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, 2023		Dec. 31, 2022		Dec. 31, 2021	Dec. 31, 2020
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated	$ 96		$ 122
Collectively evaluated	2,226		2,072
Total ALLL	2,322	[1]	2,194	[1]	$ 1,892	$ 2,453
Individually evaluated	476		1,388
Collectively evaluated	116,642		119,969
Total portfolio loans and leases	117,118		121,357
Leveraged leases	249		247
Commercial Leveraged Leases
Financing Receivable, Allowance for Credit Loss [Line Items]
Total ALLL	2		2
Leveraged leases	249		247
Commercial
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated	90		30
Collectively evaluated	1,040		1,097
Total ALLL	1,130		1,127		1,102	1,456
Individually evaluated	281		531
Collectively evaluated	72,465		75,858
Total portfolio loans and leases	72,746		76,389
Residential Mortgage
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated	0		47
Collectively evaluated	145		198
Total ALLL	145		245		235	294
Individually evaluated	126		560
Collectively evaluated	16,784		16,945
Total portfolio loans and leases	16,910		17,505
Loans	116		123
Consumer
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated	6		45
Collectively evaluated	1,041		777
Total ALLL	1,047		822		$ 555	$ 703
Individually evaluated	69		297
Collectively evaluated	27,393		27,166
Total portfolio loans and leases	$ 27,462		$ 27,463

[1] Includes $55 and $17 of other short-term investments, $1,573 and $185 of portfolio loans and leases, $(28) and $(2) of ALLL, $10 and $2 of other assets, $14 and $9 of other liabilities and $1,409 and $118 of long-term debt from consolidated VIEs that are included in their respective captions above at December 31, 2023 and 2022, respectively. For further information, refer to Note 12.