Investments (Fair Value of Trading Securities) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	$ 1,950	$ 1,620
Corporate Bonds [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	1,639	1,335
ABS [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	17	15
U.S. Government Bonds [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	43	115
Foreign Government Bonds [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	23	23
RMBS [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	79	86
CMBS [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	7	2
CLOs [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	104	3
State And Municipal Bonds [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	16	17
Hybrid And Redeemable Preferred Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	$ 22	$ 24