CNA Financial (CNA) 10-K 15 Feb 17 2016 FY Annual report Financial data

Document and Entity Information

Document and Entity Information Document $ in Millions	12 Months Ended
	Dec. 31, 2016USD ($)shares
Document and Entity Information [Abstract]
Entity Registrant Name	CNA FINANCIAL CORP
Entity Central Index Key	21,175
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-K
Document Period End Date	Dec. 31, 2016
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Common Stock, Shares Outstanding | shares	270,495,998
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float | $	$ 844

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Revenues
Net earned premiums	$ 6,924		$ 6,921		$ 7,212
Net Investment Income	1,988		1,840		2,067
Net realized investment gains (losses):
Other-than-temporary impairment losses	(81)		(156)		(77)
Other net realized investment gains (loss)	131		89		134
Net realized investment gains (losses)	50		(67)		57
Other revenues	404		407		356
Total revenues	9,366		9,101		9,692
Claims, Benefits and Expenses
Insurance claims and policyholders' benefits	5,283		5,384		5,591
Amortization of deferred acquisition costs	1,235		1,540		1,317
Other operating expenses	1,552		1,473		1,394
Interest	159		155		183
Total claims, benefits and expenses	8,229		8,552		8,485
Income (loss) from continuing operations before income tax	1,137		549		1,207
Income tax expense (benefit)	(278)		(70)		(319)
Net income (loss) from continuing operations	859		479		888
(Loss) income from discontinued operations, net of income tax benefit (expense)	0		0		(197)
Net income (loss)	$ 859	[1]	$ 479	[1],[2]	$ 691
Basic Earnings (Loss) Per Share Attributable to CNA
Income (loss) from continuing operations	$ 3.18		$ 1.77		$ 3.29
(Loss) income from discontinued operations	0		0		(0.73)
Basic earnings (loss) per share	3.18		1.77		2.56
Diluted Earnings (Loss) Per Share Attributable to CNA
Income (loss) from continuing operations	3.17		1.77		3.28
(Loss) income from discontinued operations	0		0		(0.73)
Diluted earnings (loss) per share	3.17		1.77		2.55
Dividends per share	$ 3		$ 3		$ 2
Weighted Average Outstanding Common Stock and Common Stock Equivalents
Basic	270.4		270.2		269.9
Diluted	271.1		270.7		270.6
[1]	Net income (loss) in the first quarter of 2016 and the second quarter of 2015 included a charge related to the application of retroactive reinsurance accounting to adverse reserve development ceded under the 2010 A&EP Loss Portfolio Transfer in our Corporate & Other Non-Core segment.
[2]	Net income (loss) in the fourth quarter of 2015 included a charge related to recognition of a premium deficiency in our long term care business.

Consolidated Statements of Ope3

Consolidated Statements of Operations Parenthetical (Parentheticals) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Statement [Abstract]
Income tax benefit (expense) on discontinued operations	$ 0	$ 0	$ 34

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 859	[1]	$ 479	[1],[2]	$ 691
Other Comprehensive Income (Loss), Net of Tax, Changes In:
Net unrealized gains (losses) on investments with other-than-temporary impairments	3		(9)		15
Net unrealized gains (losses) on other investments	252		(552)		267
Net unrealized gains (losses) on investments	255		(561)		282
Net unrealized losses on discontinued operations	0		0		(22)
Foreign currency translation adjustment	(114)		(139)		(95)
Pension and postretirement benefits	1		(15)		(207)
Other comprehensive income (loss), net of tax	142		(715)		(42)
Total comprehensive income (loss)	$ 1,001		$ (236)		$ 649
[1]	Net income (loss) in the first quarter of 2016 and the second quarter of 2015 included a charge related to the application of retroactive reinsurance accounting to adverse reserve development ceded under the 2010 A&EP Loss Portfolio Transfer in our Corporate & Other Non-Core segment.
[2]	Net income (loss) in the fourth quarter of 2015 included a charge related to recognition of a premium deficiency in our long term care business.

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Assets
Fixed maturity securities at fair value (amortized cost of $38,361 and $37,253)	$ 40,905	$ 39,572
Equity securities at fair value (cost of $106 and $191)	110	197
Limited partnership investments	2,371	2,548
Other invested assets	36	44
Mortgage loans	591	678
Short term investments	1,407	1,660
Total investments	45,420	44,699
Cash	271	387
Reinsurance receivables (less allowance for uncollectible receivables of $37 and $38)	4,416	4,453
Insurance receivables (less allowance for uncollectible receivables of $46 and $51)	2,209	2,078
Accrued investment income	405	404
Deferred acquisition costs	600	598
Deferred income taxes	379	638
Property and equipment at cost (less accumulated depreciation of $254 and $382)	310	343
Goodwill	145	150
Other assets	1,078	1,295
Total assets	55,233	55,045
Liabilities
Claim and claim adjustment expenses	22,343	22,663
Unearned premiums	3,762	3,671
Future policy benefits	10,326	10,152
Short term debt	0	350
Long term debt	2,710	2,210
Other liabilities (includes $50 and $82 due to Loews Corporation)	4,123	4,243
Total liabilities	43,264	43,289
Stockholders' Equity
Common stock ($2.50 par value; 500,000,000 shares authorized; 273,040,243 shares issued; 270,495,998 and 270,274,361 shares outstanding)	683	683
Additional paid-in capital	2,173	2,153
Retained earnings	9,359	9,313
Accumulated other comprehensive income (loss)	(173)	(315)
Treasury stock (2,544,245 and 2,765,882 shares), at cost	(73)	(78)
Total stockholders’ equity	11,969	11,756
Total liabilities and stockholders' equity	$ 55,233	$ 55,045

Consolidated Balance Sheet Pare

Consolidated Balance Sheet Parentheticals (Parentheticals) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Fixed maturities securities at amortized cost	$ 38,361	$ 37,253
Equity securities at cost	106	191
Allowance for uncollectible reinsurance receivables	37	38
Allowance for uncollectible insurance receivables	46	51
Accumulated depreciation on property and equipment	254	382
Due to Related Parties	$ 50	$ 82
Common stock, par value	$ 2.50	$ 2.50
Common stock, shares authorized	500,000,000	500,000,000
Common stock, shares issued	273,040,243	273,040,243
Common stock, shares outstanding	270,495,998	270,274,361
Treasury stock, shares	2,544,245	2,765,882

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Cash Flows from Operating Activities
Net income (loss)	$ 859	[1]	$ 479	[1],[2]	$ 691
Adjustments to reconcile net income (loss) to net cash flows provided (used) by operating activities:
Loss on sale of subsidiaries	0		0		251
Deferred income tax expense (benefit)	136		(150)		3
Trading portfolio activity	(9)		17		16
Net Realized Investment Gains Losses Continuing And Discontinuing Operations	50		(67)		60
Equity method investees	238		195		83
Amortization of investments	(27)		17		3
Depreciation and amortization	77		84		83
Changes in:
Receivables, net	(130)		82		731
Accrued investment income	(3)		(1)		0
Deferred acquisition costs	(8)		311		44
Insurance reserves	237		241		(363)
Other assets	(95)		(79)		(48)
Other liabilities	162		126		(48)
Other, net	29		(2)		54
Total adjustments	557		908		749
Net cash flows provided (used) by operating activities	1,416		1,387		1,440
Dispositions:
Fixed maturity securities - sales	5,328		4,390		4,914
Fixed maturity securities - maturities, calls and redemptions	3,219		4,095		3,983
Equity securities	81		57		31
Limited partnerships	290		174		167
Mortgage loans	207		26		57
Purchases:
Fixed maturity securities	(9,827)		(8,675)		(9,365)
Equity securities	0		(62)		(67)
Limited partnerships	(252)		(188)		(271)
Mortgage loans	(120)		(123)		(137)
Change in other investments	7		4		15
Change in short term investments	258		34		(388)
Purchases of property and equipment	(146)		(125)		(71)
Proceeds from Sale of Property, Plant, and Equipment	107		0		0
Proceeds from sale of subsidiaries	0		0		198
Other, net	2		21		16
Net cash flows provided (used) by investing activities	(846)		(372)		(918)
Cash Flows from Financing Activities
Dividends paid to common stockholders	(813)		(811)		(541)
Proceeds from the issuance of debt	498		0		546
Repayment of debt	(358)		0		(549)
Other, net	0		4		25
Net cash flows provided (used) by financing activities	(673)		(807)		(519)
Effect of foreign exchange rate changes on cash	(13)		(11)		(8)
Net change in cash	(116)		197		(5)
Cash, beginning of year	387		190		195
Cash, end of year	$ 271		$ 387		$ 190
[1]	Net income (loss) in the first quarter of 2016 and the second quarter of 2015 included a charge related to the application of retroactive reinsurance accounting to adverse reserve development ceded under the 2010 A&EP Loss Portfolio Transfer in our Corporate & Other Non-Core segment.
[2]	Net income (loss) in the fourth quarter of 2015 included a charge related to recognition of a premium deficiency in our long term care business.

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity $ in Millions	USD ($)
Balance, beginning of year at Dec. 31, 2013	$ 683
Balance, end of year at Dec. 31, 2014	683
Balance, beginning of year at Dec. 31, 2013	2,145
Additional Paid-In Capital
Stock-based compensation	6
Balance, end of year at Dec. 31, 2014	2,151
Balance, beginning of year at Dec. 31, 2013	9,495
Retained Earnings (Accumulated Deficit)
Dividends paid to common stockholders	(541)
Net income (loss)	691
Balance, end of year at Dec. 31, 2014	9,645
Accumulated other comprehensive income (loss), beginning balance at Dec. 31, 2013	442
Accumulated Other Comprehensive Income (Loss)
Other Comprehensive Income (Loss)	(42)
Accumulated other comprehensive income (loss), ending balance at Dec. 31, 2014	400
Balance, beginning of year at Dec. 31, 2013	(91)
Treasury Stock
Stock Based Compensation and Other	7
Balance, end of year at Dec. 31, 2014	(84)
Balance, beginning of year at Dec. 31, 2013	(23)
Notes Receivable for the Issuance of Common Stock
(Decrease) increase in notes receivable from the issuance of common stock	22
Balance, end of year at Dec. 31, 2014	(1)
Notes Receivable for the Issuance of Common Stock
Total stockholder's equty	12,794
Balance, end of year at Dec. 31, 2015	683
Additional Paid-In Capital
Stock-based compensation	2
Balance, end of year at Dec. 31, 2015	2,153
Retained Earnings (Accumulated Deficit)
Dividends paid to common stockholders	(811)
Net income (loss)	479	[1],[2]
Balance, end of year at Dec. 31, 2015	9,313
Accumulated Other Comprehensive Income (Loss)
Other Comprehensive Income (Loss)	(715)
Accumulated other comprehensive income (loss), ending balance at Dec. 31, 2015	(315)
Treasury Stock
Stock Based Compensation and Other	6
Balance, end of year at Dec. 31, 2015	(78)
Notes Receivable for the Issuance of Common Stock
(Decrease) increase in notes receivable from the issuance of common stock	1
Balance, end of year at Dec. 31, 2015	0
Notes Receivable for the Issuance of Common Stock
Total stockholder's equty	11,756
Balance, end of year at Dec. 31, 2016	683
Additional Paid-In Capital
Stock-based compensation	20
Balance, end of year at Dec. 31, 2016	2,173
Retained Earnings (Accumulated Deficit)
Dividends paid to common stockholders	(813)
Net income (loss)	859	[1]
Balance, end of year at Dec. 31, 2016	9,359
Accumulated Other Comprehensive Income (Loss)
Other Comprehensive Income (Loss)	142
Accumulated other comprehensive income (loss), ending balance at Dec. 31, 2016	(173)
Treasury Stock
Stock Based Compensation and Other	5
Balance, end of year at Dec. 31, 2016	(73)
Notes Receivable for the Issuance of Common Stock
(Decrease) increase in notes receivable from the issuance of common stock	0
Total stockholder's equty	$ 11,969
[1]	Net income (loss) in the first quarter of 2016 and the second quarter of 2015 included a charge related to the application of retroactive reinsurance accounting to adverse reserve development ceded under the 2010 A&EP Loss Portfolio Transfer in our Corporate & Other Non-Core segment.
[2]	Net income (loss) in the fourth quarter of 2015 included a charge related to recognition of a premium deficiency in our long term care business.

Summary of Significant Accounti

Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Notes)	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
Significant Accounting Policies [Text Block]	Note A . Summary of Significant Accounting Policies Basis of Presentation The Consolidated Financial Statements include the accounts of CNA Financial Corporation (CNAF) and its subsidiaries. Collectively, CNAF and its subsidiaries are referred to as CNA or the Company. Loews Corporation (Loews) owned approximately 90% of the outstanding common stock of CNAF as of December 31, 2016 . The accompanying Consolidated Financial Statements have been prepared in conformity with accounting principles generally accepted in the United States of America (GAAP). Intercompany amounts have been eliminated. The preparation of Consolidated Financial Statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the Consolidated Financial Statements and the reported amounts of revenues and expenses during the reporting period. Actual results may differ from those estimates. Sale of Continental Assurance Company (CAC) On August 1, 2014, the Company completed the sale of CAC. The business sold, which was previously reported within the Life & Group Non-Core segment, is reported as discontinued operations. The Company elected to include CAC cash flow activity in the comparative Consolidated Statements of Cash Flow. Further information related to the sale of CAC is provided in Note P to the Consolidated Financial Statements. In connection with the sale of CAC, the Company entered into a 100% coinsurance agreement on a separate small block of annuity business outside of CAC. The coinsurance agreement required the transfer of assets with a book value equal to the ceded reserves on the inception date of the contract. Because a substantial portion of the assets supporting these liabilities are held in trust for the benefit of the original cedant, those assets were transferred on a funds withheld basis. Under this approach the Company maintains legal ownership of the assets, but the investment income and realized gains and losses on those assets inure to the reinsurer. As a result, the $34 million difference between market value and book value of the funds withheld assets at the coinsurance contract's inception was recognized as a loss in Other operating expenses in 2014. The funds withheld aspect of the agreement is considered an embedded derivative. The embedded derivative is separately accounted for at fair value and reported with the host contract in Other liabilities on the Company's Consolidated Balance Sheet. The Company recognizes Other operating expense equal to the Net investment income generated by these trust assets. Insurance Operations Premiums: Insurance premiums on property and casualty insurance contracts are recognized in proportion to the underlying risk insured and are principally earned ratably over the duration of the policies. Premiums on long term care contracts are earned ratably over the policy year in which they are due. The reserve for unearned premiums represents the portion of premiums written relating to the unexpired terms of coverage. Insurance receivables include balances due currently or in the future, including amounts due from insureds related to losses under high deductible policies, and are presented at unpaid balances, net of an allowance for uncollectible receivables. Amounts are considered past due based on policy payment terms. The allowance is determined based on periodic evaluations of aged receivables, management's experience and current economic conditions. Insurance receivables and any related allowance are written off after collection efforts are exhausted or a negotiated settlement is reached. Property and casualty contracts that are retrospectively rated contain provisions that result in an adjustment to the initial policy premium depending on the contract provisions and loss experience of the insured during the experience period. For such contracts, the Company estimates the amount of ultimate premiums that the Company may earn upon completion of the experience period and recognizes either an asset or a liability for the difference between the initial policy premium and the estimated ultimate premium. The Company adjusts such estimated ultimate premium amounts during the course of the experience period based on actual results to date. The resulting adjustment is recorded as either a reduction of or an increase to the earned premiums for the period. Claim and claim adjustment expense reserves: Claim and claim adjustment expense reserves, except reserves for structured settlements not associated with asbestos and environmental pollution (A&EP), workers' compensation lifetime claims and long term care claims, are not discounted and are based on 1) case basis estimates for losses reported on direct business, adjusted in the aggregate for ultimate loss expectations; 2) estimates of incurred but not reported (IBNR) losses; 3) estimates of losses on assumed reinsurance; 4) estimates of future expenses to be incurred in the settlement of claims; 5) estimates of salvage and subrogation recoveries and 6) estimates of amounts due from insureds related to losses under high deductible policies. Management considers current conditions and trends as well as past Company and industry experience in establishing these estimates. The effects of inflation, which can be significant, are implicitly considered in the reserving process and are part of the recorded reserve balance. Ceded claim and claim adjustment expense reserves are reported as a component of Reinsurance receivables on the Consolidated Balance Sheets. Claim and claim adjustment expense reserves are presented net of anticipated amounts due from insureds related to losses under deductible policies of $1.2 billion and $1.2 billion as of December 31, 2016 and 2015 . A significant portion of these amounts are supported by collateral. The Company has an allowance for uncollectible deductible amounts, which is presented as a component of the allowance for doubtful accounts included in Insurance receivables on the Consolidated Balance Sheets. Structured settlements have been negotiated for certain property and casualty insurance claims. Structured settlements are agreements to provide fixed periodic payments to claimants. The Company's obligations for structured settlements not funded by annuities are included in claim and claim adjustment expense reserves and carried at present values determined using interest rates ranging from to 5.5% to 8.0% as of December 31, 2016 and 2015 . As of December 31, 2016 and 2015 , the discounted reserves for unfunded structured settlements were $544 million and $560 million , net of discount of $841 million and $880 million . For the years ended December 31, 2016 , 2015 and 2014 , the amount of interest recognized on the discounted reserves of unfunded structured settlements was $42 million , $42 million and $43 million , respectively. This interest accretion is presented as a component of Insurance claims and policyholders’ benefits on the Consolidated Statements of Operations, but is excluded from the Company’s disclosure of prior year development. Workers' compensation lifetime claim reserves are calculated using mortality assumptions determined through statutory regulation and economic factors. At December 31, 2016 and 2015 , workers' compensation lifetime claim reserves are discounted at a 3.5% interest rate. As of December 31, 2016 and 2015 , the discounted reserves for workers’ compensation lifetime claim reserves were $371 million and $396 million , net of discount of $202 million and $218 million . For the years ended December 31, 2016 , 2015 and 2014 the amount of interest accretion recognized on the discounted reserves of workers’ compensation lifetime claim reserves was $17 million , $20 million and $22 million , respectively. Long term care claim reserves are calculated using mortality and morbidity assumptions based on Company and industry experience. Long term care claim reserves are discounted at interest rates ranging from 4.5% to 6.8% as of December 31, 2016 and 2015 . As of December 31, 2016 and 2015 , such discounted reserves totaled $2.2 billion and $2.2 billion , net of discount of $529 million and $435 million . Future policy benefits reserves: Future policy benefits reserves represent the active life reserves related to the Company's long term care policies and are computed using the net level premium method, which incorporates actuarial assumptions as to morbidity, persistency, discount rate and expenses. Expense assumptions primarily relate to claim adjudication. Actuarial assumptions generally vary by plan, age at issue, policy duration and gender. The initial assumptions are determined at issuance, include a margin for adverse deviation and are locked in throughout the life of the contract unless a premium deficiency develops. If a premium deficiency emerges, the assumptions are unlocked and deferred acquisition costs, if any, and the future policy benefits reserves are adjusted. The December 31, 2015 gross premium valuation (GPV) indicated a premium deficiency of $296 million . The indicated premium deficiency necessitated a charge to income that was affected by the write off of the entire long term care deferred acquisition cost asset of $289 million and an increase to active life reserves of $7 million . As a result, the long term care active life reserves carried as of December 31, 2015 represent management’s best estimate assumptions at that date with no margin for adverse deviation. The December 31, 2016 GPV indicated the carried reserves were sufficient, therefore there was no unlocking of assumptions. Interest rates for long term care active life reserves range from 6.6% to 7.0% as of December 31, 2016 and 2015 . Guaranty fund and other insurance-related assessments: Liabilities for guaranty fund and other insurance-related assessments are accrued when an assessment is probable, when it can be reasonably estimated and when the event obligating the entity to pay an imposed or probable assessment has occurred. Liabilities for guaranty funds and other insurance-related assessments are not discounted and are included as part of Other liabilities on the Consolidated Balance Sheets. As of December 31, 2016 and 2015 , the liability balances were $125 million and $129 million . Reinsurance: Reinsurance accounting allows for contractual cash flows to be reflected as premiums and losses. To qualify for reinsurance accounting, reinsurance agreements must include risk transfer. To meet risk transfer requirements, a reinsurance contract must include both insurance risk, consisting of underwriting and timing risk, and a reasonable possibility of a significant loss for the assuming entity. Reinsurance receivables related to paid losses are presented at unpaid balances. Reinsurance receivables related to unpaid losses are estimated in a manner consistent with claim and claim adjustment expense reserves or future policy benefits reserves. Reinsurance receivables are reported net of an allowance for uncollectible amounts on the Consolidated Balance Sheets. The cost of reinsurance is primarily accounted for over the life of the underlying reinsured policies using assumptions consistent with those used to account for the underlying policies or over the reinsurance contract period. The ceding of insurance does not discharge the primary liability of the Company. The Company has established an allowance for uncollectible reinsurance receivables which relates to both amounts already billed on ceded paid losses as well as ceded reserves that will be billed when losses are paid in the future. The allowance for uncollectible reinsurance receivables is estimated on the basis of periodic evaluations of balances due from reinsurers, reinsurer solvency, management's experience and current economic conditions. Reinsurer financial strength ratings are updated and reviewed on an annual basis or sooner if the Company becomes aware of significant changes related to a reinsurer. Because billed receivables generally approximate 3% or less of total reinsurance receivables, the age of the reinsurance receivables related to paid losses is not a significant input into the allowance analysis. Changes in the allowance for uncollectible reinsurance receivables are presented as a component of Insurance claims and policyholders' benefits on the Consolidated Statements of Operations. Amounts are considered past due based on the reinsurance contract terms. Reinsurance receivables related to paid losses and any related allowance are written off after collection efforts have been exhausted or a negotiated settlement is reached with the reinsurer. Reinsurance receivables related to paid losses from insolvent insurers are written off when the settlement due from the estate can be reasonably estimated. At the time reinsurance receivables related to paid losses are written off, any required adjustment to reinsurance receivables related to unpaid losses is recorded as a component of Insurance claims and policyholders' benefits on the Consolidated Statements of Operations. Reinsurance contracts that do not effectively transfer the economic risk of loss on the underlying policies are recorded using the deposit method of accounting, which requires that premium paid or received by the ceding company or assuming company be accounted for as a deposit asset or liability. The Company had $3 million recorded as deposit assets as of December 31, 2016 and 2015 , and $6 million and $8 million recorded as deposit liabilities as of December 31, 2016 and 2015 . Income on reinsurance contracts accounted for under the deposit method is recognized using an effective yield based on the anticipated timing of payments and the remaining life of the contract. When the anticipated timing of payments changes, the effective yield is recalculated to reflect actual payments to date and the estimated timing of future payments. The deposit asset or liability is adjusted to the amount that would have existed had the new effective yield been applied since the inception of the contract. A loss portfolio transfer is a retroactive reinsurance contract. If the cumulative claim and allocated claim adjustment expenses ceded under a loss portfolio transfer exceed the consideration paid, the resulting gain from such excess is deferred and amortized into earnings in future periods in proportion to actual recoveries under the loss portfolio transfer. In any period in which there is a gain position and a revised estimate of claim and allocated claim adjustment expenses, a portion of the deferred gain is cumulatively recognized in earnings as if the revised estimate was available at the inception date of the loss portfolio transfer. Deferred acquisition costs: Deferrable acquisition costs include commissions, premium taxes and certain underwriting and policy issuance costs which are incremental direct costs of successful contract acquisitions. Acquisition costs related to property and casualty business are deferred and amortized ratably over the period the related premiums are earned. Deferred acquisition costs are presented net of ceding commissions and other ceded acquisition costs. The Company evaluates deferred acquisition costs for recoverability. Anticipated investment income is considered in the determination of the recoverability of deferred acquisition costs. Adjustments, if necessary, are recorded in current period results of operations. Deferred acquisition costs related to long term care contracts issued prior to January 1, 2004 include costs which vary with and are primarily related to the acquisition of business. As noted under Future policy benefits reserves, all of the long term care deferred acquisition costs of $289 million were written off as of December 31, 2015 in recognition of a premium deficiency. Investments in life settlement contracts and related revenue recognition: Prior to 2002, the Company purchased investments in life settlement contracts. The Company obtained the ownership and beneficiary rights of an underlying life insurance policy through a life settlement contract with the owner of the life insurance contract. The Company accounts for its investments in life settlement contracts using the fair value method. Under the fair value method, each life settlement contract is carried at its fair value at the end of each reporting period. The change in fair value estimated through the Company's internal valuation process, life insurance proceeds received and periodic maintenance costs, such as premiums, necessary to keep the underlying policy in force, are recorded in Other revenues on the Consolidated Statements of Operations. In December 2016, the Company reached agreement on terms to sell the entire portfolio of life settlement contracts to a third party. The Company expects to consummate this transaction in 2017. As a result, the portfolio, which is included within Life & Group Non-Core segment, was determined to be held for sale as of December 31, 2016 . Therefore, the contracts were measured at the lower of the carrying amount or the fair value per the agreed terms. This resulted in a $10 million loss recognized within Net realized investment gains. The fair value of the Company's investments in life settlement contracts were $58 million and $74 million as of December 31, 2016 and 2015 , and are included in Other assets on the Consolidated Balance Sheets. The cash receipts and payments related to life settlement contracts are included in Cash flows from operating activities on the Consolidated Statements of Cash Flows. The following table details the values for life settlement contracts. The determination of fair value is discussed in Note C to the Consolidated Financial Statements. December 31, 2016 Number of Life Settlement Contracts Fair Value of Life Settlement Contracts (In millions) Face Amount of Life Insurance Policies (In millions) Estimated settlements during: 2017 63 $ 10 $ 34 2018 55 8 30 2019 49 7 26 2020 43 6 23 2021 36 4 19 Thereafter 280 23 153 Total 526 $ 58 $ 285 The Company uses an actuarial model to estimate the aggregate face amount of life insurance that are expected to settle in each future year and the corresponding fair value. This model projects the likelihood of the insured's death for each inforce policy based upon the Company's estimated mortality rates, which may vary due to the relatively small size of the portfolio of life settlement contracts. The number of life settlement contracts presented in the table above is based upon the average face amount of inforce policies estimated to settle in each future year. The increase in fair value recognized in Other revenues for the years ended December 31, 2016 , 2015 and 2014 on contracts still held at each respective period-end was $7 million , $1 million and $8 million . The gains recognized during the years ended December 31, 2016 , 2015 and 2014 on contracts that settled were $8 million , $24 million and $25 million . Investments The Company classifies its fixed maturity securities and its equity securities as either available-for-sale or trading, and as such, they are carried at fair value. Changes in fair value of trading securities are reported within Net investment income on the Consolidated Statements of Operations. Changes in fair value related to available-for-sale securities are reported as a component of Other comprehensive income. Losses may be recognized within Net realized investment gains (losses) on the Consolidated Statements of Operations when a decline in value is determined by the Company to be other-than-temporary. The cost of fixed maturity securities classified as available-for-sale is adjusted for amortization of premiums and accretion of discounts, which are included in Net investment income on the Consolidated Statements of Operations. The amortization of premium and accretion of discount for fixed maturity securities takes into consideration call and maturity dates that produce the lowest yield. In 2015 the Company changed its accounting principle as previously the amortization of premiums was to maturity. This change in estimate effected by a change in accounting principle was adopted in the fourth quarter of 2015 and decreased Net investment income and the amortized cost of fixed maturity securities by $39 million in the Consolidated Statement of Operations for the year-ended December 31, 2015 and the Consolidated Balance Sheet as of December 31, 2015 . The $39 million decrease to Net investment income included a $22 million cumulative adjustment relating to prior periods. The total adjustment decreased Basic and Diluted earnings per share by $0.09 for the year ended December 31, 2015 . To the extent that unrealized gains on fixed income securities supporting long term care products and structured settlements not funded by annuities would result in a premium deficiency if those gains were realized, a related increase in Insurance reserves is recorded, net of tax, as a reduction of net unrealized gains through Other comprehensive income (Shadow Adjustments). Shadow Adjustments, net of tax, decreased $97 million and $177 million for the years ended December 31, 2016 and 2015 . As of December 31, 2016 and 2015 , net unrealized gains on investments included in Accumulated other comprehensive income (AOCI) were correspondingly reduced by Shadow Adjustments of $1,014 million and $1,111 million . For asset-backed securities included in fixed maturity securities, the Company recognizes income using an effective yield based on anticipated prepayments and the estimated economic life of the securities. When estimates of prepayments change, the effective yield is recalculated to reflect actual payments to date and anticipated future payments. The amortized cost of high credit quality fixed rate securities is adjusted to the amount that would have existed had the new effective yield been applied since the acquisition of the securities. Such adjustments are reflected in Net investment income on the Consolidated Statements of Operations. Interest income on lower rated and variable rate securities is determined using the prospective yield method. The Company's carrying value of investments in limited partnerships is its share of the net asset value of each partnership, as determined by the general partner. Certain partnerships for which results are not available on a timely basis are reported on a lag, primarily three months or less. Changes in net asset values are accounted for under the equity method and recorded within Net investment income on the Consolidated Statements of Operations. Mortgage loans are commercial in nature, are carried at unpaid principal balance, net of unamortized fees and any valuation allowance, and are recorded once funded. Mortgage loans are considered to be impaired loans when it is probable that contractual principal and interest payments will not be collected. A valuation allowance is established for impaired loans to the extent that the present value of expected future cash flows discounted at the loan's original effective interest rate is less than the carrying value of the loan. Interest income from mortgage loans is recognized on an accrual basis using the effective yield method. Accrual of income is generally suspended for mortgage loans that are impaired and collection of principal and interest payments is unlikely. Mortgage loans are considered past due when full principal or interest payments have not been received according to contractual terms. Other invested assets include overseas deposits and Federal Home Loan Bank of Chicago (FHLBC) stock. FHLBC stock is carried at fair value. Overseas deposits are valued using the net asset value per share (or equivalent) practical expedient. They are primarily short-term government securities, agency securities and corporate bonds held in trusts that are managed by Lloyd's of London. These funds are required of Lloyd's syndicates to protect policyholders in overseas markets and may be denominated in local currency. Short term investments are carried at fair value, with the exception of cash accounts earning interest, which are carried at cost and approximate fair value. Changes in fair value are reported as a component of Other comprehensive income. Purchases and sales of all securities are recorded on the trade date, except for private placement debt securities, including bank loan participations, which are recorded once funded. Realized investment gains and losses are determined on the basis of the cost or amortized cost of the specific securities sold. In the normal course of investing activities, the Company enters into relationships with variable interest entities (VIEs), as both an investor in limited partnerships and asset-backed securities issued by third-party VIEs. The Company is not the primary beneficiary of these VIEs, and therefore does not consolidate them. The Company determines whether it is the primary beneficiary of a VIE based on a qualitative assessment of the relative power and benefits of the Company and our venture partners. 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. A security is impaired if the fair value of the security is less than its cost adjusted for accretion, amortization and previously recorded other-than-temporary impairment (OTTI) losses, otherwise defined as an unrealized loss. When a security is impaired, the impairment is evaluated to determine whether it is temporary or other-than-temporary. Significant judgment is required in the determination of whether an OTTI loss has occurred for a security. The Company follows a consistent and systematic process for determining and recording an OTTI loss. The Company has established a committee responsible for the OTTI process referred to as the Impairment Committee. The Impairment Committee is responsible for evaluating all securities in an unrealized loss position on at least a quarterly basis. The Impairment Committee’s assessment of whether an OTTI loss has occurred incorporates both quantitative and qualitative information. Fixed maturity securities that the Company intends to sell, or it more likely than not will be required to sell before recovery of amortized cost, are considered to be other-than-temporarily impaired and the entire difference between the amortized cost basis and fair value of the security is recognized as an OTTI loss in earnings. The remaining fixed maturity securities in an unrealized loss position are evaluated to determine if a credit loss exists. The factors considered by the Impairment Committee include (a) the financial condition and near-term and long-term prospects of the issuer, (b) whether the debtor is current on interest and principal payments, (c) credit ratings of the securities and (d) general market conditions and industry or sector specific outlook. The Company also considers results and analysis of cash flow modeling for asset-backed securities, and when appropriate, other fixed maturity securities. The focus of the analysis for asset-backed securities is on assessing the sufficiency and quality of underlying collateral and timing of cash flows based on scenario tests. If the present value of the modeled expected cash flows equals or exceeds the amortized cost of a security, no credit loss is judged to exist and the asset-backed security is deemed to be temporarily impaired. If the present value of the expected cash flows is significantly less than amortized cost, the security is judged to be other-than-temporarily impaired for credit reasons and that shortfall, referred to as the credit component, is recognized as an OTTI loss in earnings. The difference between the adjusted amortized cost basis and fair value, referred to as the non-credit component, is recognized as OTTI in Other comprehensive income. In subsequent reporting periods, a change in intent to sell or further credit impairment on a security whose fair value has not deteriorated will cause the non-credit component originally recorded as OTTI in Other comprehensive income to be recognized as an OTTI loss in earnings. The Company performs the discounted cash flow analysis using stressed scenarios to determine future expectations regarding recoverability. Significant assumptions enter into these cash flow projections including delinquency rates, probable risk of default, loss severity upon a default, over collateralization and interest coverage triggers and credit support from lower level tranches. The Company applies the same impairment model as described above for the majority of its non-redeemable preferred stock securities on the basis that these securities possess characteristics similar to debt securities and that the issuers maintain their ability to pay dividends. For all other equity securities, in determining whether the security is other-than-temporarily impaired, the Impairment Committee considers a number of factors including, but not limited to: (a) the length of time and the extent to which the fair value has been less than amortized cost, (b) the financial condition and near term prospects of the issuer, (c) the intent and ability of the Company to retain its investment for a period of time sufficient to allow for an anticipated recovery in value and (d) general market conditions and industry or sector specific outlook. Income Taxes The Company and its eligible subsidiaries (CNA Tax Group) are included in the consolidated federal income tax return of Loews and its eligible subsidiaries. The Company accounts for income taxes under the asset and liability method. Under the asset and liability method, deferred income taxes are recognized for temporary differences between the financial statement and tax return bases of assets and liabilities, based on enacted tax rates and other provisions of the tax law. The effect of a change in tax laws or rates on deferred tax assets and liabilities is recognized in income in the period in which such change is enacted. Future tax benefits are recognized to the extent that realization of such benefits is more likely than not, and a valuation allowance is established for any portion of a deferred tax asset that management believes will not be realized. Pension and Postretirement Benefits The Company recognizes the overfunded or underfunded status of its defined benefit plans in Other assets or Other liabilities on the Consolidated Balance Sheets. Changes in funded status related to prior service costs and credits and actuarial gains and losses are recognized in the year in which the changes occur through Other comprehensive income. Annual service cost, interest cost, expected return on plan assets, amortization of prior service costs and credits and amortization of actuarial gains and losses are recognized in the Consolidated Statements of Operations. The vested benefit obligation for the CNA Retirement Plan is determined based on eligible compensation and accrued service for previously entitled employees. Effective June 30, 2015, future benefit accruals under the CNA Retirement Plan were eliminated and the benefit obligations were frozen. Stock-Based Compensation The Company records compensation expense using the fair value method for all awards it grants, modifies or cancels primarily on a straight-line basis over the requisite service period, generally three to four years. Foreign Currency Foreign currency translation gains and losses are reflected in Stockholders' equity as a component of AOCI. The Company's foreign subsidiaries' balance sheet accounts are translated at the exchange rates in effect at each reporting date and income statement accounts are either translated at the exchange rate on the date of the transaction or at the average exchange rates. Foreign currency transaction gains (losses) of $(9) million , $(11) million and $(25) million were included in determining Net income (loss) for the years ended December 31, 2016 , 2015 and 2014 . Property and Equipment Property and equipment are carried at cost less accumulated depreciation. Depreciation is based on the estimated useful lives of the various classes of property and equipment and is determined principally on the straight-line method. Furniture and fixtures are depreciated over seven years. Office equipment is depreciated over five years. The estimated lives for data processing equipment an

Investments

Investments	12 Months Ended
	Dec. 31, 2016
Investments [Abstract]
Investments	Note B . Investments The significant components of Net investment income are presented in the following table. Years ended December 31 (In millions) 2016 2015 2014 Fixed maturity securities $ 1,819 $ 1,751 $ 1,803 Equity securities 10 12 12 Limited partnership investments 155 92 263 Mortgage loans 41 33 31 Short term investments 8 6 3 Trading portfolio 10 8 10 Other 4 1 3 Gross investment income 2,047 1,903 2,125 Investment expense (59 ) (63 ) (58 ) Net investment income $ 1,988 $ 1,840 $ 2,067 As of December 31, 2016 , the Company held no non-income producing fixed maturity securities. As of December 31, 2015 , the Company held $54 million of non-income producing fixed maturity securities. As of December 31, 2016 and 2015 , no investments in a single issuer exceeded 10% of stockholders' equity, other than investments in securities issued by the U.S. Treasury and obligations of government-sponsored enterprises. Net realized investment gains (losses) are presented in the following table. Years ended December 31 (In millions) 2016 2015 2014 Net realized investment gains (losses): Fixed maturity securities: Gross realized gains $ 204 $ 131 $ 170 Gross realized losses (138 ) (197 ) (129 ) Net realized investment gains (losses) on fixed maturity securities 66 (66 ) 41 Equity securities: Gross realized gains 5 2 8 Gross realized losses (10 ) (25 ) (7 ) Net realized investment gains (losses) on equity securities (5 ) (23 ) 1 Derivatives (2 ) 10 (1 ) Short term investments and other (9 ) 12 16 Net realized investment gains (losses) $ 50 $ (67 ) $ 57 Net change in unrealized gains on investments is presented in the following table. Years ended December 31 (In millions) 2016 2015 2014 Net change in unrealized gains on investments: Fixed maturity securities $ 225 $ (1,114 ) $ 1,511 Equity securities (2 ) (6 ) 6 Other 1 1 — Total net change in unrealized gains on investments $ 224 $ (1,119 ) $ 1,517 The components of OTTI losses recognized in earnings by asset type are presented in the following table. Years ended December 31 (In millions) 2016 2015 2014 Fixed maturity securities available-for-sale: Corporate and other bonds $ 59 $ 104 $ 18 States, municipalities and political subdivisions — 18 46 Asset-backed: Residential mortgage-backed 10 8 5 Other asset-backed 3 1 1 Total asset-backed 13 9 6 Total fixed maturity securities available-for-sale 72 131 70 Equity securities available-for-sale -- Common stock 9 25 7 OTTI losses recognized in earnings $ 81 $ 156 $ 77 The following tables present a summary of fixed maturity and equity securities. December 31, 2016 Cost or Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Unrealized OTTI Losses (Gains) (In millions) Fixed maturity securities available-for-sale: Corporate and other bonds $ 17,711 $ 1,323 $ 76 $ 18,958 $ (1 ) States, municipalities and political subdivisions 12,060 1,213 33 13,240 (16 ) Asset-backed: Residential mortgage-backed 5,004 120 51 5,073 (28 ) Commercial mortgage-backed 2,016 48 24 2,040 — Other asset-backed 1,022 8 5 1,025 — Total asset-backed 8,042 176 80 8,138 (28 ) U.S. Treasury and obligations of government-sponsored enterprises 83 10 — 93 — Foreign government 435 13 3 445 — Redeemable preferred stock 18 1 — 19 — Total fixed maturity securities available-for-sale 38,349 2,736 192 40,893 $ (45 ) Total fixed maturity securities trading 12 12 Equity securities available-for-sale: Common stock 13 6 — 19 Preferred stock 93 2 4 91 Total equity securities available-for-sale 106 8 4 110 Total $ 38,467 $ 2,744 $ 196 $ 41,015 December 31, 2015 Cost or Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Unrealized OTTI Losses (Gains) (In millions) Fixed maturity securities available-for-sale: Corporate and other bonds $ 17,080 $ 1,019 $ 342 $ 17,757 $ — States, municipalities and political subdivisions 11,729 1,453 8 13,174 (4 ) Asset-backed: Residential mortgage-backed 4,935 154 17 5,072 (37 ) Commercial mortgage-backed 2,154 55 12 2,197 — Other asset-backed 923 6 8 921 — Total asset-backed 8,012 215 37 8,190 (37 ) U.S. Treasury and obligations of government-sponsored enterprises 62 5 — 67 — Foreign government 334 13 1 346 — Redeemable preferred stock 33 2 — 35 — Total fixed maturity securities available-for-sale 37,250 2,707 388 39,569 $ (41 ) Total fixed maturity securities trading 3 3 Equity securities available-for-sale: Common stock 46 3 1 48 Preferred stock 145 7 3 149 Total equity securities available-for-sale 191 10 4 197 Total $ 37,444 $ 2,717 $ 392 $ 39,769 The following tables present the estimated fair value and gross unrealized losses of fixed maturity and equity securities in a gross unrealized loss position by the length of time in which the securities have continuously been in that position. Less than 12 Months 12 Months or Longer Total December 31, 2016 Estimated Fair Value Gross Unrealized Losses Estimated Fair Value Gross Unrealized Losses Estimated Fair Value Gross Unrealized Losses (In millions) Fixed maturity securities available-for-sale: Corporate and other bonds $ 2,615 $ 61 $ 254 $ 15 $ 2,869 $ 76 States, municipalities and political subdivisions 959 32 23 1 982 33 Asset-backed: Residential mortgage-backed 2,136 44 201 7 2,337 51 Commercial mortgage-backed 756 22 69 2 825 24 Other asset-backed 398 5 24 — 422 5 Total asset-backed 3,290 71 294 9 3,584 80 U.S. Treasury and obligations of government-sponsored enterprises 5 — — — 5 — Foreign government 108 3 — — 108 3 Redeemable preferred stock — — — — — — Total fixed maturity securities available-for-sale 6,977 167 571 25 7,548 192 Equity securities available-for-sale -- Preferred stock 12 — 13 4 25 4 Total $ 6,989 $ 167 $ 584 $ 29 $ 7,573 $ 196 Less than 12 Months 12 Months or Longer Total December 31, 2015 Estimated Fair Value Gross Unrealized Losses Estimated Fair Value Gross Unrealized Losses Estimated Fair Value Gross Unrealized Losses (In millions) Fixed maturity securities available-for-sale: Corporate and other bonds $ 4,882 $ 302 $ 162 $ 40 $ 5,044 $ 342 States, municipalities and political subdivisions 338 8 75 — 413 8 Asset-backed: Residential mortgage-backed 963 9 164 8 1,127 17 Commercial mortgage-backed 652 10 96 2 748 12 Other asset-backed 552 8 5 — 557 8 Total asset-backed 2,167 27 265 10 2,432 37 U.S. Treasury and obligations of government-sponsored enterprises 4 — — — 4 — Foreign government 54 1 — — 54 1 Redeemable preferred stock 3 — — — 3 — Total fixed maturity securities available-for-sale 7,448 338 502 50 7,950 388 Equity securities available-for-sale: Common Stock 3 1 — — 3 1 Preferred stock 13 3 — — 13 3 Total equity securities available-for-sale 16 4 — — 16 4 Total $ 7,464 $ 342 $ 502 $ 50 $ 7,966 $ 392 Based on current facts and circumstances, the Company believes the unrealized losses presented in the December 31, 2016 securities in a gross unrealized loss position table above are not indicative of the ultimate collectibility of the current amortized cost of the securities, but rather are attributable to changes in interest rates, credit spreads and other factors. The Company has no current intent to sell securities with unrealized losses, nor is it more likely than not that it will be required to sell prior to recovery of amortized cost; accordingly, the Company has determined that there are no additional OTTI losses to be recorded as of December 31, 2016 . The following table presents the activity related to the pretax credit loss component reflected in Retained earnings on fixed maturity securities still held as of December 31, 2016 , 2015 and 2014 for which a portion of an OTTI loss was recognized in Other comprehensive income (loss). Years ended December 31 (In millions) 2016 2015 2014 Beginning balance of credit losses on fixed maturity securities $ 53 $ 62 $ 74 Reductions for securities sold during the period (16 ) (9 ) (9 ) Reductions for securities the Company intends to sell or more likely than not will be required to sell (1 ) — (3 ) Ending balance of credit losses on fixed maturity securities $ 36 $ 53 $ 62 Contractual Maturity The following table presents available-for-sale fixed maturity securities by contractual maturity. December 31 2016 2015 (In millions) Cost or Amortized Cost Estimated Fair Value Cost or Amortized Cost Estimated Fair Value Due in one year or less $ 1,779 $ 1,828 $ 1,574 $ 1,595 Due after one year through five years 7,566 7,955 7,721 8,070 Due after five years through ten years 15,892 16,332 14,652 14,915 Due after ten years 13,112 14,778 13,303 14,989 Total $ 38,349 $ 40,893 $ 37,250 $ 39,569 Actual maturities may differ from contractual maturities because certain securities may be called or prepaid. Securities not due at a single date are allocated based on weighted average life. Limited Partnerships The carrying value of limited partnerships as of December 31, 2016 and 2015 was $2,371 million and $2,548 million , which includes undistributed earnings of $523 million and $687 million . Limited partnerships comprising 60% of the total carrying value are reported on a current basis through December 31, 2016 with no reporting lag, 18% are reported on a one month lag and the remainder are reported on more than a one month lag. The number of limited partnerships held and the strategies employed provide diversification to the limited partnership portfolio and the overall invested asset portfolio. Limited partnerships comprising 68% and 70% of the carrying value as of December 31, 2016 and 2015 employ hedge fund strategies. Limited partnerships comprising 27% and 26% of the carrying value as of December 31, 2016 and 2015 were invested in private debt and equity and the remainder were primarily invested in real estate strategies. Hedge fund strategies include both long and short positions in fixed income, equity and derivative instruments. These hedge fund strategies may seek to generate gains from mispriced or undervalued securities, price differentials between securities, distressed investments, sector rotation or various arbitrage disciplines. Within hedge fund strategies, approximately 55% were equity related, 26% pursued a multi-strategy approach, 17% were focused on distressed investments and 2% were fixed income related as of December 31, 2016 . The ten largest limited partnership positions held totaled $1,168 million and $1,221 million as of December 31, 2016 and 2015 . Based on the most recent information available regarding the Company’s percentage ownership of the individual limited partnerships, the carrying value reflected on the Consolidated Balance Sheets represents approximately 4% and 3% of the aggregate partnership equity as of December 31, 2016 and 2015 , and the related income reflected on the Consolidated Statements of Operations represents approximately 4% , 3% and 4% of the changes in aggregate partnership equity for the years ended December 31, 2016 , 2015 and 2014 . While the Company generally does not invest in highly leveraged partnerships, there are risks inherent in limited partnership investments which may result in losses due to short-selling, derivatives or other speculative investment practices. The use of leverage increases volatility generated by the underlying investment strategies. The Company’s limited partnership investments contain withdrawal provisions that generally limit liquidity for a period of thirty days up to one year and in some cases do not permit withdrawals until the termination of the partnership. Typically, withdrawals require advance written notice of up to 90 days. Derivative Financial Instruments The Company may use derivatives in the normal course of business, primarily in an attempt to reduce its exposure to market risk (principally interest rate risk, credit risk, equity price risk and foreign currency risk) stemming from various assets and liabilities. The Company's principal objective under such strategies is to achieve the desired reduction in economic risk, even if the position does not receive hedge accounting treatment. The Company may enter into interest rate swaps, futures and forward commitments to purchase securities to manage interest rate risk. The Company may use foreign currency forward contracts to manage foreign currency risk. Credit exposure associated with non-performance by the counterparties to derivative instruments is generally limited to the uncollateralized fair value of the asset related to the instruments recognized on the Consolidated Balance Sheets. The Company generally requires that all over-the-counter derivative contracts be governed by an International Swaps and Derivatives Association Master Agreement, and exchanges collateral under the terms of these agreements with its derivative investment counterparties depending on the amount of the exposure and the credit rating of the counterparty. Gross estimated fair values of derivative positions are presented in Other invested assets and Other liabilities on the Consolidated Balance Sheet. The Company does not offset derivative positions against the fair value of collateral provided or positions subject to netting arrangements. There would be no significant difference in the balance included in such accounts if the estimated fair values were presented net for the periods ended December 31, 2016 and 2015 . There was no cash collateral provided by the Company as of December 31, 2016 or 2015 . There was no cash collateral received from counterparties held as of December 31, 2016 or 2015 . The Company holds an embedded derivative on funds withheld liability with a notional value of $174 million and $179 million as of December 31, 2016 and 2015 and a fair value of $3 million and $5 million as of December 31, 2016 and 2015 . The embedded derivative on funds withheld liability is accounted for separately and reported with the funds withheld liability in Other liabilities on the Consolidated Balance Sheets. Commercial Mortgage Loans Risks related to the recoverability of loan balances include declines in the estimated cash flows from underlying property leases, fair value of collateral and creditworthiness of tenants of credit tenant loan properties, where lease payments directly service the loan. The Company evaluates loans for impairment on a specific loan basis and identifies loans for evaluation of impairment based on the collection experience of each loan and other credit quality indicators such as debt service coverage ratio and the creditworthiness of the borrower or tenants of credit tenant loan properties. As of December 31, 2016 and 2015 , there were no loans past due or in non-accrual status, and no valuation allowance was recorded. Investment Commitments As of December 31, 2016 , the Company had committed approximately $380 million to future capital calls from various third-party limited partnership investments in exchange for an ownership interest in the related partnerships. As of December 31, 2016 , the Company had mortgage loan commitments of $20 million representing signed loan applications received and accepted. The Company invests in various privately placed debt securities, including bank loans, as part of its overall investment strategy and has committed to additional future purchases, sales and funding. Purchases and sales of privately placed debt securities are recorded once funded. As of December 31, 2016 , the Company had commitments to purchase or fund additional amounts of $130 million and sell $121 million under the terms of such securities. Investments on Deposit Securities with carrying values of approximately $2.3 billion and $2.8 billion were deposited by the Company’s insurance subsidiaries under requirements of regulatory authorities and others as of December 31, 2016 and 2015 . Cash and securities with carrying values of approximately $514 million and $364 million were deposited with financial institutions as collateral for letters of credit as of December 31, 2016 and 2015 . In addition, cash and securities were deposited in trusts with financial institutions to secure reinsurance and other obligations with various third parties. The carrying values of these deposits were approximately $261 million and $263 million as of December 31, 2016 and 2015 .

Fair Value

Fair Value	12 Months Ended
	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Fair Value	Note C . Fair Value Fair value is the price that would be received upon sale of an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The following fair value hierarchy is used in selecting inputs, with the highest priority given to Level 1, as these are the most transparent or reliable. Level 1 - Quoted prices for identical instruments in active markets. Level 2 - Quoted prices for similar instruments in active markets; quoted prices for identical or similar instruments in markets that are not active; and model-derived valuations in which all significant inputs are observable in active markets. Level 3 - Valuations derived from valuation techniques in which one or more significant inputs are not observable. Prices may fall within Level 1, 2 or 3 depending upon the methodology and inputs used to estimate fair value for each specific security. In general the Company seeks to price securities using third-party pricing services. Securities not priced by pricing services are submitted to independent brokers for valuation and, if those are not available, internally developed pricing models are used to value assets using a methodology and inputs the Company believes market participants would use to value the assets. Prices obtained from third-party pricing services or brokers are not adjusted by the Company. The Company performs control procedures over information obtained from pricing services and brokers to ensure prices received represent a reasonable estimate of fair value and to confirm representations regarding whether inputs are observable or unobservable. Procedures may include i) the review of pricing service methodologies or broker pricing qualifications, ii) back-testing, where past fair value estimates are compared to actual transactions executed in the market on similar dates, iii) exception reporting, where period-over-period changes in price are reviewed and challenged with the pricing service or broker based on exception criteria, iv) deep dives, where the Company performs an independent analysis of the inputs and assumptions used to price individual securities and v) pricing validation, where prices received are compared to prices independently estimated by the Company. Assets and Liabilities Measured at Fair Value Assets and liabilities measured at fair value on a recurring basis are presented in the following tables. December 31, 2016 Total Assets/Liabilities at Fair Value (In millions) Level 1 Level 2 Level 3 Assets Fixed maturity securities: Corporate and other bonds $ — $ 18,840 $ 130 $ 18,970 States, municipalities and political subdivisions — 13,239 1 13,240 Asset-backed: Residential mortgage-backed — 4,944 129 5,073 Commercial mortgage-backed — 2,027 13 2,040 Other asset-backed — 968 57 1,025 Total asset-backed — 7,939 199 8,138 U.S. Treasury and obligations of government-sponsored enterprises 93 — — 93 Foreign government — 445 — 445 Redeemable preferred stock 19 — — 19 Total fixed maturity securities 112 40,463 330 40,905 Equity securities 91 — 19 110 Other invested assets — 5 — 5 Short term investments 475 853 — 1,328 Life settlement contracts, included in Other assets — — 58 58 Total assets $ 678 $ 41,321 $ 407 $ 42,406 Liabilities Other liabilities $ — $ (3 ) $ — $ (3 ) Total liabilities $ — $ (3 ) $ — $ (3 ) December 31, 2015 Total Assets/Liabilities at Fair Value (In millions) Level 1 Level 2 Level 3 Assets Fixed maturity securities: Corporate and other bonds $ — $ 17,592 $ 168 $ 17,760 States, municipalities and political subdivisions — 13,172 2 13,174 Asset-backed: Residential mortgage-backed — 4,938 134 5,072 Commercial mortgage-backed — 2,175 22 2,197 Other asset-backed — 868 53 921 Total asset-backed — 7,981 209 8,190 U.S. Treasury and obligations of government-sponsored enterprises 66 1 — 67 Foreign government — 346 — 346 Redeemable preferred stock 35 — — 35 Total fixed maturity securities 101 39,092 379 39,572 Equity securities 177 — 20 197 Other invested assets — 17 — 17 Short term investments 448 1,134 — 1,582 Life settlement contracts, included in Other assets — — 74 74 Total assets $ 726 $ 40,243 $ 473 $ 41,442 Liabilities Other liabilities $ — $ (5 ) $ — $ (5 ) Total liabilities $ — $ (5 ) $ — $ (5 ) The tables below present a reconciliation for all assets and liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3). Level 3 (In millions) Balance as of January 1, 2016 Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)* Net change in unrealized appreciation (depreciation) included in Other comprehensive income (loss) Purchases Sales Settlements Transfers into Level 3 Transfers out of Level 3 Balance as of December 31, 2016 Unrealized gains (losses) on Level 3 assets and liabilities held as of December 31, 2016 recognized in Net income (loss)* Fixed maturity securities: Corporate and other bonds $ 168 $ 1 $ 1 $ 163 $ (36 ) $ (103 ) $ — $ (64 ) $ 130 $ — States, municipalities and political subdivisions 2 — — — — (1 ) — — 1 — Asset-backed: Residential mortgage-backed 134 3 (5 ) 15 — (14 ) 56 (60 ) 129 — Commercial mortgage-backed 22 (1 ) (1 ) 32 — (17 ) 3 (25 ) 13 — Other asset-backed 53 (2 ) 1 86 (25 ) (1 ) 2 (57 ) 57 — Total asset-backed 209 — (5 ) 133 (25 ) (32 ) 61 (142 ) 199 — Total fixed maturity securities 379 1 (4 ) 296 (61 ) (136 ) 61 (206 ) 330 — Equity securities 20 (1 ) — — — — — — 19 (2 ) Life settlement contracts 74 5 — — — (21 ) — — 58 (3 ) Total $ 473 $ 5 $ (4 ) $ 296 $ (61 ) $ (157 ) $ 61 $ (206 ) $ 407 $ (5 ) Level 3 (In millions) Balance as of January 1, 2015 Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)* Net change in unrealized appreciation (depreciation) included in Other comprehensive income (loss) Purchases Sales Settlements Transfers into Level 3 Transfers out of Level 3 Balance as of December 31, 2015 Unrealized gains (losses) on Level 3 assets and liabilities held as of December 31, 2015 recognized in Net income (loss)* Fixed maturity securities: Corporate and other bonds $ 162 $ (2 ) $ (3 ) $ 65 $ (13 ) $ (35 ) $ 40 $ (46 ) $ 168 $ (2 ) States, municipalities and political subdivisions 94 1 — — — (10 ) — (83 ) 2 — Asset-backed: Residential mortgage-backed 189 5 (3 ) 81 — (35 ) 14 (117 ) 134 — Commercial mortgage-backed 83 7 (4 ) 23 — (17 ) 17 (87 ) 22 — Other asset-backed 655 3 3 130 (263 ) (52 ) 7 (430 ) 53 — Total asset-backed 927 15 (4 ) 234 (263 ) (104 ) 38 (634 ) 209 — Total fixed maturity securities 1,183 14 (7 ) 299 (276 ) (149 ) 78 (763 ) 379 (2 ) Equity securities 16 — (1 ) 4 — — 1 — 20 — Life settlement contracts 82 25 — — — (33 ) — — 74 1 Total $ 1,281 $ 39 $ (8 ) $ 303 $ (276 ) $ (182 ) $ 79 $ (763 ) $ 473 $ (1 ) Major Category of Assets and Liabilities Consolidated Statements of Operations Line Items Fixed maturity securities available-for-sale (1) Net realized investment gains (losses) Fixed maturity securities trading Net investment income Equity securities (1) Net realized investment gains (losses) Other invested assets - Derivative financial instruments held in a trading portfolio Net investment income Other invested assets - Derivative financial instruments not held in a trading portfolio Net realized investment gains (losses) Life settlement contracts Other revenues Other liabilities - Derivative financial instruments Net realized investment gains (losses) (1) Unrealized gains and losses are reported within AOCI. Securities shown on the previous page may be transferred in or out of levels within the fair value hierarchy based on the availability of observable market information and quoted prices used to determine the fair value of the security. The availability of observable market information and quoted prices varies based on market conditions and trading volume. During the year ended December 31, 2016 there were no transfers between Level 1 and Level 2. There were $63 million of transfers from Level 2 to Level 1 and $52 million from Level 1 to Level 2 during the year ended December 31, 2015 . The Company's policy is to recognize transfers between levels at the beginning of quarterly reporting periods. Valuation Methodologies and Inputs The following section describes the valuation methodologies and relevant inputs used to measure different financial instruments at fair value, including an indication of the level in the fair value hierarchy in which the instruments are generally classified. Fixed Maturity Securities Level 1 securities include highly liquid and exchange traded bonds and redeemable preferred stock, valued using quoted market prices. Level 2 securities include most other fixed maturity securities as the significant inputs are observable in the marketplace. All classes of Level 2 fixed maturity securities are valued using a methodology based on information generated by market transactions involving identical or comparable assets, a discounted cash flow methodology, or a combination of both when necessary. Common inputs for all classes of fixed maturity securities include prices from recently executed transactions of similar securities, marketplace quotes, benchmark yields, spreads off benchmark yields, interest rates and U.S. Treasury or swap curves. Specifically for asset-backed securities, key inputs include prepayment and default projections based on past performance of the underlying collateral and current market data. Fixed maturity securities are primarily assigned to Level 3 in cases where broker/dealer quotes are significant inputs to the valuation and there is a lack of transparency as to whether these quotes are based on information that is observable in the marketplace. Level 3 securities also include private placement debt securities whose fair value is determined using internal models with inputs that are not market observable. Equity Securities Level 1 equity securities include publicly traded securities valued using quoted market prices. Level 2 securities are primarily non-redeemable preferred stocks and common stocks valued using pricing for similar securities, recently executed transactions and other pricing models utilizing market observable inputs. Level 3 securities are primarily priced using broker/dealer quotes and internal models with inputs that are not market observable. Other Invested Assets The fair value of Federal Home Loan Bank of Chicago (FHLBC) stock is equal to par because it can only be redeemed by the FHLBC at par or sold to another member of the FHLBC at par and is classified as Level 2. As of December 31, 2016 and December 31, 2015 , there were approximately $31 million and $27 million respectively of overseas deposits within other invested assets, which can be redeemed at net asset value in 90 days or less. Overseas deposits are excluded from the fair value hierarchy because their fair value is recorded using the net asset value per share (or equivalent) practical expedient. Short Term Investments Securities that are actively traded or have quoted prices are classified as Level 1. These securities include money market funds and treasury bills. Level 2 primarily includes commercial paper, for which all inputs are market observable. Fixed maturity securities purchased within one year of maturity are classified consistent with fixed maturity securities discussed above. Short term investments as presented in the tables above differ from the amounts presented on the Consolidated Balance Sheets because certain short term investments, such as time deposits, are not measured at fair value. Life Settlement Contracts Historically, the fair values of life settlement contracts were determined as the present value of the anticipated death benefits less anticipated premium payments based on contract terms that are distinct for each insured, as well as the Company's own assumptions for mortality, premium expense and the rate of return that a buyer would require on the contracts. As discussed in Note A, Summary of Significant Accounting Policies, because the Company has reached agreement on terms to sell the portfolio of life settlement contracts to a third party, the fair value was written down to reflect the value determined per the agreed terms of sale. Despite the pending sale, as there is not an active market for life settlement contracts, they have been classified as Level 3. Derivative Financial Investments Level 2 securities primarily include the embedded derivative on funds withheld liability. The embedded derivative on funds withheld liability is valued using the change in fair value of the assets supporting the funds withheld liability, which are fixed maturity securities valued with observable inputs. Significant Unobservable Inputs The following tables present quantitative information about the significant unobservable inputs utilized by the Company in the fair value measurements of Level 3 assets. Valuations for assets and liabilities not presented in the tables below are primarily based on broker/dealer quotes for which there is a lack of transparency as to inputs used to develop the valuations. The quantitative detail of these unobservable inputs is neither provided nor reasonably available to the Company. The valuation of life settlement contracts as of December 31, 2016 was based on the terms of the pending sale of the contracts to a third party, therefore the contracts are not included in the table below. December 31, 2016 Estimated Fair Value (In millions) Valuation Technique(s) Unobservable Input(s) Range (Weighted Average) Fixed maturity securities $ 106 Discounted cash flow Credit spread 2% - 40% (4%) December 31, 2015 Estimated Fair Value Valuation Technique(s) Unobservable Input(s) Range (Weighted Average) Fixed maturity securities $ 138 Discounted cash flow Credit spread 3% - 184% (6%) Life settlement contracts 74 Discounted cash flow Discount rate risk premium 9% Mortality assumption 55% - 1676% (164%) For fixed maturity securities, an increase to the credit spread assumptions would result in a lower fair value measurement. For life settlement contracts, an increase in the discount rate risk premium or decrease in the mortality assumption would result in a lower fair value measurement. Financial Assets and Liabilities Not Measured at Fair Value The carrying amount and estimated fair value of the Company's financial assets and liabilities which are not measured at fair value on the Consolidated Balance Sheets are presented in the following tables. December 31, 2016 Carrying Amount Estimated Fair Value (In millions) Level 1 Level 2 Level 3 Total Assets Mortgage loans $ 591 $ — $ — $ 594 $ 594 Liabilities Long term debt $ 2,710 $ — $ 2,952 $ — $ 2,952 December 31, 2015 Carrying Estimated Fair Value (In millions) Level 1 Level 2 Level 3 Total Assets Mortgage loans $ 678 $ — $ — $ 688 $ 688 Liabilities Short term debt $ 350 $ — $ 360 $ — $ 360 Long term debt 2,210 — 2,433 — 2,433 The following methods and assumptions were used to estimate the fair value of these financial assets and liabilities. The fair values of mortgage loans were based on the present value of the expected future cash flows discounted at the current interest rate for origination of similar quality loans, adjusted for specific loan risk. The Company's senior notes and debentures were valued based on observable market prices. The fair value for other debt was estimated using discounted cash flows based on current incremental borrowing rates for similar borrowing arrangements. The carrying amounts reported on the Consolidated Balance Sheets for Cash, Short term investments not carried at fair value, Accrued investment income and certain Other assets and Other liabilities approximate fair value due to the short term nature of these items. These assets and liabilities are not listed in the tables above.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Income Taxes	Note D . Income Taxes The CNA Tax Group is included in the consolidated federal income tax return of Loews and its eligible subsidiaries. Loews and the Company have agreed that for each taxable year, the Company will 1) be paid by Loews the amount, if any, by which the Loews consolidated federal income tax liability is reduced by virtue of the inclusion of the CNA Tax Group in the Loews consolidated federal income tax return, or 2) pay to Loews an amount, if any, equal to the federal income tax that would have been payable by the CNA Tax Group filing a separate consolidated tax return. In the event that Loews should have a net operating loss in the future computed on the basis of filing a separate consolidated tax return without the CNA Tax Group, the Company may be required to repay tax recoveries previously received from Loews. This agreement may be canceled by either party upon 30 days written notice. For the years ended December 31, 2016 , 2015 and 2014 , the Company paid $142 million , $256 million and $287 million to Loews related to federal income taxes. For 2014 through 2016 , the Internal Revenue Service (IRS) has accepted Loews and the Company into the Compliance Assurance Process (CAP), which is a voluntary program for large corporations. Under CAP, the IRS conducts a real-time audit and works contemporaneously with the Company to resolve any issues prior to the filing of the tax return. The Company believes that this approach should reduce tax-related uncertainties, if any. As of December 31, 2016 and 2015 , there were no unrecognized tax benefits. The Company recognizes interest accrued related to: 1) unrecognized tax benefits in Interest expense and 2) tax refund claims in Other revenues on the Consolidated Statements of Operations. The Company recognizes penalties (if any) in Income tax (expense) benefit on the Consolidated Statements of Operations. During 2016 , 2015 and 2014 the Company recognized no interest and no penalties. There were no amounts accrued for interest or penalties as of December 31, 2016 or 2015 . The following table presents a reconciliation between the Company's federal income tax expense at statutory rates and the recorded income tax expense, excluding discontinued operations. Years ended December 31 (In millions) 2016 2015 2014 Income tax expense at statutory rates $ (398 ) $ (192 ) $ (423 ) Tax benefit from tax exempt income 124 123 119 Foreign taxes and credits 3 9 (6 ) Other tax expense (7 ) (10 ) (9 ) Income tax expense $ (278 ) $ (70 ) $ (319 ) Provision has not been made for the Company's investment in certain subsidiaries for which the Company intends to invest the undistributed earnings indefinitely. As of December 31, 2016 , the Company has not provided deferred taxes of $1 million on $3 million of undistributed earnings related to a foreign subsidiary. The following table presents the current and deferred components of the Company's income tax expense, excluding discontinued operations. Years ended December 31 (In millions) 2016 2015 2014 Current tax expense $ (142 ) $ (220 ) $ (318 ) Deferred tax benefit (expense) (136 ) 150 (1 ) Total income tax expense $ (278 ) $ (70 ) $ (319 ) Total income tax presented above includes foreign tax expense of approximately $9 million , $14 million and $24 million related to income from continuing foreign operations of approximately $51 million , $71 million and $66 million for the years ended December 31, 2016 , 2015 and 2014 . The deferred tax effects of the significant components of the Company's deferred tax assets and liabilities are presented in the following table. December 31 (In millions) 2016 2015 Deferred Tax Assets: Insurance reserves: Property and casualty claim and claim adjustment expense reserves $ 125 $ 178 Unearned premium reserves 206 230 Receivables 27 29 Employee benefits 272 281 Life settlement contracts 56 48 Deferred retroactive reinsurance benefit 117 84 Investment valuation differences — 29 Other assets 148 142 Gross deferred tax assets 951 1,021 Deferred Tax Liabilities: Investment valuation differences 57 — Deferred acquisition costs 120 117 Net unrealized gains 309 202 Other liabilities 86 64 Gross deferred tax liabilities 572 383 Net deferred tax asset $ 379 $ 638 As of December 31, 2016 , the CNA Tax Group had no loss carryforwards or tax credit carryforwards. Although realization of deferred tax assets is not assured, management believes it is more likely than not that the recognized net deferred tax asset will be realized through recoupment of ordinary and capital taxes paid in prior carryback years and through future earnings, reversal of existing temporary differences and available tax planning strategies. As a result, no valuation allowance was recorded as of December 31, 2016 or 2015 .

Claim and Claim Adjustment Expe

Claim and Claim Adjustment Expense Reserves	12 Months Ended
	Dec. 31, 2016
Liability for Claims and Claims Adjustment Expense [Abstract]
Claim and Claim Adjustment Expense Reserves	Note E . Claim and Claim Adjustment Expense Reserves The Company's property and casualty insurance claim and claim adjustment expense reserves represent the estimated amounts necessary to resolve all outstanding claims, including IBNR claims as of the reporting date. The Company's reserve projections are based primarily on detailed analysis of the facts in each case, the Company's experience with similar cases and various historical development patterns. Consideration is given to such historical patterns as claim reserving trends and settlement practices, loss payments, pending levels of unpaid claims and product mix, as well as court decisions, economic conditions, including inflation, and public attitudes. All of these factors can affect the estimation of claim and claim adjustment expense reserves. Establishing claim and claim adjustment expense reserves, including claim and claim adjustment expense reserves for catastrophic events that have occurred, is an estimation process. Many factors can ultimately affect the final settlement of a claim and, therefore, the necessary reserve. Changes in the law, results of litigation, medical costs, the cost of repair materials and labor rates can all affect ultimate claim costs. In addition, time can be a critical part of reserving determinations since the longer the span between the incidence of a loss and the payment or settlement of the claim, the more variable the ultimate settlement amount can be. Accordingly, short-tail claims, such as property damage claims, tend to be more reasonably estimable than long-tail claims, such as workers' compensation, general liability and professional liability claims. Adjustments to prior year reserve estimates, if necessary, are reflected in the results of operations in the period that the need for such adjustments is determined. There can be no assurance that the Company's ultimate cost for insurance losses will not exceed current estimates. Catastrophes are an inherent risk of the property and casualty insurance business and have contributed to material period-to-period fluctuations in the Company's results of operations and/or equity. The Company reported catastrophe losses, net of reinsurance, of $165 million , $141 million and $156 million for the years ended December 31, 2016 , 2015 and 2014 . Catastrophe losses in 2016 related primarily to U.S. weather-related events and the Fort McMurray wildfires. In developing claim and claim adjustment expense (“loss” or “losses”) reserve estimates, our actuaries perform detailed reserve analyses that are staggered throughout the year. Every reserve group is reviewed at least once during the year. The analyses generally review losses gross of ceded reinsurance and apply the ceded reinsurance terms to the gross estimates to establish estimates net of reinsurance. In addition to the detailed analyses, we review actual loss emergence for all products each quarter. In developing the loss reserve estimates for property and casualty contracts, we generally project ultimate losses using several common actuarial methods as listed below. We review the various indications from the various methods and apply judgment to select an actuarial point estimate. The indicated required reserve is the difference between the selected ultimate loss and the inception-to-date paid losses. The difference between the selected ultimate loss and the case incurred or reported loss is IBNR. IBNR includes a provision for development on known cases as well as a provision for late reported incurred claims. Further, the Company does not establish case reserves for allocated loss adjustment expenses (ALAE), therefore all ALAE reserves are included in our estimate of IBNR. The most frequently utilized methods to project ultimate losses include the following: • paid development; • incurred development; • loss ratio; • Bornhuetter-Ferguson using premiums and paid loss; • Bornhuetter-Ferguson using premiums and incurred loss; • frequency times severity; and • stochastic modeling. The paid development method estimates ultimate losses by reviewing paid loss patterns and applying them to accident years with further expected changes in paid loss. The incurred development method is similar to the paid development method, but it uses case incurred losses instead of paid losses. The loss ratio method multiplies premiums by an expected loss ratio to produce ultimate loss estimates for each accident year. The Bornhuetter-Ferguson using premiums and paid loss method is a combination of the paid development approach and the loss ratio approach. This method normally determines expected loss ratios similar to the approach used to estimate the expected loss ratio for the loss ratio method. The Bornhuetter-Ferguson using premiums and incurred loss method is similar to the Bornhuetter-Ferguson using premiums and paid loss method except that it uses case incurred losses. The frequency times severity method multiplies a projected number of ultimate claims by an estimated ultimate average loss for each accident year to produce ultimate loss estimates. Stochastic modeling produces a range of possible outcomes based on varying assumptions related to the particular product being modeled. For many exposures, especially those that can be considered long-tail, a particular accident or policy year may not have a sufficient volume of paid losses to produce a statistically reliable estimate of ultimate losses. In such a case, our actuaries typically assign more weight to the incurred development method than to the paid development method. As claims continue to settle and the volume of paid loss increases, the actuaries may assign additional weight to the paid development method. For most of our products, even the incurred losses for accident or policy years that are early in the claim settlement process will not be of sufficient volume to produce a reliable estimate of ultimate losses. In these cases, we may not assign any weight to the paid and incurred development methods. We will use the loss ratio, Bornhuetter-Ferguson and frequency times severity methods. For short-tail exposures, the paid and incurred development methods can often be relied on sooner, primarily because our history includes a sufficient number of years to cover the entire period over which paid and incurred losses are expected to change. However, we may also use the loss ratio, Bornhuetter-Ferguson and frequency times severity methods for short-tail exposures. For other more complex reserve groups where the above methods may not produce reliable indications, we use additional methods tailored to the characteristics of the specific situation. Reserves for policyholder benefits for our Life & Group Non-Core segment, which primarily includes long term care, are based on actuarial assumptions which include estimates of morbidity, persistency, discount rates and expenses over the life of the contracts. Under GAAP, the best estimates of the actuarial assumptions at the date the contract was issued are locked-in throughout the life of the contract, unless a premium deficiency develops, which occurred in 2015. As a result, the Company updated the assumptions to represent management’s best estimates at the time of the premium deficiency and these revised assumptions are locked-in unless another premium deficiency is identified. Certain claim liabilities are more difficult to estimate and have differing methodologies and considerations which are described below. Our mass tort and A&EP reserving methodologies are similar as both are based on detailed account reviews of all large accounts with estimates based on ultimate payments considering the applicable law and coverage litigation. These reserves are subject to greater inherent variability than is typical of the remainder of the Company’s reserves due to, among other things, a general lack of sufficiently detailed data, expansion of the population being held responsible for these exposures and significant unresolved legal issues such as the existence of coverage and the definition of an occurrence. Our actuarial reserve analyses result in point estimates. Each quarter, the results of detailed reserve reviews are summarized and discussed with our senior management to determine management's best estimate of reserves. Senior management considers many factors in making this decision. The factors include, but are not limited to, the historical pattern and volatility of the actuarial indications, the sensitivity of the actuarial indications to changes in paid and incurred loss patterns, the consistency of claims handling processes, the consistency of case reserving practices, changes in our pricing and underwriting, pricing and underwriting trends in the insurance market and legal, judicial, social and economic trends. Our recorded reserves reflect our best estimate as of a particular point in time based upon known facts, consideration of the factors cited above and our judgment. The carried reserve may differ from the actuarial point estimate as the result of our consideration of the factors noted above as well as the potential volatility of the projections associated with the specific product being analyzed and other factors affecting claims costs that may not be quantifiable through traditional actuarial analysis. The loss reserve development tables presented herein illustrate the change over time of reserves established for claim and allocated claim adjustment expenses arising from short duration insurance contracts for certain lines of business within our property & casualty segments. Not all lines of business or segments are presented based on their context to the Company's overall loss reserves, calendar year reserve development, or calendar year net earned premiums. Insurance contracts are considered to be short duration contracts when the contracts are not expected to remain in force for an extended period of time. The Cumulative Net Incurred Claim and Allocated Claim Adjustment Expenses tables, reading across, show the cumulative net incurred claim and allocated claim adjustment expenses relating to each accident year at the end of the stated calendar year. Changes in the cumulative amount across time are the result of the Company's expanded awareness of additional facts and circumstances that pertain to the unsettled claims. The Cumulative Net Paid Claims and Allocated Claim Adjustment Expenses tables, reading across, show the cumulative amount paid for claims in each accident year as of the end of the stated calendar year. The Net Strengthening or (Releases) of Prior Accident Year Reserves tables, reading across, show the net increase or decrease in the cumulative net incurred accident year claim and allocated claim adjustment expenses during each stated calendar year and indicates whether the reserves for that accident year were strengthened or released. The information in the tables is reported on a net basis after reinsurance and does not include unallocated claim and claim adjustment expenses or the effects of discounting. The information contained in the years preceding the current calendar year is unaudited. Information contained in the tables pertaining to our International segment has been presented at the year-end 2016 foreign currency exchange rates for all periods presented to remove the effects of foreign currency exchange rate changes between calendar years. The Company has presented development information for the Hardy business prospectively from the date of acquisition and is presented as a separate table within our International segment. To the extent the Company enters into a commutation, the transaction is reported on a prospective basis. To the extent that the Company enters into a disposition, the effects of the disposition are reported on a retrospective basis by removing the balances associated with the disposed of business. The amounts reported for the cumulative number of reported claims include direct and assumed open and closed claims by accident year at the claimant level. The number excludes claim counts for claims within a policy deductible where the insured is responsible for payment of losses in the deductible layer. Claim count data for certain assumed reinsurance contracts is unavailable. In the loss reserve development tables, IBNR includes reserves for incurred but not reported losses and expected development on case reserves. The Company does not case reserve ALAE, therefore all ALAE reserves are also included in the estimate of IBNR. Liability for Unpaid Claim and Claim Adjustment Expenses Rollforward The following table presents a reconciliation between beginning and ending claim and claim adjustment expense reserves, including claim and claim adjustment expense reserves of the Life & Group Non-Core segment. As of or for the years ended December 31 (In millions) 2016 2015 2014 Reserves, beginning of year: Gross $ 22,663 $ 23,271 $ 24,089 Ceded 4,087 4,344 4,972 Net reserves, beginning of year 18,576 18,927 19,117 Change in net reserves due to acquisition (disposition) of subsidiaries — — (13 ) Net incurred claim and claim adjustment expenses: Provision for insured events of current year 5,025 4,934 5,043 Decrease in provision for insured events of prior years (342 ) (255 ) (36 ) Amortization of discount 175 166 161 Total net incurred (1) 4,858 4,845 5,168 Net payments attributable to: Current year events (967 ) (856 ) (945 ) Prior year events (4,167 ) (4,089 ) (4,355 ) Total net payments (5,134 ) (4,945 ) (5,300 ) Foreign currency translation adjustment and other (51 ) (251 ) (45 ) Net reserves, end of year 18,249 18,576 18,927 Ceded reserves, end of year 4,094 4,087 4,344 Gross reserves, end of year $ 22,343 $ 22,663 $ 23,271 (1) Total net incurred above does not agree to Insurance claims and policyholders' benefits as reflected on the Consolidated Statements of Operations due to amounts related to retroactive reinsurance deferred gain accounting, uncollectible reinsurance and loss deductible receivables, and benefit expenses related to future policy benefits, which are not reflected in the table above. The following tables present the gross and net carried reserves. December 31, 2016 Specialty Commercial International Life & Group Non-Core Corporate & Other Non-Core Total (In millions) Gross Case Reserves $ 1,871 $ 4,661 $ 632 $ 3,172 $ 1,524 $ 11,860 Gross IBNR Reserves 4,278 4,233 696 186 1,090 10,483 Total Gross Carried Claim and Claim Adjustment Expense Reserves $ 6,149 $ 8,894 $ 1,328 $ 3,358 $ 2,614 $ 22,343 Net Case Reserves $ 1,681 $ 4,353 $ 548 $ 2,951 $ 94 $ 9,627 Net IBNR Reserves 3,723 3,952 653 158 136 8,622 Total Net Carried Claim and Claim Adjustment Expense Reserves $ 5,404 $ 8,305 $ 1,201 $ 3,109 $ 230 $ 18,249 December 31, 2015 Specialty Commercial International Life & Group Non-Core Corporate & Other Non-Core Total (In millions) Gross Case Reserves $ 2,011 $ 4,975 $ 622 $ 2,973 $ 1,521 $ 12,102 Gross IBNR Reserves 4,258 4,208 725 247 1,123 10,561 Total Gross Carried Claim and Claim Adjustment Expense Reserves $ 6,269 $ 9,183 $ 1,347 $ 3,220 $ 2,644 $ 22,663 Net Case Reserves $ 1,810 $ 4,651 $ 531 $ 2,714 $ 130 $ 9,836 Net IBNR Reserves 3,758 3,925 688 216 153 8,740 Total Net Carried Claim and Claim Adjustment Expense Reserves $ 5,568 $ 8,576 $ 1,219 $ 2,930 $ 283 $ 18,576 Net Prior Year Development Changes in estimates of claim and allocated claim adjustment expense reserves and premium accruals, net of reinsurance, for prior years are defined as net prior year development. These changes can be favorable or unfavorable. The following tables and discussion present the net prior year development recorded for Specialty, Commercial, International and Corporate & Other Non-Core segments. Year ended December 31, 2016 (In millions) Specialty Commercial International Corporate & Other Non-Core Total Pretax (favorable) unfavorable net prior year claim and allocated claim adjustment expense reserve development $ (287 ) $ 55 $ (58 ) $ 2 $ (288 ) Pretax (favorable) unfavorable premium development (18 ) (2 ) (6 ) — (26 ) Total pretax (favorable) unfavorable net prior year development $ (305 ) $ 53 $ (64 ) $ 2 $ (314 ) Year ended December 31, 2015 (In millions) Specialty Commercial International Corporate & Other Non-Core Total Pretax (favorable) unfavorable net prior year claim and allocated claim adjustment expense reserve development $ (141 ) $ (15 ) $ (54 ) $ — $ (210 ) Pretax (favorable) unfavorable premium development (11 ) (15 ) 18 — (8 ) Total pretax (favorable) unfavorable net prior year development $ (152 ) $ (30 ) $ (36 ) $ — $ (218 ) Year ended December 31, 2014 (In millions) Specialty Commercial International Corporate & Other Non-Core Total Pretax (favorable) unfavorable net prior year claim and allocated claim adjustment expense reserve development $ (136 ) $ 176 $ (59 ) $ (2 ) $ (21 ) Pretax (favorable) unfavorable premium development (13 ) (20 ) 2 (1 ) (32 ) Total pretax (favorable) unfavorable net prior year development $ (149 ) $ 156 $ (57 ) $ (3 ) $ (53 ) Favorable net prior year development of $45 million , $50 million and $14 million was recorded in the Life & Group Non-Core segment for the years ended December 31, 2016 , 2015 and 2014 . The favorable net prior year development for the year ended December 31, 2016 was driven by a reserve release resulting from the annual experience study of long term care claim reserves which indicated lower than expected claim severity. Premium development can occur in the property and casualty business when there is a change in exposure on auditable policies or when premium accruals differ from processed premium. Audits on policies usually occur in a period after the expiration date of the policy. Specialty The following table presents further detail of the net prior year claim and allocated claim adjustment expense reserve development (development) recorded for the Specialty segment. Years ended December 31 (In millions) 2016 2015 2014 Pretax (favorable) unfavorable development: Medical Professional Liability $ (37 ) $ (43 ) $ 39 Other Professional Liability and Management Liability (130 ) — (87 ) Surety (63 ) (69 ) (82 ) Warranty 4 (2 ) (2 ) Other (61 ) (27 ) (4 ) Total pretax (favorable) unfavorable development $ (287 ) $ (141 ) $ (136 ) 2016 Favorable development for medical professional liability was primarily due to lower than expected severities for individual healthcare professionals, allied facilities and hospitals in accident years 2011 and prior and better than expected severity in medical products liability in accident years 2010 through 2015. This was partially offset by unfavorable development in accident years 2012 and 2013 related to higher than expected large loss emergence in hospitals and higher than expected frequency and severity in accident years 2014 and 2015 in our aging services business. Favorable development in other professional liability and management liability was primarily due to favorable settlements on closed claims and lower than expected frequency of claims in accident years 2010 through 2014 related to professional services and financial institutions. This was partially offset by unfavorable development related to a specific financial institutions claim in accident year 2014, higher management liability severities in accident year 2015, and deterioration on credit crises-related claims in accident year 2009. Favorable development in surety coverages was primarily due to lower than expected frequency of large losses in accident years 2014 and prior. Favorable development for other coverages provided to Specialty customers was due to better than expected claim frequency and claim severity in commercial lines coverages in accident years 2010 through 2015. 2015 Overall, favorable development for medical professional liability was related to lower than expected severity in accident years 2012 and prior. Unfavorable development was recorded related to increased claim frequency and severity in the aging services business in accident years 2013 and 2014. Favorable development in other professional liability and management liability related to better than expected large loss emergence in financial institutions primarily in accident years 2011 through 2014. Additional favorable development related to lower than expected severity for professional services in accident years 2011 and prior. Unfavorable development was recorded related to increased frequency of large claims on public company management liability in accident years 2012 through 2014. Favorable development for surety coverages was primarily due to lower than expected frequency of large losses in accident years 2013 and prior. Favorable development for other coverages was due to better than expected claim frequency in property coverages provided to Specialty customers in accident year 2014. 2014 Unfavorable development for medical professional liability was primarily related to increased frequency of large medical products liability class action lawsuits in accident years 2012 and prior and increased frequency of other large medical professional liability losses in accident years 2011 through 2013. Overall, favorable development for other professional liability and management liability was related to better than expected severity in accident years 2008 through 2011, including favorable outcomes on individual large claims. Additional favorable development related to lower than expected frequency in accident years 2011 through 2013. Unfavorable development was recorded due to higher than expected severity in financial institution and professional service coverages in accident years 2009 through 2011. Favorable development for surety coverages was primarily due to better than expected large loss emergence in accident years 2012 and prior. Specialty - Line of Business Composition The table below provides the line of business composition of the net liability for unpaid claim and claim adjustment expenses for the Specialty segment. As of December 31 (In millions) 2016 Net liability for unpaid claim and claim adjustment expenses: Medical Professional Liability $ 1,779 Other Professional Liability and Management Liability 3,063 Surety 394 Warranty 37 Other 131 Total net liability for unpaid claim and claim adjustment expenses $ 5,404 Specialty - Medical Professional Liability Cumulative Net Incurred Claim and Allocated Claim Adjustment Expenses are presented in the following table. As of December 31 Calendar Year As of December 31, 2016 (In millions, except reported claims data) 2007 (1) 2008 (1) 2009 (1) 2010 (1) 2011 (1) 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 IBNR Cumulative Number of Claims Accident Year 2007 $ 448 $ 452 $ 444 $ 427 $ 395 $ 391 $ 390 $ 401 $ 399 $ 385 $ 9 12,122 2008 426 451 496 480 468 468 467 455 442 9 14,094 2009 462 469 494 506 480 471 463 432 12 15,573 2010 483 478 478 486 470 446 403 16 15,206 2011 486 492 507 533 501 491 23 17,428 2012 526 529 575 567 559 47 18,375 2013 534 540 560 567 95 19,565 2014 511 548 585 165 19,286 2015 480 539 278 16,798 2016 469 400 11,600 Total $ 4,872 $ 1,054 Cumulative Net Paid Claims and Allocated Claim Adjustment Expenses are presented in the following table. As of December 31 Calendar Year (In millions) 2007 (1) 2008 (1) 2009 (1) 2010 (1) 2011 (1) 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 Accident Year 2007 $ 11 $ 68 $ 134 $ 201 $ 247 $ 296 $ 326 $ 352 $ 364 $ 365 2008 9 90 207 282 332 377 395 409 428 2009 9 75 180 278 328 353 377 396 2010 11 93 186 273 338 361 371 2011 18 121 225 315 379 407 2012 15 121 236 359 428 2013 18 121 259 364 2014 25 149 274 2015 22 105 2016 18 Total $ 3,156 Net liability for unpaid claim and allocated claim adjustment expenses for the accident years presented $ 1,716 Net liability for unpaid claim and claim adjustment expenses for accident years prior to 2007 30 Liability for unallocated claim adjustment expenses for accident years presented 33 Total net liability for unpaid claim and claim adjustment expenses $ 1,779 Net strengthening or (releases) of prior accident year reserves is presented in the following table. For the years ended December 31 Calendar Year (In millions) 2008 (1) 2009 (1) 2010 (1) 2011 (1) 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 Total Accident Year 2007 $ 4 $ (8 ) $ (17 ) $ (32 ) $ (4 ) $ (1 ) $ 11 $ (2 ) $ (14 ) $ (63 ) 2008 25 45 (16 ) (12 ) — (1 ) (12 ) (13 ) 16 2009 7 25 12 (26 ) (9 ) (8 ) (31 ) (30 ) 2010 (5 ) — 8 (16 ) (24 ) (43 ) (80 ) 2011 6 15 26 (32 ) (10 ) 5 2012 3 46 (8 ) (8 ) 33 2013 6 20 7 33 2014 37 37 74 2015 59 59 Total net development for the accident years presented above $ 63 $ (29 ) $ (16 ) Total net development for accident years prior to 2007 (24 ) (14 ) (21 ) Total $ 39 $ (43 ) $ (37 ) (1) Data presented for these calendar years is required supplemental information, which is unaudited. Specialty - Other Professional Liability and Management Liability Cumulative Net Incurred Claim and Allocated Claim Adjustment Expenses are presented in the following table. As of December 31 Calendar Year As of December 31, 2016 (In millions, except reported claims data) 2007 (1) 2008 (1) 2009 (1) 2010 (1) 2011 (1) 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 IBNR Cumulative Number of Claims Accident Year 2007 $ 804 $ 817 $ 806 $ 754 $ 734 $ 724 $ 704 $ 681 $ 662 $ 662 $ 13 16,011 2008 916 933 954 924 915 880 850 845 827 35 16,326 2009 829 873 903 898 891 900 895 903 50 17,263 2010 825 827 850 848 846 836 823 39 17,796 2011 876 904 933 948 944 910 107 18,620 2012 907 894 876 870 833 107 18,228 2013 844 841 879 840 137 17,324 2014 841 859 854 306 16,886 2015 847 851 478 16,391 2016 859 742 15,045 Total $ 8,362 $ 2,014 Cumulative Net Paid Claims and Allocated Claim Adjustment Expenses are presented in the following table. As of December 31 Calendar Year (In millions) 2007 (1) 2008 (1) 2009 (1) 2010 (1) 2011 (1) 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 Accident Year 2007 $ 32 $ 162 $ 307 $ 397 $ 472 $ 524 $ 564 $ 585 $ 593 $ 614 2008 39 181 376 515 600 641 678 719 741 2009 37 195 358 550 638 719 769 798 2010 31 203 404 541 630 670 721 2011 71 313 502 604 682 726 2012 57 248 398 570 648 2013 51 240 426 583 2014 51 212 375 2015 48 209 2016 60 Total $ 5,475 Net liability for unpaid claim and allocated claim adjustment expenses for the accident years presented $ 2,887 Net liability for unpaid claim and claim adjustment expenses for accident years prior to 2007 104 Liability for unallocated claim adjustment expenses for accident years presented 72 Total net liability for unpaid claim and claim adjustment expenses $ 3,063 Net strengthening or (releases) of prior accident year reserves is presented in the following table. For the years ended December 31 Calendar Year (In millions) 2008 (1) 2009 (1) 2010 (1) 2011 (1) 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 Total Accident Year 2007 $ 13 $ (11 ) $ (52 ) $ (20 ) $ (10 ) $ (20 ) $ (23 ) $ (19 ) $ — $ (142 ) 2008 17 21 (30 ) (9 ) (35 ) (30 ) (5 ) (18 ) (89 ) 2009 44 30 (5 ) (7 ) 9 (5 ) 8 74 2010 2 23 (2 ) (2 ) (10 ) (13 ) (2 ) 2011 28 29 15 (4 ) (34 ) 34 2012 (13 ) (18 ) (6 ) (37 ) (74 ) 2013 (3 ) 38 (39 ) (4 ) 2014 18 (5 ) 13 2015 4 4 Total net development for the accident years presented above $ (52 ) $ 7 $ (134 ) Total net development for accident years prior to 2007 (35 ) (7 ) 4 Total $ (87 ) $ — $ (130 ) (1) Data presented for these calendar years is required supplemental information, which is unaudited. Specialty - Surety Cumulative Net Incurred Claim and Allocated Claim Adjustment Expenses are presented in the following table. As of December 31 Calendar Year As of December 31, 2016 (In millions, except reported claims data) 2007 (1) 2008 (1) 2009 (1) 2010 (1) 2011 (1) 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 IBNR Cumulative Number of Claims Accident Year 2007 $ 98 $ 107 $ 81 $ 57 $ 59 $ 56 $ 51 $ 49 $ 49 $ 50 $ — 6,270 2008 114 114 73 68 61 52 48 45 44 — 7,153 2009 114 114 103 85 68 59 52 53 1 6,654 2010 112 112 111 84 76 66 63 8 5,943 2011 120 121 116 87 75 70 9 5,760 2012 120 122 98 70 52 16 5,473 2013 120 121 115 106 24 4,890 2014 123 124 94 51 4,737 2015 131 131 100 4,279 2016 124 110 2,902 Total $ 787 $ 319 Cumulative Net Paid Claims and Allocated Claim Adjustment Expenses are presented in the following table. As of December 31 Calendar Year (In millions) 2007 (1) 2008 (1) 2009 (1) 2010 (1) 2011 (1) 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 Accident Year 2007 $ 12 $ 30 $ 40 $ 45 $ 46 $ 46 $ 46 $ 48 $ 49 $ 50 2008 9 27 35 39 42 43 43 43 43 2009 13 24 34 41 43 45 46 47 2010 13 34 50 55 57 58 55 2011 19 42 55 58 60 60 2012 5 32 34 35 35 2013 16 40 69 78 2014 7 30 38 2015 7 26 2016 5 Total $ 437 Net liability for unpaid claim and allocated claim adjustment expenses for the accident years presented $ 350 Net liability for unpaid claim and claim adjustment expenses for accident years prior to 2007 16 Liability for unallocated claim adjustment expenses for accident years presented 28 Total net liability for unpaid claim and claim adjustment expenses $ 394 Net strengthening or (releases) of prior accident year reserves is presented in the following table. For the years ended December 31 Calendar Year (In millions) 2008 (1) 2009 (1) 2010 (1) 2011 (1) 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 Total Accident Year 2007 $ 9 $ (26 ) $ (24 ) $ 2 $ (3 ) $ (5 ) $ (2 ) $ — $ 1 $ (48 ) 2008 — (41 ) (5 ) (7 ) (9 ) (4 ) (3 ) (1 ) (70 ) 2009 — (11 ) (18 ) (17 ) (9 ) (7 ) 1 (61 ) 2010 — (1 ) (27 ) (8 ) (10 ) (3 ) (49 ) 2011 1 (5 ) (29 ) (12 ) (5 ) (50 ) 2012 2 (24 ) (28 ) (18 ) (68 ) 2013 1 (6 ) (9 ) (14 ) 2014 1 (30 ) (29 ) 2015 — — Total net development for the accident years presented above $ (75 ) $ (65 ) $ (64 ) Total net development for accident years prior to 2007 (7 ) (4 ) 1 Total $ (82 ) $ (69 ) $ (63 ) (1) Data presented for these calendar years is required supplemental information, which is unaudited. Commercial The following table presents further detail of the development recorded for the Commercial segment. Years ended December 31 (In millions) 2016 2015 2014 Pretax (favorable) unfavorable development: Commercial Auto $ (46 ) $ (22 ) $ 31 General Liability (28 ) (33 ) 45 Workers' Compensation 150 80 139 Property and Other (21 ) (40 ) (39 ) Total pretax (favorable) unfavorable development $ 55 $ (15 ) $ 176 2016 Favorable development for commercial auto was primarily due to favorable settlements on claims in accident years 2010 through 2014 and lower than expected severities in accident years 2012 through 2015. Favorable development for general liability was primarily due to better than expected claim settlements in accident years 2012 through 2014 and better than expected severity on umbrella claims in accident years 2010 through 2013. This was partially offset by unfavorable development related to an increase in reported claims prior to the closing of the three year window set forth by the Minnesota Child Victims Act in accident years 2006 and prior. Unfavorable development for workers' compensation was primarily due to higher than expected severity for Defense Base Act contractors that largely resulted from a reduction of expected future recoveries from the US Department of Labor under the War Hazard Act. Further unfavorable development was due to the impact of recent Florida court rulings for accident years 2008 through 2015. These were partially offset by favorable development related to lower than expected frequencies related to our ongoing Middle Market and Small Business results for accident years 2009 through 2014. Favorable development for property and other was primarily due to better than expected loss frequency in accident years 2013 through 2015. This was partially offset by unfavorable development related to higher than expected severity from a fourth quarter 2015 catastrophe event. 2015 Favorable development for commercial auto was primarily due to lower than expected severity in accident years 2009 through 2014. Favorable development for general liability was primarily due to favorable settlements on claims in accident years 2010 through 2013. Unfavorable development for workers’ compensation was primarily due to higher than expected severity related to Defense Base Act contractors in accident years 2008 through 2014. Favorable development for property and other was primarily due to better than expected claim emergence from 2012 and 2014 catastrophe events and better than expected frequency of large claims in accident year 2014. The year ended December 31, 2015 also included unfavorable loss development related to extra contractual obligation losses and losses associated with premium development. 2014 Unfavor

Legal Proceedings, Commitments

Legal Proceedings, Commitments and Contingencies, and Guarantees	12 Months Ended
	Dec. 31, 2016
Legal Proceedings, Commitments and Contingencies, and Guarantees [Abstract]
Legal Proceedings, Commitments and Contingencies, and Guarantees [Text Block]	Note F . Legal Proceedings, Commitments and Contingencies, and Guarantees CNA 401(k) Plus Plan Litigation In September 2016, a class action lawsuit was filed against CCC, Continental Assurance Company (CAC), CNAF, the Investment Committee of the CNA 401(k) Plus Plan, The Northern Trust Company and John Does 1-10 (collectively Defendants) over the CNA 401(k) Plus Plan. The complaint alleges that defendants breached fiduciary duties to the CNA 401(k) Plus Plan and caused prohibited transactions in violation of the Employee Retirement Income Security Act of 1974 when the CNA 401(k) Plus Plan's Fixed Income Fund’s annuity contract with CAC was canceled. The plaintiff alleges he and a proposed class of the CNA 401(k) Plus Plan participants who had invested in the Fixed Income Fund suffered lower returns in their CNA 401(k) Plus Plan investments as a consequence of these alleged violations and seeks relief on behalf of the putative class. Management has only recently begun evaluating the lawsuit as this litigation is in its preliminary stages, and as of yet no class has been certified. CCC and the other defendants are contesting the case and management currently is unable to predict the final outcome or the impact on the Company’s financial condition, results of operations, or cash flows. As of December 31, 2016 , the likelihood of loss is reasonably possible, but the amount of loss, if any, cannot be estimated at this stage of the litigation. Small Business Premium Rate Adjustment Contingency The Company recently identified rating errors related to its multi-peril package product within its Small Business unit. The Company recorded a charge which reduced Earned premium by $16 million in anticipation of voluntarily issuing $30 million of premium refunds related to affected policies written from December 1, 2015 through December 31, 2016. Earned premium in 2017 will be negatively impacted by the portion of the $30 million that has not yet been earned through December 31, 2016 and the expected refund amount will increase further because of premium written in 2017 prior to the Company’s actions to correct its rating process. The Company is currently in dialogue with state regulators and providing them with details regarding the anticipated premium refunds and other corrective actions. The Company is reviewing other business lines to determine whether other similar issues exist. Fines or penalties related to the foregoing or further refunds which may be required are reasonably possible, but the amount of such losses, if any, cannot be estimated at this time. Other Litigation The Company is a party to other routine litigation incidental to its business, which, based on the facts and circumstances currently known, is not material to the Consolidated Financial Statements. Commitments and Contingencies The Company holds an investment in a real estate joint venture in which the Company, on a joint and several basis with the other unrelated shareholders, guaranteed to fund operating deficits of the joint venture and an operating lease for an office building entered into by the venture. The lease was terminated in March 2016. In the event that the other parties to the joint venture are unable to meet their commitments in funding this joint venture, the Company would be required to assume future obligations, primarily related to the wind-down of the lease and joint venture. The Company does not believe it is likely that it will be required to do so. However, as of December 31, 2016 , the maximum potential loss that the Company could be required to pay under this guarantee, in excess of amounts already recorded, was approximately $11 million . If the Company were required to assume future obligations, the Company would have the right to pursue reimbursement from the other shareholders. Guarantees As of December 31, 2016 and December 31, 2015 , the Company had recorded liabilities of approximately $5 million related to guarantee and indemnification agreements. Management believes that it is not likely that any future indemnity claims will be significantly greater than the amounts recorded. In the course of selling business entities and assets to third parties, the Company agreed to guarantee the performance of certain obligations of a previously owned subsidiary and to indemnify purchasers for losses arising out of breaches of representation and warranties with respect to the business entities or assets sold, including, in certain cases, losses arising from undisclosed liabilities or certain named litigation. Such guarantee and indemnification agreements in effect for sales of business entities, assets and third-party loans may include provisions that survive indefinitely. As of December 31, 2016 , the aggregate amount related to quantifiable guarantees was $375 million and the aggregate amount related to quantifiable indemnification agreements was $258 million . Should the Company be required to make payments under the guarantee, it would have the right to seek reimbursement in certain cases from an affiliate of a previously owned subsidiary. In addition, the Company has agreed to provide indemnification to third-party purchasers for certain losses associated with sold business entities or assets that are not limited by a contractual monetary amount. As of December 31, 2016 , the Company had outstanding unlimited indemnifications in connection with the sales of certain of its business entities or assets that included tax liabilities arising prior to a purchaser's ownership of an entity or asset, defects in title at the time of sale, employee claims arising prior to closing and in some cases losses arising from certain litigation and undisclosed liabilities. Certain provisions of the indemnification agreements survive indefinitely, while others survive until the applicable statutes of limitation expire, or until the agreed-upon contract terms expire. The Company also provided guarantees, if the primary obligor fails to perform, to holders of structured settlement annuities provided by a previously owned subsidiary. As of December 31, 2016 , the potential amount of future payments the Company could be required to pay under these guarantees was approximately $1.9 billion , which will be paid over the lifetime of the annuitants. The Company does not believe any payment is likely under these guarantees, as the Company is the beneficiary of a trust that must be maintained at a level that approximates the discounted reserves for these annuities.

Reinsurance

Reinsurance	12 Months Ended
	Dec. 31, 2016
Reinsurance Disclosures [Abstract]
Reinsurance	Note G . Reinsurance The Company cedes insurance to reinsurers to limit its maximum loss, provide greater diversification of risk, minimize exposures on larger risks and to exit certain lines of business. The ceding of insurance does not discharge the primary liability of the Company. A credit exposure exists with respect to reinsurance ceded to the extent that any reinsurer is unable to meet its obligations. A collectibility exposure also exists to the extent that the reinsurer disputes the liabilities assumed under reinsurance agreements. Property and casualty reinsurance coverages are tailored to the specific risk characteristics of each product line and the Company's retained amount varies by type of coverage. Reinsurance contracts are purchased to protect specific lines of business such as property and workers' compensation. Corporate catastrophe reinsurance is also purchased for property and workers' compensation exposure. Currently, most reinsurance contracts are purchased on an excess of loss basis. The Company also utilizes facultative reinsurance in certain lines. In addition, the Company assumes reinsurance, primarily through Hardy and as a member of various reinsurance pools and associations. The following table presents the amounts receivable from reinsurers. December 31 (In millions) 2016 2015 Reinsurance receivables related to insurance reserves: Ceded claim and claim adjustment expenses $ 4,094 $ 4,087 Ceded future policy benefits 212 207 Reinsurance receivables related to paid losses 147 197 Reinsurance receivables 4,453 4,491 Allowance for uncollectible reinsurance (37 ) (38 ) Reinsurance receivables, net of allowance for uncollectible reinsurance $ 4,416 $ 4,453 The Company has established an allowance for uncollectible reinsurance receivables related to credit risk. The Company reviews the allowance quarterly and adjusts the allowance as necessary to reflect changes in estimates of uncollectible balances. The allowance may also be reduced by write-offs of reinsurance receivable balances. The Company attempts to mitigate its credit risk related to reinsurance by entering into reinsurance arrangements with reinsurers that have credit ratings above certain levels and by obtaining collateral. On a limited basis, the Company may enter into reinsurance agreements with reinsurers that are not rated, primarily captive reinsurers. The primary methods of obtaining collateral are through reinsurance trusts, letters of credit and funds withheld balances. Such collateral was approximately $3.0 billion and $3.2 billion as of December 31, 2016 and 2015 . The Company's largest recoverables from a single reinsurer including ceded unearned premium reserves, as of December 31, 2016 , were approximately $2,353 million from a subsidiary of Berkshire Hathaway Group, $350 million from the Gateway Rivers Insurance Company and $212 million from subsidiaries of Wilton Re. These amounts are substantially collateralized. The recoverable from the Berkshire Hathaway Group includes amounts related to third-party reinsurance for which NICO has assumed the credit risk under the terms of the Loss Portfolio Transfer as discussed in Note E to the Consolidated Financial Statements. The effects of reinsurance on earned premiums and written premiums are presented in the following tables. (In millions) Direct Assumed Ceded Net Assumed/ Net % 2016 Earned Premiums Property and casualty $ 10,400 $ 258 $ 4,270 $ 6,388 4.0 % Long term care 486 50 — 536 9.3 % Total earned premiums $ 10,886 $ 308 $ 4,270 $ 6,924 4.4 % 2015 Earned Premiums Property and casualty $ 9,853 $ 274 $ 3,754 $ 6,373 4.3 % Long term care 498 50 — 548 9.1 % Total earned premiums $ 10,351 $ 324 $ 3,754 $ 6,921 4.7 % 2014 Earned Premiums Property and casualty $ 9,452 $ 277 $ 3,073 $ 6,656 4.2 % Long term care 508 48 — 556 8.6 % Total earned premiums $ 9,960 $ 325 $ 3,073 $ 7,212 4.5 % (In millions) Direct Assumed Ceded Net Assumed/ Net % 2016 Written Premiums Property and casualty $ 10,451 $ 245 $ 4,255 $ 6,441 3.8 % Long term care 495 52 — 547 9.5 % Total written premiums $ 10,946 $ 297 $ 4,255 $ 6,988 4.3 % 2015 Written Premiums Property and casualty $ 9,852 $ 270 $ 3,702 $ 6,420 4.2 % Long term care 493 49 — 542 9.0 % Total written premiums $ 10,345 $ 319 $ 3,702 $ 6,962 4.6 % 2014 Written Premiums Property and casualty $ 9,283 $ 276 $ 3,024 $ 6,535 4.2 % Long term care 504 49 — 553 8.9 % Total written premiums $ 9,787 $ 325 $ 3,024 $ 7,088 4.6 % Included in the direct and ceded earned premiums for the years ended December 31, 2016 , 2015 and 2014 are $3,865 million , $3,344 million and $2,643 million related to property business that is 100% reinsured under a significant third-party captive program. The third-party captives that participate in this program are affiliated with the non-insurance company policyholders, therefore this program provides a means for the policyholders to self-insure this property risk. The Company receives and retains a ceding commission. Long term care premiums are from long duration contracts; property and casualty premiums are from short duration contracts. Insurance claims and policyholders' benefits reported on the Consolidated Statements of Operations are net of reinsurance recoveries of $3,016 million , $2,601 million and $1,379 million for the years ended December 31, 2016 , 2015 and 2014 , including $2,621 million , $2,282 million and $1,458 million , respectively, related to the significant third-party captive program discussed above. Reinsurance recoveries in 2014 were unfavorably affected by the commutation of a workers’ compensation reinsurance pool.

Debt

Debt	12 Months Ended
	Dec. 31, 2016
Debt Disclosure [Abstract]
Debt Disclosure [Text Block]	Note H . Debt Debt is composed of the following obligations. December 31 (In millions) 2016 2015 Short term debt: Senior notes of CNAF, 6.500%, face amount of $350, due August 15, 2016 $ — $ 350 Long term debt: Senior notes of CNAF: 6.950%, face amount of $150, due January 15, 2018 150 150 7.350%, face amount of $350, due November 15, 2019 349 349 5.875%, face amount of $500, due August 15, 2020 498 497 5.750%, face amount of $400, due August 15, 2021 398 397 3.950%, face amount of $550, due May 15, 2024 546 546 4.500%, face amount of $500, due March 1, 2026 498 — Debenture of CNAF, 7.250%, face amount of $243, due November 15, 2023 241 241 Subordinated variable rate debt of Hardy, face amount of $30, due September 15, 2036 30 30 Total long term debt 2,710 2,210 Total debt $ 2,710 $ 2,560 CCC is a member of the FHLBC. FHLBC membership provides participants with access to additional sources of liquidity through various programs and services. As a requirement of membership in the FHLBC, CCC held $5 million of FHLBC stock as of December 31, 2016 giving it access to approximately $111 million of additional liquidity. As of December 31, 2016 and 2015 , CCC had no outstanding borrowings from the FHLBC. During 2015, the Company entered into a five-year $250 million senior unsecured revolving credit facility with a syndicate of banks which may be used for general corporate purposes. At the Company's election, the commitments under the credit agreement may be increased from time to time up to an additional aggregate amount of $100 million and the credit agreement includes two optional one-year extensions prior to the first and second anniversary of the closing date, subject to applicable consents. Under the credit agreement, the Company is required to pay a facility fee which would adjust automatically in the event of a change in the Company's financial ratings. The credit agreement includes several covenants, including maintenance of a minimum consolidated net worth and a defined ratio of consolidated indebtedness to consolidated total capitalization. The minimum consolidated net worth, as defined as of December 31, 2016 , was $8.7 billion . As of December 31, 2016 and 2015 , the Company had no outstanding borrowings under the credit agreements. The Company's debt obligations contain customary covenants for investment grade issuers. The Company was in compliance with all covenants as of and for the years ended December 31, 2016 and 2015 . The combined aggregate maturities for debt as of December 31, 2016 are presented in the following table. (In millions) 2017 $ — 2018 150 2019 350 2020 500 2021 400 Thereafter 1,323 Less discount (13 ) Total $ 2,710

Benefit Plans

Benefit Plans	12 Months Ended
	Dec. 31, 2016
Compensation and Retirement Disclosure [Abstract]
Benefit Plans	Note I . Benefit Plans Pension and Postretirement Health Care Benefit Plans CNA sponsors noncontributory defined benefit pension plans, primarily through the CNA Retirement Plan, covering certain eligible employees. These plans were closed to new entrants. CNA's funding policy for defined benefit pension plans is to make contributions in accordance with applicable governmental regulatory requirements with consideration of the funded status of the plans. Effective January 1, 2000, the CNA Retirement Plan was closed to new participants. Existing participants at that time were given a choice to either continue to accrue benefits under the CNA Retirement Plan or to cease accruals effective December 31, 1999. Employees who chose to continue to accrue benefits under the plan received benefits in accordance with plan provisions through June 30, 2015 as discussed further below. Employees who elected to cease accruals effective December 31, 1999 received the present value of their accrued benefit in an accrued pension account that is credited with interest based on the annual rate of interest on 30-year Treasury securities. These employees also receive certain enhanced employer contributions in the CNA 401(k) Plus Plan. In 2016, the CNA Retirement Plan paid $88 million to settle its obligation to certain retirees through the purchase of a group annuity contract from a third party insurance company. This transaction reduced the plan’s projected benefit obligation by $86 million . In the second quarter of 2015, the Company eliminated future benefit accruals associated with the CNA Retirement Plan effective June 30, 2015. Employees who were continuing to accrue under the CNA Retirement Plan up until that date are entitled to an accrued benefit payable based on their eligible compensation and accrued service through June 30, 2015, in accordance with the terms of the CNA Retirement Plan. Starting with the first pay period after July 1, 2015, affected employees began receiving enhanced employer contributions in the CNA 401(k) Plus Plan similar to employees who elected to cease accruals effective December 31, 1999. Employees who elected to cease accruals effective December 31, 1999 are not affected by this curtailment. This curtailment resulted in a $55 million decrease in the CNA Retirement Plan benefit obligation liability and a reduction of the unrecognized actuarial losses included in AOCI. In connection with the curtailment, the Company remeasured the plan benefit obligation which resulted in an increase in the discount rate used to determine the benefit obligation from 3.85% to 4.00% . During 2014, the CNA Retirement Plan offered a limited-time lump sum settlement payment opportunity to the majority of the terminated vested participants of the plan. The lump sum settlements reduced the Company’s risk and volatility related to funding the CNA Retirement Plan. The number of participants that elected to accept the lump sum opportunity was approximately 20% of the then total participants in the plan. Settlement payments of $253 million were made from CNA Retirement Plan assets. The $84 million settlement charge recorded by the Company in the fourth quarter of 2014 represents recognition of a portion of the unrecognized actuarial losses previously reflected in AOCI. This settlement charge is included in Other operating expenses within the Corporate & Other Non-Core segment. CNA provides certain health care benefits to eligible retired employees, their covered dependents and their beneficiaries primarily through the CNA Health and Group Benefits Program. These postretirement benefits have largely been eliminated for active employees. In the second quarter of 2014, the Company eliminated certain postretirement medical benefits associated with the CNA Health and Group Benefits Program. This change was a negative plan amendment which resulted in an $86 million curtailment gain reported in Other operating expenses within the Corporate & Other Non-Core segment. In connection with the plan amendment, the Company remeasured the plan benefit obligation which resulted in a decrease in the discount rate used to determine the benefit obligation from 3.60% to 3.10% . The following table presents a reconciliation of benefit obligations and plan assets. Pension Benefits Postretirement Benefits (In millions) 2016 2015 2016 2015 Benefit obligation as of January 1 $ 2,821 $ 3,019 $ 23 $ 29 Changes in benefit obligation: Service cost — 4 — — Interest cost 113 112 — 1 Participants' contributions — — 4 4 Plan amendments — (55 ) — — Actuarial (gain) loss 68 (79 ) (6 ) (3 ) Benefits paid (173 ) (173 ) (7 ) (8 ) Foreign currency translation and other (14 ) (7 ) 1 — Settlement through group annuity purchase (86 ) — — — Benefit obligation as of December 31 2,729 2,821 15 23 Fair value of plan assets as of January 1 2,267 2,456 — — Change in plan assets: Actual return on plan assets 193 (18 ) — — Company contributions 9 10 3 4 Participants' contributions — — 4 4 Benefits paid (173 ) (173 ) (7 ) (8 ) Foreign currency translation and other (15 ) (8 ) — — Settlement through group annuity purchase (88 ) — — — Fair value of plan assets as of December 31 2,193 2,267 — — Funded status $ (536 ) $ (554 ) $ (15 ) $ (23 ) Amounts recognized on the Consolidated Balance Sheets as of December 31: Other assets $ 4 $ 12 $ — $ — Other liabilities (540 ) (566 ) (15 ) (23 ) Net amount recognized $ (536 ) $ (554 ) $ (15 ) $ (23 ) Amounts recognized in Accumulated other comprehensive income, not yet recognized in net periodic cost (benefit): Prior service credit $ — $ — $ (4 ) $ (6 ) Net actuarial loss 999 999 (3 ) 3 Net amount recognized $ 999 $ 999 $ (7 ) $ (3 ) The accumulated benefit obligation for all defined benefit pension plans was $2,729 million and $2,821 million as of December 31, 2016 and 2015 . The components of net periodic cost (benefit) are presented in the following table. Years ended December 31 (In millions) 2016 2015 2014 Pension cost (benefit) Service cost $ — $ 4 $ 9 Interest cost on projected benefit obligation 113 112 132 Expected return on plan assets (160 ) (174 ) (191 ) Amortization of net actuarial loss 37 34 25 Settlement loss — — 84 Net periodic pension cost (benefit) $ (10 ) $ (24 ) $ 59 Postretirement cost (benefit) Interest cost on projected benefit obligation $ — $ 1 $ 1 Amortization of prior service credit (2 ) (3 ) (10 ) Amortization of net actuarial loss — 1 1 Curtailment gain — — (86 ) Net periodic postretirement cost (benefit) $ (2 ) $ (1 ) $ (94 ) The amounts recognized in Other comprehensive income are presented in the following table. Years ended December 31 (In millions) 2016 2015 2014 Pension and postretirement benefits Amounts arising during the period $ (29 ) $ (111 ) $ (337 ) Curtailment and other — 56 (81 ) Settlement — — 84 Reclassification adjustment relating to prior service credit (2 ) (3 ) (10 ) Reclassification adjustment relating to actuarial loss 37 35 26 Settlement through group annuity purchase (2 ) — — Total increase (decrease) in Other comprehensive income $ 4 $ (23 ) $ (318 ) The table below presents the estimated amounts to be recognized from AOCI into net periodic cost (benefit) during 2017 . (In millions) Pension Benefits Postretirement Benefits Amortization of prior service credit $ — $ (2 ) Amortization of net actuarial loss 36 — Total estimated amounts to be recognized $ 36 $ (2 ) Actuarial assumptions used for the CNA Retirement Plan and CNA Health and Group Benefits Program to determine benefit obligations are presented in the following table. December 31 2016 2015 Pension benefits Discount rate 3.950 % 4.150 % Expected long term rate of return 7.500 7.500 Postretirement benefits Discount rate 2.750 % 2.750 % Actuarial assumptions used for the CNA Retirement Plan and CNA Health and Group Benefits Program to determine net cost or benefit are presented in the following table. Years ended December 31 2016 2015 2014 Pension benefits Discount rate 4.150 % 3.850%/4.000% 4.650 % Expected long term rate of return 7.500 7.500 7.500 Rate of compensation increases N/A 3.920 3.990 Postretirement benefits Discount rate 2.750 % 2.500 % 3.600%/3.100% In determining the expected long term rate of return on plan assets assumption for the CNA Retirement Plan, CNA considered the historical performance of the benefit plan investment portfolio as well as long term market return expectations based on the investment mix of the portfolio and the expected investment horizon. The CNA Health and Group Benefits Program has limited its share of the health care trend rate to a cost-of-living adjustment of 4% per year. For all participants, the employer subsidy on health care costs will not increase by more than 4% per year. As a result, the assumed health care cost trend rate used in measuring the accumulated postretirement benefit obligation for the CNA Health and Group Benefits Program was 4% per year in 2016 , 2015 and 2014 . CNA employs a total return approach whereby a mix of equity, limited partnerships and fixed maturity securities are used to maximize the long term return of retirement plan assets for a prudent level of risk and to manage cash flows according to plan requirements. The target allocation of plan assets is 40% to 60% invested in equity securities and limited partnerships, with the remainder primarily invested in fixed maturity securities. Alternative investments, including limited partnerships, are used to enhance risk adjusted long term returns while improving portfolio diversification. The intent of this strategy is to minimize the Company's expense related to funding the plan by generating investment returns that exceed the growth of the plan liabilities over the long run. Risk tolerance is established after careful consideration of the plan liabilities, plan funded status and corporate financial conditions. As of December 31, 2016 , the plan had committed approximately $113 million to future capital calls from various third-party limited partnership investments in exchange for an ownership interest in the related partnerships. Derivatives may be used to gain market exposure in an efficient and timely manner. Investment risk is measured and monitored on an ongoing basis through annual liability measurements, periodic asset/liability studies and quarterly investment portfolio reviews. Pension plan assets measured at fair value on a recurring basis as well as cash are presented in the following tables. December 31, 2016 (In millions) Level 1 Level 2 Level 3 Total Assets Fixed maturity securities: Corporate and other bonds $ — $ 500 $ 10 $ 510 States, municipalities and political subdivisions — 63 — 63 Asset-backed: Residential mortgage-backed — 109 — 109 Commercial mortgage-backed — 66 — 66 Other asset-backed — 4 — 4 Total asset-backed — 179 — 179 Total fixed maturity securities — 742 10 752 Equity securities 363 105 — 468 Derivative financial instruments — — — — Short term investments 11 35 — 46 Other assets — 37 — 37 Cash 14 — — 14 Total assets measured at fair value $ 388 $ 919 $ 10 1,317 Total limited partnerships measured at net asset value (1) 876 Total plan assets $ 2,193 December 31, 2015 (In millions) Level 1 Level 2 Level 3 Total Assets Assets Fixed maturity securities: Corporate and other bonds $ — $ 455 $ 10 $ 465 States, municipalities and political subdivisions — 106 — 106 Asset-backed: Residential mortgage-backed — 133 — 133 Commercial mortgage-backed — 69 — 69 Other asset-backed — 11 — 11 Total asset-backed — 213 — 213 Total fixed maturity securities — 774 10 784 Equity securities 336 107 — 443 Derivative financial instruments 1 — — 1 Short term investments 24 28 — 52 Other assets — 52 — 52 Total assets measured at fair value $ 361 $ 961 $ 10 1,332 Total limited partnerships measured at net asset value (1) 935 Total plan assets $ 2,267 (1) In accordance with Subtopic 820-10, certain investments that are measured at fair value using the net asset value per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the statement of financial position. The limited partnership investments held within the plan are recorded at fair value, which represents the plan's share of net asset value of each partnership, as determined by the general partner. Limited partnerships comprising 86% and 87% of the carrying value as of December 31, 2016 and 2015 employ hedge fund strategies that generate returns through investing in marketable securities in the public fixed income and equity markets and the remainder were primarily invested in private debt and equity. Within hedge fund strategies, approximately 57% were equity related, 38% pursued a multi-strategy approach and 5% were focused on distressed investments as of December 31, 2016 . For a discussion of the fair value levels and the valuation methodologies used to measure fixed maturity securities, equities, derivatives and short term investments, see Note C to the Consolidated Financial Statements. The tables below present a reconciliation for all pension plan assets measured at fair value on a recurring basis using significant unobservable inputs (Level 3). Level 3 (In millions) Balance as of January 1, 2016 Actual return on assets still held as of December 31, 2016 Actual return on assets sold during the year ended December 31, 2016 Purchases, sales and settlements Net transfers into (out of) Level 3 Balance as of December 31, 2016 Fixed maturity securities: Corporate and other bonds $ 10 $ — $ — $ — $ — $ 10 Total $ 10 $ — $ — $ — $ — $ 10 Level 3 (In millions) Balance as of January 1, 2015 Actual return on assets still held as of Actual return on assets sold during the year ended December 31, 2015 Purchases, sales and settlements Net transfers into (out of) Level 3 Balance as of December 31, 2015 Fixed maturity securities: Corporate and other bonds $ 15 $ — $ — $ — $ (5 ) $ 10 Total $ 15 $ — $ — $ — $ (5 ) $ 10 The table below presents the estimated future minimum benefit payments to participants as of December 31, 2016 . (In millions) Pension Benefits Postretirement Benefits 2017 $ 178 $ 3 2018 178 2 2019 177 2 2020 178 2 2021 178 2 2022-2026 883 3 In 2017 , CNA expects to contribute $12 million to its pension plans and $3 million to its postretirement health care benefit plans. Savings Plans CNA sponsors savings plans, which are generally contributory plans that allow most employees to contribute a maximum of 50% of their eligible compensation, subject to certain limitations prescribed by the IRS. The Company contributes matching amounts to participants, amounting to 70% of the first 6% ( 35% of the first 6% in the first year of employment) of eligible compensation contributed by the employee. Matching contributions vest ratably over participants first five years of service. Eligible employees also receive a Company contribution of 3% or 5% of their eligible compensation, depending on their age. In addition, these employees are eligible to receive additional discretionary contributions of up to 2% of eligible compensation and an additional Company match of up to 80% of the first 6% of eligible compensation contributed by the employee. These additional contributions are made at the discretion of management and are contributed to participant accounts in the first quarter of the year following management's determination of the discretionary amounts. Matching contributions vest ratably over participants first five years of service. Benefit expense for the Company's savings plans was $75 million , $71 million and $69 million for the years ended December 31, 2016 , 2015 and 2014 .

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation [Text Block]	Note J . Stock-Based Compensation The CNAF Incentive Compensation Plan (the Plan), as amended and restated on January 1, 2010, as amended, authorizes the grant of stock-based compensation to certain management personnel for up to 11 million shares of CNAF's common stock. The Plan currently provides for awards of stock options, stock appreciation rights (SARs), restricted shares, restricted stock units (RSUs), performance-based RSUs and performance share units. The number of shares available for the granting of stock-based compensation under the Plan as of December 31, 2016 was approximately 3.7 million . The Company recorded stock-based compensation expense related to the Plan of $36 million , $14 million and $11 million for the years ended December 31, 2016 , 2015 and 2014 . The related income tax benefit recognized was $12 million , $5 million and $4 million for the years ended December 31, 2016 , 2015 , and 2014 . The compensation cost related to non-vested awards not yet recognized was $32 million , and the weighted average period over which it is expected to be recognized is 1.9 years as of December 31, 2016 . Equity based compensation that is not fully vested prior to termination is generally forfeited upon termination, except in cases of retirement, death or disability, and as otherwise provided by contractual obligations. Share Awards The fair value of share awards is based on the market value of the Company's common stock as of the date of grant. Share awards currently granted under the Plan include RSUs, performance-based RSUs and performance share units. Generally, RSU's vest over a two or three year service period following the date of grant. Performance-based RSUs generally become payable within a range of 0% to 100% of the number of shares initially granted based upon the attainment of specific annual performance goals and vest ratably over a four -year service period following the date of grant. In 2016, CNA adopted the Annual Performance Share Plan (PSP). The PSP provides officers with an opportunity to earn an award based upon attainment of specific performance goals achieved over a one -year performance period. Awards are granted at the beginning of each performance year and are subject to a two -year cliff vesting period after the Company’s annual performance has been determined. Prior to the PSP, CNA issued performance share units under the Long Term Incentive Plan (LTI). The LTI Plan has a three year performance period and will continue to have outstanding awards through 2017. In both plans, the performance share units become payable within a range of 0% to 200% of the number of performance share units initially granted. In 2016, CNA granted Special Supplemental Equity Awards (SSE). The awards consist of restricted stock units subject to both Company performance in 2016 and service-based vesting up to two years. Payments made under the PSP and SSE are made entirely in shares of common stock, except for awards made to non-U.S. participants, which are paid in cash. The following table presents activity for non-vested RSUs, performance-based RSUs and performance share units under the Plan in 2016 . Number of Awards Weighted-Average Grant Date Fair Value Balance as of January 1, 2016 735,263 $ 36.53 Awards granted 2,545,624 32.27 Awards vested (371,443 ) 33.33 Awards forfeited, canceled or expired (186,932 ) 32.80 Performance-based adjustment (590,730 ) 33.10 Balance as of December 31, 2016 2,131,782 $ 33.28 SARs The exercise price of all SARs granted is based on the market value of the Company's common stock as of the date of grant. SARs generally vest ratably over a four -year service period following date of grant and have a maximum term of ten years. The fair value of granted SARs was estimated at the grant date using the Black-Scholes option-pricing model. The Black-Scholes model incorporates a risk free rate of return and various assumptions regarding the underlying common stock and the expected life of the securities granted. Different interest rates and assumptions were used for each grant, as appropriate based on date of grant. There were no SARs granted for the years ended December 31, 2016 and 2015 . As of December 31, 2016 , there were approximately 1 million awards outstanding, fully vested or expected to vest and be exercisable. The grant date fair value of SARs vested was $1 million for the year ended December 31, 2014 .

Other Intangible Assets

Other Intangible Assets	12 Months Ended
	Dec. 31, 2016
Intangible Assets, Gross (Excluding Goodwill) [Abstract]
Other Intangible Assets	Note K . Other Intangible Assets Other intangible assets are presented in the following table. December 31 2016 2015 (In millions) Economic Useful Life Gross Carrying Amount Accumulated Amortization Gross Carrying Amount Accumulated Amortization Finite-lived intangible assets: Value of business acquired 1 - 4 years $ 48 $ 48 $ 57 $ 57 Trade name 8 years 6 3 7 3 Distribution channel 15 years 10 3 12 3 Total finite-lived intangible assets 64 54 76 63 Indefinite-lived intangible assets: Syndicate capacity 43 52 Agency force 16 16 Total indefinite-lived intangible assets 59 68 Total other intangible assets $ 123 $ 54 $ 144 $ 63 The Company's other intangible assets primarily relate to the purchase of Hardy, and the amortization of these intangible assets is included in the Statement of Operations for the International segment. For the year ended December 31, 2014 amortization expense of $2 million was included in Amortization of deferred acquisition costs. For the years ended December 31, 2016 , 2015 and 2014 amortization expense of $1 million was included in Other operating expenses. The gross carrying amounts and accumulated amortization in the table above may change from period to period as a result of foreign currency translation. Estimated future amortization expense for other intangible assets is $1 million annually in 2017 through 2021.

Operating Leases _Text Block_

Operating Leases [Text Block]	12 Months Ended
	Dec. 31, 2016
Leases, Operating [Abstract]
Operating Leases [Text Block]	Note L . Operating Leases The Company occupies office facilities under lease agreements that expire at various dates. In addition, data processing, office and transportation equipment is leased under agreements that expire at various dates. Most leases contain renewal options that provide for rent increases based on prevailing market conditions. Lease expenses for the years ended December 31, 2016 , 2015 and 2014 were $60 million , $46 million and $55 million . Sublease revenue for the year ended December 31, 2014 was $1 million . The table below presents the expected future minimum lease payments to be made under non-cancelable operating leases as of December 31, 2016 . (In millions) Future Minimum Lease Payments 2017 $ 48 2018 37 2019 30 2020 33 2021 34 Thereafter 244 Total $ 426 In connection with the planned relocation of the Company's global headquarters, on March 24, 2016, the Company sold the building in which it maintains the current principal executive offices of CNAF. Concurrently, the Company agreed to lease back the current office space until the relocation of the global headquarters under a separate lease agreement, which is expected to occur in 2018. The sale-leaseback agreement includes expected future minimum lease payments of $10 million in 2017 and $4 million in 2018.

Stockholders' Equity and Statut

Stockholders' Equity and Statutory Accounting Practices	12 Months Ended
	Dec. 31, 2016
Stockholders' Equity and Statutory Accounting Practices [Abstract]
Stockholders' Equity And Statutory Accounting Practices	Note M . Stockholders’ Equity and Statutory Accounting Practices Common Stock Dividends There are no restrictions on the retained earnings or net income of CNAF with regard to payment of dividends to its stockholders. However, given the holding company nature of CNAF, its ability to pay a dividend is significantly dependent on the receipt of dividends from its subsidiaries, particularly CCC, which directly or indirectly owns all significant subsidiaries. See the Statutory Accounting Practices section below for a discussion of the regulatory restrictions on CCC's availability to pay dividends. CNAF's ability to pay dividends is indirectly limited by the minimum consolidated net worth covenant in the Company's line of credit agreement. See Note H to the Consolidated Financial Statements for further discussion of the Company's debt obligations. Statutory Accounting Practices CNAF’s insurance subsidiaries are domiciled in various jurisdictions. These subsidiaries prepare statutory financial statements in accordance with accounting practices prescribed or permitted by the respective jurisdictions’ insurance regulators. Domestic prescribed statutory accounting practices are set forth in a variety of publications of the National Association of Insurance Commissioners (NAIC) as well as state laws, regulations and general administrative rules. These statutory accounting principles vary in certain respects from GAAP. In converting from statutory accounting principles to GAAP, the more significant adjustments include deferral of policy acquisition costs and the inclusion of net unrealized holding gains or losses in stockholders’ equity relating to certain fixed maturity securities. The Company has a prescribed practice as it relates to the accounting under Statement of Statutory Accounting Principles No. 62R (SSAP No. 62R), Property and Casualty Reinsurance , paragraphs 67 and 68 in conjunction with the 2010 Loss Portfolio Transfer with NICO which is further discussed in Note E. The prescribed practice allows the Company to aggregate all third party AE&P reinsurance balances administered by NICO in Schedule F and to utilize the Loss Portfolio Transfer as collateral for the underlying third party reinsurance balances for purposes of calculating the statutory reinsurance penalty. This prescribed practice increased statutory capital and surplus by $67 million and $90 million at December 31, 2016 and 2015 . The 2015 long term care premium deficiency discussed in Note A was recorded on a GAAP basis. There was no premium deficiency for statutory accounting purposes. Statutory accounting principles requires the use of prescribed discount rates in calculating the reserves for long term care future policy benefits which are lower than the discount rates used on a GAAP basis and results in higher carried reserves relative to GAAP reserves. The payment of dividends by CNAF's insurance subsidiaries without prior approval of the insurance department of each subsidiary’s domiciliary jurisdiction is generally limited by formula. Dividends in excess of these amounts are subject to prior approval by the respective insurance regulator. Dividends from CCC are subject to the insurance holding company laws of the State of Illinois, the domiciliary state of CCC. Under these laws, ordinary dividends, or dividends that do not require prior approval by the Illinois Department of Insurance (the Department), are determined based on the greater of the prior year's statutory net income or 10% of statutory surplus as of the end of the prior year, as well as timing and amount of dividends paid in the preceding twelve months. Additionally, ordinary dividends may only be paid from earned surplus, which is calculated by removing unrealized gains from unassigned surplus. As of December 31, 2016 , CCC is in a positive earned surplus position. The maximum allowable dividend CCC could pay during 2017 that would not be subject to the Department’s prior approval is $1,075 million , less dividends paid during the preceding twelve months measured at that point in time. CCC paid dividends of $765 million in 2016 . The actual level of dividends paid in any year is determined after an assessment of available dividend capacity, holding company liquidity and cash needs as well as the impact the dividends will have on the statutory surplus of the applicable insurance company. Combined statutory capital and surplus and statutory net income (loss), determined in accordance with accounting practices prescribed or permitted by insurance and/or other regulatory authorities for the Combined Continental Casualty Companies, are presented in the table below. Statutory Capital and Surplus Statutory Net Income (Loss) December 31 Years ended December 31 (In millions) 2016 (1) 2015 2016 (1) 2015 2014 Combined Continental Casualty Companies $ 10,748 $ 10,723 $ 1,033 $ 1,148 $ 914 (1) Information derived from the statutory-basis financial statements to be filed with insurance regulators. CNAF’s domestic insurance subsidiaries are subject to risk-based capital (RBC) requirements. RBC is a method developed by the NAIC to determine the minimum amount of statutory capital appropriate for an insurance company to support its overall business operations in consideration of its size and risk profile. The formula for determining the amount of RBC specifies various factors, weighted based on the perceived degree of risk, which are applied to certain financial balances and financial activity. The adequacy of a company's actual capital is evaluated by a comparison to the RBC results, as determined by the formula. Companies below minimum RBC requirements are classified within certain levels, each of which requires specified corrective action. The statutory capital and surplus presented above for CCC was approximately 270% and 266% of company action level RBC as of December 31, 2016 and 2015 . Company action level RBC is the level of RBC which triggers a heightened level of regulatory supervision. The statutory capital and surplus of the Company's foreign insurance subsidiaries, which is not significant to the overall statutory capital and surplus, also met or exceeded their respective regulatory and other capital requirements.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss) by Component	12 Months Ended
	Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss) by Component	Note N . Accumulated Other Comprehensive Income (Loss) by Component The table below displays the changes in Accumulated other comprehensive income (loss) by component. (In millions) Net unrealized gains (losses) on investments with OTTI losses Net unrealized gains (losses) on other investments Pension and postretirement benefits Cumulative foreign currency translation adjustment Total Balance as of December 31, 2015 $ 27 $ 390 $ (648 ) $ (84 ) $ (315 ) Other comprehensive income (loss) before reclassifications 9 290 (22 ) (114 ) 163 Amounts reclassified from accumulated other comprehensive income (loss) net of tax (expense) benefit of $(3), $(16), $12, $- and $(7) 6 38 (23 ) — 21 Other comprehensive income (loss) net of tax (expense) benefit of $(1), $(117), $(3), $- and $(121) 3 252 1 (114 ) 142 Balance as of December 31, 2016 $ 30 $ 642 $ (647 ) $ (198 ) $ (173 ) (In millions) Net unrealized gains (losses) on investments with OTTI losses Net unrealized gains (losses) on other investments Pension and postretirement benefits Cumulative foreign currency translation adjustment Total Balance as of December 31, 2014 $ 36 $ 942 $ (633 ) $ 55 $ 400 Other comprehensive income (loss) before reclassifications (23 ) (595 ) (36 ) (139 ) (793 ) Amounts reclassified from accumulated other comprehensive income (loss) net of tax (expense) benefit of $8, $30, $11, $- and $49 (14 ) (43 ) (21 ) — (78 ) Other comprehensive income (loss) net of tax (expense) benefit of $5, $282, $8, $- and $295 (9 ) (552 ) (15 ) (139 ) (715 ) Balance as of December 31, 2015 $ 27 $ 390 $ (648 ) $ (84 ) $ (315 ) Amounts reclassified from Accumulated other comprehensive income (loss) shown above are reported in Net income (loss) as follows: Component of AOCI Consolidated Statements of Operations Line Item Affected by Reclassifications Net unrealized gains (losses) on investments with OTTI losses Net realized investment gains (losses) Net unrealized gains (losses) on other investments Net realized investment gains (losses) Pension and postretirement benefits Other operating expenses

Business Segments

Business Segments	12 Months Ended
	Dec. 31, 2016
Segment Reporting [Abstract]
Business Segments	Note O . Business Segments The Company's core property and casualty commercial insurance operations are managed and reported in three business segments: Specialty, Commercial and International. Specialty provides a broad array of professional, financial and specialty property and casualty products and services through a network of independent agents, brokers and managing general underwriters. Commercial includes property and casualty coverages sold to small businesses and middle market entities and organizations primarily through an independent agency distribution system. Commercial also includes commercial insurance and risk management products sold to large corporations primarily through insurance brokers. International provides management and professional liability coverages as well as a broad range of other property and casualty insurance products and services abroad through a network of brokers, independent agencies and managing general underwriters, as well as the Lloyd’s of London marketplace. The Company's non-core operations are managed and reported in two segments: Life & Group Non-Core and Corporate & Other Non-Core. Life & Group Non-Core primarily includes the results of our individual and group long term care businesses that are in run-off. Corporate & Other Non-Core primarily includes certain corporate expenses, including interest on corporate debt, and the results of certain property and casualty business in run-off, including CNA Re and A&EP. The accounting policies of the segments are the same as those described in Note A to the Consolidated Financial Statements. The Company manages most of its assets on a legal entity basis, while segment operations are generally conducted across legal entities. As such, only Insurance and Reinsurance receivables, Insurance reserves, Deferred acquisition costs and Goodwill are readily identifiable for all individual segments. Distinct investment portfolios are not maintained for every individual segment; accordingly, allocation of assets to each segment is not performed. Therefore, a significant portion of Net investment income and Realized investment gains or losses are allocated primarily based on each segment's net carried insurance reserves, as adjusted. All significant intersegment income and expense has been eliminated. Income taxes have been allocated on the basis of the taxable income of the segments. Approximately 7.9% , 8.0% and 8.8% of the Company's direct written premiums were derived from outside the United States for the years ended December 31, 2016 , 2015 and 2014 . In the following tables, certain financial measures are presented to provide information used by management to monitor the Company's operating performance. Management utilizes these financial measures to monitor the Company's insurance operations and investment portfolio. Net operating income (loss), which is derived from certain income statement amounts, is used by management to monitor performance of the Company's insurance operations. The Company's investment portfolio is monitored by management through analysis of various factors including unrealized gains and losses on securities, portfolio duration and exposure to market and credit risk. Based on such analyses, the Company may recognize an OTTI loss on an investment security in accordance with its policy, or sell a security, which may produce realized gains and losses. Net operating income (loss) is calculated by excluding from net income (loss) the after-tax effects of i) net realized investment gains (losses) ii) income or loss from discontinued operations and iii) any cumulative effects of changes in accounting guidance. The calculation of net operating income excludes net realized investment gains (losses) because net realized investment gains (losses) are largely discretionary, except for some losses related to OTTI, and are generally driven by economic factors that are not necessarily consistent with key drivers of underwriting performance, and are therefore not considered an indication of trends in insurance operations. The Company's results of continuing operations and selected balance sheet items by segment are presented in the following tables. Year ended December 31, 2016 Specialty Commercial International Life & Group Non-Core Corporate & Other Non-Core (In millions) Eliminations Total Net written premiums $ 2,780 $ 2,841 $ 821 $ 547 $ — $ (1 ) $ 6,988 Operating revenues Net earned premiums $ 2,779 $ 2,804 $ 806 $ 536 $ — $ (1 ) $ 6,924 Net investment income 516 638 51 767 16 — 1,988 Other revenues 362 32 — (2 ) 12 — 404 Total operating revenues 3,657 3,474 857 1,301 28 (1 ) 9,316 Claims, Benefits and Expenses Net incurred claims and benefits 1,467 1,927 492 1,286 98 — 5,270 Policyholders’ dividends 4 9 — — — — 13 Amortization of deferred acquisition costs 591 470 174 — — — 1,235 Other insurance related expenses 301 560 133 132 (3 ) (1 ) 1,122 Other expenses 312 36 24 8 209 — 589 Total claims, benefits and expenses 2,675 3,002 823 1,426 304 (1 ) 8,229 Operating income (loss) before income tax 982 472 34 (125 ) (276 ) — 1,087 Income tax (expense) benefit on operating income (loss) (332 ) (161 ) (13 ) 145 98 — (263 ) Net operating income (loss) 650 311 21 20 (178 ) — 824 Net realized investment gains (losses) 5 4 18 25 (2 ) — 50 Income tax (expense) benefit on net realized investment gains (losses) (2 ) (2 ) (3 ) (9 ) 1 — (15 ) Net realized investment gains (losses), after tax 3 2 15 16 (1 ) — 35 Net income (loss) from continuing operations $ 653 $ 313 $ 36 $ 36 $ (179 ) $ — $ 859 December 31, 2016 (In millions) Reinsurance receivables $ 760 $ 621 $ 131 $ 462 $ 2,479 $ — $ 4,453 Insurance receivables 982 1,021 233 17 2 — 2,255 Deferred acquisition costs 310 214 76 — — — 600 Goodwill 117 — 28 — — — 145 Insurance reserves Claim and claim adjustment expenses 6,149 8,894 1,328 3,358 2,614 — 22,343 Unearned premiums 1,911 1,323 396 132 — — 3,762 Future policy benefits — — — 10,326 — — 10,326 Year ended December 31, 2015 Specialty Commercial International Life & Group Non-Core Corporate & Other Non-Core (In millions) Eliminations Total Net written premiums $ 2,781 $ 2,818 $ 822 $ 542 $ 1 $ (2 ) $ 6,962 Operating revenues Net earned premiums $ 2,782 $ 2,788 $ 804 $ 548 $ 1 $ (2 ) $ 6,921 Net investment income 474 593 52 704 17 — 1,840 Other revenues 356 37 (1 ) 7 11 (3 ) 407 Total operating revenues 3,612 3,418 855 1,259 29 (5 ) 9,168 Claims, Benefits and Expenses Net incurred claims and benefits 1,597 1,814 479 1,421 61 — 5,372 Policyholders’ dividends 4 8 — — — — 12 Amortization of deferred acquisition costs 589 469 168 314 — — 1,540 Other insurance related expenses 278 538 138 142 (1 ) (2 ) 1,093 Other expenses 301 28 12 11 186 (3 ) 535 Total claims, benefits and expenses 2,769 2,857 797 1,888 246 (5 ) 8,552 Operating income (loss) before income tax 843 561 58 (629 ) (217 ) — 616 Income tax (expense) benefit on operating income (loss) (283 ) (192 ) (21 ) 315 80 — (101 ) Net operating income (loss) 560 369 37 (314 ) (137 ) — 515 Net realized investment gains (losses) (33 ) (47 ) 1 (1 ) 13 — (67 ) Income tax (expense) benefit on net realized investment gains (losses) 11 16 — 9 (5 ) — 31 Net realized investment gains (losses), after tax (22 ) (31 ) 1 8 8 — (36 ) Net income (loss) from continuing operations $ 538 $ 338 $ 38 $ (306 ) $ (129 ) $ — $ 479 December 31, 2015 (In millions) Reinsurance receivables $ 724 $ 639 $ 144 $ 497 $ 2,487 $ — $ 4,491 Insurance receivables 890 993 233 11 2 — 2,129 Deferred acquisition costs 307 213 78 — — — 598 Goodwill 117 — 33 — — — 150 Insurance reserves Claim and claim adjustment expenses 6,269 9,183 1,347 3,220 2,644 — 22,663 Unearned premiums 1,839 1,297 415 120 — — 3,671 Future policy benefits — — — 10,152 — — 10,152 Year ended December 31, 2014 Specialty Commercial Life & Group Non-Core Corporate & Other Non-Core (In millions) International Eliminations Total Net written premiums $ 2,839 $ 2,817 $ 880 $ 553 $ 1 $ (2 ) $ 7,088 Operating revenues Net earned premiums $ 2,838 $ 2,906 $ 913 $ 556 $ 1 $ (2 ) $ 7,212 Net investment income 560 723 61 700 23 — 2,067 Other revenues 295 38 — 16 12 (5 ) 356 Total operating revenues 3,693 3,667 974 1,272 36 (7 ) 9,635 Claims, Benefits and Expenses Net incurred claims and benefits 1,627 2,187 488 1,304 (29 ) — 5,577 Policyholders’ dividends 6 8 — — — — 14 Amortization of deferred acquisition costs 592 493 204 28 — — 1,317 Other insurance related expenses 262 487 151 130 1 (2 ) 1,029 Other expenses 254 31 28 30 210 (5 ) 548 Total claims, benefits and expenses 2,741 3,206 871 1,492 182 (7 ) 8,485 Operating income (loss) before income tax 952 461 103 (220 ) (146 ) — 1,150 Income tax (expense) benefit on operating income (loss) (318 ) (154 ) (34 ) 151 54 — (301 ) Net operating income (loss) 634 307 69 (69 ) (92 ) — 849 Net realized investment gains (losses) 15 16 (1 ) 7 20 — 57 Income tax (expense) benefit on net realized investment gains (losses) (5 ) (6 ) 1 — (8 ) — (18 ) Net realized investment gains (losses), after tax 10 10 — 7 12 — 39 Net income (loss) from continuing operations $ 644 $ 317 $ 69 $ (62 ) $ (80 ) $ — $ 888 The following table presents revenue by line of business for each reportable segment. Revenues are comprised of operating revenues and net realized investment gains and losses. Years ended December 31 (In millions) 2016 2015 2014 Specialty Management & Professional Liability $ 2,620 $ 2,617 $ 2,818 Surety 532 502 509 Warranty & Alternative Risks 510 460 381 Specialty revenues 3,662 3,579 3,708 Commercial Middle Market 1,769 1,623 1,631 Small Business 583 616 709 Other Commercial Insurance 1,126 1,132 1,343 Commercial revenues 3,478 3,371 3,683 International Canada 203 214 273 CNA Europe 319 309 335 Hardy 353 333 365 International revenues 875 856 973 Life & Group Non-Core revenues 1,326 1,258 1,279 Corporate & Other Non-Core revenues 26 42 56 Eliminations (1 ) (5 ) (7 ) Total revenues $ 9,366 $ 9,101 $ 9,692

Discontinued Operations

Discontinued Operations	12 Months Ended
	Dec. 31, 2016
Discontinued Operations and Disposal Groups [Abstract]
Discontinued Operations	Note P . Discontinued Operations The results of discontinued operations reflected in the Consolidated Statements of Operations were as follows: Year ended December 31 (In millions) 2014 Revenues Net earned premiums $ — Net investment income 94 Net realized investment gains 3 Other revenues — Total revenues 97 Claims, Benefits and Expenses Insurance claims and policyholders' benefits 75 Other operating expenses 2 Total claims, benefits and expenses 77 Income before income tax 20 Income tax expense (6 ) Income from operations of discontinued operations, net of income tax 14 Loss on sale, net of income tax benefit of $40 (211 ) Loss from discontinued operations $ (197 ) The disposal group included $3,550 million of assets and $3,297 million of liabilities as of August 1, 2014 .

Quarterly Financial Data (Unaud

Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2016
Quarterly Financial Data [Abstract]
Quarterly Financial Data (Unaudited)	Note Q . Quarterly Financial Data (Unaudited) The following tables present unaudited quarterly financial data. 2016 (In millions, except per share data) First Second Third Fourth Full Year Revenues $ 2,195 $ 2,348 $ 2,433 $ 2,390 $ 9,366 Net income (loss) (1) $ 66 $ 209 $ 343 $ 241 $ 859 Basic earnings (loss) per share $ 0.25 $ 0.77 $ 1.27 $ 0.89 $ 3.18 Diluted earnings (loss) per share $ 0.24 $ 0.77 $ 1.26 $ 0.89 $ 3.17 2015 (In millions, except per share data) First Second Third Fourth Full Year Revenues $ 2,352 $ 2,327 $ 2,153 $ 2,269 $ 9,101 Net income (loss) (1) (2) $ 233 $ 138 $ 178 $ (70 ) $ 479 Basic earnings (loss) per share $ 0.86 $ 0.51 $ 0.66 $ (0.26 ) $ 1.77 Diluted earnings (loss) per share $ 0.86 $ 0.51 $ 0.66 $ (0.26 ) $ 1.77 (1) Net income (loss) in the first quarter of 2016 and the second quarter of 2015 included a charge related to the application of retroactive reinsurance accounting to adverse reserve development ceded under the 2010 A&EP Loss Portfolio Transfer in our Corporate & Other Non-Core segment. (2) Net income (loss) in the fourth quarter of 2015 included a charge related to recognition of a premium deficiency in our long term care business.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2016
Related Party Transactions [Abstract]
Related Party Transactions	Note R . Related Party Transactions The Company reimburses Loews for, or pays directly, fees and expenses of investment facilities and services provided to the Company. The amounts incurred by the Company for these fees and expenses were $43 million , $39 million and $39 million for the years ended December 31, 2016 , 2015 and 2014 and amounts due to Loews, included in Other liabilities and payable in the first quarter of the subsequent year, were $23 million and $21 million as of December 31, 2016 and 2015 . In addition, the Company reimbursed Loews for general corporate services and related travel expenses of $1 million for the year ended December 31, 2016 . The CNA Tax Group is included in the consolidated federal income tax return of Loews and its eligible subsidiaries, and the related payable to Loews, included in Other liabilities, was $28 million and $61 million as of December 31, 2016 and 2015 . For a detailed description of the income tax agreement with Loews see Note D to the Consolidated Financial Statements. In addition, the Company writes, at standard rates, a limited amount of insurance for Loews and its subsidiaries. The earned premiums for the years ended December 31, 2016 , 2015 and 2014 were $2 million . CNA previously sponsored a stock ownership plan whereby the Company financed the purchase of Company common stock by certain former officers, including executive officers. Interest charged on the principal amount of these outstanding stock purchase loans is generally equivalent to the short term applicable federal rate in effect on the disbursement date of the loan, compounded semi-annually. Loans made pursuant to the plan were full recourse and secured by the stock purchased.

Organization Review

Organization Review	12 Months Ended
	Dec. 31, 2016
Restructuring and Related Activities [Abstract]
Restructuring and Related Activities Disclosure [Text Block]	Note S . Organization Review In 2016 , the Company completed a comprehensive organization review intended to improve effectiveness and efficiency. The review resulted in the elimination of approximately 370 positions. The Company incurred employee termination costs as a result of these actions totaling approximately $19 million during the year ended December 31, 2016 . The costs incurred to date are included in Total claims, benefits, and expenses on the consolidated Statements of Operations and have been allocated to the Company's reportable segments in a manner consistent with the Company's current allocation of personnel costs. The costs by reportable segment for the year ended December 31, 2016 , are presented in the following table. Year ended December 31 (In millions) 2016 Specialty $ 4 Commercial 14 International — Life & Group Non-Core 1 Corporate & Other Non-Core — Total organization review costs $ 19

Schedule I. Summary of Investme

Schedule I. Summary of Investments - Other Than Investments in Related Parties	12 Months Ended
	Dec. 31, 2016
Summary of Investments, Other than Investments in Related Parties [Abstract]
Schedule I. Summary of Investments - Other than Investments in Related Parties	SCHEDULE I. SUMMARY OF INVESTMENTS - OTHER THAN INVESTMENTS IN RELATED PARTIES Incorporated herein by reference to Note B to the Consolidated Financial Statements included under Item 8.

Schedule II. Condensed Financia

Schedule II. Condensed Financial Information of Registrant (Parent Company)	12 Months Ended
	Dec. 31, 2016
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Schedule II. Condensed Financial Information of Registrant (Parent Company)	SCHEDULE II. CONDENSED FINANCIAL INFORMATION OF REGISTRANT (PARENT COMPANY) CNA Financial Corporation Statements of Operations and Comprehensive Income (Loss) Years ended December 31 (In millions) 2016 2015 2014 Revenues Net investment income $ 3 $ 1 $ 1 Net realized investment (losses) gains (7 ) 5 4 Total revenues (4 ) 6 5 Expenses Administrative and general 1 1 5 Interest 155 154 182 Total expenses 156 155 187 Loss from operations before income taxes and equity in net income of subsidiaries (160 ) (149 ) (182 ) Income tax benefit 41 34 35 Loss before equity in net income of subsidiaries (119 ) (115 ) (147 ) Equity in net income of subsidiaries 978 594 838 Net income 859 479 691 Equity in other comprehensive income of subsidiaries 142 (715 ) (42 ) Total Comprehensive Income (Loss) $ 1,001 $ (236 ) $ 649 See accompanying Notes to Condensed Financial Information as well as the Consolidated Financial Statements and accompanying Notes. CNA Financial Corporation Balance Sheets December 31 (In millions, except share data) 2016 2015 Assets Investment in subsidiaries $ 14,202 $ 13,851 Cash 1 4 Short term investments 487 478 Amounts due from affiliates 6 — Other assets 1 1 Total assets $ 14,697 $ 14,334 Liabilities Short term debt $ — $ 350 Long term debt 2,680 2,180 Other liabilities 48 48 Total liabilities 2,728 2,578 Stockholders' Equity Common stock ($2.50 par value; 500,000,000 shares authorized; 273,040,243 shares issued; 270,495,998 and 270,274,361 shares outstanding) 683 683 Additional paid-in capital 2,173 2,153 Retained earnings 9,359 9,313 Accumulated other comprehensive income (173 ) (315 ) Treasury stock (2,544,245 and 2,765,882 shares), at cost (73 ) (78 ) Total stockholders' equity 11,969 11,756 Total liabilities and stockholders' equity $ 14,697 $ 14,334 See accompanying Notes to Condensed Financial Information as well as the Consolidated Financial Statements and accompanying Notes. CNA Financial Corporation Statements of Cash Flows Years ended December 31 (In millions) 2016 2015 2014 Cash Flows from Operating Activities Net income $ 859 $ 479 $ 691 Adjustments to reconcile net income to net cash flows provided by operating activities: Equity in net income of subsidiaries (978 ) (594 ) (838 ) Dividends received from subsidiaries 765 900 650 Net realized investment losses (gains) 7 (5 ) (4 ) Other, net 21 4 14 Total adjustments (185 ) 305 (178 ) Net cash flows provided by operating activities 674 784 513 Cash Flows from Investing Activities Change in short term investments (9 ) 21 6 Capital contributions to subsidiaries — — (10 ) Other, net 4 7 5 Net cash flows (used) provided by investing activities (5 ) 28 1 Cash Flows from Financing Activities Dividends paid to common stockholders (813 ) (811 ) (541 ) Proceeds from the issuance of debt 498 — 546 Repayment of debt (358 ) — (549 ) Stock options exercised — 1 5 Other, net 1 1 25 Net cash flows used by financing activities (672 ) (809 ) (514 ) Net change in cash (3 ) 3 — Cash, beginning of year 4 1 1 Cash, end of year $ 1 $ 4 $ 1 See accompanying Notes to Condensed Financial Information as well as the Consolidated Financial Statements and accompanying Notes. Notes to Condensed Financial Information A. Summary of Significant Accounting Policies Basis of Presentation The condensed financial information of CNA Financial Corporation (CNAF or the Parent Company) should be read in conjunction with the Consolidated Financial Statements and Notes thereto included in Item 8 of this Form 10-K. CNAF’s subsidiaries are accounted for using the equity method of accounting. Equity in net income of these subsidiaries is presented on the Condensed Statements of Operations as Equity in net income of subsidiaries. Loews owned approximately 90% of the outstanding common stock of CNAF as of December 31, 2016 . Recently Adopted Accounting Standards Updates (ASU) In April 2015, the Financial Accounting Standards Board (FASB) issued ASU No. 2015-03, Interest-Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issuance Costs . The updated accounting guidance requires debt issuance costs to be presented as a deduction from the corresponding debt liability instead of the historical presentation as an unamortized debt issuance asset. As of January 1, 2016, the Parent Company adopted the updated accounting guidance retrospectively. The Parent Company adjusted its previously reported financial information included herein to reflect the change in accounting guidance for debt issuance costs. The impacts of adopting the new accounting standard on the Parent Company’s Consolidated Balance Sheet as of December 31, 2015, were a decrease in Other assets and a decrease in Long term debt of $2 million . B. Commitments, Contingencies and Guarantees As of December 31, 2016 and 2015 CNAF had recorded liabilities of approximately $5 million related to guarantee agreements. The Parent Company believes that it is not likely that any future indemnity claims will be significantly greater than the amounts recorded. In the course of selling business entities and assets to third parties, CNAF has agreed to guarantee the performance of certain obligations of both a previously owned subsidiary and a current subsidiary. Such obligations include agreement to indemnify purchasers for losses arising out of breaches of representation and warranties with respect to the business entities or assets sold, including, in certain cases, losses arising from undisclosed liabilities or certain named litigation. The guarantee agreements may include provisions that survive indefinitely. As of December 31, 2016 , the aggregate amount of quantifiable guarantee agreements in effect for sales of business entities, assets and third-party loans was $625 million . Should the company be required to make payments under the guarantee, it would have the right to seek reimbursement in certain cases from an affiliate of a previously owned subsidiary. In addition, CNAF has agreed to provide indemnification to third-party purchasers for certain losses associated with sold business entities or assets that are not limited by a contractual monetary amount. As of December 31, 2016 , CNAF had outstanding unlimited indemnifications in connection with the sales of certain of its business entities or assets that included tax liabilities arising prior to a purchaser’s ownership of an entity or asset, defects in title at the time of sale, employee claims arising prior to closing and in some cases losses arising from certain litigation and undisclosed liabilities. These indemnification agreements survive until the applicable statutes of limitation expire or until the agreed upon contract terms expire. CNAF also provided guarantees, if the primary obligor fails to perform, to holders of structured settlement annuities provided by a previously owned subsidiary. As of December 31, 2016 , the potential amount of future payments CNAF could be required to pay under these guarantees was approximately $1.9 billion , which will be paid over the lifetime of the annuitants. The Parent Company does not believe a payable is likely under these guarantees, as it is the beneficiary of a trust that must be maintained at a level that approximates the discounted reserves for these annuities.

Schedule III. Supplementary Ins

Schedule III. Supplementary Insurance Information	12 Months Ended
	Dec. 31, 2016
Supplementary Insurance Information [Abstract]
Schedule III. Supplementary Insurance Information	SCHEDULE III. SUPPLEMENTARY INSURANCE INFORMATION Incorporated herein by reference to Note O to the Consolidated Financial Statements included under Item 8.

Schedule IV. Reinsurance

Schedule IV. Reinsurance	12 Months Ended
	Dec. 31, 2016
Supplemental Schedule of Reinsurance Premiums for Insurance Companies [Abstract]
Schedule IV. Reinsurance	SCHEDULE IV. REINSURANCE Incorporated herein by reference to Note G to the Consolidated Financial Statements included under Item 8.

Schedule V. Valuation and Quali

Schedule V. Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2016
Valuation and Qualifying Accounts [Abstract]
Schedule V. Valuation and Qualifying Accounts	SCHEDULE V. VALUATION AND QUALIFYING ACCOUNTS (In millions) Balance at Beginning of Period Charged to Costs and Expenses Charged to Other Accounts (1) Deductions Balance at End of Period Year ended December 31, 2016 Deducted from assets: Allowance for doubtful accounts: Insurance and reinsurance receivables $ 89 $ (2 ) $ (1 ) $ (3 ) $ 83 Year ended December 31, 2015 Deducted from assets: Allowance for doubtful accounts: Insurance and reinsurance receivables $ 109 $ (12 ) $ — $ (8 ) $ 89 Year ended December 31, 2014 Deducted from assets: Allowance for doubtful accounts: Insurance and reinsurance receivables $ 155 $ (40 ) $ (1 ) $ (5 ) $ 109 (1) Amount includes effects of foreign currency translation.

Schedule VI. Supplemental Infor

Schedule VI. Supplemental Information Concerning Property and Casualty Insurance Operations	12 Months Ended
	Dec. 31, 2016
Supplemental Information for Property, Casualty Insurance Underwriters [Abstract]
Schedule VI. Supplemental Information Concerning Property and Casualty Insurance Operations	SCHEDULE VI. SUPPLEMENTAL INFORMATION CONCERNING PROPERTY AND CASUALTY INSURANCE OPERATIONS As of and for the years ended December 31 Consolidated Property and Casualty Operations (In millions) 2016 2015 2014 Balance Sheet Data Deferred acquisition costs $ 599 $ 597 Reserves for unpaid claim and claim adjustment expenses 22,343 22,663 Discount deducted from claim and claim adjustment expense reserves above (based on interest rates ranging from 3.5% to 8.0%) 1,572 1,534 Unearned premiums 3,762 3,671 Statement of Operations Data Net written premiums $ 6,988 $ 6,962 $ 7,088 Net earned premiums 6,924 6,921 7,212 Net investment income 1,952 1,807 2,031 Incurred claim and claim adjustment expenses related to current year 5,025 4,934 5,043 Incurred claim and claim adjustment expenses related to prior years (342 ) (255 ) (39 ) Amortization of deferred acquisition costs 1,235 1,540 1,317 Paid claim and claim adjustment expenses 5,134 4,945 5,297

Summary of Significant Accoun34

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
Consolidation	The accompanying Consolidated Financial Statements have been prepared in conformity with accounting principles generally accepted in the United States of America (GAAP). Intercompany amounts have been eliminated.
Use of Estimates	The preparation of Consolidated Financial Statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the Consolidated Financial Statements and the reported amounts of revenues and expenses during the reporting period. Actual results may differ from those estimates.
Premiums	Premiums: Insurance premiums on property and casualty insurance contracts are recognized in proportion to the underlying risk insured and are principally earned ratably over the duration of the policies. Premiums on long term care contracts are earned ratably over the policy year in which they are due. The reserve for unearned premiums represents the portion of premiums written relating to the unexpired terms of coverage. Insurance receivables include balances due currently or in the future, including amounts due from insureds related to losses under high deductible policies, and are presented at unpaid balances, net of an allowance for uncollectible receivables. Amounts are considered past due based on policy payment terms. The allowance is determined based on periodic evaluations of aged receivables, management's experience and current economic conditions. Insurance receivables and any related allowance are written off after collection efforts are exhausted or a negotiated settlement is reached. Property and casualty contracts that are retrospectively rated contain provisions that result in an adjustment to the initial policy premium depending on the contract provisions and loss experience of the insured during the experience period. For such contracts, the Company estimates the amount of ultimate premiums that the Company may earn upon completion of the experience period and recognizes either an asset or a liability for the difference between the initial policy premium and the estimated ultimate premium. The Company adjusts such estimated ultimate premium amounts during the course of the experience period based on actual results to date. The resulting adjustment is recorded as either a reduction of or an increase to the earned premiums for the period.
Claim and claim adjustment expense reserves	Claim and claim adjustment expense reserves: Claim and claim adjustment expense reserves, except reserves for structured settlements not associated with asbestos and environmental pollution (A&EP), workers' compensation lifetime claims and long term care claims, are not discounted and are based on 1) case basis estimates for losses reported on direct business, adjusted in the aggregate for ultimate loss expectations; 2) estimates of incurred but not reported (IBNR) losses; 3) estimates of losses on assumed reinsurance; 4) estimates of future expenses to be incurred in the settlement of claims; 5) estimates of salvage and subrogation recoveries and 6) estimates of amounts due from insureds related to losses under high deductible policies. Management considers current conditions and trends as well as past Company and industry experience in establishing these estimates. The effects of inflation, which can be significant, are implicitly considered in the reserving process and are part of the recorded reserve balance. Ceded claim and claim adjustment expense reserves are reported as a component of Reinsurance receivables on the Consolidated Balance Sheets. Claim and claim adjustment expense reserves are presented net of anticipated amounts due from insureds related to losses under deductible policies of $1.2 billion and $1.2 billion as of December 31, 2016 and 2015 . A significant portion of these amounts are supported by collateral. The Company has an allowance for uncollectible deductible amounts, which is presented as a component of the allowance for doubtful accounts included in Insurance receivables on the Consolidated Balance Sheets. Structured settlements have been negotiated for certain property and casualty insurance claims. Structured settlements are agreements to provide fixed periodic payments to claimants. The Company's obligations for structured settlements not funded by annuities are included in claim and claim adjustment expense reserves and carried at present values determined using interest rates ranging from to 5.5% to 8.0% as of December 31, 2016 and 2015 . As of December 31, 2016 and 2015 , the discounted reserves for unfunded structured settlements were $544 million and $560 million , net of discount of $841 million and $880 million . For the years ended December 31, 2016 , 2015 and 2014 , the amount of interest recognized on the discounted reserves of unfunded structured settlements was $42 million , $42 million and $43 million , respectively. This interest accretion is presented as a component of Insurance claims and policyholders’ benefits on the Consolidated Statements of Operations, but is excluded from the Company’s disclosure of prior year development. Workers' compensation lifetime claim reserves are calculated using mortality assumptions determined through statutory regulation and economic factors. At December 31, 2016 and 2015 , workers' compensation lifetime claim reserves are discounted at a 3.5% interest rate. As of December 31, 2016 and 2015 , the discounted reserves for workers’ compensation lifetime claim reserves were $371 million and $396 million , net of discount of $202 million and $218 million . For the years ended December 31, 2016 , 2015 and 2014 the amount of interest accretion recognized on the discounted reserves of workers’ compensation lifetime claim reserves was $17 million , $20 million and $22 million , respectively. Long term care claim reserves are calculated using mortality and morbidity assumptions based on Company and industry experience. Long term care claim reserves are discounted at interest rates ranging from 4.5% to 6.8% as of December 31, 2016 and 2015 . As of December 31, 2016 and 2015 , such discounted reserves totaled $2.2 billion and $2.2 billion , net of discount of $529 million and $435 million .
Future policy benefits reserves	Future policy benefits reserves: Future policy benefits reserves represent the active life reserves related to the Company's long term care policies and are computed using the net level premium method, which incorporates actuarial assumptions as to morbidity, persistency, discount rate and expenses. Expense assumptions primarily relate to claim adjudication. Actuarial assumptions generally vary by plan, age at issue, policy duration and gender. The initial assumptions are determined at issuance, include a margin for adverse deviation and are locked in throughout the life of the contract unless a premium deficiency develops. If a premium deficiency emerges, the assumptions are unlocked and deferred acquisition costs, if any, and the future policy benefits reserves are adjusted. The December 31, 2015 gross premium valuation (GPV) indicated a premium deficiency of $296 million . The indicated premium deficiency necessitated a charge to income that was affected by the write off of the entire long term care deferred acquisition cost asset of $289 million and an increase to active life reserves of $7 million . As a result, the long term care active life reserves carried as of December 31, 2015 represent management’s best estimate assumptions at that date with no margin for adverse deviation. The December 31, 2016 GPV indicated the carried reserves were sufficient, therefore there was no unlocking of assumptions. Interest rates for long term care active life reserves range from 6.6% to 7.0% as of December 31, 2016 and 2015 .
Guaranty fund and other insurance-related assessments	Guaranty fund and other insurance-related assessments: Liabilities for guaranty fund and other insurance-related assessments are accrued when an assessment is probable, when it can be reasonably estimated and when the event obligating the entity to pay an imposed or probable assessment has occurred. Liabilities for guaranty funds and other insurance-related assessments are not discounted and are included as part of Other liabilities on the Consolidated Balance Sheets. As of December 31, 2016 and 2015 , the liability balances were $125 million and $129 million .
Reinsurance	Reinsurance: Reinsurance accounting allows for contractual cash flows to be reflected as premiums and losses. To qualify for reinsurance accounting, reinsurance agreements must include risk transfer. To meet risk transfer requirements, a reinsurance contract must include both insurance risk, consisting of underwriting and timing risk, and a reasonable possibility of a significant loss for the assuming entity. Reinsurance receivables related to paid losses are presented at unpaid balances. Reinsurance receivables related to unpaid losses are estimated in a manner consistent with claim and claim adjustment expense reserves or future policy benefits reserves. Reinsurance receivables are reported net of an allowance for uncollectible amounts on the Consolidated Balance Sheets. The cost of reinsurance is primarily accounted for over the life of the underlying reinsured policies using assumptions consistent with those used to account for the underlying policies or over the reinsurance contract period. The ceding of insurance does not discharge the primary liability of the Company. The Company has established an allowance for uncollectible reinsurance receivables which relates to both amounts already billed on ceded paid losses as well as ceded reserves that will be billed when losses are paid in the future. The allowance for uncollectible reinsurance receivables is estimated on the basis of periodic evaluations of balances due from reinsurers, reinsurer solvency, management's experience and current economic conditions. Reinsurer financial strength ratings are updated and reviewed on an annual basis or sooner if the Company becomes aware of significant changes related to a reinsurer. Because billed receivables generally approximate 3% or less of total reinsurance receivables, the age of the reinsurance receivables related to paid losses is not a significant input into the allowance analysis. Changes in the allowance for uncollectible reinsurance receivables are presented as a component of Insurance claims and policyholders' benefits on the Consolidated Statements of Operations. Amounts are considered past due based on the reinsurance contract terms. Reinsurance receivables related to paid losses and any related allowance are written off after collection efforts have been exhausted or a negotiated settlement is reached with the reinsurer. Reinsurance receivables related to paid losses from insolvent insurers are written off when the settlement due from the estate can be reasonably estimated. At the time reinsurance receivables related to paid losses are written off, any required adjustment to reinsurance receivables related to unpaid losses is recorded as a component of Insurance claims and policyholders' benefits on the Consolidated Statements of Operations. Reinsurance contracts that do not effectively transfer the economic risk of loss on the underlying policies are recorded using the deposit method of accounting, which requires that premium paid or received by the ceding company or assuming company be accounted for as a deposit asset or liability. The Company had $3 million recorded as deposit assets as of December 31, 2016 and 2015 , and $6 million and $8 million recorded as deposit liabilities as of December 31, 2016 and 2015 . Income on reinsurance contracts accounted for under the deposit method is recognized using an effective yield based on the anticipated timing of payments and the remaining life of the contract. When the anticipated timing of payments changes, the effective yield is recalculated to reflect actual payments to date and the estimated timing of future payments. The deposit asset or liability is adjusted to the amount that would have existed had the new effective yield been applied since the inception of the contract. A loss portfolio transfer is a retroactive reinsurance contract. If the cumulative claim and allocated claim adjustment expenses ceded under a loss portfolio transfer exceed the consideration paid, the resulting gain from such excess is deferred and amortized into earnings in future periods in proportion to actual recoveries under the loss portfolio transfer. In any period in which there is a gain position and a revised estimate of claim and allocated claim adjustment expenses, a portion of the deferred gain is cumulatively recognized in earnings as if the revised estimate was available at the inception date of the loss portfolio transfer.
Deferred acquisition costs	Deferred acquisition costs: Deferrable acquisition costs include commissions, premium taxes and certain underwriting and policy issuance costs which are incremental direct costs of successful contract acquisitions. Acquisition costs related to property and casualty business are deferred and amortized ratably over the period the related premiums are earned. Deferred acquisition costs are presented net of ceding commissions and other ceded acquisition costs. The Company evaluates deferred acquisition costs for recoverability. Anticipated investment income is considered in the determination of the recoverability of deferred acquisition costs. Adjustments, if necessary, are recorded in current period results of operations. Deferred acquisition costs related to long term care contracts issued prior to January 1, 2004 include costs which vary with and are primarily related to the acquisition of business. As noted under Future policy benefits reserves, all of the long term care deferred acquisition costs of $289 million were written off as of December 31, 2015 in recognition of a premium deficiency.
Investments in life settlement contracts and related revenue recognition	Investments in life settlement contracts and related revenue recognition: Prior to 2002, the Company purchased investments in life settlement contracts. The Company obtained the ownership and beneficiary rights of an underlying life insurance policy through a life settlement contract with the owner of the life insurance contract. The Company accounts for its investments in life settlement contracts using the fair value method. Under the fair value method, each life settlement contract is carried at its fair value at the end of each reporting period. The change in fair value estimated through the Company's internal valuation process, life insurance proceeds received and periodic maintenance costs, such as premiums, necessary to keep the underlying policy in force, are recorded in Other revenues on the Consolidated Statements of Operations. In December 2016, the Company reached agreement on terms to sell the entire portfolio of life settlement contracts to a third party. The Company expects to consummate this transaction in 2017. As a result, the portfolio, which is included within Life & Group Non-Core segment, was determined to be held for sale as of December 31, 2016 . Therefore, the contracts were measured at the lower of the carrying amount or the fair value per the agreed terms. This resulted in a $10 million loss recognized within Net realized investment gains. The fair value of the Company's investments in life settlement contracts were $58 million and $74 million as of December 31, 2016 and 2015 , and are included in Other assets on the Consolidated Balance Sheets. The cash receipts and payments related to life settlement contracts are included in Cash flows from operating activities on the Consolidated Statements of Cash Flows. The following table details the values for life settlement contracts. The determination of fair value is discussed in Note C to the Consolidated Financial Statements. December 31, 2016 Number of Life Settlement Contracts Fair Value of Life Settlement Contracts (In millions) Face Amount of Life Insurance Policies (In millions) Estimated settlements during: 2017 63 $ 10 $ 34 2018 55 8 30 2019 49 7 26 2020 43 6 23 2021 36 4 19 Thereafter 280 23 153 Total 526 $ 58 $ 285 The Company uses an actuarial model to estimate the aggregate face amount of life insurance that are expected to settle in each future year and the corresponding fair value. This model projects the likelihood of the insured's death for each inforce policy based upon the Company's estimated mortality rates, which may vary due to the relatively small size of the portfolio of life settlement contracts. The number of life settlement contracts presented in the table above is based upon the average face amount of inforce policies estimated to settle in each future year. The increase in fair value recognized in Other revenues for the years ended December 31, 2016 , 2015 and 2014 on contracts still held at each respective period-end was $7 million , $1 million and $8 million . The gains recognized during the years ended December 31, 2016 , 2015 and 2014 on contracts that settled were $8 million , $24 million and $25 million .
Investments	Investments The Company classifies its fixed maturity securities and its equity securities as either available-for-sale or trading, and as such, they are carried at fair value. Changes in fair value of trading securities are reported within Net investment income on the Consolidated Statements of Operations. Changes in fair value related to available-for-sale securities are reported as a component of Other comprehensive income. Losses may be recognized within Net realized investment gains (losses) on the Consolidated Statements of Operations when a decline in value is determined by the Company to be other-than-temporary. The cost of fixed maturity securities classified as available-for-sale is adjusted for amortization of premiums and accretion of discounts, which are included in Net investment income on the Consolidated Statements of Operations. The amortization of premium and accretion of discount for fixed maturity securities takes into consideration call and maturity dates that produce the lowest yield. In 2015 the Company changed its accounting principle as previously the amortization of premiums was to maturity. This change in estimate effected by a change in accounting principle was adopted in the fourth quarter of 2015 and decreased Net investment income and the amortized cost of fixed maturity securities by $39 million in the Consolidated Statement of Operations for the year-ended December 31, 2015 and the Consolidated Balance Sheet as of December 31, 2015 . The $39 million decrease to Net investment income included a $22 million cumulative adjustment relating to prior periods. The total adjustment decreased Basic and Diluted earnings per share by $0.09 for the year ended December 31, 2015 . To the extent that unrealized gains on fixed income securities supporting long term care products and structured settlements not funded by annuities would result in a premium deficiency if those gains were realized, a related increase in Insurance reserves is recorded, net of tax, as a reduction of net unrealized gains through Other comprehensive income (Shadow Adjustments). Shadow Adjustments, net of tax, decreased $97 million and $177 million for the years ended December 31, 2016 and 2015 . As of December 31, 2016 and 2015 , net unrealized gains on investments included in Accumulated other comprehensive income (AOCI) were correspondingly reduced by Shadow Adjustments of $1,014 million and $1,111 million . For asset-backed securities included in fixed maturity securities, the Company recognizes income using an effective yield based on anticipated prepayments and the estimated economic life of the securities. When estimates of prepayments change, the effective yield is recalculated to reflect actual payments to date and anticipated future payments. The amortized cost of high credit quality fixed rate securities is adjusted to the amount that would have existed had the new effective yield been applied since the acquisition of the securities. Such adjustments are reflected in Net investment income on the Consolidated Statements of Operations. Interest income on lower rated and variable rate securities is determined using the prospective yield method. The Company's carrying value of investments in limited partnerships is its share of the net asset value of each partnership, as determined by the general partner. Certain partnerships for which results are not available on a timely basis are reported on a lag, primarily three months or less. Changes in net asset values are accounted for under the equity method and recorded within Net investment income on the Consolidated Statements of Operations. Mortgage loans are commercial in nature, are carried at unpaid principal balance, net of unamortized fees and any valuation allowance, and are recorded once funded. Mortgage loans are considered to be impaired loans when it is probable that contractual principal and interest payments will not be collected. A valuation allowance is established for impaired loans to the extent that the present value of expected future cash flows discounted at the loan's original effective interest rate is less than the carrying value of the loan. Interest income from mortgage loans is recognized on an accrual basis using the effective yield method. Accrual of income is generally suspended for mortgage loans that are impaired and collection of principal and interest payments is unlikely. Mortgage loans are considered past due when full principal or interest payments have not been received according to contractual terms. Other invested assets include overseas deposits and Federal Home Loan Bank of Chicago (FHLBC) stock. FHLBC stock is carried at fair value. Overseas deposits are valued using the net asset value per share (or equivalent) practical expedient. They are primarily short-term government securities, agency securities and corporate bonds held in trusts that are managed by Lloyd's of London. These funds are required of Lloyd's syndicates to protect policyholders in overseas markets and may be denominated in local currency. Short term investments are carried at fair value, with the exception of cash accounts earning interest, which are carried at cost and approximate fair value. Changes in fair value are reported as a component of Other comprehensive income. Purchases and sales of all securities are recorded on the trade date, except for private placement debt securities, including bank loan participations, which are recorded once funded. Realized investment gains and losses are determined on the basis of the cost or amortized cost of the specific securities sold.
Variable Interest Entities	In the normal course of investing activities, the Company enters into relationships with variable interest entities (VIEs), as both an investor in limited partnerships and asset-backed securities issued by third-party VIEs. The Company is not the primary beneficiary of these VIEs, and therefore does not consolidate them. The Company determines whether it is the primary beneficiary of a VIE based on a qualitative assessment of the relative power and benefits of the Company and our venture partners. 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.
Impairments, Other Than Temporary	A security is impaired if the fair value of the security is less than its cost adjusted for accretion, amortization and previously recorded other-than-temporary impairment (OTTI) losses, otherwise defined as an unrealized loss. When a security is impaired, the impairment is evaluated to determine whether it is temporary or other-than-temporary. Significant judgment is required in the determination of whether an OTTI loss has occurred for a security. The Company follows a consistent and systematic process for determining and recording an OTTI loss. The Company has established a committee responsible for the OTTI process referred to as the Impairment Committee. The Impairment Committee is responsible for evaluating all securities in an unrealized loss position on at least a quarterly basis. The Impairment Committee’s assessment of whether an OTTI loss has occurred incorporates both quantitative and qualitative information. Fixed maturity securities that the Company intends to sell, or it more likely than not will be required to sell before recovery of amortized cost, are considered to be other-than-temporarily impaired and the entire difference between the amortized cost basis and fair value of the security is recognized as an OTTI loss in earnings. The remaining fixed maturity securities in an unrealized loss position are evaluated to determine if a credit loss exists. The factors considered by the Impairment Committee include (a) the financial condition and near-term and long-term prospects of the issuer, (b) whether the debtor is current on interest and principal payments, (c) credit ratings of the securities and (d) general market conditions and industry or sector specific outlook. The Company also considers results and analysis of cash flow modeling for asset-backed securities, and when appropriate, other fixed maturity securities. The focus of the analysis for asset-backed securities is on assessing the sufficiency and quality of underlying collateral and timing of cash flows based on scenario tests. If the present value of the modeled expected cash flows equals or exceeds the amortized cost of a security, no credit loss is judged to exist and the asset-backed security is deemed to be temporarily impaired. If the present value of the expected cash flows is significantly less than amortized cost, the security is judged to be other-than-temporarily impaired for credit reasons and that shortfall, referred to as the credit component, is recognized as an OTTI loss in earnings. The difference between the adjusted amortized cost basis and fair value, referred to as the non-credit component, is recognized as OTTI in Other comprehensive income. In subsequent reporting periods, a change in intent to sell or further credit impairment on a security whose fair value has not deteriorated will cause the non-credit component originally recorded as OTTI in Other comprehensive income to be recognized as an OTTI loss in earnings. The Company performs the discounted cash flow analysis using stressed scenarios to determine future expectations regarding recoverability. Significant assumptions enter into these cash flow projections including delinquency rates, probable risk of default, loss severity upon a default, over collateralization and interest coverage triggers and credit support from lower level tranches. The Company applies the same impairment model as described above for the majority of its non-redeemable preferred stock securities on the basis that these securities possess characteristics similar to debt securities and that the issuers maintain their ability to pay dividends. For all other equity securities, in determining whether the security is other-than-temporarily impaired, the Impairment Committee considers a number of factors including, but not limited to: (a) the length of time and the extent to which the fair value has been less than amortized cost, (b) the financial condition and near term prospects of the issuer, (c) the intent and ability of the Company to retain its investment for a period of time sufficient to allow for an anticipated recovery in value and (d) general market conditions and industry or sector specific outlook.
Income Taxes	Income Taxes The Company and its eligible subsidiaries (CNA Tax Group) are included in the consolidated federal income tax return of Loews and its eligible subsidiaries. The Company accounts for income taxes under the asset and liability method. Under the asset and liability method, deferred income taxes are recognized for temporary differences between the financial statement and tax return bases of assets and liabilities, based on enacted tax rates and other provisions of the tax law. The effect of a change in tax laws or rates on deferred tax assets and liabilities is recognized in income in the period in which such change is enacted. Future tax benefits are recognized to the extent that realization of such benefits is more likely than not, and a valuation allowance is established for any portion of a deferred tax asset that management believes will not be realized.
Pension and Postretirement Benefits	Pension and Postretirement Benefits The Company recognizes the overfunded or underfunded status of its defined benefit plans in Other assets or Other liabilities on the Consolidated Balance Sheets. Changes in funded status related to prior service costs and credits and actuarial gains and losses are recognized in the year in which the changes occur through Other comprehensive income. Annual service cost, interest cost, expected return on plan assets, amortization of prior service costs and credits and amortization of actuarial gains and losses are recognized in the Consolidated Statements of Operations. The vested benefit obligation for the CNA Retirement Plan is determined based on eligible compensation and accrued service for previously entitled employees. Effective June 30, 2015, future benefit accruals under the CNA Retirement Plan were eliminated and the benefit obligations were frozen.
Stock-Based Compensation	Stock-Based Compensation The Company records compensation expense using the fair value method for all awards it grants, modifies or cancels primarily on a straight-line basis over the requisite service period, generally three to four years.
Foreign Currency	Foreign Currency Foreign currency translation gains and losses are reflected in Stockholders' equity as a component of AOCI. The Company's foreign subsidiaries' balance sheet accounts are translated at the exchange rates in effect at each reporting date and income statement accounts are either translated at the exchange rate on the date of the transaction or at the average exchange rates. Foreign currency transaction gains (losses) of $(9) million , $(11) million and $(25) million were included in determining Net income (loss) for the years ended December 31, 2016 , 2015 and 2014 .
Property and Equipment	Property and Equipment Property and equipment are carried at cost less accumulated depreciation. Depreciation is based on the estimated useful lives of the various classes of property and equipment and is determined principally on the straight-line method. Furniture and fixtures are depreciated over seven years. Office equipment is depreciated over five years. The estimated lives for data processing equipment and software generally range from three to five years, but can be as long as ten years. Leasehold improvements are depreciated over the corresponding lease terms not to exceed the underlying asset life. The Company's previously owned building and related capital improvements were depreciated over periods not to exceed fifty years.
Goodwill	Goodwill Goodwill represents the excess of purchase price over the fair value of the net assets of acquired entities and businesses. Goodwill in the International segment may change from period to period as a result of foreign currency translation. Goodwill is tested for impairment annually or when certain triggering events require such tests. As a result of reviews completed for the year ended December 31, 2016 , the Company determined that the estimated fair value of the reporting units were in excess of their carrying value including Goodwill. Changes in future periods in assumptions about the level of economic capital, business growth, earnings projections or the weighted average cost of capital could result in a goodwill impairment.
Other Intangible Assets	Other Intangible Assets Other intangible assets are reported within Other assets. Finite-lived intangible assets are amortized over their estimated useful lives. Indefinite-lived other intangible assets are tested for impairment annually or when certain triggering events require such tests.
Earnings (Loss) Per Share Data	Earnings (Loss) Per Share Data Earnings (loss) per share is based on weighted average number of outstanding common shares. Basic earnings (loss) per share excludes the impact of dilutive securities and is computed by dividing Net income (loss) by the weighted average number of common shares outstanding for the period. Diluted earnings (loss) per share reflects the potential dilution that could occur if securities or other contracts to issue common stock were exercised or converted into common stock. For the years ended December 31, 2016 , 2015 and 2014 , approximately 678 thousand , 534 thousand and 675 thousand potential shares attributable to exercises or conversions into common stock under stock-based employee compensation plans were included in the calculation of diluted earnings per share. For those same periods, approximately 102 thousand , 106 thousand and 170 thousand potential shares attributable to exercises or conversions into common stock under stock-based employee compensation plans were not included in the calculation of diluted earnings per share because the effect would have been antidilutive.
New Accounting Pronouncements and Changes in Accounting Principles [Text Block]	Recently Adopted Accounting Standards Updates (ASU) In April 2015, the Financial Accounting Standards Board (FASB) issued ASU No. 2015-03, Interest-Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issuance Costs . The updated accounting guidance requires debt issuance costs to be presented as a deduction from the corresponding debt liability instead of the historical presentation as an unamortized debt issuance asset. As of January 1, 2016, the Company adopted the updated accounting guidance retrospectively. The Company adjusted its previously reported financial information included herein to reflect the change in accounting guidance for debt issuance costs. The impacts of adopting the new accounting standard on the Company’s Consolidated Balance Sheet as of December 31, 2015, were a decrease in Other assets and a decrease in Long term debt of $2 million . In May 2015, the FASB issued ASU No. 2015-09, Financial Services-Insurance (Topic 944): Disclosures about Short-Duration Contracts. The updated accounting guidance requires enhanced disclosures to provide additional information about insurance liabilities for short-duration contracts. The updated guidance is effective for annual financial statements issued for fiscal years beginning after December 15, 2015, and interim periods within the annual periods beginning after December 15, 2016. The Company has adopted the change in disclosure requirements for short-duration contracts. In May 2015, the FASB issued ASU No. 2015-07, Fair Value Measurement (Topic 820): Disclosures for Investments in Certain Entities That Calculate Net Asset Value per Share (or Its Equivalent). The updated accounting guidance removes the requirement to categorize assets measured at fair value utilizing the net asset value per share (or equivalent) practical expedient within the fair value hierarchy. As of January 1, 2016, the Company adopted the updated accounting guidance retrospectively. The Company adjusted its previously reported financial information included herein to reflect the change in accounting guidance for assets measured using the net asset value. The impact of adopting the new accounting standard resulted in excluding overseas deposits of $31 million and $27 million and limited partnership investments held within the pension plan of $876 million and $935 million from the fair value level disclosures as of December 31, 2016 and December 31, 2015 .
Recently Issued Accounting Standard Update	Accounting Standards Pending Adoption In May 2014, the FASB issued ASU No. 2014-09, Revenue Recognition (Topic 606): Revenue from Contracts with Customers . The standard excludes from its scope the accounting for insurance contracts, financial instruments, and certain other agreements that are governed under other GAAP guidance. The updated guidance requires an entity to recognize revenue as performance obligations are met, in an amount that reflects the consideration the entity is entitled to receive for the transfer of the promised goods or services. The standard is effective for interim and annual reporting periods beginning after December 15, 2017 and may be applied retrospectively or through a cumulative effect adjustment to retained earnings at the date of adoption. The Company has not made a decision on the method of adoption and is currently evaluating the effect the updated guidance will have on the Company’s financial statements. While the Company anticipates some changes to revenue recognition for certain of our warranty products and services, we do not currently believe ASU 2014-09 will have a material effect on our Consolidated Financial Statements. In January 2016, the FASB issued ASU No. 2016-01, Financial Instruments-Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities. The updated accounting guidance requires changes to the reporting model for financial instruments. The guidance is effective for interim and annual periods beginning after December 15, 2017. The Company is currently evaluating the effect the guidance will have on the Company's financial statements, and expects the primary change for the Company to be the requirement for equity investments (except those accounted for under the equity method of accounting or those that result in consolidation of the investee) to be measured at fair value with changes in fair value recognized in net income. In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842): Accounting for Leases. The updated accounting guidance requires lessees to recognize on the balance sheet the assets and liabilities for the rights and obligations created by all leases, including those historically accounted for as operating leases. The guidance is effective for interim and annual periods beginning after December 15, 2018. The Company is currently evaluating the effect the updated guidance will have on the Company's financial statements. It is expected that assets and liabilities will increase based on the present value of remaining lease payments for leases in place at the adoption date; however, this is not expected to be material to the Company's results of operations or financial position. In March 2016, the FASB issued ASU No. 2016-09, Compensation-Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting. The updated accounting guidance simplifies the accounting for share-based payment award transactions, including income tax consequences, classification of awards as either equity or liabilities and classification on the statement of cash flows. The guidance is effective for annual and interim periods beginning after December 15, 2016. The Company is currently evaluating the effect the updated guidance will have on the Company’s financial statements, but anticipates the primary change to be the recognition of excess tax benefits or deficiencies on vesting or settlement of awards as an income tax benefit or expense within net income and the related cash flows classified within operating activities. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. The updated accounting guidance requires changes to the recognition of credit losses on financial instruments not accounted for at fair value through net income. The guidance is effective for interim and annual periods beginning after December 15, 2019. The Company is currently evaluating the effect the guidance will have on the Company's financial statements, but expects the primary changes to be the use of the expected credit loss model for its mortgage loan portfolio and reinsurance receivables and the presentation of credit losses within the available-for-sale fixed maturities portfolio through an allowance method rather than as a direct write-down. The expected credit loss model will require a financial asset to be presented at the net amount expected to be collected. The allowance method for available-for-sale debt securities will allow the Company to record reversals of credit losses if the estimate of credit losses declines.

Summary of Significant Accoun35

Summary of Significant Accounting Policies (Life Settlement Contracts) (Tables)	12 Months Ended
	Dec. 31, 2016
Life Settlement Contracts, Fair Value Method, Number of Contracts, Fiscal Year Maturity [Abstract]
Life settlement contracts	The following table details the values for life settlement contracts. The determination of fair value is discussed in Note C to the Consolidated Financial Statements. December 31, 2016 Number of Life Settlement Contracts Fair Value of Life Settlement Contracts (In millions) Face Amount of Life Insurance Policies (In millions) Estimated settlements during: 2017 63 $ 10 $ 34 2018 55 8 30 2019 49 7 26 2020 43 6 23 2021 36 4 19 Thereafter 280 23 153 Total 526 $ 58 $ 285

Investments (Tables)

Investments (Tables)	12 Months Ended
	Dec. 31, 2016
Investments [Abstract]
Net investment income	The significant components of Net investment income are presented in the following table. Years ended December 31 (In millions) 2016 2015 2014 Fixed maturity securities $ 1,819 $ 1,751 $ 1,803 Equity securities 10 12 12 Limited partnership investments 155 92 263 Mortgage loans 41 33 31 Short term investments 8 6 3 Trading portfolio 10 8 10 Other 4 1 3 Gross investment income 2,047 1,903 2,125 Investment expense (59 ) (63 ) (58 ) Net investment income $ 1,988 $ 1,840 $ 2,067
Net realized investment gains (losses)	Net realized investment gains (losses) are presented in the following table. Years ended December 31 (In millions) 2016 2015 2014 Net realized investment gains (losses): Fixed maturity securities: Gross realized gains $ 204 $ 131 $ 170 Gross realized losses (138 ) (197 ) (129 ) Net realized investment gains (losses) on fixed maturity securities 66 (66 ) 41 Equity securities: Gross realized gains 5 2 8 Gross realized losses (10 ) (25 ) (7 ) Net realized investment gains (losses) on equity securities (5 ) (23 ) 1 Derivatives (2 ) 10 (1 ) Short term investments and other (9 ) 12 16 Net realized investment gains (losses) $ 50 $ (67 ) $ 57
Net change in unrealized gains (losses) on investments	Net change in unrealized gains on investments is presented in the following table. Years ended December 31 (In millions) 2016 2015 2014 Net change in unrealized gains on investments: Fixed maturity securities $ 225 $ (1,114 ) $ 1,511 Equity securities (2 ) (6 ) 6 Other 1 1 — Total net change in unrealized gains on investments $ 224 $ (1,119 ) $ 1,517
Components of net other than temporary impairment losses recognized in earnings by asset type	The components of OTTI losses recognized in earnings by asset type are presented in the following table. Years ended December 31 (In millions) 2016 2015 2014 Fixed maturity securities available-for-sale: Corporate and other bonds $ 59 $ 104 $ 18 States, municipalities and political subdivisions — 18 46 Asset-backed: Residential mortgage-backed 10 8 5 Other asset-backed 3 1 1 Total asset-backed 13 9 6 Total fixed maturity securities available-for-sale 72 131 70 Equity securities available-for-sale -- Common stock 9 25 7 OTTI losses recognized in earnings $ 81 $ 156 $ 77
Summary of fixed maturity and equity securities	The following tables present a summary of fixed maturity and equity securities. December 31, 2016 Cost or Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Unrealized OTTI Losses (Gains) (In millions) Fixed maturity securities available-for-sale: Corporate and other bonds $ 17,711 $ 1,323 $ 76 $ 18,958 $ (1 ) States, municipalities and political subdivisions 12,060 1,213 33 13,240 (16 ) Asset-backed: Residential mortgage-backed 5,004 120 51 5,073 (28 ) Commercial mortgage-backed 2,016 48 24 2,040 — Other asset-backed 1,022 8 5 1,025 — Total asset-backed 8,042 176 80 8,138 (28 ) U.S. Treasury and obligations of government-sponsored enterprises 83 10 — 93 — Foreign government 435 13 3 445 — Redeemable preferred stock 18 1 — 19 — Total fixed maturity securities available-for-sale 38,349 2,736 192 40,893 $ (45 ) Total fixed maturity securities trading 12 12 Equity securities available-for-sale: Common stock 13 6 — 19 Preferred stock 93 2 4 91 Total equity securities available-for-sale 106 8 4 110 Total $ 38,467 $ 2,744 $ 196 $ 41,015 December 31, 2015 Cost or Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Unrealized OTTI Losses (Gains) (In millions) Fixed maturity securities available-for-sale: Corporate and other bonds $ 17,080 $ 1,019 $ 342 $ 17,757 $ — States, municipalities and political subdivisions 11,729 1,453 8 13,174 (4 ) Asset-backed: Residential mortgage-backed 4,935 154 17 5,072 (37 ) Commercial mortgage-backed 2,154 55 12 2,197 — Other asset-backed 923 6 8 921 — Total asset-backed 8,012 215 37 8,190 (37 ) U.S. Treasury and obligations of government-sponsored enterprises 62 5 — 67 — Foreign government 334 13 1 346 — Redeemable preferred stock 33 2 — 35 — Total fixed maturity securities available-for-sale 37,250 2,707 388 39,569 $ (41 ) Total fixed maturity securities trading 3 3 Equity securities available-for-sale: Common stock 46 3 1 48 Preferred stock 145 7 3 149 Total equity securities available-for-sale 191 10 4 197 Total $ 37,444 $ 2,717 $ 392 $ 39,769
Securities in a gross unrealized loss position	The following tables present the estimated fair value and gross unrealized losses of fixed maturity and equity securities in a gross unrealized loss position by the length of time in which the securities have continuously been in that position. Less than 12 Months 12 Months or Longer Total December 31, 2016 Estimated Fair Value Gross Unrealized Losses Estimated Fair Value Gross Unrealized Losses Estimated Fair Value Gross Unrealized Losses (In millions) Fixed maturity securities available-for-sale: Corporate and other bonds $ 2,615 $ 61 $ 254 $ 15 $ 2,869 $ 76 States, municipalities and political subdivisions 959 32 23 1 982 33 Asset-backed: Residential mortgage-backed 2,136 44 201 7 2,337 51 Commercial mortgage-backed 756 22 69 2 825 24 Other asset-backed 398 5 24 — 422 5 Total asset-backed 3,290 71 294 9 3,584 80 U.S. Treasury and obligations of government-sponsored enterprises 5 — — — 5 — Foreign government 108 3 — — 108 3 Redeemable preferred stock — — — — — — Total fixed maturity securities available-for-sale 6,977 167 571 25 7,548 192 Equity securities available-for-sale -- Preferred stock 12 — 13 4 25 4 Total $ 6,989 $ 167 $ 584 $ 29 $ 7,573 $ 196 Less than 12 Months 12 Months or Longer Total December 31, 2015 Estimated Fair Value Gross Unrealized Losses Estimated Fair Value Gross Unrealized Losses Estimated Fair Value Gross Unrealized Losses (In millions) Fixed maturity securities available-for-sale: Corporate and other bonds $ 4,882 $ 302 $ 162 $ 40 $ 5,044 $ 342 States, municipalities and political subdivisions 338 8 75 — 413 8 Asset-backed: Residential mortgage-backed 963 9 164 8 1,127 17 Commercial mortgage-backed 652 10 96 2 748 12 Other asset-backed 552 8 5 — 557 8 Total asset-backed 2,167 27 265 10 2,432 37 U.S. Treasury and obligations of government-sponsored enterprises 4 — — — 4 — Foreign government 54 1 — — 54 1 Redeemable preferred stock 3 — — — 3 — Total fixed maturity securities available-for-sale 7,448 338 502 50 7,950 388 Equity securities available-for-sale: Common Stock 3 1 — — 3 1 Preferred stock 13 3 — — 13 3 Total equity securities available-for-sale 16 4 — — 16 4 Total $ 7,464 $ 342 $ 502 $ 50 $ 7,966 $ 392
Activity related to the pretax fixed maturity credit loss component reflected within retained earnings for securities still held for which a portion of an OTTI loss was recognized in OCI	The following table presents the activity related to the pretax credit loss component reflected in Retained earnings on fixed maturity securities still held as of December 31, 2016 , 2015 and 2014 for which a portion of an OTTI loss was recognized in Other comprehensive income (loss). Years ended December 31 (In millions) 2016 2015 2014 Beginning balance of credit losses on fixed maturity securities $ 53 $ 62 $ 74 Reductions for securities sold during the period (16 ) (9 ) (9 ) Reductions for securities the Company intends to sell or more likely than not will be required to sell (1 ) — (3 ) Ending balance of credit losses on fixed maturity securities $ 36 $ 53 $ 62
Contractual maturity	The following table presents available-for-sale fixed maturity securities by contractual maturity. December 31 2016 2015 (In millions) Cost or Amortized Cost Estimated Fair Value Cost or Amortized Cost Estimated Fair Value Due in one year or less $ 1,779 $ 1,828 $ 1,574 $ 1,595 Due after one year through five years 7,566 7,955 7,721 8,070 Due after five years through ten years 15,892 16,332 14,652 14,915 Due after ten years 13,112 14,778 13,303 14,989 Total $ 38,349 $ 40,893 $ 37,250 $ 39,569

Fair Value (Tables)

Fair Value (Tables)	12 Months Ended
	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Assets and liabilities measured at fair value on a recurring basis	Assets and liabilities measured at fair value on a recurring basis are presented in the following tables. December 31, 2016 Total Assets/Liabilities at Fair Value (In millions) Level 1 Level 2 Level 3 Assets Fixed maturity securities: Corporate and other bonds $ — $ 18,840 $ 130 $ 18,970 States, municipalities and political subdivisions — 13,239 1 13,240 Asset-backed: Residential mortgage-backed — 4,944 129 5,073 Commercial mortgage-backed — 2,027 13 2,040 Other asset-backed — 968 57 1,025 Total asset-backed — 7,939 199 8,138 U.S. Treasury and obligations of government-sponsored enterprises 93 — — 93 Foreign government — 445 — 445 Redeemable preferred stock 19 — — 19 Total fixed maturity securities 112 40,463 330 40,905 Equity securities 91 — 19 110 Other invested assets — 5 — 5 Short term investments 475 853 — 1,328 Life settlement contracts, included in Other assets — — 58 58 Total assets $ 678 $ 41,321 $ 407 $ 42,406 Liabilities Other liabilities $ — $ (3 ) $ — $ (3 ) Total liabilities $ — $ (3 ) $ — $ (3 ) December 31, 2015 Total Assets/Liabilities at Fair Value (In millions) Level 1 Level 2 Level 3 Assets Fixed maturity securities: Corporate and other bonds $ — $ 17,592 $ 168 $ 17,760 States, municipalities and political subdivisions — 13,172 2 13,174 Asset-backed: Residential mortgage-backed — 4,938 134 5,072 Commercial mortgage-backed — 2,175 22 2,197 Other asset-backed — 868 53 921 Total asset-backed — 7,981 209 8,190 U.S. Treasury and obligations of government-sponsored enterprises 66 1 — 67 Foreign government — 346 — 346 Redeemable preferred stock 35 — — 35 Total fixed maturity securities 101 39,092 379 39,572 Equity securities 177 — 20 197 Other invested assets — 17 — 17 Short term investments 448 1,134 — 1,582 Life settlement contracts, included in Other assets — — 74 74 Total assets $ 726 $ 40,243 $ 473 $ 41,442 Liabilities Other liabilities $ — $ (5 ) $ — $ (5 ) Total liabilities $ — $ (5 ) $ — $ (5 )
Table of reconciliation for assets and liablities measured at fair value on a recurring basis using significant unobservable inputs	The tables below present a reconciliation for all assets and liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3). Level 3 (In millions) Balance as of January 1, 2016 Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)* Net change in unrealized appreciation (depreciation) included in Other comprehensive income (loss) Purchases Sales Settlements Transfers into Level 3 Transfers out of Level 3 Balance as of December 31, 2016 Unrealized gains (losses) on Level 3 assets and liabilities held as of December 31, 2016 recognized in Net income (loss)* Fixed maturity securities: Corporate and other bonds $ 168 $ 1 $ 1 $ 163 $ (36 ) $ (103 ) $ — $ (64 ) $ 130 $ — States, municipalities and political subdivisions 2 — — — — (1 ) — — 1 — Asset-backed: Residential mortgage-backed 134 3 (5 ) 15 — (14 ) 56 (60 ) 129 — Commercial mortgage-backed 22 (1 ) (1 ) 32 — (17 ) 3 (25 ) 13 — Other asset-backed 53 (2 ) 1 86 (25 ) (1 ) 2 (57 ) 57 — Total asset-backed 209 — (5 ) 133 (25 ) (32 ) 61 (142 ) 199 — Total fixed maturity securities 379 1 (4 ) 296 (61 ) (136 ) 61 (206 ) 330 — Equity securities 20 (1 ) — — — — — — 19 (2 ) Life settlement contracts 74 5 — — — (21 ) — — 58 (3 ) Total $ 473 $ 5 $ (4 ) $ 296 $ (61 ) $ (157 ) $ 61 $ (206 ) $ 407 $ (5 ) Level 3 (In millions) Balance as of January 1, 2015 Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)* Net change in unrealized appreciation (depreciation) included in Other comprehensive income (loss) Purchases Sales Settlements Transfers into Level 3 Transfers out of Level 3 Balance as of December 31, 2015 Unrealized gains (losses) on Level 3 assets and liabilities held as of December 31, 2015 recognized in Net income (loss)* Fixed maturity securities: Corporate and other bonds $ 162 $ (2 ) $ (3 ) $ 65 $ (13 ) $ (35 ) $ 40 $ (46 ) $ 168 $ (2 ) States, municipalities and political subdivisions 94 1 — — — (10 ) — (83 ) 2 — Asset-backed: Residential mortgage-backed 189 5 (3 ) 81 — (35 ) 14 (117 ) 134 — Commercial mortgage-backed 83 7 (4 ) 23 — (17 ) 17 (87 ) 22 — Other asset-backed 655 3 3 130 (263 ) (52 ) 7 (430 ) 53 — Total asset-backed 927 15 (4 ) 234 (263 ) (104 ) 38 (634 ) 209 — Total fixed maturity securities 1,183 14 (7 ) 299 (276 ) (149 ) 78 (763 ) 379 (2 ) Equity securities 16 — (1 ) 4 — — 1 — 20 — Life settlement contracts 82 25 — — — (33 ) — — 74 1 Total $ 1,281 $ 39 $ (8 ) $ 303 $ (276 ) $ (182 ) $ 79 $ (763 ) $ 473 $ (1 )
Quantitative information about significant unobservable inputs in the fair value measurement of level 3 assets	The following tables present quantitative information about the significant unobservable inputs utilized by the Company in the fair value measurements of Level 3 assets. Valuations for assets and liabilities not presented in the tables below are primarily based on broker/dealer quotes for which there is a lack of transparency as to inputs used to develop the valuations. The quantitative detail of these unobservable inputs is neither provided nor reasonably available to the Company. The valuation of life settlement contracts as of December 31, 2016 was based on the terms of the pending sale of the contracts to a third party, therefore the contracts are not included in the table below. December 31, 2016 Estimated Fair Value (In millions) Valuation Technique(s) Unobservable Input(s) Range (Weighted Average) Fixed maturity securities $ 106 Discounted cash flow Credit spread 2% - 40% (4%) December 31, 2015 Estimated Fair Value Valuation Technique(s) Unobservable Input(s) Range (Weighted Average) Fixed maturity securities $ 138 Discounted cash flow Credit spread 3% - 184% (6%) Life settlement contracts 74 Discounted cash flow Discount rate risk premium 9% Mortality assumption 55% - 1676% (164%)
Carrying amount and estimated fair value of financial instrument assets and liabilities not measured at fair value	The carrying amount and estimated fair value of the Company's financial assets and liabilities which are not measured at fair value on the Consolidated Balance Sheets are presented in the following tables. December 31, 2016 Carrying Amount Estimated Fair Value (In millions) Level 1 Level 2 Level 3 Total Assets Mortgage loans $ 591 $ — $ — $ 594 $ 594 Liabilities Long term debt $ 2,710 $ — $ 2,952 $ — $ 2,952 December 31, 2015 Carrying Estimated Fair Value (In millions) Level 1 Level 2 Level 3 Total Assets Mortgage loans $ 678 $ — $ — $ 688 $ 688 Liabilities Short term debt $ 350 $ — $ 360 $ — $ 360 Long term debt 2,210 — 2,433 — 2,433

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Reconcilliation between the Company's federal income tax (expense) benefit at statutory rates and the recorded income tax (expense) benefit	The following table presents a reconciliation between the Company's federal income tax expense at statutory rates and the recorded income tax expense, excluding discontinued operations. Years ended December 31 (In millions) 2016 2015 2014 Income tax expense at statutory rates $ (398 ) $ (192 ) $ (423 ) Tax benefit from tax exempt income 124 123 119 Foreign taxes and credits 3 9 (6 ) Other tax expense (7 ) (10 ) (9 ) Income tax expense $ (278 ) $ (70 ) $ (319 )
Current and deferred components of the Company's income tax (expense) benefit	The following table presents the current and deferred components of the Company's income tax expense, excluding discontinued operations. Years ended December 31 (In millions) 2016 2015 2014 Current tax expense $ (142 ) $ (220 ) $ (318 ) Deferred tax benefit (expense) (136 ) 150 (1 ) Total income tax expense $ (278 ) $ (70 ) $ (319 )
Significant components of the Company's deferred tax assets and liabilities	The deferred tax effects of the significant components of the Company's deferred tax assets and liabilities are presented in the following table. December 31 (In millions) 2016 2015 Deferred Tax Assets: Insurance reserves: Property and casualty claim and claim adjustment expense reserves $ 125 $ 178 Unearned premium reserves 206 230 Receivables 27 29 Employee benefits 272 281 Life settlement contracts 56 48 Deferred retroactive reinsurance benefit 117 84 Investment valuation differences — 29 Other assets 148 142 Gross deferred tax assets 951 1,021 Deferred Tax Liabilities: Investment valuation differences 57 — Deferred acquisition costs 120 117 Net unrealized gains 309 202 Other liabilities 86 64 Gross deferred tax liabilities 572 383 Net deferred tax asset $ 379 $ 638

Claim and Claim Adjustment Ex39

Claim and Claim Adjustment Expense Reserves (Tables)	12 Months Ended
	Dec. 31, 2016
Liability for Claims and Claims Adjustment Expense [Abstract]
Schedule of Liability for Unpaid Claims and Claims Adjustment Expense [Table Text Block]	The following table presents a reconciliation between beginning and ending claim and claim adjustment expense reserves, including claim and claim adjustment expense reserves of the Life & Group Non-Core segment. As of or for the years ended December 31 (In millions) 2016 2015 2014 Reserves, beginning of year: Gross $ 22,663 $ 23,271 $ 24,089 Ceded 4,087 4,344 4,972 Net reserves, beginning of year 18,576 18,927 19,117 Change in net reserves due to acquisition (disposition) of subsidiaries — — (13 ) Net incurred claim and claim adjustment expenses: Provision for insured events of current year 5,025 4,934 5,043 Decrease in provision for insured events of prior years (342 ) (255 ) (36 ) Amortization of discount 175 166 161 Total net incurred (1) 4,858 4,845 5,168 Net payments attributable to: Current year events (967 ) (856 ) (945 ) Prior year events (4,167 ) (4,089 ) (4,355 ) Total net payments (5,134 ) (4,945 ) (5,300 ) Foreign currency translation adjustment and other (51 ) (251 ) (45 ) Net reserves, end of year 18,249 18,576 18,927 Ceded reserves, end of year 4,094 4,087 4,344 Gross reserves, end of year $ 22,343 $ 22,663 $ 23,271 (1) Total net incurred above does not agree to Insurance claims and policyholders' benefits as reflected on the Consolidated Statements of Operations due to amounts related to retroactive reinsurance deferred gain accounting, uncollectible reinsurance and loss deductible receivables, and benefit expenses related to future policy benefits, which are not reflected in the table above.
Gross and net carried claim and claim adjustment expense reserves	The following tables present the gross and net carried reserves. December 31, 2016 Specialty Commercial International Life & Group Non-Core Corporate & Other Non-Core Total (In millions) Gross Case Reserves $ 1,871 $ 4,661 $ 632 $ 3,172 $ 1,524 $ 11,860 Gross IBNR Reserves 4,278 4,233 696 186 1,090 10,483 Total Gross Carried Claim and Claim Adjustment Expense Reserves $ 6,149 $ 8,894 $ 1,328 $ 3,358 $ 2,614 $ 22,343 Net Case Reserves $ 1,681 $ 4,353 $ 548 $ 2,951 $ 94 $ 9,627 Net IBNR Reserves 3,723 3,952 653 158 136 8,622 Total Net Carried Claim and Claim Adjustment Expense Reserves $ 5,404 $ 8,305 $ 1,201 $ 3,109 $ 230 $ 18,249 December 31, 2015 Specialty Commercial International Life & Group Non-Core Corporate & Other Non-Core Total (In millions) Gross Case Reserves $ 2,011 $ 4,975 $ 622 $ 2,973 $ 1,521 $ 12,102 Gross IBNR Reserves 4,258 4,208 725 247 1,123 10,561 Total Gross Carried Claim and Claim Adjustment Expense Reserves $ 6,269 $ 9,183 $ 1,347 $ 3,220 $ 2,644 $ 22,663 Net Case Reserves $ 1,810 $ 4,651 $ 531 $ 2,714 $ 130 $ 9,836 Net IBNR Reserves 3,758 3,925 688 216 153 8,740 Total Net Carried Claim and Claim Adjustment Expense Reserves $ 5,568 $ 8,576 $ 1,219 $ 2,930 $ 283 $ 18,576
Net prior year development	Changes in estimates of claim and allocated claim adjustment expense reserves and premium accruals, net of reinsurance, for prior years are defined as net prior year development. These changes can be favorable or unfavorable. The following tables and discussion present the net prior year development recorded for Specialty, Commercial, International and Corporate & Other Non-Core segments. Year ended December 31, 2016 (In millions) Specialty Commercial International Corporate & Other Non-Core Total Pretax (favorable) unfavorable net prior year claim and allocated claim adjustment expense reserve development $ (287 ) $ 55 $ (58 ) $ 2 $ (288 ) Pretax (favorable) unfavorable premium development (18 ) (2 ) (6 ) — (26 ) Total pretax (favorable) unfavorable net prior year development $ (305 ) $ 53 $ (64 ) $ 2 $ (314 ) Year ended December 31, 2015 (In millions) Specialty Commercial International Corporate & Other Non-Core Total Pretax (favorable) unfavorable net prior year claim and allocated claim adjustment expense reserve development $ (141 ) $ (15 ) $ (54 ) $ — $ (210 ) Pretax (favorable) unfavorable premium development (11 ) (15 ) 18 — (8 ) Total pretax (favorable) unfavorable net prior year development $ (152 ) $ (30 ) $ (36 ) $ — $ (218 ) Year ended December 31, 2014 (In millions) Specialty Commercial International Corporate & Other Non-Core Total Pretax (favorable) unfavorable net prior year claim and allocated claim adjustment expense reserve development $ (136 ) $ 176 $ (59 ) $ (2 ) $ (21 ) Pretax (favorable) unfavorable premium development (13 ) (20 ) 2 (1 ) (32 ) Total pretax (favorable) unfavorable net prior year development $ (149 ) $ 156 $ (57 ) $ (3 ) $ (53 )
Specialty [Member]
Net Incurred Claim and Claim Adjustment Expense [Line Items]
Net prior year claim and allocated claim adjustment expense reserve development	The following table presents further detail of the net prior year claim and allocated claim adjustment expense reserve development (development) recorded for the Specialty segment. Years ended December 31 (In millions) 2016 2015 2014 Pretax (favorable) unfavorable development: Medical Professional Liability $ (37 ) $ (43 ) $ 39 Other Professional Liability and Management Liability (130 ) — (87 ) Surety (63 ) (69 ) (82 ) Warranty 4 (2 ) (2 ) Other (61 ) (27 ) (4 ) Total pretax (favorable) unfavorable development $ (287 ) $ (141 ) $ (136 )
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Table Text Block]	The table below provides the line of business composition of the net liability for unpaid claim and claim adjustment expenses for the Specialty segment. As of December 31 (In millions) 2016 Net liability for unpaid claim and claim adjustment expenses: Medical Professional Liability $ 1,779 Other Professional Liability and Management Liability 3,063 Surety 394 Warranty 37 Other 131 Total net liability for unpaid claim and claim adjustment expenses $ 5,404
Specialty - Medical Professional Liability [Member]
Net Incurred Claim and Claim Adjustment Expense [Line Items]
Short-Duration Contracts Net Incurred Claims and Allocated Claim Adjustment Expenses [Table Text Block]	Cumulative Net Incurred Claim and Allocated Claim Adjustment Expenses are presented in the following table. As of December 31 Calendar Year As of December 31, 2016 (In millions, except reported claims data) 2007 (1) 2008 (1) 2009 (1) 2010 (1) 2011 (1) 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 IBNR Cumulative Number of Claims Accident Year 2007 $ 448 $ 452 $ 444 $ 427 $ 395 $ 391 $ 390 $ 401 $ 399 $ 385 $ 9 12,122 2008 426 451 496 480 468 468 467 455 442 9 14,094 2009 462 469 494 506 480 471 463 432 12 15,573 2010 483 478 478 486 470 446 403 16 15,206 2011 486 492 507 533 501 491 23 17,428 2012 526 529 575 567 559 47 18,375 2013 534 540 560 567 95 19,565 2014 511 548 585 165 19,286 2015 480 539 278 16,798 2016 469 400 11,600 Total $ 4,872 $ 1,054
Short-Duration Contracts Net Cumulative Paid Claim Adjustment Expenses Reconciliation of Total Liability for Unpaid Claim and Claim Adjustment Expense [Table Text Block]	Cumulative Net Paid Claims and Allocated Claim Adjustment Expenses are presented in the following table. As of December 31 Calendar Year (In millions) 2007 (1) 2008 (1) 2009 (1) 2010 (1) 2011 (1) 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 Accident Year 2007 $ 11 $ 68 $ 134 $ 201 $ 247 $ 296 $ 326 $ 352 $ 364 $ 365 2008 9 90 207 282 332 377 395 409 428 2009 9 75 180 278 328 353 377 396 2010 11 93 186 273 338 361 371 2011 18 121 225 315 379 407 2012 15 121 236 359 428 2013 18 121 259 364 2014 25 149 274 2015 22 105 2016 18 Total $ 3,156 Net liability for unpaid claim and allocated claim adjustment expenses for the accident years presented $ 1,716 Net liability for unpaid claim and claim adjustment expenses for accident years prior to 2007 30 Liability for unallocated claim adjustment expenses for accident years presented 33 Total net liability for unpaid claim and claim adjustment expenses $ 1,779
Short-Duration Contracts Reserve Development [Table Text Block]	Net strengthening or (releases) of prior accident year reserves is presented in the following table. For the years ended December 31 Calendar Year (In millions) 2008 (1) 2009 (1) 2010 (1) 2011 (1) 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 Total Accident Year 2007 $ 4 $ (8 ) $ (17 ) $ (32 ) $ (4 ) $ (1 ) $ 11 $ (2 ) $ (14 ) $ (63 ) 2008 25 45 (16 ) (12 ) — (1 ) (12 ) (13 ) 16 2009 7 25 12 (26 ) (9 ) (8 ) (31 ) (30 ) 2010 (5 ) — 8 (16 ) (24 ) (43 ) (80 ) 2011 6 15 26 (32 ) (10 ) 5 2012 3 46 (8 ) (8 ) 33 2013 6 20 7 33 2014 37 37 74 2015 59 59 Total net development for the accident years presented above $ 63 $ (29 ) $ (16 ) Total net development for accident years prior to 2007 (24 ) (14 ) (21 ) Total $ 39 $ (43 ) $ (37 ) (1) Data presented for these calendar years is required supplemental information, which is unaudited.
Specialty - Other Professional and Management Liability [Member]
Net Incurred Claim and Claim Adjustment Expense [Line Items]
Short-Duration Contracts Net Incurred Claims and Allocated Claim Adjustment Expenses [Table Text Block]	Cumulative Net Incurred Claim and Allocated Claim Adjustment Expenses are presented in the following table. As of December 31 Calendar Year As of December 31, 2016 (In millions, except reported claims data) 2007 (1) 2008 (1) 2009 (1) 2010 (1) 2011 (1) 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 IBNR Cumulative Number of Claims Accident Year 2007 $ 804 $ 817 $ 806 $ 754 $ 734 $ 724 $ 704 $ 681 $ 662 $ 662 $ 13 16,011 2008 916 933 954 924 915 880 850 845 827 35 16,326 2009 829 873 903 898 891 900 895 903 50 17,263 2010 825 827 850 848 846 836 823 39 17,796 2011 876 904 933 948 944 910 107 18,620 2012 907 894 876 870 833 107 18,228 2013 844 841 879 840 137 17,324 2014 841 859 854 306 16,886 2015 847 851 478 16,391 2016 859 742 15,045 Total $ 8,362 $ 2,014
Short-Duration Contracts Net Cumulative Paid Claim Adjustment Expenses Reconciliation of Total Liability for Unpaid Claim and Claim Adjustment Expense [Table Text Block]	Cumulative Net Paid Claims and Allocated Claim Adjustment Expenses are presented in the following table. As of December 31 Calendar Year (In millions) 2007 (1) 2008 (1) 2009 (1) 2010 (1) 2011 (1) 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 Accident Year 2007 $ 32 $ 162 $ 307 $ 397 $ 472 $ 524 $ 564 $ 585 $ 593 $ 614 2008 39 181 376 515 600 641 678 719 741 2009 37 195 358 550 638 719 769 798 2010 31 203 404 541 630 670 721 2011 71 313 502 604 682 726 2012 57 248 398 570 648 2013 51 240 426 583 2014 51 212 375 2015 48 209 2016 60 Total $ 5,475 Net liability for unpaid claim and allocated claim adjustment expenses for the accident years presented $ 2,887 Net liability for unpaid claim and claim adjustment expenses for accident years prior to 2007 104 Liability for unallocated claim adjustment expenses for accident years presented 72 Total net liability for unpaid claim and claim adjustment expenses $ 3,063
Short-Duration Contracts Reserve Development [Table Text Block]	Net strengthening or (releases) of prior accident year reserves is presented in the following table. For the years ended December 31 Calendar Year (In millions) 2008 (1) 2009 (1) 2010 (1) 2011 (1) 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 Total Accident Year 2007 $ 13 $ (11 ) $ (52 ) $ (20 ) $ (10 ) $ (20 ) $ (23 ) $ (19 ) $ — $ (142 ) 2008 17 21 (30 ) (9 ) (35 ) (30 ) (5 ) (18 ) (89 ) 2009 44 30 (5 ) (7 ) 9 (5 ) 8 74 2010 2 23 (2 ) (2 ) (10 ) (13 ) (2 ) 2011 28 29 15 (4 ) (34 ) 34 2012 (13 ) (18 ) (6 ) (37 ) (74 ) 2013 (3 ) 38 (39 ) (4 ) 2014 18 (5 ) 13 2015 4 4 Total net development for the accident years presented above $ (52 ) $ 7 $ (134 ) Total net development for accident years prior to 2007 (35 ) (7 ) 4 Total $ (87 ) $ — $ (130 ) (1) Data presented for these calendar years is required supplemental information, which is unaudited.
Specialty - Surety [Member]
Net Incurred Claim and Claim Adjustment Expense [Line Items]
Short-Duration Contracts Net Incurred Claims and Allocated Claim Adjustment Expenses [Table Text Block]	Cumulative Net Incurred Claim and Allocated Claim Adjustment Expenses are presented in the following table. As of December 31 Calendar Year As of December 31, 2016 (In millions, except reported claims data) 2007 (1) 2008 (1) 2009 (1) 2010 (1) 2011 (1) 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 IBNR Cumulative Number of Claims Accident Year 2007 $ 98 $ 107 $ 81 $ 57 $ 59 $ 56 $ 51 $ 49 $ 49 $ 50 $ — 6,270 2008 114 114 73 68 61 52 48 45 44 — 7,153 2009 114 114 103 85 68 59 52 53 1 6,654 2010 112 112 111 84 76 66 63 8 5,943 2011 120 121 116 87 75 70 9 5,760 2012 120 122 98 70 52 16 5,473 2013 120 121 115 106 24 4,890 2014 123 124 94 51 4,737 2015 131 131 100 4,279 2016 124 110 2,902 Total $ 787 $ 319
Short-Duration Contracts Net Cumulative Paid Claim Adjustment Expenses Reconciliation of Total Liability for Unpaid Claim and Claim Adjustment Expense [Table Text Block]	Cumulative Net Paid Claims and Allocated Claim Adjustment Expenses are presented in the following table. As of December 31 Calendar Year (In millions) 2007 (1) 2008 (1) 2009 (1) 2010 (1) 2011 (1) 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 Accident Year 2007 $ 12 $ 30 $ 40 $ 45 $ 46 $ 46 $ 46 $ 48 $ 49 $ 50 2008 9 27 35 39 42 43 43 43 43 2009 13 24 34 41 43 45 46 47 2010 13 34 50 55 57 58 55 2011 19 42 55 58 60 60 2012 5 32 34 35 35 2013 16 40 69 78 2014 7 30 38 2015 7 26 2016 5 Total $ 437 Net liability for unpaid claim and allocated claim adjustment expenses for the accident years presented $ 350 Net liability for unpaid claim and claim adjustment expenses for accident years prior to 2007 16 Liability for unallocated claim adjustment expenses for accident years presented 28 Total net liability for unpaid claim and claim adjustment expenses $ 394
Short-Duration Contracts Reserve Development [Table Text Block]	Net strengthening or (releases) of prior accident year reserves is presented in the following table. For the years ended December 31 Calendar Year (In millions) 2008 (1) 2009 (1) 2010 (1) 2011 (1) 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 Total Accident Year 2007 $ 9 $ (26 ) $ (24 ) $ 2 $ (3 ) $ (5 ) $ (2 ) $ — $ 1 $ (48 ) 2008 — (41 ) (5 ) (7 ) (9 ) (4 ) (3 ) (1 ) (70 ) 2009 — (11 ) (18 ) (17 ) (9 ) (7 ) 1 (61 ) 2010 — (1 ) (27 ) (8 ) (10 ) (3 ) (49 ) 2011 1 (5 ) (29 ) (12 ) (5 ) (50 ) 2012 2 (24 ) (28 ) (18 ) (68 ) 2013 1 (6 ) (9 ) (14 ) 2014 1 (30 ) (29 ) 2015 — — Total net development for the accident years presented above $ (75 ) $ (65 ) $ (64 ) Total net development for accident years prior to 2007 (7 ) (4 ) 1 Total $ (82 ) $ (69 ) $ (63 ) (1) Data presented for these calendar years is required supplemental information, which is unaudited.
Commercial [Member]
Net Incurred Claim and Claim Adjustment Expense [Line Items]
Net prior year claim and allocated claim adjustment expense reserve development	The following table presents further detail of the development recorded for the Commercial segment. Years ended December 31 (In millions) 2016 2015 2014 Pretax (favorable) unfavorable development: Commercial Auto $ (46 ) $ (22 ) $ 31 General Liability (28 ) (33 ) 45 Workers' Compensation 150 80 139 Property and Other (21 ) (40 ) (39 ) Total pretax (favorable) unfavorable development $ 55 $ (15 ) $ 176
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Table Text Block]	The table below provides the line of business composition of the net liability for unpaid claim and claim adjustment expenses for the Commercial segment. As of December 31 (In millions) 2016 Net Claim and claim adjustment expenses: Commercial Auto $ 424 General Liability 3,248 Workers' Compensation 4,306 Property and Other 327 Total net liability for claim and claim adjustment expenses $ 8,305
Commercial - Auto [Member]
Net Incurred Claim and Claim Adjustment Expense [Line Items]
Short-Duration Contracts Net Incurred Claims and Allocated Claim Adjustment Expenses [Table Text Block]	Cumulative Net Incurred Claim and Allocated Claim Adjustment Expenses are presented in the following table. As of December 31 Calendar Year As of December 31, 2016 (In millions, except reported claims data) 2007 (1) 2008 (1) 2009 (1) 2010 (1) 2011 (1) 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 IBNR Cumulative Number of Claims Accident Year 2007 $ 348 $ 367 $ 368 $ 360 $ 355 $ 358 $ 356 $ 355 $ 354 $ 352 $ — 67,473 2008 322 323 316 306 309 305 298 298 296 — 56,407 2009 287 272 274 278 281 277 275 272 — 47,325 2010 262 274 279 283 291 286 281 1 46,324 2011 262 273 279 293 290 285 5 46,676 2012 270 282 292 296 300 11 45,279 2013 242 259 257 241 20 38,513 2014 231 221 210 40 32,958 2015 199 197 65 29,714 2016 196 105 25,196 Total $ 2,630 $ 247
Short-Duration Contracts Net Cumulative Paid Claim Adjustment Expenses Reconciliation of Total Liability for Unpaid Claim and Claim Adjustment Expense [Table Text Block]	Cumulative Net Paid Claims and Allocated Claim Adjustment Expenses are presented in the following table. As of December 31 Calendar Year (In millions) 2007 (1) 2008 (1) 2009 (1) 2010 (1) 2011 (1) 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 Accident Year 2007 $ 93 $ 185 $ 250 $ 295 $ 329 $ 340 $ 348 $ 349 $ 350 $ 351 2008 83 158 210 244 274 289 291 292 293 2009 72 128 188 229 257 269 270 270 2010 72 137 197 240 265 274 279 2011 78 141 193 241 264 275 2012 77 157 214 253 276 2013 73 132 164 195 2014 63 100 135 2015 52 95 2016 51 Total $ 2,220 Net liability for unpaid claim and allocated claim adjustment expenses for the accident years presented $ 410 Net liability for unpaid claim and claim adjustment expenses for accident years prior to 2007 4 Liability for unallocated claim adjustment expenses for accident years presented 10 Total net liability for unpaid claim and claim adjustment expenses $ 424
Short-Duration Contracts Reserve Development [Table Text Block]	Net strengthening or (releases) of prior accident year reserves is presented in the following table. For the years ended December 31 Calendar Year (In millions) 2008 (1) 2009 (1) 2010 (1) 2011 (1) 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 Total Accident Year 2007 $ 19 $ 1 $ (8 ) $ (5 ) $ 3 $ (2 ) $ (1 ) $ (1 ) $ (2 ) $ 4 2008 1 (7 ) (10 ) 3 (4 ) (7 ) — (2 ) (26 ) 2009 (15 ) 2 4 3 (4 ) (2 ) (3 ) (15 ) 2010 12 5 4 8 (5 ) (5 ) 19 2011 11 6 14 (3 ) (5 ) 23 2012 12 10 4 4 30 2013 17 (2 ) (16 ) (1 ) 2014 (10 ) (11 ) (21 ) 2015 (2 ) (2 ) Total net development for the accident years presented above $ 37 $ (19 ) $ (42 ) Total net development for accident years prior to 2007 (6 ) (3 ) (4 ) Total $ 31 $ (22 ) $ (46 ) (1) Data presented for these calendar years is required supplemental information, which is unaudited.
Commercial - General Liability [Member]
Net Incurred Claim and Claim Adjustment Expense [Line Items]
Short-Duration Contracts Net Incurred Claims and Allocated Claim Adjustment Expenses [Table Text Block]	Cumulative Net Incurred Claim and Allocated Claim Adjustment Expenses are presented in the following table. As of December 31 Calendar Year As of December 31, 2016 (In millions, except reported claims data) 2007 (1) 2008 (1) 2009 (1) 2010 (1) 2011 (1) 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 IBNR Cumulative Number of Claims Accident Year 2007 $ 774 $ 673 $ 678 $ 639 $ 610 $ 600 $ 559 $ 545 $ 548 $ 540 $ 28 53,553 2008 611 604 630 647 633 632 613 600 591 18 44,586 2009 591 637 634 633 629 623 619 622 16 43,955 2010 566 597 599 649 695 675 659 25 43,378 2011 537 534 564 610 611 621 41 38,101 2012 539 563 579 570 558 63 34,037 2013 615 645 634 643 142 32,897 2014 627 634 635 224 26,744 2015 573 574 330 21,687 2016 622 495 16,720 Total $ 6,065 $ 1,382
Short-Duration Contracts Net Cumulative Paid Claim Adjustment Expenses Reconciliation of Total Liability for Unpaid Claim and Claim Adjustment Expense [Table Text Block]	Cumulative Net Paid Claims and Allocated Claim Adjustment Expenses are presented in the following table. As of December 31 Calendar Year (In millions) 2007 (1) 2008 (1) 2009 (1) 2010 (1) 2011 (1) 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 Accident Year 2007 $ 30 $ 130 $ 236 $ 328 $ 413 $ 458 $ 481 $ 492 $ 497 $ 504 2008 31 129 261 390 473 528 550 560 567 2009 33 112 270 392 486 532 557 584 2010 27 139 267 414 530 577 608 2011 27 135 253 389 484 534 2012 27 127 233 340 417 2013 33 135 257 377 2014 29 115 245 2015 31 132 2016 34 Total $ 4,002 Net liability for unpaid claim and allocated claim adjustment expenses for the accident years presented $ 2,063 Net liability for unpaid claim and claim adjustment expenses for accident years prior to 2007 1,130 Liability for unallocated claim adjustment expenses for accident years presented 55 Total net liability for unpaid claim and claim adjustment expenses $ 3,248
Short-Duration Contracts Reserve Development [Table Text Block]	Net strengthening or (releases) of prior accident year reserves is presented in the following table. For the years ended December 31 Calendar Year (In millions) 2008 (1) 2009 (1) 2010 (1) 2011 (1) 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 Total Accident Year 2007 $ (101 ) $ 5 $ (39 ) $ (29 ) $ (10 ) $ (41 ) $ (14 ) $ 3 $ (8 ) $ (234 ) 2008 (7 ) 26 17 (14 ) (1 ) (19 ) (13 ) (9 ) (20 ) 2009 46 (3 ) (1 ) (4 ) (6 ) (4 ) 3 31 2010 31 2 50 46 (20 ) (16 ) 93 2011 (3 ) 30 46 1 10 84 2012 24 16 (9 ) (12 ) 19 2013 30 (11 ) 9 28 2014 7 1 8 2015 1 1 Total net development for the accident years presented above $ 99 $ (46 ) $ (21 ) Total net development for accident years prior to 2007 (54 ) 13 (7 ) Total $ 45 $ (33 ) $ (28 ) (1) Data presented for these calendar years is required supplemental information, which is unaudited.
Commercial - Workers Compensation [Member]
Net Incurred Claim and Claim Adjustment Expense [Line Items]
Short-Duration Contracts Net Incurred Claims and Allocated Claim Adjustment Expenses [Table Text Block]	Cumulative Net Incurred Claim and Allocated Claim Adjustment Expenses are presented in the following table. As of December 31 Calendar Year As of December 31, 2016 (In millions, except reported claims data) 2007 (1) 2008 (1) 2009 (1) 2010 (1) 2011 (1) 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 IBNR Cumulative Number of Claims Accident Year 2007 $ 568 $ 580 $ 596 $ 604 $ 603 $ 603 $ 604 $ 610 $ 608 $ 627 $ 32 71,049 2008 558 575 593 606 608 612 622 630 638 36 59,883 2009 583 587 594 596 600 611 617 625 46 51,111 2010 576 619 641 663 683 697 717 45 48,056 2011 593 628 637 648 642 666 52 44,571 2012 589 616 648 661 671 86 41,683 2013 528 563 584 610 121 38,102 2014 459 474 474 157 32,996 2015 416 426 206 31,296 2016 421 287 27,042 Total $ 5,875 $ 1,068
Short-Duration Contracts Net Cumulative Paid Claim Adjustment Expenses Reconciliation of Total Liability for Unpaid Claim and Claim Adjustment Expense [Table Text Block]	Cumulative Net Paid Claims and Allocated Claim Adjustment Expenses are presented in the following table. As of December 31 Calendar Year (In millions) 2007 (1) 2008 (1) 2009 (1) 2010 (1) 2011 (1) 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 Accident Year 2007 $ 100 $ 246 $ 337 $ 390 $ 429 $ 471 $ 502 $ 522 $ 533 $ 535 2008 92 233 323 381 425 461 489 505 520 2009 88 223 315 381 435 468 495 516 2010 94 245 352 433 500 531 565 2011 97 245 353 432 471 515 2012 86 229 338 411 465 2013 79 211 297 366 2014 60 157 213 2015 50 130 2016 52 Total $ 3,877 Net liability for unpaid claim and allocated claim adjustment expenses for the accident years presented $ 1,998 Net liability for unpaid claim and claim adjustment expenses for accident years prior to 2007 2,334 Other (2) (30 ) Liability for unallocated claim adjustment expenses for accident years presented 4 Total net liability for unpaid claim and claim adjustment expenses $ 4,306 (2) Other includes the effect of discounting lifetime claim reserves.
Short-Duration Contracts Reserve Development [Table Text Block]	Net strengthening or (releases) of prior accident year reserves is presented in the following table. For the years ended December 31 Calendar Year (In millions) 2008 (1) 2009 (1) 2010 (1) 2011 (1) 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 Total Accident Year 2007 $ 12 $ 16 $ 8 $ (1 ) $ — $ 1 $ 6 $ (2 ) $ 19 $ 59 2008 17 18 13 2 4 10 8 8 80 2009 4 7 2 4 11 6 8 42 2010 43 22 22 20 14 20 141 2011 35 9 11 (6 ) 24 73 2012 27 32 13 10 82 2013 35 21 26 82 2014 15 — 15 2015 10 10 Total net development for the accident years presented above $ 125 $ 69 $ 125 Adjustment for development on a discounted basis 1 (4 ) 1 Total net development for accident years prior to 2007 13 15 24 Total $ 139 $ 80 $ 150 (1) Data presented for these calendar years is required supplemental information, which is unaudited.
International [Member]
Net Incurred Claim and Claim Adjustment Expense [Line Items]
Net prior year claim and allocated claim adjustment expense reserve development	The following table presents further detail of the development recorded for the International segment. Years ended December 31 (In millions) 2016 2015 2014 Pretax (favorable) unfavorable development: Medical Professional Liability $ (5 ) $ (9 ) $ (7 ) Other Professional Liability 12 (16 ) (26 ) Liability (30 ) (17 ) (13 ) Property & Marine (34 ) (29 ) (4 ) Other (1 ) 17 (9 ) Total pretax (favorable) unfavorable development $ (58 ) $ (54 ) $ (59 )
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Table Text Block]	The table below provides the composition of the net liability for unpaid claim and claim adjustment expenses for the International segment. As of December 31 (In millions) 2016 Net Claim and claim adjustment expenses: International excluding Hardy $ 881 Hardy 320 Total net liability for claim and claim adjustment expenses $ 1,201
International Excluding Hardy [Member] [Domain]
Net Incurred Claim and Claim Adjustment Expense [Line Items]
Short-Duration Contracts Net Incurred Claims and Allocated Claim Adjustment Expenses [Table Text Block]	Cumulative Net Incurred Claim and Allocated Claim Adjustment Expenses are presented in the following table. As of December 31 Calendar Year As of December 31, 2016 (In millions, except reported claims data) 2007 (1) 2008 (1) 2009 (1) 2010 (1) 2011 (1) 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 IBNR Cumulative Number of Claims Accident Year 2007 $ 204 $ 219 $ 213 $ 194 $ 181 $ 172 $ 164 $ 162 $ 160 $ 159 $ 4 27,149 2008 223 226 214 207 207 200 209 210 207 7 25,119 2009 249 245 247 247 234 231 222 213 13 21,362 2010 226 223 217 211 203 196 190 18 22,877 2011 259 260 253 233 223 216 14 25,361 2012 259 266 252 245 244 34 25,306 2013 281 282 275 256 56 23,999 2014 269 284 284 82 24,859 2015 282 297 107 22,873 2016 276 149 15,564 Total $ 2,342 $ 484
Short-Duration Contracts Net Cumulative Paid Claim Adjustment Expenses Reconciliation of Total Liability for Unpaid Claim and Claim Adjustment Expense [Table Text Block]	Cumulative Net Paid Claims and Allocated Claim Adjustment Expenses are presented in the following table. As of December 31 Calendar Year (In millions) 2007 (1) 2008 (1) 2009 (1) 2010 (1) 2011 (1) 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 Accident Year 2007 $ 31 $ 99 $ 112 $ 124 $ 133 $ 140 $ 144 $ 148 $ 150 $ 152 2008 34 84 126 135 143 151 165 172 190 2009 38 90 119 134 149 159 170 181 2010 47 93 115 130 143 151 160 2011 44 111 133 146 159 171 2012 42 109 142 161 176 2013 49 109 135 152 2014 51 119 145 2015 55 130 2016 64 Total $ 1,521 Net liability for unpaid claim and allocated claim adjustment expenses for the accident years presented $ 821 Net liability for unpaid claim and claim adjustment expenses for accident years prior to 2007 38 Liability for unallocated claim adjustment expenses for accident years presented 22 Total net liability for unpaid claim and claim adjustment expenses $ 881
Short-Duration Contracts Reserve Development [Table Text Block]	Net strengthening or (releases) of prior accident year reserves is presented in the following table. For the years ended December 31 Calendar Year (In millions) 2008 (1) 2009 (1) 2010 (1) 2011 (1) 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 Total (2) Accident Year 2007 $ 15 $ (6 ) $ (19 ) $ (13 ) $ (9 ) $ (8 ) $ (2 ) $ (2 ) $ (1 ) $ (45 ) 2008 3 (12 ) (7 ) — (7 ) 9 1 (3 ) (16 ) 2009 (4 ) 2 — (13 ) (3 ) (9 ) (9 ) (36 ) 2010 (3 ) (6 ) (6 ) (8 ) (7 ) (6 ) (36 ) 2011 1 (7 ) (20 ) (10 ) (7 ) (43 ) 2012 7 (14 ) (7 ) (1 ) (15 ) 2013 1 (7 ) (19 ) (25 ) 2014 15 — 15 2015 15 15 (1) Data presented for these calendar years is required supplemental information, which is unaudited. (2) The amounts included in the loss reserve development tables above are presented at the year-end 2016 foreign currency exchange rates for all periods presented to remove the effects of foreign currency exchange rate fluctuations between calendar years. The amounts included within the table on page 102 presenting the detail of the development recorded within the International segment include the impact of fluctuations in foreign currency exchange rates.
Hardy [Member]
Net Incurred Claim and Claim Adjustment Expense [Line Items]
Short-Duration Contracts Net Incurred Claims and Allocated Claim Adjustment Expenses [Table Text Block]	Cumulative Net Incurred Claim and Allocated Claim Adjustment Expenses are presented in the following table. As of December 31 Calendar Year As of December 31, 2016 (In millions, except reported claims data) Net Claim and Allocated Claim Adjustment Expense Reserves at Acquisition Net Incurred Claim and Allocated Claim Adjustment Expenses in 2012 (1)(2) Total Acquired Net Claim and Allocated Claim Adjustment Expense Reserves and 2012 Incurreds 2013 (1) 2014 (1) 2015 (1) 2016 IBNR Cumulative Number of Claims Accident Year 2007 $ 5 $ 7 $ 12 $ 11 $ 16 $ 10 $ 15 $ — 4,249 2008 18 (4 ) 14 11 12 13 13 — 4,234 2009 11 1 12 6 (4 ) 1 (2 ) — 3,840 2010 46 (10 ) 36 46 50 44 50 — 4,495 2011 121 — 121 130 130 134 132 (2 ) 6,193 2012 33 69 102 102 110 117 110 (1 ) 6,758 2013 127 144 136 137 — 7,392 2014 182 180 174 7 7,656 2015 187 176 18 7,669 2016 225 101 5,274 Total $ 1,030 $ 123
Short-Duration Contracts Net Cumulative Paid Claim Adjustment Expenses Reconciliation of Total Liability for Unpaid Claim and Claim Adjustment Expense [Table Text Block]	Cumulative Net Paid Claims and Allocated Claim Adjustment Expenses are presented in the following table. As of December 31 Calendar Year (In millions) 2012 (1)(2) 2013 (1) 2014 (1) 2015 (1) 2016 Accident Year 2007 $ 3 $ 14 $ 14 $ 14 $ 14 2008 3 14 10 10 11 2009 1 (2 ) (4 ) (4 ) (4 ) 2010 19 34 41 43 45 2011 29 80 119 123 127 2012 14 78 98 107 104 2013 37 100 119 125 2014 55 121 139 2015 29 97 2016 62 Total $ 720 Net liability for unpaid claim and allocated claim adjustment expenses for the accident years presented $ 310 Net liability for unpaid claim and claim adjustment expenses for accident years prior to 2007 3 Liability for unallocated claim adjustment expenses for accident years presented 7 Total net liability for unpaid claim and claim adjustment expenses $ 320
Short-Duration Contracts Reserve Development [Table Text Block]	Net strengthening or (releases) of prior accident year reserves is presented in the following table. For the years ended December 31 Calendar Year (In millions) 2012 (1)(2) 2013 (1) 2014 (1) 2015 (1) 2016 Total (3) Accident Year 2007 $ 7 $ (1 ) $ 5 $ (6 ) $ 5 $ 10 2008 (4 ) (3 ) 1 1 — (5 ) 2009 1 (6 ) (10 ) 5 (3 ) (13 ) 2010 (10 ) 10 4 (6 ) 6 4 2011 — 9 — 4 (2 ) 11 2012 — 8 7 (7 ) 8 2013 17 (8 ) 1 10 2014 (2 ) (6 ) (8 ) 2015 (11 ) (11 ) (1) Data presented for these calendar years is required supplemental information, which is unaudited. (2) Data presented for this calendar year is post-acquisition of Hardy. (3) The amounts included in the loss reserve development tables above are presented at the year-end 2016 foreign currency exchange rates for all periods presented to remove the effects of foreign currency exchange rate fluctuations between calendar years. The amounts included within the table on page 102 presenting the detail of the development recorded within the International segment include the impact of fluctuations in foreign currency exchange rates.
CNAF Consolidated [Member]
Net Incurred Claim and Claim Adjustment Expense [Line Items]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Table Text Block]	The table below reconciles the net liability for unpaid claim and claim adjustment expenses for the property and casualty segments to the amount presented in the Consolidated Balance Sheets. As of December 31 (In millions) 2016 Net liability for unpaid claim and claim adjustment expenses Specialty $ 5,404 Commercial 8,305 International 1,201 Corporate & Other Non-Core 230 Life & Group Non-Core (1) 3,109 Total net claim and claim adjustment expenses 18,249 Reinsurance receivables (2) Specialty 745 Commercial 589 International 127 Corporate & Other Non-Core 2,384 Life & Group Non-Core 249 Total reinsurance receivables 4,094 Total gross liability for unpaid claim and claim adjustment expenses $ 22,343 (1) The Life & Group Non-Core segment amount is primarily related to long term care claim reserves, but does include amounts related to unfunded structured settlements arising from short duration contracts. Long term care policies are long duration contracts. (2) Reinsurance receivables presented do not include reinsurance receivables related to paid losses.
Short-duration Insurance Contracts, Schedule of Historical Claims Duration [Table Text Block]	The table below presents information about average historical claims duration as of December 31, 2016 and is presented as required supplementary information, which is unaudited. Average Annual Percentage Payout of Ultimate Net Incurred Claim and Allocated Claim Adjustment Expenses in Year: 1 2 3 4 5 6 7 8 9 10 Total Specialty Medical Professional Liability 3.1 % 18.2 % 22.3 % 19.6 % 12.7 % 8.0 % 5.0 % 4.8 % 3.7 % 0.3 % 97.7 % Other Professional Liability and Management Liability 5.7 % 20.6 % 21.0 % 17.0 % 10.0 % 6.3 % 5.6 % 3.8 % 1.9 % 3.2 % 95.1 % Surety (1) 23.4 % 32.8 % 20.2 % 8.9 % 3.7 % 1.5 % (0.7 )% 2.0 % 1.0 % 2.0 % 94.8 % Commercial Commercial Auto 27.2 % 23.1 % 18.3 % 13.9 % 9.1 % 3.9 % 1.3 % 0.2 % 0.3 % 0.3 % 97.6 % General Liability 5.0 % 16.3 % 20.5 % 20.1 % 15.3 % 8.0 % 4.2 % 2.7 % 1.1 % 1.3 % 94.5 % Workers' Compensation 13.5 % 21.4 % 14.6 % 10.5 % 7.5 % 5.7 % 4.6 % 3.0 % 2.1 % 0.3 % 83.2 % International International - Excluding Hardy 19.5 % 27.4 % 12.1 % 6.8 % 5.9 % 4.5 % 4.8 % 3.7 % 5.0 % 1.3 % 91.0 % International - Hardy (2) 25.7 % 40.9 % 12.1 % 4.4 % 83.1 % (1) Due to the nature of the Surety business, average annual percentage payout of ultimate net incurred claim and allocated claim adjustment expenses has been calculated using only the payouts of mature accident years presented in the loss reserve development tables. (2) Average historical claims duration for Hardy is presented prospectively beginning with the first full year subsequent to acquisition, 2013.
Impact of loss portfolio transfer on the consolidated statement of operations	The following table presents the impact of the Loss Portfolio Transfer on the Consolidated Statements of Operations. Years ended December 31 (In millions) 2016 2015 2014 Net A&EP adverse development before consideration of LPT $ 200 $ 150 $ — Retroactive reinsurance benefit recognized (107 ) (85 ) (13 ) Pretax impact of A&EP reserve development and the LPT $ 93 $ 65 $ (13 )

Reinsurance (Tables)

Reinsurance (Tables)	12 Months Ended
	Dec. 31, 2016
Reinsurance Disclosures [Abstract]
Components of Reinsurance Receivables	The following table presents the amounts receivable from reinsurers. December 31 (In millions) 2016 2015 Reinsurance receivables related to insurance reserves: Ceded claim and claim adjustment expenses $ 4,094 $ 4,087 Ceded future policy benefits 212 207 Reinsurance receivables related to paid losses 147 197 Reinsurance receivables 4,453 4,491 Allowance for uncollectible reinsurance (37 ) (38 ) Reinsurance receivables, net of allowance for uncollectible reinsurance $ 4,416 $ 4,453
Components of Earned and Written Premiums	The effects of reinsurance on earned premiums and written premiums are presented in the following tables. (In millions) Direct Assumed Ceded Net Assumed/ Net % 2016 Earned Premiums Property and casualty $ 10,400 $ 258 $ 4,270 $ 6,388 4.0 % Long term care 486 50 — 536 9.3 % Total earned premiums $ 10,886 $ 308 $ 4,270 $ 6,924 4.4 % 2015 Earned Premiums Property and casualty $ 9,853 $ 274 $ 3,754 $ 6,373 4.3 % Long term care 498 50 — 548 9.1 % Total earned premiums $ 10,351 $ 324 $ 3,754 $ 6,921 4.7 % 2014 Earned Premiums Property and casualty $ 9,452 $ 277 $ 3,073 $ 6,656 4.2 % Long term care 508 48 — 556 8.6 % Total earned premiums $ 9,960 $ 325 $ 3,073 $ 7,212 4.5 % (In millions) Direct Assumed Ceded Net Assumed/ Net % 2016 Written Premiums Property and casualty $ 10,451 $ 245 $ 4,255 $ 6,441 3.8 % Long term care 495 52 — 547 9.5 % Total written premiums $ 10,946 $ 297 $ 4,255 $ 6,988 4.3 % 2015 Written Premiums Property and casualty $ 9,852 $ 270 $ 3,702 $ 6,420 4.2 % Long term care 493 49 — 542 9.0 % Total written premiums $ 10,345 $ 319 $ 3,702 $ 6,962 4.6 % 2014 Written Premiums Property and casualty $ 9,283 $ 276 $ 3,024 $ 6,535 4.2 % Long term care 504 49 — 553 8.9 % Total written premiums $ 9,787 $ 325 $ 3,024 $ 7,088 4.6 %

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2016
Debt Disclosure [Abstract]
Schedule of debt instruments	Debt is composed of the following obligations. December 31 (In millions) 2016 2015 Short term debt: Senior notes of CNAF, 6.500%, face amount of $350, due August 15, 2016 $ — $ 350 Long term debt: Senior notes of CNAF: 6.950%, face amount of $150, due January 15, 2018 150 150 7.350%, face amount of $350, due November 15, 2019 349 349 5.875%, face amount of $500, due August 15, 2020 498 497 5.750%, face amount of $400, due August 15, 2021 398 397 3.950%, face amount of $550, due May 15, 2024 546 546 4.500%, face amount of $500, due March 1, 2026 498 — Debenture of CNAF, 7.250%, face amount of $243, due November 15, 2023 241 241 Subordinated variable rate debt of Hardy, face amount of $30, due September 15, 2036 30 30 Total long term debt 2,710 2,210 Total debt $ 2,710 $ 2,560
Maturity of debt	The combined aggregate maturities for debt as of December 31, 2016 are presented in the following table. (In millions) 2017 $ — 2018 150 2019 350 2020 500 2021 400 Thereafter 1,323 Less discount (13 ) Total $ 2,710

Benefit Plans (Tables)

Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2016
Compensation and Retirement Disclosure [Abstract]
Funded status	The following table presents a reconciliation of benefit obligations and plan assets. Pension Benefits Postretirement Benefits (In millions) 2016 2015 2016 2015 Benefit obligation as of January 1 $ 2,821 $ 3,019 $ 23 $ 29 Changes in benefit obligation: Service cost — 4 — — Interest cost 113 112 — 1 Participants' contributions — — 4 4 Plan amendments — (55 ) — — Actuarial (gain) loss 68 (79 ) (6 ) (3 ) Benefits paid (173 ) (173 ) (7 ) (8 ) Foreign currency translation and other (14 ) (7 ) 1 — Settlement through group annuity purchase (86 ) — — — Benefit obligation as of December 31 2,729 2,821 15 23 Fair value of plan assets as of January 1 2,267 2,456 — — Change in plan assets: Actual return on plan assets 193 (18 ) — — Company contributions 9 10 3 4 Participants' contributions — — 4 4 Benefits paid (173 ) (173 ) (7 ) (8 ) Foreign currency translation and other (15 ) (8 ) — — Settlement through group annuity purchase (88 ) — — — Fair value of plan assets as of December 31 2,193 2,267 — — Funded status $ (536 ) $ (554 ) $ (15 ) $ (23 ) Amounts recognized on the Consolidated Balance Sheets as of December 31: Other assets $ 4 $ 12 $ — $ — Other liabilities (540 ) (566 ) (15 ) (23 ) Net amount recognized $ (536 ) $ (554 ) $ (15 ) $ (23 ) Amounts recognized in Accumulated other comprehensive income, not yet recognized in net periodic cost (benefit): Prior service credit $ — $ — $ (4 ) $ (6 ) Net actuarial loss 999 999 (3 ) 3 Net amount recognized $ 999 $ 999 $ (7 ) $ (3 )
Components of net periodic cost (benefit)	The components of net periodic cost (benefit) are presented in the following table. Years ended December 31 (In millions) 2016 2015 2014 Pension cost (benefit) Service cost $ — $ 4 $ 9 Interest cost on projected benefit obligation 113 112 132 Expected return on plan assets (160 ) (174 ) (191 ) Amortization of net actuarial loss 37 34 25 Settlement loss — — 84 Net periodic pension cost (benefit) $ (10 ) $ (24 ) $ 59 Postretirement cost (benefit) Interest cost on projected benefit obligation $ — $ 1 $ 1 Amortization of prior service credit (2 ) (3 ) (10 ) Amortization of net actuarial loss — 1 1 Curtailment gain — — (86 ) Net periodic postretirement cost (benefit) $ (2 ) $ (1 ) $ (94 )
Schedule of amounts recognized in Other comprehensive income	The amounts recognized in Other comprehensive income are presented in the following table. Years ended December 31 (In millions) 2016 2015 2014 Pension and postretirement benefits Amounts arising during the period $ (29 ) $ (111 ) $ (337 ) Curtailment and other — 56 (81 ) Settlement — — 84 Reclassification adjustment relating to prior service credit (2 ) (3 ) (10 ) Reclassification adjustment relating to actuarial loss 37 35 26 Settlement through group annuity purchase (2 ) — — Total increase (decrease) in Other comprehensive income $ 4 $ (23 ) $ (318 )
Schedule of estimated amounts to be recognized from Accumulated other comprehensive income into net periodic cost (benefit) during next fiscal year	The table below presents the estimated amounts to be recognized from AOCI into net periodic cost (benefit) during 2017 . (In millions) Pension Benefits Postretirement Benefits Amortization of prior service credit $ — $ (2 ) Amortization of net actuarial loss 36 — Total estimated amounts to be recognized $ 36 $ (2 )
Actuarial assumptions for benefit obligations and for net cost or benefit	Actuarial assumptions used for the CNA Retirement Plan and CNA Health and Group Benefits Program to determine benefit obligations are presented in the following table. December 31 2016 2015 Pension benefits Discount rate 3.950 % 4.150 % Expected long term rate of return 7.500 7.500 Postretirement benefits Discount rate 2.750 % 2.750 % Actuarial assumptions used for the CNA Retirement Plan and CNA Health and Group Benefits Program to determine net cost or benefit are presented in the following table. Years ended December 31 2016 2015 2014 Pension benefits Discount rate 4.150 % 3.850%/4.000% 4.650 % Expected long term rate of return 7.500 7.500 7.500 Rate of compensation increases N/A 3.920 3.990 Postretirement benefits Discount rate 2.750 % 2.500 % 3.600%/3.100%
Fair value of plan assets measured on a recurring basis	Pension plan assets measured at fair value on a recurring basis as well as cash are presented in the following tables. December 31, 2016 (In millions) Level 1 Level 2 Level 3 Total Assets Fixed maturity securities: Corporate and other bonds $ — $ 500 $ 10 $ 510 States, municipalities and political subdivisions — 63 — 63 Asset-backed: Residential mortgage-backed — 109 — 109 Commercial mortgage-backed — 66 — 66 Other asset-backed — 4 — 4 Total asset-backed — 179 — 179 Total fixed maturity securities — 742 10 752 Equity securities 363 105 — 468 Derivative financial instruments — — — — Short term investments 11 35 — 46 Other assets — 37 — 37 Cash 14 — — 14 Total assets measured at fair value $ 388 $ 919 $ 10 1,317 Total limited partnerships measured at net asset value (1) 876 Total plan assets $ 2,193 December 31, 2015 (In millions) Level 1 Level 2 Level 3 Total Assets Assets Fixed maturity securities: Corporate and other bonds $ — $ 455 $ 10 $ 465 States, municipalities and political subdivisions — 106 — 106 Asset-backed: Residential mortgage-backed — 133 — 133 Commercial mortgage-backed — 69 — 69 Other asset-backed — 11 — 11 Total asset-backed — 213 — 213 Total fixed maturity securities — 774 10 784 Equity securities 336 107 — 443 Derivative financial instruments 1 — — 1 Short term investments 24 28 — 52 Other assets — 52 — 52 Total assets measured at fair value $ 361 $ 961 $ 10 1,332 Total limited partnerships measured at net asset value (1) 935 Total plan assets $ 2,267 (1) In accordance with Subtopic 820-10, certain investments that are measured at fair value using the net asset value per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the statement of financial position.
Reconciliation of level 3 plan assets	The tables below present a reconciliation for all pension plan assets measured at fair value on a recurring basis using significant unobservable inputs (Level 3). Level 3 (In millions) Balance as of January 1, 2016 Actual return on assets still held as of December 31, 2016 Actual return on assets sold during the year ended December 31, 2016 Purchases, sales and settlements Net transfers into (out of) Level 3 Balance as of December 31, 2016 Fixed maturity securities: Corporate and other bonds $ 10 $ — $ — $ — $ — $ 10 Total $ 10 $ — $ — $ — $ — $ 10 Level 3 (In millions) Balance as of January 1, 2015 Actual return on assets still held as of Actual return on assets sold during the year ended December 31, 2015 Purchases, sales and settlements Net transfers into (out of) Level 3 Balance as of December 31, 2015 Fixed maturity securities: Corporate and other bonds $ 15 $ — $ — $ — $ (5 ) $ 10 Total $ 15 $ — $ — $ — $ (5 ) $ 10
Estimated future minimum benefit payments to participants	The table below presents the estimated future minimum benefit payments to participants as of December 31, 2016 . (In millions) Pension Benefits Postretirement Benefits 2017 $ 178 $ 3 2018 178 2 2019 177 2 2020 178 2 2021 178 2 2022-2026 883 3

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Restricted shares, performance-based restricted share units and performance share unit activity	The following table presents activity for non-vested RSUs, performance-based RSUs and performance share units under the Plan in 2016 . Number of Awards Weighted-Average Grant Date Fair Value Balance as of January 1, 2016 735,263 $ 36.53 Awards granted 2,545,624 32.27 Awards vested (371,443 ) 33.33 Awards forfeited, canceled or expired (186,932 ) 32.80 Performance-based adjustment (590,730 ) 33.10 Balance as of December 31, 2016 2,131,782 $ 33.28

Other Intangible Assets (Tables

Other Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2016
Intangible Assets, Gross (Excluding Goodwill) [Abstract]
Schedule of Other Intangible Assets	Other intangible assets are presented in the following table. December 31 2016 2015 (In millions) Economic Useful Life Gross Carrying Amount Accumulated Amortization Gross Carrying Amount Accumulated Amortization Finite-lived intangible assets: Value of business acquired 1 - 4 years $ 48 $ 48 $ 57 $ 57 Trade name 8 years 6 3 7 3 Distribution channel 15 years 10 3 12 3 Total finite-lived intangible assets 64 54 76 63 Indefinite-lived intangible assets: Syndicate capacity 43 52 Agency force 16 16 Total indefinite-lived intangible assets 59 68 Total other intangible assets $ 123 $ 54 $ 144 $ 63

Operating Leases (Tables)

Operating Leases (Tables)	12 Months Ended
	Dec. 31, 2016
Leases, Operating [Abstract]
Future minimum lease payments	The table below presents the expected future minimum lease payments to be made under non-cancelable operating leases as of December 31, 2016 . (In millions) Future Minimum Lease Payments 2017 $ 48 2018 37 2019 30 2020 33 2021 34 Thereafter 244 Total $ 426

Stockholders' Equity and Stat46

Stockholders' Equity and Statutory Accounting Practices (Tables)	12 Months Ended
	Dec. 31, 2016
Stockholders' Equity and Statutory Accounting Practices [Abstract]
Combined statutory capital and surplus and net income (loss)	Combined statutory capital and surplus and statutory net income (loss), determined in accordance with accounting practices prescribed or permitted by insurance and/or other regulatory authorities for the Combined Continental Casualty Companies, are presented in the table below. Statutory Capital and Surplus Statutory Net Income (Loss) December 31 Years ended December 31 (In millions) 2016 (1) 2015 2016 (1) 2015 2014 Combined Continental Casualty Companies $ 10,748 $ 10,723 $ 1,033 $ 1,148 $ 914 (1) Information derived from the statutory-basis financial statements to be filed with insurance regulators.

Accumulated Other Comprehensi47

Accumulated Other Comprehensive Income (Loss) by Component (Tables)	12 Months Ended
	Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss) by Component	The table below displays the changes in Accumulated other comprehensive income (loss) by component. (In millions) Net unrealized gains (losses) on investments with OTTI losses Net unrealized gains (losses) on other investments Pension and postretirement benefits Cumulative foreign currency translation adjustment Total Balance as of December 31, 2015 $ 27 $ 390 $ (648 ) $ (84 ) $ (315 ) Other comprehensive income (loss) before reclassifications 9 290 (22 ) (114 ) 163 Amounts reclassified from accumulated other comprehensive income (loss) net of tax (expense) benefit of $(3), $(16), $12, $- and $(7) 6 38 (23 ) — 21 Other comprehensive income (loss) net of tax (expense) benefit of $(1), $(117), $(3), $- and $(121) 3 252 1 (114 ) 142 Balance as of December 31, 2016 $ 30 $ 642 $ (647 ) $ (198 ) $ (173 ) (In millions) Net unrealized gains (losses) on investments with OTTI losses Net unrealized gains (losses) on other investments Pension and postretirement benefits Cumulative foreign currency translation adjustment Total Balance as of December 31, 2014 $ 36 $ 942 $ (633 ) $ 55 $ 400 Other comprehensive income (loss) before reclassifications (23 ) (595 ) (36 ) (139 ) (793 ) Amounts reclassified from accumulated other comprehensive income (loss) net of tax (expense) benefit of $8, $30, $11, $- and $49 (14 ) (43 ) (21 ) — (78 ) Other comprehensive income (loss) net of tax (expense) benefit of $5, $282, $8, $- and $295 (9 ) (552 ) (15 ) (139 ) (715 ) Balance as of December 31, 2015 $ 27 $ 390 $ (648 ) $ (84 ) $ (315 )

Business Segments (Tables)

Business Segments (Tables)	12 Months Ended
	Dec. 31, 2016
Segment Reporting [Abstract]
Significant components of the Company's continuing operations and selected balance sheet items	The Company's results of continuing operations and selected balance sheet items by segment are presented in the following tables. Year ended December 31, 2016 Specialty Commercial International Life & Group Non-Core Corporate & Other Non-Core (In millions) Eliminations Total Net written premiums $ 2,780 $ 2,841 $ 821 $ 547 $ — $ (1 ) $ 6,988 Operating revenues Net earned premiums $ 2,779 $ 2,804 $ 806 $ 536 $ — $ (1 ) $ 6,924 Net investment income 516 638 51 767 16 — 1,988 Other revenues 362 32 — (2 ) 12 — 404 Total operating revenues 3,657 3,474 857 1,301 28 (1 ) 9,316 Claims, Benefits and Expenses Net incurred claims and benefits 1,467 1,927 492 1,286 98 — 5,270 Policyholders’ dividends 4 9 — — — — 13 Amortization of deferred acquisition costs 591 470 174 — — — 1,235 Other insurance related expenses 301 560 133 132 (3 ) (1 ) 1,122 Other expenses 312 36 24 8 209 — 589 Total claims, benefits and expenses 2,675 3,002 823 1,426 304 (1 ) 8,229 Operating income (loss) before income tax 982 472 34 (125 ) (276 ) — 1,087 Income tax (expense) benefit on operating income (loss) (332 ) (161 ) (13 ) 145 98 — (263 ) Net operating income (loss) 650 311 21 20 (178 ) — 824 Net realized investment gains (losses) 5 4 18 25 (2 ) — 50 Income tax (expense) benefit on net realized investment gains (losses) (2 ) (2 ) (3 ) (9 ) 1 — (15 ) Net realized investment gains (losses), after tax 3 2 15 16 (1 ) — 35 Net income (loss) from continuing operations $ 653 $ 313 $ 36 $ 36 $ (179 ) $ — $ 859 December 31, 2016 (In millions) Reinsurance receivables $ 760 $ 621 $ 131 $ 462 $ 2,479 $ — $ 4,453 Insurance receivables 982 1,021 233 17 2 — 2,255 Deferred acquisition costs 310 214 76 — — — 600 Goodwill 117 — 28 — — — 145 Insurance reserves Claim and claim adjustment expenses 6,149 8,894 1,328 3,358 2,614 — 22,343 Unearned premiums 1,911 1,323 396 132 — — 3,762 Future policy benefits — — — 10,326 — — 10,326 Year ended December 31, 2015 Specialty Commercial International Life & Group Non-Core Corporate & Other Non-Core (In millions) Eliminations Total Net written premiums $ 2,781 $ 2,818 $ 822 $ 542 $ 1 $ (2 ) $ 6,962 Operating revenues Net earned premiums $ 2,782 $ 2,788 $ 804 $ 548 $ 1 $ (2 ) $ 6,921 Net investment income 474 593 52 704 17 — 1,840 Other revenues 356 37 (1 ) 7 11 (3 ) 407 Total operating revenues 3,612 3,418 855 1,259 29 (5 ) 9,168 Claims, Benefits and Expenses Net incurred claims and benefits 1,597 1,814 479 1,421 61 — 5,372 Policyholders’ dividends 4 8 — — — — 12 Amortization of deferred acquisition costs 589 469 168 314 — — 1,540 Other insurance related expenses 278 538 138 142 (1 ) (2 ) 1,093 Other expenses 301 28 12 11 186 (3 ) 535 Total claims, benefits and expenses 2,769 2,857 797 1,888 246 (5 ) 8,552 Operating income (loss) before income tax 843 561 58 (629 ) (217 ) — 616 Income tax (expense) benefit on operating income (loss) (283 ) (192 ) (21 ) 315 80 — (101 ) Net operating income (loss) 560 369 37 (314 ) (137 ) — 515 Net realized investment gains (losses) (33 ) (47 ) 1 (1 ) 13 — (67 ) Income tax (expense) benefit on net realized investment gains (losses) 11 16 — 9 (5 ) — 31 Net realized investment gains (losses), after tax (22 ) (31 ) 1 8 8 — (36 ) Net income (loss) from continuing operations $ 538 $ 338 $ 38 $ (306 ) $ (129 ) $ — $ 479 December 31, 2015 (In millions) Reinsurance receivables $ 724 $ 639 $ 144 $ 497 $ 2,487 $ — $ 4,491 Insurance receivables 890 993 233 11 2 — 2,129 Deferred acquisition costs 307 213 78 — — — 598 Goodwill 117 — 33 — — — 150 Insurance reserves Claim and claim adjustment expenses 6,269 9,183 1,347 3,220 2,644 — 22,663 Unearned premiums 1,839 1,297 415 120 — — 3,671 Future policy benefits — — — 10,152 — — 10,152 Year ended December 31, 2014 Specialty Commercial Life & Group Non-Core Corporate & Other Non-Core (In millions) International Eliminations Total Net written premiums $ 2,839 $ 2,817 $ 880 $ 553 $ 1 $ (2 ) $ 7,088 Operating revenues Net earned premiums $ 2,838 $ 2,906 $ 913 $ 556 $ 1 $ (2 ) $ 7,212 Net investment income 560 723 61 700 23 — 2,067 Other revenues 295 38 — 16 12 (5 ) 356 Total operating revenues 3,693 3,667 974 1,272 36 (7 ) 9,635 Claims, Benefits and Expenses Net incurred claims and benefits 1,627 2,187 488 1,304 (29 ) — 5,577 Policyholders’ dividends 6 8 — — — — 14 Amortization of deferred acquisition costs 592 493 204 28 — — 1,317 Other insurance related expenses 262 487 151 130 1 (2 ) 1,029 Other expenses 254 31 28 30 210 (5 ) 548 Total claims, benefits and expenses 2,741 3,206 871 1,492 182 (7 ) 8,485 Operating income (loss) before income tax 952 461 103 (220 ) (146 ) — 1,150 Income tax (expense) benefit on operating income (loss) (318 ) (154 ) (34 ) 151 54 — (301 ) Net operating income (loss) 634 307 69 (69 ) (92 ) — 849 Net realized investment gains (losses) 15 16 (1 ) 7 20 — 57 Income tax (expense) benefit on net realized investment gains (losses) (5 ) (6 ) 1 — (8 ) — (18 ) Net realized investment gains (losses), after tax 10 10 — 7 12 — 39 Net income (loss) from continuing operations $ 644 $ 317 $ 69 $ (62 ) $ (80 ) $ — $ 888
Revenues by line of business	The following table presents revenue by line of business for each reportable segment. Revenues are comprised of operating revenues and net realized investment gains and losses. Years ended December 31 (In millions) 2016 2015 2014 Specialty Management & Professional Liability $ 2,620 $ 2,617 $ 2,818 Surety 532 502 509 Warranty & Alternative Risks 510 460 381 Specialty revenues 3,662 3,579 3,708 Commercial Middle Market 1,769 1,623 1,631 Small Business 583 616 709 Other Commercial Insurance 1,126 1,132 1,343 Commercial revenues 3,478 3,371 3,683 International Canada 203 214 273 CNA Europe 319 309 335 Hardy 353 333 365 International revenues 875 856 973 Life & Group Non-Core revenues 1,326 1,258 1,279 Corporate & Other Non-Core revenues 26 42 56 Eliminations (1 ) (5 ) (7 ) Total revenues $ 9,366 $ 9,101 $ 9,692

Discontinued Operations (Tables

Discontinued Operations (Tables)	12 Months Ended
	Dec. 31, 2016
Discontinued Operations and Disposal Groups [Abstract]
Results of discontinued operations	The results of discontinued operations reflected in the Consolidated Statements of Operations were as follows: Year ended December 31 (In millions) 2014 Revenues Net earned premiums $ — Net investment income 94 Net realized investment gains 3 Other revenues — Total revenues 97 Claims, Benefits and Expenses Insurance claims and policyholders' benefits 75 Other operating expenses 2 Total claims, benefits and expenses 77 Income before income tax 20 Income tax expense (6 ) Income from operations of discontinued operations, net of income tax 14 Loss on sale, net of income tax benefit of $40 (211 ) Loss from discontinued operations $ (197 )

Quarterly Financial Data (Una50

Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2016
Quarterly Financial Data [Abstract]
Schedule of quarterly financial information	The following tables present unaudited quarterly financial data. 2016 (In millions, except per share data) First Second Third Fourth Full Year Revenues $ 2,195 $ 2,348 $ 2,433 $ 2,390 $ 9,366 Net income (loss) (1) $ 66 $ 209 $ 343 $ 241 $ 859 Basic earnings (loss) per share $ 0.25 $ 0.77 $ 1.27 $ 0.89 $ 3.18 Diluted earnings (loss) per share $ 0.24 $ 0.77 $ 1.26 $ 0.89 $ 3.17 2015 (In millions, except per share data) First Second Third Fourth Full Year Revenues $ 2,352 $ 2,327 $ 2,153 $ 2,269 $ 9,101 Net income (loss) (1) (2) $ 233 $ 138 $ 178 $ (70 ) $ 479 Basic earnings (loss) per share $ 0.86 $ 0.51 $ 0.66 $ (0.26 ) $ 1.77 Diluted earnings (loss) per share $ 0.86 $ 0.51 $ 0.66 $ (0.26 ) $ 1.77 (1) Net income (loss) in the first quarter of 2016 and the second quarter of 2015 included a charge related to the application of retroactive reinsurance accounting to adverse reserve development ceded under the 2010 A&EP Loss Portfolio Transfer in our Corporate & Other Non-Core segment. (2) Net income (loss) in the fourth quarter of 2015 included a charge related to recognition of a premium deficiency in our long term care business.

Organization Review (Tables)

Organization Review (Tables)	12 Months Ended
	Dec. 31, 2016
Restructuring and Related Activities [Abstract]
Restructuring and Related Costs [Table Text Block]	The costs by reportable segment for the year ended December 31, 2016 , are presented in the following table. Year ended December 31 (In millions) 2016 Specialty $ 4 Commercial 14 International — Life & Group Non-Core 1 Corporate & Other Non-Core — Total organization review costs $ 19

Schedule II. Condensed Financ52

Schedule II. Condensed Financial Information of Registrant (Parent Company) Schedule II. Condensed Financial Information of Registrant (Parent Company)	12 Months Ended
	Dec. 31, 2016
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Condensed Statement of Comprehensive Income [Table Text Block]	CNA Financial Corporation Statements of Operations and Comprehensive Income (Loss) Years ended December 31 (In millions) 2016 2015 2014 Revenues Net investment income $ 3 $ 1 $ 1 Net realized investment (losses) gains (7 ) 5 4 Total revenues (4 ) 6 5 Expenses Administrative and general 1 1 5 Interest 155 154 182 Total expenses 156 155 187 Loss from operations before income taxes and equity in net income of subsidiaries (160 ) (149 ) (182 ) Income tax benefit 41 34 35 Loss before equity in net income of subsidiaries (119 ) (115 ) (147 ) Equity in net income of subsidiaries 978 594 838 Net income 859 479 691 Equity in other comprehensive income of subsidiaries 142 (715 ) (42 ) Total Comprehensive Income (Loss) $ 1,001 $ (236 ) $ 649
Condensed Balance Sheet [Table Text Block]	CNA Financial Corporation Balance Sheets December 31 (In millions, except share data) 2016 2015 Assets Investment in subsidiaries $ 14,202 $ 13,851 Cash 1 4 Short term investments 487 478 Amounts due from affiliates 6 — Other assets 1 1 Total assets $ 14,697 $ 14,334 Liabilities Short term debt $ — $ 350 Long term debt 2,680 2,180 Other liabilities 48 48 Total liabilities 2,728 2,578 Stockholders' Equity Common stock ($2.50 par value; 500,000,000 shares authorized; 273,040,243 shares issued; 270,495,998 and 270,274,361 shares outstanding) 683 683 Additional paid-in capital 2,173 2,153 Retained earnings 9,359 9,313 Accumulated other comprehensive income (173 ) (315 ) Treasury stock (2,544,245 and 2,765,882 shares), at cost (73 ) (78 ) Total stockholders' equity 11,969 11,756 Total liabilities and stockholders' equity $ 14,697 $ 14,334
Condensed Cash Flow Statement [Table Text Block]	CNA Financial Corporation Statements of Cash Flows Years ended December 31 (In millions) 2016 2015 2014 Cash Flows from Operating Activities Net income $ 859 $ 479 $ 691 Adjustments to reconcile net income to net cash flows provided by operating activities: Equity in net income of subsidiaries (978 ) (594 ) (838 ) Dividends received from subsidiaries 765 900 650 Net realized investment losses (gains) 7 (5 ) (4 ) Other, net 21 4 14 Total adjustments (185 ) 305 (178 ) Net cash flows provided by operating activities 674 784 513 Cash Flows from Investing Activities Change in short term investments (9 ) 21 6 Capital contributions to subsidiaries — — (10 ) Other, net 4 7 5 Net cash flows (used) provided by investing activities (5 ) 28 1 Cash Flows from Financing Activities Dividends paid to common stockholders (813 ) (811 ) (541 ) Proceeds from the issuance of debt 498 — 546 Repayment of debt (358 ) — (549 ) Stock options exercised — 1 5 Other, net 1 1 25 Net cash flows used by financing activities (672 ) (809 ) (514 ) Net change in cash (3 ) 3 — Cash, beginning of year 4 1 1 Cash, end of year $ 1 $ 4 $ 1

Summary of Significant Accoun53

Summary of Significant Accounting Policies (Narrative) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Loss on reinsurance transaction			$ 34
Anticipated amounts due from insureds related to losses under deductible policies	$ 1,200	$ 1,200
Structured Settlement Annuities, Interest Rate, Low End	5.50%	5.50%
Structured Settlement Annuities, Interest Rates, High End	8.00%	8.00%
Discounted reserves for unfunded structured settlements	$ 544	$ 560
Discounted reserves for unfunded structure settlements, discount amount	841	880
Amount of interest recognized on the discounted reserves of unfunded structured settlements	$ 42	$ 42	43
Interest rates at which workers' compensation lifetime claim reserves are discounted at	3.50%	3.50%
Workers' Compensation Liability	$ 371	$ 396
Discounted reserves for workers’ compensation lifetime claim reserves, discount amount	202	218
Amount of interest accretion recognized on the discounted reserves of workers’ compensation lifetime claim reserves	$ 17	$ 20	22
Minimum interest rate used to discount long term care claim reserves	4.50%	4.50%
Maximum interest rate used to discount long term care claim reserves	6.80%	6.80%
Discounted reserves for long term care claim reserves	$ 2,200	$ 2,200
Discounted reserves for long term care claim reserves, discount amount	$ 529	435
Long term care premium deficiency		296
Write off of deferred acquisition cost asset due to long term care premium deficiency		289
Adjustment to Active life reserves due to premium deficiency		7
Minimum interest rate used to calculate reserves for long term care products	6.60%
Maximum interest rate used to calculate reserves for long term care products	7.00%
Liability balance for guaranty fund	$ 125	129
Percentage of billed receivables compared to total reinsurance receivables	3% or less
Deposit assets	$ 3	3
Deposit liabilities	6	8
Loss on life settlement contracts, held for sale	10
Investments in life settlement contracts	58	74
Increase in fair value recognized on life settlement contracts	7	1	8
Gain recognized on matured life settlement contracts	8	24	25
Decreased Net Investment Income and amortized cost of fixed maturity securities due to a change in estimate effected by a change in accounting principle		39
Decreased Net Investment Income and amortized cost of fixed maturity securities due to a change in estimate effected by a change in accounting principle relating to 2014 and prior		$ 22
Decrease of Basic and Diluted Earnings per Share due to change in estimate effected by a change in accounting principle		$ 0.09
Decrease in shadow adjustment, net of tax	97	$ 177
Reduction of net unrealized gains on investments included in AOCI due to shadow adjustments	1,014	1,111
Foreign currency transaction gain (loss), before tax	$ (9)	$ (11)	$ (25)
Weighted average number diluted shares outstanding adjustment	678	534	675
Antidilutive securities excluded from computation of earnings per share, amount	102	106	170
Interest paid, net	$ 157	$ 152	$ 179
Income taxes paid	170	310	$ 313
Cumulative Effect of New Accounting Principle in Period of Adoption on Long Term Debt		(2)
Cumulative Effect of New Accounting Principle in Period of Adoption on Other Assets		(2)
Other Invested Assets Overseas Deposit	31	27
Limited partnership investments	$ 2,371	2,548
Furniture and Fixtures [Member]
Property, Plant and Equipment, Useful Life	7 years
Office Equipment [Member]
Property, Plant and Equipment, Useful Life	5 years
Building and Building Improvements [Member]
Property, Plant and Equipment, Useful Life	50 years
Minimum [Member]
Requisite service period for stock- based compensation expense	3 years
Minimum [Member] | Computer Software, Intangible Asset [Member]
Property, Plant and Equipment, Useful Life	3 years
Maximum [Member]
Requisite service period for stock- based compensation expense	4 years
Maximum [Member] | Computer Software, Intangible Asset [Member]
Property, Plant and Equipment, Useful Life	10 years
Pension Plans, Defined Benefit [Member]
Limited partnership investments	$ 876	$ 935

Summary of Significant Accoun54

Summary of Significant Accounting Policies (Life Settlement Contracts) (Details) $ in Millions	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Life Settlement Contracts, Fair Value Method, Number of Contracts, Fiscal Year Maturity [Abstract]
Life settlement contracts, fair value method, number of contracts, maturing in next twelve months	63
Life settlement contracts, fair value method, number of contracts, maturing in year two	55
Life settlement contracts, fair value method, number of contracts, maturing in year three	49
Life settlement contracts, fair value method, number of contracts, maturing in year four	43
Life settlement contracts, fair value method, number of contracts, maturing in year five	36
Life settlement contracts, fair value method, number of contracts, maturing after year five	280
Life settlement contracts, fair value method, number of contracts	526
Life settlement contracts, fair value, maturing in next twelve months	$ 10
Life settlement contracts, fair value, maturing in year two	8
Life settlement contracts, fair value, maturing in year three	7
Life settlement contracts, fair value, maturing in year four	6
Life settlement contracts, fair value, maturing in year five	4
Life settlement contracts, fair value, maturing after year five	23
Life settlement contracts, fair value	58	$ 74
Life settlement contracts, fair value method, face value, maturing in next twelve months	34
Life settlement contracts, fair value method, face value, maturing in year two	30
Life settlement contracts, fair value method, face value, maturing in year three	26
Life settlement contracts, fair value method, face value, maturing in year four	23
Life settlement contracts, fair value method, face value, maturing in year five	19
Life settlement contracts, fair value method, face value, maturing after year five	153
Life settlement contracts, fair value method, face value	$ 285

Investments (Narrative) (Detail

Investments (Narrative) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Investments [Abstract]
Non-income producing fixed maturity securities	$ 0	$ 54
Investments that exceed ten percent of stockholders' equity	0	0
Limited partnership investments	2,371	2,548
Undistributed earnings of limited partnership investments	$ 523	$ 687
Percentage of limited partnerships reported on a current basis	60.00%
Percentage of limited partnerships reported on a one month lag	18.00%
Percentage of limited partnerships employing hedge fund strategies focused on fixed income and equity investments	68.00%	70.00%
Limited partnerships invested in private debt and equity	27.00%	26.00%
Percentage of equity related limited partnership hedge fund strategies	55.00%
Percentage of multistrategy approach limited partnership hedge fund strategies	26.00%
Percentage of distressed investments limited partnership hedge fund strategies	17.00%
Percentage of fixed income limited partnership hedge fund strategies	2.00%
Carrying value of ten largest limited partnerships	$ 1,168	$ 1,221
Carrying value of limited partnerships as percentage of aggregate partnership equity	4.00%	3.00%
Income As Percentage Of Change In Partnership Equity For All Limited Partnerships	4.00%	3.00%	4.00%
Derivative, Collateral, Right to Reclaim Cash	$ 0	$ 0
Derivative, Collateral, Obligation to Return Cash	0	0
Derivative, Notional Amount	174	179
Derivative Liability, Fair Value, Gross Liability	(3)	(5)
Commercial mortgage loans past due or in non-accrual status	0	0
Valuation allowances recorded on commercial mortgage loans	0	0
Future capital call commitments for limited partnership investments	380
Mortgage loan commitments	20
Commitments to purchase or fund privately placed debt securities	130
Commitments to sell various privately placed debt securities	121
Carrying value of securities deposited under requirements of regulatory authorities	2,300	2,800
Cash and securities deposited as collateral for letters of credit	514	364
Carrying value of assets deposited to secure reinsurance and third party obligations	$ 261	$ 263

Investments (Net investment inc

Investments (Net investment income) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Net Investment Income [Line Items]
Gross investment income	$ 2,047	$ 1,903	$ 2,125
Investment expense	(59)	(63)	(58)
Net Investment Income	1,988	1,840	2,067
Fixed maturity securities [Member]
Net Investment Income [Line Items]
Gross investment income	1,819	1,751	1,803
Total equity securities available-for-sale [Member]
Net Investment Income [Line Items]
Gross investment income	10	12	12
Limited partnership investments [Member]
Net Investment Income [Line Items]
Gross investment income	155	92	263
Mortgage loans [Member]
Net Investment Income [Line Items]
Gross investment income	41	33	31
Short term investments [Member]
Net Investment Income [Line Items]
Gross investment income	8	6	3
Trading portfolio [Member]
Net Investment Income [Line Items]
Gross investment income	10	8	10
Other [Member]
Net Investment Income [Line Items]
Gross investment income	$ 4	$ 1	$ 3

Investments (Net realized inves

Investments (Net realized investment gains (losses)) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Net realized investment gains (losses)	$ 50	$ (67)	$ 57
Fixed maturity securities [Member]
Gross realized gains	204	131	170
Gross realized losses	(138)	(197)	(129)
Net realized investment gains (losses)	66	(66)	41
Total equity securities available-for-sale [Member]
Gross realized gains	5	2	8
Gross realized losses	(10)	(25)	(7)
Net realized investment gains (losses)	(5)	(23)	1
Derivative [Member]
Net realized investment gains (losses)	(2)	10	(1)
Short term investments and other [Member]
Net realized investment gains (losses)	$ (9)	$ 12	$ 16

Investments (Net change in unre

Investments (Net change in unrealized gains (losses) on investments) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Net change in unrealized gains (losses) on investments	$ 224	$ (1,119)	$ 1,517
Fixed maturity securities [Member]
Net change in unrealized gains (losses) on investments	225	(1,114)	1,511
Total equity securities available-for-sale [Member]
Net change in unrealized gains (losses) on investments	(2)	(6)	6
Other [Member]
Net change in unrealized gains (losses) on investments	$ 1	$ 1	$ 0

Investments (Components of othe

Investments (Components of other-than-temporary impairment losses recognized in earnings) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Other-than-temporary impairment losses recognized in earnings	$ 81	$ 156	$ 77
Corporate and other bonds [Member]
Other-than-temporary impairment losses recognized in earnings	59	104	18
States, municipalities and political subdivisions [Member]
Other-than-temporary impairment losses recognized in earnings	0	18	46
Residential mortgage-backed [Member]
Other-than-temporary impairment losses recognized in earnings	10	8	5
Other asset-backed [Member]
Other-than-temporary impairment losses recognized in earnings	3	1	1
Total asset-backed [Member]
Other-than-temporary impairment losses recognized in earnings	13	9	6
Total fixed maturity securities available-for-sale [Member]
Other-than-temporary impairment losses recognized in earnings	72	131	70
Common stock [Member]
Other-than-temporary impairment losses recognized in earnings	$ 9	$ 25	$ 7

Investments (Summary of fixed m

Investments (Summary of fixed maturity and equity securities) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Cost or Amortized Cost	$ 38,467	$ 37,444
Gross Unrealized Gain	2,744	2,717
Gross Unrealized Loss	196	392
Estimated fair value	41,015	39,769
Corporate and other bonds [Member]
Cost or Amortized Cost	17,711	17,080
Gross Unrealized Gain	1,323	1,019
Gross Unrealized Loss	76	342
Estimated fair value	18,958	17,757
Unrealized OTTI Losses (Gains)	(1)	0
States, municipalities and political subdivisions [Member]
Cost or Amortized Cost	12,060	11,729
Gross Unrealized Gain	1,213	1,453
Gross Unrealized Loss	33	8
Estimated fair value	13,240	13,174
Unrealized OTTI Losses (Gains)	(16)	(4)
Residential mortgage-backed [Member]
Cost or Amortized Cost	5,004	4,935
Gross Unrealized Gain	120	154
Gross Unrealized Loss	51	17
Estimated fair value	5,073	5,072
Unrealized OTTI Losses (Gains)	(28)	(37)
Commercial mortgage-backed [Member]
Cost or Amortized Cost	2,016	2,154
Gross Unrealized Gain	48	55
Gross Unrealized Loss	24	12
Estimated fair value	2,040	2,197
Unrealized OTTI Losses (Gains)	0	0
Other asset-backed [Member]
Cost or Amortized Cost	1,022	923
Gross Unrealized Gain	8	6
Gross Unrealized Loss	5	8
Estimated fair value	1,025	921
Unrealized OTTI Losses (Gains)	0	0
Total asset-backed [Member]
Cost or Amortized Cost	8,042	8,012
Gross Unrealized Gain	176	215
Gross Unrealized Loss	80	37
Estimated fair value	8,138	8,190
Unrealized OTTI Losses (Gains)	(28)	(37)
U.S. Treasury and obligations of government-sponsored enterprises [Member]
Cost or Amortized Cost	83	62
Gross Unrealized Gain	10	5
Gross Unrealized Loss	0	0
Estimated fair value	93	67
Unrealized OTTI Losses (Gains)	0	0
Foreign Government Debt Securities [Member]
Cost or Amortized Cost	435	334
Gross Unrealized Gain	13	13
Gross Unrealized Loss	3	1
Estimated fair value	445	346
Unrealized OTTI Losses (Gains)	0	0
Redeemable preferred stock [Member]
Cost or Amortized Cost	18	33
Gross Unrealized Gain	1	2
Gross Unrealized Loss	0	0
Estimated fair value	19	35
Unrealized OTTI Losses (Gains)	0	0
Total fixed maturity securities available-for-sale [Member]
Cost or Amortized Cost	38,349	37,250
Gross Unrealized Gain	2,736	2,707
Gross Unrealized Loss	192	388
Estimated fair value	40,893	39,569
Unrealized OTTI Losses (Gains)	(45)	(41)
Fixed Maturities [Member]
Cost or Amortized Cost, Trading Securities	12	3
Estimated Fair Value, Trading Securities	12	3
Common stock [Member]
Cost or Amortized Cost	13	46
Gross Unrealized Gain	6	3
Gross Unrealized Loss	0	1
Estimated fair value	19	48
Preferred stock [Member]
Cost or Amortized Cost	93	145
Gross Unrealized Gain	2	7
Gross Unrealized Loss	4	3
Estimated fair value	91	149
Total equity securities available-for-sale [Member]
Cost or Amortized Cost	106	191
Gross Unrealized Gain	8	10
Gross Unrealized Loss	4	4
Estimated fair value	$ 110	$ 197

Investments (Securities in a gr

Investments (Securities in a gross unrealized loss position) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value, Less than 12 Months	$ 6,989	$ 7,464
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	167	342
Estimated Fair Value, 12 Months or Longer	584	502
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	29	50
Estimated Fair Value, Total	7,573	7,966
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	196	392
Corporate and other bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value, Less than 12 Months	2,615	4,882
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	61	302
Estimated Fair Value, 12 Months or Longer	254	162
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	15	40
Estimated Fair Value, Total	2,869	5,044
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	76	342
States, municipalities and political subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value, Less than 12 Months	959	338
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	32	8
Estimated Fair Value, 12 Months or Longer	23	75
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	1	0
Estimated Fair Value, Total	982	413
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	33	8
Residential mortgage-backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value, Less than 12 Months	2,136	963
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	44	9
Estimated Fair Value, 12 Months or Longer	201	164
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	7	8
Estimated Fair Value, Total	2,337	1,127
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	51	17
Commercial mortgage-backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value, Less than 12 Months	756	652
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	22	10
Estimated Fair Value, 12 Months or Longer	69	96
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	2	2
Estimated Fair Value, Total	825	748
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	24	12
Other asset-backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value, Less than 12 Months	398	552
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	5	8
Estimated Fair Value, 12 Months or Longer	24	5
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Estimated Fair Value, Total	422	557
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	5	8
Total asset-backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value, Less than 12 Months	3,290	2,167
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	71	27
Estimated Fair Value, 12 Months or Longer	294	265
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	9	10
Estimated Fair Value, Total	3,584	2,432
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	80	37
U.S. Treasury and obligations of government-sponsored enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value, Less than 12 Months	5	4
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	0
Estimated Fair Value, 12 Months or Longer	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Estimated Fair Value, Total	5	4
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	0	0
Foreign Government Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value, Less than 12 Months	108	54
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	3	1
Estimated Fair Value, 12 Months or Longer	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Estimated Fair Value, Total	108	54
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	3	1
Redeemable preferred stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value, Less than 12 Months	0	3
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	0
Estimated Fair Value, 12 Months or Longer	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Estimated Fair Value, Total	0	3
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	0	0
Total fixed maturity securities available-for-sale [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value, Less than 12 Months	6,977	7,448
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	167	338
Estimated Fair Value, 12 Months or Longer	571	502
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	25	50
Estimated Fair Value, Total	7,548	7,950
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	192	388
Common stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value, Less than 12 Months		3
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		1
Estimated Fair Value, 12 Months or Longer		0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		0
Estimated Fair Value, Total		3
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss		1
Preferred stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value, Less than 12 Months	12	13
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	3
Estimated Fair Value, 12 Months or Longer	13	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	4	0
Estimated Fair Value, Total	25	13
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 4	3
Total equity securities available-for-sale [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value, Less than 12 Months		16
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		4
Estimated Fair Value, 12 Months or Longer		0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		0
Estimated Fair Value, Total		16
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss		$ 4

Investments (Activity related t

Investments (Activity related to the pretax fixed maturity credit loss component reflected within retained earnings for securities still held for which a portion of an OTTI loss was recognized in OCI) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Beginning balance of credit losses on fixed maturity securities	$ 53	$ 62	$ 74
Reductions for securities sold during the period	(16)	(9)	(9)
Reductions for securities the Company intends to sell or more likely than not will be required to sell	(1)	0	(3)
Ending balance of credit losses on fixed maturity securities	$ 36	$ 53	$ 62

Investments (Contractual maturi

Investments (Contractual maturity) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Investments [Abstract]
Due in one year or less, cost or amortized cost	$ 1,779	$ 1,574
Due after one year through five years, cost or amortized cost	7,566	7,721
Due after five years through ten years, cost or amortized cost	15,892	14,652
Due after ten years, cost or amortized cost	13,112	13,303
Total Amortized Cost Basis	38,349	37,250
Due in one year or less, estimated fair value	1,828	1,595
Due after one year through five years, estimated fair value	7,955	8,070
Due after five years through ten years, estimated fair value	16,332	14,915
Due after ten years, estimated fair value	14,778	14,989
Total Estimated Fair Value	$ 40,893	$ 39,569

Fair Value (Assets and liabilit

Fair Value (Assets and liabilities measured at fair value on a recurring basis) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	$ 42,406	$ 41,442
Corporate and other bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	18,970	17,760
States, municipalities and political subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	13,240	13,174
Residential mortgage-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	5,073	5,072
Commercial mortgage-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	2,040	2,197
Other asset-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	1,025	921
Total asset-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	8,138	8,190
U.S. Treasury and obligations of government-sponsored enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	93	67
Foreign Government Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	445	346
Redeemable preferred stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	19	35
Fixed maturity securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	40,905	39,572
Equity securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	110	197
Other invested assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	5	17
Short term investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	1,328	1,582
Life settlement contracts, included in Other assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	58	74
Embedded Derivative Financial Instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of liabilities, measured on a recurring basis	(3)	(5)
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	678	726
Fair value of liabilities, measured on a recurring basis	0	0
Level 1 [Member] | Corporate and other bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	0	0
Level 1 [Member] | States, municipalities and political subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	0	0
Level 1 [Member] | Residential mortgage-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	0	0
Level 1 [Member] | Commercial mortgage-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	0	0
Level 1 [Member] | Other asset-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	0	0
Level 1 [Member] | Total asset-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	0	0
Level 1 [Member] | U.S. Treasury and obligations of government-sponsored enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	93	66
Level 1 [Member] | Foreign Government Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	0	0
Level 1 [Member] | Redeemable preferred stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	19	35
Level 1 [Member] | Fixed maturity securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	112	101
Level 1 [Member] | Equity securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	91	177
Level 1 [Member] | Other invested assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	0	0
Level 1 [Member] | Short term investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	475	448
Level 1 [Member] | Life settlement contracts, included in Other assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	0	0
Level 1 [Member] | Embedded Derivative Financial Instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of liabilities, measured on a recurring basis	0	0
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	41,321	40,243
Fair value of liabilities, measured on a recurring basis	(3)	(5)
Level 2 [Member] | Corporate and other bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	18,840	17,592
Level 2 [Member] | States, municipalities and political subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	13,239	13,172
Level 2 [Member] | Residential mortgage-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	4,944	4,938
Level 2 [Member] | Commercial mortgage-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	2,027	2,175
Level 2 [Member] | Other asset-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	968	868
Level 2 [Member] | Total asset-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	7,939	7,981
Level 2 [Member] | U.S. Treasury and obligations of government-sponsored enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	0	1
Level 2 [Member] | Foreign Government Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	445	346
Level 2 [Member] | Redeemable preferred stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	0	0
Level 2 [Member] | Fixed maturity securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	40,463	39,092
Level 2 [Member] | Equity securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	0	0
Level 2 [Member] | Other invested assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	5	17
Level 2 [Member] | Short term investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	853	1,134
Level 2 [Member] | Life settlement contracts, included in Other assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	0	0
Level 2 [Member] | Embedded Derivative Financial Instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of liabilities, measured on a recurring basis	(3)	(5)
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	407	473
Fair value of liabilities, measured on a recurring basis	0	0
Level 3 [Member] | Corporate and other bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	130	168
Level 3 [Member] | States, municipalities and political subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	1	2
Level 3 [Member] | Residential mortgage-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	129	134
Level 3 [Member] | Commercial mortgage-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	13	22
Level 3 [Member] | Other asset-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	57	53
Level 3 [Member] | Total asset-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	199	209
Level 3 [Member] | U.S. Treasury and obligations of government-sponsored enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	0	0
Level 3 [Member] | Foreign Government Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	0	0
Level 3 [Member] | Redeemable preferred stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	0	0
Level 3 [Member] | Fixed maturity securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	330	379
Level 3 [Member] | Equity securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	19	20
Level 3 [Member] | Other invested assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	0	0
Level 3 [Member] | Short term investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	0	0
Level 3 [Member] | Life settlement contracts, included in Other assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	58	74
Level 3 [Member] | Embedded Derivative Financial Instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of liabilities, measured on a recurring basis	$ 0	$ 0

Fair Value (Table of reconcilia

Fair Value (Table of reconciliation for assets and liabilities measured at fair value on a recurring basis using significant unobservable inputs) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	$ 473	$ 1,281
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	5	39
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	(4)	(8)
Purchases	296	303
Sales	(61)	(276)
Settlements	(157)	(182)
Transfers into Level 3	61	79
Transfers out of Level 3	(206)	(763)
Balance, Ending, Assets	407	473
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	(5)	(1)
Corporate and other bonds [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	168	162
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	1	(2)
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	1	(3)
Purchases	163	65
Sales	(36)	(13)
Settlements	(103)	(35)
Transfers into Level 3	0	40
Transfers out of Level 3	(64)	(46)
Balance, Ending, Assets	130	168
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	0	(2)
States, municipalities and political subdivisions [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	2	94
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	0	1
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	0	0
Purchases	0	0
Sales	0	0
Settlements	(1)	(10)
Transfers into Level 3	0	0
Transfers out of Level 3	0	(83)
Balance, Ending, Assets	1	2
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	0	0
Residential mortgage-backed [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	134	189
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	3	5
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	(5)	(3)
Purchases	15	81
Sales	0	0
Settlements	(14)	(35)
Transfers into Level 3	56	14
Transfers out of Level 3	(60)	(117)
Balance, Ending, Assets	129	134
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	0	0
Commercial Mortgage Backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	22	83
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	(1)	7
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	(1)	(4)
Purchases	32	23
Sales	0	0
Settlements	(17)	(17)
Transfers into Level 3	3	17
Transfers out of Level 3	(25)	(87)
Balance, Ending, Assets	13	22
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	0	0
Other asset-backed [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	53	655
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	(2)	3
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	1	3
Purchases	86	130
Sales	(25)	(263)
Settlements	(1)	(52)
Transfers into Level 3	2	7
Transfers out of Level 3	(57)	(430)
Balance, Ending, Assets	57	53
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	0	0
Total asset-backed [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	209	927
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	0	15
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	(5)	(4)
Purchases	133	234
Sales	(25)	(263)
Settlements	(32)	(104)
Transfers into Level 3	61	38
Transfers out of Level 3	(142)	(634)
Balance, Ending, Assets	199	209
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	0	0
Fixed maturity securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	379	1,183
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	1	14
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	(4)	(7)
Purchases	296	299
Sales	(61)	(276)
Settlements	(136)	(149)
Transfers into Level 3	61	78
Transfers out of Level 3	(206)	(763)
Balance, Ending, Assets	330	379
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	0	(2)
Equity securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	20	16
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	(1)	0
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	0	(1)
Purchases	0	4
Sales	0	0
Settlements	0	0
Transfers into Level 3	0	1
Transfers out of Level 3	0	0
Balance, Ending, Assets	19	20
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	(2)	0
Life settlement contracts, included in Other assets [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	74	82
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	5	25
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	0	0
Purchases	0	0
Sales	0	0
Settlements	(21)	(33)
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Balance, Ending, Assets	58	74
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	$ (3)	$ 1

Fair Value (Narrative) (Details

Fair Value (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Fair Value, Assets, Level 2 to Level 1, Transfers	$ 0	$ 63
Fair Value, Assets, Level 1 to Level 2, Transfers	0	52
Other Invested Assets Overseas Deposit	$ 31	$ 27

Fair Value (Quantitative inform

Fair Value (Quantitative information about significant unobservable inputs in the fair value measurement of level 3 assets) (Details) - Income Approach Valuation Technique [Member] - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Fixed maturity securities [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Assets, Fair Value Disclosure	$ 106	$ 138
Fixed maturity securities [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Credit Spread	2.00%	3.00%
Fixed maturity securities [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Credit Spread	40.00%	184.00%
Fixed maturity securities [Member] | Weighted Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Credit Spread	4.00%	6.00%
Life settlement contracts, included in Other assets [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Assets, Fair Value Disclosure		$ 74
Discount rate risk premium		9.00%
Life settlement contracts, included in Other assets [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Mortality assumption		55.00%
Life settlement contracts, included in Other assets [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Mortality assumption		1676.00%
Life settlement contracts, included in Other assets [Member] | Weighted Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Mortality assumption		164.00%

Fair Value (Carrying amount and

Fair Value (Carrying amount and estimated fair value of financial instrument assets and liabilities which are not measured at fair value) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Financial Assets [Abstract]
Mortgage loans	$ 591	$ 678
Financial Liabilities [Abstract]
Short term debt	0	350
Long term debt	2,710	2,210
Carrying Amount [Member]
Financial Assets [Abstract]
Mortgage loans	591	678
Financial Liabilities [Abstract]
Short term debt		350
Long term debt	2,710	2,210
Estimated Fair Value [Member]
Financial Assets [Abstract]
Mortgage loans	594	688
Financial Liabilities [Abstract]
Short term debt		360
Long term debt	2,952	2,433
Level 1 [Member] | Estimated Fair Value [Member]
Financial Assets [Abstract]
Mortgage loans	0	0
Financial Liabilities [Abstract]
Short term debt		0
Long term debt	0	0
Level 2 [Member] | Estimated Fair Value [Member]
Financial Assets [Abstract]
Mortgage loans	0	0
Financial Liabilities [Abstract]
Short term debt		360
Long term debt	2,952	2,433
Level 3 [Member] | Estimated Fair Value [Member]
Financial Assets [Abstract]
Mortgage loans	594	688
Financial Liabilities [Abstract]
Short term debt		0
Long term debt	$ 0	$ 0

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Federal income taxes received from (paid to) Loews	$ (142)	$ (256)	$ (287)
Unrecognized tax benefits	0	0
Interest income (expense)	0	0	0
Unrecognized Tax Benefits, Income Tax Penalties Expense	0	0	0
Accrued interest and penalties	0	0
Deferred tax liability on undistributed income related to a foreign subsidiary	1
Undistributed Earnings from a Foreign Subsidiary	3
Foreign tax expense (benefit) on income from continuing operations	9	14	24
Income (loss) from continuing foreign operations	51	71	$ 66
Operating Loss Carryforwards	0
Tax Credit Carryforward, Amount	0
Valuation allowance	$ 0	$ 0

Income Taxes (Reconciliation be

Income Taxes (Reconciliation between the Company's federal income tax (expense) benefit at statutory rates and the recorded income tax (expense) benefit) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Income tax expense at statutory rates	$ (398)	$ (192)	$ (423)
Tax benefit from tax exempt income	124	123	119
Foreign taxes and credits	3	9	(6)
Other tax expense	(7)	(10)	(9)
Income tax (expense) benefit	$ (278)	$ (70)	$ (319)

Income Taxes (Current and defer

Income Taxes (Current and deferred components of the Company's income tax (expense) benefit) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Expense (Benefit), Continuing Operations [Abstract]
Current tax (expense) benefit	$ (142)	$ (220)	$ (318)
Deferred income tax (expense) benefit	(136)	150	(1)
Income tax (expense) benefit	$ (278)	$ (70)	$ (319)

Income Taxes (Significant compo

Income Taxes (Significant components of the Company's deferred tax assets and liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Deferred Tax Assets:
Property and casualty claim and claim adjustment expense reserves	$ 125	$ 178
Unearned premium reserves	206	230
Receivables	27	29
Employee benefits	272	281
Life settlement contracts	56	48
Deferred retroactive reinsurance benefit	117	84
Investment valuation differences	0	29
Other assets	148	142
Gross deferred tax assets	951	1,021
Deferred Tax Liabilities:
Investment valuation differences	57	0
Deferred acquisition costs	120	117
Net unrealized gains	309	202
Other liabilities	86	64
Deferred Tax Liabilities, Gross	572	383
Net deferred tax asset (liability)	$ 379	$ 638

Claim and Claim Adjustment Ex73

Claim and Claim Adjustment Expense Reserves (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2010
Catastrophe losses net of reinsurance		$ 165	$ 141	$ 156
Pretax (favorable) unfavorable net prior year claim and allocated claim adjustment expense reserve development Life & Group		(45)	(50)	(14)
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development, Workers' Compensation Reinsurance Pool				26
Loss Portfolio Transfer [Member]
Net A&EP claim and allocated claim adjustment expense reserves ceded to NICO					$ 1,600
Aggregate limit under A&EP Loss Portfolio Transfer					4,000
A&EP claim and allocated claim adjustment expense reserves ceded under existing third party reinsurance contracts transferred to NICO under A&EP Loss Portfolio Transfer					1,200
Reinsurance premium paid to NICO under A&EP Loss Portfolio Transfer					2,000
Net reinsurance receivables transferrred to NICO under A&EP Loss Portfolio Transfer					215
Total consideration paid to NICO under AEP Loss Portfolio Transfer					$ 2,200
Net AEP adverse development before consideration of LPT	$ 200	200	150	$ 0
Unfavorable Development related to Asbestos Claims and Higher than Expected Severity in Pollution Claims			150
Cumulative amounts ceded under AEP Loss Portfolio Transfer		2,800	2,600
Deferred reinsurance benefit yet to be recognized		334	$ 241
Fair value of collateral trust account established by NICO under A&EP Loss Portfolio Transfer		$ 2,800

Claim and Claim Adjustment Ex74

Claim and Claim Adjustment Expense Reserves (Reconcilliation of claim and claim adjustment expense reserves) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reserves, beginning of year: [Abstract]
Gross		$ 22,663	$ 23,271	$ 24,089
Ceded		4,087	4,344	4,972
Net reserves, beginning of year		18,576	18,927	19,117
Change in net reserves due to acquisition (disposition) of subsidiaries		0	0	(13)
Net incurred claim and claim adjustment expenses:
Provision for insured events of current year		5,025	4,934	5,043
Decrease in provision for insured events of prior years		(342)	(255)	(36)
Amortization of discount		175	166	161
Total net incurred (1)	[1]	4,858	4,845	5,168
Net payments attributable to:
Current year events		(967)	(856)	(945)
Prior year events		(4,167)	(4,089)	(4,355)
Total net payments		(5,134)	(4,945)	(5,300)
Foreign currency translation adjustment and other		(51)	(251)	(45)
Net reserves, end of year		18,249	18,576	18,927
Ceded reserves, end of year		4,094	4,087	4,344
Gross reserves, end of year		$ 22,343	$ 22,663	$ 23,271
[1]	Total net incurred above does not agree to Insurance claims and policyholders' benefits as reflected on the Consolidated Statements of Operations due to amounts related to retroactive reinsurance deferred gain accounting, uncollectible reinsurance and loss deductible receivables, and benefit expenses related to future policy benefits, which are not reflected in the table above.

Claim and Claim Adjustment Ex75

Claim and Claim Adjustment Expense Reserves (Gross and net carried claim and claim adjustment expense reserves) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Gross Case Reserves	$ 11,860	$ 12,102
Gross IBNR Reserves	10,483	10,561
Total Gross Carried Claim and Claim Adjustment Expense Reserves	22,343	22,663	$ 23,271	$ 24,089
Net Case Reserves	9,627	9,836
Net IBNR Reserves	8,622	8,740
Total Net Carried Claim and Claim Adjustment Expense Reserves	18,249	18,576	$ 18,927	$ 19,117
Specialty [Member]
Gross Case Reserves	1,871	2,011
Gross IBNR Reserves	4,278	4,258
Total Gross Carried Claim and Claim Adjustment Expense Reserves	6,149	6,269
Net Case Reserves	1,681	1,810
Net IBNR Reserves	3,723	3,758
Total Net Carried Claim and Claim Adjustment Expense Reserves	5,404	5,568
Commercial [Member]
Gross Case Reserves	4,661	4,975
Gross IBNR Reserves	4,233	4,208
Total Gross Carried Claim and Claim Adjustment Expense Reserves	8,894	9,183
Net Case Reserves	4,353	4,651
Net IBNR Reserves	3,952	3,925
Total Net Carried Claim and Claim Adjustment Expense Reserves	8,305	8,576
International [Member]
Gross Case Reserves	632	622
Gross IBNR Reserves	696	725
Total Gross Carried Claim and Claim Adjustment Expense Reserves	1,328	1,347
Net Case Reserves	548	531
Net IBNR Reserves	653	688
Total Net Carried Claim and Claim Adjustment Expense Reserves	1,201	1,219
Life and Group Non-Core [Member]
Gross Case Reserves	3,172	2,973
Gross IBNR Reserves	186	247
Total Gross Carried Claim and Claim Adjustment Expense Reserves	3,358	3,220
Net Case Reserves	2,951	2,714
Net IBNR Reserves	158	216
Total Net Carried Claim and Claim Adjustment Expense Reserves	3,109	2,930
Corporate and Other [Member]
Gross Case Reserves	1,524	1,521
Gross IBNR Reserves	1,090	1,123
Total Gross Carried Claim and Claim Adjustment Expense Reserves	2,614	2,644
Net Case Reserves	94	130
Net IBNR Reserves	136	153
Total Net Carried Claim and Claim Adjustment Expense Reserves	$ 230	$ 283

Claim and Claim Adjustment Ex76

Claim and Claim Adjustment Expense Reserves (Net prior year development) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Pretax (favorable) unfavorable net prior year claim and allocated claim adjustment expense reserve development, excluding Life & Group	$ (288)	$ (210)	$ (21)
Pretax (favorable) unfavorable premium development, excluding Life & Group	(26)	(8)	(32)
Total pretax (favorable) unfavorable net prior year development, excluding Life & Group	(314)	(218)	(53)
Specialty [Member]
Segment Reporting Information [Line Items]
Pretax (favorable) unfavorable net prior year claim and allocated claim adjustment expense reserve development, excluding Life & Group	(287)	(141)	(136)
Pretax (favorable) unfavorable premium development, excluding Life & Group	(18)	(11)	(13)
Total pretax (favorable) unfavorable net prior year development, excluding Life & Group	(305)	(152)	(149)
Commercial [Member]
Segment Reporting Information [Line Items]
Pretax (favorable) unfavorable net prior year claim and allocated claim adjustment expense reserve development, excluding Life & Group	55	(15)	176
Pretax (favorable) unfavorable premium development, excluding Life & Group	(2)	(15)	(20)
Total pretax (favorable) unfavorable net prior year development, excluding Life & Group	53	(30)	156
International [Member]
Segment Reporting Information [Line Items]
Pretax (favorable) unfavorable net prior year claim and allocated claim adjustment expense reserve development, excluding Life & Group	(58)	(54)	(59)
Pretax (favorable) unfavorable premium development, excluding Life & Group	(6)	18	2
Total pretax (favorable) unfavorable net prior year development, excluding Life & Group	(64)	(36)	(57)
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Pretax (favorable) unfavorable net prior year claim and allocated claim adjustment expense reserve development, excluding Life & Group	2	0	(2)
Pretax (favorable) unfavorable premium development, excluding Life & Group	0	0	(1)
Total pretax (favorable) unfavorable net prior year development, excluding Life & Group	$ 2	$ 0	$ (3)

Claim and Claim Adjustment Ex77

Claim and Claim Adjustment Expense Reserves (Net prior year claim and allocated claim adjustment expense reserve development for Specialty segment) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Pretax (favorable) unfavorable net prior year claim and allocated claim adjustment expense reserve development, excluding Life & Group	$ (288)	$ (210)	$ (21)
Specialty [Member]
Net prior year claim and allocated claim adjustment expense reserve development, Medical Professional Liability	(37)	(43)	39
Net prior year claim and allocated claim adjustment expense reserve development, Other Professional Liability and Management Liability	(130)	0	(87)
Net prior year claim and allocated claim adjustment expense reserve development, Surety	(63)	(69)	(82)
Warranty	4	(2)	(2)
Net prior year claim and allocated claim adjustment expense reserve development, Other	(61)	(27)	(4)
Pretax (favorable) unfavorable net prior year claim and allocated claim adjustment expense reserve development, excluding Life & Group	$ (287)	$ (141)	$ (136)

Claim and Claim Adjustment Ex78

Claim and Claim Adjustment Expense Reserves Short Duration Contracts - Specialty Reconciliation (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	$ 18,249	$ 18,576	$ 18,927	$ 19,117
Specialty - Medical Professional Liability [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	1,779
Specialty - Other Professional and Management Liability [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	3,063
Specialty - Surety [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	394
Specialty - Warranty [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	37
Specialty - Other [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	131
Specialty [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	$ 5,404	$ 5,568

Claim and Claim Adjustment Ex79

Claim and Claim Adjustment Expense Reserves Short Duration Contracts - Net Incurred Claims and Allocated Claim Adjustment Expenses Specialty - Medical Professional Liability (Details) - Specialty - Medical Professional Liability [Member] $ in Millions	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 ($)	Dec. 31, 2007USD ($)
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 1,054
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 4,872
Short-duration Insurance Contracts, Accident Year 2007 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	12,122
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 9
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 385	$ 399	$ 401	$ 390	$ 391	$ 395	$ 427	$ 444	$ 452	$ 448
Short-duration Insurance Contracts, Accident Year 2008 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	14,094
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 9
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 442	455	467	468	468	480	496	451	$ 426
Short-duration Insurance Contracts, Accident Year 2009 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	15,573
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 12
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 432	463	471	480	506	494	469	$ 462
Short-duration Insurance Contracts, Accident Year 2010 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	15,206
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 16
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 403	446	470	486	478	478	$ 483
Short-duration Insurance Contracts, Accident Year 2011 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	17,428
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 23
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 491	501	533	507	492	$ 486
Short-duration Insurance Contracts, Accident Year 2012 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	18,375
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 47
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 559	567	575	529	$ 526
Short-duration Insurance Contracts, Accident Year 2013 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	19,565
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 95
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 567	560	540	$ 534
Short-duration Insurance Contracts, Accident Year 2014 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	19,286
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 165
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 585	548	$ 511
Short-duration Insurance Contracts, Accident Year 2015 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	16,798
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 278
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 539	$ 480
Short-duration Insurance Contracts, Accident Year 2016 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	11,600
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 400
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 469

Claim and Claim Adjustment Ex80

Claim and Claim Adjustment Expense Reserves Short Duration Contracts - Net Cumulative Paid Claim and Claim Adjustment Expenses Specialty - Medical Professional Liability (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008	Dec. 31, 2007
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years	$ 4,167	$ 4,089	$ 4,355
Liability for Unpaid Claims and Claims Adjustment Expense, Net	18,249	18,576	18,927	$ 19,117
Specialty - Medical Professional Liability [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	3,156
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	1,716
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years	30
Short-duration Insurance Contracts, Liability for Unpaid Claims and Claims Adjustment Expense, Accumulated Unallocated Claim Adjustment Expense	33
Liability for Unpaid Claims and Claims Adjustment Expense, Net	1,779
Short-duration Insurance Contracts, Accident Year 2007 [Member] | Specialty - Medical Professional Liability [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	365	364	352	326	$ 296	$ 247	$ 201	$ 134	$ 68	$ 11
Short-duration Insurance Contracts, Accident Year 2008 [Member] | Specialty - Medical Professional Liability [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	428	409	395	377	332	282	207	90	$ 9
Short-duration Insurance Contracts, Accident Year 2009 [Member] | Specialty - Medical Professional Liability [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	396	377	353	328	278	180	75	$ 9
Short-duration Insurance Contracts, Accident Year 2010 [Member] | Specialty - Medical Professional Liability [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	371	361	338	273	186	93	$ 11
Short-duration Insurance Contracts, Accident Year 2011 [Member] | Specialty - Medical Professional Liability [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	407	379	315	225	121	$ 18
Short-duration Insurance Contracts, Accident Year 2012 [Member] | Specialty - Medical Professional Liability [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	428	359	236	121	$ 15
Short-duration Insurance Contracts, Accident Year 2013 [Member] | Specialty - Medical Professional Liability [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	364	259	121	$ 18
Short-duration Insurance Contracts, Accident Year 2014 [Member] | Specialty - Medical Professional Liability [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	274	149	$ 25
Short-duration Insurance Contracts, Accident Year 2015 [Member] | Specialty - Medical Professional Liability [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	105	$ 22
Short-duration Insurance Contracts, Accident Year 2016 [Member] | Specialty - Medical Professional Liability [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 18

Claim and Claim Adjustment Ex81

Claim and Claim Adjustment Expense Reserves Short Duration Contracts - Net Strengthening or Releasing of Prior Accident Year Reserves Specialty - Medical Professional Liability (Details) - Specialty - Medical Professional Liability [Member] - USD ($) $ in Millions	12 Months Ended									24 Months Ended	36 Months Ended	48 Months Ended	60 Months Ended	72 Months Ended	84 Months Ended	96 Months Ended	108 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016
Claims Development [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	$ (16)	$ (29)	$ 63
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development Prior Years	(21)	(14)	(24)
Net prior year claim and allocated claim adjustment expense reserve development, Medical Professional Liability	(37)	(43)	39
Short-duration Insurance Contracts, Accident Year 2007 [Member]
Claims Development [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	(14)	(2)	11	$ (1)	$ (4)	$ (32)	$ (17)	$ (8)	$ 4								$ (63)
Short-duration Insurance Contracts, Accident Year 2008 [Member]
Claims Development [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	(13)	(12)	(1)	0	(12)	(16)	45	$ 25								$ 16
Short-duration Insurance Contracts, Accident Year 2009 [Member]
Claims Development [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	(31)	(8)	(9)	(26)	12	25	$ 7								$ (30)
Short-duration Insurance Contracts, Accident Year 2010 [Member]
Claims Development [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	(43)	(24)	(16)	8	0	$ (5)								$ (80)
Short-duration Insurance Contracts, Accident Year 2011 [Member]
Claims Development [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	(10)	(32)	26	15	$ 6								$ 5
Short-duration Insurance Contracts, Accident Year 2012 [Member]
Claims Development [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	(8)	(8)	46	$ 3								$ 33
Short-duration Insurance Contracts, Accident Year 2013 [Member]
Claims Development [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	7	20	$ 6								$ 33
Short-duration Insurance Contracts, Accident Year 2014 [Member]
Claims Development [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	37	$ 37								$ 74
Short-duration Insurance Contracts, Accident Year 2015 [Member]
Claims Development [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	$ 59

Claim and Claim Adjustment Ex82

Claim and Claim Adjustment Expense Reserves Short Duration Contracts - Net Incurred Claims and Allocated Claim Adjustment Expenses Specialty - Other Professional and Management LIability (Details) - Specialty - Other Professional and Management Liability [Member] $ in Millions	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 ($)	Dec. 31, 2007USD ($)
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 2,014
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 8,362
Short-duration Insurance Contracts, Accident Year 2007 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	16,011
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 13
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 662	$ 662	$ 681	$ 704	$ 724	$ 734	$ 754	$ 806	$ 817	$ 804
Short-duration Insurance Contracts, Accident Year 2008 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	16,326
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 35
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 827	845	850	880	915	924	954	933	$ 916
Short-duration Insurance Contracts, Accident Year 2009 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	17,263
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 50
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 903	895	900	891	898	903	873	$ 829
Short-duration Insurance Contracts, Accident Year 2010 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	17,796
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 39
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 823	836	846	848	850	827	$ 825
Short-duration Insurance Contracts, Accident Year 2011 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	18,620
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 107
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 910	944	948	933	904	$ 876
Short-duration Insurance Contracts, Accident Year 2012 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	18,228
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 107
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 833	870	876	894	$ 907
Short-duration Insurance Contracts, Accident Year 2013 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	17,324
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 137
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 840	879	841	$ 844
Short-duration Insurance Contracts, Accident Year 2014 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	16,886
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 306
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 854	859	$ 841
Short-duration Insurance Contracts, Accident Year 2015 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	16,391
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 478
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 851	$ 847
Short-duration Insurance Contracts, Accident Year 2016 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	15,045
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 742
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 859

Claim and Claim Adjustment Ex83

Claim and Claim Adjustment Expense Reserves Short Duration Contracts - Net Cumulative Paid Claim and Claim Adjustment Expenses Specialty - Other Professional and Management Liability (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008	Dec. 31, 2007
Short Duration Contracts Net Cumulative Paid Claim Adjustment Expenses [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years	$ 4,167	$ 4,089	$ 4,355
Liability for Unpaid Claims and Claims Adjustment Expense, Net	18,249	18,576	18,927	$ 19,117
Specialty - Other Professional and Management Liability [Member]
Short Duration Contracts Net Cumulative Paid Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	5,475
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	2,887
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years	104
Short-duration Insurance Contracts, Liability for Unpaid Claims and Claims Adjustment Expense, Accumulated Unallocated Claim Adjustment Expense	72
Liability for Unpaid Claims and Claims Adjustment Expense, Net	3,063
Short-duration Insurance Contracts, Accident Year 2007 [Member] | Specialty - Other Professional and Management Liability [Member]
Short Duration Contracts Net Cumulative Paid Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	614	593	585	564	$ 524	$ 472	$ 397	$ 307	$ 162	$ 32
Short-duration Insurance Contracts, Accident Year 2008 [Member] | Specialty - Other Professional and Management Liability [Member]
Short Duration Contracts Net Cumulative Paid Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	741	719	678	641	600	515	376	181	$ 39
Short-duration Insurance Contracts, Accident Year 2009 [Member] | Specialty - Other Professional and Management Liability [Member]
Short Duration Contracts Net Cumulative Paid Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	798	769	719	638	550	358	195	$ 37
Short-duration Insurance Contracts, Accident Year 2010 [Member] | Specialty - Other Professional and Management Liability [Member]
Short Duration Contracts Net Cumulative Paid Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	721	670	630	541	404	203	$ 31
Short-duration Insurance Contracts, Accident Year 2011 [Member] | Specialty - Other Professional and Management Liability [Member]
Short Duration Contracts Net Cumulative Paid Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	726	682	604	502	313	$ 71
Short-duration Insurance Contracts, Accident Year 2012 [Member] | Specialty - Other Professional and Management Liability [Member]
Short Duration Contracts Net Cumulative Paid Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	648	570	398	248	$ 57
Short-duration Insurance Contracts, Accident Year 2013 [Member] | Specialty - Other Professional and Management Liability [Member]
Short Duration Contracts Net Cumulative Paid Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	583	426	240	$ 51
Short-duration Insurance Contracts, Accident Year 2014 [Member] | Specialty - Other Professional and Management Liability [Member]
Short Duration Contracts Net Cumulative Paid Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	375	212	$ 51
Short-duration Insurance Contracts, Accident Year 2015 [Member] | Specialty - Other Professional and Management Liability [Member]
Short Duration Contracts Net Cumulative Paid Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	209	$ 48
Short-duration Insurance Contracts, Accident Year 2016 [Member] | Specialty - Other Professional and Management Liability [Member]
Short Duration Contracts Net Cumulative Paid Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 60

Claim and Claim Adjustment Ex84

Claim and Claim Adjustment Expense Reserves Short Duration Contracts - Net Strengthening or Releasing of Prior Accident Year Reserves Specialty - Other Professional and Management Liability (Details) - Specialty - Other Professional and Management Liability [Member] - USD ($) $ in Millions	12 Months Ended									24 Months Ended	36 Months Ended	48 Months Ended	60 Months Ended	72 Months Ended	84 Months Ended	96 Months Ended	108 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016
Claims Development [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	$ (134)	$ 7	$ (52)
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development Prior Years	4	(7)	(35)
Net prior year claim and allocated claim adjustment expense reserve development, Other Professional Liability and Management Liability	(130)	0	(87)
Short-duration Insurance Contracts, Accident Year 2007 [Member]
Claims Development [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	0	(19)	(23)	$ (20)	$ (10)	$ (20)	$ (52)	$ (11)	$ 13								$ (142)
Short-duration Insurance Contracts, Accident Year 2008 [Member]
Claims Development [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	(18)	(5)	(30)	(35)	(9)	(30)	21	$ 17								$ (89)
Short-duration Insurance Contracts, Accident Year 2009 [Member]
Claims Development [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	8	(5)	9	(7)	(5)	30	$ 44								$ 74
Short-duration Insurance Contracts, Accident Year 2010 [Member]
Claims Development [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	(13)	(10)	(2)	(2)	23	$ 2								$ (2)
Short-duration Insurance Contracts, Accident Year 2011 [Member]
Claims Development [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	(34)	(4)	15	29	$ 28								$ 34
Short-duration Insurance Contracts, Accident Year 2012 [Member]
Claims Development [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	(37)	(6)	(18)	$ (13)								$ (74)
Short-duration Insurance Contracts, Accident Year 2013 [Member]
Claims Development [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	(39)	38	$ (3)								$ (4)
Short-duration Insurance Contracts, Accident Year 2014 [Member]
Claims Development [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	(5)	$ 18								$ 13
Short-duration Insurance Contracts, Accident Year 2015 [Member]
Claims Development [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	$ 4

Claim and Claim Adjustment Ex85

Claim and Claim Adjustment Expense Reserves Short Duration Contracts - Net Incurred Claims and Allocated Claim Adjustment Expenses Specialty - Surety (Details) - Specialty - Surety [Member] $ in Millions	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 ($)	Dec. 31, 2007USD ($)
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 319
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 787
Short-duration Insurance Contracts, Accident Year 2007 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	6,270
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 0
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 50	$ 49	$ 49	$ 51	$ 56	$ 59	$ 57	$ 81	$ 107	$ 98
Short-duration Insurance Contracts, Accident Year 2008 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	7,153
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 0
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 44	45	48	52	61	68	73	114	$ 114
Short-duration Insurance Contracts, Accident Year 2009 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	6,654
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 1
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 53	52	59	68	85	103	114	$ 114
Short-duration Insurance Contracts, Accident Year 2010 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	5,943
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 8
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 63	66	76	84	111	112	$ 112
Short-duration Insurance Contracts, Accident Year 2011 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	5,760
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 9
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 70	75	87	116	121	$ 120
Short-duration Insurance Contracts, Accident Year 2012 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	5,473
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 16
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 52	70	98	122	$ 120
Short-duration Insurance Contracts, Accident Year 2013 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	4,890
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 24
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 106	115	121	$ 120
Short-duration Insurance Contracts, Accident Year 2014 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	4,737
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 51
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 94	124	$ 123
Short-duration Insurance Contracts, Accident Year 2015 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	4,279
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 100
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 131	$ 131
Short-duration Insurance Contracts, Accident Year 2016 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	2,902
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 110
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 124

Claim and Claim Adjustment Ex86

Claim and Claim Adjustment Expense Reserves Short Duration Contracts - Net Cumulative Paid Claim and Claim Adjustment Expenses Specialty - Surety (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008	Dec. 31, 2007
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years	$ 4,167	$ 4,089	$ 4,355
Liability for Unpaid Claims and Claims Adjustment Expense, Net	18,249	18,576	18,927	$ 19,117
Specialty - Surety [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	437
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	350
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years	16
Short-duration Insurance Contracts, Liability for Unpaid Claims and Claims Adjustment Expense, Accumulated Unallocated Claim Adjustment Expense	28
Liability for Unpaid Claims and Claims Adjustment Expense, Net	394
Specialty - Surety [Member] | Short-duration Insurance Contracts, Accident Year 2007 [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	50	49	48	46	$ 46	$ 46	$ 45	$ 40	$ 30	$ 12
Specialty - Surety [Member] | Short-duration Insurance Contracts, Accident Year 2008 [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	43	43	43	43	42	39	35	27	$ 9
Specialty - Surety [Member] | Short-duration Insurance Contracts, Accident Year 2009 [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	47	46	45	43	41	34	24	$ 13
Specialty - Surety [Member] | Short-duration Insurance Contracts, Accident Year 2010 [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	55	58	57	55	50	34	$ 13
Specialty - Surety [Member] | Short-duration Insurance Contracts, Accident Year 2011 [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	60	60	58	55	42	$ 19
Specialty - Surety [Member] | Short-duration Insurance Contracts, Accident Year 2012 [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	35	35	34	32	$ 5
Specialty - Surety [Member] | Short-duration Insurance Contracts, Accident Year 2013 [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	78	69	40	$ 16
Specialty - Surety [Member] | Short-duration Insurance Contracts, Accident Year 2014 [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	38	30	$ 7
Specialty - Surety [Member] | Short-duration Insurance Contracts, Accident Year 2015 [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	26	$ 7
Specialty - Surety [Member] | Short-duration Insurance Contracts, Accident Year 2016 [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 5

Claim and Claim Adjustment Ex87

Claim and Claim Adjustment Expense Reserves Short Duration Contracts - Net Strengthening or Releasing of Prior Accident Year Reserves Specialty - Surety (Details) - Specialty - Surety [Member] - USD ($) $ in Millions	12 Months Ended										24 Months Ended	36 Months Ended	48 Months Ended	60 Months Ended	72 Months Ended	84 Months Ended	96 Months Ended	108 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008	Dec. 31, 2007	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016
Claims Development [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	$ (64)	$ (65)	$ (75)
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development Prior Years	1	(4)	(7)
Net prior year claim and allocated claim adjustment expense reserve development, Surety	(63)	(69)	(82)
Short-duration Insurance Contracts, Accident Year 2007 [Member]
Claims Development [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	1	0	(2)	$ (5)	$ (3)	$ 2	$ (24)	$ (26)	$ 9									$ (48)
Short-duration Insurance Contracts, Accident Year 2008 [Member]
Claims Development [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	(1)	(3)	(4)	(9)	(7)	(5)	(41)	0									$ (70)
Short-duration Insurance Contracts, Accident Year 2009 [Member]
Claims Development [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	1	(7)	(9)	(17)	(18)	(11)	0									$ (61)
Short-duration Insurance Contracts, Accident Year 2010 [Member]
Claims Development [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	(3)	(10)	(8)	(27)	(1)	0									$ (49)
Short-duration Insurance Contracts, Accident Year 2011 [Member]
Claims Development [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	(5)	(12)	(29)	(5)	1									$ (50)
Short-duration Insurance Contracts, Accident Year 2012 [Member]
Claims Development [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	(18)	(28)	(24)	2									$ (68)
Short-duration Insurance Contracts, Accident Year 2013 [Member]
Claims Development [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	(9)	(6)	1									$ (14)
Short-duration Insurance Contracts, Accident Year 2014 [Member]
Claims Development [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	(30)	1									$ (29)
Short-duration Insurance Contracts, Accident Year 2015 [Member]
Claims Development [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	$ 0

Claim and Claim Adjustment Ex88

Claim and Claim Adjustment Expense Reserves (Net prior year claim and allocated claim adjustment expense reserve development for Commercial segment) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Pretax (favorable) unfavorable net prior year claim and allocated claim adjustment expense reserve development, excluding Life & Group	$ (288)	$ (210)	$ (21)
Commercial [Member]
Net prior year claim and allocated claim adjustment expense reserve development, Commercial Auto	(46)	(22)	31
Net prior year claim and allocated claim adjustment expense reserve development, General Liability	(28)	(33)	45
Net prior year claim and allocated claim adjustment expense reserve development, Workers' Compensation	150	80	139
Property and Other	(21)	(40)	(39)
Pretax (favorable) unfavorable net prior year claim and allocated claim adjustment expense reserve development, excluding Life & Group	$ 55	$ (15)	$ 176

Claim and Claim Adjustment Ex89

Claim and Claim Adjustment Expense Reserves Short Duration Contracts - Commercial Reconciliation (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	$ 18,249	$ 18,576	$ 18,927	$ 19,117
Commercial - Auto [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	424
Commercial - General Liability [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	3,248
Commercial - Workers Compensation [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	4,306
Commercial - Property and Other [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	327
Commercial [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	$ 8,305	$ 8,576

Claim and Claim Adjustment Ex90

Claim and Claim Adjustment Expense Reserves Short Duration Contracts - Net Incurred Claims and Allocated Claim Adjustment Expenses Commercial - Auto (Details) - Commercial - Auto [Member] $ in Millions	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 ($)	Dec. 31, 2007USD ($)
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 247
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 2,630
Short-duration Insurance Contracts, Accident Year 2007 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	67,473
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 0
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 352	$ 354	$ 355	$ 356	$ 358	$ 355	$ 360	$ 368	$ 367	$ 348
Short-duration Insurance Contracts, Accident Year 2008 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	56,407
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 0
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 296	298	298	305	309	306	316	323	$ 322
Short-duration Insurance Contracts, Accident Year 2009 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	47,325
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 0
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 272	275	277	281	278	274	272	$ 287
Short-duration Insurance Contracts, Accident Year 2010 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	46,324
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 1
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 281	286	291	283	279	274	$ 262
Short-duration Insurance Contracts, Accident Year 2011 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	46,676
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 5
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 285	290	293	279	273	$ 262
Short-duration Insurance Contracts, Accident Year 2012 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	45,279
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 11
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 300	296	292	282	$ 270
Short-duration Insurance Contracts, Accident Year 2013 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	38,513
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 20
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 241	257	259	$ 242
Short-duration Insurance Contracts, Accident Year 2014 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	32,958
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 40
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 210	221	$ 231
Short-duration Insurance Contracts, Accident Year 2015 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	29,714
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 65
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 197	$ 199
Short-duration Insurance Contracts, Accident Year 2016 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	25,196
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 105
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 196

Claim and Claim Adjustment Ex91

Claim and Claim Adjustment Expense Reserves Short Duration Contracts - Net Cumulative Paid Claim and Claim Adjustment Expenses Commercial - Auto (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008	Dec. 31, 2007
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years	$ 4,167	$ 4,089	$ 4,355
Liability for Unpaid Claims and Claims Adjustment Expense, Net	18,249	18,576	18,927	$ 19,117
Commercial - Auto [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	2,220
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	410
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years	4
Short-duration Insurance Contracts, Liability for Unpaid Claims and Claims Adjustment Expense, Accumulated Unallocated Claim Adjustment Expense	10
Liability for Unpaid Claims and Claims Adjustment Expense, Net	424
Commercial - Auto [Member] | Short-duration Insurance Contracts, Accident Year 2007 [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	351	350	349	348	$ 340	$ 329	$ 295	$ 250	$ 185	$ 93
Commercial - Auto [Member] | Short-duration Insurance Contracts, Accident Year 2008 [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	293	292	291	289	274	244	210	158	$ 83
Commercial - Auto [Member] | Short-duration Insurance Contracts, Accident Year 2009 [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	270	270	269	257	229	188	128	$ 72
Commercial - Auto [Member] | Short-duration Insurance Contracts, Accident Year 2010 [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	279	274	265	240	197	137	$ 72
Commercial - Auto [Member] | Short-duration Insurance Contracts, Accident Year 2011 [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	275	264	241	193	141	$ 78
Commercial - Auto [Member] | Short-duration Insurance Contracts, Accident Year 2012 [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	276	253	214	157	$ 77
Commercial - Auto [Member] | Short-duration Insurance Contracts, Accident Year 2013 [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	195	164	132	$ 73
Commercial - Auto [Member] | Short-duration Insurance Contracts, Accident Year 2014 [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	135	100	$ 63
Commercial - Auto [Member] | Short-duration Insurance Contracts, Accident Year 2015 [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	95	$ 52
Commercial - Auto [Member] | Short-duration Insurance Contracts, Accident Year 2016 [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 51

Claim and Claim Adjustment Ex92

Claim and Claim Adjustment Expense Reserves Short Duration Contracts - Net Strengthening or Releasing of Prior Accident Year Reserves Commercial - Auto (Details) - Commercial - Auto [Member] - USD ($) $ in Millions	12 Months Ended									24 Months Ended	36 Months Ended	48 Months Ended	60 Months Ended	72 Months Ended	84 Months Ended	96 Months Ended	108 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	$ (42)	$ (19)	$ 37
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development Prior Years	(4)	(3)	(6)
Net prior year claim and allocated claim adjustment expense reserve development, Commercial Auto	(46)	(22)	31
Short-duration Insurance Contracts, Accident Year 2007 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	(2)	(1)	(1)	$ (2)	$ 3	$ (5)	$ (8)	$ 1	$ 19								$ 4
Short-duration Insurance Contracts, Accident Year 2008 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	(2)	0	(7)	(4)	3	(10)	(7)	$ 1								$ (26)
Short-duration Insurance Contracts, Accident Year 2009 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	(3)	(2)	(4)	3	4	2	$ (15)								$ (15)
Short-duration Insurance Contracts, Accident Year 2010 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	(5)	(5)	8	4	5	$ 12								$ 19
Short-duration Insurance Contracts, Accident Year 2011 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	(5)	(3)	14	6	$ 11								$ 23
Short-duration Insurance Contracts, Accident Year 2012 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	4	4	10	$ 12								$ 30
Short-duration Insurance Contracts, Accident Year 2013 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	(16)	(2)	$ 17								$ (1)
Short-duration Insurance Contracts, Accident Year 2014 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	(11)	$ (10)								$ (21)
Short-duration Insurance Contracts, Accident Year 2015 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	$ (2)

Claim and Claim Adjustment Ex93

Claim and Claim Adjustment Expense Reserves Short Duration Contracts - Net Incurred Claims and Allocated Claim Adjustment Expenses Commercial - General Liability (Details) - Commercial - General Liability [Member] $ in Millions	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 ($)	Dec. 31, 2007USD ($)
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 1,382
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 6,065
Short-duration Insurance Contracts, Accident Year 2007 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	53,553
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 28
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 540	$ 548	$ 545	$ 559	$ 600	$ 610	$ 639	$ 678	$ 673	$ 774
Short-duration Insurance Contracts, Accident Year 2008 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	44,586
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 18
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 591	600	613	632	633	647	630	604	$ 611
Short-duration Insurance Contracts, Accident Year 2009 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	43,955
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 16
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 622	619	623	629	633	634	637	$ 591
Short-duration Insurance Contracts, Accident Year 2010 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	43,378
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 25
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 659	675	695	649	599	597	$ 566
Short-duration Insurance Contracts, Accident Year 2011 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	38,101
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 41
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 621	611	610	564	534	$ 537
Short-duration Insurance Contracts, Accident Year 2012 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	34,037
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 63
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 558	570	579	563	$ 539
Short-duration Insurance Contracts, Accident Year 2013 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	32,897
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 142
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 643	634	645	$ 615
Short-duration Insurance Contracts, Accident Year 2014 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	26,744
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 224
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 635	634	$ 627
Short-duration Insurance Contracts, Accident Year 2015 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	21,687
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 330
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 574	$ 573
Short-duration Insurance Contracts, Accident Year 2016 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	16,720
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 495
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 622

Claim and Claim Adjustment Ex94

Claim and Claim Adjustment Expense Reserves Short Duration Contracts - Net Cumulative Paid Claim and Claim Adjustment Expenses Commercial - General Liability (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008	Dec. 31, 2007
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years	$ 4,167	$ 4,089	$ 4,355
Liability for Unpaid Claims and Claims Adjustment Expense, Net	18,249	18,576	18,927	$ 19,117
Commercial - General Liability [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	4,002
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	2,063
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years	1,130
Short-duration Insurance Contracts, Liability for Unpaid Claims and Claims Adjustment Expense, Accumulated Unallocated Claim Adjustment Expense	55
Liability for Unpaid Claims and Claims Adjustment Expense, Net	3,248
Commercial - General Liability [Member] | Short-duration Insurance Contracts, Accident Year 2007 [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	504	497	492	481	$ 458	$ 413	$ 328	$ 236	$ 130	$ 30
Commercial - General Liability [Member] | Short-duration Insurance Contracts, Accident Year 2008 [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	567	560	550	528	473	390	261	129	$ 31
Commercial - General Liability [Member] | Short-duration Insurance Contracts, Accident Year 2009 [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	584	557	532	486	392	270	112	$ 33
Commercial - General Liability [Member] | Short-duration Insurance Contracts, Accident Year 2010 [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	608	577	530	414	267	139	$ 27
Commercial - General Liability [Member] | Short-duration Insurance Contracts, Accident Year 2011 [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	534	484	389	253	135	$ 27
Commercial - General Liability [Member] | Short-duration Insurance Contracts, Accident Year 2012 [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	417	340	233	127	$ 27
Commercial - General Liability [Member] | Short-duration Insurance Contracts, Accident Year 2013 [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	377	257	135	$ 33
Commercial - General Liability [Member] | Short-duration Insurance Contracts, Accident Year 2014 [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	245	115	$ 29
Commercial - General Liability [Member] | Short-duration Insurance Contracts, Accident Year 2015 [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	132	$ 31
Commercial - General Liability [Member] | Short-duration Insurance Contracts, Accident Year 2016 [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 34

Claim and Claim Adjustment Ex95

Claim and Claim Adjustment Expense Reserves Short Duration Contracts - Net Strengthening or Releasing of Prior Accident Year Reserves Commercial - General Liability (Details) - Commercial - General Liability [Member] - USD ($) $ in Millions	12 Months Ended									24 Months Ended	36 Months Ended	48 Months Ended	60 Months Ended	72 Months Ended	84 Months Ended	96 Months Ended	108 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	$ (21)	$ (46)	$ 99
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development Prior Years	(7)	13	(54)
Net prior year claim and allocated claim adjustment expense reserve development, General Liability	(28)	(33)	45
Short-duration Insurance Contracts, Accident Year 2007 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	(8)	3	(14)	$ (41)	$ (10)	$ (29)	$ (39)	$ 5	$ (101)								$ (234)
Short-duration Insurance Contracts, Accident Year 2008 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	(9)	(13)	(19)	(1)	(14)	17	26	$ (7)								$ (20)
Short-duration Insurance Contracts, Accident Year 2009 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	3	(4)	(6)	(4)	(1)	(3)	$ 46								$ 31
Short-duration Insurance Contracts, Accident Year 2010 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	(16)	(20)	46	50	2	$ 31								$ 93
Short-duration Insurance Contracts, Accident Year 2011 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	10	1	46	30	$ (3)								$ 84
Short-duration Insurance Contracts, Accident Year 2012 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	(12)	(9)	16	$ 24								$ 19
Short-duration Insurance Contracts, Accident Year 2013 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	9	(11)	$ 30								$ 28
Short-duration Insurance Contracts, Accident Year 2014 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	1	$ 7								$ 8
Short-duration Insurance Contracts, Accident Year 2015 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	$ 1

Claim and Claim Adjustment Ex96

Claim and Claim Adjustment Expense Reserves Short Duration Contracts - Net Incurred Claims and Allocated Claim Adjustment Expenses Commercial - Workers Compensation (Details) - Commercial - Workers Compensation [Member] $ in Millions	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 ($)	Dec. 31, 2007USD ($)
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 1,068
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 5,875
Short-duration Insurance Contracts, Accident Year 2007 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	71,049
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 32
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 627	$ 608	$ 610	$ 604	$ 603	$ 603	$ 604	$ 596	$ 580	$ 568
Short-duration Insurance Contracts, Accident Year 2008 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	59,883
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 36
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 638	630	622	612	608	606	593	575	$ 558
Short-duration Insurance Contracts, Accident Year 2009 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	51,111
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 46
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 625	617	611	600	596	594	587	$ 583
Short-duration Insurance Contracts, Accident Year 2010 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	48,056
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 45
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 717	697	683	663	641	619	$ 576
Short-duration Insurance Contracts, Accident Year 2011 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	44,571
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 52
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 666	642	648	637	628	$ 593
Short-duration Insurance Contracts, Accident Year 2012 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	41,683
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 86
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 671	661	648	616	$ 589
Short-duration Insurance Contracts, Accident Year 2013 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	38,102
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 121
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 610	584	563	$ 528
Short-duration Insurance Contracts, Accident Year 2014 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	32,996
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 157
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 474	474	$ 459
Short-duration Insurance Contracts, Accident Year 2015 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	31,296
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 206
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 426	$ 416
Short-duration Insurance Contracts, Accident Year 2016 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	27,042
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 287
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 421

Claim and Claim Adjustment Ex97

Claim and Claim Adjustment Expense Reserves Short Duration Contracts - Net Cumulative Paid Claim and Claim Adjustment Expenses Commercial - Workers Compensation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008	Dec. 31, 2007
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years	$ 4,167	$ 4,089	$ 4,355
Liability for Unpaid Claims and Claims Adjustment Expense, Net	18,249	18,576	18,927	$ 19,117
Commercial - Workers Compensation [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	3,877
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	1,998
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years	2,334
Short-duration Insurance Contracts, Liability for Unpaid Claims and Claim Adjustment Expense, Other Reconciling Item	(30)
Short-duration Insurance Contracts, Liability for Unpaid Claims and Claims Adjustment Expense, Accumulated Unallocated Claim Adjustment Expense	4
Liability for Unpaid Claims and Claims Adjustment Expense, Net	4,306
Short-duration Insurance Contracts, Accident Year 2007 [Member] | Commercial - Workers Compensation [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	535	533	522	502	$ 471	$ 429	$ 390	$ 337	$ 246	$ 100
Short-duration Insurance Contracts, Accident Year 2008 [Member] | Commercial - Workers Compensation [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	520	505	489	461	425	381	323	233	$ 92
Short-duration Insurance Contracts, Accident Year 2009 [Member] | Commercial - Workers Compensation [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	516	495	468	435	381	315	223	$ 88
Short-duration Insurance Contracts, Accident Year 2010 [Member] | Commercial - Workers Compensation [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	565	531	500	433	352	245	$ 94
Short-duration Insurance Contracts, Accident Year 2011 [Member] | Commercial - Workers Compensation [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	515	471	432	353	245	$ 97
Short-duration Insurance Contracts, Accident Year 2012 [Member] | Commercial - Workers Compensation [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	465	411	338	229	$ 86
Short-duration Insurance Contracts, Accident Year 2013 [Member] | Commercial - Workers Compensation [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	366	297	211	$ 79
Short-duration Insurance Contracts, Accident Year 2014 [Member] | Commercial - Workers Compensation [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	213	157	$ 60
Short-duration Insurance Contracts, Accident Year 2015 [Member] | Commercial - Workers Compensation [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	130	$ 50
Short-duration Insurance Contracts, Accident Year 2016 [Member] | Commercial - Workers Compensation [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 52

Claim and Claim Adjustment Ex98

Claim and Claim Adjustment Expense Reserves Short Duration Contracts - Net Strengthening or Releasing of Prior Accident Year Reserves Commercial - Workers Compensation (Details) - Commercial - Workers Compensation [Member] - USD ($) $ in Millions	12 Months Ended									24 Months Ended	36 Months Ended	48 Months Ended	60 Months Ended	72 Months Ended	84 Months Ended	96 Months Ended	108 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	$ 125	$ 69	$ 125
Short-duration Insurance Contracts, Discounted Liabilities, Aggregate Discount	1	(4)	1
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development Prior Years	24	15	13
Net prior year claim and allocated claim adjustment expense reserve development, Workers' Compensation	150	80	139
Short-duration Insurance Contracts, Accident Year 2007 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	19	(2)	6	$ 1	$ 0	$ (1)	$ 8	$ 16	$ 12								$ 59
Short-duration Insurance Contracts, Accident Year 2008 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	8	8	10	4	2	13	18	$ 17								$ 80
Short-duration Insurance Contracts, Accident Year 2009 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	8	6	11	4	2	7	$ 4								$ 42
Short-duration Insurance Contracts, Accident Year 2010 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	20	14	20	22	22	$ 43								$ 141
Short-duration Insurance Contracts, Accident Year 2011 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	24	(6)	11	9	$ 35								$ 73
Short-duration Insurance Contracts, Accident Year 2012 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	10	13	32	$ 27								$ 82
Short-duration Insurance Contracts, Accident Year 2013 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	26	21	$ 35								$ 82
Short-duration Insurance Contracts, Accident Year 2014 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	0	$ 15								$ 15
Short-duration Insurance Contracts, Accident Year 2015 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	$ 10

Claim and Claim Adjustment Ex99

Claim and Claim Adjustment Expense Reserves Net prior year claim and allocated claim adjustment expense reserve development for International segment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Pretax (favorable) unfavorable net prior year claim and allocated claim adjustment expense reserve development, excluding Life & Group	$ (288)	$ (210)	$ (21)
International [Member]
Net prior year claim and allocated claim adjustment expense reserve development, Medical Professional Liability	(5)	(9)	(7)
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development, Other Professional Liability	12	(16)	(26)
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development, Liability	(30)	(17)	(13)
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development, Property & Marine	(34)	(29)	(4)
Net prior year claim and allocated claim adjustment expense reserve development, Other	(1)	17	(9)
Pretax (favorable) unfavorable net prior year claim and allocated claim adjustment expense reserve development, excluding Life & Group	$ (58)	$ (54)	$ (59)

Claim and Claim Adjustment E100

Claim and Claim Adjustment Expense Reserves Short Duration Contracts - International Reconciliation (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	$ 18,249	$ 18,576	$ 18,927	$ 19,117
International Excluding Hardy [Member] [Domain]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	881
Hardy [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	320
International [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	$ 1,201	$ 1,219

Claim and Claim Adjustment E101

Claim and Claim Adjustment Expense Reserves Short Duration Contracts - Net Incurred Claims and Allocated Claim Adjustment Expenses - International Excluding Hardy (Details) - International Excluding Hardy [Member] $ in Millions	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 ($)	Dec. 31, 2007USD ($)
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 484
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 2,342
Short-duration Insurance Contracts, Accident Year 2007 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	27,149
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 4
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 159	$ 160	$ 162	$ 164	$ 172	$ 181	$ 194	$ 213	$ 219	$ 204
Short-duration Insurance Contracts, Accident Year 2008 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	25,119
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 7
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 207	210	209	200	207	207	214	226	$ 223
Short-duration Insurance Contracts, Accident Year 2009 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	21,362
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 13
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 213	222	231	234	247	247	245	$ 249
Short-duration Insurance Contracts, Accident Year 2010 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	22,877
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 18
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 190	196	203	211	217	223	$ 226
Short-duration Insurance Contracts, Accident Year 2011 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	25,361
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 14
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 216	223	233	253	260	$ 259
Short-duration Insurance Contracts, Accident Year 2012 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	25,306
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 34
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 244	245	252	266	$ 259
Short-duration Insurance Contracts, Accident Year 2013 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	23,999
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 56
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 256	275	282	$ 281
Short-duration Insurance Contracts, Accident Year 2014 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	24,859
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 82
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 284	284	$ 269
Short-duration Insurance Contracts, Accident Year 2015 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	22,873
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 107
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 297	$ 282
Short-duration Insurance Contracts, Accident Year 2016 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	15,564
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 149
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 276

Claim and Claim Adjustment E102

Claim and Claim Adjustment Expense Reserves Short Duration Contracts - Net Cumulative Paid Claim and Claim Adjustment Expenses International Excluding Hardy (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008	Dec. 31, 2007
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years	$ 4,167	$ 4,089	$ 4,355
Liability for Unpaid Claims and Claims Adjustment Expense, Net	18,249	18,576	18,927	$ 19,117
International Excluding Hardy [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	1,521
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	821
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years	38
Short-duration Insurance Contracts, Liability for Unpaid Claims and Claims Adjustment Expense, Accumulated Unallocated Claim Adjustment Expense	22
Liability for Unpaid Claims and Claims Adjustment Expense, Net	881
Short-duration Insurance Contracts, Accident Year 2007 [Member] | International Excluding Hardy [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	152	150	148	144	$ 140	$ 133	$ 124	$ 112	$ 99	$ 31
Short-duration Insurance Contracts, Accident Year 2008 [Member] | International Excluding Hardy [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	190	172	165	151	143	135	126	84	$ 34
Short-duration Insurance Contracts, Accident Year 2009 [Member] | International Excluding Hardy [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	181	170	159	149	134	119	90	$ 38
Short-duration Insurance Contracts, Accident Year 2010 [Member] | International Excluding Hardy [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	160	151	143	130	115	93	$ 47
Short-duration Insurance Contracts, Accident Year 2011 [Member] | International Excluding Hardy [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	171	159	146	133	111	$ 44
Short-duration Insurance Contracts, Accident Year 2012 [Member] | International Excluding Hardy [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	176	161	142	109	$ 42
Short-duration Insurance Contracts, Accident Year 2013 [Member] | International Excluding Hardy [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	152	135	109	$ 49
Short-duration Insurance Contracts, Accident Year 2014 [Member] | International Excluding Hardy [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	145	119	$ 51
Short-duration Insurance Contracts, Accident Year 2015 [Member] | International Excluding Hardy [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	130	$ 55
Short-duration Insurance Contracts, Accident Year 2016 [Member] | International Excluding Hardy [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 64

Claim and Claim Adjustment E103

Claim and Claim Adjustment Expense Reserves Short Duration Contracts - Net Strengthening or Releasing of Prior Accident Year Reserves International Excluding Hardy (Details) - International Excluding Hardy [Member] - USD ($) $ in Millions	12 Months Ended									24 Months Ended	36 Months Ended	48 Months Ended	60 Months Ended	72 Months Ended	84 Months Ended	96 Months Ended	108 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016
Short-duration Insurance Contracts, Accident Year 2007 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	$ (1)	$ (2)	$ (2)	$ (8)	$ (9)	$ (13)	$ (19)	$ (6)	$ 15								$ (45)
Short-duration Insurance Contracts, Accident Year 2008 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	(3)	1	9	(7)	0	(7)	(12)	$ 3								$ (16)
Short-duration Insurance Contracts, Accident Year 2009 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	(9)	(9)	(3)	(13)	0	2	$ (4)								$ (36)
Short-duration Insurance Contracts, Accident Year 2010 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	(6)	(7)	(8)	(6)	(6)	$ (3)								$ (36)
Short-duration Insurance Contracts, Accident Year 2011 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	(7)	(10)	(20)	(7)	$ 1								$ (43)
Short-duration Insurance Contracts, Accident Year 2012 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	(1)	(7)	(14)	$ 7								$ (15)
Short-duration Insurance Contracts, Accident Year 2013 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	(19)	(7)	$ 1								$ (25)
Short-duration Insurance Contracts, Accident Year 2014 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	0	$ 15								$ 15
Short-duration Insurance Contracts, Accident Year 2015 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	$ 15

Claim and Claim Adjustment E104

Claim and Claim Adjustment Expense Reserves Short Duration Contracts - Net Incurred Claims and Allocated Claim Adjustment Expenses - International - Hardy (Details) - Hardy [Member] $ in Millions	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)	Dec. 31, 2012USD ($)
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 1,030
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	310
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	123
Short-duration Insurance Contracts, Accident Year 2007 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	15	$ 10	$ 16	$ 11	$ 7
Net Claim and Claim Adjustment Expense Reserves at Acquisition					5
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net					12
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 0
Number of Reported Claims per Million of Net Earned Premium	4,249
Short-duration Insurance Contracts, Accident Year 2008 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 13	13	12	11	(4)
Net Claim and Claim Adjustment Expense Reserves at Acquisition					18
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net					14
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 0
Number of Reported Claims per Million of Net Earned Premium	4,234
Short-duration Insurance Contracts, Accident Year 2009 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ (2)	1	(4)	6	1
Net Claim and Claim Adjustment Expense Reserves at Acquisition					11
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net					12
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 0
Number of Reported Claims per Million of Net Earned Premium	3,840
Short-duration Insurance Contracts, Accident Year 2010 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 50	44	50	46	(10)
Net Claim and Claim Adjustment Expense Reserves at Acquisition					46
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net					36
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 0
Number of Reported Claims per Million of Net Earned Premium	4,495
Short-duration Insurance Contracts, Accident Year 2011 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 132	134	130	130	0
Net Claim and Claim Adjustment Expense Reserves at Acquisition					121
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net					121
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ (2)
Number of Reported Claims per Million of Net Earned Premium	6,193
Short-duration Insurance Contracts, Accident Year 2012 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 110	117	110	102	69
Net Claim and Claim Adjustment Expense Reserves at Acquisition					33
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net					$ 102
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ (1)
Number of Reported Claims per Million of Net Earned Premium	6,758
Short-duration Insurance Contracts, Accident Year 2013 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 137	136	144	$ 127
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 0
Number of Reported Claims per Million of Net Earned Premium	7,392
Short-duration Insurance Contracts, Accident Year 2014 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 174	180	$ 182
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 7
Number of Reported Claims per Million of Net Earned Premium	7,656
Short-duration Insurance Contracts, Accident Year 2015 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 176	$ 187
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 18
Number of Reported Claims per Million of Net Earned Premium	7,669
Short-duration Insurance Contracts, Accident Year 2016 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 225
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 101
Number of Reported Claims per Million of Net Earned Premium	5,274

Claim and Claim Adjustment E105

Claim and Claim Adjustment Expense Reserves Short Duration Contracts – Net Cumulative Paid Claim and Claim Adjustment Expenses - International - Hardy (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Short Duration Contracts Net Cumulative Paid Claim Adjustment Expenses [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years	$ 4,167	$ 4,089	$ 4,355
Liability for Unpaid Claims and Claims Adjustment Expense, Net	18,249	18,576	18,927	$ 19,117
Hardy [Member]
Short Duration Contracts Net Cumulative Paid Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	720
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	310
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years	3
Short-duration Insurance Contracts, Liability for Unpaid Claims and Claims Adjustment Expense, Accumulated Unallocated Claim Adjustment Expense	7
Liability for Unpaid Claims and Claims Adjustment Expense, Net	320
Hardy [Member] | Short-duration Insurance Contracts, Accident Year 2007 [Member]
Short Duration Contracts Net Cumulative Paid Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	14	14	14	14	$ 3
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net					12
Hardy [Member] | Short-duration Insurance Contracts, Accident Year 2008 [Member]
Short Duration Contracts Net Cumulative Paid Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	11	10	10	14	3
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net					14
Hardy [Member] | Short-duration Insurance Contracts, Accident Year 2009 [Member]
Short Duration Contracts Net Cumulative Paid Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	(4)	(4)	(4)	(2)	1
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net					12
Hardy [Member] | Short-duration Insurance Contracts, Accident Year 2010 [Member]
Short Duration Contracts Net Cumulative Paid Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	45	43	41	34	19
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net					36
Hardy [Member] | Short-duration Insurance Contracts, Accident Year 2011 [Member]
Short Duration Contracts Net Cumulative Paid Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	127	123	119	80	29
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net					121
Hardy [Member] | Short-duration Insurance Contracts, Accident Year 2012 [Member]
Short Duration Contracts Net Cumulative Paid Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	104	107	98	78	14
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net					$ 102
Hardy [Member] | Short-duration Insurance Contracts, Accident Year 2013 [Member]
Short Duration Contracts Net Cumulative Paid Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	125	119	100	$ 37
Hardy [Member] | Short-duration Insurance Contracts, Accident Year 2014 [Member]
Short Duration Contracts Net Cumulative Paid Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	139	121	$ 55
Hardy [Member] | Short-duration Insurance Contracts, Accident Year 2015 [Member]
Short Duration Contracts Net Cumulative Paid Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	97	$ 29
Hardy [Member] | Short-duration Insurance Contracts, Accident Year 2016 [Member]
Short Duration Contracts Net Cumulative Paid Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 62

Claim and Claim Adjustment E106

Claim and Claim Adjustment Expense Reserves Short Duration Contracts – Net Strengthening or Releasing of Prior Accident Year Reserves - International - Hardy (Details) - Hardy [Member] - USD ($) $ in Millions	12 Months Ended					24 Months Ended	36 Months Ended	48 Months Ended	60 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016
Short-duration Insurance Contracts, Accident Year 2007 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	$ 5	$ (6)	$ 5	$ (1)	$ 7				$ 10
Short-duration Insurance Contracts, Accident Year 2008 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	0	1	1	(3)	(4)				(5)
Short-duration Insurance Contracts, Accident Year 2009 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	(3)	5	(10)	(6)	1				(13)
Short-duration Insurance Contracts, Accident Year 2010 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	6	(6)	4	10	(10)				4
Short-duration Insurance Contracts, Accident Year 2011 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	(2)	4	0	9	$ 0				$ 11
Short-duration Insurance Contracts, Accident Year 2012 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	(7)	7	8	$ 0				$ 8
Short-duration Insurance Contracts, Accident Year 2013 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	1	(8)	$ 17				$ 10
Short-duration Insurance Contracts, Accident Year 2014 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	(6)	$ (2)				$ (8)
Short-duration Insurance Contracts, Accident Year 2015 [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development	$ (11)

Claim and Claim Adjustment E107

Claim and Claim Adjustment Expense Reserves Short Duration Contracts - Consolidated Reconciliation (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	$ 18,249	$ 18,576	$ 18,927	$ 19,117
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	4,094
Total Gross Carried Claim and Claim Adjustment Expense Reserves	22,343	22,663	$ 23,271	$ 24,089
Specialty [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	5,404	5,568
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	745
Total Gross Carried Claim and Claim Adjustment Expense Reserves	6,149	6,269
Commercial [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	8,305	8,576
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	589
Total Gross Carried Claim and Claim Adjustment Expense Reserves	8,894	9,183
International [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	1,201	1,219
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	127
Total Gross Carried Claim and Claim Adjustment Expense Reserves	1,328	1,347
Corporate and Other [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	230	283
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	2,384
Total Gross Carried Claim and Claim Adjustment Expense Reserves	2,614	2,644
Life and Group Non-Core [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	3,109	2,930
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	249
Total Gross Carried Claim and Claim Adjustment Expense Reserves	$ 3,358	$ 3,220

Claim and Claim Adjustment E108

Claim and Claim Adjustment Expense Reserves Short-Duration Contracts - Historical Claims Duration (Details)	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008	Dec. 31, 2007
Specialty - Medical Professional Liability [Member]
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Short-duration Insurance Contracts, Historical Claims Duration, Year One										3.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two									18.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three								22.30%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four							19.60%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five						12.70%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six					8.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven				5.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight			4.80%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine		3.70%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten	0.30%
Short-Duration Insurance Contracts, Historical Claims Duration, Net	97.70%
Specialty - Other Professional and Management Liability [Member]
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Short-duration Insurance Contracts, Historical Claims Duration, Year One										5.70%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two									20.60%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three								21.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four							17.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five						10.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six					6.30%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven				5.60%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight			3.80%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine		1.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten	3.20%
Short-Duration Insurance Contracts, Historical Claims Duration, Net	95.10%
Specialty - Surety [Member]
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Short-duration Insurance Contracts, Historical Claims Duration, Year One										23.40%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two									32.80%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three								20.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four							8.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five						3.70%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six					1.50%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven				(0.70%)
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight			2.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine		1.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten	2.00%
Short-Duration Insurance Contracts, Historical Claims Duration, Net	94.80%
Commercial - Auto [Member]
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Short-duration Insurance Contracts, Historical Claims Duration, Year One										27.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two									23.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three								18.30%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four							13.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five						9.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six					3.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven				1.30%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight			0.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine		0.30%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten	0.30%
Short-Duration Insurance Contracts, Historical Claims Duration, Net	97.60%
Commercial - General Liability [Member]
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Short-duration Insurance Contracts, Historical Claims Duration, Year One										5.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two									16.30%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three								20.50%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four							20.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five						15.30%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six					8.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven				4.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight			2.70%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine		1.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten	1.30%
Short-Duration Insurance Contracts, Historical Claims Duration, Net	94.50%
Commercial - Workers Compensation [Member]
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Short-duration Insurance Contracts, Historical Claims Duration, Year One										13.50%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two									21.40%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three								14.60%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four							10.50%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five						7.50%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six					5.70%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven				4.60%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight			3.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine		2.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten	0.30%
Short-Duration Insurance Contracts, Historical Claims Duration, Net	83.20%
International Excluding Hardy [Member]
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Short-duration Insurance Contracts, Historical Claims Duration, Year One										19.50%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two									27.40%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three								12.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four							6.80%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five						5.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six					4.50%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven				4.80%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight			3.70%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine		5.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten	1.30%
Short-Duration Insurance Contracts, Historical Claims Duration, Net	91.00%
Hardy [Member]
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Short-duration Insurance Contracts, Historical Claims Duration, Year One										25.70%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two									40.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three								12.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four							4.40%
Short-Duration Insurance Contracts, Historical Claims Duration, Net	83.10%

Claim and Claim Adjustment E109

Claim and Claim Adjustment Expense Reserves (Impact of Loss Portfolio Transfer on the Consolidated Statement of Operations) (Details) - Loss Portfolio Transfer [Member] - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Net AEP adverse development before consideration of LPT	$ 200	$ 200	$ 150	$ 0
Retroactive reinsurance benefit recognized		(107)	(85)	(13)
Pretax impact of deferred retroactive reinsurance benefit		$ 93	$ 65	$ (13)

Legal Proceedings, Commitmen110

Legal Proceedings, Commitments and Contingencies, and Guarantees (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Legal Proceedings, Commitments and Contingencies, and Guarantees [Line Items]
Reduction to Earned Premium due to the Small Business Premium Rate Adjustment Contingency	$ 16
Expected Premium Refund Related to the Small Business Premium Rate Adjustment Contingency	30
Property Lease Guarantee [Member]
Legal Proceedings, Commitments and Contingencies, and Guarantees [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	11
Guarantee and Indemnification [Member]
Legal Proceedings, Commitments and Contingencies, and Guarantees [Line Items]
Guarantor Obligations, Current Carrying Value	5	$ 5
Guarantee agreement [Member]
Legal Proceedings, Commitments and Contingencies, and Guarantees [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	375
Indemnification Agreement [Member]
Legal Proceedings, Commitments and Contingencies, and Guarantees [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	258
Guarantee Obligations [Member]
Legal Proceedings, Commitments and Contingencies, and Guarantees [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 1,900

Reinsurance (Narrative) (Detail

Reinsurance (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Funds held under reinsurance agreements, liability	$ 3,000	$ 3,200
Reinsurance recoveries reported in insurance claims and policyholders' benefits reported on the Consolidated Statement of Operations	3,016	2,601	$ 1,379
Subsidiaries of Berkshire Hathaway Group [Member]
Largest Recoverables From Single Reinsurer	2,353
Gateway Rivers Insurance Company [Member]
Largest Recoverables From Single Reinsurer	350
Subsidiaries of Wilton Re[Member]
Largest Recoverables From Single Reinsurer	212
Significant Captive Program [Member]
Direct and ceded earned premiums	3,865	3,344	2,643
Reinsurance recoveries reported in insurance claims and policyholders' benefits reported on the Consolidated Statement of Operations	$ 2,621	$ 2,282	$ 1,458

Reinsurance (Components of Rein

Reinsurance (Components of Reinsurance Receivables) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reinsurance receivables related to insurance reserves
Ceded claim and claim adjustment expenses	$ 4,094	$ 4,087	$ 4,344	$ 4,972
Ceded future policy benefits	212	207
Reinsurance receivables related to paid losses	147	197
Reinsurance receivables	4,453	4,491
Allowance for uncollectible reinsurance	(37)	(38)
Reinsurance receivables, net of allowance for uncollectible reinsurance	$ 4,416	$ 4,453

Reinsurance (Components of Earn

Reinsurance (Components of Earned Premiums) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Direct premiums earned	$ 10,886	$ 10,351	$ 9,960
Assumed premiums earned	308	324	325
Ceded premiums earned	4,270	3,754	3,073
Net earned premiums	6,924	6,921	7,212
Property and Casualty Insurance [Member]
Direct premiums earned	10,400	9,853	9,452
Assumed premiums earned	258	274	277
Ceded premiums earned	4,270	3,754	3,073
Net earned premiums	6,388	6,373	6,656
Long term care Insurance Product Line [Member]
Direct premiums earned	486	498	508
Assumed premiums earned	50	50	48
Ceded premiums earned	0	0	0
Net earned premiums	$ 536	$ 548	$ 556
Percentage of assumed premiums earned to net premiums earned [Member]
Percentage of assumed premium earned to premium earned net	4.40%	4.70%	4.50%
Percentage of assumed premiums earned to net premiums earned [Member] | Property and Casualty Insurance [Member]
Percentage of assumed premium earned to premium earned net	4.00%	4.30%	4.20%
Percentage of assumed premiums earned to net premiums earned [Member] | Long term care Insurance Product Line [Member]
Percentage of assumed premium earned to premium earned net	9.30%	9.10%	8.60%

Reinsurance (Components of Writ

Reinsurance (Components of Written Premiums) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Direct premiums written	$ 10,946	$ 10,345	$ 9,787
Assumed premiums written	297	319	325
Ceded premiums written	4,255	3,702	3,024
Net written premiums	6,988	6,962	7,088
Property and Casualty Insurance [Member]
Direct premiums written	10,451	9,852	9,283
Assumed premiums written	245	270	276
Ceded premiums written	4,255	3,702	3,024
Net written premiums	6,441	6,420	6,535
Long term care Insurance Product Line [Member]
Direct premiums written	495	493	504
Assumed premiums written	52	49	49
Ceded premiums written	0	0	0
Net written premiums	$ 547	$ 542	$ 553
Percentage of assumed premiums written to net premiums written [Member]
Percentage of assumed premium written to premium written net	4.30%	4.60%	4.60%
Percentage of assumed premiums written to net premiums written [Member] | Property and Casualty Insurance [Member]
Percentage of assumed premium written to premium written net	3.80%	4.20%	4.20%
Percentage of assumed premiums written to net premiums written [Member] | Long term care Insurance Product Line [Member]
Percentage of assumed premium written to premium written net	9.50%	9.00%	8.90%

Debt (Narrative) (Details)

Debt (Narrative) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Debt Disclosure [Abstract]
Federal Home Loan Bank Stock	$ 5
Federal Home Loan Bank, Advances, General Debt Obligations, Maximum Amount Available	111
Federal Home Loan Bank, Advances, Branch of FHLB Bank, Amount of Advances	0	$ 0
Line of Credit, Current borrowing capacity	250
Additional borrowing capacity available	100
Line of Credit, Minimum Net Worth Required for Compliance	8,700
Line of Credit, Amount Outstanding	$ 0	$ 0

Debt (Schedule of debt instrume

Debt (Schedule of debt instruments) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Long term debt	$ 2,710	$ 2,210
Total debt	2,710	2,560
Senior notes 6.950%, face amount $150, due January 15, 2018
Long term debt	150	150
Senior notes 7.350%, face amount $350, due November 15, 2019
Long term debt	349	349
Senior notes 5.875%, face amount $500, due August 15, 2020
Long term debt	498	497
Senior notes 5.750%, face amount $400, due August 15, 2021
Long term debt	398	397
Senior Notes, 3.950%, face amount of $550, due May 15, 2024
Long term debt	546	546
Senior Notes, 4.500%, face amount of $500, due March 1, 2026
Long term debt	498	0
Debenture of CNAF, 7.250%, face amount of $243, due November 15, 2023
Long term debt	241	241
Subordinated variable rate debt of Hardy, face amount of $30, due September 15, 2036
Long term debt	30	30
Senior notes 6.500%, face amount of $350, due August 15, 2016 [Member]
Short term debt	$ 0	$ 350

Debt (Maturity of debt) (Detail

Debt (Maturity of debt) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Debt Disclosure [Abstract]
Repayments of principal in the next twelve months	$ 0
Repayments of principal in year two	150
Repayments of principal in year three	350
Repayments of principal in year four	500
Repayments of principal in year five	400
Repayments of principal after year five	1,323
Less discount	(13)
Total debt	$ 2,710	$ 2,560

Benefit Plans Benefit Plans (Na

Benefit Plans Benefit Plans (Narrative) (details) - USD ($) $ in Millions	6 Months Ended				12 Months Ended
	Dec. 31, 2015	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan, Curtailments						$ 55
Lump sum settlement acceptance rate by retirement plan participants			20.00%				20.00%
Lump sum pension settlement payment							$ 253
Settlement loss							84
Curtailment gain							86
Future capital call commitments for limited partnership investments					$ 380
Percentage of limited partnerships employing hedge fund strategies focused on fixed income and equity investments	70.00%				68.00%	70.00%
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent					50.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Match					70.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay					6.00%
Defined Contribution Plan, Employers Matching Contribution, Vesting Period in Years					5 years
Company Contribution of Eligible Compensation, Depending on Age, Percent					3% or 5%
Benefit expense for the Company's savings plan					$ 75	$ 71	$ 69
Additional Contribution, Management Discretion [Member]
Defined Contribution Plan, Employer Matching Contribution, Percent of Match					80.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay					6.00%
Defined Contribution Plan, Employers Matching Contribution, Vesting Period in Years					5 years
Defined Contribution Plan, Employer Discretionary Contribution Amount, Percent					2.00%
First Year of Employment [Member]
Defined Contribution Plan, Employer Matching Contribution, Percent of Match					35.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay					6.00%
Pension Plans, Defined Benefit [Member]
Settlement through group annuity purchase					$ 88	0
Decrease in Benefit Obligation due to settlement					$ 86	0
Discount rate	4.00%	3.85%			4.15%		4.65%
Settlement loss					$ 0	0	$ 84
Defined benefit plan, accumulated benefit obligation	$ 2,821				2,729	$ 2,821
Future capital call commitments for limited partnership investments					$ 113
Percentage of limited partnerships employing hedge fund strategies focused on fixed income and equity investments	87.00%				86.00%	87.00%
Limited partnership equity related hedge fund strategy plan assets					57.00%
Limited partnership hedge fund multi strategy plan assets					38.00%
Limited partnership hedge fund strategy distressed investments plan assets					5.00%
Defined Benefit Plans, Estimated Future Employer Contributions in Next Fiscal Year					$ 12
Cost of Living Adjustment [Member]
Assumptions used in calculating assumed health care cost trend rate					4.00%
Employer Subsidy on Health Care Costs [Member]
Assumptions used in calculating assumed health care cost trend rate					4.00%
Other Postretirement Benefit Plan [Member]
Settlement through group annuity purchase					$ 0	$ 0
Decrease in Benefit Obligation due to settlement					$ 0	$ 0
Discount rate			3.10%	3.60%	2.75%	2.50%
Curtailment gain					$ 0	$ 0	$ 86
Defined benefit plan, health care cost trend rate assumed for next fiscal year					4.00%	4.00%	4.00%
Defined Benefit Plans, Estimated Future Employer Contributions in Next Fiscal Year					$ 3
Equity securities [Member]
Defined Benefit Plan, Target Plan Asset Allocations Range Minimum					40.00%
Defined Benefit Plan, Target Plan Asset Allocations Range Maximum					60.00%

Benefit Plans (Funded Status) (

Benefit Plans (Funded Status) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]
Defined Benefit Plan, Assets for Plan Benefits	$ 2,193	$ 2,267
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at January 1	2,821	3,019
Service cost	0	4	$ 9
Interest cost	113	112	132
Participants' contributions	0	0
Plan amendments	0	(55)
Actuarial (gain) loss	68	(79)
Benefits paid	(173)	(173)
Foreign currency translation and other	(14)	(7)
Decrease in Benefit Obligation due to settlement	(86)	0
Benefit obligation at December 31	2,729	2,821	3,019
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at January 1	2,267	2,456
Actual return on plan assets	193	(18)
Company contributions	9	10
Participants' contributions	0	0
Benefits paid	(173)	(173)
Foreign currency translation and other	(15)	(8)
Settlement through group annuity purchase	(88)	0
Fair value of plan assets at December 31	2,193	2,267	2,456
Defined Benefit Plan, Funded Status of Plan [Abstract]
Funded status	(536)	(554)
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]
Defined Benefit Plan, Assets for Plan Benefits	4	12
Other liabilities	(540)	(566)
Net amount recognized on balance sheets	(536)	(554)
Amounts recognized in Accumulated other comprehensive income not yet recognized in net periodic cost (benefit)[Abstract]
Prior service credit	0	0
Net actuarial (gain) loss	999	999
Net amount recognized in Accumulated other comprehensive income	999	999
Other Postretirement Benefit Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at January 1	23	29
Service cost	0	0
Interest cost	0	1	1
Participants' contributions	4	4
Plan amendments	0	0
Actuarial (gain) loss	(6)	(3)
Benefits paid	(7)	(8)
Foreign currency translation and other	1	0
Decrease in Benefit Obligation due to settlement	0	0
Benefit obligation at December 31	15	23	29
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at January 1	0	0
Actual return on plan assets	0	0
Company contributions	3	4
Participants' contributions	4	4
Benefits paid	(7)	(8)
Foreign currency translation and other	0	0
Settlement through group annuity purchase	0	0
Fair value of plan assets at December 31	0	0	$ 0
Defined Benefit Plan, Funded Status of Plan [Abstract]
Funded status	(15)	(23)
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]
Defined Benefit Plan, Assets for Plan Benefits	0	0
Other liabilities	(15)	(23)
Net amount recognized on balance sheets	(15)	(23)
Amounts recognized in Accumulated other comprehensive income not yet recognized in net periodic cost (benefit)[Abstract]
Prior service credit	(4)	(6)
Net actuarial (gain) loss	(3)	3
Net amount recognized in Accumulated other comprehensive income	$ (7)	$ (3)

Benefit Plans (Components of ne

Benefit Plans (Components of net periodic cost (benefit)) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Settlement loss			$ 84
Curtailment gain			(86)
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 0	$ 4	9
Interest cost on projected benefit obligation	113	112	132
Expected return on plan assets	(160)	(174)	(191)
Amortization of net actuarial (gain) loss	37	34	25
Settlement loss	0	0	84
Net periodic (benefit) cost	(10)	(24)	59
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0
Interest cost on projected benefit obligation	0	1	1
Amortization of prior service credit	(2)	(3)	(10)
Amortization of net actuarial (gain) loss	0	1	1
Curtailment gain	0	0	(86)
Net periodic (benefit) cost	$ (2)	$ (1)	$ (94)

Benefit Plans (Schedule of amou

Benefit Plans (Schedule of amounts recognized in Other comprehensive income) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, before Tax, [Abstract]
Amounts arising during the period	$ (29)	$ (111)	$ (337)
Curtailment and other	0	56	(81)
Settlement through group annuity purchase	0	0	84
Reclassification adjustment relating to prior service cost (credit)	(2)	(3)	(10)
Reclassification adjustment relating to actuarial (gain) loss	37	35	26
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Settlements Through Group Annuity Purchase, before Tax	(2)	0	0
Total increase (decrease) in Other comprehensive income	$ 4	$ (23)	$ (318)

Benefit Plans (Schedule of esti

Benefit Plans (Schedule of estimated amounts to be recognized from Accumulated other comprehensive income into net periodic cost (benefit) during next fiscal year) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service cost (credit)	$ 0
Amortization of net actuarial (gain) loss	36
Total estimated amounts to be recognized	36
Other Postretirement Benefit Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service cost (credit)	(2)
Amortization of net actuarial (gain) loss	0
Total estimated amounts to be recognized	$ (2)

Benefit Plans (Actuarial Assump

Benefit Plans (Actuarial Assumptions for Benefit Obligations) (Details)	Dec. 31, 2016	Dec. 31, 2015
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.95%	4.15%
Expected long term rate of return	7.50%	7.50%
Other Postretirement Benefit Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	2.75%	2.75%

Benefit Plans (Actuarial Ass124

Benefit Plans (Actuarial Assumptions for Net Cost or Benefit) (Details)	6 Months Ended				12 Months Ended
	Dec. 31, 2015	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	4.00%	3.85%			4.15%		4.65%
Expected long term rate of return					7.50%	7.50%	7.50%
Rate of compensation increases						3.92%	3.99%
Other Postretirement Benefit Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate			3.10%	3.60%	2.75%	2.50%

Benefit Plans (Fair Value of Pl

Benefit Plans (Fair Value of Plan Assets Measured on a Recurring Basis) (Details) - USD ($) $ in Millions		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Assets for Plan Benefits		$ 2,193	$ 2,267
Corporate and other bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		510	465
Corporate and other bonds [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Corporate and other bonds [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		500	455
Corporate and other bonds [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		10	10	$ 15
States, municipalities and political subdivisions [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		63	106
States, municipalities and political subdivisions [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
States, municipalities and political subdivisions [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		63	106
States, municipalities and political subdivisions [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Residential mortgage-backed [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		109	133
Residential mortgage-backed [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Residential mortgage-backed [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		109	133
Residential mortgage-backed [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Commercial Mortgage Backed Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		66	69
Commercial Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Commercial Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		66	69
Commercial Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Other asset-backed [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		4	11
Other asset-backed [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Other asset-backed [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		4	11
Other asset-backed [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Total asset-backed [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		179	213
Total asset-backed [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Total asset-backed [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		179	213
Total asset-backed [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Fixed Maturities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		752	784
Fixed Maturities [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Fixed Maturities [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		742	774
Fixed Maturities [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		10	10	15
Equity securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		468	443
Equity securities [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		363	336
Equity securities [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		105	107
Equity securities [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Derivative Financial Instruments, Assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	1
Derivative Financial Instruments, Assets [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	1
Derivative Financial Instruments, Assets [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Derivative Financial Instruments, Assets [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Short-term Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		46	52
Short-term Investments [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		11	24
Short-term Investments [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		35	28
Short-term Investments [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Other assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		37	52
Other assets [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Other assets [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		37	52
Other assets [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Cash [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		14
Cash [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		14
Cash [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0
Cash [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0
Total assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		1,317	1,332
Total assets [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		388	361
Total assets [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		919	961
Total assets [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		10	10	$ 15
Total limited partnerships [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Assets for Plan Benefits	[1]	$ 876	$ 935
[1]	(1) In accordance with Subtopic 820-10, certain investments that are measured at fair value using the net asset value per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the statement of financial position.

Benefit Plans (Reconciliation o

Benefit Plans (Reconciliation of Level 3 Plan Assets) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Fixed Maturities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at January 1	$ 784
Fair value of plan assets at December 31	752	$ 784
Corporate and other bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at January 1	465
Fair value of plan assets at December 31	510	465
Total assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at January 1	1,332
Fair value of plan assets at December 31	1,317	1,332
Fair Value, Inputs, Level 3 [Member] | Fixed Maturities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at January 1	10	15
Defined Benefit Plan, Actual Return on Plan Assets Still Held	0	0
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period	0	0
Defined Benefit Plan, Purchases, Sales, and Settlements	0	0
Defined Benefit Plan, Net transfers into (out of) Level 3	0	(5)
Fair value of plan assets at December 31	10	10
Fair Value, Inputs, Level 3 [Member] | Corporate and other bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at January 1	10	15
Defined Benefit Plan, Actual Return on Plan Assets Still Held	0	0
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period	0	0
Defined Benefit Plan, Purchases, Sales, and Settlements	0	0
Defined Benefit Plan, Net transfers into (out of) Level 3	0	(5)
Fair value of plan assets at December 31	10	10
Fair Value, Inputs, Level 3 [Member] | Total assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at January 1	10	15
Defined Benefit Plan, Actual Return on Plan Assets Still Held	0	0
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period	0	0
Defined Benefit Plan, Purchases, Sales, and Settlements	0	0
Defined Benefit Plan, Net transfers into (out of) Level 3	0	(5)
Fair value of plan assets at December 31	$ 10	$ 10

Benefit Plans (Estimated Future

Benefit Plans (Estimated Future Minimum Benefit Payments to Participants) (Details) $ in Millions	Dec. 31, 2016USD ($)
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Benefit Payments in Year One	$ 178
Defined Benefit Plan, Expected Future Benefit Payments in Year Two	178
Defined Benefit Plan, Expected Future Benefit Payments in Year Three	177
Defined Benefit Plan, Expected Future Benefit Payments in Year Four	178
Defined Benefit Plan, Expected Future Benefit Payments in Year Five	178
Defined Benefit Plan, Expected Future Benefit Payments in Five Fiscal Years Thereafter	883
Other Postretirement Benefit Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Benefit Payments in Year One	3
Defined Benefit Plan, Expected Future Benefit Payments in Year Two	2
Defined Benefit Plan, Expected Future Benefit Payments in Year Three	2
Defined Benefit Plan, Expected Future Benefit Payments in Year Four	2
Defined Benefit Plan, Expected Future Benefit Payments in Year Five	2
Defined Benefit Plan, Expected Future Benefit Payments in Five Fiscal Years Thereafter	$ 3

Stock-Based Compensation (Narra

Stock-Based Compensation (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	11,000,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	3,700,000
Allocated Share-based Compensation Expense	$ 36	$ 14	$ 11
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense	12	$ 5	4
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized	$ 32
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	1 year 10 months 24 days
Restricted Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Period Following Date of Grant, in Years	two or three
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Period Following Date of Grant, in Years	4
Range of Shares Initially Granted Payable Based Upon Attainment of Specific Annual Performance Goals	0% to 100%
Stock Appreciation Rights (SARs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Period Following Date of Grant, in Years	4
Stock Options and SARs, Maximum Term Following Date of Grant, in Years	10
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	0	0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number	1,000,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number	1,000,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number	1,000,000
Fair Value of Stock Based Awards Vested			$ 1
Long Term Incentive Plan [Member] | Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Shares Initially Granted Payable Based Upon Attainment of Specific Annual Performance Goals	0% to 200%
Measurement Period of Specific Annual Performance Goals, in Years	3
Annual Performance Share Plan [Member] | Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Shares Initially Granted Payable Based Upon Attainment of Specific Annual Performance Goals	0% to 200%
Measurement Period of Specific Annual Performance Goals, in Years	1
Cliff Vesting Period Following Date of Grant	2
Special Supplemental Equity Awards [Member] | Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Service Based Vesting Period	2

Stock-Based Compensation (Restr

Stock-Based Compensation (Restricted shares, performance-based restricted share units and performance share unit activity) (Details)	12 Months Ended
	Dec. 31, 2016$ / sharesshares
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Number of nonvested awards at January 1 | shares	735,263
Weighted average grant date fair value of nonvested awards at January 1 | $ / shares	$ 36.53
Number of awards granted | shares	2,545,624
Weighted average grant date fair value of awards granted | $ / shares	$ 32.27
Number of awards vested | shares	(371,443)
Weighted average grant date fair value of awards vested | $ / shares	$ 33.33
Number of awards forfeited, canceled or expired | shares	(186,932)
Weighted average grant date fair value of awards forfeited, canceled or expired | $ / shares	$ 32.80
Performance-based adjustment | shares	(590,730)
Weighted average grant date fair value of performance based adjustment | $ / shares	$ 33.10
Number of nonvested awards at December 31 | shares	2,131,782
Weighted average grant date fair value of nonvested awards at December 31 | $ / shares	$ 33.28

Schedule of Other Intangible As

Schedule of Other Intangible Assets (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Amortization of deferred acquisition costs	$ 1,235	$ 1,540	$ 1,317
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	1
Finite-Lived Intangible Assets, Amortization Expense, Year Two	1
Finite-Lived Intangible Assets, Amortization Expense, Year Three	1
Finite-Lived Intangible Assets, Amortization Expense, Year Four	1
Finite-Lived Intangible Assets, Amortization Expense, Year Five	1
International [Member]
Amortization of deferred acquisition costs	174	168	204
International [Member] | Other Intangible Assets [Member]
Amortization of deferred acquisition costs			2
Amortization expense included in other operating expenses	$ 1	$ 1	$ 1

Schedule of Other Intangible131

Schedule of Other Intangible Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets	$ 64	$ 76
Indefinite-lived intangible assets	59	68
Intangible Assets, Gross (Excluding Goodwill)	123	144
Accumulated Amortization	54	63
Lloyds syndicate capacity [Member]
Indefinite-lived intangible assets	43	52
Agency Force [Member]
Indefinite-lived intangible assets	16	16
Value of business acquired [Member]
Finite-Lived Intangible Assets	48	57
Accumulated Amortization	$ 48	57
Trade name [Member]
Economic useful life measured in years	8 years
Finite-Lived Intangible Assets	$ 6	7
Accumulated Amortization	$ 3	3
Distribution channel [Member]
Economic useful life measured in years	15 years
Finite-Lived Intangible Assets	$ 10	12
Accumulated Amortization	$ 3	$ 3
Minimum [Member] | Value of business acquired [Member]
Economic useful life measured in years	1 year
Maximum [Member] | Value of business acquired [Member]
Economic useful life measured in years	4 years

Operating Leases (Narrative) (D

Operating Leases (Narrative) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Leases, Operating [Abstract]
Operating Leases, Rent Expense	$ 60	$ 46	$ 55
Operating Leases, Income Statement, Sublease Revenue			$ 1
Minimum Lease Payments, Sale Leaseback Transactions, Next Twelve Months	10
Minimum Lease Payments, Sale Leaseback Transactions, within Two Years	$ 4

Operating Leases (Future Minimu

Operating Leases (Future Minimum Lease Payments) (Details) $ in Millions	Dec. 31, 2016USD ($)
Leases, Operating [Abstract]
Operating Leases, Future Minimum Payments Due, Next Twelve Months	$ 48
Operating Leases, Future Minimum Payments, Due in Two Years	37
Operating Leases, Future Minimum Payments, Due in Three Years	30
Operating Leases, Future Minimum Payments, Due in Four Years	33
Operating Leases, Future Minimum Payments, Due in Five Years	34
Operating Leases, Future Minimum Payments, Due Thereafter	244
Operating Leases, Future Minimum Payments Due	$ 426

Stockholders' Equity and Sta134

Stockholders' Equity and Statutory Accounting Practices (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Stockholders' Equity and Statutory Accounting Practices [Abstract]
Increase in statutory capital and surplus due to prescribed practice	$ 67	$ 90
Statutory Accounting Practices, Statutory Amount Available for Dividend Payment Before Consideration of Statutory Dividends Paid in the preceding twelve months	1,075
Statutory Accounting Practices, Dividends Paid in the preceding twelve months	$ 765
Capital Required for Capital Adequacy to Risk Weighted Assets	270.00%	266.00%

Stockholders' Equity and Sta135

Stockholders' Equity and Statutory Accounting Practices Combined statutory capital and surplus and net income (loss) (Details) - Combined Continental Casualty Companies [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statutory Accounting Practices [Line Items]
Statutory capital and surplus	$ 10,748	$ 10,723
Statutory net income (loss)	$ 1,033	$ 1,148	$ 914

Accumulated Other Comprehens136

Accumulated Other Comprehensive Income (Loss) by Component (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), beginning balance	$ (315)	$ 400
Other comprehensive income (loss), before reclassifications	163	(793)
Amounts reclassified from accumulated other comprehensive income (loss) after tax (expense) benefit	21	(78)
Other comprehensive income (loss) after tax (expense) benefit	142	(715)
Accumulated other comprehensive income (loss), ending balance	(173)	(315)
Reclassification from AOCI, Current Period, Tax	(7)	49
Tax (expense) benefit on other comprehensive income (loss)	(121)	295
Net unrealized gains (losses) on investments with OTTI losses [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), beginning balance	27	36
Other comprehensive income (loss), before reclassifications	9	(23)
Amounts reclassified from accumulated other comprehensive income (loss) after tax (expense) benefit	6	(14)
Other comprehensive income (loss) after tax (expense) benefit	3	(9)
Accumulated other comprehensive income (loss), ending balance	30	27
Reclassification from AOCI, Current Period, Tax	(3)	8
Tax (expense) benefit on other comprehensive income (loss)	(1)	5
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), beginning balance	390	942
Other comprehensive income (loss), before reclassifications	290	(595)
Amounts reclassified from accumulated other comprehensive income (loss) after tax (expense) benefit	38	(43)
Other comprehensive income (loss) after tax (expense) benefit	252	(552)
Accumulated other comprehensive income (loss), ending balance	642	390
Reclassification from AOCI, Current Period, Tax	(16)	30
Tax (expense) benefit on other comprehensive income (loss)	(117)	282
Pension and postretirement benefits [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), beginning balance	(648)	(633)
Other comprehensive income (loss), before reclassifications	(22)	(36)
Amounts reclassified from accumulated other comprehensive income (loss) after tax (expense) benefit	(23)	(21)
Other comprehensive income (loss) after tax (expense) benefit	1	(15)
Accumulated other comprehensive income (loss), ending balance	(647)	(648)
Reclassification from AOCI, Current Period, Tax	12	11
Tax (expense) benefit on other comprehensive income (loss)	(3)	8
Cumulative foreign currency translation adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), beginning balance	(84)	55
Other comprehensive income (loss), before reclassifications	(114)	(139)
Amounts reclassified from accumulated other comprehensive income (loss) after tax (expense) benefit	0	0
Other comprehensive income (loss) after tax (expense) benefit	(114)	(139)
Accumulated other comprehensive income (loss), ending balance	(198)	(84)
Reclassification from AOCI, Current Period, Tax	0	0
Tax (expense) benefit on other comprehensive income (loss)	$ 0	$ 0

Business Segments (Narrative) (

Business Segments (Narrative) (Details)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting [Abstract]
Percentage of direct foreign written premiums	7.90%	8.00%	8.80%

Business Segments (Income State

Business Segments (Income Statement Information) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Net written premiums	$ 6,988	$ 6,962	$ 7,088
Operating Revenues
Net earned premiums	6,924	6,921	7,212
Net Investment Income	1,988	1,840	2,067
Other revenues	404	407	356
Total operating revenues	9,316	9,168	9,635
Claims, Benefits and Expenses
Net incurred claims and benefits	5,270	5,372	5,577
Policyholders' dividends	13	12	14
Amortization of deferred acquisition costs	1,235	1,540	1,317
Other insurance related expenses	1,122	1,093	1,029
Other expenses	589	535	548
Total claims, benefits and expenses	8,229	8,552	8,485
Operating income (loss) from continuing operations before income tax	1,087	616	1,150
Income tax (expense) benefit on operating income (loss)	(263)	(101)	(301)
Net operating income (loss) from continuing operations	824	515	849
Net realized investment gains (losses), pre-tax	50	(67)	57
Income tax (expense) benefit on net realized investment gains (losses)	(15)	31	(18)
Net realized investment gains (losses), after tax	35	(36)	39
Net income (loss) from continuing operations	859	479	888
Specialty [Member]
Segment Reporting Information [Line Items]
Net written premiums	2,780	2,781	2,839
Operating Revenues
Net earned premiums	2,779	2,782	2,838
Net Investment Income	516	474	560
Other revenues	362	356	295
Total operating revenues	3,657	3,612	3,693
Claims, Benefits and Expenses
Net incurred claims and benefits	1,467	1,597	1,627
Policyholders' dividends	4	4	6
Amortization of deferred acquisition costs	591	589	592
Other insurance related expenses	301	278	262
Other expenses	312	301	254
Total claims, benefits and expenses	2,675	2,769	2,741
Operating income (loss) from continuing operations before income tax	982	843	952
Income tax (expense) benefit on operating income (loss)	(332)	(283)	(318)
Net operating income (loss) from continuing operations	650	560	634
Net realized investment gains (losses), pre-tax	5	(33)	15
Income tax (expense) benefit on net realized investment gains (losses)	(2)	11	(5)
Net realized investment gains (losses), after tax	3	(22)	10
Net income (loss) from continuing operations	653	538	644
Commercial [Member]
Segment Reporting Information [Line Items]
Net written premiums	2,841	2,818	2,817
Operating Revenues
Net earned premiums	2,804	2,788	2,906
Net Investment Income	638	593	723
Other revenues	32	37	38
Total operating revenues	3,474	3,418	3,667
Claims, Benefits and Expenses
Net incurred claims and benefits	1,927	1,814	2,187
Policyholders' dividends	9	8	8
Amortization of deferred acquisition costs	470	469	493
Other insurance related expenses	560	538	487
Other expenses	36	28	31
Total claims, benefits and expenses	3,002	2,857	3,206
Operating income (loss) from continuing operations before income tax	472	561	461
Income tax (expense) benefit on operating income (loss)	(161)	(192)	(154)
Net operating income (loss) from continuing operations	311	369	307
Net realized investment gains (losses), pre-tax	4	(47)	16
Income tax (expense) benefit on net realized investment gains (losses)	(2)	16	(6)
Net realized investment gains (losses), after tax	2	(31)	10
Net income (loss) from continuing operations	313	338	317
International [Member]
Segment Reporting Information [Line Items]
Net written premiums	821	822	880
Operating Revenues
Net earned premiums	806	804	913
Net Investment Income	51	52	61
Other revenues	0	(1)	0
Total operating revenues	857	855	974
Claims, Benefits and Expenses
Net incurred claims and benefits	492	479	488
Policyholders' dividends	0	0	0
Amortization of deferred acquisition costs	174	168	204
Other insurance related expenses	133	138	151
Other expenses	24	12	28
Total claims, benefits and expenses	823	797	871
Operating income (loss) from continuing operations before income tax	34	58	103
Income tax (expense) benefit on operating income (loss)	(13)	(21)	(34)
Net operating income (loss) from continuing operations	21	37	69
Net realized investment gains (losses), pre-tax	18	1	(1)
Income tax (expense) benefit on net realized investment gains (losses)	(3)	0	1
Net realized investment gains (losses), after tax	15	1	0
Net income (loss) from continuing operations	36	38	69
Life and Group Non-Core [Member]
Segment Reporting Information [Line Items]
Net written premiums	547	542	553
Operating Revenues
Net earned premiums	536	548	556
Net Investment Income	767	704	700
Other revenues	(2)	7	16
Total operating revenues	1,301	1,259	1,272
Claims, Benefits and Expenses
Net incurred claims and benefits	1,286	1,421	1,304
Policyholders' dividends	0	0	0
Amortization of deferred acquisition costs	0	314	28
Other insurance related expenses	132	142	130
Other expenses	8	11	30
Total claims, benefits and expenses	1,426	1,888	1,492
Operating income (loss) from continuing operations before income tax	(125)	(629)	(220)
Income tax (expense) benefit on operating income (loss)	145	315	151
Net operating income (loss) from continuing operations	20	(314)	(69)
Net realized investment gains (losses), pre-tax	25	(1)	7
Income tax (expense) benefit on net realized investment gains (losses)	(9)	9	0
Net realized investment gains (losses), after tax	16	8	7
Net income (loss) from continuing operations	36	(306)	(62)
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Net written premiums	0	1	1
Operating Revenues
Net earned premiums	0	1	1
Net Investment Income	16	17	23
Other revenues	12	11	12
Total operating revenues	28	29	36
Claims, Benefits and Expenses
Net incurred claims and benefits	98	61	(29)
Policyholders' dividends	0	0	0
Amortization of deferred acquisition costs	0	0	0
Other insurance related expenses	(3)	(1)	1
Other expenses	209	186	210
Total claims, benefits and expenses	304	246	182
Operating income (loss) from continuing operations before income tax	(276)	(217)	(146)
Income tax (expense) benefit on operating income (loss)	98	80	54
Net operating income (loss) from continuing operations	(178)	(137)	(92)
Net realized investment gains (losses), pre-tax	(2)	13	20
Income tax (expense) benefit on net realized investment gains (losses)	1	(5)	(8)
Net realized investment gains (losses), after tax	(1)	8	12
Net income (loss) from continuing operations	(179)	(129)	(80)
Eliminations [Member]
Segment Reporting Information [Line Items]
Net written premiums	(1)	(2)	(2)
Operating Revenues
Net earned premiums	(1)	(2)	(2)
Net Investment Income	0	0	0
Other revenues	0	(3)	(5)
Total operating revenues	(1)	(5)	(7)
Claims, Benefits and Expenses
Net incurred claims and benefits	0	0	0
Policyholders' dividends	0	0	0
Amortization of deferred acquisition costs	0	0	0
Other insurance related expenses	(1)	(2)	(2)
Other expenses	0	(3)	(5)
Total claims, benefits and expenses	(1)	(5)	(7)
Operating income (loss) from continuing operations before income tax	0	0	0
Income tax (expense) benefit on operating income (loss)	0	0	0
Net operating income (loss) from continuing operations	0	0	0
Net realized investment gains (losses), pre-tax	0	0	0
Income tax (expense) benefit on net realized investment gains (losses)	0	0	0
Net realized investment gains (losses), after tax	0	0	0
Net income (loss) from continuing operations	$ 0	$ 0	$ 0

Business Segments (Balance Shee

Business Segments (Balance Sheet Information) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Reinsurance receivables	$ 4,453	$ 4,491
Insurance receivables	2,255	2,129
Deferred acquisition costs	600	598
Goodwill	145	150
Insurance reserves
Claim and claim adjustment expenses	22,343	22,663
Unearned premiums	3,762	3,671
Future policy benefits	10,326	10,152
Specialty [Member]
Segment Reporting Information [Line Items]
Reinsurance receivables	760	724
Insurance receivables	982	890
Deferred acquisition costs	310	307
Goodwill	117	117
Insurance reserves
Claim and claim adjustment expenses	6,149	6,269
Unearned premiums	1,911	1,839
Future policy benefits	0	0
Commercial [Member]
Segment Reporting Information [Line Items]
Reinsurance receivables	621	639
Insurance receivables	1,021	993
Deferred acquisition costs	214	213
Goodwill	0	0
Insurance reserves
Claim and claim adjustment expenses	8,894	9,183
Unearned premiums	1,323	1,297
Future policy benefits	0	0
International [Member]
Segment Reporting Information [Line Items]
Reinsurance receivables	131	144
Insurance receivables	233	233
Deferred acquisition costs	76	78
Goodwill	28	33
Insurance reserves
Claim and claim adjustment expenses	1,328	1,347
Unearned premiums	396	415
Future policy benefits	0	0
Life and Group Non-Core [Member]
Segment Reporting Information [Line Items]
Reinsurance receivables	462	497
Insurance receivables	17	11
Deferred acquisition costs	0	0
Goodwill	0	0
Insurance reserves
Claim and claim adjustment expenses	3,358	3,220
Unearned premiums	132	120
Future policy benefits	10,326	10,152
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Reinsurance receivables	2,479	2,487
Insurance receivables	2	2
Deferred acquisition costs	0	0
Goodwill	0	0
Insurance reserves
Claim and claim adjustment expenses	2,614	2,644
Unearned premiums	0	0
Future policy benefits	0	0
Eliminations [Member]
Segment Reporting Information [Line Items]
Reinsurance receivables	0	0
Insurance receivables	0	0
Deferred acquisition costs	0	0
Goodwill	0	0
Insurance reserves
Claim and claim adjustment expenses	0	0
Unearned premiums	0	0
Future policy benefits	$ 0	$ 0

Business Segments (Revenues by

Business Segments (Revenues by Line of Business) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenues	$ 2,390	$ 2,433	$ 2,348	$ 2,195	$ 2,269	$ 2,153	$ 2,327	$ 2,352	$ 9,366	$ 9,101	$ 9,692
Specialty [Domain]
Revenues									3,662	3,579	3,708
Management & Professional Liability [Member]
Revenues									2,620	2,617	2,818
Surety [Member]
Revenues									532	502	509
Warranty & Alternative Risks [Member]
Revenues									510	460	381
Commercial [Domain]
Revenues									3,478	3,371	3,683
Middle Markets [Member]
Revenues									1,769	1,623	1,631
Small Business [Member]
Revenues									583	616	709
Other Commercial Insurance [Member]
Revenues									1,126	1,132	1,343
International [Domain]
Revenues									875	856	973
Canada [Member]
Revenues									203	214	273
CNA Europe [Member]
Revenues									319	309	335
Hardy [Member]
Revenues									353	333	365
Life and Group Non-Core [Member]
Revenues									1,326	1,258	1,279
Corporate and Other [Member]
Revenues									26	42	56
Eliminations [Member]
Revenues									$ (1)	$ (5)	$ (7)

Discontinued Operations Income

Discontinued Operations Income Statement Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenues
Net Earned Premium			$ 0
Net Investment Income			94
Net Realized Investment Gains (Losses)			3
Other Revenues			0
Total Revenues			97
Claims, Benefits and Expenses
Insurance Claims and Policyholders' Benefits			75
Other Operating Expenses			2
Total Claims, Benefits and Expenses			77
Income before Income Tax			20
Income tax (expense) benefit			(6)
Income from operations of discontinued operations, net of income tax			14
Loss on sale, net of income tax (expense) benefit of $40, - and -			(211)
Income tax benefit (expense) on impairment			40
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	$ 0	$ 0	$ (197)

Discontinued Operations (Narrat

Discontinued Operations (Narrative) (Details) $ in Millions	Aug. 01, 2014USD ($)
Discontinued Operations and Disposal Groups [Abstract]
Disposal Group, Including Discontinued Operation, Assets	$ 3,550
Disposal Group, Including Discontinued Operation, Liabilities	$ 3,297

Quarterly Financial Data (Un143

Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended											12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016		Dec. 31, 2015		Sep. 30, 2015	Jun. 30, 2015		Mar. 31, 2015	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Quarterly Financial Data [Abstract]
Revenues	$ 2,390	$ 2,433	$ 2,348	$ 2,195		$ 2,269		$ 2,153	$ 2,327		$ 2,352	$ 9,366		$ 9,101		$ 9,692
Net income (loss)	$ 241	$ 343	$ 209	$ 66	[1]	$ (70)	[2]	$ 178	$ 138	[1]	$ 233	$ 859	[1]	$ 479	[1],[2]	$ 691
Basic earnings (loss) per share	$ 0.89	$ 1.27	$ 0.77	$ 0.25		$ (0.26)		$ 0.66	$ 0.51		$ 0.86	$ 3.18		$ 1.77		$ 2.56
Diluted earnings (loss) per share	$ 0.89	$ 1.26	$ 0.77	$ 0.24		$ (0.26)		$ 0.66	$ 0.51		$ 0.86	$ 3.17		$ 1.77		$ 2.55
[1]	Net income (loss) in the first quarter of 2016 and the second quarter of 2015 included a charge related to the application of retroactive reinsurance accounting to adverse reserve development ceded under the 2010 A&EP Loss Portfolio Transfer in our Corporate & Other Non-Core segment.
[2]	Net income (loss) in the fourth quarter of 2015 included a charge related to recognition of a premium deficiency in our long term care business.

Related Party Transactions Narr

Related Party Transactions Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Due to Related Parties	$ 50	$ 82
Fees and expenses of investment facilities and services [Member]
Amounts reimbursed to Loews for services provided to the Company	43	39	$ 39
Due to Related Parties	23	21
Corporate Services and Related Travel Expenses [Member]
Amounts reimbursed to Loews for services provided to the Company	1
Taxes paid [Member]
Due to Related Parties	28	61
Loews [Member]
Amounts earned from Loews for insurance premiums	$ 2	$ 2	$ 2

Organization Review Narrative (

Organization Review Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016USD ($)
Restructuring and Related Activities [Abstract]
Restructuring Costs	$ 19

Organization Review Costs by Re

Organization Review Costs by Reportable Segment (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring Costs	$ 19
Specialty [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Costs	4
Commercial [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Costs	14
International [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Costs	0
Life and Group Non-Core [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Costs	1
Corporate and Other [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Costs	$ 0

Schedule II. Condensed Finan147

Schedule II. Condensed Financial Information of Registrant (Parent Company) (Schedule of Condensed Financial Information of Registrant, Statements of Operations and Comprehensive Income) (Details) - USD ($) $ in Millions	3 Months Ended											12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016		Dec. 31, 2015		Sep. 30, 2015	Jun. 30, 2015		Mar. 31, 2015	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Revenues
Net realized investment gains (losses)												$ 50		$ (67)		$ 57
Total revenues	$ 2,390	$ 2,433	$ 2,348	$ 2,195		$ 2,269		$ 2,153	$ 2,327		$ 2,352	9,366		9,101		9,692
Claims, Benefits and Expenses
Interest												159		155		183
Income tax expense (benefit)												(278)		(70)		(319)
Net income (loss)	$ 241	$ 343	$ 209	$ 66	[1]	$ (70)	[2]	$ 178	$ 138	[1]	$ 233	859	[1]	479	[1],[2]	691
Total comprehensive income (loss)												1,001		(236)		649
Parent Company [Member]
Revenues
Net investment income												3		1		1
Net realized investment gains (losses)												(7)		5		4
Total revenues												(4)		6		5
Claims, Benefits and Expenses
Administrative and general												1		1		5
Interest												155		154		182
Total expenses												156		155		187
Income (loss) from operations before income taxes and equity in net income of subsidiaries												(160)		(149)		(182)
Income tax expense (benefit)												41		34		35
Income (loss) before equity in net income (loss) of subsidiaries												(119)		(115)		(147)
Equity in net income of subsidiaries												978		594		838
Net income (loss)												859		479		691
Equity in other comprehensive income of subsidiaries												142		(715)		(42)
Total comprehensive income (loss)												$ 1,001		$ (236)		$ 649
[1]	Net income (loss) in the first quarter of 2016 and the second quarter of 2015 included a charge related to the application of retroactive reinsurance accounting to adverse reserve development ceded under the 2010 A&EP Loss Portfolio Transfer in our Corporate & Other Non-Core segment.
[2]	Net income (loss) in the fourth quarter of 2015 included a charge related to recognition of a premium deficiency in our long term care business.

Schedule II. Condensed Finan148

Schedule II. Condensed Financial Information of Registrant (Parent Company) (Schedule of Condensed Financial Information of Registrant, Balance Sheets) (Details) - USD ($) $ / shares in Units, $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Assets
Cash	$ 271	$ 387	$ 190	$ 195
Short term investments	1,407	1,660
Other assets	1,078	1,295
Total assets	55,233	55,045
Liabilities
Short term debt	0	350
Long term debt	2,710	2,210
Other liabilities	4,123	4,243
Total liabilities	43,264	43,289
Stockholders' Equity
Common stock ($2.50 par value; 500,000,000 shares authorized; 273,040,243 shares issued; 270,495,998 and 270,274,361 shares outstanding)	683	683	683	683
Additional paid-in capital	2,173	2,153	2,151	2,145
Retained earnings	9,359	9,313	9,645	9,495
Accumulated other comprehensive income (loss)	(173)	(315)	400	442
Treasury stock (2,544,245 and 2,765,882 shares), at cost	(73)	(78)	(84)	(91)
Total stockholders’ equity	11,969	11,756	12,794
Total liabilities and stockholders' equity	$ 55,233	$ 55,045
Balance Sheet Parenthetical
Common stock, par value	$ 2.50	$ 2.50
Common stock, shares authorized	500,000,000	500,000,000
Common stock, shares issued	273,040,243	273,040,243
Common stock, shares outstanding	270,495,998	270,274,361
Treasury stock, shares	2,544,245	2,765,882
Parent Company [Member]
Assets
Investment in subsidiaries	$ 14,202	$ 13,851
Cash	1	4	$ 1	$ 1
Short term investments	487	478
Due from Affiliates	6	0
Other assets	1	1
Total assets	14,697	14,334
Liabilities
Short term debt	0	350
Long term debt	2,680	2,180
Other liabilities	48	48
Total liabilities	2,728	2,578
Stockholders' Equity
Common stock ($2.50 par value; 500,000,000 shares authorized; 273,040,243 shares issued; 270,495,998 and 270,274,361 shares outstanding)	683	683
Additional paid-in capital	2,173	2,153
Retained earnings	9,359	9,313
Accumulated other comprehensive income (loss)	(173)	(315)
Treasury stock (2,544,245 and 2,765,882 shares), at cost	(73)	(78)
Total stockholders’ equity	11,969	11,756
Total liabilities and stockholders' equity	$ 14,697	$ 14,334
Balance Sheet Parenthetical
Common stock, par value	$ 2.50	$ 2.50
Common stock, shares authorized	500,000,000	500,000,000
Common stock, shares issued	273,040,243	273,040,243
Common stock, shares outstanding	270,495,998	270,274,361
Treasury stock, shares	2,544,245	2,765,882

Schedule II. Condensed Finan149

Schedule II. Condensed Financial Information of Registrant (Parent Company) (Schedule of Condensed Financial Information of Registrant, Statements of Cash Flows) (Details) - USD ($) $ in Millions	3 Months Ended											12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016		Dec. 31, 2015		Sep. 30, 2015	Jun. 30, 2015	[1]	Mar. 31, 2015	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Cash Flows from Operating Activities
Net income (loss)	$ 241	$ 343	$ 209	$ 66	[1]	$ (70)	[2]	$ 178	$ 138		$ 233	$ 859	[1]	$ 479	[1],[2]	$ 691
Adjustments to reconcile net income (loss) to net cash flows provided (used) by operating activities:
Net realized investment (gains) losses												(50)		67		(57)
Other, net												29		(2)		54
Total adjustments												557		908		749
Net cash flows provided (used) by operating activities												1,416		1,387		1,440
Cash Flows from Investing Activities
Change in short term investments												258		34		(388)
Other, net												2		21		16
Net cash flows provided (used) by investing activities												(846)		(372)		(918)
Cash Flows from Financing Activities
Dividends paid to common stockholders												(813)		(811)		(541)
Proceeds from the issuance of debt												498		0		546
Repayment of debt												(358)		0		(549)
Other, net												0		4		25
Net cash flows provided (used) by financing activities												(673)		(807)		(519)
Net change in cash												(116)		197		(5)
Cash, beginning of year				387							190	387		190		195
Cash, end of year	271					387						271		387		190
Parent Company [Member]
Cash Flows from Operating Activities
Net income (loss)												859		479		691
Adjustments to reconcile net income (loss) to net cash flows provided (used) by operating activities:
Equity in net income (loss) of subsidiaries												(978)		(594)		(838)
Dividends received from subsidiaries												765		900		650
Net realized investment (gains) losses												7		(5)		(4)
Other, net												21		4		14
Total adjustments												(185)		305		(178)
Net cash flows provided (used) by operating activities												674		784		513
Cash Flows from Investing Activities
Change in short term investments												(9)		21		6
Capital contributions to subsidiaries												0		0		(10)
Other, net												4		7		5
Net cash flows provided (used) by investing activities												(5)		28		1
Cash Flows from Financing Activities
Dividends paid to common stockholders												(813)		(811)		(541)
Proceeds from the issuance of debt												498		0		546
Repayment of debt												(358)		0		(549)
Stock options exercised												0		1		5
Other, net												1		1		25
Net cash flows provided (used) by financing activities												(672)		(809)		(514)
Net change in cash												(3)		3		0
Cash, beginning of year				$ 4							$ 1	4		1		1
Cash, end of year	$ 1					$ 4						$ 1		$ 4		$ 1
[1]	Net income (loss) in the first quarter of 2016 and the second quarter of 2015 included a charge related to the application of retroactive reinsurance accounting to adverse reserve development ceded under the 2010 A&EP Loss Portfolio Transfer in our Corporate & Other Non-Core segment.
[2]	Net income (loss) in the fourth quarter of 2015 included a charge related to recognition of a premium deficiency in our long term care business.

Schedule II. Condensed Finan150

Schedule II. Condensed Financial Information of Registrant (Parent Company) (Schedule II. Condensed Financial Information of Registrant (Narrative)) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Cumulative Effect of New Accounting Principle in Period of Adoption on Other Assets		$ (2)
Cumulative Effect of New Accounting Principle in Period of Adoption on Long Term Debt		(2)
Parent Company [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption on Other Assets		(2)
Cumulative Effect of New Accounting Principle in Period of Adoption on Long Term Debt		(2)
Guarantor Obligations, Current Carrying Value	$ 5	$ 5
Guarantor Obligations, Maximum Exposure, Undiscounted	1,900
Indemnification Agreement [Member]
Guarantor Obligations, Maximum Exposure, Undiscounted	258
Indemnification Agreement [Member] | Parent Company [Member]
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 625

Schedule V. Valuation and Qu151

Schedule V. Valuation and Qualifying Accounts (Schedule of valuation and qualifying accounts) (Details) - Allowance for doubtful accounts, insurance and reinsurance receivables [Member] - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Movement in valuation allowances and reserves [Roll Forward]
Balance at beginning of period		$ 89	$ 109	$ 155
Charged to costs and expenses		(2)	(12)	(40)
Charged to other accounts	[1]	(1)	0	(1)
Deductions		(3)	(8)	(5)
Balance at end of period		$ 83	$ 89	$ 109
[1]	Amount includes effects of foreign currency translation.

Schedule VI. Supplemental In152

Schedule VI. Supplemental Information Concerning Property and Casualty Insurance Operations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Incurred claim and claim adjustment expenses related to current year	$ 5,025	$ 4,934	$ 5,043
Incurred claim and claim adjustment expenses related to prior years	(342)	(255)	(36)
Consolidated Property and Casualty Insurance Entity [Member]
Deferred acquisition costs	599	597
Reserves for unpaid claim and claim adjustment expenses	22,343	22,663
Discount deducted from claim and claim adjustment expense reserves above (based on interest rates ranging from 3.5% to 8.0%)	1,572	1,534
Unearned Premiums	3,762	3,671
Net written premiums	6,988	6,962	7,088
Net earned premiums	6,924	6,921	7,212
Net investment income	1,952	1,807	2,031
Incurred claim and claim adjustment expenses related to current year	5,025	4,934	5,043
Incurred claim and claim adjustment expenses related to prior years	(342)	(255)	(39)
Amortization of deferred acquisition costs	1,235	1,540	1,317
Paid claim and claim adjustment expenses	$ 5,134	$ 4,945	$ 5,297
Consolidated Property and Casualty Insurance Entity [Member] | Minimum [Member]
Supplemental Information Parenthetical
Supplemental Information for Property, Casualty Insurance Underwriters, Interest Rate at which Discount Computed	3.50%	3.50%
Consolidated Property and Casualty Insurance Entity [Member] | Maximum [Member]
Supplemental Information Parenthetical
Supplemental Information for Property, Casualty Insurance Underwriters, Interest Rate at which Discount Computed	8.00%	8.00%