Deferred Acquisition Costs - Deferred Policy Acquisition Costs and Asset Reconciliation (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Deferred policy acquisition costs asset, beginning of period	$ 670	$ 637
Capitalized deferred policy acquisition costs	245	239
Deferred Policy Acquisition Costs, Amortization Expense	(234)	(214)
Deferred Policy Acquisition Cost, Amortization Expense, Other	10	(2)
Deferred policy acquisition costs asset, end of period	691	660
Life Insurance Product Line [Member]
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Deferred policy acquisition costs asset, beginning of period	232	229
Capitalized deferred policy acquisition costs	13	13
Deferred Policy Acquisition Costs, Amortization Expense	(10)	(8)
Deferred Policy Acquisition Cost, Amortization Expense, Other	10	(2)
Deferred policy acquisition costs asset, end of period	245	232
Consolidated Property and Casualty Insurance Entity
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Deferred policy acquisition costs asset, beginning of period	438	408
Capitalized deferred policy acquisition costs	232	226
Deferred Policy Acquisition Costs, Amortization Expense	(224)	(206)
Deferred policy acquisition costs asset, end of period	$ 446	$ 428