Deferred Acquisition Costs - Deferred Policy Acquisition Costs and Asset Reconciliation (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Movement Analysis of Deferred Policy Acquisition Costs
Deferred policy acquisition costs asset, beginning of period	$ 880	$ 827	$ 805	$ 774
Capitalized deferred policy acquisition costs	340	306	666	601
Amortized deferred policy acquisition costs	(295)	(276)	(572)	(541)
Shadow deferred policy acquisition costs	(1)	(23)	25	0
Deferred policy acquisition costs asset, end of period	924	834	924	834
Consolidated Property And Casualty Insurance
Movement Analysis of Deferred Policy Acquisition Costs
Deferred policy acquisition costs asset, beginning of period	586	536	542	512
Capitalized deferred policy acquisition costs	325	292	637	572
Amortized deferred policy acquisition costs	(281)	(261)	(549)	(517)
Deferred policy acquisition costs asset, end of period	630	567	630	567
Life Insurance Segment
Movement Analysis of Deferred Policy Acquisition Costs
Deferred policy acquisition costs asset, beginning of period	294	291	263	262
Capitalized deferred policy acquisition costs	15	14	29	29
Amortized deferred policy acquisition costs	(14)	(15)	(23)	(24)
Shadow deferred policy acquisition costs	(1)	(23)	25	0
Deferred policy acquisition costs asset, end of period	$ 294	$ 267	$ 294	$ 267