Investments (Past Due and Interest Accrual Status of Mortgage Loans) (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment, Aging [Abstract]
Past Due	$ 377	$ 184
Nonaccrual Status	301	279
Commercial
Financing Receivable, Recorded Investment, Aging [Abstract]
Past Due	9	10
Nonaccrual Status	7	75
Agricultural
Financing Receivable, Recorded Investment, Aging [Abstract]
Past Due	109	1
Nonaccrual Status	46	41
Residential
Financing Receivable, Recorded Investment, Aging [Abstract]
Past Due	259	173
Nonaccrual Status	$ 248	$ 163