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	$ 1,687
Amortized cost, due after one year through five years	7,534
Amortized cost, due after five years through ten years	13,453
Amortized cost, due after ten years	27,568
Amortized cost, Structured Securities	16,254
Fixed maturity securities, amortized cost	66,496	$ 64,079
Estimated fair value, due in one year or less	1,688
Estimated fair value, due after one year through five years	7,889
Estimated fair value, due after five years through ten years	14,687
Estimated fair value, due after ten years	35,230
Estimated fair value, Structured Securities	17,302
Fixed maturity securities, estimated fair value	$ 76,796	$ 71,036