determining OTTI charges for our equity portfolio, our invested asset impairment policy considers qualitative and quantitative factors, including facts and circumstances specific to individual securities; asset classes; the financial condition of the issuer; changes in dividend payment; the length of time fair value had been less than cost; the severity of the decline in fair value below cost; the volatility of the security; and our ability and intent to hold each position until its forecasted recovery. We include the noncredit portion of fixed-maturity OTTI charges and all other unrealized gains and losses on investments, net of taxes, in shareholders’ equity as accumulated other comprehensive income (AOCI). Realized gains and losses on investments are recognized in net income based on the trade date accounting method. Included within our other invested assets were $31 million and $31 million of life policy loans, $35 million and $23 million of private equity investments and $37 million and $27 million of real estate through direct property ownership and development projects in the United States at December 31, 2017 and 2016, respectively. Life policy loans are carried at the receivable value. The private equity investments provide their financial statements to us and generally report investments on their balance sheets at fair value. We use the equity method of accounting for private equity and real estate development investments. Investment income, net of expenses, consists mainly of interest and dividends. We record interest on an accrual basis and record dividends at the ex-dividend date. We amortize premiums and discounts on fixed-maturity securities using the effective interest method over the expected life of the security. Fair Value Disclosures Fair value is defined as the exit price or the amount that would be (1) received to sell an asset or (2) paid to transfer a liability in an orderly transaction between marketplace participants at the measurement date. When determining an exit price, we rely upon observable market data whenever possible. We primarily base fair value for investments in equity and fixed-maturity securities (including redeemable preferred stock and assets held in separate accounts) on quoted market prices or on prices from the company’s nationally recognized pricing vendor, an outside resource that supplies global securities pricing, dividend, corporate action and descriptive information to support fund pricing, securities operations, research and portfolio management. The company obtains and reviews the pricing service’s valuation methodologies and related inputs and validates these prices by replicating a sample across each asset class using a discounted cash flow model. When a price is not available from these sources, as in the case of securities that are not publicly traded, we determine the fair value using various inputs including quotes from independent brokers. The fair value of investments not priced by the company’s nationally recognized pricing vendor is less than 1 percent of the fair value of our total investment portfolio. For the purpose of ASC 825 disclosure, we estimate the fair value of our long-term senior notes on market pricing of similar debt instruments that are actively trading. We estimate the fair value of our note payable on the year-end outstanding balance because it is short term and tied to a variable interest rate. We estimate the fair value of liabilities for investment contracts and annuities using discounted cash flow calculations across a wide range of economic interest rate scenarios with a provision for our nonperformance risk. We estimate the fair value for policyholder loans on insurance contracts using a discounted cash flow model. Determination of fair value for structured settlements assumes the discount rates used to calculate the present value of expected payments are the risk-free spot rates plus an A3 rated bond spread for financial issuers at December 31, 2017 , to account for nonperformance risk. See Note 3, Fair Value Measurements, for further details. Cash and Cash Equivalents Cash and cash equivalents are highly liquid instruments that include liquid debt instruments with original maturities of less than three months. These are carried at cost, which approximates fair value. Property Casualty Insurance The consolidated property casualty companies actively write property casualty insurance through independent agencies in 42 states. Our 10 largest states generated 59.7 percent and 61.4 percent of total earned premiums in 2017 and 2016 , respectively. Ohio, our largest state, accounted for 16.2 percent and 16.8 percent of total earned premiums in 2017 and 2016 , respectively. Illinois, Georgia, Indiana, North Carolina, Pennsylvania and Michigan each accounted for between 5 percent and 7 percent of total earned premiums in 2017 . Our largest single agency relationship accounted for approximately 0.8 percent of our total property casualty earned premiums in 2017 . No aggregate agency relationship locations under a single ownership structure accounted for more than 4 percent of our total property casualty earned premiums in 2017 . We record revenues for installment charges as fee revenues in the consolidated statements of income. Property casualty written premiums are deferred and recorded as earned premiums on a pro rata basis over the terms of the policies. We record as unearned premiums the portion of written premiums that applies to unexpired policy terms. Expenses associated with successfully acquiring insurance policies – commissions, premium taxes and underwriting costs – are deferred and amortized over the terms of the policies. We assess recoverability of deferred acquisition costs at a level consistent with the way we acquire, service and manage insurance policies and measure profitability. We analyze our acquisition cost assumptions to reflect actual experience, and we evaluate potential premium deficiencies. Certain property casualty policies are not entered into policy underwriting systems as of the effective date of coverage. An estimate is recorded for these unprocessed written premiums. A large majority of the estimate is unearned and has no material impact on earned premiums. Premiums receivable are reviewed for impairment on a quarterly basis. We maintain an allowance for uncollectible premiums. We establish reserves to cover the expected cost of claims, losses and expenses related to investigating, processing and resolving claims. Although the appropriate amount of reserves is inherently uncertain, we base our decisions on past experience and current facts. Reserves are based on claims reported prior to the end of the year and estimates of unreported claims. We regularly review and update reserves using the most current information available. Any resulting adjustments are reflected in current calendar year insurance losses and policyholder benefits. We estimate that we may recover some of our costs through salvage and subrogation. Policyholder Dividends Certain workers’ compensation policies include the possibility of a policyholder earning a return of a portion of premium in the form of a policyholder dividend. The dividend generally is calculated by determining the profitability of a policy year along with the associated premium. We reserve for all probable future policyholder dividend payments. We record policyholder dividends as other underwriting expenses. Life Insurance We offer several types of life insurance and disability income insurance, and we account for each according to the duration of the contract. Short-duration life and health contracts are written to cover claims that arise during a short, fixed term of coverage. We generally have the right to change the amount of premium charged or cancel the coverage at the end of each contract term. We record premiums for short-duration life and health contracts similarly to property casualty contracts. Long-duration contracts are written to provide coverage for an extended period of time. Traditional long-duration contracts require policyholders to pay scheduled gross premiums, generally not less frequently than annually, over the term of the coverage. Premiums for these contracts, such as whole life insurance and disability income insurance, are recognized as revenue when due. Some traditional long-duration contracts, such as ten-pay whole life insurance, have premium payment periods shorter than the period over which coverage is provided. For these contracts, the excess of premium over the amount required to pay expenses and benefits is recognized over the term of the coverage rather than over the premium payment period. We establish a liability for traditional long-duration contracts as we receive premiums. The amount of this liability is the present value of future expenses and benefits less the present value of future net premiums. Net premium is the portion of gross premium required to provide for all expenses and benefits. We estimate future expenses and benefits and net premium using assumptions for expected expenses, mortality, morbidity, withdrawal rates and investment income. We include a provision for deviation, meaning we allow for some uncertainty in making our assumptions. We establish our assumptions when the contract is issued, and we generally maintain those assumptions for the life of the contract. We use both our own experience and industry experience, adjusted for historical trends, in arriving at our assumptions for expected mortality, morbidity and withdrawal rates. We use our own experience and historical trends for setting our assumption for expected expenses. We base our assumption for expected investment income on our own experience, adjusted for current economic conditions. We capitalize acquisition costs for traditional long-duration contracts. We charge these capitalized costs associated with successfully acquiring traditional long-duration contract insurance policies in proportion to premium revenue recognized. We use the same assumptions used in establishing the liability for the contract. We update our acquisition cost assumptions periodically to reflect actual experience, and we evaluate our deferred acquisition costs for recoverability. Universal life contracts are long-duration contracts for which contractual provisions are not fixed, unlike whole life insurance. Universal life contracts allow policyholders to vary the amount of premium, within limits, without our consent. However, we may vary the mortality, expense charges and the interest crediting rate, within limits, used to accumulate policy values. We do not record universal life premiums as revenue. Instead we recognize as revenue the mortality charges, administration charges and surrender charges when received. Some of our universal life contracts assess administration charges in the early years of the contract that are compensation for services we will provide in the later years of the contract. These administration charges are deferred and are recognized over the period when we provide those future services. We maintain a policy reserve liability equal to the policyholder account value. There is no provision for adverse deviation. Some of our universal life policies contain no-lapse guarantee provisions. For these policies, we establish a reserve in addition to the account balance, based on expected no-lapse guarantee benefits and expected policy assessments. We capitalize acquisition costs associated with successfully acquiring universal life long-duration contracts. We charge these capitalized costs to expenses over the term of coverage of the contract in accordance with the recognition of gross profit from the contract. When we charge deferred policy acquisition costs to expenses, we use assumptions based on our best estimates of long-term experience. We review and modify these assumptions on a regular basis. Separate Accounts We have issued universal life contracts with guaranteed minimum returns, referred to as bank-owned life insurance contracts (BOLIs). A BOLI is designed so the bank is the policy owner and the policy beneficiary. We legally segregate and record as separate accounts the assets and liabilities for some of our BOLIs, based on the specific contract provisions. We guarantee minimum investment returns, account values and death benefits for our separate account BOLIs. Our other BOLIs are general account products. We carry the assets of separate account BOLIs at fair value. The liabilities on separate account BOLIs primarily are the contract holders’ claims to the related assets and are carried at an amount equal to the contract holders’ account value. At December 31, 2017 , the current fair value of the BOLI invested assets and cash exceeded the current fair value of the contract holders’ account value by approximately $29 million . If the BOLI projected fair value were to fall below the value we guaranteed, a liability would be established with a corresponding charge to the company’s earnings. Generally, investment income and realized investment gains and losses of the separate accounts accrue directly to the contract holder, and we do not include them in the consolidated statements of income. Revenues and expenses related to separate accounts consist of contractual fees and mortality, surrender and expense risk charges. Also, each separate account BOLI includes a negotiated capital gain and loss sharing arrangement between the company and the bank. A percentage of each separate account’s realized capital gain and loss representing contract fees and assessments accrues to us and is transferred from the separate account to our general account and is recognized as revenue or expense. We record as revenues separate account investment management fees in fee revenues of the consolidated statements of income. Reinsurance The Cincinnati Insurance Company offers reinsurance assumed for casualty and specialty (predominantly domestic exposure) and property (worldwide exposure). Treaties are written on a pro rata and excess of loss basis. We also continue to assume risk with limited exposure as a reinsurer for involuntary state pools. Written premium is recorded, net of contract specific retrocessions, on an ultimate estimate basis and earned on a pro rata basis over the coverage period of the treaty. Expenses are recorded as per contract terms and deferred over the earning period of the premium. We establish known loss reserves when reported. We establish reserves for losses in excess of reported activity in the form of IBNR. Reserves are established using actuarial analysis which includes models and methods traditionally used for the types of exposures written. We establish reserves for event specific occurrences using modeling data and company specific data when available. We enter into other reinsurance transactions to reduce risk and uncertainty by buying property casualty reinsurance and retrocessional reinsurance as well as life reinsurance. Reinsurance and retrocessional reinsurance contracts do not relieve us from our obligation to policyholders, but rather help protect our financial strength to perform that duty. All of these ceded reinsurance contracts transfer the economic risk of loss. Premiums that we cede are deferred and recorded as earned premiums on a pro rata basis over the terms of the contracts. We estimate loss amounts recoverable from our reinsurers based on the reinsurance policy terms. Historically, our claims with reinsurers have been paid. We establish an insignificant allowance for uncollectible reinsurance. Income Taxes We calculate deferred income tax liabilities and assets using tax rates in effect when temporary differences in the consolidated financial statement income and taxable income are expected to reverse. We recognize deferred income taxes for numerous temporary differences between our taxable income and consolidated financial statement income and other changes in shareholders’ equity. Such temporary differences relate primarily to unrealized gains and losses on investments and differences in the recognition of deferred acquisition costs, unearned premiums, insurance reserves and basis differences in the carrying value of investments held. We charge deferred income taxes associated with balances that impact other comprehensive income, such as unrealized appreciation and depreciation of investments (except the amount related to the effect of income tax rate changes), to shareholders’ equity in accumulated other comprehensive income (AOCI). We charge deferred taxes associated with other differences to income. Although no Internal Revenue Service (IRS) penalties currently are accrued, if incurred, they would be recognized as a component of income tax expense. The Tax Cuts and Jobs Act (the “Tax Act”) was enacted on December 22, 2017, and reduced U.S. corporate income tax rates from 35 percent to 21 percent . The effect of the rate change was recorded as a one-time noncash benefit to income tax expense in our consolidated statements of income for the year ended December 31, 2017. See Note 11, Income Taxes, for further detail on the Tax Act, our uncertain tax positions and other income tax items. Earnings per Share Net income per common share is based on the weighted average number of common shares outstanding during each of the respective years. We calculate net income per common share (diluted) assuming the exercise or conversion of share‑based awards using the treasury stock method. Land, Building and Equipment We record land at cost, and record building and equipment at cost less accumulated depreciation. Equipment held under capital leases also is classified as property and equipment with the related lease obligations recorded as liabilities. We capitalize and amortize costs for internally developed computer software during the application development stage. These costs generally consist of external consulting, internal payroll and payroll-related costs. Our depreciation is based on estimated useful lives (ranging from three years to 39.5 years) using straight-line and accelerated methods. Depreciation expense was $28 million for 2017 , $30 million for 2016 and $36 million for 2015 . We review our accumulated depreciation for our building, equipment and software assets and write off fully depreciated assets for obsolesce and nonuse. We monitor land, building and equipment and software assets for potential impairments. Potential impairments may include a significant decrease in the fair values of the assets, considerable cost overruns on projects, a change in legal factors or business climate or other factors that indicate that the carrying amount may not be recoverable or useful. There were no recorded land, building and equipment impairments for 2017 , 2016 or 2015 . Finance Receivables Our leasing subsidiary provides auto and equipment direct financing (leases and loans) to commercial and individual clients. We generally transfer ownership of the property to the client as the terms of the leases expire. Our lease contracts contain bargain purchase options. We account for these leases and loans as direct financing-type leases. We capitalize and amortize lease or loan origination costs over the life of the financing, using the effective interest method. These costs may include, but are not limited to finder fees, broker fees, filing fees and the cost of credit reports. We record income as other revenues over the financing term using the effective interest method in the consolidated statements of income. Finance receivables are reviewed for impairment and are insignificant to our consolidated financial position, results of operations and cash flows. Employee Benefit Pension Plan We sponsor a defined benefit pension plan that was modified during 2008. We closed entry into the pension plan, and only participants 40 years of age or older could elect to remain in the plan. Our pension expense is based on certain actuarial assumptions and also is composed of several components that are determined using the projected unit credit actuarial cost method. Refer to Note 13, Employee Retirement Benefits, for more information about our defined benefit pension plan. Share-Based Compensation We grant qualified and nonqualified share-based compensation under authorized plans. The stock options generally vest on a graded scale over three years following the date of grant and are exercisable over 10 -year periods. We grant service-based restricted stock units that cliff vest three years after the date of grant as well as service-based restricted stock units that vest ratably over the three -year vesting term. We also grant performance-based restricted stock units that vest if certain market conditions are attained. In 2017 , the CFC compensation committee approved share-based awards including incentive stock options, nonqualified stock options, service-based restricted and performance-based restricted stock units. See Note 17, Share-Based Associate Compensation Plans, for further details. Subsequent Events There were no subsequent events requiring adjustment to the consolidated financial statements or disclosure. Adopted Accounting Updates ASU 2016-07, Investments - Equity Method and Joint Ventures (Topic 323): Simplifying the Transition to the Equity Method of Accounting In March 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2016-07, Equity Method and Joint Ventures (Topic 323): Simplifying the Transition to the Equity Method of Accounting. ASU 2016-07 eliminates the requirement to retroactively adjust an investment, results of operations, and retained earnings once an investment qualifies for use of the equity method. It requires the equity method investor to add the cost of acquiring the additional interest in the investee to the current basis of the investor's previously held interest and adopt the equity method of accounting as of the date the investment becomes qualified for equity method accounting without retroactive adjustment. The effective date of ASU 2016-07 was for interim and annual reporting periods beginning after December 15, 2016, and was applied prospectively. The company adopted this ASU effective January 1, 2017, and it did not have a material impact on our company's consolidated financial position, cash flows or results of operations. ASU 2016-09, Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting In March 2016, the FASB issued ASU 2016-09, Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting. ASU 2016-09 simplifies several aspects of the accounting for share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities, and classification on the statement of cash flows. The effective date of ASU 2016-09 was for interim and annual reporting periods beginning after December 15, 2016. The recognition and classification of the excess tax benefit provisions were applied prospectively in the results of operations and statement of cash flows. This adoption resulted in excess tax benefits of $7 million for the year ended December 31, 2017, which reduced our current provision for income taxes in our results of operations. The statutory tax withholding classification, which are cash payments made to taxing authorities for shares withheld, were applied retrospectively and reclassified the statutory tax withholding requirements in the statement of cash flows from Other liabilities in operating activities to Other in financing activities. This statutory tax withholding reclassification resulted in $13 million , $12 million and $11 million being included in financing activities for the years ended December 31, 2017, 2016 and 2015, respectively. There were no cumulative effect adjustments upon adoption of this ASU. ASU 2018-02, Income Statement—Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income In February 2018, the FASB issued ASU 2018-02, Income Statement - Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income (“AOCI”). ASU 2018-02 eliminates the stranded tax effects within AOCI resulting from the application of current GAAP in response to the change in the U.S. corporate income tax rate from 35 percent to 21 percent as part of the Tax Act. Stranded tax effects unrelated to the Tax Act are released from AOCI using the security-by-security approach. The effective date of ASU 2018-02 is for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years with early adoption permitted for public entities for which financial statements had not yet been issued. The company elected to early adopt ASU 2018-02 effective for the year ended December 31, 2017, and applied the provisions retrospectively within our consolidated balance sheets and statements of shareholders' equity. This adoption resulted in a one-time reclassification of the effect of remeasuring deferred tax liabilities related to items, primarily unrealized gains and losses on investments, within AOCI to retained earnings resulting from the change in the U.S. corporate income tax rate. This reclassification resulted in an increase to AOCI and a decrease to retained earnings in the amount of $492 million for the year ended December 31, 2017, with no net impact to total shareholders' equity. Pending Accounting Updates ASU 2014-09 Revenue from Contracts with Customers In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers . ASU 2014-09 requires an entity to recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods and services. Insurance contracts do not fall within the scope of this ASU. The effective date of ASU 2014-09 is for interim and annual reporting periods beginning after December 15, 2017. The ASU has not yet been adopted and will not have a material impact on our company’s consolidated financial position, cash flows or results of operations. ASU 2016-01, Financial Instruments - Overall (Subtopic 825-10) - Recognition and Measurement of Financial Assets and Financial Liabilities In January 2016, the FASB issued ASU 2016-01, Financial Instruments - Overall (Subtopic 825-10) - Recognition and Measurement of Financial Assets and Financial Liabilities. ASU 2016-01 revises the accounting related to the classification and measurement of investments in equity securities and the presentation of certain fair value changes for financial liabilities measured at fair value. Our results of operations will be impacted as changes in fair value of equity securities will be reported in net income instead of other comprehensive income. The effective date of ASU 2016-01 is for interim and annual reporting periods beginning after December 15, 2017, and will be applied prospectively. The ASU has not yet been adopted. Upon adoption of this ASU on January 1, 2018, $2.503 billion of after-tax unrealized gains on equity securities will be reclassified from AOCI to retained earnings. ASU 2016-02, Leases (Topic 842) In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842). The main provision of ASU 2016-02 requires the recognition of lease assets and lease liabilities by lessees for those leases classified as operating leases under previous GAAP. The effective date of ASU 2016-02 is for interim and annual reporting periods beginning after December 15, 2018. The ASU has not yet been adopted; however, it is not expected to have a material impact on our company's consolidated financial position, cash flows or results of operations. ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments . ASU 2016-13 amends previous guidance on the impairment of financial instruments by adding an impairmen

Investments

Investments	12 Months Ended
	Dec. 31, 2017
Investments [Abstract]
Investments	Investments The following table provides cost or amortized cost, gross unrealized gains, gross unrealized losses and fair value for our fixed-maturity and equity securities: (Dollars in millions) Cost or amortized cost Gross unrealized Fair At December 31, 2017 gains losses Fixed-maturity securities: Corporate $ 5,420 $ 246 $ 13 $ 5,653 States, municipalities and political subdivisions 4,316 155 6 4,465 Commercial mortgage-backed 280 7 1 286 Government-sponsored enterprises 257 1 4 254 United States government 31 — — 31 Foreign government 10 — — 10 Subtotal 10,314 409 24 10,699 Equity securities: Common equities 2,918 3,135 14 6,039 Nonredeemable preferred equities 176 34 — 210 Subtotal 3,094 3,169 14 6,249 Total $ 13,408 $ 3,578 $ 38 $ 16,948 At December 31, 2016 Fixed-maturity securities: Corporate $ 5,555 $ 252 $ 26 $ 5,781 States, municipalities and political subdivisions 3,770 100 42 3,828 Commercial mortgage-backed 282 7 2 287 Government-sponsored enterprises 167 — 3 164 United States government 10 — — 10 Foreign government 10 — — 10 Convertibles and bonds with warrants attached 5 — — 5 Subtotal 9,799 359 73 10,085 Equity securities: Common equities 2,812 2,320 9 5,123 Nonredeemable preferred equities 183 28 — 211 Subtotal 2,995 2,348 9 5,334 Total $ 12,794 $ 2,707 $ 82 $ 15,419 The net unrealized investment gains in our fixed-maturity portfolio at December 31, 2017 , are primarily the result of the continued low interest rate environment that increased the fair value of our fixed-maturity portfolio. Our commercial mortgage-backed securities had an average rating of Aa1/AA at December 31, 2017 and 2016 . The seven largest net unrealized investment gains in our common stock portfolio are from JP Morgan Chase & Co. (NYSE:JPM), Honeywell International Incorporated (NYSE:HON), BlackRock Inc. (NYSE:BLK), Microsoft Corporation (Nasdaq:MFST), Apple Inc. (Nasdaq:AAPL), 3M Company (NYSE:MMM) and Johnson and Johnson (NYSE:JNJ), which had a combined gross unrealized gain of $1.013 billion . At December 31, 2017 , JP Morgan Chase & Co. was our largest single equity holding with a fair value of 4.0 percent of our publicly traded common equities portfolio and 1.4 percent of the total investment portfolio. The table below provides fair values and unrealized losses by investment category and by the duration of the securities’ continuous unrealized loss positions: (Dollars in millions) Less than 12 months 12 months or more Total At December 31, 2017 Fair value Unrealized losses Fair value Unrealized losses Fair value Unrealized losses Fixed-maturity securities: Corporate $ 330 $ 4 $ 252 $ 9 $ 582 $ 13 States, municipalities and political subdivisions 88 1 264 5 352 6 Commercial mortgage-backed 33 — 36 1 69 1 Government-sponsored enterprises 96 1 124 3 220 4 Foreign government 10 — — — 10 — United States government 23 — 6 — 29 — Subtotal 580 6 682 18 1,262 24 Equity securities: Common equities 229 14 — — 229 14 Subtotal 229 14 — — 229 14 Total $ 809 $ 20 $ 682 $ 18 $ 1,491 $ 38 At December 31, 2016 Fixed-maturity securities: Corporate $ 733 $ 15 $ 189 $ 11 $ 922 $ 26 States, municipalities and political subdivisions 989 42 — — 989 42 Commercial mortgage-backed 89 2 2 — 91 2 Government-sponsored enterprises 155 3 — — 155 3 United States government 6 — — — 6 — Subtotal 1,972 62 191 11 2,163 73 Equity securities: Common equities 103 9 — — 103 9 Nonredeemable preferred equities 4 — — — 4 — Subtotal 107 9 — — 107 9 Total $ 2,079 $ 71 $ 191 $ 11 $ 2,270 $ 82 Contractual maturity dates for fixed-maturity investments were: (Dollars in millions) Amortized cost Fair value % of fair value At December 31, 2017 Maturity dates: Due in one year or less $ 511 $ 519 4.9 % Due after one year through five years 2,736 2,839 26.5 Due after five years through ten years 3,921 4,058 37.9 Due after ten years 3,146 3,283 30.7 Total $ 10,314 $ 10,699 100.0 % Actual maturities may differ from contractual maturities when there is a right to call or prepay obligations with or without call or prepayment penalties. At December 31, 2017 and 2016 , the company had fixed-maturity investments with a fair value of $101 million and $72 million , respectively, on deposit with various states in compliance with regulatory requirements. In addition, cash and fixed-maturity investments deposited with third parties used as collateral to secure liabilities on behalf of insureds, cedants and other creditors had a fair value of $57 million and $22 million at December 31, 2017 and 2016 , respectively. In the normal course of investing activities, the company enters into investments in limited partnerships, including private equity and real estate investments, and asset-backed securities issued by third-parties. The company’s maximum exposure to loss with respect to these investments is limited to the investment carrying values included in the company’s consolidated balance sheets and any unfunded commitments. The following table provides investment income and realized investment gains and losses: (Dollars in millions) Years ended December 31, 2017 2016 2015 Investment income: Interest $ 445 $ 440 $ 428 Dividends 170 161 150 Other 4 3 3 Total 619 604 581 Less investment expenses 10 9 9 Total $ 609 $ 595 $ 572 Realized investment gains and losses: Fixed maturities: Gross realized gains $ 25 $ 26 $ 18 Gross realized losses — (1 ) — Other-than-temporary impairments (6 ) (2 ) (18 ) Equity securities: Gross realized gains 195 152 129 Gross realized losses (72 ) (53 ) (26 ) Other-than-temporary impairments (3 ) — (34 ) Other 9 2 1 Total $ 148 $ 124 $ 70 For the years ended December 31, 2017 , 2016 and 2015 , there were no credit losses on fixed-maturity securities for which a portion of OTTI has been recognized in other comprehensive income. During 2017 , we other-than-temporarily impaired six securities. At December 31, 2017 , 249 fixed-maturity investments with a total unrealized loss of $18 million had been in an unrealized loss position for 12 months or more. Of that total, no fixed-maturity investments had fair values below 70 percent of amortized cost. There were no equity security investments in an unrealized loss position for 12 months or more as of December 31, 2017 . During 2016 , we other-than-temporarily impaired four securities. At December 31, 2016 , 32 fixed-maturity investments with a total unrealized loss of $11 million had been in an unrealized loss position for 12 months or more. Of that total, no fixed-maturity investments had fair values below 70 percent of amortized cost. There were no equity security investments in an unrealized loss position for 12 months or more as of December 31, 2016 . During 2015 , we other-than-temporarily impaired 20 securities. At December 31, 2015 , 69 fixed-maturity investments with a total unrealized loss of $37 million had been in an unrealized loss position for 12 months or more. Of that total, five fixed-maturity investments had fair values below 70 percent of amortized cost. There were no equity security investments in an unrealized loss position for 12 months or more as of December 31, 2015 .

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements Fair Value Hierarchy The fair value hierarchy gives the highest priority to quoted prices with readily available independent data in active markets for identical assets or liabilities (Level 1) and the lowest priority to unobservable market inputs (Level 3). When various inputs for measurement fall within different levels of the fair value hierarchy, the lowest observable input that has a significant impact on fair value measurement is used. Our valuation techniques have not changed from those used at December 31, 2016 , and ultimately management determines fair value. Financial instruments reported at fair value in our consolidated financial statements are categorized based upon the following characteristics or inputs to the valuation techniques: • Level 1 – Financial assets and liabilities for which inputs are observable and are obtained from reliable quoted prices for identical assets or liabilities in active markets. This is the most reliable fair value measurement and includes, for example, active exchange-traded equity securities. • Level 2 – Financial assets and liabilities for which values are based on quoted prices in markets that are not active or for which values are based on similar assets and liabilities that are actively traded. This also includes pricing models for which the inputs are corroborated by market data. The technique used for the Level 2 fixed-maturity securities and taxable fixed maturities in separate accounts is the application of market based modeling. The inputs used for all classes of fixed-maturity securities listed in the table below include relevant market information by asset class, trade activity of like securities, marketplace quotes, benchmark yields, spreads off benchmark yields, interest rates, U.S. Treasury or swap curves, yield to maturity and economic events. Specific to commercial mortgage-backed securities, key inputs also include prepayment and default projections based on past performance of the underlying collateral and current market data. All of the Level 2 fixed-maturity securities are priced by a nationally recognized pricing vendor. The Level 2 nonredeemable preferred equities technique used is the application of market based modeling. The inputs used, similar to those used by the pricing vendor for our fixed-maturity securities, include relevant market information, trade activity of like securities, yield to maturity, corporate action notices and economic events. All of the Level 2 nonredeemable preferred equities are priced by a nationally recognized pricing vendor. • Level 3 – Financial assets and liabilities for which values are based on prices or valuation techniques that require inputs that are both unobservable and significant to the overall fair value measurement. Level 3 inputs include the following: ◦ Quotes from brokers or other external sources that are not considered binding; ◦ Quotes from brokers or other external sources where it cannot be determined that market participants would in fact transact for the asset or liability at the quoted price; or ◦ Quotes from brokers or other external sources where the inputs are not deemed observable. The following tables illustrate the fair value hierarchy for those assets measured at fair value on a recurring basis at December 31, 2017 and 2016 . We do not have any liabilities carried at fair value. There were no transfers between Level 1 and Level 2. (Dollars in millions) Quoted prices in active markets for Significant unobservable At December 31, 2017 Significant other observable inputs (Level 2) Total Fixed maturities, available for sale: Corporate $ — $ 5,652 $ 1 $ 5,653 States, municipalities and political subdivisions — 4,460 5 4,465 Commercial mortgage-backed — 286 — 286 Government-sponsored enterprises — 254 — 254 United States Government 31 — — 31 Foreign government — 10 — 10 Subtotal 31 10,662 6 10,699 Common equities, available for sale 6,039 — — 6,039 Nonredeemable preferred equities, available for sale — 210 — 210 Separate accounts taxable fixed maturities — 795 — 795 Top Hat savings plan mutual funds and common equity (included in Other assets) 31 — — 31 Total $ 6,101 $ 11,667 $ 6 $ 17,774 At December 31, 2016 Fixed maturities, available for sale: Corporate $ — $ 5,703 $ 78 $ 5,781 States, municipalities and political subdivisions — 3,828 — 3,828 Commercial mortgage-backed — 287 — 287 Government-sponsored enterprises — 164 — 164 United States Government 10 — — 10 Foreign government — 10 — 10 Convertibles and bonds with warrants attached — 5 — 5 Subtotal 10 9,997 78 10,085 Common equities, available for sale 5,123 — — 5,123 Nonredeemable preferred equities, available for sale — 211 — 211 Separate accounts taxable fixed maturities — 750 — 750 Top Hat savings plan mutual funds and common equity (included in Other assets) 24 — — 24 Total $ 5,157 $ 10,958 $ 78 $ 16,193 Each financial instrument that was deemed to have significant unobservable inputs when determining valuation is identified in the following tables by security type with a summary of changes in fair value for the years ended December 31, 2017 and 2016 . Total Level 3 assets continue to be less than 1 percent of financial assets measured at fair value in the consolidated balance sheets. Assets presented in the table below were valued based primarily on broker/dealer quotes for which there is a lack of transparency as to inputs used to develop the valuations. Transfers into Level 3 included situations where a fair value quote was not provided by the company's nationally recognized pricing vendor and as a result the price was stale or had been replaced with a broker quote where the inputs had not been corroborated to be market observable resulting in the security being classified as Level 3. Transfers out of Level 3 included situations where a broker quote was used without observable inputs or data that could not be corroborated by our pricing vendors in the prior period and significant observable inputs were identified in the current period. The following table provides the change in Level 3 assets during 2017 and 2016 : (Dollars in millions) Asset fair value measurements using significant unobservable input Corporate fixed maturities Separate accounts taxable fixed maturities States, municipalities and political subdivisions fixed maturities Nonredeemable preferred equities Total Beginning balance, January 1, 2017 $ 78 $ — $ — $ — $ 78 Total gains or losses (realized/unrealized): Included in net income — — — — — Included in other comprehensive income — — — — — Purchases — — 5 — 5 Sales — — — — — Transfers into Level 3 — — — — — Transfers out of Level 3 (77 ) — — — (77 ) Ending balance, December 31, 2017 $ 1 $ — $ 5 $ — $ 6 Beginning balance, January 1, 2016 $ 51 $ 1 $ — $ 3 $ 55 Total gains or losses (realized/unrealized): Included in net income — — — — — Included in other comprehensive income — — — (1 ) (1 ) Purchases 57 — — — 57 Sales (1 ) — — (2 ) (3 ) Transfers into Level 3 13 — — — 13 Transfers out of Level 3 (42 ) (1 ) — — (43 ) Ending balance, December 31, 2016 $ 78 $ — $ — $ — $ 78 With the exception of the above table, additional disclosures for the Level 3 category are not material, and therefore not provided. Fair Value Disclosure for Assets and Liabilities Not Carried at Fair Value The disclosures below are presented to provide information about the effects of current market conditions on financial instruments that are not reported at fair value in our consolidated financial statements. The following table shows fair values of our note payable and long-term debt: (Dollars in millions) Quoted prices in active markets for Significant other Significant unobservable inputs (Level 3) Total At December 31, 2017 Note payable $ — $ 24 $ — $ 24 6.900% senior debentures, due 2028 — 34 — 34 6.920% senior debentures, due 2028 — 505 — 505 6.125% senior notes, due 2034 — 477 — 477 Total $ — $ 1,040 $ — $ 1,040 At December 31, 2016 Note payable $ — $ 20 $ — $ 20 6.900% senior debentures, due 2028 — 33 — 33 6.920% senior debentures, due 2028 — 488 — 488 6.125% senior notes, due 2034 — 435 — 435 Total $ — $ 976 $ — $ 976 Fair value of the note payable was determined based upon the outstanding balance at December 31, 2017 and 2016 , because it is short term and tied to a variable interest rate. Fair value of the long-term debt was determined under the fair value measurements and disclosure accounting rules based on market pricing of similar debt instruments that are actively trading. We determine fair value for our debt the same way that we value corporate fixed maturities in our investment portfolio. Fair value can vary with macroeconomic conditions. Regardless of the fluctuations in fair value, the outstanding principal amount of our long-term debt is $793 million at both December 31, 2017 and 2016 . None of the long-term debt is encumbered by rating triggers. The note payable and long-term debt were classified as Level 2 as an active market does not exist, but fair value is determined based on observable inputs. The following table shows the fair value of our life policy loans, included in other invested assets: (Dollars in millions) Quoted prices in active markets for identical assets (Level 1) Significant other observable inputs (Level 2) Significant unobservable inputs (Level 3) Total At December 31, 2017 Life policy loans $ — $ — $ 41 $ 41 At December 31, 2016 Life policy loans $ — $ — $ 40 $ 40 Outstanding principal and interest for these life policy loans totaled $31 million at December 31, 2017 and 2016 . To determine the fair value, we make the following significant assumptions: (1) the discount rates used to calculate the present value of expected payments are the risk-free spot rates, as nonperformance risk is minimal; and (2) the loan repayment rate by which policyholders pay off their loan balances is in line with past experience. The following table shows fair value of our deferred annuities and structured settlements included in life policy and investment contract reserves: (Dollars in millions) Quoted prices in active markets for identical assets (Level 1) Significant other observable inputs (Level 2) Significant unobservable inputs (Level 3) Total At December 31, 2017 Deferred annuities $ — $ — $ 834 $ 834 Structured settlements — 210 — 210 Total $ — $ 210 $ 834 $ 1,044 At December 31, 2016 Deferred annuities $ — $ — $ 839 $ 839 Structured settlements — 206 — 206 Total $ — $ 206 $ 839 $ 1,045 Recorded reserves for the deferred annuities were $835 million and $861 million at December 31, 2017 and 2016 , respectively. Recorded reserves for the structured settlements were $161 million and $170 million at December 31, 2017 and 2016 , respectively. Fair values for deferred annuities were calculated based upon internally developed models because active markets and observable inputs do not exist. To determine the fair value, we made the following significant assumptions: (1) the discount rates used to calculate the present value of expected payments are the risk-free spot rates plus an A3 rated bond spread for financial issuers at December 31, 2017 and 2016 , to account for nonperformance risk; (2) the rate of interest credited to policyholders is the portfolio net earned interest rate less a spread for expenses and profit; and (3) additional lapses occur when the credited interest rate is exceeded by an assumed competitor credited rate, which is a function of the risk-free rate of the economic scenario being modeled. Fair values for structured settlements were calculated based on internally developed models which assume the discount rates used to calculate the present value of expected payments are the risk-free spot rates plus an A3 rated bond spread for financial issuers at December 31, 2017 and 2016 , to account for nonperformance risk. The structured settlements were classified as Level 2 as an active market does not exist, but fair value is based on observable inputs.

Property Casualty Loss And Loss

Property Casualty Loss And Loss Expenses	12 Months Ended
	Dec. 31, 2017
Insurance [Abstract]
Property Casualty Loss And Loss Expenses	Property Casualty Loss and Loss Expenses We use actuarial methods, models and judgment to estimate, as of a financial statement date, the property casualty loss and loss expense reserves required to pay for and settle all outstanding insured claims, including incurred but not reported (IBNR) claims, as of that date. The actuarial estimate is subject to review and adjustment by an inter-departmental committee that includes actuarial, claims, underwriting, loss prevention and accounting management. This committee is familiar with relevant company and industry business, claims and underwriting trends, as well as general economic and legal trends that could affect future loss and loss expense payments. The amount we will actually have to pay for claims can be highly uncertain. This uncertainty, together with the size of our reserves, makes the loss and loss expense reserves our most significant estimate. Our reserving process takes into account known facts and interpretations of circumstances and factors including the type of claim, policy provisions pertaining to each claim, potential subrogation or salvage recoverable, large loss activity and trends, new business activity, judicial decisions, economic conditions, changes in law and regulation and product and underwriting changes. There have been no significant changes in methodologies and assumptions used in calculating loss and loss expense reserves for all years presented. There were no material additional premiums or return premiums accrued for as a result of prior-year effects. Our field claims representatives establish case reserves when claims are reported to provide for our unpaid loss and loss expense obligation associated with individual claims. For events designated as natural catastrophes resulting in losses incurred related to direct premiums, we calculate IBNR reserves directly as a result of an estimated claim counts and estimated average dollar amount per claim for each event. Once individual case reserves are established for a catastrophe event, we reduce the IBNR reserves. Our actuarial staff uses generally accepted actuarial methods and models to derive ultimate loss and IBNR reserve estimates. The time interval between a claims occurrence and its settlement is one of the crucial attributes when estimating ultimate losses and IBNR reserves. Due to the uncertainties inherent with loss reserves, our ultimate loss experience could prove better or worse than what our carried reserves reflect. To the extent that reserves are inadequate and are required to be increased, the amount of the increase is a charge in that period, raising our loss and loss expense ratio and reducing earnings. To the extent that reserves are redundant and are required to be released, the amount of the release is a credit in that period, reducing our loss and loss expense ratio and increasing earnings. This table summarizes activity for our consolidated property casualty loss and loss expense reserves: (Dollars in millions) Years ended December 31, 2017 2016 2015 Gross loss and loss expense reserves, January 1 $ 5,035 $ 4,660 $ 4,438 Less reinsurance recoverable 298 281 282 Net loss and loss expense reserves, January 1 4,737 4,379 4,156 Net incurred loss and loss expenses related to: Current accident year 3,257 3,029 2,756 Prior accident years (119 ) (168 ) (184 ) Total incurred 3,138 2,861 2,572 Net paid loss and loss expenses related to: Current accident year 1,404 1,260 1,152 Prior accident years 1,439 1,243 1,197 Total paid 2,843 2,503 2,349 Net loss and loss expense reserves, December 31 5,032 4,737 4,379 Plus reinsurance recoverable 187 298 281 Gross loss and loss expense reserves, December 31 $ 5,219 $ 5,035 $ 4,660 In 2017, 2016 and 2015, the reserve for loss and loss expense in the consolidated balance sheets also included $54 million , $50 million and $58 million , respectively, for certain life and health loss and loss expense reserves. Additional disclosures for reserves related to these health claims are not material and therefore not provided. During 2017, we experienced $119 million of favorable development on prior accident years including $73 million of favorable development in commercial lines, $14 million of favorable development in personal lines, $29 million of favorable development in excess and surplus lines and $3 million of favorable development in our reinsurance assumed operations. We recognized favorable development of $54 million for the workers' compensation line, $33 million for the commercial property line and $30 million for the other commercial lines due to reduced uncertainty of prior accident year loss and loss expense for these lines. This illustrates the potential for revisions inherent in estimating reserves, especially for long-tail lines such as workers’ compensation. We recognized unfavorable reserve development of $33 million for the commercial auto line due to higher loss cost effects in recent accident years, resulting in an increase of our reserve estimate for claims that have not yet been settled. Commercial casualty developed unfavorably by $11 million due to paid losses or re-estimates of case reserves at higher than expected levels. During 2016 , we experienced $168 million of favorable development on prior accident years including $129 million of favorable development in commercial lines, $4 million of favorable development in personal lines, $34 million of favorable development in excess and surplus lines and $1 million of favorable development in our reinsurance assumed operations. We recognized favorable development of $69 million for the workers' compensation line, $29 million for the commercial property line, $20 million for commercial casualty line and $42 million for the other commercial lines due to reduced uncertainty of prior accident year loss and loss expense for these lines. We recognized unfavorable reserve development of $31 million for the commercial auto line and $18 million for the personal auto line. Both lines developed unfavorable due to higher loss cost effects in recent accident years, resulting in an increase of our reserve estimate for claims that have not yet been settled. During 2015 , we experienced $184 million of favorable development on prior accident years including $154 million of favorable development in commercial lines, $5 million of adverse development in personal lines and $35 million of favorable development in excess and surplus lines. We recognized favorable development of $93 million for the workers’ compensation line, largely due to more favorable 2015 workers' compensation trends for estimated payments to be made in future calendar years that were down slightly from 2014. We recognized favorable development of $63 million for the commercial casualty line. Development for products liability was favorable for most prior accident years and development of prior years for commercial umbrella coverage improved slightly better than expected. Therefore, estimated ultimate losses were lowered. Our commercial auto line experienced $31 million of adverse development due to higher loss cost effects in recent accident years, resulting in an increase of our reserve estimate for claims that have not yet been settled. Included in our lines of business are asbestos and environmental claims. We carried $84 million and $85 million of net loss and loss expense reserves for asbestos and environmental claims at December 31, 2017 and 2016, respectively. The asbestos and environmental claims amounts for each respective year constituted less than 2.0 percent of total net loss and loss expense reserves at these year-end dates. We believe our exposure to asbestos and environmental claims is limited, largely because our reinsurance retention was $500,000 or below prior to 1987. We also were predominantly a personal lines company in the 1960s and 1970s. During the 1980s and early 1990s, commercial lines grew as a percentage of our overall business and our exposure to asbestos and environmental claims grew accordingly. Over that period, we included an asbestos and environmental exclusion in almost all policies or endorsed the exclusion to the policies. We have not engaged in any mergers or acquisitions through which such a liability could have been assumed. We continue to monitor our claims for evidence of material exposure to other mass tort classes but have found no such credible evidence to date. The following table provides a reconciliation of the property casualty incurred losses and allocated loss adjustment expenses (ALAE) development and paid losses and ALAE development information at December 31, 2017. (Dollars in millions) Cumulative incurred losses and ALAE as reported within the triangles, net of reinsurance Cumulative paid losses and ALAE as reported within the triangles, net of reinsurance Liabilities for loss and ALAE for accident years not presented in the triangles, net of reinsurance Total liabilities for loss and ALAE, net of reinsurance Reinsurance recoverable on unpaid losses Total liabilities for gross loss and loss expense reserves Commercial casualty $ 4,434 $ 2,573 $ 83 $ 1,944 $ 43 $ 1,987 Workers' compensation 2,259 1,598 267 928 64 992 Commercial auto 1,955 1,380 16 591 4 595 Commercial property 2,353 2,095 12 270 7 277 Personal auto 1,774 1,503 5 276 31 307 Homeowner 1,466 1,358 3 111 3 114 Excess and surplus 441 195 94 340 3 343 Other lines 315 Total liabilities for loss and ALAE reserves 4,930 Unallocated loss adjustment expense reserves 289 Gross loss and loss expense reserves $ 5,219 For all lines of business, the claim counts reported are primarily measured by insurance coverages that are triggered when a loss occurs and a reserve is established. For this purpose, coverages are defined as unique combinations of certain attributes such as line of business and cause of loss. Claims that are opened and closed without payment are included in the reported claim counts. Claim counts are presented on a direct basis only and do not reflect any assumed or ceded reinsurance. In the following tables, commercial casualty and workers' compensation each disclose 10 accident years of loss and ALAE reserves and nine accident years of the cumulative number of reported claims. In 2009, we refined our claim count logic such that the definition of an open claim, a closed claim and a claim that closes without payment was uniform amongst all of our systems, including legacy systems. Therefore, consistent definitions are only available for accident year 2009 and forward. We will increase the commercial casualty and workers’ compensation cumulative number of reported claims by one year in future periods, not to exceed 10 years . Commercial auto, commercial property, personal auto and homeowner each disclose five accident years of loss and ALAE reserves and cumulative number of reported claims as each of these lines have five year cumulative average annual percentage payouts of approximately 95 percent or higher. The excess and surplus lines began operations in 2008 with earned premiums and loss and ALAE reserves being immaterial prior to 2011. Accordingly, we disclosed seven accident years of loss and ALAE reserves and cumulative number of reported claims for the excess and surplus lines, and will disclose additional accident years in subsequent annual filings, not to exceed 10 years. Commercial Casualty The following table shows the commercial casualty incurred and paid losses and ALAE development by accident year. The table also shows the IBNR reserves plus expected development on reported losses and claim frequency: (Dollars in millions, reported claims in thousands) As of December 31, 2017 Incurred losses and ALAE, net of reinsurance Total of incurred but not reported liabilities plus expected development on reported losses Cumulative number of reported claims Years ended December 31, Accident 2008 2009 2010 2011 2012 2013 2014 2015 2016 Year Unaudited 2017 2008 $ 516 $ 458 $ 409 $ 387 $ 362 $ 359 $ 357 $ 357 $ 355 $ 366 $ 11 — 2009 484 409 412 360 370 365 357 357 353 10 20 2010 495 394 378 349 347 348 349 343 19 20 2011 466 404 377 377 375 380 366 17 19 2012 466 414 417 394 394 404 43 18 2013 448 443 431 416 413 64 19 2014 503 496 479 476 82 21 2015 533 526 529 170 20 2016 563 574 247 19 2017 610 381 15 Total $ 4,434 Cumulative paid losses and ALAE, net of reinsurance 2008 $ 31 $ 93 $ 158 $ 212 $ 262 $ 293 $ 315 $ 325 $ 331 $ 339 2009 27 75 151 213 267 295 310 322 328 2010 33 92 159 203 256 285 300 314 2011 27 93 149 227 266 298 315 2012 27 88 170 232 288 330 2013 35 90 159 232 286 2014 34 97 172 287 2015 38 108 200 2016 46 126 2017 48 Total 2,573 All outstanding liabilities before 2008, net of reinsurance 83 Liabilities for loss and ALAE, net of reinsurance $ 1,944 The following table shows the average annual percentage payout of incurred losses for the commercial casualty line of business: Average annual percentage payout of incurred losses by age, net of reinsurance (unaudited) Years 1 2 3 4 5 6 7 8 9 10 Average annual percentage payout 7.9% 14.9% 18.0% 17.7% 13.7% 8.8% 4.8% 3.5% 1.6% 1.8% Workers’ Compensation The following table shows the workers’ compensation incurred and paid losses and ALAE development by accident year. The table also shows the IBNR reserves plus expected development on reported losses and claim frequency: (Dollars in millions, reported claims in thousands) As of December 31, 2017 Incurred losses and ALAE, net of reinsurance Total of incurred Cumulative number of reported claims Years ended December 31, Accident 2008 2009 2010 2011 2012 2013 2014 2015 2016 Year Unaudited 2017 2008 $ 298 $ 305 $ 310 $ 302 $ 299 $ 299 $ 297 $ 296 $ 296 $ 293 $ 28 — 2009 307 278 263 238 238 235 234 234 232 18 27 2010 283 274 248 242 240 239 240 237 22 26 2011 284 251 246 242 239 236 231 22 24 2012 265 245 234 220 213 211 26 21 2013 264 246 221 212 208 28 20 2014 261 233 214 203 31 19 2015 246 220 208 60 17 2016 230 218 72 16 2017 218 89 13 Total $ 2,259 Cumulative paid losses and ALAE, net of reinsurance 2008 $ 72 $ 155 $ 195 $ 217 $ 233 $ 242 $ 247 $ 251 $ 254 $ 256 2009 65 132 163 179 188 193 198 201 202 2010 67 134 164 181 192 198 202 204 2011 65 131 161 177 186 190 192 2012 62 121 147 162 171 175 2013 61 119 144 157 164 2014 56 110 134 148 2015 47 93 115 2016 46 97 2017 45 Total 1,598 All outstanding liabilities before 2008, net of reinsurance 267 Liabilities for loss and ALAE, net of reinsurance $ 928 The following table shows the average annual percentage payout of incurred losses for the workers’ compensation line of business: Average annual percentage payout of incurred losses by age, net of reinsurance (unaudited) Years 1 2 3 4 5 6 7 8 9 10 Average annual percentage payout 25.9% 26.9% 12.4% 7.0% 4.2% 2.4% 1.5% 1.4% 0.8% 0.5% Commercial Auto The following table shows the commercial auto incurred and paid losses and ALAE development by accident year. The table also shows the IBNR reserves plus expected development on reported losses and claim frequency: (Dollars in millions, reported claims in thousands) As of December 31, 2017 Incurred losses and ALAE, net of reinsurance Total of incurred Cumulative number of reported claims Years ended December 31, Accident 2013 2014 2015 2016 Year Unaudited 2017 2013 $ 292 $ 305 $ 315 $ 322 $ 322 $ 5 46 2014 333 346 351 358 8 51 2015 374 384 394 15 51 2016 417 430 36 53 2017 451 127 47 Total $ 1,955 Cumulative paid losses and ALAE, net of reinsurance 2013 $ 141 $ 199 $ 246 $ 285 $ 307 2014 159 223 273 310 2015 173 244 303 2016 184 273 2017 187 Total 1,380 All outstanding liabilities before 2013, net of reinsurance 16 Liabilities for loss and ALAE, net of reinsurance $ 591 The following table shows the average annual percentage payout of incurred losses for the commercial auto line of business. Commercial auto includes both physical damage and liability losses. A majority of the incurred losses paid after year 2 are the result of liability losses. Average annual percentage payout of incurred losses by age, net of reinsurance (unaudited) Years 1 2 3 4 5 Average annual percentage payout 43.3% 18.7% 14.5% 11.2% 6.7% Commercial Property The following table shows the commercial property incurred and paid losses and ALAE development by accident year. The table also shows the IBNR reserves plus expected development on reported losses and claim frequency: (Dollars in millions, reported claims in thousands) As of December 31, 2017 Incurred losses and ALAE, net of reinsurance Total of incurred Cumulative number of reported claims Years ended December 31, Accident 2013 2014 2015 2016 Year Unaudited 2017 2013 $ 389 $ 359 $ 352 $ 356 $ 357 $ 1 14 2014 452 444 441 442 2 17 2015 454 414 416 2 17 2016 590 551 7 17 2017 587 24 16 Total $ 2,353 Cumulative paid losses and ALAE, net of reinsurance 2013 $ 227 $ 330 $ 344 $ 349 $ 352 2014 297 412 432 437 2015 279 388 407 2016 358 504 2017 395 Total 2,095 All outstanding liabilities before 2013, net of reinsurance 12 Liabilities for loss and ALAE, net of reinsurance $ 270 The following table shows the average annual percentage payout of incurred losses for the commercial property line of business: Average annual percentage payout of incurred losses by age, net of reinsurance (unaudited) Years 1 2 3 4 5 Average annual percentage payout 66.0% 26.9% 4.4% 1.1% 0.9% Personal Auto The following table shows the personal auto incurred and paid losses and ALAE development by accident year. The table also shows the IBNR reserves plus expected development on reported losses and claim frequency: (Dollars in millions, reported claims in thousands) As of December 31, 2017 Incurred losses and ALAE, net of reinsurance Total of incurred Cumulative number of reported claims Years ended December 31, Accident 2013 2014 2015 2016 Year Unaudited 2017 2013 $ 280 $ 280 $ 293 $ 298 $ 298 $ — 96 2014 317 317 325 324 — 105 2015 343 356 356 — 108 2016 383 384 8 110 2017 412 55 102 Total $ 1,774 Cumulative paid losses and ALAE, net of reinsurance 2013 $ 190 $ 245 $ 272 $ 287 $ 293 2014 210 267 298 313 2015 229 292 325 2016 243 316 2017 256 Total 1,503 All outstanding liabilities before 2013 net of reinsurance 5 Liabilities for loss and ALAE, net of reinsurance $ 276 The following table shows the average annual percentage payout of incurred losses for the personal auto line of business. Personal auto includes both physical damage and liability losses. A majority of the incurred losses paid after year 2 are the result of liability losses. Average annual percentage payout of incurred losses by age, net of reinsurance (unaudited) Years 1 2 3 4 5 Average annual percentage payout 63.7% 18.1% 9.4% 4.8% 1.9% Homeowner The following table shows the homeowner incurred and paid losses and ALAE development by accident year. The table also shows the IBNR reserves plus expected development on reported losses and claim frequency: (Dollars in millions, reported claims in thousands) As of December 31, 2017 Incurred losses and ALAE, net of reinsurance Total of incurred Cumulative number of reported claims Years ended December 31, Accident 2013 2014 2015 2016 Year Unaudited 2017 2013 $ 252 $ 246 $ 247 $ 247 $ 246 $ — 25 2014 297 283 286 285 1 26 2015 284 275 275 1 24 2016 315 304 3 23 2017 356 8 24 Total $ 1,466 Cumulative paid losses and ALAE, net of reinsurance 2013 $ 180 $ 236 $ 242 $ 244 $ 246 2014 224 273 281 283 2015 203 260 269 2016 208 283 2017 277 Total 1,358 All outstanding liabilities before 2013, net of reinsurance 3 Liabilities for loss and ALAE, net of reinsurance $ 111 The following table shows the average annual percentage payout of incurred losses for the homeowner line of business: Average annual percentage payout of incurred losses by age, net of reinsurance (unaudited) Years 1 2 3 4 5 Average annual percentage payout 74.4% 21.3% 3.0% 0.7% 0.4% Excess and Surplus Lines The following table shows the excess and surplus lines incurred and paid losses and ALAE development by accident year. The table also shows the IBNR reserves plus expected development on reported losses and claim frequency: (Dollars in millions, reported claims in thousands) As of December 31, 2017 Incurred losses and ALAE, net of reinsurance Total of incurred Cumulative number of reported claims Years ended December 31, Accident 2011 2012 2013 2014 2015 2016 Year Unaudited 2017 2011 $ 48 $ 47 $ 44 $ 38 $ 36 $ 35 $ 35 $ 1 1 2012 67 56 49 40 37 36 1 1 2013 74 64 54 45 42 4 2 2014 95 82 75 64 16 2 2015 96 81 73 22 2 2016 93 87 34 2 2017 104 64 2 Total $ 441 Cumulative paid losses and ALAE, net of reinsurance 2011 $ 8 $ 14 $ 23 $ 27 $ 30 $ 32 $ 34 2012 9 15 19 25 29 31 2013 7 12 20 27 32 2014 9 17 27 37 2015 8 19 29 2016 10 21 2017 11 Total 195 All outstanding liabilities before 2011, net of reinsurance 94 Liabilities for loss and ALAE, net of reinsurance $ 340 The following table shows the average annual percentage payout of incurred losses for the excess and surplus lines insurance segment. Excess and surplus lines consist mostly of commercial casualty and commercial property coverages. A majority of the incurred losses paid after year 2 are the result of commercial casualty losses. Average annual percentage payout of incurred losses by age, net of reinsurance (unaudited) Years 1 2 3 4 5 6 7 Average annual percentage payout 16.0% 14.1% 17.5% 14.7% 10.7% 7.2% 1.1%

Life Policy And Investment Cont

Life Policy And Investment Contract Reserves	12 Months Ended
	Dec. 31, 2017
Liability for Future Policy Benefits [Abstract]
Life Policy And Investment Contract Reserves	Life Policy and Investment Contract Reserves We establish the reserves for traditional life insurance policies based on expected expenses, mortality, morbidity, withdrawal rates, timing of claim presentation and investment yields, including a provision for uncertainty. Once these assumptions are established, they generally are maintained throughout the lives of the contracts. We use both our own experience and industry experience, adjusted for historical trends, in arriving at our assumptions for expected mortality, morbidity and withdrawal rates as well as for expected expenses. We base our assumptions for expected investment income on our own experience adjusted for current economic conditions. We establish reserves for the company’s universal life, deferred annuity and structured settlement policies equal to the cumulative account balances, which include premium deposits plus credited interest less charges and withdrawals. Some of our universal life policies contain no-lapse guarantee provisions. For these policies, we establish a reserve in addition to the account balance, based on expected no-lapse guarantee benefits and expected policy assessments. This table summarizes our life policy and investment contract reserves: (Dollars in millions) At December 31, 2017 2016 Life policy reserves: Ordinary/traditional life $ 1,080 $ 1,011 Other 47 45 Subtotal 1,127 1,056 Investment contract reserves: Deferred annuities 835 861 Universal life 601 578 Structured settlements 160 170 Other 6 6 Subtotal 1,602 1,615 Total life policy and investment contract reserves $ 2,729 $ 2,671

Deferred Policy Acquisition Cos

Deferred Policy Acquisition Costs	12 Months Ended
	Dec. 31, 2017
Deferred Costs [Abstract]
Deferred Policy Acquisition Costs	Deferred Policy Acquisition Costs Expenses directly related to successfully acquired insurance policies – primarily commissions, premium taxes and underwriting costs – are deferred and amortized over the terms of the policies. We update our acquisition cost assumptions periodically to reflect actual experience, and we evaluate the costs for recoverability. The table below shows the deferred policy acquisition costs and asset reconciliation: (Dollars in millions) Years ended December 31, 2017 2016 2015 Property casualty: Deferred policy acquisition costs asset, January 1 $ 408 $ 388 $ 379 Capitalized deferred policy acquisition costs 897 840 801 Amortized deferred policy acquisition costs (867 ) (820 ) (792 ) Deferred policy acquisition costs asset, December 31 $ 438 $ 408 $ 388 Life: Deferred policy acquisition costs asset, January 1 $ 229 $ 228 $ 199 Capitalized deferred policy acquisition costs 51 49 45 Amortized deferred policy acquisition costs (46 ) (43 ) (37 ) Amortized shadow deferred policy acquisition costs (2 ) (5 ) 21 Deferred policy acquisition costs asset, December 31 $ 232 $ 229 $ 228 Consolidated: Deferred policy acquisition costs asset, January 1 $ 637 $ 616 $ 578 Capitalized deferred policy acquisition costs 948 889 846 Amortized deferred policy acquisition costs (913 ) (863 ) (829 ) Amortized shadow deferred policy acquisition costs (2 ) (5 ) 21 Deferred policy acquisition costs asset, December 31 $ 670 $ 637 $ 616 No premium deficiencies were recorded in the consolidated statements of income in 2017 , 2016 and 2015 , as the sum of the anticipated loss and loss expenses, policyholder dividends and unamortized deferred acquisition expenses did not exceed the related unearned premiums and anticipated investment income.

Note Payable

Note Payable	12 Months Ended
	Dec. 31, 2017
Notes Payable, Current [Abstract]
Note Payable	Note Payable We have one line of credit through multiple commercial banks with a borrowing capacity of $225 million and an additional $50 million accordion feature. Our unsecured revolving credit facility has a term of five years that expires May 13, 2019 . We had no compensating balance requirements on short-term debt for either 2017 or 2016 . At December 31, 2017 and 2016, $24 million and $20 million was drawn on the line of credit, respectively. The interest rate charged on our borrowings on this credit agreement ranged from 1.65 percent to 2.45 percent during 2017 and ranged from 1.31 percent to 1.49 percent during 2016 .

Long-Term Debt And Capital Leas

Long-Term Debt And Capital Lease Obligation	12 Months Ended
	Dec. 31, 2017
Long-term Debt and Capital Lease Obligations [Abstract]
Long-Term Debt And Capital Lease Obligation	Long-Term Debt and Capital Lease Obligations This table summarizes the principal amounts of our long-term debt excluding unamortized discounts, none of which are encumbered by rating triggers: (Dollars in millions) Book value Principal amount Interest rate Year of issue At December 31, At December 31, 2017 2016 2017 2016 6.900% 1998 Senior debentures, due 2028 $ 26 $ 26 $ 28 $ 28 6.920% 2005 Senior debentures, due 2028 391 391 391 391 6.125% 2004 Senior notes, due 2034 370 370 374 374 Total $ 787 $ 787 $ 793 $ 793 Capital lease obligations, excluding an insignificant amount of interest, totaled $40 million and $39 million in 2017 and 2016 , respectively. Below are the expected capital lease obligations that we expect to pay over the next six years: (Dollars in millions) Years ended December 31, 2018 2019 2020 2021 2022 2023 Capital lease obligations $ 12 $ 10 $ 7 $ 5 $ 4 $ 2

Shareholders' Equity And Divide

Shareholders' Equity And Dividend Restrictions	12 Months Ended
	Dec. 31, 2017
Shareholders Equity And Dividend Restrictions [Abstract]
Shareholders' Equity And Dividend Restrictions	Shareholders’ Equity and Dividend Restrictions Declared cash dividends per share were $2.50 , $1.92 and $2.30 for the years ended December 31, 2017 , 2016 and 2015 , respectively. Our insurance subsidiary declared dividends to the parent company of $465 million in 2017 , $475 million in 2016 and $447 million in 2015 . State regulatory requirements restrict the dividends insurance subsidiaries can pay. Generally, the most our insurance subsidiary can pay without prior regulatory approval is the greater of 10 percent of statutory capital and surplus or 100 percent of statutory net income for the prior calendar year. Dividends exceeding these limitations may be paid only with approval of the insurance department of the domiciliary state. During 2018 , the total that our insurance subsidiary, which is the parent of all other insurance subsidiaries, may declare in dividends is approximately $509 million . Accumulated Other Comprehensive Income The table below shows beginning and end of year accumulated other comprehensive income (AOCI) for investments, pension obligations, life deferred acquisition costs, life policy reserves and other. The changes from the beginning of year to the end of year are the result of changes to other comprehensive income or loss (OCI). Additionally, as a result of the early adoption of ASU 2018-02, Income Statement—Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income, included in the table below is the reclassification of $492 million which increased AOCI and decreased retained earnings. See Note 1, Summary of Significant Accounting Policies for further explanation of this ASU. (Dollars in millions) 2017 2016 2015 Before tax Income tax Net Before Income Net Before Income Net Investments: AOCI, January 1 $ 2,625 $ 908 $ 1,717 $ 2,094 $ 722 $ 1,372 $ 2,719 $ 942 $ 1,777 OCI before realized gains recognized in net income 1,054 366 688 653 229 424 (556 ) (196 ) (360 ) Realized gains recognized in net income (139 ) (49 ) (90 ) (122 ) (43 ) (79 ) (69 ) (24 ) (45 ) OCI 915 317 598 531 186 345 (625 ) (220 ) (405 ) Adjustment to reclassify certain tax effects from AOCI — (492 ) 492 — — — — — — AOCI, December 31 $ 3,540 $ 733 $ 2,807 $ 2,625 $ 908 $ 1,717 $ 2,094 $ 722 $ 1,372 Pension obligations: AOCI, January 1 $ (26 ) $ (8 ) $ (18 ) $ (42 ) $ (14 ) $ (28 ) $ (36 ) $ (12 ) $ (24 ) OCI excluding amortization recognized in net income 12 6 6 13 5 8 (12 ) (5 ) (7 ) Amortization recognized in net income 2 1 1 3 1 2 6 3 3 OCI 14 7 7 16 6 10 (6 ) (2 ) (4 ) AOCI, December 31 $ (12 ) $ (1 ) $ (11 ) $ (26 ) $ (8 ) $ (18 ) $ (42 ) $ (14 ) $ (28 ) Life deferred acquisition costs, life policy reserves and other: AOCI, January 1 $ (9 ) $ (3 ) $ (6 ) $ 1 $ 1 $ — $ (12 ) $ (3 ) $ (9 ) OCI before realized gains recognized in net income 8 5 3 (8 ) (3 ) (5 ) 14 5 9 Realized gains recognized in net income (9 ) (4 ) (5 ) (2 ) (1 ) (1 ) (1 ) (1 ) — OCI (1 ) 1 (2 ) (10 ) (4 ) (6 ) 13 4 9 AOCI, December 31 $ (10 ) $ (2 ) $ (8 ) $ (9 ) $ (3 ) $ (6 ) $ 1 $ 1 $ — Summary of AOCI: AOCI, January 1 $ 2,590 $ 897 $ 1,693 $ 2,053 $ 709 $ 1,344 $ 2,671 $ 927 $ 1,744 Investments OCI 915 317 598 531 186 345 (625 ) (220 ) (405 ) Pension obligations OCI 14 7 7 16 6 10 (6 ) (2 ) (4 ) Life deferred acquisition costs, life policy reserves and other OCI (1 ) 1 (2 ) (10 ) (4 ) (6 ) 13 4 9 Total OCI 928 325 603 537 188 349 (618 ) (218 ) (400 ) Adjustment to reclassify certain tax effects from AOCI — (492 ) 492 — — — — — — AOCI, December 31 $ 3,518 $ 730 $ 2,788 $ 2,590 $ 897 $ 1,693 $ 2,053 $ 709 $ 1,344 Investments realized gains and life deferred acquisition costs, life policy reserves and other realized gains are recorded in the realized investment gains, net, line item in the consolidated statements of income. Amortization on pension obligations is recorded in the insurance losses and contract holders' benefits and underwriting, acquisition and insurance expenses line items in the consolidated statements of income.

Reinsurance

Reinsurance	12 Months Ended
	Dec. 31, 2017
Reinsurance Disclosures [Abstract]
Reinsurance	Reinsurance Primary components of our property casualty reinsurance assumed operations include involuntary and voluntary assumed as well as contracts from our reinsurance assumed operations, known as Cincinnati Re. Primary components of our ceded reinsurance include a property per risk treaty, property excess treaty, casualty per occurrence treaty, casualty excess treaty, property catastrophe treaty and catastrophe bonds and retrocessions on our reinsurance assumed operations. Management’s decisions about the appropriate level of risk retention are affected by various factors, including changes in our underwriting practices, capacity to retain risks and reinsurance market conditions. The tables below summarize our consolidated property casualty insurance net written premiums, earned premiums and incurred loss and loss expenses: (Dollars in millions) Years ended December 31, 2017 2016 2015 Direct written premiums $ 4,854 $ 4,646 $ 4,461 Assumed written premiums 125 103 77 Ceded written premiums (139 ) (169 ) (177 ) Net written premiums $ 4,840 $ 4,580 $ 4,361 (Dollars in millions) Years ended December 31, 2017 2016 2015 Direct earned premiums $ 4,752 $ 4,567 $ 4,396 Assumed earned premiums 132 77 29 Ceded earned premiums (162 ) (162 ) (154 ) Earned premiums $ 4,722 $ 4,482 $ 4,271 (Dollars in millions) Years ended December 31, 2017 2016 2015 Direct incurred loss and loss expenses $ 2,961 $ 2,874 $ 2,596 Assumed incurred loss and loss expenses 113 43 12 Ceded incurred loss and loss expenses 64 (56 ) (36 ) Incurred loss and loss expenses $ 3,138 $ 2,861 $ 2,572 Our changes in direct incurred and ceded incurred compared to prior years resulted primarily from a large settlement paid by USAIG, a joint underwriting association of individual insurance companies that collectively functions as a worldwide aviation insurance market. This settlement resulted in offsetting amounts to direct incurred and ceded incurred with no change to our net incurred loss and loss expenses. We terminated our participation in the USAIG pool after policy year 2002. Our life insurance company purchases reinsurance for protection of a portion of risks that are written. Primary components of our life reinsurance program include individual mortality coverage, aggregate catastrophe and accidental death coverage in excess of certain deductibles. The tables below summarize our consolidated life insurance earned premiums and contract holders' benefits incurred: (Dollars in millions) Years ended December 31, 2017 2016 2015 Direct earned premiums $ 300 $ 290 $ 271 Ceded earned premiums (68 ) (62 ) (62 ) Earned premiums $ 232 $ 228 $ 209 (Dollars in millions) Years ended December 31, 2017 2016 2015 Direct contract holders' benefits incurred $ 319 $ 303 $ 292 Ceded contract holders' benefits incurred (67 ) (57 ) (56 ) Contract holders' benefits incurred $ 252 $ 246 $ 236 The ceded benefits incurred can vary depending on the type of life insurance policy held and the year the policy was issued.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The significant components of deferred tax assets and liabilities included in the consolidated balance sheets at December 31 were as follows: (Dollars in millions) At December 31, 2017 2016 Deferred tax assets: Loss and loss expense reserves $ 123 $ 199 Unearned premiums 100 158 Investments — 5 Other 27 52 Total gross deferred tax assets 250 414 Deferred tax liabilities: Unrealized investment gains and other, net 740 907 Deferred acquisition costs 123 195 Life policy reserves 111 162 Investments 10 — Other 11 15 Total gross deferred tax liabilities 995 1,279 Net deferred income tax liability $ 745 $ 865 Deferred tax assets and liabilities reflect temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amount recognized for tax purposes. Deferred tax assets are reduced by a valuation allowance when management believes it is more likely than not that some, or all, of the deferred tax assets will not be realized. After considering all positive and negative evidence of taxable income in the carryback and carryforward periods as permitted by law, we believe it is more likely than not that all of the deferred tax asset will be realized. As a result, we have no valuation allowance as of December 31, 2017 and 2016. The differences between the 35 percent statutory federal income tax rate and our effective income tax rate were as follows: (Dollars in millions) Years ended December 31, 2017 2016 2015 Tax at statutory rate: $ 256 35.0 % $ 284 35.0 % $ 308 35.0 % Increase (decrease) resulting from: Tax-exempt income from municipal bonds (36 ) (4.9 ) (34 ) (4.2 ) (33 ) (3.7 ) Dividend received exclusion (34 ) (4.7 ) (33 ) (4.1 ) (32 ) (3.6 ) Deferred tax benefit due to tax rate change (495 ) (67.8 ) — — — — Other (6 ) (0.8 ) 4 0.5 4 0.3 Provision for income taxes $ (315 ) (43.2 )% $ 221 27.2 % $ 247 28.0 % The Tax Act was enacted on December 22, 2017, and represented one of the most comprehensive changes in U.S. corporate income taxation since 1986. The Tax Act revises the U.S. corporate income tax by lowering the corporate income tax rate from a top marginal rate of 35 percent to a flat rate of 21 percent . In addition to lowering tax rates, changes were made to the amount of the dividends received deduction and the required proration addback for qualified dividend income and tax exempt municipal interest. The Tax Act is effective January 1, 2018. The reduction in corporate income tax rate decreased our net deferred tax liability as of December 22, 2017, by $495 million . The effect of the rate change was recorded as a one-time noncash benefit to income tax expense in our consolidated statements of income for the year ended December 31, 2017, with an effective tax rate benefit of 67.8 percent . This benefit results from re-measuring our net deferred tax liability at the newly enacted corporate income tax rate of 21 percent (the rate at which the deferred items are expected to be reversed) versus the 35 percent rate at which the net deferred tax benefits were previously carried. Of this $495 million benefit, $492 million relates to net unrealized gains on investments and other AOCI amounts. The remainder relates to differences in the recognition of deferred acquisition costs, unearned premiums, insurance reserves and basis differences in the carrying value of investments held. We expect to complete determination of the effects of the Tax Act on our deferred tax assets and liabilities as part of the annual income tax return filing process which is expected to be completed in the fourth quarter of 2018. The provision for federal income taxes is based upon filing a consolidated income tax return for the company and its subsidiaries. Included in Other above is the current year tax benefit under ASU 2016-09, Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting , which decreased both the provision for income taxes and the effective income tax rate by $7 million and 1 percent , respectively. As of December 31, 2017 , 2016 and 2015 , we had no operating or capital loss carryforwards. Unrecognized Tax Benefits As a result of positions either taken in our 2014 through 2016 federal tax returns filed with the IRS or expected to be taken in the 2017 filing, we believe it is more likely than not that our tax liability will be sustained upon examination by the IRS. We therefore carry no amount for unrecognized tax benefits for the years ended 2014 through 2017 . The statute of limitations for federal tax purposes has closed for tax years 2013 and earlier. There are no federal returns under examination and we have not been notified of any upcoming IRS examinations. Income taxes paid in our consolidated statements of cash flows are shown net of refunds received of $18 million in 2017, $2 million in 2016 and an immaterial amount in 2015. In addition to our IRS filings, we file income tax returns with immaterial amounts in various state jurisdictions. The statute of limitations for state income tax purposes has closed for tax years 2013 and earlier. There are no state income returns under examination and we have not been notified of any upcoming state examinations.

Net Income Per Common Share

Net Income Per Common Share	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Net Income Per Common Share	Net Income Per Common Share Basic earnings per share are computed based on the weighted average number of common shares outstanding. Diluted earnings per share are computed based on the weighted average number of common and dilutive potential common shares outstanding using the treasury stock method. The table shows calculations for basic and diluted earnings per share: (In millions, except per share data) Years ended December 31, 2017 2016 2015 Numerator: Net income—basic and diluted $ 1,045 $ 591 $ 634 Denominator: Basic weighted-average common shares outstanding 164.2 164.5 164.0 Effect of share-based awards: Stock options 1.1 1.1 1.0 Nonvested shares 0.7 0.9 0.6 Diluted weighted-average shares 166.0 166.5 165.6 Earnings per share: Basic $ 6.36 $ 3.59 $ 3.87 Diluted 6.29 3.55 3.83 Number of anti-dilutive share-based awards 0.7 0.3 0.4 The current sources of dilution of our common shares are certain equity-based awards as discussed in Note 17, Share-Based Associate Compensation Plans. The above table includes the number of anti-dilutive share-based awards at year-end 2017 , 2016 and 2015 . We did not include these share-based awards in the computation of net income per common share (diluted) because their exercise would have anti-dilutive effects. Our 2017 net income and basic and diluted earnings per share were impacted by the Tax Act as discussed in Note 11, Income Taxes.

Employee Retirement Benefits

Employee Retirement Benefits	12 Months Ended
	Dec. 31, 2017
Retirement Benefits [Abstract]
Employee Retirement Benefits	Employee Retirement Benefits We sponsor a qualified defined benefit pension plan that we closed entry into for new associates as of June 30, 2008, and only participants 40 years of age or older as of August 31, 2008, could elect to continue to participate. During 2008, we changed the form of retirement benefit we offer some associates to a company match on contributions to a 401(k) plan as further explained below. For participants remaining in the pension plan, we continue to fund future benefit obligations. Benefits for the defined benefit pension plan are based on years of credited service and compensation level. Contributions are based on the prescribed method defined in the Pension Protection Act. Our net periodic benefit cost is based on certain actuarial assumptions and also is composed of several components that are determined using the projected unit credit actuarial cost method. The qualified plan has been amended to allow for distribution of vested balances to terminated participants. We sponsor a defined contribution plan (401(k) plan) with matching company contributions totaling $16 million , $14 million and $12 million during the years 2017 , 2016 and 2015 , respectively. Associates who are not accruing benefits under the pension plan are eligible to receive the company match of up to 6 percent of cash compensation. Participants vest in the company match for the 401(k) plan after three years of eligible service. We maintain a supplemental executive retirement plan (SERP) with a benefit obligation of $9 million at year-end 2017 and $15 million at year-end 2016 , which is included in the projected benefit obligation. The company also makes available to a select group of associates the CFC Top Hat Savings Plan, a nonqualified deferred compensation plan, which had a fair value of $31 million and $24 million at December 31, 2017 and 2016 , respectively. Company matching contributions to the CFC Top Hat Savings Plan totaled $1 million for the year 2017 and less than $1 million for both years 2016 and 2015. Defined Benefit Pension Plan Assumptions We evaluate our pension plan assumptions annually and update them as necessary. This is a summary of the weighted-average assumptions used to determine our benefit obligations at December 31 for the plans: Qualified Pension Plan SERP 2017 2016 2017 2016 Discount rate 3.73 % 4.30 % 3.61 % 4.10 % Rate of compensation increase 2.75-3.25 2.75-3.25 2.75-3.25 2.75-3.25 To determine the discount rate for each plan, a theoretical settlement portfolio of high-quality rated corporate bonds was chosen to provide payments approximately matching the plan’s projected benefit payments. A single interest rate for each plan was determined resulting in a discounted value of the plan's benefit payments that equates to the market value of the selected bonds. The discount rate is reflective of current market interest rate conditions and our plan's liability characteristics. Based on this analysis, we decreased the rate from the prior year by 0.57 percentage points for the qualified pension plan and by 0.49 percentage points for the SERP. Compensation increase assumptions reflect anticipated rates of inflation, real return on wage growth and merit and promotional increases. The mortality assumption is updated annually to reflect the updated scale. The RP-2014 Employee Mortality Tables and RP-2014 Annuitant Mortality Tables for males and females projected generationally with Scale MP-2017, Scale MP-2016 and Scale MP-2015 were used for the years 2017, 2016 and 2015, respectively. The updated mortality table did not have a significant impact on our consolidated financial statements as our qualified plan assumes the majority of benefits will be paid in the form of lump sums. This is a summary of the weighted-average assumptions used to determine our net periodic benefit cost for the plans: Qualified Pension Plan SERP 2017 2016 2015 2017 2016 2015 Discount rate 4.30 % 4.55 % 4.25 % 4.10 % 4.30 % 4.05 % Expected return on plan assets 7.25 7.25 7.25 n/a n/a n/a Rate of compensation increase 2.75-3.25 2.75-3.25 2.75-3.25 2.75-3.25 2.75-3.25 2.75-3.25 The discount rate was decreased by 0.25 percentage points for the qualified pension plan and 0.20 percentage points for the SERP due to market interest rate conditions at the beginning of 2017 . The discount rate assumptions for our benefit obligation generally track with high-quality rated corporate bond yields chosen in our theoretical settlement portfolio, and yearly adjustments reflect any changes to those bond yields. We believe the expected return on plan assets is representative of the expected long-term rate of return on these assets, which is consistent with 2017 expectations of interest rates and based partially on the fact that the plan’s common stock holdings pay dividends. We review historical actual return on plan assets when determining our expected long-term rate of return. Total portfolio return for 2017 was 17.4 percent and for 2016 was 16.6 percent. Our compensation increase assumptions in 2017 reflect anticipated rates of inflation, real return on wage growth and merit and promotional increases. Benefit obligation activity using an actuarial measurement date for our qualified pension plan and SERP at December 31 follows: (Dollars in millions) At December 31, 2017 2016 Change in projected benefit obligation: Benefit obligation, January 1 $ 340 $ 323 Service cost 11 11 Interest cost 14 14 Actuarial loss 20 13 Benefits paid (34 ) (21 ) Projected benefit obligation, December 31 $ 351 $ 340 Change in plan assets: Fair value of plan assets, January 1 $ 315 $ 278 Actual return on plan assets 52 45 Employer contribution 12 13 Benefits paid (34 ) (21 ) Fair value of plan assets, December 31 $ 345 $ 315 Funded status, December 31 $ (6 ) $ (25 ) Accumulated benefit obligation $ 322 $ 309 Our unfunded status improved for 2017 primarily due to better-than-expected return on plan assets partially offset by actuarial losses resulting largely from decreases in discount rate and assumed lump sum rates. A reconciliation follows of the funded status for our qualified plan and SERP at the end of the measurement period to the amounts recognized in the consolidated balance sheets at December 31: (Dollars in millions) At December 31, 2017 2016 Pension amounts recognized in the consolidated balance sheets: Other liabilities $ (6 ) $ (25 ) Total $ (6 ) $ (25 ) Pension amounts recognized in accumulated other comprehensive income: Net actuarial loss $ 12 $ 26 Prior service cost — — Total $ 12 $ 26 Below are the components of our net periodic benefit cost, as well as other changes in plan assets and benefit obligations recognized in other comprehensive income for our qualified plan and SERP at December 31: (Dollars in millions) Years ended December 31, 2017 2016 2015 Net periodic benefit cost: Service cost $ 11 $ 11 $ 12 Interest cost 14 14 14 Expected return on plan assets (21 ) (19 ) (18 ) Amortization of actuarial loss and prior service cost 2 3 6 Other 1 — 1 Net periodic benefit cost $ 7 $ 9 $ 15 Other changes in plan assets and benefit obligations recognized in other comprehensive income: Current year actuarial (gain) loss $ (11 ) $ (13 ) $ 13 Amortization of actuarial loss (3 ) (2 ) (6 ) Amortization of prior service cost — (1 ) (1 ) Total recognized in other comprehensive (income) loss $ (14 ) $ (16 ) $ 6 Total recognized in net periodic benefit cost and other comprehensive (income) loss $ (7 ) $ (7 ) $ 21 The 2017 amount recognized in net periodic benefit cost and other comprehensive income remained unchanged from 2016. The 2016 change in the amount recognized in other comprehensive income from 2015 is largely due to better-than-expected investment return partially offset with decreases in discount and assumed lump sum rates. The estimated costs to be amortized from AOCI into net periodic benefit cost over the next year for our plans are $1 million in actuarial loss and less than $1 million in prior service cost. Defined Benefit Pension Plan Assets The pension plan assets are managed to maximize total return over the long term while providing sufficient liquidity and current return to satisfy the cash flow requirements of the plan. The plan’s day-to-day investment decisions are managed by our internal investment department; however, overall investment strategies are discussed with our employee benefits committee. Our investment strategy, currently driven by the low interest rate environment, is to weight our portfolio towards large-cap, high-quality, dividend-growing equities that we have historically favored. As our plan matures and interest rates normalize, we expect a greater allocation to fixed-income securities to better align asset and liability market risks. Our fixed-maturity bond portfolio is investment grade. The plan does not engage in derivative transactions. Excluding cash, during 2017 we held approximately 80 percent of our pension portfolio in domestic common equity investments. The remainder of the portfolio consisted of 9 percent in states, municipalities and taxable political subdivisions fixed-maturity investments and 11 percent in domestic corporate fixed-maturity investments. Our common equity portfolio consisted of 22 percent in both the the information technology sector and financial sector, 15 percent in the healthcare sector, 13 percent in the consumer discretionary sector and 12 percent in the industrial sector at year-end 2017 . No additional sectors accounted for 10 percent or more of our common equity portfolio balance at year-end 2017 . Investments in securities are valued based on the fair value hierarchy outlined in Note 3, Fair Value Measurements. The pension plan did not have any liabilities carried at fair value during the years ended December 31, 2017 and 2016 . There have been no transfers between Level 1 and Level 2 for the years ended December 31, 2017 and 2016 . The following table shows the fair value hierarchy for those assets measured at fair value on a recurring basis at December 31, 2017 and 2016 . Excluded from the table below is cash on hand of $18 million and $11 million at December 31, 2017 and 2016 , respectively. (Dollars in millions) Quoted prices in Significant other Significant (Level 3) Total At December 31, 2017 Fixed maturities, available for sale: States, municipalities and political subdivisions $ — $ 31 $ — $ 31 Corporate — 34 — 34 Total fixed maturities, available for sale — 65 — 65 Common equities, available for sale 262 — — 262 Total $ 262 $ 65 $ — $ 327 At December 31, 2016 Fixed maturities, available for sale: States, municipalities and political subdivisions $ — $ 31 $ — $ 31 Corporate — 20 — 20 Total fixed maturities, available for sale — 51 — 51 Common equities, available for sale 253 — — 253 Total $ 253 $ 51 $ — $ 304 Our pension plan assets included 232,113 shares of the company’s common stock at both December 31, 2017 and 2016 , which had a fair value of $17 million and $18 million at December 31, 2017 and 2016 , respectively. The defined benefit pension plan did not purchase any shares of our common stock during 2017 and 2016 . No shares of our common stock were sold during 2017 . During 2016, the pension plan sold 35,000 shares of the company’s common stock. The company paid $1 million in 2017 and less than $1 million in 2016 in cash dividends on our common stock to the pension plan. We contributed $5 million to our qualified plan during the first quarter of 2018 and estimate $5 million of benefit payments from the SERP during 2018 . We expect to make the following benefit payments for our qualified plan and SERP, reflecting expected future service: (Dollars in millions) Years ended December 31, 2018 2019 2020 2021 2022 2023 - 2027 Expected future benefit payments $ 26 $ 24 $ 25 $ 29 $ 26 $ 146

Statutory Accounting Informatio

Statutory Accounting Information	12 Months Ended
	Dec. 31, 2017
Staturory Accounting Information [Abstract]
Statutory Accounting Information	Statutory Accounting Information Insurance companies’ statutory financial statements are presented on the basis of accounting practices prescribed or permitted by applicable state insurance departments of domicile. Insurance companies use statutory accounting practices (SAP) as recognized by various states. We have adopted the National Association of Insurance Commissioners’ (NAIC) Accounting Practices and Procedures manual, version effective January 1, 2001, and updates through the current year as a component of prescribed or permitted practices by laws of the state of domicile. The primary differences between SAP and GAAP include the valuation of unrealized investment gains and losses, expensing of policy acquisition costs, actuarial assumptions for life insurance reserves and deferred income taxes based on differences in statutory and taxable income. Statutory net income (loss) and capital and surplus are determined in accordance with SAP prescribed or permitted by insurance regulatory authorities for five legal entities, our insurance subsidiary and its four insurance subsidiaries. Statutory capital and surplus for our insurance subsidiary, The Cincinnati Insurance Company, includes capital and surplus of its four insurance subsidiaries. All capital and surplus amounts exceed statutory risk-based capital requirements. The statutory net income (loss) and statutory capital and surplus are presented below: (Dollars in millions) Net income (loss) Capital and surplus Years ended December 31, At December 31, 2017 2016 2015 2017 2016 The Cincinnati Insurance Company $ 401 $ 434 $ 534 $ 5,094 $ 4,686 The Cincinnati Casualty Company 21 11 12 392 360 The Cincinnati Indemnity Company 4 4 3 100 93 The Cincinnati Specialty Underwriters Insurance Company 58 57 49 436 372 The Cincinnati Life Insurance Company 12 2 (11 ) 195 200

Transactions With Affiliated Pa

Transactions With Affiliated Parties	12 Months Ended
	Dec. 31, 2017
Related Party Transactions [Abstract]
Transactions With Affiliated Parties	Transactions With Affiliated Parties We paid certain officers and directors, or insurance agencies of which they are shareholders, commissions of $7 million in 2017 , 2016 and 2015 , on premium volume of $45 million , $44 million and $42 million for 2017 , 2016 and 2015 , respectively.

Commitments And Contingent Liab

Commitments And Contingent Liabilities	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments And Contingent Liabilities	Commitments and Contingent Liabilities In the ordinary course of conducting business, the company and its subsidiaries are named as defendants in various legal proceedings. Most of these proceedings are claims litigation involving the company's insurance subsidiaries in which the company is either defending or providing indemnity for third-party claims brought against insureds or litigating first-party coverage claims. The company accounts for such activity through the establishment of unpaid loss and loss expense reserves. We believe that the ultimate liability, if any, with respect to such ordinary-course claims litigation, after consideration of provisions made for potential losses and costs of defense, is immaterial to our consolidated financial condition, results of operations and cash flows. The company and its subsidiaries also are occasionally involved in other legal and regulatory proceedings, some of which assert claims for substantial amounts. These actions include, among others, putative class actions seeking certification of a state or national class. Such proceedings have alleged, for example, breach of an alleged duty to search national databases to ascertain unreported deaths of insureds under life insurance policies. The company's insurance subsidiaries also are occasionally parties to individual actions in which extra-contractual damages, punitive damages or penalties are sought, such as claims alleging bad faith handling of insurance claims or writing unauthorized coverage or claims alleging discrimination by former or current associates. On a quarterly basis, we review these outstanding matters. Under current accounting guidance, we establish accruals when it is probable that a loss has been incurred and we can reasonably estimate its potential exposure. The company accounts for such probable and estimable losses, if any, through the establishment of legal expense reserves. Based on our quarterly review, we believe that our accruals for probable and estimable losses are reasonable and that the amounts accrued do not have a material effect on our consolidated financial condition or results of operations. However, if any one or more of these matters results in a judgment against us or settlement for an amount that is significantly greater than the amount accrued, the resulting liability could have a material effect on the company's consolidated results of operations or cash flows. Based on our most recent review, our estimate for any other matters for which the risk of loss is not probable, but more than remote, is immaterial.

Share-Based Associate Compensat

Share-Based Associate Compensation Plans	12 Months Ended
	Dec. 31, 2017
Share-based Compensation [Abstract]
Stock-Based Associate Compensation Plans	Share-Based Associate Compensation Plans Four equity compensation plans currently permit us to grant various types of equity awards. We currently grant incentive stock options, nonqualified stock options, service-based restricted stock units and performance-based restricted stock units to associates, including some with market-based performance objectives under our shareholder-approved plans. We also have a Holiday Stock Plan that permits annual awards of one share of common stock to each full-time associate for each full calendar year of service up to a maximum of 10 shares. One of our equity compensation plans permits us to grant stock to our outside directors as a component of their annual compensation. We used treasury shares for share-based compensation award issues or exercises during 2017 and 2016. Share-based compensation cost after tax was $17 million , $15 million and $14 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. The related income tax benefit recognized was $9 million , $8 million , and $6 million for the years ended December 31, 2017, 2016 and 2015, respectively. Options exercised during the years ended December 31, 2017 , 2016 and 2015 , had intrinsic value of $19 million , $25 million and $15 million , respectively. Intrinsic value is the market price less the exercise price. Options vested during the years ended December 31, 2017 , 2016 and 2015 , had total intrinsic value of $8 million , $11 million and $7 million , respectively. As of December 31, 2017 , we had $28 million of unrecognized total compensation cost related to nonvested stock options and restricted stock unit awards. That cost will be recognized over a weighted-average period of 1.7 years. Stock Options Stock options are granted to associates at an exercise price equal to the fair value as determined by the average high and low sales price reported on the Nasdaq Global Select Market for the grant date and are exercisable over 10 -year periods. The stock options generally vest ratably over a three -year period. In determining the share-based compensation amounts, we estimate the fair value of each option granted on the date of grant using a binomial option-pricing model. We make the following assumptions to develop the binomial option-pricing model as follows: • Weighted-average expected term is based on historical experience of similar awards with consideration for current exercise trends. • Expected volatility is based on our stock price over a historical period that approximates the expected term. • Dividend yield is determined by dividing the annualized per share dividend by the stock price on the date of grant. • Risk-free rates are the implied yield currently available on zero-coupon U.S. Treasury issues with a remaining term approximating the expected term. The following weighted average assumptions were used in determining fair value for option grants issued: 2017 2016 2015 Weighted-average expected term 8 years 8 years 8-9 years Expected volatility 16.95% 24.88-25.75% 25.04-26.15% Dividend yield 2.83% 2.58-3.12% 3.52% Risk-free rates 2.33% 1.44-1.60% 1.94-2.01% Weighted-average fair value of options granted during the period $10.79 $13.21 $11.15 Below is a summary of option information for the year 2017 : (Dollars in millions, except exercise price. Shares in thousands) Shares Weighted- exercise price Aggregate Weighted-average Outstanding option shares at January 1, 2017 3,012 $ 42.12 Granted 706 70.70 Exercised (527 ) 38.33 Forfeited or expired (125 ) 47.07 Outstanding option shares at December 31, 2017 3,066 49.14 $ 79 5.61 years Options exercisable at end of period 2,072 $ 40.69 $ 71 4.13 years Cash received from the exercise of options was $13 million , $21 million and $24 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. We acquired 96,030 , 186,097 and 292,414 shares totaling $7 million , $13 million and $16 million , respectively, from associates in consideration for option exercises during 2017 , 2016 and 2015 . The weighted-average remaining contractual life for options expected to vest as of December 31, 2017 , was 8.69 years . Under all active shareholder approved plans, a total of 17.3 million shares were authorized to be granted. At December 31, 2017 , 11.3 million shares remained available for future issuance under the plans. During 2017 , we granted 15,040 shares of common stock to our directors for 2016 board service fees. Restricted Stock Units Service-based restricted stock units granted to associates are valued at fair value of the shares on the date of grant less the present value of the dividends that holders of restricted stock units do not receive on the shares underlying the restricted stock units during the vesting period. Service-based restricted stock units generally cliff vest three years after the date of grant. We also grant restricted stock units which vest on a three year ratable vesting schedule. Service-based restricted stock units vested during the year had an intrinsic value of $23 million , $23 million and $26 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. We have performance-based awards that vest on the first day of March after a three -calendar-year performance period. These awards vest according to the level of three -year total shareholder return achieved compared with a peer group over a three -year performance period with payouts ranging from 0 to 200 percent for awards granted in 2015 , 2016 and 2017 . Three -year total shareholder return is calculated by using annualized total return of a stock to an investor due to capital gain appreciation plus reinvestment of all dividends. For the three-year performance period ended December 31, 2017, our total shareholder return exceeded five of our nine peers. We expect payout of these shares at the target level to occur in March of 2018. During 2017, we issued 87,228 shares of performance-based restricted stock units at the target-level performance hurdle for the three-year performance period ended December 31, 2016, as our total shareholder return exceeded five of nine peers in our 2014 peer group. We issued 25,461 shares of performance-based restricted stock units during 2016 at the threshold-level performance hurdle for the three -year performance period ended December 31, 2015, as we achieved a three -year total shareholder return that exceeded four of 10 peers in our 2013 peer group. Performance-based awards vested during the year had an intrinsic value of $7 million for the year ended December 31, 2017 and $6 million for both years ended 2016 and 2015 . These performance-based awards are valued using a Monte-Carlo valuation on the date of grant, which uses a risk-neutral framework to model future stock price movements based upon the risk-free rate of return, the volatility of each peer and the pairwise correlations of each peer being modeled. Compensation cost is recognized regardless of whether the market-based performance objective has been satisfied. We make assumptions to develop the Monte-Carlo model as follows: • Correlation coefficients are based upon the stock price data used to calculate the historical volatilities. The correlation coefficients are used to model the way the price of each entity's stock tends to move in relation to each other. • Expected volatility is based on each company's historical volatility using daily stock price observations with the period commensurate with the performance measurement period. • Dividend yield has been modeled assuming dividends are reinvested in additional shares of the issuing entity on the ex-dividend date during the performance period. • Risk-free rates are equal to the yield, as of the measurement date, of the zero-coupon U.S. Treasury bill that is commensurate with the performance measurement period. The following assumptions were used in determining fair value for performance-based grants issued: 2017 2016 2015 Expected term 2.89 years 2.44-2.88 years 2.88 years Expected volatility 15.75-28.35% 15.42-33.64% 13.78-34.69% Dividend yield 2.83% 2.58-3.12% 3.52% Risk-free rates 1.44% 0.77-0.87% 0.99% Below is a summary of service-based and performance-based share information, assuming a target payout for performance-based shares, for the year 2017 : (Shares in thousands) Service-based Weighted- Performance-based Weighted- Nonvested at January 1, 2017 888 $ 48.59 236 $ 49.64 Granted 292 65.16 57 43.26 Vested (311 ) 43.05 (87 ) 36.73 Forfeited or canceled (26 ) 55.59 — — Nonvested at December 31, 2017 843 56.16 206 53.35

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Segment Information	Segment Information We operate primarily in two industries, property casualty insurance and life insurance. Our chief operating decision maker regularly reviews our reporting segments to make decisions about allocating resources and assessing performance. Our reporting segments are: • Commercial lines insurance • Personal lines insurance • Excess and surplus lines insurance • Life insurance • Investments We report as Other the noninvestment operations of the parent company and its noninsurer subsidiary, CFC Investment Company and Cincinnati Re, our reinsurance assumed operations. Revenues come primarily from unaffiliated customers: • All four insurance segments record revenues from insurance premiums earned. • Fee revenues for the commercial, personal and excess and surplus insurance segments primarily represent installment fees. Fee revenues for the life insurance segment represent separate account investment management fees. • Our investments’ revenues consist of pretax net investment income and realized investment gains and losses. • Other revenues are primarily finance income and earned premiums of Cincinnati Re. Income or loss before income taxes for each segment is reported based on the nature of that business area’s operations: • Income before income taxes for the insurance segments is defined as underwriting profit or loss. ◦ For commercial lines, personal lines and excess and surplus lines insurance segments, we calculate underwriting profit or loss as premiums earned and fee revenue minus loss and loss expenses and underwriting expenses incurred. ◦ For the life insurance segment, we calculate underwriting profit or loss as premiums earned and fee revenue, minus contract holders’ benefits and expenses incurred, plus investment interest credited to contract holders. • Income before income taxes for the investments segment is net investment income plus realized investment gains and losses for investments of the entire company, minus investment interest credited to contract holders of the life insurance segment. • Loss before income taxes for the Other category is primarily due to interest expense from debt of the parent company, operating expenses of our headquarters and premiums earned minus loss and loss expenses and underwriting expenses of Cincinnati Re. Identifiable assets are used by each segment in its operations. We do not separately report the identifiable assets for the commercial, personal or excess and surplus lines segments because we do not use that measure to analyze the segments. We include all investment assets, regardless of ownership, in the investments segment. Segment information is summarized in the following table: (Dollars in millions) Years ended December 31, 2017 2016 2015 Revenues: Commercial lines insurance Commercial casualty $ 1,072 $ 1,050 $ 1,010 Commercial property 903 867 815 Commercial auto 634 594 561 Workers' compensation 335 354 367 Other commercial 221 224 243 Commercial lines insurance premiums 3,165 3,089 2,996 Fee revenues 5 5 4 Total commercial lines insurance 3,170 3,094 3,000 Personal lines insurance Personal auto 582 543 506 Homeowner 518 486 463 Other personal 141 132 128 Personal lines insurance premiums 1,241 1,161 1,097 Fee revenues 5 4 3 Total personal lines insurance 1,246 1,165 1,100 Excess and surplus lines insurance 209 183 168 Fee revenues 1 1 1 Total excess and surplus lines insurance 210 184 169 Life insurance premiums 232 228 209 Fee revenues 5 5 5 Total life insurance 237 233 214 Investments Investment income, net of expenses 609 595 572 Realized investment gains, net 148 124 70 Total investment revenue 757 719 642 Other Cincinnati Re insurance premiums 107 49 10 Other 5 5 7 Total other revenue 112 54 17 Total revenues $ 5,732 $ 5,449 $ 5,142 Income (loss) before income taxes: Insurance underwriting results Commercial lines insurance $ 119 $ 184 $ 345 Personal lines insurance (32 ) (12 ) (12 ) Excess and surplus lines insurance 61 62 51 Life insurance (1 ) 1 (2 ) Investments 664 629 556 Other (81 ) (52 ) (57 ) Total income before income taxes $ 730 $ 812 $ 881 December 31, December 31, Identifiable assets: 2017 2016 Property casualty insurance $ 2,863 $ 2,967 Life insurance 1,409 1,366 Investments 17,112 15,569 Other 459 484 Total $ 21,843 $ 20,386

Quarterly Supplementary Data

Quarterly Supplementary Data	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Quarterly Supplementary Data	Quarterly Supplementary Data This table includes unaudited quarterly financial information for the years ended December 31, 2017 and 2016 : (Dollars in millions, except per share data) Quarter 1st 2nd 3rd 4th Full year 2017 Revenues $ 1,523 $ 1,386 $ 1,412 $ 1,411 $ 5,732 Income before income taxes 276 128 129 197 730 Net income 201 100 102 642 1,045 Net income per common share—basic 1.22 0.61 0.62 3.92 6.36 Net income per common share—diluted 1.21 0.60 0.61 3.88 6.29 2016 Revenues $ 1,364 $ 1,371 $ 1,402 $ 1,312 $ 5,449 Income before income taxes 265 166 253 128 812 Net income 188 123 180 100 591 Net income per common share—basic 1.14 0.75 1.09 0.61 3.59 Net income per common share—diluted 1.13 0.74 1.08 0.60 3.55 The sum of the quarterly reported per share amounts may not equal the full year as each is computed independently. Revenues including realized investment gains and losses, which are integral to our financial results over the long term, may cause this value to fluctuate substantially because we have substantial discretion in the timing of investment sales. Also, applicable accounting standards require us to recognize gains and losses from certain changes in fair values of securities and embedded derivatives without actual realization of those gains and losses.

Summary Of Investments Other Th

Summary Of Investments Other Than Investments In Related Parties	12 Months Ended
	Dec. 31, 2017
Summary of Investments, Other than Investments in Related Parties [Abstract]
Summary Of Investments Other Than Investments In Related Parties	Schedule I Cincinnati Financial Corporation and Subsidiaries Summary of Investments - Other Than Investments in Related Parties (Dollars in millions) At December 31, 2017 Type of investment Cost or amortized cost Fair value Balance sheet Fixed maturities: States, municipalities and political subdivisions: The Cincinnati Insurance Company $ 3,310 $ 3,421 $ 3,421 The Cincinnati Casualty Company 184 190 190 The Cincinnati Indemnity Company 44 46 46 The Cincinnati Life Insurance Company 306 320 320 The Cincinnati Specialty Underwriters Insurance Company 469 485 485 CSU Producer Resources Inc. 1 1 1 Cincinnati Financial Corporation 2 2 2 Total 4,316 4,465 4,465 United States government: The Cincinnati Insurance Company 28 28 28 The Cincinnati Casualty Company 2 2 2 The Cincinnati Indemnity Company 1 1 1 Total 31 31 31 Government-sponsored enterprises: The Cincinnati Life Insurance Company 257 254 254 Total 257 254 254 Foreign government: The Cincinnati Insurance Company 10 10 10 Total 10 10 10 All other corporate bonds: The Cincinnati Insurance Company 2,644 2,747 2,747 The Cincinnati Casualty Company 99 104 104 The Cincinnati Indemnity Company 28 29 29 The Cincinnati Specialty Underwriters Insurance Company 137 143 143 The Cincinnati Life Insurance Company 2,758 2,880 2,880 CSU Producer Resources Inc. 1 1 1 Cincinnati Financial Corporation 33 35 35 Total 5,700 5,939 5,939 Total fixed maturities $ 10,314 $ 10,699 $ 10,699 Schedule I (continued) Cincinnati Financial Corporation and Subsidiaries Summary of Investments - Other Than Investments in Related Parties (Dollars in millions) At December 31, 2017 Type of investment Cost or amortized cost Fair value Balance sheet Equity securities: Common equities: The Cincinnati Insurance Company $ 1,615 $ 3,479 $ 3,479 The Cincinnati Casualty Company 56 118 118 The Cincinnati Indemnity Company 13 25 25 The Cincinnati Specialty Underwriters Insurance Company 61 120 120 CSU Producer Resources Inc. 15 23 23 Cincinnati Financial Corporation 1,158 2,274 2,274 Total 2,918 6,039 6,039 Nonredeemable preferred equities: The Cincinnati Insurance Company 170 200 200 The Cincinnati Life Insurance Company 5 9 9 Cincinnati Financial Corporation 1 1 1 Total 176 210 210 Total equity securities $ 3,094 $ 6,249 $ 6,249 Other invested assets: Policy loans: The Cincinnati Life Insurance Company $ 31 — $ 31 Private equity: Cincinnati Financial Corporation (1) 29 — 29 The Cincinnati Life Insurance Company (1) 6 — 6 Real estate: The Cincinnati Life Insurance Company (1) 31 — 31 Cincinnati Financial Corporation (1) 6 — 6 Total other invested assets $ 103 — $ 103 Total investments $ 13,511 — $ 17,051

Condensed Financial Statements

Condensed Financial Statements Of Parent Company	12 Months Ended
	Dec. 31, 2017
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Condensed Financial Statements Of Parent Company	Schedule II Cincinnati Financial Corporation (parent company only) Condensed Balance Sheets (Dollars in millions) At December 31, 2017 2016 Assets Investments Fixed maturities, at fair value (amortized cost: 2017—$35; 2016—$46) $ 37 $ 52 Equity securities, at fair value (cost: 2017—$1,159; 2016—$1,084) 2,275 1,833 Other invested assets 35 29 Total investments 2,347 1,914 Cash and cash equivalents 199 248 Equity in net assets of subsidiaries 6,542 5,790 Investment income receivable 8 8 Land, building and equipment, net, for company use (accumulated depreciation: 130 132 Income tax receivable 15 10 Other assets 52 35 Due from subsidiaries 107 106 Total assets $ 9,400 $ 8,243 Liabilities Dividends declared but unpaid $ 82 $ 79 Deferred federal income tax 234 252 Long-term debt 787 787 Other liabilities 54 65 Total liabilities 1,157 1,183 Shareholders' Equity Common stock 397 397 Paid-in capital 1,265 1,252 Retained earnings 5,180 5,037 Accumulated other comprehensive income 2,788 1,693 Treasury stock at cost (1,387 ) (1,319 ) Total shareholders' equity 8,243 7,060 Total liabilities and shareholders' equity $ 9,400 $ 8,243 This condensed financial information should be read in conjunction with the Consolidated Financial Statements and Notes included in Part II, Item 8. Schedule II (continued) Cincinnati Financial Corporation (parent company only) Condensed Statements of Income (Dollars in millions) Years ended December 31, 2017 2016 2015 Revenues Investment income, net of expenses $ 62 $ 56 $ 53 Realized investment gains and (losses), net 28 27 (19 ) Other revenue 15 15 15 Total revenues 105 98 49 Expenses Interest expense 52 52 52 Other expenses 28 27 28 Total expenses 80 79 80 Income (Loss) Before Income Taxes and Earnings of Subsidiaries 25 19 (31 ) Benefit for income taxes (161 ) (6 ) (23 ) Net Income (Loss) Before Earnings of Subsidiaries 186 25 (8 ) Increase in equity of subsidiaries 859 566 642 Net Income $ 1,045 $ 591 $ 634 This condensed financial information should be read in conjunction with the Consolidated Financial Statements and Notes included in Part II, Item 8. Schedule II (continued) Cincinnati Financial Corporation (parent company only) Condensed Statements of Comprehensive Income (Dollars in millions) Years ended December 31, 2017 2016 2015 Net Income $ 1,045 $ 591 $ 634 Other Comprehensive Income, Before Tax Unrealized gains and (losses) on investments available for sale 391 221 (111 ) Unrealized gains and (losses) on investments held by subsidiaries 672 434 (444 ) Reclassification adjustment for (gains) and losses included in net income (28 ) (27 ) 19 Reclassification adjustment for (gains) included in net income on subsidiaries (120 ) (97 ) (89 ) Unrealized (losses) and gains on other (2 ) (6 ) — Unrealized gains and (losses) on other subsidiaries 1 (4 ) 13 Unrealized gains and (losses) on investments available for sale, investments held by subsidiaries and other 914 521 (612 ) Amortization of pension actuarial gains (losses) and prior service cost 14 16 (6 ) Other comprehensive income (loss) before tax 928 537 (618 ) Income taxes on above of other comprehensive income (loss) 325 188 (218 ) Other comprehensive income (loss), net of tax 603 349 (400 ) Comprehensive Income $ 1,648 $ 940 $ 234 This condensed financial information should be read in conjunction with the Consolidated Financial Statements and Notes included in Part II, Item 8. Schedule II (continued) Cincinnati Financial Corporation (parent company only) Condensed Statements of Cash Flows (Dollars in millions) Years ended December 31, 2017 2016 2015 Cash Flows From Operating Activities Net income $ 1,045 $ 591 $ 634 Adjustments to reconcile net income to net cash provided by operating activities: Depreciation and amortization 7 6 7 Realized investment (gains) and losses, net (28 ) (27 ) 19 Dividends from subsidiaries 465 475 447 Changes in: Increase in equity of subsidiaries (859 ) (566 ) (642 ) Investment income receivable — (2 ) — Current federal income taxes (5 ) (4 ) (7 ) Deferred income tax (150 ) 8 (10 ) Other assets (20 ) (4 ) (3 ) Other liabilities 15 (1 ) 13 Intercompany receivable for operations 13 20 16 Net cash provided by operating activities 483 496 474 Cash Flows From Investing Activities Call or maturity of fixed maturities 14 5 8 Sale of equity securities 230 135 54 Purchase of fixed maturities (2 ) — — Purchase of equity securities (293 ) (175 ) (110 ) Investment in buildings and equipment (3 ) (2 ) — Change in other invested assets, net — 6 1 Net cash used in investing activities (54 ) (31 ) (47 ) Cash Flows From Financing Activities Payment of cash dividends to shareholders (400 ) (306 ) (366 ) Shares acquired - share repurchase authorization (92 ) (39 ) (53 ) Proceeds from stock options exercised 13 21 24 Other 1 1 2 Net cash used in financing activities (478 ) (323 ) (393 ) Net change in cash and cash equivalents (49 ) 142 34 Cash and cash equivalents at beginning of year 248 106 72 Cash and cash equivalents at end of year $ 199 $ 248 $ 106 This condensed financial information should be read in conjunction with the Consolidated Financial Statements and Notes included in Part II, Item 8.

Supplementary Insurance Informa

Supplementary Insurance Information	12 Months Ended
	Dec. 31, 2017
Supplementary Insurance Information [Abstract]
Supplementary Insurance Information	Schedule III Cincinnati Financial Corporation and Subsidiaries Supplementary Insurance Information (Dollars in millions) Years ended December 31, 2017 2016 2015 Deferred policy acquisition costs: Commercial lines insurance $ 284 $ 271 $ 264 Personal lines insurance 121 110 103 Excess and surplus lines insurance 17 16 15 Cincinnati Re 16 11 6 Total property casualty insurance 438 408 388 Life insurance 232 229 228 Total $ 670 $ 637 $ 616 Gross future policy benefits, losses, claims and expense losses: Commercial lines insurance $ 4,236 $ 4,179 $ 3,925 Personal lines insurance 587 569 498 Excess and surplus lines insurance 264 241 227 Cincinnati Re 132 46 10 Total property casualty insurance 5,219 5,035 4,660 Life insurance 2,753 2,693 2,605 Total (1) $ 7,972 $ 7,728 $ 7,265 Gross unearned premiums: Commercial lines insurance $ 1,548 $ 1,510 $ 1,472 Personal lines insurance 683 629 593 Excess and surplus lines insurance 105 93 87 Cincinnati Re 67 74 48 Total property casualty insurance 2,403 2,306 2,200 Life insurance 1 1 1 Total (1) $ 2,404 $ 2,307 $ 2,201 Other policy claims and benefits payable: Commercial lines insurance $ — $ — $ — Personal lines insurance — — — Excess and surplus lines insurance — — — Cincinnati Re — — — Total property casualty insurance — — — Life insurance 30 28 36 Total (1) $ 30 $ 28 $ 36 Earned premiums: Commercial lines insurance $ 3,165 $ 3,089 $ 2,996 Personal lines insurance 1,241 1,161 1,097 Excess and surplus lines insurance 209 183 168 Cincinnati Re 107 49 10 Total property casualty insurance 4,722 4,482 4,271 Life insurance 232 228 209 Total $ 4,954 $ 4,710 $ 4,480 Schedule III (continued) Cincinnati Financial Corporation and Subsidiaries Supplementary Insurance Information (Dollars in millions) Years ended December 31, 2017 2016 2015 Investment income, net of expenses: Commercial lines insurance $ — $ — $ — Personal lines insurance — — — Excess and surplus lines insurance — — — Cincinnati Re — — — Total property casualty insurance (2) 392 384 368 Life insurance 155 155 150 Total $ 547 $ 539 $ 518 Benefits, claims losses and settlement expenses: Commercial lines insurance $ 2,042 $ 1,928 $ 1,708 Personal lines insurance 918 840 789 Excess and surplus lines insurance 86 68 70 Cincinnati Re 92 25 5 Total property casualty insurance 3,138 2,861 2,572 Life insurance 252 246 236 Total $ 3,390 $ 3,107 $ 2,808 Amortization of deferred policy acquisition costs: Commercial lines insurance $ 590 $ 570 $ 552 Personal lines insurance 225 209 210 Excess and surplus lines insurance 35 31 28 Cincinnati Re 17 10 2 Total property casualty insurance 867 820 792 Life insurance 46 43 37 Total (3) $ 913 $ 863 $ 829 Underwriting, acquisition and insurance expenses: Commercial lines insurance $ 419 $ 412 $ 395 Personal lines insurance 135 128 113 Excess and surplus lines insurance 28 23 20 Cincinnati Re 18 6 1 Total property casualty insurance 600 569 529 Life insurance 33 33 29 Total (3) $ 633 $ 602 $ 558 Net written premiums: Commercial lines insurance $ 3,202 $ 3,122 $ 3,025 Personal lines insurance 1,294 1,198 1,128 Excess and surplus lines insurance 219 189 175 Cincinnati Re 125 71 33 Total property casualty insurance 4,840 4,580 4,361 Accident health insurance 3 2 2 Total $ 4,843 $ 4,582 $ 4,363 Notes to Schedule III: (1) The sum of gross future policy benefits, losses, claims and expense losses, gross unearned premium and other policy claims and benefits payable is equal to the sum of Loss and loss expense reserves, Life policy reserves and investment contract reserves and Unearned premiums reported in the company’s consolidated balance sheets. (2) This segment information is not regularly allocated to segments and reviewed by company management in making decisions about resources to be allocated to the segments or to assess their performance. (3) The sum of amortization of deferred policy acquisition costs and other underwriting and insurance expenses is equal to Underwriting, acquisition and insurance expenses in the consolidated statements of income.

Reinsurance - Schedule IV

Reinsurance - Schedule IV	12 Months Ended
	Dec. 31, 2017
Supplemental Schedule of Reinsurance Premiums for Insurance Companies [Abstract]
Supplemental Schedule of Reinsurance Premiums for Insurance Companies [Text Block]	Schedule IV Cincinnati Financial Corporation and Subsidiaries Reinsurance (Dollars in millions) Years ended December 31, 2017 2016 2015 Gross amounts: Life insurance in force $ 99,888 $ 95,533 $ 91,451 Earned premiums Commercial lines insurance $ 3,258 $ 3,180 $ 3,088 Personal lines insurance 1,275 1,195 1,131 Excess and surplus lines insurance 219 192 177 Cincinnati Re — — — Total property casualty insurance 4,752 4,567 4,396 Life insurance 300 290 271 Total $ 5,052 $ 4,857 $ 4,667 Ceded amounts to other companies: Life insurance in force $ 38,711 $ 38,724 $ 38,716 Earned premiums Commercial lines insurance $ 99 $ 98 $ 102 Personal lines insurance 35 35 35 Excess and surplus lines insurance 10 9 9 Cincinnati Re 18 20 8 Total property casualty insurance 162 162 154 Life insurance 68 62 62 Total $ 230 $ 224 $ 216 Assumed amounts from other companies: Life insurance in force $ — $ — $ — Earned premiums Commercial lines insurance $ 6 $ 7 $ 10 Personal lines insurance 1 1 1 Excess and surplus lines insurance — — — Cincinnati Re 125 69 18 Total property casualty insurance 132 77 29 Life insurance — — — Total $ 132 $ 77 $ 29 Net amounts: Life insurance in force $ 61,177 $ 56,808 $ 52,735 Earned premiums Commercial lines insurance $ 3,165 $ 3,089 $ 2,996 Personal lines insurance 1,241 1,161 1,097 Excess and surplus lines insurance 209 183 168 Cincinnati Re 107 49 10 Total property casualty insurance 4,722 4,482 4,271 Life insurance 232 228 209 Total $ 4,954 $ 4,710 $ 4,480 Percentage of amounts assumed to net: Life insurance in force — % — % — % Earned premiums Commercial lines insurance 0.2 % 0.2 % 0.3 % Personal lines insurance 0.1 0.1 0.1 Excess and surplus lines insurance — — — Cincinnati Re 116.1 140.8 188.0 Total property casualty insurance 2.8 1.7 0.7 Life insurance — — — Total 2.7 1.6 0.7

Valuation And Qualifying Accoun

Valuation And Qualifying Accounts	12 Months Ended
	Dec. 31, 2017
Valuation and Qualifying Accounts [Abstract]
Valuation And Qualifying Accounts	Schedule V Cincinnati Financial Corporation and Subsidiaries Valuation and Qualifying Accounts (Dollars in millions) At December 31, 2017 2016 2015 Allowance for doubtful receivables: Beginning balance, January 1 $ 5 $ 4 $ 3 Additions charged to costs and expenses 6 5 3 Deductions (5 ) (4 ) (2 ) Ending balance, December 31 $ 6 $ 5 $ 4

Supplementary Information Conce

Supplementary Information Concerning Property Casualty Insurance Operations	12 Months Ended
	Dec. 31, 2017
Supplemental Information for Property, Casualty Insurance Underwriters [Abstract]
Supplementary Information Concerning Property Casualty Insurance Operations	Schedule VI Cincinnati Financial Corporation and Subsidiaries Supplementary Information Concerning Property Casualty Insurance Operations (Dollars in millions) Years ended December 31, 2017 2016 2015 Deferred policy acquisition costs: Commercial lines insurance $ 284 $ 271 $ 264 Personal lines insurance 121 110 103 Excess and surplus lines insurance 17 16 15 Cincinnati Re 16 11 6 Total $ 438 $ 408 $ 388 Reserves for unpaid claims and claim adjustment expenses: Commercial lines insurance $ 4,236 $ 4,179 $ 3,925 Personal lines insurance 587 569 498 Excess and surplus lines insurance 264 241 227 Cincinnati Re 132 46 10 Total $ 5,219 $ 5,035 $ 4,660 Reserve discount deducted $ — $ — $ — Gross unearned premiums: Commercial lines insurance $ 1,548 $ 1,510 $ 1,472 Personal lines insurance 683 629 593 Excess and surplus lines insurance 105 93 87 Cincinnati Re 67 74 48 Total $ 2,403 $ 2,306 $ 2,200 Earned premiums: Commercial lines insurance $ 3,165 $ 3,089 $ 2,996 Personal lines insurance 1,241 1,161 1,097 Excess and surplus lines insurance 209 183 168 Cincinnati Re 107 49 10 Total $ 4,722 $ 4,482 $ 4,271 Investment income, net of expenses: Commercial lines insurance $ — $ — $ — Personal lines insurance — — — Excess and surplus lines insurance — — — Cincinnati Re — — — Total (1) $ 392 $ 384 $ 368 Note to Schedule VI: (1) This segment information is not regularly allocated to segments and not reviewed by company management in making decisions about resources to be allocated to the segments or to assess their performance. Schedule VI (continued) Cincinnati Financial Corporation and Subsidiaries Supplementary Information Concerning Property Casualty Insurance Operations (Dollars in millions) Years ended December 31, 2017 2016 2015 Loss and loss expenses incurred related to current accident year: Commercial lines insurance $ 2,115 $ 2,057 $ 1,862 Personal lines insurance 932 844 784 Excess and surplus lines insurance 115 102 105 Cincinnati Re 95 26 5 Total $ 3,257 $ 3,029 $ 2,756 Loss and loss expenses incurred related to prior accident years: Commercial lines insurance $ (73 ) $ (129 ) $ (154 ) Personal lines insurance (14 ) (4 ) 5 Excess and surplus lines insurance (29 ) (34 ) (35 ) Cincinnati Re (3 ) (1 ) — Total $ (119 ) $ (168 ) $ (184 ) Amortization of deferred policy acquisition costs: Commercial lines insurance $ 590 $ 570 $ 552 Personal lines insurance 225 209 210 Excess and surplus lines insurance 35 31 28 Cincinnati Re 17 10 2 Total $ 867 $ 820 $ 792 Paid loss and loss expenses: Commercial lines insurance $ 1,866 $ 1,675 $ 1,575 Personal lines insurance 898 771 731 Excess and surplus lines insurance 61 55 43 Cincinnati Re 18 2 — Total $ 2,843 $ 2,503 $ 2,349 Net written premiums: Commercial lines insurance $ 3,202 $ 3,122 $ 3,025 Personal lines insurance 1,294 1,198 1,128 Excess and surplus lines insurance 219 189 175 Cincinnati Re 125 71 33 Total $ 4,840 $ 4,580 $ 4,361

Summary of Significant Accoun34

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Nature of Operations	Nature of Operations Cincinnati Financial Corporation (CFC) operates through our insurance group and two complementary subsidiary companies. The Cincinnati Insurance Company leads our insurance group that also includes two subsidiaries: The Cincinnati Casualty Company and The Cincinnati Indemnity Company. This group markets a broad range of standard market commercial and personal policies. The group focuses on delivery of quality customer service to our select group of 1,702 independent insurance agencies with 2,256 reporting locations across 42 states. Other subsidiaries of The Cincinnati Insurance Company include The Cincinnati Life Insurance Company, which markets life and disability income insurance and fixed annuities, and The Cincinnati Specialty Underwriters Insurance Company, which offers excess and surplus lines property casualty insurance products. The Cincinnati Insurance Company also conducts the business of our reinsurance assumed operations, Cincinnati Re SM . The two CFC complementary subsidiaries are CSU Producer Resources Inc., which provides insurance brokerage services to our independent agencies so their clients can access our excess and surplus lines insurance products, and CFC Investment Company, which offers commercial leasing and financing services to our agents, their clients and other customers.
Basis of Presentation	Basis of Presentation Our consolidated financial statements include the accounts of the parent and its wholly owned subsidiaries and are presented in conformity with accounting principles generally accepted in the United States of America (GAAP). All intercompany balances and transactions have been eliminated in consolidation. The preparation of the consolidated financial statements in conformity with GAAP requires us to make estimates and assumptions that affect amounts reported in the consolidated financial statements and accompanying notes. Our actual results could differ from those estimates.
Investments	Investments Our portfolio investments are primarily in publicly traded fixed-maturity and equity security investments. Fixed-maturity investments (taxable bonds, tax-exempt bonds, redeemable preferred equities and commercial mortgage- backed securities) and equity investments (common and nonredeemable preferred equities) are classified as available for sale and recorded at fair value in the consolidated financial statements. The number of fixed-maturity securities with fair value below 100 percent of amortized cost can be expected to fluctuate as interest rates rise or fall. Because of our strong capital and long-term investment horizon, our general intent is to hold fixed-maturity investments until maturity, regardless of short-term fluctuations in fair values. Impairment charges for fixed maturities are recorded for other-than-temporary declines in value if fair value is below amortized cost and, in the asset impairment committee’s judgment, the fair value is not expected to be recouped within a designated recovery period. Our invested asset impairment policy also states that fixed maturities below their amortized cost that the company (1) intends to sell or (2) more likely than not will be required to sell before recovery of their amortized cost basis are deemed to be other-than-temporarily impaired (OTTI). The amortized cost of any such securities is reduced to fair value as the new cost basis, and a realized loss is recorded in the period in which it is recognized. When these two criteria are not met, and the company believes that full collection of interest and/or principal is not likely, we determine the net present value of future cash flows by using the effective interest rate implicit in the security at the date of acquisition as the discount rate and compare that amount with the amortized cost and fair value of the security. The difference between the net present value of the expected future cash flows and amortized cost of the security is considered a credit loss and recognized as a realized loss in the period in which it occurred. The difference between the fair value and the net present value of the cash flows of the security, the noncredit loss, is recognized in other comprehensive income as an unrealized loss. We had no fixed-maturity securities with a noncredit loss for the years ended 2017 , 2016 and 2015 . When determining OTTI charges for our equity portfolio, our invested asset impairment policy considers qualitative and quantitative factors, including facts and circumstances specific to individual securities; asset classes; the financial condition of the issuer; changes in dividend payment; the length of time fair value had been less than cost; the severity of the decline in fair value below cost; the volatility of the security; and our ability and intent to hold each position until its forecasted recovery. We include the noncredit portion of fixed-maturity OTTI charges and all other unrealized gains and losses on investments, net of taxes, in shareholders’ equity as accumulated other comprehensive income (AOCI). Realized gains and losses on investments are recognized in net income based on the trade date accounting method. Included within our other invested assets were $31 million and $31 million of life policy loans, $35 million and $23 million of private equity investments and $37 million and $27 million of real estate through direct property ownership and development projects in the United States at December 31, 2017 and 2016, respectively. Life policy loans are carried at the receivable value. The private equity investments provide their financial statements to us and generally report investments on their balance sheets at fair value. We use the equity method of accounting for private equity and real estate development investments. Investment income, net of expenses, consists mainly of interest and dividends. We record interest on an accrual basis and record dividends at the ex-dividend date. We amortize premiums and discounts on fixed-maturity securities using the effective interest method over the expected life of the security.
Fair Value Disclosures	Fair Value Disclosures Fair value is defined as the exit price or the amount that would be (1) received to sell an asset or (2) paid to transfer a liability in an orderly transaction between marketplace participants at the measurement date. When determining an exit price, we rely upon observable market data whenever possible. We primarily base fair value for investments in equity and fixed-maturity securities (including redeemable preferred stock and assets held in separate accounts) on quoted market prices or on prices from the company’s nationally recognized pricing vendor, an outside resource that supplies global securities pricing, dividend, corporate action and descriptive information to support fund pricing, securities operations, research and portfolio management. The company obtains and reviews the pricing service’s valuation methodologies and related inputs and validates these prices by replicating a sample across each asset class using a discounted cash flow model. When a price is not available from these sources, as in the case of securities that are not publicly traded, we determine the fair value using various inputs including quotes from independent brokers. The fair value of investments not priced by the company’s nationally recognized pricing vendor is less than 1 percent of the fair value of our total investment portfolio. For the purpose of ASC 825 disclosure, we estimate the fair value of our long-term senior notes on market pricing of similar debt instruments that are actively trading. We estimate the fair value of our note payable on the year-end outstanding balance because it is short term and tied to a variable interest rate. We estimate the fair value of liabilities for investment contracts and annuities using discounted cash flow calculations across a wide range of economic interest rate scenarios with a provision for our nonperformance risk. We estimate the fair value for policyholder loans on insurance contracts using a discounted cash flow model. Determination of fair value for structured settlements assumes the discount rates used to calculate the present value of expected payments are the risk-free spot rates plus an A3 rated bond spread for financial issuers at December 31, 2017 , to account for nonperformance risk. See Note 3, Fair Value Measurements, for further details.
Cash And Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents are highly liquid instruments that include liquid debt instruments with original maturities of less than three months. These are carried at cost, which approximates fair value.
Property Casualty Insurance	Property Casualty Insurance The consolidated property casualty companies actively write property casualty insurance through independent agencies in 42 states. Our 10 largest states generated 59.7 percent and 61.4 percent of total earned premiums in 2017 and 2016 , respectively. Ohio, our largest state, accounted for 16.2 percent and 16.8 percent of total earned premiums in 2017 and 2016 , respectively. Illinois, Georgia, Indiana, North Carolina, Pennsylvania and Michigan each accounted for between 5 percent and 7 percent of total earned premiums in 2017 . Our largest single agency relationship accounted for approximately 0.8 percent of our total property casualty earned premiums in 2017 . No aggregate agency relationship locations under a single ownership structure accounted for more than 4 percent of our total property casualty earned premiums in 2017 . We record revenues for installment charges as fee revenues in the consolidated statements of income. Property casualty written premiums are deferred and recorded as earned premiums on a pro rata basis over the terms of the policies. We record as unearned premiums the portion of written premiums that applies to unexpired policy terms. Expenses associated with successfully acquiring insurance policies – commissions, premium taxes and underwriting costs – are deferred and amortized over the terms of the policies. We assess recoverability of deferred acquisition costs at a level consistent with the way we acquire, service and manage insurance policies and measure profitability. We analyze our acquisition cost assumptions to reflect actual experience, and we evaluate potential premium deficiencies. Certain property casualty policies are not entered into policy underwriting systems as of the effective date of coverage. An estimate is recorded for these unprocessed written premiums. A large majority of the estimate is unearned and has no material impact on earned premiums. Premiums receivable are reviewed for impairment on a quarterly basis. We maintain an allowance for uncollectible premiums. We establish reserves to cover the expected cost of claims, losses and expenses related to investigating, processing and resolving claims. Although the appropriate amount of reserves is inherently uncertain, we base our decisions on past experience and current facts. Reserves are based on claims reported prior to the end of the year and estimates of unreported claims. We regularly review and update reserves using the most current information available. Any resulting adjustments are reflected in current calendar year insurance losses and policyholder benefits. We estimate that we may recover some of our costs through salvage and subrogation.
Policyholder Dividends	Policyholder Dividends Certain workers’ compensation policies include the possibility of a policyholder earning a return of a portion of premium in the form of a policyholder dividend. The dividend generally is calculated by determining the profitability of a policy year along with the associated premium. We reserve for all probable future policyholder dividend payments. We record policyholder dividends as other underwriting expenses.
Life Insurance	Life Insurance We offer several types of life insurance and disability income insurance, and we account for each according to the duration of the contract. Short-duration life and health contracts are written to cover claims that arise during a short, fixed term of coverage. We generally have the right to change the amount of premium charged or cancel the coverage at the end of each contract term. We record premiums for short-duration life and health contracts similarly to property casualty contracts. Long-duration contracts are written to provide coverage for an extended period of time. Traditional long-duration contracts require policyholders to pay scheduled gross premiums, generally not less frequently than annually, over the term of the coverage. Premiums for these contracts, such as whole life insurance and disability income insurance, are recognized as revenue when due. Some traditional long-duration contracts, such as ten-pay whole life insurance, have premium payment periods shorter than the period over which coverage is provided. For these contracts, the excess of premium over the amount required to pay expenses and benefits is recognized over the term of the coverage rather than over the premium payment period. We establish a liability for traditional long-duration contracts as we receive premiums. The amount of this liability is the present value of future expenses and benefits less the present value of future net premiums. Net premium is the portion of gross premium required to provide for all expenses and benefits. We estimate future expenses and benefits and net premium using assumptions for expected expenses, mortality, morbidity, withdrawal rates and investment income. We include a provision for deviation, meaning we allow for some uncertainty in making our assumptions. We establish our assumptions when the contract is issued, and we generally maintain those assumptions for the life of the contract. We use both our own experience and industry experience, adjusted for historical trends, in arriving at our assumptions for expected mortality, morbidity and withdrawal rates. We use our own experience and historical trends for setting our assumption for expected expenses. We base our assumption for expected investment income on our own experience, adjusted for current economic conditions. We capitalize acquisition costs for traditional long-duration contracts. We charge these capitalized costs associated with successfully acquiring traditional long-duration contract insurance policies in proportion to premium revenue recognized. We use the same assumptions used in establishing the liability for the contract. We update our acquisition cost assumptions periodically to reflect actual experience, and we evaluate our deferred acquisition costs for recoverability. Universal life contracts are long-duration contracts for which contractual provisions are not fixed, unlike whole life insurance. Universal life contracts allow policyholders to vary the amount of premium, within limits, without our consent. However, we may vary the mortality, expense charges and the interest crediting rate, within limits, used to accumulate policy values. We do not record universal life premiums as revenue. Instead we recognize as revenue the mortality charges, administration charges and surrender charges when received. Some of our universal life contracts assess administration charges in the early years of the contract that are compensation for services we will provide in the later years of the contract. These administration charges are deferred and are recognized over the period when we provide those future services. We maintain a policy reserve liability equal to the policyholder account value. There is no provision for adverse deviation. Some of our universal life policies contain no-lapse guarantee provisions. For these policies, we establish a reserve in addition to the account balance, based on expected no-lapse guarantee benefits and expected policy assessments. We capitalize acquisition costs associated with successfully acquiring universal life long-duration contracts. We charge these capitalized costs to expenses over the term of coverage of the contract in accordance with the recognition of gross profit from the contract. When we charge deferred policy acquisition costs to expenses, we use assumptions based on our best estimates of long-term experience. We review and modify these assumptions on a regular basis.
Separate Accounts	Separate Accounts We have issued universal life contracts with guaranteed minimum returns, referred to as bank-owned life insurance contracts (BOLIs). A BOLI is designed so the bank is the policy owner and the policy beneficiary. We legally segregate and record as separate accounts the assets and liabilities for some of our BOLIs, based on the specific contract provisions. We guarantee minimum investment returns, account values and death benefits for our separate account BOLIs. Our other BOLIs are general account products. We carry the assets of separate account BOLIs at fair value. The liabilities on separate account BOLIs primarily are the contract holders’ claims to the related assets and are carried at an amount equal to the contract holders’ account value. At December 31, 2017 , the current fair value of the BOLI invested assets and cash exceeded the current fair value of the contract holders’ account value by approximately $29 million . If the BOLI projected fair value were to fall below the value we guaranteed, a liability would be established with a corresponding charge to the company’s earnings. Generally, investment income and realized investment gains and losses of the separate accounts accrue directly to the contract holder, and we do not include them in the consolidated statements of income. Revenues and expenses related to separate accounts consist of contractual fees and mortality, surrender and expense risk charges. Also, each separate account BOLI includes a negotiated capital gain and loss sharing arrangement between the company and the bank. A percentage of each separate account’s realized capital gain and loss representing contract fees and assessments accrues to us and is transferred from the separate account to our general account and is recognized as revenue or expense. We record as revenues separate account investment management fees in fee revenues of the consolidated statements of income.
Reinsurance	Reinsurance The Cincinnati Insurance Company offers reinsurance assumed for casualty and specialty (predominantly domestic exposure) and property (worldwide exposure). Treaties are written on a pro rata and excess of loss basis. We also continue to assume risk with limited exposure as a reinsurer for involuntary state pools. Written premium is recorded, net of contract specific retrocessions, on an ultimate estimate basis and earned on a pro rata basis over the coverage period of the treaty. Expenses are recorded as per contract terms and deferred over the earning period of the premium. We establish known loss reserves when reported. We establish reserves for losses in excess of reported activity in the form of IBNR. Reserves are established using actuarial analysis which includes models and methods traditionally used for the types of exposures written. We establish reserves for event specific occurrences using modeling data and company specific data when available. We enter into other reinsurance transactions to reduce risk and uncertainty by buying property casualty reinsurance and retrocessional reinsurance as well as life reinsurance. Reinsurance and retrocessional reinsurance contracts do not relieve us from our obligation to policyholders, but rather help protect our financial strength to perform that duty. All of these ceded reinsurance contracts transfer the economic risk of loss. Premiums that we cede are deferred and recorded as earned premiums on a pro rata basis over the terms of the contracts. We estimate loss amounts recoverable from our reinsurers based on the reinsurance policy terms. Historically, our claims with reinsurers have been paid. We establish an insignificant allowance for uncollectible reinsurance.
Income Taxes	Income Taxes We calculate deferred income tax liabilities and assets using tax rates in effect when temporary differences in the consolidated financial statement income and taxable income are expected to reverse. We recognize deferred income taxes for numerous temporary differences between our taxable income and consolidated financial statement income and other changes in shareholders’ equity. Such temporary differences relate primarily to unrealized gains and losses on investments and differences in the recognition of deferred acquisition costs, unearned premiums, insurance reserves and basis differences in the carrying value of investments held. We charge deferred income taxes associated with balances that impact other comprehensive income, such as unrealized appreciation and depreciation of investments (except the amount related to the effect of income tax rate changes), to shareholders’ equity in accumulated other comprehensive income (AOCI). We charge deferred taxes associated with other differences to income. Although no Internal Revenue Service (IRS) penalties currently are accrued, if incurred, they would be recognized as a component of income tax expense.
Earnings per Share	Earnings per Share Net income per common share is based on the weighted average number of common shares outstanding during each of the respective years. We calculate net income per common share (diluted) assuming the exercise or conversion of share‑based awards using the treasury stock method.
Land, Building And Equipment	Land, Building and Equipment We record land at cost, and record building and equipment at cost less accumulated depreciation. Equipment held under capital leases also is classified as property and equipment with the related lease obligations recorded as liabilities. We capitalize and amortize costs for internally developed computer software during the application development stage. These costs generally consist of external consulting, internal payroll and payroll-related costs. Our depreciation is based on estimated useful lives (ranging from three years to 39.5 years) using straight-line and accelerated methods. Depreciation expense was $28 million for 2017 , $30 million for 2016 and $36 million for 2015 . We review our accumulated depreciation for our building, equipment and software assets and write off fully depreciated assets for obsolesce and nonuse. We monitor land, building and equipment and software assets for potential impairments. Potential impairments may include a significant decrease in the fair values of the assets, considerable cost overruns on projects, a change in legal factors or business climate or other factors that indicate that the carrying amount may not be recoverable or useful. There were no recorded land, building and equipment impairments for 2017 , 2016 or 2015 .
Finance Receivables	Finance Receivables Our leasing subsidiary provides auto and equipment direct financing (leases and loans) to commercial and individual clients. We generally transfer ownership of the property to the client as the terms of the leases expire. Our lease contracts contain bargain purchase options. We account for these leases and loans as direct financing-type leases. We capitalize and amortize lease or loan origination costs over the life of the financing, using the effective interest method. These costs may include, but are not limited to finder fees, broker fees, filing fees and the cost of credit reports. We record income as other revenues over the financing term using the effective interest method in the consolidated statements of income. Finance receivables are reviewed for impairment and are insignificant to our consolidated financial position, results of operations and cash flows.
Employee Benefit Pension Plan	Employee Benefit Pension Plan We sponsor a defined benefit pension plan that was modified during 2008. We closed entry into the pension plan, and only participants 40 years of age or older could elect to remain in the plan. Our pension expense is based on certain actuarial assumptions and also is composed of several components that are determined using the projected unit credit actuarial cost method. Refer to Note 13, Employee Retirement Benefits, for more information about our defined benefit pension plan.
Stock-Based Compensation	Share-Based Compensation We grant qualified and nonqualified share-based compensation under authorized plans. The stock options generally vest on a graded scale over three years following the date of grant and are exercisable over 10 -year periods. We grant service-based restricted stock units that cliff vest three years after the date of grant as well as service-based restricted stock units that vest ratably over the three -year vesting term. We also grant performance-based restricted stock units that vest if certain market conditions are attained. In 2017 , the CFC compensation committee approved share-based awards including incentive stock options, nonqualified stock options, service-based restricted and performance-based restricted stock units. See Note 17, Share-Based Associate Compensation Plans, for further details.
Subsequent Events	Subsequent Events There were no subsequent events requiring adjustment to the consolidated financial statements or disclosure.
Adopted Accounting Updates	Adopted Accounting Updates ASU 2016-07, Investments - Equity Method and Joint Ventures (Topic 323): Simplifying the Transition to the Equity Method of Accounting In March 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2016-07, Equity Method and Joint Ventures (Topic 323): Simplifying the Transition to the Equity Method of Accounting. ASU 2016-07 eliminates the requirement to retroactively adjust an investment, results of operations, and retained earnings once an investment qualifies for use of the equity method. It requires the equity method investor to add the cost of acquiring the additional interest in the investee to the current basis of the investor's previously held interest and adopt the equity method of accounting as of the date the investment becomes qualified for equity method accounting without retroactive adjustment. The effective date of ASU 2016-07 was for interim and annual reporting periods beginning after December 15, 2016, and was applied prospectively. The company adopted this ASU effective January 1, 2017, and it did not have a material impact on our company's consolidated financial position, cash flows or results of operations. ASU 2016-09, Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting In March 2016, the FASB issued ASU 2016-09, Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting. ASU 2016-09 simplifies several aspects of the accounting for share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities, and classification on the statement of cash flows. The effective date of ASU 2016-09 was for interim and annual reporting periods beginning after December 15, 2016. The recognition and classification of the excess tax benefit provisions were applied prospectively in the results of operations and statement of cash flows. This adoption resulted in excess tax benefits of $7 million for the year ended December 31, 2017, which reduced our current provision for income taxes in our results of operations. The statutory tax withholding classification, which are cash payments made to taxing authorities for shares withheld, were applied retrospectively and reclassified the statutory tax withholding requirements in the statement of cash flows from Other liabilities in operating activities to Other in financing activities. This statutory tax withholding reclassification resulted in $13 million , $12 million and $11 million being included in financing activities for the years ended December 31, 2017, 2016 and 2015, respectively. There were no cumulative effect adjustments upon adoption of this ASU. ASU 2018-02, Income Statement—Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income In February 2018, the FASB issued ASU 2018-02, Income Statement - Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income (“AOCI”). ASU 2018-02 eliminates the stranded tax effects within AOCI resulting from the application of current GAAP in response to the change in the U.S. corporate income tax rate from 35 percent to 21 percent as part of the Tax Act. Stranded tax effects unrelated to the Tax Act are released from AOCI using the security-by-security approach. The effective date of ASU 2018-02 is for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years with early adoption permitted for public entities for which financial statements had not yet been issued. The company elected to early adopt ASU 2018-02 effective for the year ended December 31, 2017, and applied the provisions retrospectively within our consolidated balance sheets and statements of shareholders' equity. This adoption resulted in a one-time reclassification of the effect of remeasuring deferred tax liabilities related to items, primarily unrealized gains and losses on investments, within AOCI to retained earnings resulting from the change in the U.S. corporate income tax rate. This reclassification resulted in an increase to AOCI and a decrease to retained earnings in the amount of $492 million for the year ended December 31, 2017, with no net impact to total shareholders' equity.
Pending Accounting Updates	Pending Accounting Updates ASU 2014-09 Revenue from Contracts with Customers In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers . ASU 2014-09 requires an entity to recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods and services. Insurance contracts do not fall within the scope of this ASU. The effective date of ASU 2014-09 is for interim and annual reporting periods beginning after December 15, 2017. The ASU has not yet been adopted and will not have a material impact on our company’s consolidated financial position, cash flows or results of operations. ASU 2016-01, Financial Instruments - Overall (Subtopic 825-10) - Recognition and Measurement of Financial Assets and Financial Liabilities In January 2016, the FASB issued ASU 2016-01, Financial Instruments - Overall (Subtopic 825-10) - Recognition and Measurement of Financial Assets and Financial Liabilities. ASU 2016-01 revises the accounting related to the classification and measurement of investments in equity securities and the presentation of certain fair value changes for financial liabilities measured at fair value. Our results of operations will be impacted as changes in fair value of equity securities will be reported in net income instead of other comprehensive income. The effective date of ASU 2016-01 is for interim and annual reporting periods beginning after December 15, 2017, and will be applied prospectively. The ASU has not yet been adopted. Upon adoption of this ASU on January 1, 2018, $2.503 billion of after-tax unrealized gains on equity securities will be reclassified from AOCI to retained earnings. ASU 2016-02, Leases (Topic 842) In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842). The main provision of ASU 2016-02 requires the recognition of lease assets and lease liabilities by lessees for those leases classified as operating leases under previous GAAP. The effective date of ASU 2016-02 is for interim and annual reporting periods beginning after December 15, 2018. The ASU has not yet been adopted; however, it is not expected to have a material impact on our company's consolidated financial position, cash flows or results of operations. ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments . ASU 2016-13 amends previous guidance on the impairment of financial instruments by adding an impairment model that allows an entity to recognize expected credit losses as an allowance rather than impairing as they are incurred. The new guidance is intended to reduce complexity of credit impairment models and result in a more timely recognition of expected credit losses. The effective date of ASU 2016-13 is for interim and annual reporting periods beginning after December 15, 2019. The ASU has not yet been adopted. Management is currently evaluating the impact on our company’s consolidated financial position, cash flows and results of operations. ASU 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments . ASU 2016-15 addresses eight specific cash flow issues with the objective of reducing the existing diversity in practice. The effective date of ASU 2016-15 is for interim and annual reporting periods beginning after December 15, 2017. The ASU has not yet been adopted; however, it will not have a material impact on our company's consolidated financial position, cash flows or results of operations. ASU 2017-07, Compensation - Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost In March 2017, the FASB issued ASU 2017-07, Compensation - Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Postretirement Benefit Costs . ASU 2017-07 provides guidance on how to present the components of net periodic benefit costs in the income statement for pension plans and other post-retirement benefit plans. The effective date of ASU 2017-07 is for interim and annual reporting periods beginning after December 15, 2017. The ASU has not yet been adopted; however, it will not have a material impact on our company's consolidated financial position, cash flows or results of operations. ASU 2017-08, Receivables - Nonrefundable Fees and Other Costs (Subtopic 310-20): Premium Amortization on Purchased Callable Debt Securities In March 2017, the FASB issued ASU 2017-08, Receivables - Nonrefundable Fees and Other Costs (Subtopic 310-20): Premium Amortization on Purchased Callable Debt Securities. ASU 2017-08 amends guidance on the amortization period of premiums on certain purchased callable debt securities. The amendments shorten the amortization period of premiums on certain purchased callable debt securities to the earliest call date. The amendments should be applied on a modified retrospective basis through a cumulative-effect adjustment to beginning retained earnings. The effective date of ASU 2017-08 is for interim and annual reporting periods beginning after December 15, 2018. The ASU has not yet been adopted; however, it will not have a material impact on our company's consolidated financial position, cash flows or results of operations. ASU 2017-09, Compensation - Stock Compensation (Topic 718): Scope of Modification Accounting In May 2017, the FASB issued ASU 2017-09, Compensation - Stock Compensation (Topic 718): Scope of Modification Accounting. ASU 2017-09 clarifies when to account for a change to the terms or conditions of a share-based payment award as a modification. Under the new guidance, modification accounting is required only if the fair value, the vesting conditions, or the classification of the award (as equity or liability) changes as a result of the change in terms or conditions. The amendment should be applied on a prospective basis. The effective date of ASU 2017-09 is for interim and annual reporting periods, beginning after December 15, 2017. The ASU has not yet been adopted; however, it will not have a material impact on our company's consolidated financial position, cash flows or results of operations.

Investments (Tables)

Investments (Tables)	12 Months Ended
	Dec. 31, 2017
Investments [Abstract]
Analysis Of Cost Or Amortized Cost, Gross Unrealized Gains And Losses And Fair Value for Investments	The following table provides cost or amortized cost, gross unrealized gains, gross unrealized losses and fair value for our fixed-maturity and equity securities: (Dollars in millions) Cost or amortized cost Gross unrealized Fair At December 31, 2017 gains losses Fixed-maturity securities: Corporate $ 5,420 $ 246 $ 13 $ 5,653 States, municipalities and political subdivisions 4,316 155 6 4,465 Commercial mortgage-backed 280 7 1 286 Government-sponsored enterprises 257 1 4 254 United States government 31 — — 31 Foreign government 10 — — 10 Subtotal 10,314 409 24 10,699 Equity securities: Common equities 2,918 3,135 14 6,039 Nonredeemable preferred equities 176 34 — 210 Subtotal 3,094 3,169 14 6,249 Total $ 13,408 $ 3,578 $ 38 $ 16,948 At December 31, 2016 Fixed-maturity securities: Corporate $ 5,555 $ 252 $ 26 $ 5,781 States, municipalities and political subdivisions 3,770 100 42 3,828 Commercial mortgage-backed 282 7 2 287 Government-sponsored enterprises 167 — 3 164 United States government 10 — — 10 Foreign government 10 — — 10 Convertibles and bonds with warrants attached 5 — — 5 Subtotal 9,799 359 73 10,085 Equity securities: Common equities 2,812 2,320 9 5,123 Nonredeemable preferred equities 183 28 — 211 Subtotal 2,995 2,348 9 5,334 Total $ 12,794 $ 2,707 $ 82 $ 15,419
Fair Values And Unrealized Losses by Investment Category And By The Duration Of The Securities' Continuous Unrealized Loss Position	The table below provides fair values and unrealized losses by investment category and by the duration of the securities’ continuous unrealized loss positions: (Dollars in millions) Less than 12 months 12 months or more Total At December 31, 2017 Fair value Unrealized losses Fair value Unrealized losses Fair value Unrealized losses Fixed-maturity securities: Corporate $ 330 $ 4 $ 252 $ 9 $ 582 $ 13 States, municipalities and political subdivisions 88 1 264 5 352 6 Commercial mortgage-backed 33 — 36 1 69 1 Government-sponsored enterprises 96 1 124 3 220 4 Foreign government 10 — — — 10 — United States government 23 — 6 — 29 — Subtotal 580 6 682 18 1,262 24 Equity securities: Common equities 229 14 — — 229 14 Subtotal 229 14 — — 229 14 Total $ 809 $ 20 $ 682 $ 18 $ 1,491 $ 38 At December 31, 2016 Fixed-maturity securities: Corporate $ 733 $ 15 $ 189 $ 11 $ 922 $ 26 States, municipalities and political subdivisions 989 42 — — 989 42 Commercial mortgage-backed 89 2 2 — 91 2 Government-sponsored enterprises 155 3 — — 155 3 United States government 6 — — — 6 — Subtotal 1,972 62 191 11 2,163 73 Equity securities: Common equities 103 9 — — 103 9 Nonredeemable preferred equities 4 — — — 4 — Subtotal 107 9 — — 107 9 Total $ 2,079 $ 71 $ 191 $ 11 $ 2,270 $ 82
Contractual Maturity Dates For Fixed-Maturity And Short-Term Investments	Contractual maturity dates for fixed-maturity investments were: (Dollars in millions) Amortized cost Fair value % of fair value At December 31, 2017 Maturity dates: Due in one year or less $ 511 $ 519 4.9 % Due after one year through five years 2,736 2,839 26.5 Due after five years through ten years 3,921 4,058 37.9 Due after ten years 3,146 3,283 30.7 Total $ 10,314 $ 10,699 100.0 %
Investment Income, Realized Investment Gains And Losses And Change In Unrealized Investment Gains And Losses	The following table provides investment income and realized investment gains and losses: (Dollars in millions) Years ended December 31, 2017 2016 2015 Investment income: Interest $ 445 $ 440 $ 428 Dividends 170 161 150 Other 4 3 3 Total 619 604 581 Less investment expenses 10 9 9 Total $ 609 $ 595 $ 572 Realized investment gains and losses: Fixed maturities: Gross realized gains $ 25 $ 26 $ 18 Gross realized losses — (1 ) — Other-than-temporary impairments (6 ) (2 ) (18 ) Equity securities: Gross realized gains 195 152 129 Gross realized losses (72 ) (53 ) (26 ) Other-than-temporary impairments (3 ) — (34 ) Other 9 2 1 Total $ 148 $ 124 $ 70

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value Hierarchy for Assets Measured at Fair Value on a Recurring Basis	The following tables illustrate the fair value hierarchy for those assets measured at fair value on a recurring basis at December 31, 2017 and 2016 . We do not have any liabilities carried at fair value. There were no transfers between Level 1 and Level 2. (Dollars in millions) Quoted prices in active markets for Significant unobservable At December 31, 2017 Significant other observable inputs (Level 2) Total Fixed maturities, available for sale: Corporate $ — $ 5,652 $ 1 $ 5,653 States, municipalities and political subdivisions — 4,460 5 4,465 Commercial mortgage-backed — 286 — 286 Government-sponsored enterprises — 254 — 254 United States Government 31 — — 31 Foreign government — 10 — 10 Subtotal 31 10,662 6 10,699 Common equities, available for sale 6,039 — — 6,039 Nonredeemable preferred equities, available for sale — 210 — 210 Separate accounts taxable fixed maturities — 795 — 795 Top Hat savings plan mutual funds and common equity (included in Other assets) 31 — — 31 Total $ 6,101 $ 11,667 $ 6 $ 17,774 At December 31, 2016 Fixed maturities, available for sale: Corporate $ — $ 5,703 $ 78 $ 5,781 States, municipalities and political subdivisions — 3,828 — 3,828 Commercial mortgage-backed — 287 — 287 Government-sponsored enterprises — 164 — 164 United States Government 10 — — 10 Foreign government — 10 — 10 Convertibles and bonds with warrants attached — 5 — 5 Subtotal 10 9,997 78 10,085 Common equities, available for sale 5,123 — — 5,123 Nonredeemable preferred equities, available for sale — 211 — 211 Separate accounts taxable fixed maturities — 750 — 750 Top Hat savings plan mutual funds and common equity (included in Other assets) 24 — — 24 Total $ 5,157 $ 10,958 $ 78 $ 16,193
Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)	The following table provides the change in Level 3 assets during 2017 and 2016 : (Dollars in millions) Asset fair value measurements using significant unobservable input Corporate fixed maturities Separate accounts taxable fixed maturities States, municipalities and political subdivisions fixed maturities Nonredeemable preferred equities Total Beginning balance, January 1, 2017 $ 78 $ — $ — $ — $ 78 Total gains or losses (realized/unrealized): Included in net income — — — — — Included in other comprehensive income — — — — — Purchases — — 5 — 5 Sales — — — — — Transfers into Level 3 — — — — — Transfers out of Level 3 (77 ) — — — (77 ) Ending balance, December 31, 2017 $ 1 $ — $ 5 $ — $ 6 Beginning balance, January 1, 2016 $ 51 $ 1 $ — $ 3 $ 55 Total gains or losses (realized/unrealized): Included in net income — — — — — Included in other comprehensive income — — — (1 ) (1 ) Purchases 57 — — — 57 Sales (1 ) — — (2 ) (3 ) Transfers into Level 3 13 — — — 13 Transfers out of Level 3 (42 ) (1 ) — — (43 ) Ending balance, December 31, 2016 $ 78 $ — $ — $ — $ 78
Fair Value of Life Policy Loans	The following table shows the fair value of our life policy loans, included in other invested assets: (Dollars in millions) Quoted prices in active markets for identical assets (Level 1) Significant other observable inputs (Level 2) Significant unobservable inputs (Level 3) Total At December 31, 2017 Life policy loans $ — $ — $ 41 $ 41 At December 31, 2016 Life policy loans $ — $ — $ 40 $ 40
Debt
Fair Values of Deferred Annuities, Structured Settlements and Other Items	The following table shows fair values of our note payable and long-term debt: (Dollars in millions) Quoted prices in active markets for Significant other Significant unobservable inputs (Level 3) Total At December 31, 2017 Note payable $ — $ 24 $ — $ 24 6.900% senior debentures, due 2028 — 34 — 34 6.920% senior debentures, due 2028 — 505 — 505 6.125% senior notes, due 2034 — 477 — 477 Total $ — $ 1,040 $ — $ 1,040 At December 31, 2016 Note payable $ — $ 20 $ — $ 20 6.900% senior debentures, due 2028 — 33 — 33 6.920% senior debentures, due 2028 — 488 — 488 6.125% senior notes, due 2034 — 435 — 435 Total $ — $ 976 $ — $ 976
Deferred Annuities and Structured Settlements
Fair Values of Deferred Annuities, Structured Settlements and Other Items	The following table shows fair value of our deferred annuities and structured settlements included in life policy and investment contract reserves: (Dollars in millions) Quoted prices in active markets for identical assets (Level 1) Significant other observable inputs (Level 2) Significant unobservable inputs (Level 3) Total At December 31, 2017 Deferred annuities $ — $ — $ 834 $ 834 Structured settlements — 210 — 210 Total $ — $ 210 $ 834 $ 1,044 At December 31, 2016 Deferred annuities $ — $ — $ 839 $ 839 Structured settlements — 206 — 206 Total $ — $ 206 $ 839 $ 1,045

Property Casualty Loss And Lo37

Property Casualty Loss And Loss Expenses (Tables)	12 Months Ended
	Dec. 31, 2017
Insurance [Abstract]
Consolidated Property Casualty Loss And Loss Expense Reserves	This table summarizes activity for our consolidated property casualty loss and loss expense reserves: (Dollars in millions) Years ended December 31, 2017 2016 2015 Gross loss and loss expense reserves, January 1 $ 5,035 $ 4,660 $ 4,438 Less reinsurance recoverable 298 281 282 Net loss and loss expense reserves, January 1 4,737 4,379 4,156 Net incurred loss and loss expenses related to: Current accident year 3,257 3,029 2,756 Prior accident years (119 ) (168 ) (184 ) Total incurred 3,138 2,861 2,572 Net paid loss and loss expenses related to: Current accident year 1,404 1,260 1,152 Prior accident years 1,439 1,243 1,197 Total paid 2,843 2,503 2,349 Net loss and loss expense reserves, December 31 5,032 4,737 4,379 Plus reinsurance recoverable 187 298 281 Gross loss and loss expense reserves, December 31 $ 5,219 $ 5,035 $ 4,660
Reconciliation of Property casualty Incurred Losses and ALAE and Paid Losses and ALAE Development Information	The following table provides a reconciliation of the property casualty incurred losses and allocated loss adjustment expenses (ALAE) development and paid losses and ALAE development information at December 31, 2017. (Dollars in millions) Cumulative incurred losses and ALAE as reported within the triangles, net of reinsurance Cumulative paid losses and ALAE as reported within the triangles, net of reinsurance Liabilities for loss and ALAE for accident years not presented in the triangles, net of reinsurance Total liabilities for loss and ALAE, net of reinsurance Reinsurance recoverable on unpaid losses Total liabilities for gross loss and loss expense reserves Commercial casualty $ 4,434 $ 2,573 $ 83 $ 1,944 $ 43 $ 1,987 Workers' compensation 2,259 1,598 267 928 64 992 Commercial auto 1,955 1,380 16 591 4 595 Commercial property 2,353 2,095 12 270 7 277 Personal auto 1,774 1,503 5 276 31 307 Homeowner 1,466 1,358 3 111 3 114 Excess and surplus 441 195 94 340 3 343 Other lines 315 Total liabilities for loss and ALAE reserves 4,930 Unallocated loss adjustment expense reserves 289 Gross loss and loss expense reserves $ 5,219
Schedule of Incurred and Paid Losses and ALAE Development by Accident Year	The following table shows the excess and surplus lines incurred and paid losses and ALAE development by accident year. The table also shows the IBNR reserves plus expected development on reported losses and claim frequency: (Dollars in millions, reported claims in thousands) As of December 31, 2017 Incurred losses and ALAE, net of reinsurance Total of incurred Cumulative number of reported claims Years ended December 31, Accident 2011 2012 2013 2014 2015 2016 Year Unaudited 2017 2011 $ 48 $ 47 $ 44 $ 38 $ 36 $ 35 $ 35 $ 1 1 2012 67 56 49 40 37 36 1 1 2013 74 64 54 45 42 4 2 2014 95 82 75 64 16 2 2015 96 81 73 22 2 2016 93 87 34 2 2017 104 64 2 Total $ 441 Cumulative paid losses and ALAE, net of reinsurance 2011 $ 8 $ 14 $ 23 $ 27 $ 30 $ 32 $ 34 2012 9 15 19 25 29 31 2013 7 12 20 27 32 2014 9 17 27 37 2015 8 19 29 2016 10 21 2017 11 Total 195 All outstanding liabilities before 2011, net of reinsurance 94 Liabilities for loss and ALAE, net of reinsurance $ 340 The following table shows the homeowner incurred and paid losses and ALAE development by accident year. The table also shows the IBNR reserves plus expected development on reported losses and claim frequency: (Dollars in millions, reported claims in thousands) As of December 31, 2017 Incurred losses and ALAE, net of reinsurance Total of incurred Cumulative number of reported claims Years ended December 31, Accident 2013 2014 2015 2016 Year Unaudited 2017 2013 $ 252 $ 246 $ 247 $ 247 $ 246 $ — 25 2014 297 283 286 285 1 26 2015 284 275 275 1 24 2016 315 304 3 23 2017 356 8 24 Total $ 1,466 Cumulative paid losses and ALAE, net of reinsurance 2013 $ 180 $ 236 $ 242 $ 244 $ 246 2014 224 273 281 283 2015 203 260 269 2016 208 283 2017 277 Total 1,358 All outstanding liabilities before 2013, net of reinsurance 3 Liabilities for loss and ALAE, net of reinsurance $ 111 The following table shows the personal auto incurred and paid losses and ALAE development by accident year. The table also shows the IBNR reserves plus expected development on reported losses and claim frequency: (Dollars in millions, reported claims in thousands) As of December 31, 2017 Incurred losses and ALAE, net of reinsurance Total of incurred Cumulative number of reported claims Years ended December 31, Accident 2013 2014 2015 2016 Year Unaudited 2017 2013 $ 280 $ 280 $ 293 $ 298 $ 298 $ — 96 2014 317 317 325 324 — 105 2015 343 356 356 — 108 2016 383 384 8 110 2017 412 55 102 Total $ 1,774 Cumulative paid losses and ALAE, net of reinsurance 2013 $ 190 $ 245 $ 272 $ 287 $ 293 2014 210 267 298 313 2015 229 292 325 2016 243 316 2017 256 Total 1,503 All outstanding liabilities before 2013 net of reinsurance 5 Liabilities for loss and ALAE, net of reinsurance $ 276 The following table shows the commercial property incurred and paid losses and ALAE development by accident year. The table also shows the IBNR reserves plus expected development on reported losses and claim frequency: (Dollars in millions, reported claims in thousands) As of December 31, 2017 Incurred losses and ALAE, net of reinsurance Total of incurred Cumulative number of reported claims Years ended December 31, Accident 2013 2014 2015 2016 Year Unaudited 2017 2013 $ 389 $ 359 $ 352 $ 356 $ 357 $ 1 14 2014 452 444 441 442 2 17 2015 454 414 416 2 17 2016 590 551 7 17 2017 587 24 16 Total $ 2,353 Cumulative paid losses and ALAE, net of reinsurance 2013 $ 227 $ 330 $ 344 $ 349 $ 352 2014 297 412 432 437 2015 279 388 407 2016 358 504 2017 395 Total 2,095 All outstanding liabilities before 2013, net of reinsurance 12 Liabilities for loss and ALAE, net of reinsurance $ 270 The following table shows the commercial auto incurred and paid losses and ALAE development by accident year. The table also shows the IBNR reserves plus expected development on reported losses and claim frequency: (Dollars in millions, reported claims in thousands) As of December 31, 2017 Incurred losses and ALAE, net of reinsurance Total of incurred Cumulative number of reported claims Years ended December 31, Accident 2013 2014 2015 2016 Year Unaudited 2017 2013 $ 292 $ 305 $ 315 $ 322 $ 322 $ 5 46 2014 333 346 351 358 8 51 2015 374 384 394 15 51 2016 417 430 36 53 2017 451 127 47 Total $ 1,955 Cumulative paid losses and ALAE, net of reinsurance 2013 $ 141 $ 199 $ 246 $ 285 $ 307 2014 159 223 273 310 2015 173 244 303 2016 184 273 2017 187 Total 1,380 All outstanding liabilities before 2013, net of reinsurance 16 Liabilities for loss and ALAE, net of reinsurance $ 591 The following table shows the commercial casualty incurred and paid losses and ALAE development by accident year. The table also shows the IBNR reserves plus expected development on reported losses and claim frequency: (Dollars in millions, reported claims in thousands) As of December 31, 2017 Incurred losses and ALAE, net of reinsurance Total of incurred but not reported liabilities plus expected development on reported losses Cumulative number of reported claims Years ended December 31, Accident 2008 2009 2010 2011 2012 2013 2014 2015 2016 Year Unaudited 2017 2008 $ 516 $ 458 $ 409 $ 387 $ 362 $ 359 $ 357 $ 357 $ 355 $ 366 $ 11 — 2009 484 409 412 360 370 365 357 357 353 10 20 2010 495 394 378 349 347 348 349 343 19 20 2011 466 404 377 377 375 380 366 17 19 2012 466 414 417 394 394 404 43 18 2013 448 443 431 416 413 64 19 2014 503 496 479 476 82 21 2015 533 526 529 170 20 2016 563 574 247 19 2017 610 381 15 Total $ 4,434 Cumulative paid losses and ALAE, net of reinsurance 2008 $ 31 $ 93 $ 158 $ 212 $ 262 $ 293 $ 315 $ 325 $ 331 $ 339 2009 27 75 151 213 267 295 310 322 328 2010 33 92 159 203 256 285 300 314 2011 27 93 149 227 266 298 315 2012 27 88 170 232 288 330 2013 35 90 159 232 286 2014 34 97 172 287 2015 38 108 200 2016 46 126 2017 48 Total 2,573 All outstanding liabilities before 2008, net of reinsurance 83 Liabilities for loss and ALAE, net of reinsurance $ 1,944 The following table shows the workers’ compensation incurred and paid losses and ALAE development by accident year. The table also shows the IBNR reserves plus expected development on reported losses and claim frequency: (Dollars in millions, reported claims in thousands) As of December 31, 2017 Incurred losses and ALAE, net of reinsurance Total of incurred Cumulative number of reported claims Years ended December 31, Accident 2008 2009 2010 2011 2012 2013 2014 2015 2016 Year Unaudited 2017 2008 $ 298 $ 305 $ 310 $ 302 $ 299 $ 299 $ 297 $ 296 $ 296 $ 293 $ 28 — 2009 307 278 263 238 238 235 234 234 232 18 27 2010 283 274 248 242 240 239 240 237 22 26 2011 284 251 246 242 239 236 231 22 24 2012 265 245 234 220 213 211 26 21 2013 264 246 221 212 208 28 20 2014 261 233 214 203 31 19 2015 246 220 208 60 17 2016 230 218 72 16 2017 218 89 13 Total $ 2,259 Cumulative paid losses and ALAE, net of reinsurance 2008 $ 72 $ 155 $ 195 $ 217 $ 233 $ 242 $ 247 $ 251 $ 254 $ 256 2009 65 132 163 179 188 193 198 201 202 2010 67 134 164 181 192 198 202 204 2011 65 131 161 177 186 190 192 2012 62 121 147 162 171 175 2013 61 119 144 157 164 2014 56 110 134 148 2015 47 93 115 2016 46 97 2017 45 Total 1,598 All outstanding liabilities before 2008, net of reinsurance 267 Liabilities for loss and ALAE, net of reinsurance $ 928
Schedule of Average Annual Percentage Payout of Incurred Claims	The following table shows the average annual percentage payout of incurred losses for the homeowner line of business: Average annual percentage payout of incurred losses by age, net of reinsurance (unaudited) Years 1 2 3 4 5 Average annual percentage payout 74.4% 21.3% 3.0% 0.7% 0.4% The following table shows the average annual percentage payout of incurred losses for the excess and surplus lines insurance segment. Excess and surplus lines consist mostly of commercial casualty and commercial property coverages. A majority of the incurred losses paid after year 2 are the result of commercial casualty losses. Average annual percentage payout of incurred losses by age, net of reinsurance (unaudited) Years 1 2 3 4 5 6 7 Average annual percentage payout 16.0% 14.1% 17.5% 14.7% 10.7% 7.2% 1.1% The following table shows the average annual percentage payout of incurred losses for the commercial property line of business: Average annual percentage payout of incurred losses by age, net of reinsurance (unaudited) Years 1 2 3 4 5 Average annual percentage payout 66.0% 26.9% 4.4% 1.1% 0.9% The following table shows the average annual percentage payout of incurred losses for the personal auto line of business. Personal auto includes both physical damage and liability losses. A majority of the incurred losses paid after year 2 are the result of liability losses. Average annual percentage payout of incurred losses by age, net of reinsurance (unaudited) Years 1 2 3 4 5 Average annual percentage payout 63.7% 18.1% 9.4% 4.8% 1.9% The following table shows the average annual percentage payout of incurred losses for the commercial auto line of business. Commercial auto includes both physical damage and liability losses. A majority of the incurred losses paid after year 2 are the result of liability losses. Average annual percentage payout of incurred losses by age, net of reinsurance (unaudited) Years 1 2 3 4 5 Average annual percentage payout 43.3% 18.7% 14.5% 11.2% 6.7% The following table shows the average annual percentage payout of incurred losses for the commercial casualty line of business: Average annual percentage payout of incurred losses by age, net of reinsurance (unaudited) Years 1 2 3 4 5 6 7 8 9 10 Average annual percentage payout 7.9% 14.9% 18.0% 17.7% 13.7% 8.8% 4.8% 3.5% 1.6% 1.8% The following table shows the average annual percentage payout of incurred losses for the workers’ compensation line of business: Average annual percentage payout of incurred losses by age, net of reinsurance (unaudited) Years 1 2 3 4 5 6 7 8 9 10 Average annual percentage payout 25.9% 26.9% 12.4% 7.0% 4.2% 2.4% 1.5% 1.4% 0.8% 0.5%

Life Policy And Investment Co38

Life Policy And Investment Contract Reserves (Tables)	12 Months Ended
	Dec. 31, 2017
Liability for Future Policy Benefits [Abstract]
Reserve In Addition To The Account Balance, Based on Expected No-Lapse Guarantee Benefits And Expected Policy Assessments	This table summarizes our life policy and investment contract reserves: (Dollars in millions) At December 31, 2017 2016 Life policy reserves: Ordinary/traditional life $ 1,080 $ 1,011 Other 47 45 Subtotal 1,127 1,056 Investment contract reserves: Deferred annuities 835 861 Universal life 601 578 Structured settlements 160 170 Other 6 6 Subtotal 1,602 1,615 Total life policy and investment contract reserves $ 2,729 $ 2,671

Deferred Policy Acquisition C39

Deferred Policy Acquisition Costs (Tables)	12 Months Ended
	Dec. 31, 2017
Deferred Costs [Abstract]
Deferred Policy Acquisition Costs And Asset Reconciliation, Including the Amortized Deferred Policy Acquisition Costs	The table below shows the deferred policy acquisition costs and asset reconciliation: (Dollars in millions) Years ended December 31, 2017 2016 2015 Property casualty: Deferred policy acquisition costs asset, January 1 $ 408 $ 388 $ 379 Capitalized deferred policy acquisition costs 897 840 801 Amortized deferred policy acquisition costs (867 ) (820 ) (792 ) Deferred policy acquisition costs asset, December 31 $ 438 $ 408 $ 388 Life: Deferred policy acquisition costs asset, January 1 $ 229 $ 228 $ 199 Capitalized deferred policy acquisition costs 51 49 45 Amortized deferred policy acquisition costs (46 ) (43 ) (37 ) Amortized shadow deferred policy acquisition costs (2 ) (5 ) 21 Deferred policy acquisition costs asset, December 31 $ 232 $ 229 $ 228 Consolidated: Deferred policy acquisition costs asset, January 1 $ 637 $ 616 $ 578 Capitalized deferred policy acquisition costs 948 889 846 Amortized deferred policy acquisition costs (913 ) (863 ) (829 ) Amortized shadow deferred policy acquisition costs (2 ) (5 ) 21 Deferred policy acquisition costs asset, December 31 $ 670 $ 637 $ 616

Long-Term Debt And Capital Le40

Long-Term Debt And Capital Lease Obligation (Tables)	12 Months Ended
	Dec. 31, 2017
Long-term Debt and Capital Lease Obligations [Abstract]
Book Value And Principal Amounts Of Long-Term Debt	This table summarizes the principal amounts of our long-term debt excluding unamortized discounts, none of which are encumbered by rating triggers: (Dollars in millions) Book value Principal amount Interest rate Year of issue At December 31, At December 31, 2017 2016 2017 2016 6.900% 1998 Senior debentures, due 2028 $ 26 $ 26 $ 28 $ 28 6.920% 2005 Senior debentures, due 2028 391 391 391 391 6.125% 2004 Senior notes, due 2034 370 370 374 374 Total $ 787 $ 787 $ 793 $ 793
Capital Lease Payments Over Next Five Years	Below are the expected capital lease obligations that we expect to pay over the next six years: (Dollars in millions) Years ended December 31, 2018 2019 2020 2021 2022 2023 Capital lease obligations $ 12 $ 10 $ 7 $ 5 $ 4 $ 2

Shareholders' Equity And Divi41

Shareholders' Equity And Dividend Restrictions (Tables)	12 Months Ended
	Dec. 31, 2017
Shareholders Equity And Dividend Restrictions [Abstract]
Change In AOCI Includes Changes In Unrealized Gains And Losses On Investments And Pension Obligations	The changes from the beginning of year to the end of year are the result of changes to other comprehensive income or loss (OCI). Additionally, as a result of the early adoption of ASU 2018-02, Income Statement—Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income, included in the table below is the reclassification of $492 million which increased AOCI and decreased retained earnings. See Note 1, Summary of Significant Accounting Policies for further explanation of this ASU. (Dollars in millions) 2017 2016 2015 Before tax Income tax Net Before Income Net Before Income Net Investments: AOCI, January 1 $ 2,625 $ 908 $ 1,717 $ 2,094 $ 722 $ 1,372 $ 2,719 $ 942 $ 1,777 OCI before realized gains recognized in net income 1,054 366 688 653 229 424 (556 ) (196 ) (360 ) Realized gains recognized in net income (139 ) (49 ) (90 ) (122 ) (43 ) (79 ) (69 ) (24 ) (45 ) OCI 915 317 598 531 186 345 (625 ) (220 ) (405 ) Adjustment to reclassify certain tax effects from AOCI — (492 ) 492 — — — — — — AOCI, December 31 $ 3,540 $ 733 $ 2,807 $ 2,625 $ 908 $ 1,717 $ 2,094 $ 722 $ 1,372 Pension obligations: AOCI, January 1 $ (26 ) $ (8 ) $ (18 ) $ (42 ) $ (14 ) $ (28 ) $ (36 ) $ (12 ) $ (24 ) OCI excluding amortization recognized in net income 12 6 6 13 5 8 (12 ) (5 ) (7 ) Amortization recognized in net income 2 1 1 3 1 2 6 3 3 OCI 14 7 7 16 6 10 (6 ) (2 ) (4 ) AOCI, December 31 $ (12 ) $ (1 ) $ (11 ) $ (26 ) $ (8 ) $ (18 ) $ (42 ) $ (14 ) $ (28 ) Life deferred acquisition costs, life policy reserves and other: AOCI, January 1 $ (9 ) $ (3 ) $ (6 ) $ 1 $ 1 $ — $ (12 ) $ (3 ) $ (9 ) OCI before realized gains recognized in net income 8 5 3 (8 ) (3 ) (5 ) 14 5 9 Realized gains recognized in net income (9 ) (4 ) (5 ) (2 ) (1 ) (1 ) (1 ) (1 ) — OCI (1 ) 1 (2 ) (10 ) (4 ) (6 ) 13 4 9 AOCI, December 31 $ (10 ) $ (2 ) $ (8 ) $ (9 ) $ (3 ) $ (6 ) $ 1 $ 1 $ — Summary of AOCI: AOCI, January 1 $ 2,590 $ 897 $ 1,693 $ 2,053 $ 709 $ 1,344 $ 2,671 $ 927 $ 1,744 Investments OCI 915 317 598 531 186 345 (625 ) (220 ) (405 ) Pension obligations OCI 14 7 7 16 6 10 (6 ) (2 ) (4 ) Life deferred acquisition costs, life policy reserves and other OCI (1 ) 1 (2 ) (10 ) (4 ) (6 ) 13 4 9 Total OCI 928 325 603 537 188 349 (618 ) (218 ) (400 ) Adjustment to reclassify certain tax effects from AOCI — (492 ) 492 — — — — — — AOCI, December 31 $ 3,518 $ 730 $ 2,788 $ 2,590 $ 897 $ 1,693 $ 2,053 $ 709 $ 1,344

Reinsurance (Tables)

Reinsurance (Tables)	12 Months Ended
	Dec. 31, 2017
Reinsurance Disclosures [Abstract]
Property Casualty Insurance Premiums Written On Assumed And Ceded Business [Table Text Block]	The tables below summarize our consolidated property casualty insurance net written premiums, earned premiums and incurred loss and loss expenses: (Dollars in millions) Years ended December 31, 2017 2016 2015 Direct written premiums $ 4,854 $ 4,646 $ 4,461 Assumed written premiums 125 103 77 Ceded written premiums (139 ) (169 ) (177 ) Net written premiums $ 4,840 $ 4,580 $ 4,361
Earned Consolidated Property Casualty Insurance Premiums On Assumed And Ceded Business	(Dollars in millions) Years ended December 31, 2017 2016 2015 Direct earned premiums $ 4,752 $ 4,567 $ 4,396 Assumed earned premiums 132 77 29 Ceded earned premiums (162 ) (162 ) (154 ) Earned premiums $ 4,722 $ 4,482 $ 4,271
Incurred Consolidated Property Casualty Insurance Loss And Loss Expenses On Assumed And Ceded Business	(Dollars in millions) Years ended December 31, 2017 2016 2015 Direct incurred loss and loss expenses $ 2,961 $ 2,874 $ 2,596 Assumed incurred loss and loss expenses 113 43 12 Ceded incurred loss and loss expenses 64 (56 ) (36 ) Incurred loss and loss expenses $ 3,138 $ 2,861 $ 2,572
Earned Life Insurance Premiums On Ceded Business	consolidated life insurance earned premiums and contract holders' benefits incurred: (Dollars in millions) Years ended December 31, 2017 2016 2015 Direct earned premiums $ 300 $ 290 $ 271 Ceded earned premiums (68 ) (62 ) (62 ) Earned premiums $ 232 $ 228 $ 209
Life Insurance Contract Holders' Benefits Incurred On Ceded Business	(Dollars in millions) Years ended December 31, 2017 2016 2015 Direct contract holders' benefits incurred $ 319 $ 303 $ 292 Ceded contract holders' benefits incurred (67 ) (57 ) (56 ) Contract holders' benefits incurred $ 252 $ 246 $ 236

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Components Of Deferred Tax Assets And Liabilities	The significant components of deferred tax assets and liabilities included in the consolidated balance sheets at December 31 were as follows: (Dollars in millions) At December 31, 2017 2016 Deferred tax assets: Loss and loss expense reserves $ 123 $ 199 Unearned premiums 100 158 Investments — 5 Other 27 52 Total gross deferred tax assets 250 414 Deferred tax liabilities: Unrealized investment gains and other, net 740 907 Deferred acquisition costs 123 195 Life policy reserves 111 162 Investments 10 — Other 11 15 Total gross deferred tax liabilities 995 1,279 Net deferred income tax liability $ 745 $ 865
Differences Between The 35 Percent Statutory Income Tax Rate And Effective Income Tax Rate	The differences between the 35 percent statutory federal income tax rate and our effective income tax rate were as follows: (Dollars in millions) Years ended December 31, 2017 2016 2015 Tax at statutory rate: $ 256 35.0 % $ 284 35.0 % $ 308 35.0 % Increase (decrease) resulting from: Tax-exempt income from municipal bonds (36 ) (4.9 ) (34 ) (4.2 ) (33 ) (3.7 ) Dividend received exclusion (34 ) (4.7 ) (33 ) (4.1 ) (32 ) (3.6 ) Deferred tax benefit due to tax rate change (495 ) (67.8 ) — — — — Other (6 ) (0.8 ) 4 0.5 4 0.3 Provision for income taxes $ (315 ) (43.2 )% $ 221 27.2 % $ 247 28.0 %

Net Income Per Common Share (Ta

Net Income Per Common Share (Tables)	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Calculations For Basic And Diluted Earnings Per Share	The table shows calculations for basic and diluted earnings per share: (In millions, except per share data) Years ended December 31, 2017 2016 2015 Numerator: Net income—basic and diluted $ 1,045 $ 591 $ 634 Denominator: Basic weighted-average common shares outstanding 164.2 164.5 164.0 Effect of share-based awards: Stock options 1.1 1.1 1.0 Nonvested shares 0.7 0.9 0.6 Diluted weighted-average shares 166.0 166.5 165.6 Earnings per share: Basic $ 6.36 $ 3.59 $ 3.87 Diluted 6.29 3.55 3.83 Number of anti-dilutive share-based awards 0.7 0.3 0.4

Employee Retirement Benefits (T

Employee Retirement Benefits (Tables)	12 Months Ended
	Dec. 31, 2017
Benefit Obligation Activity Using An Actuarial Measurement Date For Qualified Plan And SERP	Benefit obligation activity using an actuarial measurement date for our qualified pension plan and SERP at December 31 follows: (Dollars in millions) At December 31, 2017 2016 Change in projected benefit obligation: Benefit obligation, January 1 $ 340 $ 323 Service cost 11 11 Interest cost 14 14 Actuarial loss 20 13 Benefits paid (34 ) (21 ) Projected benefit obligation, December 31 $ 351 $ 340 Change in plan assets: Fair value of plan assets, January 1 $ 315 $ 278 Actual return on plan assets 52 45 Employer contribution 12 13 Benefits paid (34 ) (21 ) Fair value of plan assets, December 31 $ 345 $ 315 Funded status, December 31 $ (6 ) $ (25 ) Accumulated benefit obligation $ 322 $ 309
Reconciliation Of The Funded Status For Qualified Plan And SERP	A reconciliation follows of the funded status for our qualified plan and SERP at the end of the measurement period to the amounts recognized in the consolidated balance sheets at December 31: (Dollars in millions) At December 31, 2017 2016 Pension amounts recognized in the consolidated balance sheets: Other liabilities $ (6 ) $ (25 ) Total $ (6 ) $ (25 ) Pension amounts recognized in accumulated other comprehensive income: Net actuarial loss $ 12 $ 26 Prior service cost — — Total $ 12 $ 26
Components Of Net Periodic Benefit Cost As Well As Other Changes In Plan Assets And Benefit Obligations Recognized In Other Comprehensive Income For Qualified Plan And SERP	Below are the components of our net periodic benefit cost, as well as other changes in plan assets and benefit obligations recognized in other comprehensive income for our qualified plan and SERP at December 31: (Dollars in millions) Years ended December 31, 2017 2016 2015 Net periodic benefit cost: Service cost $ 11 $ 11 $ 12 Interest cost 14 14 14 Expected return on plan assets (21 ) (19 ) (18 ) Amortization of actuarial loss and prior service cost 2 3 6 Other 1 — 1 Net periodic benefit cost $ 7 $ 9 $ 15 Other changes in plan assets and benefit obligations recognized in other comprehensive income: Current year actuarial (gain) loss $ (11 ) $ (13 ) $ 13 Amortization of actuarial loss (3 ) (2 ) (6 ) Amortization of prior service cost — (1 ) (1 ) Total recognized in other comprehensive (income) loss $ (14 ) $ (16 ) $ 6 Total recognized in net periodic benefit cost and other comprehensive (income) loss $ (7 ) $ (7 ) $ 21
Fair Value Hierarchy Of Assets Measured At Fair Value On A Recurring Basis	(Dollars in millions) Quoted prices in Significant other Significant (Level 3) Total At December 31, 2017 Fixed maturities, available for sale: States, municipalities and political subdivisions $ — $ 31 $ — $ 31 Corporate — 34 — 34 Total fixed maturities, available for sale — 65 — 65 Common equities, available for sale 262 — — 262 Total $ 262 $ 65 $ — $ 327 At December 31, 2016 Fixed maturities, available for sale: States, municipalities and political subdivisions $ — $ 31 $ — $ 31 Corporate — 20 — 20 Total fixed maturities, available for sale — 51 — 51 Common equities, available for sale 253 — — 253 Total $ 253 $ 51 $ — $ 304
Expected Future Benefit Payments For Qualified Plan And SERP	We expect to make the following benefit payments for our qualified plan and SERP, reflecting expected future service: (Dollars in millions) Years ended December 31, 2018 2019 2020 2021 2022 2023 - 2027 Expected future benefit payments $ 26 $ 24 $ 25 $ 29 $ 26 $ 146
Benefit Obligations
Weighted-Average Assumptions Used	This is a summary of the weighted-average assumptions used to determine our benefit obligations at December 31 for the plans: Qualified Pension Plan SERP 2017 2016 2017 2016 Discount rate 3.73 % 4.30 % 3.61 % 4.10 % Rate of compensation increase 2.75-3.25 2.75-3.25 2.75-3.25 2.75-3.25
Net Periodic Benefit Cost
Weighted-Average Assumptions Used	This is a summary of the weighted-average assumptions used to determine our net periodic benefit cost for the plans: Qualified Pension Plan SERP 2017 2016 2015 2017 2016 2015 Discount rate 4.30 % 4.55 % 4.25 % 4.10 % 4.30 % 4.05 % Expected return on plan assets 7.25 7.25 7.25 n/a n/a n/a Rate of compensation increase 2.75-3.25 2.75-3.25 2.75-3.25 2.75-3.25 2.75-3.25 2.75-3.25

Statutory Accounting Informat46

Statutory Accounting Information (Tables)	12 Months Ended
	Dec. 31, 2017
Staturory Accounting Information [Abstract]
Statutory Net Income And Statutory Surplus	The statutory net income (loss) and statutory capital and surplus are presented below: (Dollars in millions) Net income (loss) Capital and surplus Years ended December 31, At December 31, 2017 2016 2015 2017 2016 The Cincinnati Insurance Company $ 401 $ 434 $ 534 $ 5,094 $ 4,686 The Cincinnati Casualty Company 21 11 12 392 360 The Cincinnati Indemnity Company 4 4 3 100 93 The Cincinnati Specialty Underwriters Insurance Company 58 57 49 436 372 The Cincinnati Life Insurance Company 12 2 (11 ) 195 200

Share-Based Associate Compens47

Share-Based Associate Compensation Plans (Tables)	12 Months Ended
	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Option Information	Below is a summary of option information for the year 2017 : (Dollars in millions, except exercise price. Shares in thousands) Shares Weighted- exercise price Aggregate Weighted-average Outstanding option shares at January 1, 2017 3,012 $ 42.12 Granted 706 70.70 Exercised (527 ) 38.33 Forfeited or expired (125 ) 47.07 Outstanding option shares at December 31, 2017 3,066 49.14 $ 79 5.61 years Options exercisable at end of period 2,072 $ 40.69 $ 71 4.13 years
Restricted Stock Unit Information	Below is a summary of service-based and performance-based share information, assuming a target payout for performance-based shares, for the year 2017 : (Shares in thousands) Service-based Weighted- Performance-based Weighted- Nonvested at January 1, 2017 888 $ 48.59 236 $ 49.64 Granted 292 65.16 57 43.26 Vested (311 ) 43.05 (87 ) 36.73 Forfeited or canceled (26 ) 55.59 — — Nonvested at December 31, 2017 843 56.16 206 53.35
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Assumptions Used In Option Grants Issued	The following weighted average assumptions were used in determining fair value for option grants issued: 2017 2016 2015 Weighted-average expected term 8 years 8 years 8-9 years Expected volatility 16.95% 24.88-25.75% 25.04-26.15% Dividend yield 2.83% 2.58-3.12% 3.52% Risk-free rates 2.33% 1.44-1.60% 1.94-2.01% Weighted-average fair value of options granted during the period $10.79 $13.21 $11.15
Performance Based Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Assumptions Used In Option Grants Issued	The following assumptions were used in determining fair value for performance-based grants issued: 2017 2016 2015 Expected term 2.89 years 2.44-2.88 years 2.88 years Expected volatility 15.75-28.35% 15.42-33.64% 13.78-34.69% Dividend yield 2.83% 2.58-3.12% 3.52% Risk-free rates 1.44% 0.77-0.87% 0.99%

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Segment Information	Segment information is summarized in the following table: (Dollars in millions) Years ended December 31, 2017 2016 2015 Revenues: Commercial lines insurance Commercial casualty $ 1,072 $ 1,050 $ 1,010 Commercial property 903 867 815 Commercial auto 634 594 561 Workers' compensation 335 354 367 Other commercial 221 224 243 Commercial lines insurance premiums 3,165 3,089 2,996 Fee revenues 5 5 4 Total commercial lines insurance 3,170 3,094 3,000 Personal lines insurance Personal auto 582 543 506 Homeowner 518 486 463 Other personal 141 132 128 Personal lines insurance premiums 1,241 1,161 1,097 Fee revenues 5 4 3 Total personal lines insurance 1,246 1,165 1,100 Excess and surplus lines insurance 209 183 168 Fee revenues 1 1 1 Total excess and surplus lines insurance 210 184 169 Life insurance premiums 232 228 209 Fee revenues 5 5 5 Total life insurance 237 233 214 Investments Investment income, net of expenses 609 595 572 Realized investment gains, net 148 124 70 Total investment revenue 757 719 642 Other Cincinnati Re insurance premiums 107 49 10 Other 5 5 7 Total other revenue 112 54 17 Total revenues $ 5,732 $ 5,449 $ 5,142 Income (loss) before income taxes: Insurance underwriting results Commercial lines insurance $ 119 $ 184 $ 345 Personal lines insurance (32 ) (12 ) (12 ) Excess and surplus lines insurance 61 62 51 Life insurance (1 ) 1 (2 ) Investments 664 629 556 Other (81 ) (52 ) (57 ) Total income before income taxes $ 730 $ 812 $ 881 December 31, December 31, Identifiable assets: 2017 2016 Property casualty insurance $ 2,863 $ 2,967 Life insurance 1,409 1,366 Investments 17,112 15,569 Other 459 484 Total $ 21,843 $ 20,386

Quarterly Supplementary Data (T

Quarterly Supplementary Data (Tables)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Unaudited Quarterly Financial Information	This table includes unaudited quarterly financial information for the years ended December 31, 2017 and 2016 : (Dollars in millions, except per share data) Quarter 1st 2nd 3rd 4th Full year 2017 Revenues $ 1,523 $ 1,386 $ 1,412 $ 1,411 $ 5,732 Income before income taxes 276 128 129 197 730 Net income 201 100 102 642 1,045 Net income per common share—basic 1.22 0.61 0.62 3.92 6.36 Net income per common share—diluted 1.21 0.60 0.61 3.88 6.29 2016 Revenues $ 1,364 $ 1,371 $ 1,402 $ 1,312 $ 5,449 Income before income taxes 265 166 253 128 812 Net income 188 123 180 100 591 Net income per common share—basic 1.14 0.75 1.09 0.61 3.59 Net income per common share—diluted 1.13 0.74 1.08 0.60 3.55

Summary Of Significant Accoun50

Summary Of Significant Accounting Policies (Narrative) (Details)	12 Months Ended
	Dec. 31, 2017USD ($)statesubsidiaryindependent_insurance_agencyreporting_locations	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2008
Significant Accounting Policies
Unrealized gains reclassified to retained earnings for ASU 2016-01, after tax	$ 2,503,000,000
Excess tax benefit, amount	7,000,000
Income Tax Examination, Penalties Expense	$ 0
Number of operating subsidaries | subsidiary	2
Number of independent insurance agencies | independent_insurance_agency	1,702
Number of reporting locations | reporting_locations	2,256
Number of states in which entity operates | state	42
Defined Benefit Plan Qualifying Age				40 years
Current fair value of the BOLI invested assets and cash exceeded the current fair value of the contract holders' account value	$ 29,000,000
Other invested assets	103,000,000	$ 81,000,000
Depreciation expense	28,000,000	30,000,000	$ 36,000,000
Land, building and equipment impairments	0	0	0
Net cash used in financing activities	$ (614,000,000)	(426,000,000)	(498,000,000)
Minimum
Significant Accounting Policies
Estimated useful lives	3 years
Maximum
Significant Accounting Policies
Estimated useful lives	39 years 6 months
Life Policy Loans
Significant Accounting Policies
Other invested assets	$ 31,000,000	31,000,000
Venture Capital Funds
Significant Accounting Policies
Other invested assets	35,000,000	23,000,000
Real Estate Investment
Significant Accounting Policies
Other invested assets	$ 37,000,000	$ 27,000,000
10 Largest States
Significant Accounting Policies
Generated percentage of total earned premiums	59.70%	61.40%
Ohio, Largest State
Significant Accounting Policies
Generated percentage of total earned premiums	16.20%	16.80%
Indiana, Illinois, Pennsylvania, Georgia, Michigan and North Carolina | Minimum
Significant Accounting Policies
Generated percentage of total earned premiums	5.00%
Indiana, Illinois, Pennsylvania, Georgia, Michigan and North Carolina | Maximum
Significant Accounting Policies
Generated percentage of total earned premiums	7.00%
Largest Single Agency Relationship
Significant Accounting Policies
Generated percentage of total earned premiums	0.80%
All Other | Maximum
Significant Accounting Policies
Generated percentage of total earned premiums	4.00%
Stock Options
Significant Accounting Policies
Weighted-average remaining contractual life for options expected to vest	10 years
Property Casualty Insurance Segment
Significant Accounting Policies
Number of operating subsidaries | subsidiary	2
Stock Options
Significant Accounting Policies
Awards vesting period	3 years
Restricted Stock Units (RSUs)
Significant Accounting Policies
Awards vesting period	3 years
Accounting Standards Update 2016-09
Significant Accounting Policies
Net cash used in financing activities	$ 13,000,000	$ 12,000,000	11,000,000
Adjustment to reclassify certain tax effects from AOCI to retained earnings	0
New Accounting Pronouncement, Early Adoption, Effect | Accumulated Other Comprehensive Income | Accounting Standards Update 2018-02
Significant Accounting Policies
Adjustment to reclassify certain tax effects from AOCI to retained earnings	492,000,000	0	0
New Accounting Pronouncement, Early Adoption, Effect | Retained Earnings | Accounting Standards Update 2018-02
Significant Accounting Policies
Adjustment to reclassify certain tax effects from AOCI to retained earnings	$ (492,000,000)	$ 0	$ 0

Investments (Narrative) (Detail

Investments (Narrative) (Details) $ in Millions	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Gain (Loss) on Investments
Largest equity holdings to total equity portfolio	4.00%
Largest equity holdings to total portfolio	1.40%
Investments in fair value, deposit with various states	$ 17,774	$ 16,193
Impaired securities	6	4	20
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, aggregate loss	$ 18	$ 11	$ 37
Collateral at fair value	$ 57	$ 22
Fixed Maturities
Gain (Loss) on Investments
Number of securities total unrealized loss in an unrealized loss position for 12 months or more	249	32	69
Number of securities below 70 percent of amortized cost	0	0	5
Equity Securities
Gain (Loss) on Investments
Number of securities total unrealized loss in an unrealized loss position for 12 months or more	0	0	0
Exxon Mobil Corporation, The Procter & Gamble Company, Honeywell International Inc, BlackRock Inc., Genuine Parts Company, RPM International, and Johnson and Johnson [Member]
Gain (Loss) on Investments
Available-for-sale securities, accumulated net gain position	$ 1,013
Seven Primary Contributors
Gain (Loss) on Investments
Number of securities	7
On Deposit With Various States
Gain (Loss) on Investments
Investments in fair value, deposit with various states	$ 101	$ 72

Investments (Analysis Of Cost O

Investments (Analysis Of Cost Or Amortized Cost Gross Unrealized Gains And Losses And Fair Value For Investments) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Fixed Maturities
Schedule of Available-for-sale Securities
Cost or amortized cost	$ 10,314	$ 9,799
Gross unrealized gains	409	359
Gross unrealized losses	24	73
Fair value	10,699	10,085
Fixed Maturities | Corporate Securities
Schedule of Available-for-sale Securities
Cost or amortized cost	5,420	5,555
Gross unrealized gains	246	252
Gross unrealized losses	13	26
Fair value	5,653	5,781
Fixed Maturities | States, Municipalities and Political Subdivisions
Schedule of Available-for-sale Securities
Cost or amortized cost	4,316	3,770
Gross unrealized gains	155	100
Gross unrealized losses	6	42
Fair value	4,465	3,828
Fixed Maturities | Commercial Mortgage Backed Securities
Schedule of Available-for-sale Securities
Cost or amortized cost	280	282
Gross unrealized gains	7	7
Gross unrealized losses	1	2
Fair value	286	287
Fixed Maturities | Government-Sponsored Enterprises
Schedule of Available-for-sale Securities
Cost or amortized cost	257	167
Gross unrealized gains	1	0
Gross unrealized losses	4	3
Fair value	254	164
Fixed Maturities | Foreign Government
Schedule of Available-for-sale Securities
Cost or amortized cost	10	10
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Fair value	10	10
Fixed Maturities | Convertibles and Bonds with Warrants Attached
Schedule of Available-for-sale Securities
Cost or amortized cost		5
Gross unrealized gains		0
Gross unrealized losses		0
Fair value		5
Fixed Maturities | United States Government
Schedule of Available-for-sale Securities
Cost or amortized cost	31	10
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Fair value	31	10
Equity Securities
Schedule of Available-for-sale Securities
Cost or amortized cost	3,094	2,995
Gross unrealized gains	3,169	2,348
Gross unrealized losses	14	9
Fair value	6,249	5,334
Equity Securities | Common Equities
Schedule of Available-for-sale Securities
Cost or amortized cost	2,918	2,812
Gross unrealized gains	3,135	2,320
Gross unrealized losses	14	9
Fair value	6,039	5,123
Equity Securities | Nonredeemable Preferred Equities
Schedule of Available-for-sale Securities
Cost or amortized cost	176	183
Gross unrealized gains	34	28
Gross unrealized losses	0	0
Fair value	210	211
Fixed Maturities And Equity Securities
Schedule of Available-for-sale Securities
Cost or amortized cost	13,408	12,794
Gross unrealized gains	3,578	2,707
Gross unrealized losses	38	82
Fair value	$ 16,948	$ 15,419

Investments (Fair Values And Un

Investments (Fair Values And Unrealized Losses By Investment Category And By The Duration Of The Securities' Continuous Unrealized Loss Position) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Investments, Unrealized Loss Position
Less than 12 months fair value	$ 809	$ 2,079
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	20	71
12 months or more fair value	682	191
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	18	11
Total fair value	1,491	2,270
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	38	82
Fixed Maturities
Investments, Unrealized Loss Position
Less than 12 months fair value	580	1,972
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	6	62
12 months or more fair value	682	191
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	18	11
Total fair value	1,262	2,163
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	24	73
Fixed Maturities | Corporate Securities
Investments, Unrealized Loss Position
Less than 12 months fair value	330	733
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	4	15
12 months or more fair value	252	189
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	9	11
Total fair value	582	922
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	13	26
Fixed Maturities | States, Municipalities and Political Subdivisions
Investments, Unrealized Loss Position
Less than 12 months fair value	88	989
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	1	42
12 months or more fair value	264	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	5	0
Total fair value	352	989
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	6	42
Fixed Maturities | Commercial Mortgage Backed Securities
Investments, Unrealized Loss Position
Less than 12 months fair value	33	89
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	2
12 months or more fair value	36	2
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	1	0
Total fair value	69	91
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	1	2
Fixed Maturities | Government-Sponsored Enterprises
Investments, Unrealized Loss Position
Less than 12 months fair value	96	155
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	1	3
12 months or more fair value	124	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	3	0
Total fair value	220	155
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	4	3
Fixed Maturities | Foreign government
Investments, Unrealized Loss Position
Less than 12 months fair value	10
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0
12 months or more fair value	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0
Total fair value	10
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	0
Fixed Maturities | United States Government
Investments, Unrealized Loss Position
Less than 12 months fair value	23	6
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	0
12 months or more fair value	6	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Total fair value	29	6
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	0	0
Equity Securities
Investments, Unrealized Loss Position
Less than 12 months fair value	229	107
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	14	9
12 months or more fair value	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Total fair value	229	107
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	14	9
Equity Securities | Common Equities
Investments, Unrealized Loss Position
Less than 12 months fair value	229	103
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	14	9
12 months or more fair value	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Total fair value	229	103
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 14	9
Equity Securities | Nonredeemable Preferred Equities
Investments, Unrealized Loss Position
Less than 12 months fair value		4
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		0
12 months or more fair value		0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		0
Total fair value		4
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss		$ 0

Investments (Contractual Maturi

Investments (Contractual Maturity Dates For Fixed-Maturity And Short-Term Investments) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Amortized cost
Due in one year or less	$ 511
Due after one year through five years	2,736
Due after five years through ten years	3,921
Due after ten years	3,146
Total	10,314	$ 9,799
Fair value
Due in one year or less	519
Due after one year through five years	2,839
Due after five years through ten years	4,058
Due after ten years	3,283
Total	$ 10,699	$ 10,085
% of fair value
Due in one year or less	4.90%
Due after one year through five years	26.50%
Due after five years through ten years	37.90%
Due after ten years	30.70%
Total	100.00%

Investments (Investment Income

Investments (Investment Income Realized Investment Gains And Losses) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Investment income:
Interest	$ 445	$ 440	$ 428
Dividends	170	161	150
Other	4	3	3
Total	619	604	581
Less investment expenses	10	9	9
Total	609	595	572
Realized investment gains and losses:
Other	9	2	1
Total	148	124	70
Fixed Maturities
Realized investment gains and losses:
Gross realized gains	25	26	18
Gross realized losses	0	(1)	0
Other-than-temporary impairments	(6)	(2)	(18)
Equity Securities
Realized investment gains and losses:
Gross realized gains	195	152	129
Gross realized losses	(72)	(53)	(26)
Other-than-temporary impairments	$ (3)	$ 0	$ (34)

Fair Value Measurements (Narrat

Fair Value Measurements (Narrative) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Principal amount of debt	$ 793	$ 793
Recorded outstanding principal and interest for these life policy loans	61	51
Reserves for structured settlements	$ 5,273	$ 5,085
Maximum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Percentage of Level 3 assets measured at fair value	1.00%	1.00%
Life Policy Loans
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Recorded outstanding principal and interest for these life policy loans	$ 31	$ 31
Deferred Annuities and Structured Settlements
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Recorded reserves for the deferred annuities	835	861
Reserves for structured settlements	$ 161	$ 170

Fair Value Measurements (Fair V

Fair Value Measurements (Fair Value Hierarchy For Assets Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Available for sale securities, debt securities	$ 10,699	$ 10,085
Available for sale securities, equity securities	6,249	5,334
Separate accounts taxable fixed maturities	806	766
Total	17,774	16,193
Top Hat Savings Plan - Mutual Funds and Common Equities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Top Hat savings plan mutual funds and common equity (included in Other assets)	31	24
Fixed Maturities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Available for sale securities, debt securities	10,699	10,085
Fixed Maturities | Corporate Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Available for sale securities, debt securities	5,653	5,781
Fixed Maturities | States, Municipalities and Political Subdivisions
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Available for sale securities, debt securities	4,465	3,828
Fixed Maturities | Commercial Mortgage Backed Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Available for sale securities, debt securities	286	287
Fixed Maturities | Government-Sponsored Enterprises
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Available for sale securities, debt securities	254	164
Fixed Maturities | Foreign Government
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Available for sale securities, debt securities	10	10
Fixed Maturities | Convertibles and Bonds with Warrants Attached
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Available for sale securities, debt securities		5
Fixed Maturities | United States Government
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Available for sale securities, debt securities	31	10
Equity Securities | Common Equities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Available for sale securities, equity securities	6,039	5,123
Equity Securities | Nonredeemable Preferred Equities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Available for sale securities, equity securities	210	211
Taxable Fixed Maturities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Separate accounts taxable fixed maturities	795	750
Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Total	6,101	5,157
Level 1 | Top Hat Savings Plan - Mutual Funds and Common Equities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Top Hat savings plan mutual funds and common equity (included in Other assets)	31	24
Level 1 | Fixed Maturities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Available for sale securities, debt securities	31	10
Level 1 | Fixed Maturities | Corporate Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Available for sale securities, debt securities	0	0
Level 1 | Fixed Maturities | States, Municipalities and Political Subdivisions
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Available for sale securities, debt securities	0	0
Level 1 | Fixed Maturities | Commercial Mortgage Backed Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Available for sale securities, debt securities	0	0
Level 1 | Fixed Maturities | Government-Sponsored Enterprises
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Available for sale securities, debt securities	0	0
Level 1 | Fixed Maturities | Foreign Government
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Available for sale securities, debt securities	0	0
Level 1 | Fixed Maturities | Convertibles and Bonds with Warrants Attached
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Available for sale securities, debt securities		0
Level 1 | Fixed Maturities | United States Government
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Available for sale securities, debt securities	31	10
Level 1 | Equity Securities | Common Equities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Available for sale securities, equity securities	6,039	5,123
Level 1 | Equity Securities | Nonredeemable Preferred Equities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Available for sale securities, equity securities	0	0
Level 1 | Taxable Fixed Maturities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Separate accounts taxable fixed maturities	0	0
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Total	11,667	10,958
Level 2 | Top Hat Savings Plan - Mutual Funds and Common Equities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Top Hat savings plan mutual funds and common equity (included in Other assets)	0	0
Level 2 | Fixed Maturities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Available for sale securities, debt securities	10,662	9,997
Level 2 | Fixed Maturities | Corporate Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Available for sale securities, debt securities	5,652	5,703
Level 2 | Fixed Maturities | States, Municipalities and Political Subdivisions
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Available for sale securities, debt securities	4,460	3,828
Level 2 | Fixed Maturities | Commercial Mortgage Backed Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Available for sale securities, debt securities	286	287
Level 2 | Fixed Maturities | Government-Sponsored Enterprises
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Available for sale securities, debt securities	254	164
Level 2 | Fixed Maturities | Foreign Government
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Available for sale securities, debt securities	10	10
Level 2 | Fixed Maturities | Convertibles and Bonds with Warrants Attached
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Available for sale securities, debt securities		5
Level 2 | Fixed Maturities | United States Government
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Available for sale securities, debt securities	0	0
Level 2 | Equity Securities | Common Equities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Available for sale securities, equity securities	0	0
Level 2 | Equity Securities | Nonredeemable Preferred Equities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Available for sale securities, equity securities	210	211
Level 2 | Taxable Fixed Maturities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Separate accounts taxable fixed maturities	795	750
Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Total	6	78
Level 3 | Top Hat Savings Plan - Mutual Funds and Common Equities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Top Hat savings plan mutual funds and common equity (included in Other assets)	0	0
Level 3 | Fixed Maturities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Available for sale securities, debt securities	6	78
Level 3 | Fixed Maturities | Corporate Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Available for sale securities, debt securities	1	78
Level 3 | Fixed Maturities | States, Municipalities and Political Subdivisions
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Available for sale securities, debt securities	5	0
Level 3 | Fixed Maturities | Commercial Mortgage Backed Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Available for sale securities, debt securities	0	0
Level 3 | Fixed Maturities | Government-Sponsored Enterprises
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Available for sale securities, debt securities	0	0
Level 3 | Fixed Maturities | Foreign Government
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Available for sale securities, debt securities	0	0
Level 3 | Fixed Maturities | Convertibles and Bonds with Warrants Attached
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Available for sale securities, debt securities		0
Level 3 | Fixed Maturities | United States Government
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Available for sale securities, debt securities	0	0
Level 3 | Equity Securities | Common Equities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Available for sale securities, equity securities	0	0
Level 3 | Equity Securities | Nonredeemable Preferred Equities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Available for sale securities, equity securities	0	0
Level 3 | Taxable Fixed Maturities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Separate accounts taxable fixed maturities	$ 0	$ 0

Fair Value Measurements (Asset

Fair Value Measurements (Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Beginning balance	$ 78	$ 55
Total gains or losses (realized/unrealized):
Included in net income	0	0
Included in other comprehensive income	0	(1)
Purchases	5	57
Sales	0	(3)
Transfers into Level 3	0	13
Transfers out of Level 3	(77)	(43)
Ending balance	6	78
Corporate Fixed Maturities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Beginning balance	78	51
Total gains or losses (realized/unrealized):
Included in net income	0	0
Included in other comprehensive income	0	0
Purchases	0	57
Sales	0	(1)
Transfers into Level 3	0	13
Transfers out of Level 3	(77)	(42)
Ending balance	1	78
Taxable Fixed Maturities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Beginning balance	0	1
Total gains or losses (realized/unrealized):
Included in net income	0	0
Included in other comprehensive income	0	0
Purchases	0	0
Sales	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	(1)
Ending balance	0	0
States, Municipalities and Political Subdivisions
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Beginning balance	0
Total gains or losses (realized/unrealized):
Included in net income	0
Included in other comprehensive income	0
Purchases	5
Sales	0
Transfers into Level 3	0
Transfers out of Level 3	0
Ending balance	5	0
Nonredeemable Preferred Equities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
Beginning balance	0	3
Total gains or losses (realized/unrealized):
Included in net income	0	0
Included in other comprehensive income	0	(1)
Purchases	0	0
Sales	0	(2)
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Ending balance	$ 0	$ 0

Fair Value Measurements (Fair59

Fair Value Measurements (Fair Value of Note Payable and Long-Term Debt) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Fair value of note payable	$ 24	$ 20
Total	1,040	976
6.900% Senior Debentures, Due 2028
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Fair value of senior debt	$ 34	$ 33
Interest rate	6.90%	6.90%
Debt instrument, year of maturity	2,028	2,028
6.920% Senior Debentures, Due 2028
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Fair value of senior debt	$ 505	$ 488
Interest rate	6.92%	6.92%
Debt instrument, year of maturity	2,028	2,028
6.125% Senior Notes, Due 2034
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Fair value of senior debt	$ 477	$ 435
Interest rate	6.125%	6.125%
Debt instrument, year of maturity	2,034	2,034
Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Fair value of note payable	$ 0	$ 0
Total	0	0
Level 1 | 6.900% Senior Debentures, Due 2028
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Fair value of senior debt	0	0
Level 1 | 6.920% Senior Debentures, Due 2028
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Fair value of senior debt	0	0
Level 1 | 6.125% Senior Notes, Due 2034
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Fair value of senior debt	0	0
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Fair value of note payable	24	20
Total	1,040	976
Level 2 | 6.900% Senior Debentures, Due 2028
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Fair value of senior debt	34	33
Level 2 | 6.920% Senior Debentures, Due 2028
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Fair value of senior debt	505	488
Level 2 | 6.125% Senior Notes, Due 2034
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Fair value of senior debt	477	435
Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Fair value of note payable	0	0
Total	0	0
Level 3 | 6.900% Senior Debentures, Due 2028
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Fair value of senior debt	0	0
Level 3 | 6.920% Senior Debentures, Due 2028
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Fair value of senior debt	0	0
Level 3 | 6.125% Senior Notes, Due 2034
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Fair value of senior debt	$ 0	$ 0

Fair Value Measurements (Fair60

Fair Value Measurements (Fair Value of Life Policy) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Fair value of life policy loans	$ 41	$ 40
Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Fair value of life policy loans	0	0
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Fair value of life policy loans	0	0
Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Fair value of life policy loans	$ 41	$ 40

Fair Value Measurements (Fair61

Fair Value Measurements (Fair Value Of Deferred Annuities, Structured Settlements And Other Items) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Fair value of deferred annuities and structured settlements	$ 1,044	$ 1,045
Deferred Annuities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Fair value of deferred annuities and structured settlements	834	839
Structured Settlements
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Fair value of deferred annuities and structured settlements	210	206
Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Fair value of deferred annuities and structured settlements	0	0
Level 1 | Deferred Annuities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Fair value of deferred annuities and structured settlements	0	0
Level 1 | Structured Settlements
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Fair value of deferred annuities and structured settlements	0	0
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Fair value of deferred annuities and structured settlements	210	206
Level 2 | Deferred Annuities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Fair value of deferred annuities and structured settlements	0	0
Level 2 | Structured Settlements
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Fair value of deferred annuities and structured settlements	210	206
Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Fair value of deferred annuities and structured settlements	834	839
Level 3 | Deferred Annuities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Fair value of deferred annuities and structured settlements	834	839
Level 3 | Structured Settlements
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis
Fair value of deferred annuities and structured settlements	$ 0	$ 0

Property Casualty Loss And Lo62

Property Casualty Loss And Loss Expenses (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Supplemental Information for Property, Casualty Insurance Underwriters [Line Items]
Certain accident, life and health loss reserves	$ 5,219,000,000	$ 5,035,000,000	$ 4,660,000,000	$ 4,438,000,000
Prior year claims and claims adjustment expense, (favorable) and unfavorable	119,000,000	168,000,000	184,000,000
Net loss and loss expense reserves for asbestos and environmental claims	$ 84,000,000	$ 85,000,000
Percentage of reserves for asbestos and environmental claims	2.00%	2.00%
Maximum
Supplemental Information for Property, Casualty Insurance Underwriters [Line Items]
Reinsurance retention	$ 500,000
Life and Health Loss Reserves
Supplemental Information for Property, Casualty Insurance Underwriters [Line Items]
Certain accident, life and health loss reserves	54,000,000	$ 50,000,000	58,000,000
Commercial Insurance
Supplemental Information for Property, Casualty Insurance Underwriters [Line Items]
Prior year claims and claims adjustment expense, (favorable) and unfavorable	73,000,000	129,000,000	154,000,000
Commercial Insurance | Workers' Compensation Line
Supplemental Information for Property, Casualty Insurance Underwriters [Line Items]
Certain accident, life and health loss reserves	992,000,000
Prior year claims and claims adjustment expense, (favorable) and unfavorable	54,000,000	69,000,000	93,000,000
Commercial Insurance | Commercial Property Line
Supplemental Information for Property, Casualty Insurance Underwriters [Line Items]
Certain accident, life and health loss reserves	277,000,000
Prior year claims and claims adjustment expense, (favorable) and unfavorable	33,000,000	29,000,000
Commercial Insurance | Other Commercial Lines
Supplemental Information for Property, Casualty Insurance Underwriters [Line Items]
Prior year claims and claims adjustment expense, (favorable) and unfavorable	30,000,000	42,000,000
Commercial Insurance | Commercial Casualty Line
Supplemental Information for Property, Casualty Insurance Underwriters [Line Items]
Certain accident, life and health loss reserves	1,987,000,000
Prior year claims and claims adjustment expense, (favorable) and unfavorable	(11,000,000)	20,000,000	63,000,000
Commercial Insurance | Commercial Auto Line
Supplemental Information for Property, Casualty Insurance Underwriters [Line Items]
Certain accident, life and health loss reserves	595,000,000
Prior year claims and claims adjustment expense, (favorable) and unfavorable	(33,000,000)	(31,000,000)	(31,000,000)
Personal Insurance
Supplemental Information for Property, Casualty Insurance Underwriters [Line Items]
Prior year claims and claims adjustment expense, (favorable) and unfavorable	14,000,000	4,000,000	(5,000,000)
Personal Insurance | Personal Auto
Supplemental Information for Property, Casualty Insurance Underwriters [Line Items]
Certain accident, life and health loss reserves	307,000,000
Prior year claims and claims adjustment expense, (favorable) and unfavorable		(18,000,000)
Excess and Surplus Lines Insurance
Supplemental Information for Property, Casualty Insurance Underwriters [Line Items]
Certain accident, life and health loss reserves	343,000,000
Prior year claims and claims adjustment expense, (favorable) and unfavorable	29,000,000	34,000,000	35,000,000
Reinsurance assumed and other non segment [Member]
Supplemental Information for Property, Casualty Insurance Underwriters [Line Items]
Prior year claims and claims adjustment expense, (favorable) and unfavorable	$ 3,000,000	$ 1,000,000	$ 0

Property Casualty Loss And Lo63

Property Casualty Loss And Loss Expenses (Consolidated Property Casualty Loss And Loss Expense Reserves) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Insurance [Abstract]
Gross loss and loss expense reserves, January 1	$ 5,035	$ 4,660	$ 4,438
Less reinsurance recoverable	298	281	282
Net loss and loss expense reserves, January 1	4,737	4,379	4,156
Net incurred loss and loss expenses related to:
Current accident year	3,257	3,029	2,756
Prior accident years	(119)	(168)	(184)
Total incurred	3,138	2,861	2,572
Net paid loss and loss expenses related to:
Current accident year	1,404	1,260	1,152
Prior accident years	1,439	1,243	1,197
Total paid	2,843	2,503	2,349
Net loss and loss expense reserves, December 31	5,032	4,737	4,379
Plus reinsurance recoverable	187	298	281
Gross loss and loss expense reserves, December 31	$ 5,219	$ 5,035	$ 4,660

Property Casualty Loss And Lo64

Property Casualty Loss And Loss Expenses (Reconciliation of Incurred Losses and ALAE) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Liability for Claims and Claims Adjustment Expense [Line Items]
Cumulative incurred losses and ALAE as reported within the triangles, net of reinsurance	$ 2,353
Total liabilities for loss and ALAE, net of reinsurance	4,930
Reinsurance recoverable on unpaid losses	187	$ 298	$ 281	$ 282
Unallocated loss adjustment expense reserves	289
Total liabilities for gross loss and loss expense reserves	5,219	$ 5,035	$ 4,660	$ 4,438
Other Short-duration Insurance Product Line
Liability for Claims and Claims Adjustment Expense [Line Items]
Total liabilities for loss and ALAE, net of reinsurance	315
Commercial Insurance | Commercial Casualty Line
Liability for Claims and Claims Adjustment Expense [Line Items]
Cumulative incurred losses and ALAE as reported within the triangles, net of reinsurance	4,434
Cumulative paid losses and ALAE as reported within the triangles, net of reinsurance	2,573
Liabilities for loss and ALAE for accident years not presented in the triangles, net of reinsurance	83
Total liabilities for loss and ALAE, net of reinsurance	1,944
Reinsurance recoverable on unpaid losses	43
Total liabilities for gross loss and loss expense reserves	1,987
Commercial Insurance | Workers' Compensation Line
Liability for Claims and Claims Adjustment Expense [Line Items]
Cumulative incurred losses and ALAE as reported within the triangles, net of reinsurance	2,259
Cumulative paid losses and ALAE as reported within the triangles, net of reinsurance	1,598
Liabilities for loss and ALAE for accident years not presented in the triangles, net of reinsurance	267
Total liabilities for loss and ALAE, net of reinsurance	928
Reinsurance recoverable on unpaid losses	64
Total liabilities for gross loss and loss expense reserves	992
Commercial Insurance | Commercial Auto Line
Liability for Claims and Claims Adjustment Expense [Line Items]
Cumulative incurred losses and ALAE as reported within the triangles, net of reinsurance	1,955
Cumulative paid losses and ALAE as reported within the triangles, net of reinsurance	1,380
Liabilities for loss and ALAE for accident years not presented in the triangles, net of reinsurance	16
Total liabilities for loss and ALAE, net of reinsurance	591
Reinsurance recoverable on unpaid losses	4
Total liabilities for gross loss and loss expense reserves	595
Commercial Insurance | Commercial Property Line
Liability for Claims and Claims Adjustment Expense [Line Items]
Cumulative incurred losses and ALAE as reported within the triangles, net of reinsurance	2,353
Cumulative paid losses and ALAE as reported within the triangles, net of reinsurance	2,095
Liabilities for loss and ALAE for accident years not presented in the triangles, net of reinsurance	12
Total liabilities for loss and ALAE, net of reinsurance	270
Reinsurance recoverable on unpaid losses	7
Total liabilities for gross loss and loss expense reserves	277
Personal Insurance | Personal Auto
Liability for Claims and Claims Adjustment Expense [Line Items]
Cumulative incurred losses and ALAE as reported within the triangles, net of reinsurance	1,774
Cumulative paid losses and ALAE as reported within the triangles, net of reinsurance	1,503
Liabilities for loss and ALAE for accident years not presented in the triangles, net of reinsurance	5
Total liabilities for loss and ALAE, net of reinsurance	276
Reinsurance recoverable on unpaid losses	31
Total liabilities for gross loss and loss expense reserves	307
Personal Insurance | Home Owner Line
Liability for Claims and Claims Adjustment Expense [Line Items]
Cumulative incurred losses and ALAE as reported within the triangles, net of reinsurance	1,466
Cumulative paid losses and ALAE as reported within the triangles, net of reinsurance	1,358
Liabilities for loss and ALAE for accident years not presented in the triangles, net of reinsurance	3
Total liabilities for loss and ALAE, net of reinsurance	111
Reinsurance recoverable on unpaid losses	3
Total liabilities for gross loss and loss expense reserves	114
Excess and Surplus Lines Insurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Cumulative incurred losses and ALAE as reported within the triangles, net of reinsurance	441
Cumulative paid losses and ALAE as reported within the triangles, net of reinsurance	195
Liabilities for loss and ALAE for accident years not presented in the triangles, net of reinsurance	94
Total liabilities for loss and ALAE, net of reinsurance	340
Reinsurance recoverable on unpaid losses	3
Total liabilities for gross loss and loss expense reserves	$ 343

Property Casualty Loss And Lo65

Property Casualty Loss And Loss Expenses (Claims Development - Commercial Casualty) (Details) reported_claim in Thousands, $ in Millions	Dec. 31, 2017USD ($)reported_claim	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)	Dec. 31, 2012USD ($)	Dec. 31, 2011USD ($)	Dec. 31, 2010USD ($)	Dec. 31, 2009USD ($)	Dec. 31, 2008USD ($)
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	$ 2,353
Liabilities for loss and ALAE, net of reinsurance	4,930
Commercial Casualty Line | Commercial Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	4,434
Cumulative paid losses and ALAE, net of reinsurance	2,573
All outstanding liabilities before, net of reinsurance	83
Liabilities for loss and ALAE, net of reinsurance	1,944
2008 | Commercial Casualty Line | Commercial Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	366	$ 355	$ 357	$ 357	$ 359	$ 362	$ 387	$ 409	$ 458	$ 516
Total of incurred but not reported liabilities plus expected development on reported losses	$ 11
Cumulative number of reported claims | reported_claim	0
Cumulative paid losses and ALAE, net of reinsurance	$ 339	331	325	315	293	262	212	158	93	$ 31
2009 | Commercial Casualty Line | Commercial Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	353	357	357	365	370	360	412	409	484
Total of incurred but not reported liabilities plus expected development on reported losses	$ 10
Cumulative number of reported claims | reported_claim	20
Cumulative paid losses and ALAE, net of reinsurance	$ 328	322	310	295	267	213	151	75	$ 27
2010 | Commercial Casualty Line | Commercial Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	343	349	348	347	349	378	394	495
Total of incurred but not reported liabilities plus expected development on reported losses	$ 19
Cumulative number of reported claims | reported_claim	20
Cumulative paid losses and ALAE, net of reinsurance	$ 314	300	285	256	203	159	92	$ 33
2011 | Commercial Casualty Line | Commercial Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	366	380	375	377	377	404	466
Total of incurred but not reported liabilities plus expected development on reported losses	$ 17
Cumulative number of reported claims | reported_claim	19
Cumulative paid losses and ALAE, net of reinsurance	$ 315	298	266	227	149	93	$ 27
2012 | Commercial Casualty Line | Commercial Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	404	394	394	417	414	466
Total of incurred but not reported liabilities plus expected development on reported losses	$ 43
Cumulative number of reported claims | reported_claim	18
Cumulative paid losses and ALAE, net of reinsurance	$ 330	288	232	170	88	$ 27
2013 | Commercial Casualty Line | Commercial Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	413	416	431	443	448
Total of incurred but not reported liabilities plus expected development on reported losses	$ 64
Cumulative number of reported claims | reported_claim	19
Cumulative paid losses and ALAE, net of reinsurance	$ 286	232	159	90	$ 35
2014 | Commercial Casualty Line | Commercial Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	476	479	496	503
Total of incurred but not reported liabilities plus expected development on reported losses	$ 82
Cumulative number of reported claims | reported_claim	21
Cumulative paid losses and ALAE, net of reinsurance	$ 287	172	97	$ 34
2015 | Commercial Casualty Line | Commercial Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	529	526	533
Total of incurred but not reported liabilities plus expected development on reported losses	$ 170
Cumulative number of reported claims | reported_claim	20
Cumulative paid losses and ALAE, net of reinsurance	$ 200	108	$ 38
2016 | Commercial Casualty Line | Commercial Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	574	563
Total of incurred but not reported liabilities plus expected development on reported losses	$ 247
Cumulative number of reported claims | reported_claim	19
Cumulative paid losses and ALAE, net of reinsurance	$ 126	$ 46
Short-duration Insurance Contracts, Accident Year 2017 [Member] | Commercial Casualty Line | Commercial Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	610
Total of incurred but not reported liabilities plus expected development on reported losses	$ 381
Cumulative number of reported claims | reported_claim	15
Cumulative paid losses and ALAE, net of reinsurance	$ 48

Property Casualty Loss And Lo66

Property Casualty Loss And Loss Expenses (Claims Development - Workers Compensation) (Details) reported_claim in Thousands, $ in Millions	Dec. 31, 2017USD ($)reported_claim	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)	Dec. 31, 2012USD ($)	Dec. 31, 2011USD ($)	Dec. 31, 2010USD ($)	Dec. 31, 2009USD ($)	Dec. 31, 2008USD ($)
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	$ 2,353
Liabilities for loss and ALAE, net of reinsurance	4,930
Workers' Compensation Line | Commercial Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	2,259
Cumulative paid losses and ALAE, net of reinsurance	1,598
All outstanding liabilities before, net of reinsurance	267
Liabilities for loss and ALAE, net of reinsurance	928
2008 | Workers' Compensation Line | Commercial Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	293	$ 296	$ 296	$ 297	$ 299	$ 299	$ 302	$ 310	$ 305	$ 298
Total of incurred but not reported liabilities plus expected development on reported losses	$ 28
Cumulative number of reported claims | reported_claim	0
Cumulative paid losses and ALAE, net of reinsurance	$ 256	254	251	247	242	233	217	195	155	$ 72
2009 | Workers' Compensation Line | Commercial Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	232	234	234	235	238	238	263	278	307
Total of incurred but not reported liabilities plus expected development on reported losses	$ 18
Cumulative number of reported claims | reported_claim	27
Cumulative paid losses and ALAE, net of reinsurance	$ 202	201	198	193	188	179	163	132	$ 65
2010 | Workers' Compensation Line | Commercial Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	237	240	239	240	242	248	274	283
Total of incurred but not reported liabilities plus expected development on reported losses	$ 22
Cumulative number of reported claims | reported_claim	26
Cumulative paid losses and ALAE, net of reinsurance	$ 204	202	198	192	181	164	134	$ 67
2011 | Workers' Compensation Line | Commercial Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	231	236	239	242	246	251	284
Total of incurred but not reported liabilities plus expected development on reported losses	$ 22
Cumulative number of reported claims | reported_claim	24
Cumulative paid losses and ALAE, net of reinsurance	$ 192	190	186	177	161	131	$ 65
2012 | Workers' Compensation Line | Commercial Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	211	213	220	234	245	265
Total of incurred but not reported liabilities plus expected development on reported losses	$ 26
Cumulative number of reported claims | reported_claim	21
Cumulative paid losses and ALAE, net of reinsurance	$ 175	171	162	147	121	$ 62
2013 | Workers' Compensation Line | Commercial Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	208	212	221	246	264
Total of incurred but not reported liabilities plus expected development on reported losses	$ 28
Cumulative number of reported claims | reported_claim	20
Cumulative paid losses and ALAE, net of reinsurance	$ 164	157	144	119	$ 61
2014 | Workers' Compensation Line | Commercial Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	203	214	233	261
Total of incurred but not reported liabilities plus expected development on reported losses	$ 31
Cumulative number of reported claims | reported_claim	19
Cumulative paid losses and ALAE, net of reinsurance	$ 148	134	110	$ 56
2015 | Workers' Compensation Line | Commercial Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	208	220	246
Total of incurred but not reported liabilities plus expected development on reported losses	$ 60
Cumulative number of reported claims | reported_claim	17
Cumulative paid losses and ALAE, net of reinsurance	$ 115	93	$ 47
2016 | Workers' Compensation Line | Commercial Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	218	230
Total of incurred but not reported liabilities plus expected development on reported losses	$ 72
Cumulative number of reported claims | reported_claim	16
Cumulative paid losses and ALAE, net of reinsurance	$ 97	$ 46
Short-duration Insurance Contracts, Accident Year 2017 [Member] | Workers' Compensation Line | Commercial Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	218
Total of incurred but not reported liabilities plus expected development on reported losses	$ 89
Cumulative number of reported claims | reported_claim	13
Cumulative paid losses and ALAE, net of reinsurance	$ 45

Property Casualty Loss And Lo67

Property Casualty Loss And Loss Expenses (Claims Development - Commercial Auto) (Details) reported_claim in Thousands, $ in Millions	Dec. 31, 2017USD ($)reported_claim	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	$ 2,353
Liabilities for loss and ALAE, net of reinsurance	4,930
Commercial Auto Line | Commercial Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	1,955
Cumulative paid losses and ALAE, net of reinsurance	1,380
All outstanding liabilities before, net of reinsurance	16
Liabilities for loss and ALAE, net of reinsurance	591
2013 | Commercial Auto Line | Commercial Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	322	$ 322	$ 315	$ 305	$ 292
Total of incurred but not reported liabilities plus expected development on reported losses	$ 5
Cumulative number of reported claims | reported_claim	46
Cumulative paid losses and ALAE, net of reinsurance	$ 307	285	246	199	$ 141
2014 | Commercial Auto Line | Commercial Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	358	351	346	333
Total of incurred but not reported liabilities plus expected development on reported losses	$ 8
Cumulative number of reported claims | reported_claim	51
Cumulative paid losses and ALAE, net of reinsurance	$ 310	273	223	$ 159
2015 | Commercial Auto Line | Commercial Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	394	384	374
Total of incurred but not reported liabilities plus expected development on reported losses	$ 15
Cumulative number of reported claims | reported_claim	51
Cumulative paid losses and ALAE, net of reinsurance	$ 303	244	$ 173
2016 | Commercial Auto Line | Commercial Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	430	417
Total of incurred but not reported liabilities plus expected development on reported losses	$ 36
Cumulative number of reported claims | reported_claim	53
Cumulative paid losses and ALAE, net of reinsurance	$ 273	$ 184
Short-duration Insurance Contracts, Accident Year 2017 [Member] | Commercial Auto Line | Commercial Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	451
Total of incurred but not reported liabilities plus expected development on reported losses	$ 127
Cumulative number of reported claims | reported_claim	47
Cumulative paid losses and ALAE, net of reinsurance	$ 187

Property Casualty Loss And Lo68

Property Casualty Loss And Loss Expenses (Claims Development - Commercial Property) (Details) reported_claim in Thousands, $ in Millions	Dec. 31, 2017USD ($)reported_claim	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	$ 2,353
Liabilities for loss and ALAE, net of reinsurance	4,930
Commercial Property Line | Commercial Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	2,353
Cumulative paid losses and ALAE, net of reinsurance	2,095
All outstanding liabilities before, net of reinsurance	12
Liabilities for loss and ALAE, net of reinsurance	270
2013 | Commercial Property Line | Commercial Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	357	$ 356	$ 352	$ 359	$ 389
Total of incurred but not reported liabilities plus expected development on reported losses	$ 1
Cumulative number of reported claims | reported_claim	14
Cumulative paid losses and ALAE, net of reinsurance	$ 352	349	344	330	$ 227
2014 | Commercial Property Line | Commercial Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	442	441	444	452
Total of incurred but not reported liabilities plus expected development on reported losses	$ 2
Cumulative number of reported claims | reported_claim	17
Cumulative paid losses and ALAE, net of reinsurance	$ 437	432	412	$ 297
2015 | Commercial Property Line | Commercial Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	416	414	454
Total of incurred but not reported liabilities plus expected development on reported losses	$ 2
Cumulative number of reported claims | reported_claim	17
Cumulative paid losses and ALAE, net of reinsurance	$ 407	388	$ 279
2016 | Commercial Property Line | Commercial Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	551	590
Total of incurred but not reported liabilities plus expected development on reported losses	$ 7
Cumulative number of reported claims | reported_claim	17
Cumulative paid losses and ALAE, net of reinsurance	$ 504	$ 358
Short-duration Insurance Contracts, Accident Year 2017 [Member] | Commercial Property Line | Commercial Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	587
Total of incurred but not reported liabilities plus expected development on reported losses	$ 24
Cumulative number of reported claims | reported_claim	16
Cumulative paid losses and ALAE, net of reinsurance	$ 395

Property Casualty Loss And Lo69

Property Casualty Loss And Loss Expenses (Claims Development - Personal Auto) (Details) reported_claim in Thousands, $ in Millions	Dec. 31, 2017USD ($)reported_claim	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	$ 2,353
Liabilities for loss and ALAE, net of reinsurance	4,930
Personal Auto | Personal Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	1,774
Cumulative paid losses and ALAE, net of reinsurance	1,503
All outstanding liabilities before, net of reinsurance	5
Liabilities for loss and ALAE, net of reinsurance	276
2013 | Personal Auto | Personal Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	298	$ 298	$ 293	$ 280	$ 280
Total of incurred but not reported liabilities plus expected development on reported losses	$ 0
Cumulative number of reported claims | reported_claim	96
Cumulative paid losses and ALAE, net of reinsurance	$ 293	287	272	245	$ 190
2014 | Personal Auto | Personal Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	324	325	317	317
Total of incurred but not reported liabilities plus expected development on reported losses	$ 0
Cumulative number of reported claims | reported_claim	105
Cumulative paid losses and ALAE, net of reinsurance	$ 313	298	267	$ 210
2015 | Personal Auto | Personal Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	356	356	343
Total of incurred but not reported liabilities plus expected development on reported losses	$ 0
Cumulative number of reported claims | reported_claim	108
Cumulative paid losses and ALAE, net of reinsurance	$ 325	292	$ 229
2016 | Personal Auto | Personal Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	384	383
Total of incurred but not reported liabilities plus expected development on reported losses	$ 8
Cumulative number of reported claims | reported_claim	110
Cumulative paid losses and ALAE, net of reinsurance	$ 316	$ 243
Short-duration Insurance Contracts, Accident Year 2017 [Member] | Personal Auto | Personal Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	412
Total of incurred but not reported liabilities plus expected development on reported losses	$ 55
Cumulative number of reported claims | reported_claim	102
Cumulative paid losses and ALAE, net of reinsurance	$ 256

Property Casualty Loss And Lo70

Property Casualty Loss And Loss Expenses (Claims Development - Homeowner) (Details) reported_claim in Thousands, $ in Millions	Dec. 31, 2017USD ($)reported_claim	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	$ 2,353
Liabilities for loss and ALAE, net of reinsurance	4,930
Home Owner Line | Personal Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	1,466
Cumulative paid losses and ALAE, net of reinsurance	1,358
All outstanding liabilities before, net of reinsurance	3
Liabilities for loss and ALAE, net of reinsurance	111
2013 | Home Owner Line | Personal Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	246	$ 247	$ 247	$ 246	$ 252
Total of incurred but not reported liabilities plus expected development on reported losses	$ 0
Cumulative number of reported claims | reported_claim	25
Cumulative paid losses and ALAE, net of reinsurance	$ 246	244	242	236	$ 180
2014 | Home Owner Line | Personal Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	285	286	283	297
Total of incurred but not reported liabilities plus expected development on reported losses	$ 1
Cumulative number of reported claims | reported_claim	26
Cumulative paid losses and ALAE, net of reinsurance	$ 283	281	273	$ 224
2015 | Home Owner Line | Personal Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	275	275	284
Total of incurred but not reported liabilities plus expected development on reported losses	$ 1
Cumulative number of reported claims | reported_claim	24
Cumulative paid losses and ALAE, net of reinsurance	$ 269	260	$ 203
2016 | Home Owner Line | Personal Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	304	315
Total of incurred but not reported liabilities plus expected development on reported losses	$ 3
Cumulative number of reported claims | reported_claim	23
Cumulative paid losses and ALAE, net of reinsurance	$ 283	$ 208
Short-duration Insurance Contracts, Accident Year 2017 [Member] | Home Owner Line | Personal Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	356
Total of incurred but not reported liabilities plus expected development on reported losses	$ 8
Cumulative number of reported claims | reported_claim	24
Cumulative paid losses and ALAE, net of reinsurance	$ 277

Property Casualty Loss And Lo71

Property Casualty Loss And Loss Expenses (Claims Development - Excess and Surplus Lines) (Details) reported_claim in Thousands, $ in Millions	Dec. 31, 2017USD ($)reported_claim	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)	Dec. 31, 2012USD ($)	Dec. 31, 2011USD ($)
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	$ 2,353
Liabilities for loss and ALAE, net of reinsurance	4,930
Excess and Surplus Lines Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	441
Cumulative paid losses and ALAE, net of reinsurance	195
All outstanding liabilities before, net of reinsurance	94
Liabilities for loss and ALAE, net of reinsurance	340
2011 | Excess and Surplus Lines Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	35	$ 35	$ 36	$ 38	$ 44	$ 47	$ 48
Total of incurred but not reported liabilities plus expected development on reported losses	$ 1
Cumulative number of reported claims | reported_claim	1
Cumulative paid losses and ALAE, net of reinsurance	$ 34	32	30	27	23	14	$ 8
2012 | Excess and Surplus Lines Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	36	37	40	49	56	67
Total of incurred but not reported liabilities plus expected development on reported losses	$ 1
Cumulative number of reported claims | reported_claim	1
Cumulative paid losses and ALAE, net of reinsurance	$ 31	29	25	19	15	$ 9
2013 | Excess and Surplus Lines Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	42	45	54	64	74
Total of incurred but not reported liabilities plus expected development on reported losses	$ 4
Cumulative number of reported claims | reported_claim	2
Cumulative paid losses and ALAE, net of reinsurance	$ 32	27	20	12	$ 7
2014 | Excess and Surplus Lines Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	64	75	82	95
Total of incurred but not reported liabilities plus expected development on reported losses	$ 16
Cumulative number of reported claims | reported_claim	2
Cumulative paid losses and ALAE, net of reinsurance	$ 37	27	17	$ 9
2015 | Excess and Surplus Lines Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	73	81	96
Total of incurred but not reported liabilities plus expected development on reported losses	$ 22
Cumulative number of reported claims | reported_claim	2
Cumulative paid losses and ALAE, net of reinsurance	$ 29	19	$ 8
2016 | Excess and Surplus Lines Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	87	93
Total of incurred but not reported liabilities plus expected development on reported losses	$ 34
Cumulative number of reported claims | reported_claim	2
Cumulative paid losses and ALAE, net of reinsurance	$ 21	$ 10
Short-duration Insurance Contracts, Accident Year 2017 [Member] | Excess and Surplus Lines Insurance
Claims Development [Line Items]
Incurred losses and ALAE, net of reinsurance	104
Cumulative paid losses and ALAE, net of reinsurance	$ 11

Property Casualty Loss And Lo72

Property Casualty Loss And Loss Expenses (Average Annual Payout) (Details)	Dec. 31, 2017
Commercial Insurance | Commercial Auto Line
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
1	43.30%
2	18.70%
3	14.50%
4	11.20%
5	6.70%
Commercial Insurance | Workers' Compensation Line
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
1	25.90%
2	26.90%
3	12.40%
4	7.00%
5	4.20%
6	2.40%
7	1.50%
8	1.40%
9	0.80%
10	0.50%
Commercial Insurance | Commercial Casualty Line
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
1	7.90%
2	14.90%
3	18.00%
4	17.70%
5	13.70%
6	8.80%
7	4.80%
8	3.50%
9	1.60%
10	1.80%
Commercial Insurance | Commercial Property Line
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
1	66.00%
2	26.90%
3	4.40%
4	1.10%
5	0.90%
Personal Insurance | Home Owner Line
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
1	74.40%
2	21.30%
3	3.00%
4	0.70%
5	0.40%
Personal Insurance | Personal Auto
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
1	63.70%
2	18.10%
3	9.40%
4	4.80%
5	1.90%
Excess and Surplus Lines Insurance
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
1	16.00%
2	14.10%
3	17.50%
4	14.70%
5	10.70%
6	7.20%
7	1.10%

Life Policy And Investment Co73

Life Policy And Investment Contract Reservess (Reserve In Addition To The Account Balance Based On Expected No-Lapse Guarantee Benefits And Expected Policy Assessments) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Liability for Future Policy Benefit, by Product Segment
Life policy and investment contract reserves	$ 2,729	$ 2,671
Life Policy Reserves
Liability for Future Policy Benefit, by Product Segment
Life policy and investment contract reserves	1,127	1,056
Life Policy Reserves | Ordinary/Traditional Life
Liability for Future Policy Benefit, by Product Segment
Life policy and investment contract reserves	1,080	1,011
Life Policy Reserves | Other Life Policy Reserves
Liability for Future Policy Benefit, by Product Segment
Life policy and investment contract reserves	47	45
Investment contract reserves
Liability for Future Policy Benefit, by Product Segment
Life policy and investment contract reserves	1,602	1,615
Investment contract reserves | Deferred Annuities
Liability for Future Policy Benefit, by Product Segment
Life policy and investment contract reserves	835	861
Investment contract reserves | Universal Life
Liability for Future Policy Benefit, by Product Segment
Life policy and investment contract reserves	601	578
Investment contract reserves | Structured Settlements
Liability for Future Policy Benefit, by Product Segment
Life policy and investment contract reserves	160	170
Investment contract reserves | Other Investment Contract Reserves
Liability for Future Policy Benefit, by Product Segment
Life policy and investment contract reserves	$ 6	$ 6

Deferred Policy Acquisition C74

Deferred Policy Acquisition Costs (Deferred Policy Acquisition Costs And Asset Reconciliation Including The Amortized Deferred Policy Acquisition Costs) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deferred Costs [Roll Forward]
Deferred policy acquisition costs asset at January 1	$ 637	$ 616	$ 578
Capitalized deferred policy acquisition costs	948	889	846
Amortized deferred policy acquisition costs	(913)	(863)	(829)
Amortized shadow deferred policy acquisition costs	(2)	(5)	21
Deferred policy acquisition costs asset at December 31	670	637	616
Property Casualty Insurance Segment [Member]
Deferred Costs [Roll Forward]
Deferred policy acquisition costs asset at January 1	408	388	379
Capitalized deferred policy acquisition costs	897	840	801
Amortized deferred policy acquisition costs	(867)	(820)	(792)
Deferred policy acquisition costs asset at December 31	438	408	388
Life Insurance Product Line [Member]
Deferred Costs [Roll Forward]
Deferred policy acquisition costs asset at January 1	229	228	199
Capitalized deferred policy acquisition costs	51	49	45
Amortized deferred policy acquisition costs	(46)	(43)	(37)
Amortized shadow deferred policy acquisition costs	(2)	(5)	21
Deferred policy acquisition costs asset at December 31	$ 232	$ 229	$ 228

Note Payable (Narrative) (Detai

Note Payable (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Debt Disclosure
Number of lines of credit	1	1
Aggregate borrowing capacity	$ 225	$ 225
Accordian feature available amount	$ 50	50
Line of credit facility, term	5 years
Expiration date of Line of credit	May 13, 2019
Note payable	$ 24	$ 20
Minimum
Debt Disclosure
Line of credit, interest rate	1.65%	1.31%
Maximum
Debt Disclosure
Line of credit, interest rate	2.45%	1.49%

Long-Term Debt And Capital Le76

Long-Term Debt And Capital Lease Obligation (Book Value And Principal Amounts Of Long-Term Debt (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument
Book value	$ 787	$ 787
Principal amount	$ 793	$ 793
6.900% Senior Debentures, Due 2028
Debt Instrument
Interest rate	6.90%	6.90%
Debt issuance year	1,998
Book value	$ 26	$ 26
Principal amount	$ 28	$ 28
6.920% Senior Debentures, Due 2028
Debt Instrument
Interest rate	6.92%	6.92%
Debt issuance year	2,005
Book value	$ 391	$ 391
Principal amount	$ 391	$ 391
6.125% Senior Notes, Due 2034
Debt Instrument
Interest rate	6.125%	6.125%
Debt issuance year	2,004
Book value	$ 370	$ 370
Principal amount	$ 374	$ 374

Long-Term Debt And Capital Le77

Long-Term Debt And Capital Lease Obligation (Capital Lease Payments Over Next Five Years) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Long-term Debt and Capital Lease Obligations [Abstract]
2,018	$ 12
2,019	10
2,020	7
2,021	5
2,022	4
2,023	2
Capital lease obligations	$ 40	$ 39

Shareholders' Equity And Divi78

Shareholders' Equity And Dividend Restrictions (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Declared cash dividends, per share	$ 2.50	$ 1.92	$ 2.3
Dividends declared by insurance subsidiary to parent	$ 465	$ 475	$ 447
Dividend payment without prior regulatory approval, maximum percent of policyholder surplus	10.00%
Dividend payment without prior regulatory approval, percent of statutory net income for the prior calendar year	100.00%
Dividends might be paid during next year	$ 509
Accumulated Other Comprehensive Income | New Accounting Pronouncement, Early Adoption, Effect | Accounting Standards Update 2018-02
Adjustment to reclassify certain tax effects from AOCI to retained earnings	492	0	0
Retained Earnings | New Accounting Pronouncement, Early Adoption, Effect | Accounting Standards Update 2018-02
Adjustment to reclassify certain tax effects from AOCI to retained earnings	$ (492)	$ 0	$ 0

Shareholders' Equity And Divi79

Shareholders' Equity And Dividend Restrictions (Change In AOCI Includes Changes In Unrealized Gains And Losses On Investments And Pension Obligations) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income, Before Tax
OCI	$ 928	$ 537	$ (618)
Pension obligations OCI	14	16	(6)
Accumulated Other Comprehensive Income, Income Tax
OCI	325	188	(218)
Accumulated Other Comprehensive Income, Net of Tax
AOCI, balance at the beginning of the period	1,693
AOCI, balance at the end of the period	2,788	1,693
Accumulated Net Unrealized Investment Gain (Loss)
Accumulated Other Comprehensive Income, Before Tax
AOCI, balance at the beginning of the period	2,625	2,094	2,719
OCI before realized gains recognized in net income	1,054	653	(556)
Realized gains recognized in net income	(139)	(122)	(69)
OCI	915	531	(625)
AOCI, balance at the end of the period	3,540	2,625	2,094
Accumulated Other Comprehensive Income, Income Tax
AOCI, balance at the beginning of the period	908	722	942
OCI before realized gains recognized in net income	366	229	(196)
Realized gains recognized in net income	(49)	(43)	(24)
OCI	317	186	(220)
AOCI, balance at the end of the period	733	908	722
Accumulated Other Comprehensive Income, Net of Tax
AOCI, balance at the beginning of the period	1,717	1,372	1,777
OCI before realized gains recognized in net income	688	424	(360)
Realized gains recognized in net income	(90)	(79)	(45)
OCI	598	345	(405)
AOCI, balance at the end of the period	2,807	1,717	1,372
Accumulated Defined Benefit Plans Adjustment
Accumulated Other Comprehensive Income, Before Tax
AOCI, balance at the beginning of the period	(26)	(42)	(36)
OCI before realized gains recognized in net income	12	13	(12)
Realized gains recognized in net income	2	3	6
OCI	14	16	(6)
AOCI, balance at the end of the period	(12)	(26)	(42)
Accumulated Other Comprehensive Income, Income Tax
AOCI, balance at the beginning of the period	(8)	(14)	(12)
OCI before realized gains recognized in net income	6	5	(5)
Realized gains recognized in net income	1	1	3
OCI	7	6	(2)
AOCI, balance at the end of the period	(1)	(8)	(14)
Accumulated Other Comprehensive Income, Net of Tax
AOCI, balance at the beginning of the period	(18)	(28)	(24)
OCI before realized gains recognized in net income	6	8	(7)
Realized gains recognized in net income	1	2	3
OCI	7	10	(4)
AOCI, balance at the end of the period	(11)	(18)	(28)
Accumulated Net Unrealized Gain (Loss) on Deferred Costs, Reserves And Other
Accumulated Other Comprehensive Income, Before Tax
AOCI, balance at the beginning of the period	(9)	1	(12)
OCI before realized gains recognized in net income	8	(8)	14
Realized gains recognized in net income	(9)	(2)	(1)
OCI	(1)	(10)	13
AOCI, balance at the end of the period	(10)	(9)	1
Accumulated Other Comprehensive Income, Income Tax
AOCI, balance at the beginning of the period	(3)	1	(3)
OCI before realized gains recognized in net income	5	(3)	5
Realized gains recognized in net income	(4)	(1)	(1)
OCI	1	(4)	4
AOCI, balance at the end of the period	(2)	(3)	1
Accumulated Other Comprehensive Income, Net of Tax
AOCI, balance at the beginning of the period	(6)	0	(9)
OCI before realized gains recognized in net income	3	(5)	9
Realized gains recognized in net income	(5)	(1)	0
OCI	(2)	(6)	9
AOCI, balance at the end of the period	(8)	(6)	0
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income, Before Tax
AOCI, balance at the beginning of the period	2,590	2,053	2,671
Investments OCI	915	531	(625)
Pension obligations OCI	14	16	(6)
Life deferred acquisition costs, life policy reserves and other OCI	(1)	(10)	13
Total OCI	928	537	(618)
AOCI, balance at the end of the period	3,518	2,590	2,053
Accumulated Other Comprehensive Income, Income Tax
AOCI, balance at the beginning of the period	897	709	927
Investments OCI	317	186	(220)
Pension obligations OCI	7	6	(2)
Life deferred acquisition costs, life policy reserves and other OCI	1	(4)	4
Total OCI	325	188	(218)
AOCI, balance at the end of the period	730	897	709
Accumulated Other Comprehensive Income, Net of Tax
AOCI, balance at the beginning of the period	1,693	1,344	1,744
Investments OCI	598	345	(405)
Pension obligations OCI	7	10	(4)
Life deferred acquisition costs, life policy reserves and other OCI	(2)	(6)	9
Total OCI	603	349	(400)
AOCI, balance at the end of the period	2,788	1,693	1,344
New Accounting Pronouncement, Early Adoption, Effect | Accounting Standards Update 2018-02 | Accumulated Net Unrealized Investment Gain (Loss)
Accumulated Other Comprehensive Income, Before Tax
Adjustment to reclassify certain tax effects from AOCI	0
Accumulated Other Comprehensive Income, Income Tax
Adjustment to reclassify certain tax effects from AOCI	(492)
Accumulated Other Comprehensive Income, Net of Tax
Adjustment to reclassify certain tax effects from AOCI	492
New Accounting Pronouncement, Early Adoption, Effect | Accounting Standards Update 2018-02 | Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income, Before Tax
Adjustment to reclassify certain tax effects from AOCI	0
Accumulated Other Comprehensive Income, Income Tax
Adjustment to reclassify certain tax effects from AOCI	(492)
Accumulated Other Comprehensive Income, Net of Tax
Adjustment to reclassify certain tax effects from AOCI	$ 492	$ 0	$ 0

Reinsurance Reinsurance (Writte

Reinsurance Reinsurance (Written Consolidated Property Casualty Insurance Premiums On Assumed and Ceded Business) (Details) - Property, Liability and Casualty Insurance Product Line [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Direct Premiums Written	$ 4,854	$ 4,646	$ 4,461
Assumed Premiums Written	125	103	77
Ceded Premiums Written	(139)	(169)	(177)
Premiums Written, Net, Property and Casualty	$ 4,840	$ 4,580	$ 4,361

Reinsurance (Earned Consolidate

Reinsurance (Earned Consolidated Property Casualty Insurance Premiums On Assumed And Ceded Business) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Direct earned premiums	$ 5,052	$ 4,857	$ 4,667
Assumed earned premiums	132	77	29
Ceded earned premiums	(230)	(224)	(216)
Property, Liability and Casualty Insurance Product Line [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Direct earned premiums	4,752	4,567	4,396
Assumed earned premiums	132	77	29
Ceded earned premiums	(162)	(162)	(154)
Net earned premiums	$ 4,722	$ 4,482	$ 4,271

Reinsurance (Incurred Consolida

Reinsurance (Incurred Consolidated Property Casualty Insurance Loss And Loss Expenses On Assumed And Ceded Business) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net incurred loss and loss expenses	$ 3,390	$ 3,107	$ 2,808
Property, Liability and Casualty Insurance Product Line [Member]
Direct incurred loss and loss expenses	2,961	2,874	2,596
Assumed incurred loss and loss expenses	113	43	12
Ceded incurred loss and loss expenses	64	(56)	(36)
Net incurred loss and loss expenses	$ 3,138	$ 2,861	$ 2,572

Reinsurance (Earned Life Insura

Reinsurance (Earned Life Insurance Premiums On Ceded Business) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Direct earned premiums	$ 5,052	$ 4,857	$ 4,667
Ceded earned premiums	(230)	(224)	(216)
Life Insurance Segment
Direct earned premiums	300	290	271
Ceded earned premiums	(68)	(62)	(62)
Net earned premiums	$ 232	$ 228	$ 209

Reinsurance (Life Insurance Con

Reinsurance (Life Insurance Contract Holders' Benefits Incurred On Ceded Business) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net incurred loss and loss expenses	$ 3,390	$ 3,107	$ 2,808
Life Insurance Segment
Direct contract holders' benefits incurred	319	303	292
Ceded contract holders' benefits incurred	(67)	(57)	(56)
Net incurred loss and loss expenses	$ 252	$ 246	$ 236

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reduction in net deferred tax liability due to change of corporate income tax rate	$ 495
Deferred tax benefit due to tax rate change	67.80%	(0.00%)	(0.00%)
Excess tax benefit, amount	$ 7
Excess tax benefit percent	1.00%
Income taxes paid, net	$ 18	$ 2	$ 0
Retained Earnings | Accounting Standards Update 2018-02 | New Accounting Pronouncement, Early Adoption, Effect
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Adjustment to reclassify certain tax effects from AOCI to retained earnings	(492)	0	0
Accumulated Other Comprehensive Income | Accounting Standards Update 2018-02 | New Accounting Pronouncement, Early Adoption, Effect
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Adjustment to reclassify certain tax effects from AOCI to retained earnings	$ 492	$ 0	$ 0

Income Taxes (Components Of Def

Income Taxes (Components Of Deferred Tax Assets And Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Loss and loss expense reserves	$ 123	$ 199
Unearned premiums	100	158
Investments	0	5
Other	27	52
Total gross deferred tax assets	250	414
Deferred tax liabilities:
Unrealized investment gains and other, net	740	907
Deferred acquisition costs	123	195
Life policy reserves	111	162
Investments	10	0
Other	11	15
Total gross deferred tax liabilities	995	1,279
Net deferred income tax liability	$ 745	$ 865

Income Taxes (Differences Betwe

Income Taxes (Differences Between The 35 Percent Statutory Income Tax Rate And Effective Income Tax Rate) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Tax at statutory rate:	$ 256	$ 284	$ 308
Tax at statutory rate (percentage):	35.00%	35.00%	35.00%
Increase (decrease) resulting from:
Tax-exempt income from municipal bonds	$ (36)	$ (34)	$ (33)
Dividend received exclusion	(34)	(33)	(32)
Deferred tax benefit due to tax rate change	(495)	0	0
Other	(6)	4	4
Total provision (benefit) for income taxes	$ (315)	$ 221	$ 247
Tax at statutory rate:
Tax-exempt income from municipal bonds (percentage)	(4.90%)	(4.20%)	(3.70%)
Dividend received exclusion (percentage)	(4.70%)	(4.10%)	(3.60%)
Deferred tax benefit due to tax rate change	(67.80%)	0.00%	0.00%
Other (percentage)	(0.80%)	0.50%	0.30%
Effective tax, percentage	(43.20%)	27.20%	28.00%

Net Income Per Common Share (Ca

Net Income Per Common Share (Calculations For Basic And Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Numerator:
Net income—basic and diluted	$ 642	$ 102	$ 100	$ 201	$ 100	$ 180	$ 123	$ 188	$ 1,045	$ 591	$ 634
Denominator:
Basic weighted-average common shares outstanding									164.2	164.5	164
Diluted weighted-average shares									166	166.5	165.6
Earnings per share:
Basic (in usd per share)	$ 3.92	$ 0.62	$ 0.61	$ 1.22	$ 0.61	$ 1.09	$ 0.75	$ 1.14	$ 6.36	$ 3.59	$ 3.87
Diluted (in usd per share)	$ 3.88	$ 0.61	$ 0.60	$ 1.21	$ 0.60	$ 1.08	$ 0.74	$ 1.13	$ 6.29	$ 3.55	$ 3.83
Number of anti-dilutive share-based awards									0.7	0.3	0.4
Stock Options
Denominator:
Effect of stock-based awards									1.1	1.1	1
Restricted Stock Units (RSUs)
Denominator:
Effect of stock-based awards									0.7	0.9	0.6

Employee Retirement Benefits (N

Employee Retirement Benefits (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2008	Dec. 31, 2018	Mar. 31, 2018
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block
Minimum participant age to elect				40 years
Employer discretionary contribution amount (less than $1 million for 2016 and 2015 in the CFC Top Hat Savings Plan)	$ 16	$ 14	$ 12
Requisite service period	3 years
Accrued employee benefit		$ 15
Actual return on plan assets	17.40%	16.60%
Amortization of actuarial loss	$ 1
Amortization of prior service cost less than $1 million	1
Pension plan assets at fair value	$ 345	$ 315	278
Domestic Equity Securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block
Allocation percentage of investments	80.00%
Domestic Equity Securities | Information Technology Sector
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block
Allocation percentage of investments	22.00%
Domestic Equity Securities | Financial Services Sector [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block
Allocation percentage of investments	22.00%
Domestic Equity Securities | Healthcare Sector
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block
Allocation percentage of investments	15.00%
Domestic Equity Securities | Consumer Discretionary Sector [Member] [Domain]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block
Allocation percentage of investments	13.00%
Domestic Equity Securities | Industrial Sector
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block
Allocation percentage of investments	12.00%
Domestic Equity Securities | All Remaining Sectors
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block
Allocation percentage of investments	10.00%
States, Municipalities and Political Subdivisions
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block
Allocation percentage of investments	9.00%
Domestic Corporate Debt Securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block
Allocation percentage of investments	11.00%
Cash and Cash Equivalents
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block
Pension plan assets at fair value	$ 18	$ 11
Maximum
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block
Matching contribution to defined contribution plan	6.00%
Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block
Percentage of increase decrease in discount rate	0.25%
Pension plan assets, shares	232,113	232,113
Pension plan assets, fair value	$ 17	$ 18
Shares sold during period		35,000
Cash dividends paid	$ 1	$ 1
Pension Plan | Benefit Obligations
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block
Percentage of increase decrease in discount rate	0.57%
Supplemental Employee Retirement Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block
Accrued employee benefit	$ 9
Percentage of increase decrease in discount rate	0.20%
Supplemental Employee Retirement Plan | Benefit Obligations
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block
Percentage of increase decrease in discount rate	0.49%
Top Hat Savings Plan - Mutual Funds and Common Equities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block
CFC Top Hat Savings Plan	$ 31	24
Subsequent Event | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block
Expected contribution by employer during 2018						$ 5
Forecast | Supplemental Employee Retirement Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block
Expected contribution by employer during 2018					$ 5
Top Hat | Top Hat Savings Plan - Mutual Funds and Common Equities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block
Employer discretionary contribution amount (less than $1 million for 2016 and 2015 in the CFC Top Hat Savings Plan)	1	1	$ 1
CFC Top Hat Savings Plan	$ 31	$ 24

Employee Retirement Benefits (W

Employee Retirement Benefits (Weighted-Average Assumptions Used) (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Benefit Obligations | Pension Plan
Schedule of Benefit Obligations Weighted Average Assumptions
Discount rate	3.73%	4.30%
Benefit Obligations | Pension Plan | Minimum
Schedule of Benefit Obligations Weighted Average Assumptions
Rate of compensation increase	2.75%	2.75%
Benefit Obligations | Pension Plan | Maximum
Schedule of Benefit Obligations Weighted Average Assumptions
Rate of compensation increase	3.25%	3.25%
Benefit Obligations | Supplemental Employee Retirement Plan
Schedule of Benefit Obligations Weighted Average Assumptions
Discount rate	3.61%	4.10%
Benefit Obligations | Supplemental Employee Retirement Plan | Minimum
Schedule of Benefit Obligations Weighted Average Assumptions
Rate of compensation increase	2.75%	2.75%
Benefit Obligations | Supplemental Employee Retirement Plan | Maximum
Schedule of Benefit Obligations Weighted Average Assumptions
Rate of compensation increase	3.25%	3.25%
Net Periodic Benefit Cost | Pension Plan
Schedule of Benefit Obligations Weighted Average Assumptions
Discount rate	4.30%	4.55%	4.25%
Expected return on plan assets	7.25%	7.25%	7.25%
Net Periodic Benefit Cost | Pension Plan | Minimum
Schedule of Benefit Obligations Weighted Average Assumptions
Rate of compensation increase	2.75%	2.75%	2.75%
Net Periodic Benefit Cost | Pension Plan | Maximum
Schedule of Benefit Obligations Weighted Average Assumptions
Rate of compensation increase	3.25%	3.25%	3.25%
Net Periodic Benefit Cost | Supplemental Employee Retirement Plan
Schedule of Benefit Obligations Weighted Average Assumptions
Discount rate	4.10%	4.30%	4.05%
Net Periodic Benefit Cost | Supplemental Employee Retirement Plan | Minimum
Schedule of Benefit Obligations Weighted Average Assumptions
Rate of compensation increase	2.75%	2.75%	2.75%
Net Periodic Benefit Cost | Supplemental Employee Retirement Plan | Maximum
Schedule of Benefit Obligations Weighted Average Assumptions
Rate of compensation increase	3.25%	3.25%	3.25%

Employee Retirement Benefits (B

Employee Retirement Benefits (Benefit Obligation Activity Using An Actuarial Measurement Date For Qualified Plan And SERP) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Change in projected benefit obligation:
Benefit obligation, January 1	$ 340	$ 323
Service cost	11	11	$ 12
Interest cost	14	14	14
Actuarial loss	20	13
Benefits paid	(34)	(21)
Projected benefit obligation, December 31	351	340	323
Change in plan assets:
Fair value of plan assets, January 1	315	278
Actual return on plan assets	52	45
Employer contribution	12	13
Benefits paid	(34)	(21)
Fair value of plan assets, December 31	345	315	$ 278
Unfunded status:
Funded status, December 31	(6)	(25)
Accumulated benefit obligation	$ 322	$ 309

Employee Retirement Benefits (R

Employee Retirement Benefits (Reconciliation Of The Funded Status For Qualified Plan And SERP) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Retirement Benefits [Abstract]
Other liabilities	$ (6)	$ (25)
Total	(6)	(25)
Pension amounts recognized in accumulated other comprehensive income:
Net actuarial loss	12	26
Prior service cost	0	0
Total	$ 12	$ 26

Employee Retirement Benefits (C

Employee Retirement Benefits (Components Of Net Periodic Benefit Cost As Well As Other Changes In Plan Assets And Benefit Obligations Recognized In Other Comprehensive Income For Qualified Plan And SERP) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Retirement Benefits [Abstract]
Service cost	$ 11	$ 11	$ 12
Interest cost	14	14	14
Expected return on plan assets	(21)	(19)	(18)
Amortization of actuarial loss and prior service cost	2	3	6
Other	1	0	1
Net periodic benefit cost	7	9	15
Current year actuarial (gain) loss	(11)	(13)	13
Amortization of actuarial loss	(3)	(2)	(6)
Amortization of prior service cost	0	(1)	(1)
Total recognized in other comprehensive (income) loss	(14)	(16)	6
Total recognized in net periodic benefit cost and other comprehensive (income) loss	$ (7)	$ (7)	$ 21

Employee Retirement Benefits (F

Employee Retirement Benefits (Fair Value Hierarchy Of Assets Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Schedule of Pension and Other Postretirment Plan Assets by Fair Value
Available for sale securities, debt securities	$ 10,699	$ 10,085
Available for sale securities, equity securities	6,249	5,334
Fixed Maturities
Schedule of Pension and Other Postretirment Plan Assets by Fair Value
Available for sale securities, debt securities	65	51
Fixed Maturities | States, Municipalities and Political Subdivisions
Schedule of Pension and Other Postretirment Plan Assets by Fair Value
Available for sale securities, debt securities	31	31
Fixed Maturities | Corporate Fixed Maturities
Schedule of Pension and Other Postretirment Plan Assets by Fair Value
Available for sale securities, debt securities	34	20
Equity Securities | Common Stock
Schedule of Pension and Other Postretirment Plan Assets by Fair Value
Available for sale securities, equity securities	262	253
Debt And Equity Securities
Schedule of Pension and Other Postretirment Plan Assets by Fair Value
Available for sale securities, equity securities	327	304
Level 1 | Fixed Maturities
Schedule of Pension and Other Postretirment Plan Assets by Fair Value
Available for sale securities, debt securities	0	0
Level 1 | Fixed Maturities | States, Municipalities and Political Subdivisions
Schedule of Pension and Other Postretirment Plan Assets by Fair Value
Available for sale securities, debt securities	0	0
Level 1 | Fixed Maturities | Corporate Fixed Maturities
Schedule of Pension and Other Postretirment Plan Assets by Fair Value
Available for sale securities, debt securities	0	0
Level 1 | Equity Securities | Common Stock
Schedule of Pension and Other Postretirment Plan Assets by Fair Value
Available for sale securities, equity securities	262	253
Level 1 | Debt And Equity Securities
Schedule of Pension and Other Postretirment Plan Assets by Fair Value
Available for sale securities, equity securities	262	253
Level 2 | Fixed Maturities
Schedule of Pension and Other Postretirment Plan Assets by Fair Value
Available for sale securities, debt securities	65	51
Level 2 | Fixed Maturities | States, Municipalities and Political Subdivisions
Schedule of Pension and Other Postretirment Plan Assets by Fair Value
Available for sale securities, debt securities	31	31
Level 2 | Fixed Maturities | Corporate Fixed Maturities
Schedule of Pension and Other Postretirment Plan Assets by Fair Value
Available for sale securities, debt securities	34	20
Level 2 | Equity Securities | Common Stock
Schedule of Pension and Other Postretirment Plan Assets by Fair Value
Available for sale securities, equity securities	0	0
Level 2 | Debt And Equity Securities
Schedule of Pension and Other Postretirment Plan Assets by Fair Value
Available for sale securities, debt securities	65	51
Level 3 | Fixed Maturities
Schedule of Pension and Other Postretirment Plan Assets by Fair Value
Available for sale securities, debt securities	0	0
Level 3 | Fixed Maturities | States, Municipalities and Political Subdivisions
Schedule of Pension and Other Postretirment Plan Assets by Fair Value
Available for sale securities, debt securities	0	0
Level 3 | Fixed Maturities | Corporate Fixed Maturities
Schedule of Pension and Other Postretirment Plan Assets by Fair Value
Available for sale securities, debt securities	0	0
Level 3 | Equity Securities | Common Stock
Schedule of Pension and Other Postretirment Plan Assets by Fair Value
Available for sale securities, equity securities	0	0
Level 3 | Debt And Equity Securities
Schedule of Pension and Other Postretirment Plan Assets by Fair Value
Available for sale securities, equity securities	$ 0	$ 0

Employee Retirement Benefits (E

Employee Retirement Benefits (Expected Future Benefit Payments For Qualified Plan And SERP) (Details) $ in Millions	Dec. 31, 2017USD ($)
Retirement Benefits [Abstract]
Expected future benefit payments, 2018	$ 26
Expected future benefit payments, 2019	24
Expected future benefit payments, 2020	25
Expected future benefit payments, 2021	29
Expected future benefit payments, 2022	26
Expected future benefit payments, 2023 - 2027	$ 146

Statutory Accounting Informat96

Statutory Accounting Information (Schedule Of Statutory Net Income And Statutory Surplus (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
The Cincinnati Insurance Company
Statutory Accounting Practices
SAP net income (loss)	$ 401	$ 434	$ 534
Capital and surplus	5,094	4,686
The Cincinnati Casualty Company
Statutory Accounting Practices
SAP net income (loss)	21	11	12
Capital and surplus	392	360
The Cincinnati Indemnity Company
Statutory Accounting Practices
SAP net income (loss)	4	4	3
Capital and surplus	100	93
The Cincinnati Specialty Underwriters Insurance Company
Statutory Accounting Practices
SAP net income (loss)	58	57	49
Capital and surplus	436	372
The Cincinnati Life Insurance Company
Statutory Accounting Practices
SAP net income (loss)	12	2	$ (11)
Capital and surplus	$ 195	$ 200

Transactions With Affliated Par

Transactions With Affliated Parties (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Related Party Transaction
Payment for commissions	$ 7	$ 7	$ 7
Earned premiums	4,954	4,710	4,480
Affiliated Parties
Related Party Transaction
Earned premiums	$ 45	$ 44	$ 42

Share-Based Associate Compens98

Share-Based Associate Compensation Plans (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)Peerscompensation_plansshares	Dec. 31, 2016USD ($)Peersshares	Dec. 31, 2015USD ($)Peersshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of peers in peer group | Peers	9	9	10
Number of equity compensation plans | compensation_plans	4
Share based compensation	$ 17	$ 15	$ 14
Tax benefit from compensation expense	9	8	6
Options exercised, intrinsic value	19	25	15
Options vested, intrinsic value	8	11	7
Unrecognized compensation costs related to non-vested awards	$ 28
Expected weighted-average period to recognize the unrecognized compensation costs related to non-vested awards	1 year 8 months 18 days
Maximum number of shares awarded to each full-time employee for their service | shares	10
Proceeds from stock options exercised	$ 13	21	24
Shares of common stock granted in period (in shares) | shares	706,000
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards exercise peirod	10 years
Awards vesting period	3 years
Proceeds from stock options exercised	$ 13	$ 21	$ 24
Shares repurchased | shares	96,030	186,097	292,414
Shares repurchased, value	$ 7	$ 13	$ 16
Weighted average remaining contractual term	8 years 8 months 8 days
Shares authorized to be granted under the shareholder-approved plans | shares	17,300,000
Shares available for future issuance under the plans | shares	11,300,000
Stock Options | Directors
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock granted in period (in shares) | shares	15,040
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate	2.83%		3.52%
Weighted-average expected term	2 years 10 months 21 days		2 years 10 months 18 days
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate	1.44%		0.99%
Performance Shares [Member] | Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards vesting period	3 years
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period Intrinsic Value Aggregate	$ 7	$ 6	$ 6
Performance Shares [Member] | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate		2.58%
Weighted-average expected term		2 years 5 months 9 days
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate		0.77%

Share-Based Associate Compens99

Share-Based Associate Compensation Plans (Assumptions Used In Grants Issued) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Stock Options
Weighted-average fair value of options granted during the period	$ 10.79	$ 13.21	$ 11.15
Stock Options | Minimum
Weighted-average expected term	8 years	8 years	8 years
Expected volatility	16.95%	24.88%	25.04%
Dividend yield	2.83%	2.58%	3.52%
Risk-free rates	2.33%	1.44%	1.94%
Stock Options | Maximum
Weighted-average expected term	8 years	8 years	9 years
Expected volatility	16.95%	25.75%	26.15%
Dividend yield	2.83%	3.12%	3.52%
Risk-free rates	2.33%	1.60%	2.01%
Performance Based Shares
Weighted-average expected term	2 years 10 months 21 days		2 years 10 months 18 days
Dividend yield	2.83%		3.52%
Risk-free rates	1.44%		0.99%
Performance Based Shares | Minimum
Weighted-average expected term		2 years 5 months 9 days
Expected volatility	15.75%	15.42%	13.78%
Dividend yield		2.58%
Risk-free rates		0.77%
Performance Based Shares | Maximum
Weighted-average expected term		2 years 10 months 18 days
Expected volatility	28.35%	33.64%	34.69%
Dividend yield		3.12%
Risk-free rates		0.87%

Share-Based Associate Compen100

Share-Based Associate Compensation Plans (Stock Option Information) (Details) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)$ / sharesshares
Shares
Outstanding at beginning of year (in shares) | shares	3,012
Granted (in shares) | shares	706
Exercised (in shares) | shares	(527)
Forfeited or expired (in shares) | shares	(125)
Outstanding at end of year (in shares) | shares	3,066
Options exercisable at end of period (in shares) | shares	2,072
Weighted-average exercise price
Outstanding at beginning of year (in dollars per share) | $ / shares	$ 42.12
Granted (in dollars per share) | $ / shares	70.70
Exercised (in dollars per share) | $ / shares	38.33
Forfeited or expired (in dollars per share) | $ / shares	47.07
Outstanding at end of year (in dollars per share) | $ / shares	49.14
Options exercisable at end of period (in dollars per share) | $ / shares	$ 40.69
Aggregate intrinsic value
Outstanding at end of year | $	$ 79
Options exercisable at end of period | $	$ 71
Weighted-average remaining contractual life
Outstanding option shares at December 31, 2017	5 years 221 days
Options exercisable at end of period	4 years 47 days

Share-Based Associate Compen101

Share-Based Associate Compensation Plans (Restricted Stock Unit Information) (Details) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)peers_exceededPeers$ / sharesshares	Dec. 31, 2016USD ($)peers_exceededPeers$ / sharesshares	Dec. 31, 2015USD ($)peers_exceededPeers
Reconciliation of Restricted Stock Activity [Line Items]
Number of peers exceeded | peers_exceeded	5	5	4
Number of peers | Peers	9	9	10
Restricted Stock Units (RSUs) | Service Based Shares
Nonvested shares
Beginning balance (in shares)	888,000
Granted (in shares)	292,000
Vested (in shares)	(311,000)
Forfeited or canceled (in shares)	(26,000)
Ending balance (in shares)	843,000	888,000
Weighted-average grant-date fair value
Beginning balance (in dollars per share) | $ / shares	$ 48.59
Granted (in dollars per share) | $ / shares	65.16
Vested (in dollars per share) | $ / shares	43.05
Forfeited or canceled (in dollars per share) | $ / shares	55.59
Ending balance (in dollars per share) | $ / shares	$ 56.16	$ 48.59
Restricted Stock Units (RSUs) | Performance Based Shares
Nonvested shares
Beginning balance (in shares)	236,000
Granted (in shares)	57,000
Vested (in shares)	(87,000)
Forfeited or canceled (in shares)	0
Ending balance (in shares)	206,000	236,000
Weighted-average grant-date fair value
Beginning balance (in dollars per share) | $ / shares	$ 49.64
Granted (in dollars per share) | $ / shares	43.26
Vested (in dollars per share) | $ / shares	36.73
Forfeited or canceled (in dollars per share) | $ / shares	0
Ending balance (in dollars per share) | $ / shares	$ 53.35	$ 49.64
Restricted Stock Units (RSUs) | Service Based Shares
Reconciliation of Restricted Stock Activity [Line Items]
Awards vesting period	3 years
Awards other than options vested, intrinsic value | $	$ 23	$ 23	$ 26
Restricted Stock Units (RSUs) | Performance Based Shares
Reconciliation of Restricted Stock Activity [Line Items]
Awards vesting period	3 years
Awards other than options vested, intrinsic value | $	$ 7	$ 6	$ 6
share based performance metric for performance shares	3 years
Risk-free rates, minimum	0.00%	0.00%	0.00%
Risk-free rates, maximum	200.00%	200.00%	200.00%
Shares, Issued	87,228	25,461

Segment Information (Details)

Segment Information (Details) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017USD ($)	Sep. 30, 2017USD ($)	Jun. 30, 2017USD ($)	Mar. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Sep. 30, 2016USD ($)	Jun. 30, 2016USD ($)	Mar. 31, 2016USD ($)	Dec. 31, 2017USD ($)segmentindustry	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Segment Reporting Information
Earned premiums									$ 4,954	$ 4,710	$ 4,480
Total revenues	$ 1,411	$ 1,412	$ 1,386	$ 1,523	$ 1,312	$ 1,402	$ 1,371	$ 1,364	5,732	5,449	5,142
Other Income									5	5	7
Fees and Commissions									16	15	13
Net Investment Income									609	595	572
Realized investment gains, net									148	124	70
Income before income taxes	197	$ 129	$ 128	$ 276	128	$ 253	$ 166	$ 265	730	812	881
Identifiable assets	21,843				20,386				$ 21,843	20,386
Number of Industries Operated In | industry									2
Number of Insurance Segments | segment									4
Life Insurance Segment
Segment Reporting Information
Earned premiums									$ 232	228	209
Identifiable assets	1,409				1,366				1,409	1,366
Investments Segment
Segment Reporting Information
Identifiable assets	17,112				15,569				17,112	15,569
Consolidated Property and Casualty Insurance Entity
Segment Reporting Information
Identifiable assets	2,863				2,967				2,863	2,967
Corporate and Other [Member]
Segment Reporting Information
Identifiable assets	$ 459				$ 484				459	484
Operating Segments | Commercial Insurance
Segment Reporting Information
Earned premiums									3,165	3,089	2,996
Total revenues									3,170	3,094	3,000
Fees and Commissions									5	5	4
Income before income taxes									119	184	345
Operating Segments | Commercial Insurance | Commercial Casualty Line
Segment Reporting Information
Earned premiums									1,072	1,050	1,010
Operating Segments | Commercial Insurance | Commercial Property Line
Segment Reporting Information
Earned premiums									903	867	815
Operating Segments | Commercial Insurance | Commercial Auto Line
Segment Reporting Information
Earned premiums									634	594	561
Operating Segments | Commercial Insurance | Workers' Compensation Line
Segment Reporting Information
Earned premiums									335	354	367
Operating Segments | Commercial Insurance | Other Commercial Lines
Segment Reporting Information
Earned premiums									221	224	243
Operating Segments | Personal Insurance
Segment Reporting Information
Earned premiums									1,241	1,161	1,097
Total revenues									1,246	1,165	1,100
Fees and Commissions									5	4	3
Income before income taxes									(32)	(12)	(12)
Operating Segments | Personal Insurance | Personal Auto
Segment Reporting Information
Earned premiums									582	543	506
Operating Segments | Personal Insurance | Home Owner Line
Segment Reporting Information
Earned premiums									518	486	463
Operating Segments | Personal Insurance | Other Personal Lines
Segment Reporting Information
Earned premiums									141	132	128
Operating Segments | Excess and Surplus Lines Insurance
Segment Reporting Information
Earned premiums									209	183	168
Total revenues									210	184	169
Fees and Commissions									1	1	1
Income before income taxes									61	62	51
Operating Segments | Life Insurance Segment
Segment Reporting Information
Earned premiums									232	228	209
Total revenues									237	233	214
Fees and Commissions									5	5	5
Income before income taxes									(1)	1	(2)
Operating Segments | Investments Segment
Segment Reporting Information
Total revenues									757	719	642
Net Investment Income									609	595	572
Realized investment gains, net									148	124	70
Income before income taxes									664	629	556
Corporate, Non-Segment [Member]
Segment Reporting Information
Total revenues									112	54	17
Corporate, Non-Segment [Member] | Reinsurance assumed and other non segment [Member]
Segment Reporting Information
Earned premiums									107	49	10
Corporate, Non-Segment [Member] | Corporate and Other [Member]
Segment Reporting Information
Other Income									5	5	7
Income before income taxes									$ (81)	$ (52)	$ (57)

Quarterly Supplementary Data (D

Quarterly Supplementary Data (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 1,411	$ 1,412	$ 1,386	$ 1,523	$ 1,312	$ 1,402	$ 1,371	$ 1,364	$ 5,732	$ 5,449	$ 5,142
Income before income taxes	197	129	128	276	128	253	166	265	730	812	881
Net Income (Loss) Attributable to Parent	$ 642	$ 102	$ 100	$ 201	$ 100	$ 180	$ 123	$ 188	$ 1,045	$ 591	$ 634
Basic (in usd per share)	$ 3.92	$ 0.62	$ 0.61	$ 1.22	$ 0.61	$ 1.09	$ 0.75	$ 1.14	$ 6.36	$ 3.59	$ 3.87
Diluted (in usd per share)	$ 3.88	$ 0.61	$ 0.60	$ 1.21	$ 0.60	$ 1.08	$ 0.74	$ 1.13	$ 6.29	$ 3.55	$ 3.83

Summary of Investments Other104

Summary of Investments Other Than Investments In Related Parties (Details)1 $ in Millions	Dec. 31, 2017USD ($)
Summary Of Investments Other Than Investments In Related Parties Reportable Data
Cost or amortized cost	$ 13,511
Balance sheet	17,051
Fixed Maturities
Summary Of Investments Other Than Investments In Related Parties Reportable Data
Cost or amortized cost	10,314
Fair value	10,699
Balance sheet	10,699
Equity Securities
Summary Of Investments Other Than Investments In Related Parties Reportable Data
Cost or amortized cost	3,094
Fair value	6,249
Balance sheet	6,249
Other than Securities Investment
Summary Of Investments Other Than Investments In Related Parties Reportable Data
Cost or amortized cost	103
Balance sheet	103
States, Municipalities and Political Subdivisions | Fixed Maturities
Summary Of Investments Other Than Investments In Related Parties Reportable Data
Cost or amortized cost	4,316
Fair value	4,465
Balance sheet	4,465
States, Municipalities and Political Subdivisions | Fixed Maturities | Cincinnati Financial Corporation
Summary Of Investments Other Than Investments In Related Parties Reportable Data
Cost or amortized cost	2
Fair value	2
Balance sheet	2
States, Municipalities and Political Subdivisions | Fixed Maturities | The Cincinnati Insurance Company
Summary Of Investments Other Than Investments In Related Parties Reportable Data
Cost or amortized cost	3,310
Fair value	3,421
Balance sheet	3,421
States, Municipalities and Political Subdivisions | Fixed Maturities | The Cincinnati Casualty Company
Summary Of Investments Other Than Investments In Related Parties Reportable Data
Cost or amortized cost	184
Fair value	190
Balance sheet	190
States, Municipalities and Political Subdivisions | Fixed Maturities | The Cincinnati Indemnity Company
Summary Of Investments Other Than Investments In Related Parties Reportable Data
Cost or amortized cost	44
Fair value	46
Balance sheet	46
States, Municipalities and Political Subdivisions | Fixed Maturities | The Cincinnati Life Insurance Company
Summary Of Investments Other Than Investments In Related Parties Reportable Data
Cost or amortized cost	306
Fair value	320
Balance sheet	320
States, Municipalities and Political Subdivisions | Fixed Maturities | The Cincinnati Specialty Underwriters Insurance Company
Summary Of Investments Other Than Investments In Related Parties Reportable Data
Cost or amortized cost	469
Fair value	485
Balance sheet	485
States, Municipalities and Political Subdivisions | Fixed Maturities | CSU Producers Resources Inc.
Summary Of Investments Other Than Investments In Related Parties Reportable Data
Cost or amortized cost	1
Fair value	1
Balance sheet	1
United States Government | Fixed Maturities
Summary Of Investments Other Than Investments In Related Parties Reportable Data
Cost or amortized cost	31
Fair value	31
Balance sheet	31
United States Government | Fixed Maturities | The Cincinnati Insurance Company
Summary Of Investments Other Than Investments In Related Parties Reportable Data
Cost or amortized cost	28
Fair value	28
Balance sheet	28
United States Government | Fixed Maturities | The Cincinnati Casualty Company
Summary Of Investments Other Than Investments In Related Parties Reportable Data
Cost or amortized cost	2
Fair value	2
Balance sheet	2
United States Government | Fixed Maturities | The Cincinnati Indemnity Company
Summary Of Investments Other Than Investments In Related Parties Reportable Data
Cost or amortized cost	1
Fair value	1
Balance sheet	1
Government-Sponsored Enterprises | Fixed Maturities
Summary Of Investments Other Than Investments In Related Parties Reportable Data
Cost or amortized cost	257
Fair value	254
Balance sheet	254
Government-Sponsored Enterprises | Fixed Maturities | The Cincinnati Life Insurance Company
Summary Of Investments Other Than Investments In Related Parties Reportable Data
Cost or amortized cost	257
Fair value	254
Balance sheet	254
Foreign Government | Fixed Maturities
Summary Of Investments Other Than Investments In Related Parties Reportable Data
Cost or amortized cost	10
Fair value	10
Balance sheet	10
Foreign Government | Fixed Maturities | The Cincinnati Insurance Company
Summary Of Investments Other Than Investments In Related Parties Reportable Data
Cost or amortized cost	10
Fair value	10
Balance sheet	10
Common Stock | Equity Securities
Summary Of Investments Other Than Investments In Related Parties Reportable Data
Cost or amortized cost	2,918
Fair value	6,039
Balance sheet	6,039
Common Stock | Equity Securities | Cincinnati Financial Corporation
Summary Of Investments Other Than Investments In Related Parties Reportable Data
Cost or amortized cost	1,158
Fair value	2,274
Balance sheet	2,274
Common Stock | Equity Securities | The Cincinnati Insurance Company
Summary Of Investments Other Than Investments In Related Parties Reportable Data
Cost or amortized cost	1,615
Fair value	3,479
Balance sheet	3,479
Common Stock | Equity Securities | The Cincinnati Casualty Company
Summary Of Investments Other Than Investments In Related Parties Reportable Data
Cost or amortized cost	56
Fair value	118
Balance sheet	118
Common Stock | Equity Securities | The Cincinnati Indemnity Company
Summary Of Investments Other Than Investments In Related Parties Reportable Data
Cost or amortized cost	13
Fair value	25
Balance sheet	25
Common Stock | Equity Securities | The Cincinnati Specialty Underwriters Insurance Company
Summary Of Investments Other Than Investments In Related Parties Reportable Data
Cost or amortized cost	61
Fair value	120
Balance sheet	120
Common Stock | Equity Securities | CSU Producers Resources Inc.
Summary Of Investments Other Than Investments In Related Parties Reportable Data
Cost or amortized cost	15
Fair value	23
Balance sheet	23
Nonredeemable Preferred Stock | Equity Securities
Summary Of Investments Other Than Investments In Related Parties Reportable Data
Cost or amortized cost	176
Fair value	210
Balance sheet	210
Nonredeemable Preferred Stock | Equity Securities | Cincinnati Financial Corporation
Summary Of Investments Other Than Investments In Related Parties Reportable Data
Cost or amortized cost	1
Fair value	1
Balance sheet	1
Nonredeemable Preferred Stock | Equity Securities | The Cincinnati Insurance Company
Summary Of Investments Other Than Investments In Related Parties Reportable Data
Cost or amortized cost	170
Fair value	200
Balance sheet	200
Nonredeemable Preferred Stock | Equity Securities | The Cincinnati Life Insurance Company
Summary Of Investments Other Than Investments In Related Parties Reportable Data
Cost or amortized cost	5
Fair value	9
Balance sheet	9
All Other Corporate Bonds | Fixed Maturities
Summary Of Investments Other Than Investments In Related Parties Reportable Data
Cost or amortized cost	5,700
Fair value	5,939
Balance sheet	5,939
All Other Corporate Bonds | Fixed Maturities | Cincinnati Financial Corporation
Summary Of Investments Other Than Investments In Related Parties Reportable Data
Cost or amortized cost	33
Fair value	35
Balance sheet	35
All Other Corporate Bonds | Fixed Maturities | The Cincinnati Insurance Company
Summary Of Investments Other Than Investments In Related Parties Reportable Data
Cost or amortized cost	2,644
Fair value	2,747
Balance sheet	2,747
All Other Corporate Bonds | Fixed Maturities | The Cincinnati Casualty Company
Summary Of Investments Other Than Investments In Related Parties Reportable Data
Cost or amortized cost	99
Fair value	104
Balance sheet	104
All Other Corporate Bonds | Fixed Maturities | The Cincinnati Indemnity Company
Summary Of Investments Other Than Investments In Related Parties Reportable Data
Cost or amortized cost	28
Fair value	29
Balance sheet	29
All Other Corporate Bonds | Fixed Maturities | The Cincinnati Life Insurance Company
Summary Of Investments Other Than Investments In Related Parties Reportable Data
Cost or amortized cost	2,758
Fair value	2,880
Balance sheet	2,880
All Other Corporate Bonds | Fixed Maturities | The Cincinnati Specialty Underwriters Insurance Company
Summary Of Investments Other Than Investments In Related Parties Reportable Data
Cost or amortized cost	137
Fair value	143
Balance sheet	143
All Other Corporate Bonds | Fixed Maturities | CSU Producers Resources Inc.
Summary Of Investments Other Than Investments In Related Parties Reportable Data
Cost or amortized cost	1
Fair value	1
Balance sheet	1
Policy Loans | Other than Securities Investment | The Cincinnati Life Insurance Company
Summary Of Investments Other Than Investments In Related Parties Reportable Data
Cost or amortized cost	31
Fair value	0
Balance sheet	31
Limited Partnership | Other than Securities Investment | The Cincinnati Life Insurance Company
Summary Of Investments Other Than Investments In Related Parties Reportable Data
Cost or amortized cost	6
Balance sheet	6
Limited Partnership | Other than Securities Investment | Cincinnati Financial Corporation
Summary Of Investments Other Than Investments In Related Parties Reportable Data
Cost or amortized cost	29
Fair value	0
Balance sheet	29
Real Estate [Member] | Other than Securities Investment | Cincinnati Financial Corporation
Summary Of Investments Other Than Investments In Related Parties Reportable Data
Cost or amortized cost	6
Balance sheet	6
Real Estate [Member] | Other than Securities Investment | The Cincinnati Life Insurance Company
Summary Of Investments Other Than Investments In Related Parties Reportable Data
Cost or amortized cost	31
Balance sheet	$ 31

Condensed Financial Statemen105

Condensed Financial Statements Of Parent Company Condensed Statements Of Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash Flows From Operating Activities
Net Income	$ 642	$ 102	$ 100	$ 201	$ 100	$ 180	$ 123	$ 188	$ 1,045	$ 591	$ 634
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization									55	48	52
Realized investment gains, net									(148)	(124)	(70)
Changes in:
Investment income receivable									0	(5)	(6)
Current income tax receivable/payable									67	(35)	(18)
Other assets									(43)	34	(39)
Other liabilities									24	61	55
Net cash provided by operating activities									1,052	1,115	1,075
Cash Flows From Investing Activities
Sale of fixed maturities									23	15	43
Call or maturity of fixed maturities									1,172	1,511	1,199
Sale of equity securities									523	465	342
Purchase of fixed maturities									(1,723)	(1,994)	(1,722)
Purchase of equity securities									(513)	(439)	(493)
Investment in buildings and equipment									(16)	(13)	(10)
Change in other invested assets, net									(15)	(14)	1
Net cash used in investing activities									(558)	(456)	(624)
Cash Flows From Financing Activities
Changes in note payable									4	(15)	(14)
Payment of cash dividends to shareholders									(400)	(306)	(366)
Shares acquired - share repurchase authorization									(92)	(39)	(53)
Proceeds from stock options exercised									13	21	24
Other									(54)	(32)	(28)
Net cash used in financing activities									(614)	(426)	(498)
Net change in cash and cash equivalents									(120)	233	(47)
Cash and cash equivalents at beginning of year				777				544	777	544	591
Cash and cash equivalents at end of year	657				777				657	777	544
Cincinnati Financial Corporation
Cash Flows From Operating Activities
Net Income									1,045	591	634
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization									7	6	7
Realized investment gains, net									(28)	(27)	19
Dividends from subsidiaries									465	475	447
Changes in:
Increase in equity of subsidiaries									(859)	(566)	(642)
Investment income receivable									0	(2)	0
Current federal income taxes									(5)	(4)	(7)
Current income tax receivable/payable									(150)	8	(10)
Other assets									(20)	(4)	(3)
Other liabilities									15	(1)	13
Intercompany receivable for operations									13	20	16
Net cash provided by operating activities									483	496	474
Cash Flows From Investing Activities
Call or maturity of fixed maturities									14	5	8
Sale of equity securities									230	135	54
Purchase of fixed maturities									(2)	0	0
Purchase of equity securities									(293)	(175)	(110)
Investment in buildings and equipment									(3)	(2)	0
Change in other invested assets, net									0	6	1
Net cash used in investing activities									(54)	(31)	(47)
Cash Flows From Financing Activities
Payment of cash dividends to shareholders									(400)	(306)	(366)
Shares acquired - share repurchase authorization									(92)	(39)	(53)
Proceeds from stock options exercised									13	21	24
Other									1	1	2
Net cash used in financing activities									(478)	(323)	(393)
Net change in cash and cash equivalents									(49)	142	34
Cash and cash equivalents at beginning of year				$ 248				$ 106	248	106	72
Cash and cash equivalents at end of year	$ 199				$ 248				$ 199	$ 248	$ 106

Condensed Financial Statemen106

Condensed Financial Statements Of Parent Company Condensed Balance Sheets (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Condensed Financial Statements, Captions
Fixed maturities, amortized cost	$ 10,314	$ 9,799
Investments
Fixed maturities, at fair value (amortized cost: 2017—$35; 2016—$46)	10,699	10,085
Equity securities, at fair value (cost: 2017—$1,159; 2016—$1,084)	6,249	5,334
Other invested assets	103	81
Total investments	17,051	15,500
Cash and cash equivalents	657	777	$ 544	$ 591
Investment income receivable	134	134
Land, building and equipment, net, for company use (accumulated depreciation: 2017—$115; 2016—$111)	185	183
Other assets	216	198
Total assets	21,843	20,386
Liabilities
Deferred federal income tax	995	1,279
Long-term debt	787	787
Other liabilities	792	786
Total liabilities	13,600	13,326
Shareholders' Equity
Common stock	397	397
Paid-in capital	1,265	1,252
Retained earnings	5,180	5,037
Accumulated other comprehensive income	2,788	1,693
Treasury stock at cost	(1,387)	(1,319)
Total shareholders' equity	8,243	7,060	6,427
Total liabilities and shareholders' equity	21,843	20,386
Equity securities, cost	3,094	2,995
Cincinnati Financial Corporation
Condensed Financial Statements, Captions
Fixed maturities, amortized cost	35	46
Investments
Fixed maturities, at fair value (amortized cost: 2017—$35; 2016—$46)	37	52
Equity securities, at fair value (cost: 2017—$1,159; 2016—$1,084)	2,275	1,833
Other invested assets	35	29
Total investments	2,347	1,914
Cash and cash equivalents	199	248	$ 106	$ 72
Equity in net assets of subsidiaries	6,542	5,790
Investment income receivable	8	8
Land, building and equipment, net, for company use (accumulated depreciation: 2017—$115; 2016—$111)	130	132
Income tax receivable	15	10
Other assets	52	35
Due from subsidiaries	107	106
Total assets	9,400	8,243
Liabilities
Dividends declared but unpaid	82	79
Deferred federal income tax	234	252
Long-term debt	787	787
Other liabilities	54	65
Total liabilities	1,157	1,183
Shareholders' Equity
Common stock	397	397
Paid-in capital	1,265	1,252
Retained earnings	5,180	5,037
Accumulated other comprehensive income	2,788	1,693
Treasury stock at cost	(1,387)	(1,319)
Total shareholders' equity	8,243	7,060
Total liabilities and shareholders' equity	9,400	8,243
Equity securities, cost	$ 1,159	$ 1,084

Condensed Financial Statemen107

Condensed Financial Statements Of Parent Company Condensed Balance Sheets (Parenthetical) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Condensed Financial Statements, Captions
Fixed maturities, amortized cost	$ 10,314	$ 9,799
Equity securities, cost	3,094	2,995
Land, building and equipment, accumulated depreciation	253	237
Cincinnati Financial Corporation
Condensed Financial Statements, Captions
Fixed maturities, amortized cost	35	46
Equity securities, cost	1,159	1,084
Land, building and equipment, accumulated depreciation	$ 115	$ 111

Condensed Financial Statemen108

Condensed Financial Statements Of Parent Company Condensed Statements Of Income (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues
Investment income, net of expenses									$ 609	$ 595	$ 572
Realized investment gains, net									148	124	70
Other revenues									5	5	7
Total revenues	$ 1,411	$ 1,412	$ 1,386	$ 1,523	$ 1,312	$ 1,402	$ 1,371	$ 1,364	5,732	5,449	5,142
Expenses
Interest expense									53	53	53
Other expenses									13	12	13
Total expenses									5,002	4,637	4,261
Income (Loss) Before Income Taxes and Earnings of Subsidiaries	197	129	128	276	128	253	166	265	730	812	881
Benefit for income taxes									(315)	221	247
Net Income	$ 642	$ 102	$ 100	$ 201	$ 100	$ 180	$ 123	$ 188	1,045	591	634
Cincinnati Financial Corporation
Revenues
Investment income, net of expenses									62	56	53
Realized investment gains, net									28	27	(19)
Other revenues									15	15	15
Total revenues									105	98	49
Expenses
Interest expense									52	52	52
Other expenses									28	27	28
Total expenses									80	79	80
Income (Loss) Before Income Taxes and Earnings of Subsidiaries									25	19	(31)
Benefit for income taxes									(161)	(6)	(23)
Net Income (Loss) Before Earnings of Subsidiaries									186	25	(8)
Increase in equity of subsidiaries									859	566	642
Net Income									$ 1,045	$ 591	$ 634

Condensed Financial Statemen109

Condensed Financial Statements Of Parent Company Condensed Statements Of Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Financial Statements, Captions
Net Income	$ 642	$ 102	$ 100	$ 201	$ 100	$ 180	$ 123	$ 188	$ 1,045	$ 591	$ 634
Unrealized gains and (losses) on investments available for sale									598	345	(405)
Unrealized gains and (losses) on investments available for sale, investments held by subsidiaries and other									914	521	(612)
Amortization of pension actuarial gains (losses) and prior service cost									14	16	(6)
OCI									928	537	(618)
Income taxes on above of other comprehensive income (loss)									325	188	(218)
Other comprehensive income (loss), net of tax									603	349	(400)
Comprehensive Income									1,648	940	234
Cincinnati Financial Corporation
Condensed Financial Statements, Captions
Net Income									1,045	591	634
Unrealized gains and (losses) on investments available for sale									391	221	(111)
Unrealized gains and (losses) on investments held by subsidiaries									672	434	(444)
Reclassification adjustment for (gains) and losses included in net income									(28)	(27)	19
Reclassification adjustment for (gains) included in net income on subsidiaries									(120)	(97)	(89)
Unrealized (losses) and gains on other									(2)	(6)	0
Unrealized gains and (losses) on other subsidiaries									$ 1	$ (4)	$ 13

Supplementary Insurance Info110

Supplementary Insurance Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Supplementary Insurance Information, by Segment
Deferred policy acquisition costs	$ 670	$ 637	$ 616
Gross future policy benefits, losses, claims and expense losses	7,972	7,728	7,265
Gross unearned premium	2,404	2,307	2,201
Other policy claims and benefits payable	30	28	36
Earned premiums	4,954	4,710	4,480
Investment income, net of expenses	547	539	518
Benefits, claims losses and settlement expense	3,390	3,107	2,808
Amortization of deferred policy acquisition costs	913	863	829
Underwriting, acquisition and insurance expenses	633	602	558
Net written premiums	4,843	4,582	4,363
Commercial Insurance
Supplementary Insurance Information, by Segment
Deferred policy acquisition costs	284	271	264
Gross future policy benefits, losses, claims and expense losses	4,236	4,179	3,925
Gross unearned premium	1,548	1,510	1,472
Earned premiums	3,165	3,089	2,996
Benefits, claims losses and settlement expense	2,042	1,928	1,708
Amortization of deferred policy acquisition costs	590	570	552
Underwriting, acquisition and insurance expenses	419	412	395
Net written premiums	3,202	3,122	3,025
Personal Insurance
Supplementary Insurance Information, by Segment
Deferred policy acquisition costs	121	110	103
Gross future policy benefits, losses, claims and expense losses	587	569	498
Gross unearned premium	683	629	593
Earned premiums	1,241	1,161	1,097
Benefits, claims losses and settlement expense	918	840	789
Amortization of deferred policy acquisition costs	225	209	210
Underwriting, acquisition and insurance expenses	135	128	113
Net written premiums	1,294	1,198	1,128
Excess and Surplus Lines Insurance
Supplementary Insurance Information, by Segment
Deferred policy acquisition costs	17	16	15
Gross future policy benefits, losses, claims and expense losses	264	241	227
Gross unearned premium	105	93	87
Earned premiums	209	183	168
Benefits, claims losses and settlement expense	86	68	70
Amortization of deferred policy acquisition costs	35	31	28
Underwriting, acquisition and insurance expenses	28	23	20
Net written premiums	219	189	175
Reinsurance assumed and other non segment [Member]
Supplementary Insurance Information, by Segment
Deferred policy acquisition costs	16	11	6
Gross future policy benefits, losses, claims and expense losses	132	46	10
Gross unearned premium	67	74	48
Earned premiums	107	49	10
Benefits, claims losses and settlement expense	92	25	5
Amortization of deferred policy acquisition costs	17	10	2
Underwriting, acquisition and insurance expenses	18	6	1
Net written premiums	125	71	33
Property, Liability and Casualty Insurance Product Line [Member]
Supplementary Insurance Information, by Segment
Deferred policy acquisition costs	438	408	388
Gross future policy benefits, losses, claims and expense losses	5,219	5,035	4,660
Gross unearned premium	2,403	2,306	2,200
Earned premiums	4,722	4,482	4,271
Investment income, net of expenses	392	384	368
Benefits, claims losses and settlement expense	3,138	2,861	2,572
Amortization of deferred policy acquisition costs	867	820	792
Underwriting, acquisition and insurance expenses	600	569	529
Net written premiums	4,840	4,580	4,361
Accident Health Insurance Segment [Member]
Supplementary Insurance Information, by Segment
Net written premiums	3	2	2
Life Insurance Segment
Supplementary Insurance Information, by Segment
Deferred policy acquisition costs	232	229	228
Gross future policy benefits, losses, claims and expense losses	2,753	2,693	2,605
Gross unearned premium	1	1	1
Other policy claims and benefits payable	30	28	36
Earned premiums	232	228	209
Investment income, net of expenses	155	155	150
Benefits, claims losses and settlement expense	252	246	236
Amortization of deferred policy acquisition costs	46	43	37
Underwriting, acquisition and insurance expenses	$ 33	$ 33	$ 29

Reinsurance (Details)

Reinsurance (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Gross amounts, life insurance in force	$ 99,888	$ 95,533	$ 91,451
Gross amounts	5,052	4,857	4,667
Ceded amounts to other companies, life insurance in force	38,711	38,724	38,716
Ceded amounts to other companies	230	224	216
Assumed amounts from other companies, life insurance in force	0	0	0
Assumed amounts from other companies	132	77	29
Net amounts, life insurance in force	61,177	56,808	52,735
Premiums Earned, Net	$ 4,954	$ 4,710	$ 4,480
Percentage of amounts assumed to net, life insurance in force	0.00%	0.00%	0.00%
Percentage of amounts assumed to net	2.70%	1.60%	0.70%
Commercial Insurance
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Gross amounts	$ 3,258	$ 3,180	$ 3,088
Ceded amounts to other companies	99	98	102
Assumed amounts from other companies	6	7	10
Premiums Earned, Net	$ 3,165	$ 3,089	$ 2,996
Percentage of amounts assumed to net	0.20%	0.20%	0.30%
Personal Insurance
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Gross amounts	$ 1,275	$ 1,195	$ 1,131
Ceded amounts to other companies	35	35	35
Assumed amounts from other companies	1	1	1
Premiums Earned, Net	$ 1,241	$ 1,161	$ 1,097
Percentage of amounts assumed to net	0.10%	0.10%	0.10%
Excess and Surplus Lines Insurance
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Gross amounts	$ 219	$ 192	$ 177
Ceded amounts to other companies	10	9	9
Assumed amounts from other companies	0	0	0
Premiums Earned, Net	$ 209	$ 183	$ 168
Percentage of amounts assumed to net	0.00%	0.00%	0.00%
Reinsurance assumed and other non segment [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Gross amounts	$ 0	$ 0	$ 0
Ceded amounts to other companies	18	20	8
Assumed amounts from other companies	125	69	18
Premiums Earned, Net	$ 107	$ 49	$ 10
Percentage of amounts assumed to net	116.10%	140.80%	188.00%
Property, Liability And Casualty Insurance Segment [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Gross amounts	$ 4,752	$ 4,567	$ 4,396
Ceded amounts to other companies	162	162	154
Assumed amounts from other companies	132	77	29
Premiums Earned, Net	$ 4,722	$ 4,482	$ 4,271
Percentage of amounts assumed to net	2.80%	1.70%	0.70%
Life Insurance Segment
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Gross amounts	$ 300	$ 290	$ 271
Ceded amounts to other companies	68	62	62
Assumed amounts from other companies	0	0	0
Premiums Earned, Net	$ 232	$ 228	$ 209
Percentage of amounts assumed to net	0.00%	0.00%	0.00%

Valuation And Qualifying Acc112

Valuation And Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Valuation and Qualifying Accounts [Abstract]
Beginning balance, January 1	$ 5	$ 4	$ 3
Additions charged to costs and expenses	6	5	3
Deductions	(5)	(4)	(2)
Ending balance, December 31	$ 6	$ 5	$ 4

Supplementary Information Co113

Supplementary Information Concerning Property Casualty Insurance Operations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Supplemental Information for Property, Casualty Insurance Underwriters [Line Items]
Deferred policy acquisition costs	$ 438	$ 408	$ 388
Reserves for unpaid claims and claim adjustment expenses	5,219	5,035	4,660
Unearned premiums	2,403	2,306	2,200
Earned premiums	4,722	4,482	4,271
Investment income	392	384	368
Loss and loss expenses incurred related to current accident year	3,257	3,029	2,756
Prior year claims and claims adjustment expense, (favorable) and unfavorable	(119)	(168)	(184)
Amortization of deferred policy acquisition cost	867	820	792
Paid loss and loss expenses	2,843	2,503	2,349
Net written premiums	4,840	4,580	4,361
Commercial Insurance
Supplemental Information for Property, Casualty Insurance Underwriters [Line Items]
Deferred policy acquisition costs	284	271	264
Reserves for unpaid claims and claim adjustment expenses	4,236	4,179	3,925
Unearned premiums	1,548	1,510	1,472
Earned premiums	3,165	3,089	2,996
Investment income	0	0	0
Loss and loss expenses incurred related to current accident year	2,115	2,057	1,862
Prior year claims and claims adjustment expense, (favorable) and unfavorable	(73)	(129)	(154)
Amortization of deferred policy acquisition cost	590	570	552
Paid loss and loss expenses	1,866	1,675	1,575
Net written premiums	3,202	3,122	3,025
Personal Insurance
Supplemental Information for Property, Casualty Insurance Underwriters [Line Items]
Deferred policy acquisition costs	121	110	103
Reserves for unpaid claims and claim adjustment expenses	587	569	498
Unearned premiums	683	629	593
Earned premiums	1,241	1,161	1,097
Investment income	0	0	0
Loss and loss expenses incurred related to current accident year	932	844	784
Prior year claims and claims adjustment expense, (favorable) and unfavorable	(14)	(4)	5
Amortization of deferred policy acquisition cost	225	209	210
Paid loss and loss expenses	898	771	731
Net written premiums	1,294	1,198	1,128
Excess and Surplus Lines Insurance
Supplemental Information for Property, Casualty Insurance Underwriters [Line Items]
Deferred policy acquisition costs	17	16	15
Reserves for unpaid claims and claim adjustment expenses	264	241	227
Unearned premiums	105	93	87
Earned premiums	209	183	168
Investment income	0	0	0
Loss and loss expenses incurred related to current accident year	115	102	105
Prior year claims and claims adjustment expense, (favorable) and unfavorable	(29)	(34)	(35)
Amortization of deferred policy acquisition cost	35	31	28
Paid loss and loss expenses	61	55	43
Net written premiums	219	189	175
Reinsurance assumed and other non segment [Member]
Supplemental Information for Property, Casualty Insurance Underwriters [Line Items]
Deferred policy acquisition costs	16	11	6
Reserves for unpaid claims and claim adjustment expenses	132	46	10
Unearned premiums	67	74	48
Earned premiums	107	49	10
Investment income	0	0	0
Loss and loss expenses incurred related to current accident year	95	26	5
Prior year claims and claims adjustment expense, (favorable) and unfavorable	(3)	(1)	0
Amortization of deferred policy acquisition cost	17	10	2
Paid loss and loss expenses	18	2	0
Net written premiums	$ 125	$ 71	$ 33