DAC, VOBA, DSI, and DFEL (VOBA) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Changes in VOBA [Roll Forward]
Balance as of beginning-of-year		$ 891	$ 893	$ 649
Business acquired (sold) through reinsurance				(22)
Deferrals		7	3	8
Amortization:
Amortization, excluding unlocking		(105)	(108)	(129)
Unlocking		(48)	36	(82)
Accretion of interest	[1]	52	52	56
Adjustment related to realized (gains) losses		(1)	(2)	(1)
Adjustment related to unrealized (gains) losses		(280)	17	414
Balance as of end-of-year		$ 516	$ 891	$ 893
Interest accrual rate, low end		4.20%
Interest accrual rate, high end		6.90%

[1] The interest accrual rates utilized to calculate the accretion of interest ranged from 4.2% to 6.9%.