Derivative Instruments - Effect of Fair Value and Cash Flow Hedge Accounting on Consolidated Statement of Income (Parenthetical) (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Derivative Instrument Detail [Abstract]
Gains (losses) recognized in earnings related discontinuance of cash flow hedges	$ 13	$ 18	$ 40	$ 24

Amount, before tax, of reclassification from accumulated other comprehensive income (AOCI) for gain (loss) from discontinuance of cash flow hedge included in assessment of hedge effectiveness.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=125515794&loc=SL5624171-113959

Name:	us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeReclassificationForDiscontinuanceBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration