Investments and Derivative Instruments (Details 11) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Variable Interest Entities Primary Beneficiary
Total Liabilities	$ 73	$ 111
Variable Interest Entity Assets Included in Limited Partnerships and Other Alternative Investments	4	6
Consolidated VIEs [Member]
Variable Interest Entities Primary Beneficiary
Total Assets	184	227
Maximum Exposure to Loss	118	120
Collateralized Debt Obligations [Member] | Consolidated VIEs [Member]
Variable Interest Entities Primary Beneficiary
Total Assets	49	89
Total Liabilities	51	88
Maximum Exposure to Loss	0	7
Investment Funds [Member] | Consolidated VIEs [Member]
Variable Interest Entities Primary Beneficiary
Total Assets	131	132
Total Liabilities	20	20
Maximum Exposure to Loss	116	110
Limited partnerships [Member] | Consolidated VIEs [Member]
Variable Interest Entities Primary Beneficiary
Total Liabilities	2	3
Maximum Exposure to Loss	$ 2	$ 3