Changes in Liability for Policy and Contract Claims (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Beginning balance	$ 9,594
Ending balance	10,379	$ 9,594
Long-term Care Insurance
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Beginning balance	8,548	8,034	$ 6,749
Less reinsurance recoverables	(2,292)	(2,310)	(2,055)
Net beginning balance	6,256	5,724	4,694
Current year	2,548	2,234	2,066
Prior years	130	(183)	377
Total incurred	2,678	2,051	2,443
Current year	(201)	(176)	(166)
Prior years	(1,814)	(1,644)	(1,506)
Total paid	(2,015)	(1,820)	(1,672)
Interest on liability for policy and contract claims	335	301	259
Net ending balance	7,254	6,256	5,724
Add reinsurance recoverables	2,262	2,292	2,310
Ending balance	$ 9,516	$ 8,548	$ 8,034