Accumulated Other Comprehensive Income (Loss) - Components of AOCI (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, net of OTTI	$ 1,030		$ 786
Derivatives	126		93
DAC/VOBA and Sales inducements adjustment on available-for-sale securities	(293)		(240)
Premium deficiency reserve adjustment	(86)		(82)
Unrealized capital gains (losses), before tax	777		557
Deferred income tax asset (liability)	(35)		(123)
Unrealized capital gains (losses), after tax	742		434
Pension and other postretirement benefits liability, net of tax	5		4
AOCI	$ 747	$ 108	$ 438