Investments (Details 13) - Mortgage loans, non-impaired - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Financing Receivable, Impaired [Line Items]
Fixed rate mortgage loans	$ 4,296	$ 4,332
Below 1.0
Financing Receivable, Impaired [Line Items]
Fixed rate mortgage loans	62	64
1.0 - 1.25
Financing Receivable, Impaired [Line Items]
Fixed rate mortgage loans	344	382
1.26 - 1.50
Financing Receivable, Impaired [Line Items]
Fixed rate mortgage loans	1,222	1,219
Above 1.50
Financing Receivable, Impaired [Line Items]
Fixed rate mortgage loans	$ 2,668	$ 2,667