Segment Reporting (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2022	Sep. 30, 2021
Segment Income Statement Data Abstract
Net interest income	$ 264,439			$ 183,675			$ 668,332	$ 539,092
Net intersegment interest income (expense)	0			0			0	0
Segment net interest income	264,439			183,675			668,332	539,092
Noninterest income(a)	70,788			82,076			220,713	250,862
Total revenue	335,227			265,752			889,045	789,954
Provision for credit losses	16,998			(24,010)			13,006	(82,018)
Noninterest expense	195,791			177,892			550,503	527,713
Income before income taxes	122,438			111,870			325,536	344,259
Income tax expense (benefit)	26,163			23,060			68,176	70,142
Net income	96,275	$ 86,824	$ 74,262	88,809	$ 91,007	$ 94,301	257,360	274,117
Segment Balance Sheet Data
Allocated goodwill							1,104,992	1,104,992
Operating Segments | Corporate and Commercial Specialty
Segment Income Statement Data Abstract
Net interest income	161,143			91,012			363,135	270,712
Net intersegment interest income (expense)	(37,998)			3,696			(34,774)	12,690
Segment net interest income	123,145			94,709			328,361	283,403
Noninterest income(a)	35,663			41,892			112,620	120,991
Total revenue	158,808			136,601			440,981	404,394
Provision for credit losses	11,904			14,349			36,803	46,745
Noninterest expense	58,934			56,209			172,141	165,568
Income before income taxes	87,970			66,043			232,037	192,082
Income tax expense (benefit)	16,420			11,920			42,692	35,021
Net income	71,551			54,123			189,346	157,060
Segment Balance Sheet Data
Allocated goodwill							525,836	525,836
Operating Segments | Community, Consumer, and Business
Segment Income Statement Data Abstract
Net interest income	87,156			73,616			233,699	218,868
Net intersegment interest income (expense)	49,575			15,283			99,046	46,165
Segment net interest income	136,731			88,899			332,745	265,033
Noninterest income(a)	26,745			37,053			92,072	117,351
Total revenue	163,476			125,952			424,817	382,384
Provision for credit losses	5,378			4,748			14,958	15,955
Noninterest expense	107,782			98,172			311,210	300,913
Income before income taxes	50,316			23,032			98,649	65,517
Income tax expense (benefit)	10,567			4,837			20,716	13,758
Net income	39,749			18,196			77,933	51,758
Segment Balance Sheet Data
Allocated goodwill							579,156	579,156
Operating Segments | Risk Management and Shared Services
Segment Income Statement Data Abstract
Net interest income	16,140			19,047			71,498	49,511
Net intersegment interest income (expense)	(11,577)			(18,980)			(64,272)	(58,855)
Segment net interest income	4,563			68			7,227	(9,344)
Noninterest income(a)	8,381			3,131			16,021	12,520
Total revenue	12,943			3,199			23,247	3,176
Provision for credit losses	(283)			(43,107)			(38,756)	(144,717)
Noninterest expense	29,076			23,512			67,153	61,233
Income before income taxes	(15,849)			22,794			(5,150)	86,660
Income tax expense (benefit)	(824)			6,304			4,769	21,363
Net income	$ (15,025)			$ 16,490			(9,918)	65,298
Segment Balance Sheet Data
Allocated goodwill							$ 0	$ 0