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	Jun. 30, 2024		Mar. 31, 2024	Dec. 31, 2023		Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated	$ 93			$ 96
Collectively evaluated	2,195			2,226
Total ALLL	2,288	[1]	$ 2,318	2,322	[1]	$ 2,327	$ 2,215	$ 2,194
Individually evaluated	416			476
Collectively evaluated	116,054			116,642
Total portfolio loans and leases	116,470			117,118
Leveraged leases	246			249
Commercial Leveraged Leases
Financing Receivable, Allowance for Credit Loss [Line Items]
Total ALLL	2			2
Commercial
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated	88			90
Collectively evaluated	1,025			1,040
Total ALLL	1,113		1,141	1,130		1,199	1,143	1,127
Individually evaluated	215			281
Collectively evaluated	71,568			72,465
Total portfolio loans and leases	71,783			72,746
Residential Mortgage
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated	0			0
Collectively evaluated	136			145
Total ALLL	136		140	145		173	185	245
Individually evaluated	129			126
Collectively evaluated	16,802			16,784
Total portfolio loans and leases	16,931			16,910
Residential mortgage loans	109			116		124
Consumer
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated	5			6
Collectively evaluated	1,034			1,041
Total ALLL	1,039		$ 1,037	1,047		$ 955	$ 887	$ 822
Individually evaluated	72			69
Collectively evaluated	27,684			27,393
Total portfolio loans and leases	$ 27,756			$ 27,462

[1] Includes $52 and $55 of other short-term investments, $1,272 and $1,573 of portfolio loans and leases, $(23) and $(28) of ALLL, $7 and $10 of other assets, $13 and $14 of other liabilities and $1,136 and $1,409 of long-term debt from consolidated VIEs that are included in their respective captions above at June 30, 2024 and December 31, 2023, respectively. For further information, refer to Note 11.