Deferred Acquisition Costs - Deferred Policy Acquisition Costs and Asset Reconciliation (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Movement Analysis of Deferred Policy Acquisition Costs
Deferred policy acquisition costs asset, beginning of period	$ 924	$ 834	$ 805	$ 774
Capitalized deferred policy acquisition costs	302	272	968	873
Amortized deferred policy acquisition costs	(312)	(286)	(884)	(827)
Shadow deferred policy acquisition costs	1	(3)	26	(3)
Deferred policy acquisition costs asset, end of period	915	817	915	817
Consolidated Property And Casualty Insurance
Movement Analysis of Deferred Policy Acquisition Costs
Deferred policy acquisition costs asset, beginning of period	630	567	542	512
Capitalized deferred policy acquisition costs	287	258	924	830
Amortized deferred policy acquisition costs	(300)	(274)	(849)	(791)
Deferred policy acquisition costs asset, end of period	617	551	617	551
Life Insurance Segment
Movement Analysis of Deferred Policy Acquisition Costs
Deferred policy acquisition costs asset, beginning of period	294	267	263	262
Capitalized deferred policy acquisition costs	15	14	44	43
Amortized deferred policy acquisition costs	(12)	(12)	(35)	(36)
Shadow deferred policy acquisition costs	1	(3)	26	(3)
Deferred policy acquisition costs asset, end of period	$ 298	$ 266	$ 298	$ 266