Shareholders' Equity (Details 1) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Comparison of shareholders' equity on a GAAP basis and policyholders' surplus on a statutory basis [Abstract]
Shareholders' equity	$ 15,574	$ 15,530	$ 15,634
Property and Casualty Insurance Group [Member]
Comparison of shareholders' equity on a GAAP basis and policyholders' surplus on a statutory basis [Abstract]
Shareholders' equity	16,886	17,266
Policyholders' surplus	13,958	14,539
Corporate and other [Member]
Comparison of shareholders' equity on a GAAP basis and policyholders' surplus on a statutory basis [Abstract]
Shareholders' equity	$ (1,312)	$ (1,736)

The amount of statutory capital and surplus (stockholders' equity) as of the balance sheet date using prescribed or permitted statutory accounting practices (rather than GAAP, if different) of the state or country.

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Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

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