Collateralized Agreements and Financings - Resale and Repurchase Agreements and Securities Borrowed and Loaned Transactions (Parenthetical) (Detail) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Collateralized Agreements And Financings [Abstract]
Securities borrowed at fair value	$ 31,680	$ 26,279
Securities loaned at fair value	$ 1,060	$ 714

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=121572278&loc=d3e13433-108611

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