Loans and Leases - Balances Of Commercial Loan Portfolio Classes, Disaggregated By PD Grade (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	$ 56,687	$ 58,232
Commercial and industrial | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, originated year one	4,265	9,331
Financing receivable, originated year two	6,336	5,308
Financing receivable, originated year three	4,296	2,812
Financing receivable, originated year four	2,151	1,829
Financing receivable, originated year five	1,496	1,240
Financing receivable, originated prior to year five	2,944	2,267
LMC, Non-Revolving Loans	4,876	5,404
Revolving loans	6,099	4,793
Revolving Loans converted to term loans	65	120
Loans and leases	32,528	33,104
Revolving loans converted to term loan during period	0	50
Commercial and industrial | PD Grade 1 -12 | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, originated year one	4,191	9,060
Financing receivable, originated year two	6,164	5,138
Financing receivable, originated year three	4,163	2,628
Financing receivable, originated year four	1,958	1,748
Financing receivable, originated year five	1,448	1,161
Financing receivable, originated prior to year five	2,758	2,145
LMC, Non-Revolving Loans	4,876	5,404
Revolving loans	5,827	4,571
Revolving Loans converted to term loans	13	60
Loans and leases	31,398	31,915
Commercial and industrial | PD Grade 13 | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, originated year one	22	89
Financing receivable, originated year two	50	93
Financing receivable, originated year three	56	70
Financing receivable, originated year four	75	31
Financing receivable, originated year five	24	37
Financing receivable, originated prior to year five	75	64
LMC, Non-Revolving Loans	0	0
Revolving loans	155	127
Revolving Loans converted to term loans	5	1
Loans and leases	462	512
Commercial and industrial | PD Grade 14 15 16 | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, originated year one	52	182
Financing receivable, originated year two	122	77
Financing receivable, originated year three	77	114
Financing receivable, originated year four	118	50
Financing receivable, originated year five	24	42
Financing receivable, originated prior to year five	111	58
LMC, Non-Revolving Loans	0	0
Revolving loans	117	95
Revolving Loans converted to term loans	47	59
Loans and leases	668	677
Commercial real estate | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	12,292	12,275
Commercial real estate | CRE | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, originated year one	1,245	2,555
Financing receivable, originated year two	2,387	3,348
Financing receivable, originated year three	3,309	1,888
Financing receivable, originated year four	1,614	1,257
Financing receivable, originated year five	983	1,044
Financing receivable, originated prior to year five	2,429	1,887
Revolving loans	325	277
Revolving Loans converted to term loans	0	19
Loans and leases	12,292	12,275
Commercial real estate | PD Grade 1 -12 | CRE | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, originated year one	1,238	2,477
Financing receivable, originated year two	2,295	3,311
Financing receivable, originated year three	3,248	1,750
Financing receivable, originated year four	1,399	1,140
Financing receivable, originated year five	873	946
Financing receivable, originated prior to year five	2,273	1,800
Revolving loans	299	259
Revolving Loans converted to term loans	0	19
Loans and leases	11,625	11,702
Commercial real estate | PD Grade 13 | CRE | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, originated year one	3	48
Financing receivable, originated year two	74	24
Financing receivable, originated year three	50	117
Financing receivable, originated year four	190	75
Financing receivable, originated year five	70	71
Financing receivable, originated prior to year five	101	54
Revolving loans	0	0
Revolving Loans converted to term loans	0	0
Loans and leases	488	389
Commercial real estate | PD Grade 14 15 16 | CRE | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, originated year one	4	30
Financing receivable, originated year two	18	13
Financing receivable, originated year three	11	21
Financing receivable, originated year four	25	42
Financing receivable, originated year five	40	27
Financing receivable, originated prior to year five	55	33
Revolving loans	26	18
Revolving Loans converted to term loans	0	0
Loans and leases	$ 179	$ 184