v3.8.0.1
Certain Long-Duration Contracts with Guarantees (Variable Annuity, Variable Life, Variable Universal Life and Universal Life Contracts) (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Annuity Contracts | Return of net deposits | In the Event of Death    
Net Amount at Risk by Product and Guarantee [Line Items]    
Account value $ 129,231 $ 119,433
Net amount at risk $ 288 $ 493
Average attained age of contractholders 66 years 65 years
Annuity Contracts | Return of net deposits | At Annuitization / Accumulation    
Net Amount at Risk by Product and Guarantee [Line Items]    
Account value $ 100 $ 152
Net amount at risk $ 0 $ 0
Average attained age of contractholders 66 years 66 years
Annuity Contracts | Minimum return or contract value | In the Event of Death    
Net Amount at Risk by Product and Guarantee [Line Items]    
Account value $ 35,431 $ 33,843
Net amount at risk $ 2,611 $ 3,714
Average attained age of contractholders 68 years 67 years
Annuity Contracts | Minimum return or contract value | At Annuitization / Accumulation    
Net Amount at Risk by Product and Guarantee [Line Items]    
Account value $ 146,319 $ 135,462
Net amount at risk $ 3,762 $ 5,788
Average attained age of contractholders 66 years 65 years
Average period remaining until earliest expected annuitization 2 months 25 days 3 months 6 days
Variable Life, Variable Universal Life and Universal Life Contracts | No-lapse guarantees | In the Event of Death    
Net Amount at Risk by Product and Guarantee [Line Items]    
Separate account value $ 9,365 $ 8,144
General account value 15,969 14,513
Net amount at risk $ 241,598 $ 225,084
Average attained age of contractholders 55 years 56 years