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	$ 1,465
Amortized cost, due after one year through five years	7,192
Amortized cost, due after five years through ten years	13,928
Amortized cost, due after ten years	28,226
Amortized cost, Structured Securities	16,181
Fixed maturity securities, amortized cost	66,992	$ 63,083
Estimated fair value, due in one year or less	1,480
Estimated fair value, due after one year through five years	7,623
Estimated fair value, due after five years through ten years	15,397
Estimated fair value, due after ten years	36,227
Estimated fair value, Structured Securities	17,412
Fixed maturity securities, estimated fair value	$ 78,139	$ 69,977