Investments (Details 21) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Variable Interest Entity [Line Items]
Total Assets	$ 6,692	$ 7,273
Total Liabilities	2,567	3,128
Consolidated Securitization Entities [Member]
Variable Interest Entity [Line Items]
Total Assets	2,730	3,299
Total Liabilities	2,545	3,103
MRSC collateral financing arrangement [Member]
Variable Interest Entity [Line Items]
Total Assets	3,439	3,333
Total Liabilities	0	0
Other limited partnership interests [Member]
Variable Interest Entity [Line Items]
Total Assets	356	360
Total Liabilities	8	6
Real estate joint ventures [Member]
Variable Interest Entity [Line Items]
Total Assets	11	16
Total Liabilities	14	18
Other invested assets [Member]
Variable Interest Entity [Line Items]
Total Assets	85	102
Total Liabilities	0	1
Trading Account Assets [Member]
Variable Interest Entity [Line Items]
Total Assets	71	163
Total Liabilities	$ 0	$ 0