Investments (Past Due and Interest Accrual Status of Mortgage Loans) (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment, Aging [Abstract]
Past Due Status of Mortgage Loans	$ 564	$ 184
Mortgage loans that were in non accrual status	628	279
Commercial
Financing Receivable, Recorded Investment, Aging [Abstract]
Past Due Status of Mortgage Loans	10	10
Mortgage loans that were in non accrual status	70	75
Agricultural
Financing Receivable, Recorded Investment, Aging [Abstract]
Past Due Status of Mortgage Loans	33	1
Mortgage loans that were in non accrual status	46	41
Residential
Financing Receivable, Recorded Investment, Aging [Abstract]
Past Due Status of Mortgage Loans	521	173
Mortgage loans that were in non accrual status	$ 512	$ 163