Federal and Foreign Income Tax (Details 2) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
The tax effects of temporary differences that gave rise to deferred income tax assets and liabilities [Abstract]
Unpaid losses and loss expenses	$ 632	$ 643
Unearned premiums	339	334
Foreign tax credits	853	834
Employee compensation	116	125
Postretirement benefits	293	165
Other-than-temporary impairment losses	286	290
Total deferred income tax assets	2,519	2,391
Deferred policy acquisition costs	457	441
Unremitted earnings of foreign subsidiaries	925	936
Unrealized Appreciation of investments	934	603
Other invested assets	235	212
Other, net	117	101
Total deferred income tax liabilities	2,668	2,293
Net deferred income tax asset (liability)	$ (149)	$ 98