Investments and Derivative Instruments (Details 8) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Commercial Mortgage Loans Credit Quality
Avg. Debt-Service	2.00
Commercial [Member]
Commercial Mortgage Loans Credit Quality
Carrying Value	$ 3,620	$ 4,935
Avg. Debt-Service	2.00	2.34
Greater than 80% [Member] | Commercial [Member]
Commercial Mortgage Loans Credit Quality
Carrying Value	99	137
Avg. Debt-Service	1.25	0.89
65% - 80% [Member] | Commercial [Member]
Commercial Mortgage Loans Credit Quality
Carrying Value	1,004	1,717
Avg. Debt-Service	1.90	2.27
Less than 65% [Member] | Commercial [Member]
Commercial Mortgage Loans Credit Quality
Carrying Value	$ 2,517	$ 3,081
Avg. Debt-Service	2.07	2.44