Intangible Assets - Narrative (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Unearned Revenue, Net	$ 26
Unearned Revenue, Unlocking Adjustment	2
Goodwill	467		$ 467
Deferred Sales Inducement Cost, Unrealized Gain (Loss) on Investment	5	$ 0
Unearned Revenue, Additions	(28)
Unearned Revenue, Amortization Expense	18
Unearned Revenue, Unrealized Gain (Loss) on Investment	$ (18)
Minimum
Finite-Lived Intangible Assets [Line Items]
Value of Business Acquired, Assumption, Interest Rate to Calculate Accretion on Intangible Asset	0.05%
Maximum
Finite-Lived Intangible Assets [Line Items]
Value of Business Acquired, Assumption, Interest Rate to Calculate Accretion on Intangible Asset	4.01%
Voba [Member]
Finite-Lived Intangible Assets [Line Items]
Cumulative Adjustments For Net Unrealized Investment Gains	$ 0	0
Dac [Member]
Finite-Lived Intangible Assets [Line Items]
Cumulative Adjustments For Net Unrealized Investment Gains	$ 0	$ 0