Loans - Wholesale Loan Portfolio, Payment Status of FDMs and Defaults (Details) - Wholesale - USD ($)	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Financing Receivable, Modified [Line Items]
FDM's that defaulted		$ 0
Secured by real estate
Financing Receivable, Modified [Line Items]
Amortized cost of FDMs during the last 12 months	$ 163,000,000	0
Commitments to lend to borrowers experiencing financial difficulty	0		$ 0
Secured by real estate | Criticized nonaccrual
Financing Receivable, Modified [Line Items]
Amortized cost of FDMs during the last 12 months	46,000,000
Secured by real estate | Current and less than 30 days past due and still accruing
Financing Receivable, Modified [Line Items]
Amortized cost of FDMs during the last 12 months	110,000,000
Secured by real estate | 30–89 days past due and still accruing
Financing Receivable, Modified [Line Items]
Amortized cost of FDMs during the last 12 months	7,000,000
Commercial and industrial
Financing Receivable, Modified [Line Items]
Amortized cost of FDMs during the last 12 months	1,428,000,000	373,000,000
FDM's that defaulted	77,000,000
Commitments to lend to borrowers experiencing financial difficulty	577,000,000		1,800,000,000
Commercial and industrial | Criticized nonaccrual
Financing Receivable, Modified [Line Items]
Amortized cost of FDMs during the last 12 months	366,000,000	157,000,000
Commercial and industrial | Current and less than 30 days past due and still accruing
Financing Receivable, Modified [Line Items]
Amortized cost of FDMs during the last 12 months	1,033,000,000	212,000,000
Commercial and industrial | 30–89 days past due and still accruing
Financing Receivable, Modified [Line Items]
Amortized cost of FDMs during the last 12 months	29,000,000	4,000,000
Other
Financing Receivable, Modified [Line Items]
Amortized cost of FDMs during the last 12 months	599,000,000	63,000,000
Commitments to lend to borrowers experiencing financial difficulty	29,000,000		$ 4,000,000
Other | Criticized nonaccrual
Financing Receivable, Modified [Line Items]
Amortized cost of FDMs during the last 12 months	204,000,000	63,000,000
Other | Current and less than 30 days past due and still accruing
Financing Receivable, Modified [Line Items]
Amortized cost of FDMs during the last 12 months	383,000,000	0
Other | 30–89 days past due and still accruing
Financing Receivable, Modified [Line Items]
Amortized cost of FDMs during the last 12 months	$ 12,000,000	$ 0