Investments - Impaired Commercial Mortgage Loans (Details) (Mortgage Loans on Real Estate [Member], USD $)
In Millions, unless otherwise specified
3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Dec. 31, 2014
Mortgage Loans on Real Estate [Member]
     
Financing Receivable, Impaired [Line Items]      
Impaired commercial mortgage loans with related allowance, gross $ 83   $ 147
Impaired commercial mortgage loans with no related allowance, gross 31   31
Impaired commercial mortgage loans, gross 114   178
Impaired commercial mortgage loans, reserves (8)   (12)
Impaired commercial mortgage loans with related allowance, net 75   135
Impaired commercial mortgage loans, net 106   166
Average recorded investment in impaired mortgage loans 146 120  
Interest income on non-accrual commercial mortgage loans that would have been recognized if original terms had been met        
Interest income on impaired commercial mortgage loans