Deferred Acquisition Costs - Deferred Policy Acquisition Costs and Asset Reconciliation (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Movement Analysis of Deferred Policy Acquisition Costs
Deferred policy acquisition costs asset, beginning of period	$ 805	$ 774
Capitalized deferred policy acquisition costs	326	295
Amortized deferred policy acquisition costs	(277)	(265)
Shadow deferred policy acquisition costs	26	23
Deferred policy acquisition costs asset, end of period	880	827
Consolidated Property And Casualty Insurance
Movement Analysis of Deferred Policy Acquisition Costs
Deferred policy acquisition costs asset, beginning of period	542	512
Capitalized deferred policy acquisition costs	312	280
Amortized deferred policy acquisition costs	(268)	(256)
Deferred policy acquisition costs asset, end of period	586	536
Life Insurance Segment
Movement Analysis of Deferred Policy Acquisition Costs
Deferred policy acquisition costs asset, beginning of period	263	262
Capitalized deferred policy acquisition costs	14	15
Amortized deferred policy acquisition costs	(9)	(9)
Shadow deferred policy acquisition costs	26	23
Deferred policy acquisition costs asset, end of period	$ 294	$ 291