Loans and Leases - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024		Mar. 31, 2023	Dec. 31, 2023		Dec. 31, 2022
Accounts, Notes, Loans and Financing Receivable
Unearned income	$ 275			$ 272
Net discount	375			395
Accrued interest receivable	595			593
Direct financing lease - interest income	9		$ 6
Sales type lease - interest income	18		15
Allowance for loan and lease losses	2,318	[1]	$ 2,215	2,322	[1]	$ 2,194
Solar energy installation loans
Accounts, Notes, Loans and Financing Receivable
Net discount	875			865
Commercial Leases
Accounts, Notes, Loans and Financing Receivable
Allowance for loan and lease losses	15			13
Federal Home Loan Bank Advances
Accounts, Notes, Loans and Financing Receivable
Loans pledged	14,400			14,500
FRB Loan
Accounts, Notes, Loans and Financing Receivable
Loans pledged	$ 49,300			$ 49,300

[1] Includes $48 and $55 of other short-term investments, $1,420 and $1,573 of portfolio loans and leases, $(26) and $(28) of ALLL, $29 and $10 of other assets, $25 and $14 of other liabilities and $1,274 and $1,409 of long-term debt from consolidated VIEs that are included in their respective captions above at March 31, 2024 and December 31, 2023, respectively. For further information, refer to Note 11.