Investments (Maturities of Fixed Maturity Securities) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Amortized cost, due in one year or less	$ 1,465
Amortized cost, due after one year through five years	7,207
Amortized cost, due after five years through ten years	14,328
Amortized cost, due after ten years	29,954
Amortized cost, Structured Securities	16,529
Fixed maturity securities, amortized cost	69,483	$ 63,083
Estimated fair value, due in one year or less	1,483
Estimated fair value, due after one year through five years	7,745
Estimated fair value, due after five years through ten years	16,074
Estimated fair value, due after ten years	38,200
Estimated fair value, Structured Securities	17,797
Fixed maturity securities, estimated fair value	$ 81,299	$ 69,977