Investments (Consolidated Variable Interest Entities - Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Variable Interest Entity [Line Items]
Tax credits guaranteed by third parties that reduce maximum exposure to loss related to other invested assets	$ 302		$ 302		$ 318
Financial or other support to investees designated as VIEs			0	0
Consolidated Securitization Entities [Member]
Variable Interest Entity [Line Items]
Variable interest, maximum exposure to loss in consolidated securitization entities	157		157		168
Long-term debt held by consolidated securitization entities, percentage range minimum			2.25%	2.25%
Long-term debt held by consolidated securitization entities, percentage range maximum			5.57%	5.57%
Interest expense on long-term debt held by consolidated securitization entities	$ 34	$ 42	$ 67	$ 85