Deferred Acquisition Costs - Deferred Policy Acquisition Costs and Asset Reconciliation (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Deferred policy acquisition costs asset, beginning of period	$ 728	$ 678	$ 670	$ 637
Capitalized deferred policy acquisition costs	244	236	755	724
Deferred Policy Acquisition Costs, Amortization Expense	(231)	(237)	(701)	(680)
Deferred Policy Acquisition Cost, Amortization Expense, Other	2	(1)	19	(5)
Deferred policy acquisition costs asset, end of period	743	676	743	676
Life Insurance Product Line [Member]
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Deferred policy acquisition costs asset, beginning of period	256	230	232	229
Capitalized deferred policy acquisition costs	15	13	43	38
Deferred Policy Acquisition Costs, Amortization Expense	(6)	(17)	(27)	(37)
Deferred Policy Acquisition Cost, Amortization Expense, Other	2	(1)	19	(5)
Deferred policy acquisition costs asset, end of period	267	225	267	225
Consolidated Property and Casualty Insurance Entity
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Deferred policy acquisition costs asset, beginning of period	472	448	438	408
Capitalized deferred policy acquisition costs	229	223	712	686
Deferred Policy Acquisition Costs, Amortization Expense	(225)	(220)	(674)	(643)
Deferred policy acquisition costs asset, end of period	$ 476	$ 451	$ 476	$ 451