Deferred Policy Acquisition Costs and Value of Business Acquired - Rollforward (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Beginning balance	$ 288	$ 536	$ 536
Deferrals of commissions and expenses	13	13
Amortization:
Amortization, excluding unlocking	(22)	(17)
Unlocking	(3)	0
Interest accrued	9	9
Net amortization included in the Condensed Consolidated Statements of Operations	(16)	(8)
Change due to unrealized capital gains/losses on available-for-sale securities	177	(113)
Ending balance	464	428	288
Movement Analysis Of Value of Business Acquired VOBA [Roll Forward]
Beginning balance	305	551	551
Deferrals of commissions and expenses	0	2
Amortization, excluding unlocking	(21)	(16)
Unlocking	(9)	9
Interest accrued	9	9
Net amortization included in the Condensed Consolidated Statements of Operations	(21)	2
Change due to unrealized capital gains/losses on available-for-sale securities	178	(107)
Ending balance	462	448	305
Movement Analysis of Deferred Policy Acquisition Costs and Value of Business Acquired (VOBA) [Roll Forward]
Beginning balance	593	1,087	1,087
Deferrals of commissions and expenses	13	15
Amortization, excluding unlocking	(43)	(33)
Unlocking	(12)	9
Interest accrued	18	18
Net amortization included in the Condensed Consolidated Statements of Operations	(37)	(6)	(6)
Change due to unrealized capital gains/losses on available-for-sale securities	355	(220)
Ending balance	$ 926	$ 876	593
Minimum
Movement Analysis of Deferred Policy Acquisition Costs and Value of Business Acquired (VOBA) [Roll Forward]
Value of Business Acquired (VOBA), Interest accrued percentage	5.50%	5.50%
Maximum
Movement Analysis of Deferred Policy Acquisition Costs and Value of Business Acquired (VOBA) [Roll Forward]
Value of Business Acquired (VOBA), Interest accrued percentage	7.00%	7.00%
Accounting Standards Update 2016-13
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Beginning balance	$ 2
Amortization:
Ending balance			2
Movement Analysis Of Value of Business Acquired VOBA [Roll Forward]
Beginning balance	0
Ending balance			0
Movement Analysis of Deferred Policy Acquisition Costs and Value of Business Acquired (VOBA) [Roll Forward]
Beginning balance	$ 2
Ending balance			$ 2