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	Mar. 31, 2022		Dec. 31, 2021		Mar. 31, 2021	Dec. 31, 2020
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated	$ 173		$ 164
Collectively evaluated	1,735		1,728
Total ALLL	1,908	[1]	1,892	[1]	$ 2,208	$ 2,453
Individually evaluated	1,442		1,352
Collectively evaluated	114,278		110,544
Total portfolio loans and leases	115,720		111,896
Leveraged leases	262		285
Commercial Leveraged Leases
Financing Receivable, Allowance for Credit Loss [Line Items]
Total ALLL	2		2
Leveraged leases	262		285
Commercial
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated	82		77
Collectively evaluated	1,028		1,025
Total ALLL	1,110		1,102		1,329	1,456
Individually evaluated	572		579
Collectively evaluated	72,366		69,689
Total portfolio loans and leases	72,938		70,268
Residential Mortgage
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated	47		46
Collectively evaluated	192		189
Total ALLL	239		235		247	294
Individually evaluated	549		460
Collectively evaluated	16,450		15,783
Total portfolio loans and leases	16,999		16,243
Residential mortgage loans	145		154		153
Consumer
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated	44		41
Collectively evaluated	515		514
Total ALLL	559		555		$ 632	$ 703
Individually evaluated	321		313
Collectively evaluated	25,462		25,072
Total portfolio loans and leases	$ 25,783		$ 25,385

[1] Includes $24 and $24 of other short-term investments, $266 and $322 of portfolio loans and leases, $(2) and $(2) of ALLL, $2 and $2 of other assets, an immaterial amount and $1 of other liabilities, and $209 and $263 of long-term debt from consolidated VIEs that are included in their respective captions above at March 31, 2022 and December 31, 2021, respectively. For further information, refer to Note 11.