Investments (Fair Value of Trading Securities) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	$ 1,712	$ 1,854
Corporate bonds [Member] | Fixed maturity AFS securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	1,360	1,416
ABS [Member] | Fixed maturity AFS securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	19	25
U.S. government bonds [Member] | Fixed maturity AFS securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	164	221
Foreign government bonds [Member] | Fixed maturity AFS securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	23	25
RMBS [Member] | Fixed maturity AFS securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	97	104
CMBS [Member] | Fixed maturity AFS securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	2	4
CLOs [Member] | Fixed maturity AFS securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	6	10
State and municipal bonds [Member] | Fixed maturity AFS securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	18	18
Hybrid and redeemable preferred securities [Member] | Fixed maturity AFS securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	$ 23	$ 31