Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2020		Jun. 30, 2019	Jun. 30, 2020		Jun. 30, 2019	Dec. 31, 2019
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	$ 444,490		$ 184,911	$ 200,307		$ 180,424
Charge-offs	(22,907)		(12,223)	(36,360)		(22,750)
Recoveries	6,298		7,061	12,540		13,075
Provision/(provision credit) for loan losses	110,000		13,000	255,000		22,000
Ending Balance	537,881		192,749	537,881		192,749
Allowance - individually evaluated for impairment	30,204		31,181	30,204		31,181
Allowance - collectively evaluated for impairment	507,677		159,579	507,677		159,579
Individually evaluated for impairment	289,917		300,726	289,917		300,726
Collectively evaluated for impairment	32,419,020		29,343,285	32,419,020		29,343,285
Loans, net of unearned income	32,708,937	[1]	29,712,810	32,708,937	[1]	29,712,810	$ 31,061,111	[1]
Commercial
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance				158,598
Allowance - individually evaluated for impairment							6,196
Allowance - collectively evaluated for impairment							151,554
Individually evaluated for impairment							84,001
Collectively evaluated for impairment							24,273,207
Commercial | C&I
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	254,516		103,713	122,486		98,947
Charge-offs	(18,201)		(6,590)	(24,952)		(9,691)
Recoveries	1,073		519	2,008		1,348
Provision/(provision credit) for loan losses	81,334		18,454	200,398		25,492
Ending Balance	318,722		116,096	318,722		116,096
Allowance - individually evaluated for impairment	16,577		8,484	16,577		8,484
Allowance - collectively evaluated for impairment	302,145		106,758	302,145		106,758
Individually evaluated for impairment	140,526		115,808	140,526		115,808
Collectively evaluated for impairment	21,253,367		18,904,621	21,253,367		18,904,621
Loans, net of unearned income	21,393,893		19,054,269	21,393,893		19,054,269	20,051,091
Commercial | Commercial Real Estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	47,625		34,382	36,112		31,311
Charge-offs	(61)		(121)	(642)		(555)
Recoveries	156		(88)	729		(31)
Provision/(provision credit) for loan losses	9,565		(1,220)	28,434		2,228
Ending Balance	57,285		32,953	57,285		32,953
Allowance - individually evaluated for impairment	0		0	0		0
Allowance - collectively evaluated for impairment	57,285		32,953	57,285		32,953
Individually evaluated for impairment	160		1,777	160		1,777
Collectively evaluated for impairment	4,813,181		3,852,027	4,813,181		3,852,027
Loans, net of unearned income	4,813,341		3,861,031	4,813,341		3,861,031	4,337,017
Consumer | Consumer Real Estate (a)
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	123,022		34,154	28,443		37,439
Charge-offs	(1,968)		(1,714)	(4,278)		(4,518)
Recoveries	3,987		5,525	7,542		9,566
Provision/(provision credit) for loan losses	18,716		(6,433)	19,058		(10,955)
Ending Balance	143,757		31,532	143,757		31,532
Allowance - individually evaluated for impairment	13,275		22,255	13,275		22,255
Allowance - collectively evaluated for impairment	130,482		8,199	130,482		8,199
Individually evaluated for impairment	148,543		182,442	148,543		182,442
Collectively evaluated for impairment	5,903,850		6,093,863	5,903,850		6,093,863
Loans, net of unearned income	6,052,393		6,303,134	6,052,393		6,303,134	6,177,139
Consumer | Credit Card and Other
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	19,327		12,662	13,266		12,727
Charge-offs	(2,677)		(3,798)	(6,488)		(7,986)
Recoveries	1,082		1,105	2,261		2,192
Provision/(provision credit) for loan losses	385		2,199	7,110		5,235
Ending Balance	18,117		12,168	18,117		12,168
Allowance - individually evaluated for impairment	352		442	352		442
Allowance - collectively evaluated for impairment	17,765		11,669	17,765		11,669
Individually evaluated for impairment	688		699	688		699
Collectively evaluated for impairment	448,622		492,774	448,622		492,774
Loans, net of unearned income	$ 449,310		494,376	449,310		494,376	$ 495,864
Cumulative Effect, Period Of Adoption, Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance				106,394
Cumulative Effect, Period Of Adoption, Adjustment | Commercial | C&I
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance				18,782
Cumulative Effect, Period Of Adoption, Adjustment | Commercial | Commercial Real Estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance				(7,348)
Cumulative Effect, Period Of Adoption, Adjustment | Consumer | Consumer Real Estate (a)
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance				92,992
Cumulative Effect, Period Of Adoption, Adjustment | Consumer | Credit Card and Other
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance				$ 1,968
Purchased credit-impaired loans
Allowance for Loan and Lease Losses [Roll Forward]
Ending Balance			1,989			1,989
Loans, net of unearned income			68,799			68,799
Purchased credit-impaired loans | Commercial | C&I
Allowance for Loan and Lease Losses [Roll Forward]
Ending Balance			854			854
Loans, net of unearned income			33,840			33,840
Purchased credit-impaired loans | Commercial | Commercial Real Estate
Allowance for Loan and Lease Losses [Roll Forward]
Ending Balance			0			0
Loans, net of unearned income			7,227			7,227
Purchased credit-impaired loans | Consumer | Consumer Real Estate (a)
Allowance for Loan and Lease Losses [Roll Forward]
Ending Balance			1,078			1,078
Loans, net of unearned income			26,829			26,829
Purchased credit-impaired loans | Consumer | Credit Card and Other
Allowance for Loan and Lease Losses [Roll Forward]
Ending Balance			57			57
Loans, net of unearned income			$ 903			$ 903

[1] June 30, 2020 and December 31, 2019 include $16.9 million and $18.8 million, respectively, of held-to-maturity consumer mortgage loans secured by residential real estate in process of foreclosure.