Investments (Maturities of Fixed Maturity Securities) (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Amortized cost, due in one year or less	$ 1,535
Amortized cost, due after one year through five years	7,291
Amortized cost, due after five years through ten years	14,164
Amortized cost, due after ten years	28,718
Amortized cost, Structured Securities	16,353
Fixed maturity securities, amortized cost	68,061	$ 64,079
Estimated fair value, due in one year or less	1,549
Estimated fair value, due after one year through five years	7,729
Estimated fair value, due after five years through ten years	15,661
Estimated fair value, due after ten years	36,811
Estimated fair value, Structured Securities	17,588
Fixed maturity securities, estimated fair value	$ 79,338	$ 71,036