Reserve for Property-Liability Insurance Claims and Claims Expense (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Incurred claims and claims expense related to:
Current year	$ 19,512	$ 18,032	$ 19,149
Prior years	(84)	(121)	(665)
Property-Liability
Activity in the reserve for property-liability insurance claims and claims expense:
Balance at beginning of period	21,857	21,288	20,375
Less reinsurance recoverables	4,664	4,010	2,588
Net balance at beginning of period	17,193	17,278	17,787
Esurance acquisition			(13)
Incurred claims and claims expense related to:
Current year	19,512	18,032	19,149
Prior years	(84)	(121)	(665)
Total incurred	19,428	17,911	18,484
Claims and claims expense paid related to:
Current year	12,924	11,658	12,545
Prior years	6,468	6,338	6,435
Total paid	19,392	17,996	18,980
Net balance at end of period	17,229	17,193	17,278
Plus reinsurance recoverables	5,694	4,664	4,010
Balance at end of period	$ 22,923	$ 21,857	$ 21,288