Investments (Maturities of Fixed Maturity Securities) (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Amortized cost, due in one year or less	$ 1,606
Amortized cost, due after one year through five years	7,425
Amortized cost, due after five years through ten years	13,230
Amortized cost, due after ten years	27,076
Amortized cost, Structured Securities	16,087
Fixed maturity securities, amortized cost	65,424	$ 63,083
Estimated fair value, due in one year or less	1,609
Estimated fair value, due after one year through five years	7,775
Estimated fair value, due after five years through ten years	14,439
Estimated fair value, due after ten years	34,650
Estimated fair value, Structured Securities	17,132
Fixed maturity securities, estimated fair value	$ 75,605	$ 69,977