Investments (Fair Value of Trading Securities) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	$ 4,673	$ 1,950
Corporate Bonds [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	2,947	1,639
U.S. Government Bonds [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	45	43
Foreign Government Bonds [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	44	23
RMBS [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	170	79
CMBS [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	163	7
ABS [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	1,238	121
State And Municipal Bonds [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	17	16
Hybrid And Redeemable Preferred Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	$ 49	$ 22