Loans and Leases - Balances Of Commercial Loan Portfolio Classes, Disaggregated By PD Grade (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans, net of unearned income	$ 59,706,531	$ 31,061,111
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans, net of unearned income	33,655,717	20,051,091
Commercial, Financial, and Industrial (a) | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	7,989,617
2019	5,957,318
2018	3,199,379
2017	1,991,389
2016	1,428,958
Prior to 2016	2,542,229
Non-Revolving Loans	5,607,068
Revolving Loans	4,821,796
Revolving Loans converted to term loans	117,963
Total loans, net of unearned income	28,048,649	15,640,208
Financing Receivable, Revolving, Converted to Term Loan During Period	40,000
Commercial, Financial, and Industrial (a) | PD Grade 1 -12 | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	7,795,816
2019	5,770,378
2018	3,036,673
2017	1,917,886
2016	1,323,236
Prior to 2016	2,414,920
Non-Revolving Loans	5,607,068
Revolving Loans	4,533,240
Revolving Loans converted to term loans	60,592
Total loans, net of unearned income	32,459,809
Commercial, Financial, and Industrial (a) | PD Grade 13 | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	86,675
2019	75,224
2018	53,067
2017	22,692
2016	45,640
Prior to 2016	80,438
Non-Revolving Loans	0
Revolving Loans	123,383
Revolving Loans converted to term loans	47,364
Total loans, net of unearned income	534,483
Commercial, Financial, and Industrial (a) | PD Grade 14 15 16 | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	107,126
2019	111,716
2018	109,639
2017	50,811
2016	60,082
Prior to 2016	46,871
Non-Revolving Loans	0
Revolving Loans	165,173
Revolving Loans converted to term loans	10,007
Total loans, net of unearned income	661,425
Commercial real estate | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans, net of unearned income	12,510,887	4,337,017
Commercial real estate | CRE | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	2,114,932
2019	3,278,452
2018	2,059,080
2017	1,486,788
2016	1,147,528
Prior to 2016	2,093,125
Revolving Loans	312,146
Revolving Loans converted to term loans	18,836
Total loans, net of unearned income	12,510,887	$ 4,332,042
Commercial real estate | PD Grade 1 -12 | CRE | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	2,099,167
2019	3,244,741
2018	1,940,046
2017	1,410,004
2016	1,056,094
Prior to 2016	2,015,504
Revolving Loans	300,752
Revolving Loans converted to term loans	18,836
Total loans, net of unearned income	12,085,144
Commercial real estate | PD Grade 13 | CRE | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	15,089
2019	31,230
2018	97,016
2017	35,573
2016	83,254
Prior to 2016	45,875
Revolving Loans	4,065
Revolving Loans converted to term loans	0
Total loans, net of unearned income	312,102
Commercial real estate | PD Grade 14 15 16 | CRE | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	676
2019	2,481
2018	22,018
2017	41,211
2016	8,180
Prior to 2016	31,746
Revolving Loans	7,329
Revolving Loans converted to term loans	0
Total loans, net of unearned income	$ 113,641