Variable Interest Entities (Detail) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Variable Interest Entity [Line Items]
Assets	$ 29,097	$ 29,345	$ 27,743
Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Aggregate investment balance	178	228
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Assets	117	114
Investment In Low Income Housing Properties [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Equity method investments debt balance	156	210
Trust For Final Capping, Closure, Post-closure Or Environmental Remediation Obligations [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Aggregate investment balance	$ 110	$ 106