Loans Held for Sale - Narrative (Details) - USD ($) $ in Millions		3 Months Ended			12 Months Ended
		Dec. 31, 2023	Jun. 30, 2023	Mar. 31, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale	[1]	$ 339			$ 339	$ 354
Loss on sale of loans						(9)
Revenue (losses) associated with the economic hedging program					826	(1,493)	$ 1,055
Commercial loans held for sale
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loans held-for-sale		250			250	237
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Retail Branches Sold
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale						2,148
Commercial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale		339			339	349
Valuation allowance		2			2	0
Commercial loans | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Retail Branches Sold
Accounts, Notes, Loans and Financing Receivable [Line Items]
Sales of loans held for sale				$ 37
Consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale		0			0	5
Valuation allowance		0			0	0
Consumer loans | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Retail Branches Sold
Accounts, Notes, Loans and Financing Receivable [Line Items]
Sales of loans held for sale				2,102
Consumer loans | Exit of Mass Market Retail Banking Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Sales of loans held for sale				904
Loss on sale of loans			$ 10	35
Commercial Real Estate Loans Transferred From Portfolio Loans To Held For Sale | Commercial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans sold		439
Loans Transferred From Portfolio Loans to Held For Sale | Commercial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale		89			89	112
Residential mortgages | Consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale		0			0	5
Residential mortgages | Consumer loans | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Retail Branches Sold
Accounts, Notes, Loans and Financing Receivable [Line Items]
Sales of loans held for sale				1,665
Residential mortgages | Consumer loans | Exit of Mass Market Retail Banking Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Sales of loans held for sale				865
Home equity mortgages | Consumer loans | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Retail Branches Sold
Accounts, Notes, Loans and Financing Receivable [Line Items]
Sales of loans held for sale				185
Home equity mortgages | Consumer loans | Exit of Mass Market Retail Banking Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Sales of loans held for sale				39
Credit cards | Consumer loans | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Retail Branches Sold
Accounts, Notes, Loans and Financing Receivable [Line Items]
Sales of loans held for sale				168
Other consumer | Consumer loans | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Retail Branches Sold
Accounts, Notes, Loans and Financing Receivable [Line Items]
Sales of loans held for sale				$ 84
Global banking | Commercial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale		$ 339			339	349
Global banking | Commercial loans | Restructuring Plan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans sold						44
Loss on sale of loans						(21)
Other Income (Loss)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revenue (losses) associated with the economic hedging program					0	7	(2)
Other Income (Loss) | Commercial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Lower of amortized cost or fair value (reversal)					2	8	7
Other Income (Loss) | Consumer loans | Exit of Mass Market Retail Banking Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Lower of amortized cost or fair value (reversal)						$ 11	$ 7
Other Income (Loss) | Commercial Real Estate Loans Transferred From Portfolio Loans To Held For Sale | Commercial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Lower of amortized cost or fair value (reversal)					$ 30

[1] The following table summarizes assets and liabilities related to our consolidated variable interest entities ("VIEs") at December 31, 2023 and 2022. Assets and liabilities exclude intercompany balances that eliminate in consolidation. See Note 27, "Variable Interest Entities," for additional information. At December 31,20232022(in millions)AssetsLoans, net$— $162 Other assets23 44 Total assets$23 $206 LiabilitiesInterest, taxes and other liabilities$17 $22 Total liabilities$17 $22