Deferred Policy Acquisition Costs and Value of Business Acquired - DAC and VOBA Activity (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Beginning balance	$ 3,186,000,000	$ 3,424,000,000	$ 3,013,000,000
Deferrals of commissions and expenses	234,000,000	255,000,000	260,000,000
Amortization:
Amortization, excluding unlocking	(418,000,000)	(384,000,000)	(443,000,000)
Unlocking	(123,000,000)	(78,000,000)	(39,000,000)
Interest accrued	188,000,000	193,000,000	192,000,000
Net amortization included in Consolidated Statements of Operations	(353,000,000)	(269,000,000)	(290,000,000)
Change in unrealized capital gains/losses on available-for-sale securities	(249,000,000)	(224,000,000)	441,000,000
Ending balance	2,818,000,000	3,186,000,000	3,424,000,000
Movement Analysis Of Value of Business Acquired VOBA [Roll Forward]
Beginning balance	811,000,000	997,000,000	665,000,000
Deferrals of commissions and expenses	8,000,000	9,000,000	10,000,000
Amortization, excluding unlocking	(152,000,000)	(144,000,000)	(163,000,000)
Unlocking(1)	(89,000,000)	(78,000,000)	(6,000,000)
Interest accrued	65,000,000	76,000,000	82,000,000
Net amortization included in Consolidated Statements of Operations	(176,000,000)	(146,000,000)	(87,000,000)
Change in unrealized capital gains/losses on available-for-sale securities	(87,000,000)	(49,000,000)	409,000,000
Ending balance	556,000,000	811,000,000	997,000,000
Movement Analysis of Deferred Policy Acquisition Costs and Value of Business Acquired (VOBA) [Roll Forward]
Beginning balance	3,997,000,000	4,421,000,000	3,678,000,000
Deferrals of commissions and expenses	242,000,000	264,000,000	270,000,000
Amortization, excluding unlocking	(570,000,000)	(528,000,000)	(606,000,000)
Unlocking(1)	(212,000,000)	(156,000,000)	(45,000,000)
Interest accrued	253,000,000	269,000,000	274,000,000
Net amortization included in Consolidated Statements of Operations	(529,000,000)	(415,000,000)	(377,000,000)
Change in unrealized capital gains/losses on available-for-sale securities	(336,000,000)	(273,000,000)	850,000,000
Ending balance	3,374,000,000	3,997,000,000	4,421,000,000
Loss Recognition for DAC	0	3,000,000	0
Loss recognition for VOBA	$ 0	$ 4,000,000	$ 0
Minimum
Movement Analysis of Deferred Policy Acquisition Costs and Value of Business Acquired (VOBA) [Roll Forward]
Rates at which interest accrued	4.00%	4.10%	4.20%
Maximum
Movement Analysis of Deferred Policy Acquisition Costs and Value of Business Acquired (VOBA) [Roll Forward]
Rates at which interest accrued	7.40%	7.50%	7.50%
Guaranteed Minimum Interest Rates
Amortization:
Unlocking	$ (80,000,000)
Movement Analysis Of Value of Business Acquired VOBA [Roll Forward]
Unlocking(1)	$ (140,000,000)