Deferred Acquisition Costs - Deferred Policy Acquisition Costs and Asset Reconciliation (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Deferred policy acquisition costs asset, beginning of period	$ 678	$ 624	$ 637	$ 616
Capitalized deferred policy acquisition costs	236	227	724	679
Deferred Policy Acquisition Costs, Amortization Expense	(237)	(222)	(680)	(648)
Deferred Policy Acquisition Cost, Amortization Expense, Other	(1)	(2)	(5)	(20)
Deferred policy acquisition costs asset, end of period	676	627	676	627
Life Insurance Product Line [Member]
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Deferred policy acquisition costs asset, beginning of period	230	212	229	228
Capitalized deferred policy acquisition costs	13	11	38	35
Deferred Policy Acquisition Costs, Amortization Expense	(17)	(15)	(37)	(37)
Deferred Policy Acquisition Cost, Amortization Expense, Other	(1)	(2)	(5)	(20)
Deferred policy acquisition costs asset, end of period	225	206	225	206
Consolidated Property and Casualty Insurance Entity
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Deferred policy acquisition costs asset, beginning of period	448	412	408	388
Capitalized deferred policy acquisition costs	223	216	686	644
Deferred Policy Acquisition Costs, Amortization Expense	(220)	(207)	(643)	(611)
Deferred policy acquisition costs asset, end of period	$ 451	$ 421	$ 451	$ 421