Investments (Details 35) (USD $) In Millions	Jun. 30, 2011	Dec. 31, 2010
Past Due and Interest Accrual Status of Mortgage Loans
Past Due Status of Mortgage Loans	$ 357	$ 296
Interest Accrual Status of Mortgage Loans	142	25
Mortgage loans that were in non accrual status	216	209
Commercial mortgage loans portfolio segment [Member]
Past Due and Interest Accrual Status of Mortgage Loans
Past Due Status of Mortgage Loans	161	58
Interest Accrual Status of Mortgage Loans	115	1
Mortgage loans that were in non accrual status	41	7
Agricultural mortgage loans portfolio segment [Member]
Past Due and Interest Accrual Status of Mortgage Loans
Past Due Status of Mortgage Loans	161	159
Interest Accrual Status of Mortgage Loans	17	13
Mortgage loans that were in non accrual status	147	177
Residential mortgage loans portfolio segment [Member]
Past Due and Interest Accrual Status of Mortgage Loans
Past Due Status of Mortgage Loans	35	79
Interest Accrual Status of Mortgage Loans	10	11
Mortgage loans that were in non accrual status	$ 28	$ 25