Investments Investments (Details) - Contractual Maturities - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Investments [Abstract]
Fixed maturities, due in one year or less, amortized cost	$ 4,489
Fixed maturities, due after 1 year through 5 years, amortized cost	17,020
Fixed maturities, due after 5 years through 10 years, amortized cost	17,030
Fixed maturities, due after 10 years, amortized cost	22,505
Fixed maturities excluding mortgage-backed securities, collateralized mortgage obligations and pass-through securities, amortized cost	61,044
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities, amortized cost	2,557
Fixed maturities, amortized cost	63,601	$ 61,316
Fixed maturities, due in one year or less, fair value	4,505
Fixed maturities, due after 1 year through 5 years, fair value	17,021
Fixed maturities, due after 5 years through 10 years, fair value	16,785
Fixed maturities, due after 10 years, fair value	22,580
Fixed maturities excluding mortgage-backed securities, collateralized mortgage obligations and pass-through securities, fair value	60,891
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities, fair value	2,573
Fixed maturities, at fair value	$ 63,464	$ 62,694