Segments Information (Details 1) (USD $) In Millions	3 Months Ended	9 Months Ended
Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Income (loss) before income tax [Abstract]
Total property and casualty insurance	$ 357	$ 787	$ 1,485	$ 2,023
Corporate and other loss	(62)	(57)	(188)	(160)
Realized investment gains, Net	71	54	300	271
Income Before Federal and Foreign Income Tax	366	784	1,597	2,134
Property and casualty insurance [Member]
Income (loss) before income tax [Abstract]
Insurance underwriting income	(71)	399	194	809
Reinsurance assumed underwriting income	11	7	26	21
Underwriting income before deferred policy acquisition costs	(60)	406	220	830
Increase (decrease) in deferred policy acquisition costs	13	(7)	70	36
Underwriting income (loss)	(47)	399	290	866
Investment income	396	390	1,171	1,162
Other income (charges)	8	(2)	24	(5)
Property and casualty insurance [Member] \| Personal insurance [Member]
Income (loss) before income tax [Abstract]
Insurance underwriting income	(168)	125	(84)	143
Property and casualty insurance [Member] \| Commercial insurance [Member]
Income (loss) before income tax [Abstract]
Insurance underwriting income	8	151	(90)	262
Property and casualty insurance [Member] \| Specialty Insurance [Member]
Income (loss) before income tax [Abstract]
Insurance underwriting income	$ 89	$ 123	$ 368	$ 404

Represents income (loss) before income tax related to non-insurance companies before realized investment gain (loss).

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Amount of underwriting income (loss) for the reportable property and casualty insurance segments which is arrived at by reducing premiums earned by losses and loss expenses incurred and statutory underwriting expenses incurred, before reinsurance assumed business which is in run-off. Under statutory accounting principles, policy acquisition and other underwriting expenses are recognized immediately, not at the time premiums are earned.

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Reflects the sum of all other income and charges recognized by the entity in the period not otherwise specified separately.

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Amount of income (loss) before income tax for property and casualty insurance including underwriting income (loss), investment income (loss) and other income (charges), before realized investment gain (loss).

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Amount of underwriting income (loss) for the property and casualty insurance reinsurance assumed segment, which is in run-off, which is arrived at by reducing premiums earned by losses and loss expenses incurred and statutory underwriting expenses incurred. Under statutory accounting principles, policy acquisition and other underwriting expenses are recognized immediately, not at the time premiums are earned.

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Amount of underwriting income (loss) for the property and casualty insurance segments which is arrived at by reducing premiums earned by losses and loss expenses incurred and generally accepted accounting principles (GAAP) underwriting expenses incurred. Under GAAP, policy acquisition expenses are deferred and amortized over the period in which the related premiums are earned.

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Amount of underwriting income (loss) for the property and casualty insurance segments which is arrived at by reducing premiums earned by losses and loss expenses incurred and statutory underwriting expenses incurred. Under statutory accounting principles, policy acquisition and other underwriting expenses are recognized immediately, not at the time premiums are earned.

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This item represents the net total realized and unrealized gain (loss) included in earnings for the period as a result of selling or holding marketable securities categorized as trading, available-for-sale, or held-to-maturity, including the unrealized holding gain (loss) of held-to-maturity securities transferred to the trading security category and the cumulative unrealized gain (loss) which was included in other comprehensive income (a separate component of shareholders' equity) for available-for-sale securities transferred to trading securities during the period. Additionally, this item would include any gains (losses) realized during the period from the sale of investments accounted for under the cost method of accounting and losses recognized for other than temporary impairments (OTTI) of the subject investments.

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Sum of operating profit and nonoperating income or expense before Income or Loss from equity method investments, income taxes, extraordinary items, and noncontrolling interest.

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The increase (decrease) during the reporting period in the balance sheet value of capitalized sales costs that are associated with acquiring a new insurance customers.

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The total amount of investment earnings, excluding realized and unrealized gain (loss), recognized in the period on the entity's investments, net of related investment expenses. Such amount includes interest, dividends, and rental income.

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