Allowance for Credit Losses (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	$ 537,881	$ 192,749	$ 200,307	$ 180,424
Charge-offs	78,341	24,337	114,701	47,087
Recoveries	11,751	9,737	24,291	22,812
Provision for credit losses	227,000	14,366	502,388	36,273
Ending Balance	988,102	193,149	988,102	193,149
Loans, net of unearned income	59,706,531		59,706,531		$ 31,061,111
Funded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Provision for credit losses	230,000	15,000	485,000	37,000
Unfunded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	50,461	7,525	6,101	7,618
Initial reserve on loans acquired	41,259		41,259
Provision for credit losses	(3,000)	(635)	17,388	(728)
Ending Balance	88,720	6,890	88,720	6,890
Commercial
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance			158,598
Loans, net of unearned income	33,655,717		33,655,717		20,051,091
Commercial | Commercial, Financial, and Industrial (a)
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	318,722	116,096	122,486	98,947
Charge-offs	69,448	18,598	94,400	28,289
Recoveries	3,200	3,245	5,208	4,593
Ending Balance	489,094	114,130	489,094	114,130
Loans, net of unearned income	28,048,649		28,048,649		15,640,208
Commercial | Commercial, Financial, and Industrial (a) | PCD Loans
Allowance for Loan and Lease Losses [Roll Forward]
Charge-offs			237,300
Commercial | Commercial, Financial, and Industrial (a) | Non-PCD Loans
Allowance for Loan and Lease Losses [Roll Forward]
Provision for credit losses	147,000		147,000
Commercial | Commercial, Financial, and Industrial (a) | Paycheck Protection Plan
Allowance for Loan and Lease Losses [Roll Forward]
Loans, net of unearned income	4,200,000		4,200,000
Commercial | Commercial, Financial, and Industrial (a) | Funded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Provision for credit losses	98,918	13,387	299,316	38,879
Commercial | Commercial, Financial, and Industrial (a) | Unfunded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	36,388	4,231	3,590	4,240
Initial reserve on loans acquired	11,760		11,760
Provision for credit losses	(1,509)	(406)	14,777	(415)
Ending Balance	46,639	3,825	46,639	3,825
Commercial | Commercial Real Estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	57,285	32,953	36,112	31,311
Charge-offs	3,540	369	4,182	924
Recoveries	2,243	181	2,972	150
Ending Balance	207,958	35,625	207,958	35,625
Loans, net of unearned income	12,510,887		12,510,887		4,337,017
Commercial | Commercial Real Estate | Funded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Provision for credit losses	51,847	2,860	80,281	5,088
Commercial | Commercial Real Estate | Unfunded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	6,359	3,149	2,356	3,242
Initial reserve on loans acquired	26,306		26,306
Provision for credit losses	(1,671)	(231)	1,056	(324)
Ending Balance	30,994	2,918	30,994	2,918
Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Loans, net of unearned income	12,327,869		12,327,869		6,177,139
Consumer | Consumer Real Estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	143,757	31,532	28,443	37,439
Charge-offs	1,834	1,473	6,112	5,991
Recoveries	5,311	5,055	12,853	14,621
Ending Balance	265,430	30,674	265,430	30,674
Loans, net of unearned income	12,327,869		12,327,869		6,177,139
Consumer | Consumer Real Estate | Funded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Provision for credit losses	74,055	(4,440)	93,113	(15,395)
Consumer | Consumer Real Estate | Unfunded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	7,714	20	16	27
Initial reserve on loans acquired	3,185		3,185
Provision for credit losses	180	(5)	1,555	(12)
Ending Balance	11,079	15	11,079	15
Consumer | Credit Card and Other
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	18,117	12,168	13,266	12,727
Charge-offs	3,519	3,897	10,007	11,883
Recoveries	997	1,256	3,258	3,448
Ending Balance	25,620	12,720	25,620	12,720
Loans, net of unearned income	1,212,058		1,212,058		$ 495,864
Consumer | Credit Card and Other | Funded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Provision for credit losses	5,180	3,193	12,290	8,428
Consumer | Credit Card and Other | Unfunded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	0	125	139	109
Initial reserve on loans acquired	8		8
Provision for credit losses	0	7	0	23
Ending Balance	8	$ 132	8	$ 132
Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance			106,394
Adjustment | Unfunded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance			23,972
Adjustment | Commercial | Commercial, Financial, and Industrial (a)
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance			18,782
Adjustment | Commercial | Commercial, Financial, and Industrial (a) | Unfunded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance			16,512
Adjustment | Commercial | Commercial Real Estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance			(7,348)
Adjustment | Commercial | Commercial Real Estate | Unfunded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance			1,276
Adjustment | Consumer | Consumer Real Estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance			92,992
Adjustment | Consumer | Consumer Real Estate | Unfunded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance			6,323
Adjustment | Consumer | Credit Card and Other
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance			1,968
Adjustment | Consumer | Credit Card and Other | Unfunded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance			(139)
Adjusted balance
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance			306,701
Adjusted balance | Unfunded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance			30,073
Adjusted balance | Commercial | Commercial, Financial, and Industrial (a)
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance			141,268
Adjusted balance | Commercial | Commercial, Financial, and Industrial (a) | Unfunded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance			20,102
Adjusted balance | Commercial | Commercial Real Estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance			28,764
Adjusted balance | Commercial | Commercial Real Estate | Unfunded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance			3,632
Adjusted balance | Consumer | Consumer Real Estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance			121,435
Adjusted balance | Consumer | Consumer Real Estate | Unfunded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance			6,339
Adjusted balance | Consumer | Credit Card and Other
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance			15,234
Adjusted balance | Consumer | Credit Card and Other | Unfunded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance			0
Financial Asset Acquired with Credit Deterioration
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	286,811		286,811
Financial Asset Acquired with Credit Deterioration | Commercial | Commercial, Financial, and Industrial (a)
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	137,702		137,702
Financial Asset Acquired with Credit Deterioration | Commercial | Commercial Real Estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	100,123		100,123
Financial Asset Acquired with Credit Deterioration | Consumer | Consumer Real Estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	44,141		44,141
Financial Asset Acquired with Credit Deterioration | Consumer | Credit Card and Other
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	$ 4,845		$ 4,845