Investments (Consolidated Variable Interest Entities) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Variable Interest Entity [Line Items]
Total Assets	$ 8,616	$ 6,692
Total Liabilities	4,286	2,567
Consolidated Securitization Entities [Member]
Variable Interest Entity [Line Items]
Total Assets	2,453	2,730
Total Liabilities	2,282	2,545
MRSC collateral financing arrangement [Member]
Variable Interest Entity [Line Items]
Total Assets	3,449	3,439
Total Liabilities	0	0
Operating joint venture [Member]
Variable Interest Entity [Line Items]
Total Assets	2,364	0
Total Liabilities	1,976	0
Other limited partnership interests [Member]
Variable Interest Entity [Line Items]
Total Assets	187	356
Total Liabilities	14	8
Real estate joint ventures [Member]
Variable Interest Entity [Line Items]
Total Assets	11	11
Total Liabilities	14	14
Other invested assets [Member]
Variable Interest Entity [Line Items]
Total Assets	85	85
Total Liabilities	0	0
Trading Account Assets [Member]
Variable Interest Entity [Line Items]
Total Assets	67	71
Total Liabilities	$ 0	$ 0