Accumulated Other Comprehensive Income (Loss) - Components of AOCI (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Components Of Accumulated Other Comprehensive Income Loss [Line Items]
Derivatives	$ 127	$ 258	$ 259
DAC/VOBA adjustment on available-for-sale securities	(1,471)	(1,083)	(765)
Premium deficiency reserve	(190)	(54)	0
Sales inducements adjustment on available-for-sale securities	(278)	(169)	(23)
Other	(18)	(31)	(31)
Unrealized capital gains (losses), before tax	3,556	2,367	1,594
Deferred income tax asset (liability)	(840)	(472)	(202)
Net unrealized capital gains (losses)	2,716	1,895	1,392
Pension and other post-employment benefits liability, net of tax	15	26	33
AOCI	2,731	1,921	1,425
Fixed maturities
Components Of Accumulated Other Comprehensive Income Loss [Line Items]
Fixed maturities, net of OTTI	5,351	3,413	2,123
Equity securities
Components Of Accumulated Other Comprehensive Income Loss [Line Items]
Equity securities, available-for-sale	$ 35	$ 33	$ 31