Deferred Acquisition Costs - Deferred Policy Acquisition Costs and Asset Reconciliation (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Deferred policy acquisition costs asset, beginning of period	$ 691	$ 660	$ 670	$ 637
Capitalized deferred policy acquisition costs	266	249	511	488
Deferred Policy Acquisition Costs, Amortization Expense	(236)	(229)	(470)	(443)
Deferred Policy Acquisition Cost, Amortization Expense, Other	7	(2)	17	(4)
Deferred policy acquisition costs asset, end of period	728	678	728	678
Life Insurance Product Line [Member]
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Deferred policy acquisition costs asset, beginning of period	245	232	232	229
Capitalized deferred policy acquisition costs	15	12	28	25
Deferred Policy Acquisition Costs, Amortization Expense	(11)	(12)	(21)	(20)
Deferred Policy Acquisition Cost, Amortization Expense, Other	7	(2)	17	(4)
Deferred policy acquisition costs asset, end of period	256	230	256	230
Consolidated Property and Casualty Insurance Entity
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Deferred policy acquisition costs asset, beginning of period	446	428	438	408
Capitalized deferred policy acquisition costs	251	237	483	463
Deferred Policy Acquisition Costs, Amortization Expense	(225)	(217)	(449)	(423)
Deferred policy acquisition costs asset, end of period	$ 472	$ 448	$ 472	$ 448