Investments and Derivative Instruments (Details 8) (USD $) In Millions, unless otherwise specified	Jun. 30, 2011	Dec. 31, 2010
Commercial Mortgage Loans Credit Quality
Avg. Debt-Service Coverage Ratio	1.88
Greater than 80% [Member] | Commercial [Member]
Commercial Mortgage Loans Credit Quality
Carrying Value	$ 1,032	$ 1,358
Avg. Debt-Service Coverage Ratio	1.510	1.490
65% - 80% [Member] | Commercial [Member]
Commercial Mortgage Loans Credit Quality
Carrying Value	2,379	1,829
Avg. Debt-Service Coverage Ratio	1.710	1.930
Less than 65% [Member] | Commercial [Member]
Commercial Mortgage Loans Credit Quality
Carrying Value	1,784	1,153
Avg. Debt-Service Coverage Ratio	2.300	2.260
Commercial [Member]
Commercial Mortgage Loans Credit Quality
Carrying Value	$ 5,195	$ 4,340
Avg. Debt-Service Coverage Ratio	1.880	1.870