Claim and Claim Adjustment Expense Reserves - Reconciliation of Claim and Claim Adjustment Expense Reserves (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Gross reserves, beginning of year	$ 23,271	$ 24,089	$ 24,763
Ceded reserves, beginning of year	4,344	4,972	5,126
Net reserves, beginning of year	18,927	19,117	19,637
Change in net reserves due to acquisition (disposition) of subsidiaries		(13)
Net incurred claim and claim adjustment expenses:
Provision for insured events of current year	4,934	5,043	5,114
Decrease in provision for insured events of prior years	(255)	(36)	(115)
Amortization of discount	166	161	154
Total net incurred	4,845	5,168	5,153
Net payments attributable to:
Current year events	(856)	(945)	(981)
Prior year events	(4,089)	(4,355)	(4,588)
Total net payments	(4,945)	(5,300)	(5,569)
Foreign currency translation adjustment and other	(251)	(45)	(104)
Net reserves, end of year	18,576	18,927	19,117
Ceded reserves, end of year	4,087	4,344	4,972
Gross reserves, end of year	$ 22,663	$ 23,271	$ 24,089