Income Taxes (Summary Of Deferred Tax Assets And Liabilities) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Income Taxes [Abstract]
Property and casualty claim and claim adjustment expense reserves	$ 419	$ 525
Unearned premium reserves	142	127
Receivables	75	99
Employee benefits	449	375
Life settlement contracts	61	64
Investment valuation differences	3	70
Net loss and tax credits carried forward	135	126
Basis differential in investment in subsidiary	29	32
Other	224	200
Deferred tax assets	1,537	1,618
Deferred acquisition costs	(283)	(284)
Net unrealized gains	(516)	(326)
Property, plant and equipment	(790)	(644)
Basis differential in investment in subsidiary	(490)	(477)
Other liabilities	(117)	(160)
Deferred tax liabilities	(2,196)	(1,891)
Net deferred tax liability	$ (659)	$ (273)