Deferred Acquisition Costs - Additional Information (Detail) - USD ($)	3 Months Ended			9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Jun. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Deferred Policy Acquisition Costs [Line Items]
Deferred Policy acquisition costs amortization				$ 261,000,000	$ 257,000,000
Accumulated effect of net unrealized investment (gains) losses				1,717,000,000	462,000,000
Deferred acquisition costs	$ 2,342,000,000	$ 3,982,000,000		2,342,000,000	3,982,000,000	$ 3,571,000,000
Increase in future policy benefit reserves	(92,000,000)	$ (81,000,000)		(429,000,000)	(612,000,000)
Loss Recognition Testing | Immediate Fixed Annuity
Deferred Policy Acquisition Costs [Line Items]
Deferred Policy acquisition costs amortization			$ 14,000,000
Increase in future policy benefit reserves				31,000,000	$ 24,000,000
Long-term Care Insurance
Deferred Policy Acquisition Costs [Line Items]
Accumulated effect of net unrealized investment (gains) losses				1,300,000,000
Deferred acquisition costs	$ 0			0
Increase in future policy benefit reserves				$ 333,000,000