Reserve for Property-Liability Insurance Claims and Claims Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Incurred claims and claims expense related to:
Current year	$ 20,953	$ 19,512	$ 18,032
Prior years	81	(84)	(121)
Property-Liability
Activity in the reserve for property-liability insurance claims and claims expense:
Balance as of January 1	22,923	21,857	21,288
Less reinsurance recoverables	5,694	4,664	4,010
Net balance as of January 1	17,229	17,193	17,278
Incurred claims and claims expense related to:
Current year	20,953	19,512	18,032
Prior years	81	(84)	(121)
Total incurred	21,034	19,428	17,911
Claims and claims expense paid related to:
Current year	13,660	12,924	11,658
Prior years	6,626	6,468	6,338
Total paid	20,286	19,392	17,996
Net balance as of December 31	17,977	17,229	17,193
Plus reinsurance recoverables	5,892	5,694	4,664
Balance as of December 31	$ 23,869	$ 22,923	$ 21,857