Credit Quality and the Allowance for Loan and Lease Losses - Summary of the ALLL and Related Loans and Leases Classified by Portfolio Segment (Details) - USD ($) $ in Millions	Dec. 31, 2024		Dec. 31, 2023		Dec. 31, 2022	Dec. 31, 2021
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated	$ 117		$ 96
Collectively evaluated	2,235		2,226
Total ALLL	2,352	[1]	2,322	[1]	$ 2,194	$ 1,892
Individually evaluated	622		476
Collectively evaluated	119,061		116,642
Total portfolio loans and leases	119,683		117,118
Leveraged leases	248		249
Commercial Leveraged Leases
Financing Receivable, Allowance for Credit Loss [Line Items]
Total ALLL	1		2
Commercial
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated	106		90
Collectively evaluated	1,048		1,040
Total ALLL	1,154		1,130		1,127	1,102
Individually evaluated	395		281
Collectively evaluated	72,898		72,465
Total portfolio loans and leases	73,293		72,746
Residential Mortgage
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated	0		0
Collectively evaluated	146		145
Total ALLL	146		145		245	235
Individually evaluated	131		126
Collectively evaluated	17,304		16,784
Total portfolio loans and leases	17,435		16,910
Loans	108		116
Consumer
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated	11		6
Collectively evaluated	1,041		1,041
Total ALLL	1,052		1,047		$ 822	$ 555
Individually evaluated	96		69
Collectively evaluated	28,859		27,393
Total portfolio loans and leases	$ 28,955		$ 27,462

[1] Includes $51 and $55 of other short-term investments, $1,000 and $1,573 of portfolio loans and leases, $(19) and $(28) of ALLL, $5 and $10 of other assets, $12 and $14 of other liabilities and $889 and $1,409 of long-term debt from consolidated VIEs that are included in their respective captions above at December 31, 2024 and 2023, respectively. For further information, refer to Note 12.