Loans and Leases - Balances Of Commercial Loan Portfolio Classes, Disaggregated By PD Grade (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Mar. 31, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans, net of unearned income	$ 58,232	$ 58,600
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans, net of unearned income	33,104	33,951
Commercial and industrial | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, originated year one	9,331	2,408
Financing receivable, originated year two	5,308	8,131
Financing receivable, originated year three	2,812	4,717
Financing receivable, originated year four	1,829	2,349
Financing receivable, originated year five	1,240	1,663
Financing receivable, originated prior to year five	2,267	3,213
LMC, Non-Revolving Loans	5,404	5,530
Revolving Loans	4,793	5,872
Revolving Loans converted to term loans	120	68
Total loans, net of unearned income	33,104	33,951
Revolving loans converted to term loan during period	50
Commercial and industrial | PD Grade 1 -12 | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, originated year one	9,060	2,368
Financing receivable, originated year two	5,138	7,915
Financing receivable, originated year three	2,628	4,572
Financing receivable, originated year four	1,748	2,174
Financing receivable, originated year five	1,161	1,600
Financing receivable, originated prior to year five	2,145	3,038
LMC, Non-Revolving Loans	5,404	5,530
Revolving Loans	4,571	5,535
Revolving Loans converted to term loans	60	14
Total loans, net of unearned income	31,915	32,746
Commercial and industrial | PD Grade 13 | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, originated year one	89	5
Financing receivable, originated year two	93	68
Financing receivable, originated year three	70	65
Financing receivable, originated year four	31	51
Financing receivable, originated year five	37	28
Financing receivable, originated prior to year five	64	81
LMC, Non-Revolving Loans	0	0
Revolving Loans	127	189
Revolving Loans converted to term loans	1	7
Total loans, net of unearned income	512	494
Commercial and industrial | PD Grade 14 15 16 | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, originated year one	182	35
Financing receivable, originated year two	77	148
Financing receivable, originated year three	114	80
Financing receivable, originated year four	50	124
Financing receivable, originated year five	42	35
Financing receivable, originated prior to year five	58	94
LMC, Non-Revolving Loans	0	0
Revolving Loans	95	148
Revolving Loans converted to term loans	59	47
Total loans, net of unearned income	677	711
Commercial real estate | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans, net of unearned income	12,275	12,470
Commercial real estate | CRE | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, originated year one	2,555	514
Financing receivable, originated year two	3,348	2,438
Financing receivable, originated year three	1,888	3,400
Financing receivable, originated year four	1,257	1,811
Financing receivable, originated year five	1,044	1,144
Financing receivable, originated prior to year five	1,887	2,818
Revolving Loans	277	345
Revolving Loans converted to term loans	19	0
Total loans, net of unearned income	12,275	12,470
Commercial real estate | PD Grade 1 -12 | CRE | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, originated year one	2,477	514
Financing receivable, originated year two	3,311	2,346
Financing receivable, originated year three	1,750	3,350
Financing receivable, originated year four	1,140	1,612
Financing receivable, originated year five	946	1,024
Financing receivable, originated prior to year five	1,800	2,652
Revolving Loans	259	320
Revolving Loans converted to term loans	19	0
Total loans, net of unearned income	11,702	11,818
Commercial real estate | PD Grade 13 | CRE | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, originated year one	48	0
Financing receivable, originated year two	24	74
Financing receivable, originated year three	117	38
Financing receivable, originated year four	75	178
Financing receivable, originated year five	71	77
Financing receivable, originated prior to year five	54	109
Revolving Loans	0	0
Revolving Loans converted to term loans	0	0
Total loans, net of unearned income	389	476
Commercial real estate | PD Grade 14 15 16 | CRE | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, originated year one	30	0
Financing receivable, originated year two	13	18
Financing receivable, originated year three	21	12
Financing receivable, originated year four	42	21
Financing receivable, originated year five	27	43
Financing receivable, originated prior to year five	33	57
Revolving Loans	18	25
Revolving Loans converted to term loans	0	0
Total loans, net of unearned income	$ 184	$ 176