Reserve for Property-Liability Insurance Claims and Claims Expense (Details) (Property-Liability, USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Property-Liability
Activity in the reserve for property-liability insurance claims and claims expense:
Balance at beginning of period	$ 20,375	$ 19,468	$ 19,167
Less reinsurance recoverables	2,588	2,072	2,139
Net balance at beginning of period	17,787	17,396	17,028
Esurance acquisition	(13)	425
Incurred claims and claims expense related to:
Current year	19,149	20,496	19,110
Prior years	(665)	(335)	(159)
Total incurred	18,484	20,161	18,951
Claims and claims expense paid related to:
Current year	12,545	13,893	12,012
Prior years	6,435	6,302	6,571
Total paid	18,980	20,195	18,583
Net balance at end of period	17,278	17,787	17,396
Plus reinsurance recoverables	4,010	2,588	2,072
Balance at end of period	$ 21,288	$ 20,375	$ 19,468