Investments (Consolidated Variable Interest Entities) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Variable Interest Entity [Line Items]
Total Assets	$ 8,333	$ 6,692
Total Liabilities	3,965	2,567
Consolidated Securitization Entities [Member]
Variable Interest Entity [Line Items]
Total Assets	2,309	2,730
Total Liabilities	2,135	2,545
MRSC collateral financing arrangement [Member]
Variable Interest Entity [Line Items]
Total Assets	3,505	3,439
Total Liabilities	0	0
Operating joint venture [Member]
Variable Interest Entity [Line Items]
Total Assets	2,182	0
Total Liabilities	1,804	0
Other limited partnership interests [Member]
Variable Interest Entity [Line Items]
Total Assets	180	356
Total Liabilities	11	8
Real estate joint ventures [Member]
Variable Interest Entity [Line Items]
Total Assets	10	11
Total Liabilities	15	14
Other invested assets [Member]
Variable Interest Entity [Line Items]
Total Assets	82	85
Total Liabilities	0	0
Trading Account Assets [Member]
Variable Interest Entity [Line Items]
Total Assets	65	71
Total Liabilities	$ 0	$ 0