Collateralized Agreements and Financings - Offsetting Arrangements (Parenthetical) (Detail) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020
Collateralized Agreements And Financings [Abstract]
Securities borrowed at fair value	$ 34,437	$ 28,898
Securities loaned at fair value	$ 7,298	$ 1,053	$ 7,298

Fair value portion of securities that an entity sells and agrees to repurchase at a specified date for a specified price.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=123594938&loc=d3e13433-108611

Name:	us-gaap_SecuritiesLoanedOrSoldUnderAgreementsToRepurchaseFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant