Investments (Maturities of Fixed Maturity Securities) (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Amortized cost, due in one year or less	$ 1,414
Amortized cost, due after one year through five years	7,353
Amortized cost, due after five years through ten years	15,160
Amortized cost, due after ten years	30,637
Amortized cost, Structured Securities	16,518
Fixed maturity securities, amortized cost	71,082	$ 69,483
Estimated fair value, due in one year or less	1,437
Estimated fair value, due after one year through five years	7,812
Estimated fair value, due after five years through ten years	16,181
Estimated fair value, due after ten years	35,075
Estimated fair value, Structured Securities	17,404
Fixed maturity securities	$ 77,909	$ 81,299