Insurance (Details 7) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Liabilities for Unpaid Claims and Claim Expenses
Balance at January 1,	$ 10,117	$ 10,708	$ 8,219
Less: Reinsurance recoverables	1,436	2,198	547
Net balance at January 1,	8,681	8,510	7,672
Acquisitions, net	0	0	583
Incurred related to:
Current year	8,399	9,028	6,482
Prior years	(69)	(199)	(75)
Total incurred	8,330	8,829	6,407
Paid related to:
Current year	(5,689)	(6,238)	(4,050)
Prior years	(2,467)	(2,420)	(2,102)
Total paid	(8,156)	(8,658)	(6,152)
Net balance at December 31,	8,855	8,681	8,510
Add: Reinsurance recoverables	1,581	1,436	2,198
Balance at December 31,	$ 10,436	$ 10,117	$ 10,708