Loans and Leases - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2024		Sep. 30, 2023	Sep. 30, 2024		Sep. 30, 2023	Jun. 30, 2024	Dec. 31, 2023		Jun. 30, 2023	Dec. 31, 2022
Accounts, Notes, Loans and Financing Receivable
Unearned income	$ 312			$ 312				$ 272
Net discount	316			316				395
Accrued interest receivable	593			593				593
Direct financing lease - interest income	10		$ 7	29		$ 20
Sales type lease - interest income	21		16	58		47
Allowance for loan and lease losses	2,305	[1]	$ 2,340	2,305	[1]	$ 2,340	$ 2,288	2,322	[1]	$ 2,327	$ 2,194
Solar energy installation loans
Accounts, Notes, Loans and Financing Receivable
Net discount	894			894				865
Commercial leases
Accounts, Notes, Loans and Financing Receivable
Allowance for loan and lease losses	14			14				13
Federal Home Loan Bank Advances
Accounts, Notes, Loans and Financing Receivable
Loans pledged	14,900			14,900				14,500
FRB Loan
Accounts, Notes, Loans and Financing Receivable
Loans pledged	$ 53,100			$ 53,100				$ 49,300

[1] Includes $50 and $55 of other short-term investments, $1,131 and $1,573 of portfolio loans and leases, $(21) and $(28) of ALLL, $8 and $10 of other assets, $13 and $14 of other liabilities and $1,008 and $1,409 of long-term debt from consolidated VIEs that are included in their respective captions above at September 30, 2024 and December 31, 2023, respectively. For further information, refer to Note 12.