Business Segments - Summary of Accounting Change Impact (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2025		Sep. 30, 2024	Sep. 30, 2025		Sep. 30, 2024	Dec. 31, 2024	[1]
Segment Reporting Information [Line Items]
Goodwill	$ 458	[1]	$ 458	$ 458	[1]	$ 458	$ 458
Operating Segments
Segment Reporting Information [Line Items]
Segment profit (loss) before tax	396		91	973		603
Segment total assets	182,646		181,011	182,646		181,011
Segment total deposits	115,618		115,774	115,618		115,774
IWPB | Operating Segments
Segment Reporting Information [Line Items]
Segment profit (loss) before tax	56		(26)	154		70
Segment total assets	38,262		38,385	38,262		38,385
Segment total deposits	25,899		28,903	25,899		28,903
CIB | Operating Segments
Segment Reporting Information [Line Items]
Segment profit (loss) before tax	374		142	931		670
Segment total assets	139,411		138,348	139,411		138,348
Segment total deposits	89,719		86,871	89,719		86,871
CC | Operating Segments
Segment Reporting Information [Line Items]
Segment profit (loss) before tax	(34)		(25)	(112)		(137)
Segment total assets	4,973		4,278	4,973		4,278
Segment total deposits	$ 0		0	$ 0		0
As Previously Reported | IWPB | Operating Segments
Segment Reporting Information [Line Items]
Segment profit (loss) before tax			(26)			70
Segment total assets			38,385			38,385
Segment total deposits			28,903			28,903
As Previously Reported | CMB | Operating Segments
Segment Reporting Information [Line Items]
Segment profit (loss) before tax			126			462
Segment total assets			54,909			54,909
Segment total deposits			43,333			43,333
Goodwill			358			358
As Previously Reported | GB | Operating Segments
Segment Reporting Information [Line Items]
Segment profit (loss) before tax			85			241
Segment total assets			10,122			10,122
Segment total deposits			40,881			40,881
As Previously Reported | MSS | Operating Segments
Segment Reporting Information [Line Items]
Segment profit (loss) before tax			7			23
Segment total assets			35,264			35,264
Segment total deposits			1,393			1,393
As Previously Reported | GBM Other | Operating Segments
Segment Reporting Information [Line Items]
Segment profit (loss) before tax			(76)			(56)
Segment total assets			38,053			38,053
Segment total deposits			1,264			1,264
As Previously Reported | CC | Operating Segments
Segment Reporting Information [Line Items]
Segment profit (loss) before tax			(25)			(137)
Segment total assets			4,278			4,278
Segment total deposits			$ 0			$ 0

[1] The following table summarizes assets and liabilities related to our consolidated variable interest entities ("VIEs") at September 30, 2025 and December 31, 2024. Assets and liabilities exclude intercompany balances that eliminate in consolidation. See Note 15, "Variable Interest Entities," for additional information. September 30, 2025December 31, 2024(in millions)AssetsOther assets$7 $11 Total assets$7 $11 LiabilitiesInterest, taxes and other liabilities$14 $4 Total liabilities$14 $4