Accumulated Other Comprehensive Income (Loss) - Components of AOCI (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Derivatives	$ 143		$ 195
DAC/VOBA adjustment on available-for-sale securities	(570)		(1,389)
Premium deficiency reserve	(128)		0
Sales inducements and other intangibles adjustment on available-for-sale securities	(88)		(260)
Other	0		(31)
Unrealized capital gains (losses), before tax	1,162		3,427
Deferred income tax asset (liability)	(229)		(842)
Unrealized capital gains (losses), after tax	933		2,585
Pension and other post-employment benefits liability, net of tax	10		21
AOCI	943	$ 2,731	2,606
Fixed maturities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Fixed maturities, net of OTTI	1,805		4,876
Equity securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Equity securities	$ 0		$ 36