Insurance Claim Reserves (details) - Reserve Detail for Claims and Claim Adjustment Expenses - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reconciliation of beginning and ending reserve balances for claims and claim adjustment expenses [Roll Forward]
Claims and claim adjustment expense reserves at beginning of year	$ 49,850	$ 50,895
Claims and claim adjustment expense reserves at end of year	48,295	49,850	$ 50,895
Property casualty [Member]
Reconciliation of beginning and ending reserve balances for claims and claim adjustment expenses [Roll Forward]
Claims and claim adjustment expense reserves at beginning of year	49,824	50,865	50,888
Reinsurance recoverables on unpaid losses	8,788	9,280	10,254
Net reserves at beginning of year	41,036	41,585	40,634
Estimated claims and claim adjustment expenses for claims arising in the current year	14,412	14,621	14,060
Estimated decrease in claims and claim adjustment expenses for claims arising in prior years	(897)	(957)	(944)
Total increases	13,515	13,664	13,116
Claims and claim adjustment expense payments for claims arising in current year	5,666	5,828	5,485
Claims and claim adjustment expense payments for claims arising in prior years	8,669	8,099	8,477
Total payments	14,335	13,927	13,962
Acquisitions	2		1,792
Unrealized foreign exchange (gain) loss	(395)	(286)	5
Net reserves at end of year	39,823	41,036	41,585
Reinsurance recoverables on unpaid losses	8,449	8,788	9,280
Claims and claim adjustment expense reserves at end of year	48,272	49,824	$ 50,865
Accident and health [Member]
Reconciliation of beginning and ending reserve balances for claims and claim adjustment expenses [Roll Forward]
Claims and claim adjustment expense reserves at beginning of year	26
Claims and claim adjustment expense reserves at end of year	$ 23	$ 26