Noninterest Revenue and Noninterest Expense - Components of Noninterest Expense (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Noninterest Income (Expense) [Abstract]
Legal expense	$ 28	$ 197
FDIC-related expense	$ 201	$ 99

Amount of expense for Federal Deposit Insurance Corporation (FDIC) insurance.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.14)
-URI http://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

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