Insurance (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Analysis of changes in the liability for losses and loss adjustment expenses, net of reinsurance
Balance at beginning of period				$ 4,129				$ 4,282	$ 4,129	$ 4,282	$ 4,164
Provision for losses and LAE occurring in the current year									2,055	1,903	1,813
Net decrease in provision for claims of prior years	(5)	40	(22)	(28)	(7)	23	(27)	(19)	(15)	(30)	(69)
Total losses and LAE incurred									2,040	1,873	1,744
Payments for losses and LAE of:
Current year									(739)	(841)	(652)
Prior years									(1,131)	(1,185)	(969)
Total payments									(1,870)	(2,026)	(1,621)
Foreign currency translation and other									(11)	0	(5)
Balance at end of period	4,288				4,129				4,288	4,129	4,282
Add back reinsurance recoverables, net of allowance	2,122				2,716				2,122	2,716	2,238
Gross unpaid losses and LAE included in the Balance Sheet	$ 6,410				$ 6,845				$ 6,410	$ 6,845	$ 6,520