DAC, VOBA, DSI, and DFEL (DSI) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Changes in DSI [Roll Forward]
Balance as of beginning-of-year	$ 243	$ 256	$ 240
Deferrals	29	24	29
Amortization, net of interest:
Amortization, excluding unlocking, net of interest	(30)	(32)	(33)
Unlocking	(4)	(2)	2
Adjustment related to realized (gains) losses	(1)	(1)	(1)
Adjustment related to unrealized (gains) losses	1	(2)	19
Balance as of end-of-year	$ 238	$ 243	$ 256