Segment Reporting (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2023	Sep. 30, 2022
Segment Income Statement Data Abstract
Net interest income	$ 254,244			$ 264,439			$ 786,171	$ 668,332
Net intersegment interest (expense)	0			0			0	0
Segment net interest income	254,244			264,439			786,171	668,332
Noninterest income	66,579			70,788			194,195	220,713
Total revenue	320,823			335,227			980,366	889,045
Provision for credit losses	21,943			16,998			62,014	13,006
Noninterest expense	196,205			195,791			574,291	550,503
Income before income taxes	102,674			122,438			344,061	325,536
Income tax expense (benefit)	19,426			26,163			70,299	68,176
Net income	83,248	$ 87,154	$ 103,360	96,275	$ 86,824	$ 74,262	273,762	257,360
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	250,365			161,143			710,031	363,135
Net intersegment interest (expense)	(106,675)			(40,117)			(288,366)	(36,893)
Segment net interest income	143,690			121,026			421,665	326,242
Noninterest income	34,081			35,663			99,243	112,620
Total revenue	177,771			156,688			520,908	438,862
Provision for credit losses	14,066			11,904			41,523	36,803
Noninterest expense	63,207			58,934			186,351	172,141
Income before income taxes	100,498			85,851			293,034	229,918
Income tax expense (benefit)	19,304			15,967			54,138	42,248
Net income	81,194			69,884			238,897	187,670
Segment Balance Sheet Data
Allocated goodwill							525,836	525,836
Operating Segments | Community, Consumer, and Business
Segment Income Statement Data Abstract
Net interest income	67,139			87,156			219,883	233,699
Net intersegment interest (expense)	123,900			49,437			317,820	98,907
Segment net interest income	191,039			136,593			537,703	332,606
Noninterest income	29,675			26,745			85,881	92,072
Total revenue	220,714			163,338			623,584	424,679
Provision for credit losses	7,381			5,378			21,467	14,958
Noninterest expense	108,185			107,860			328,960	311,423
Income before income taxes	105,148			50,100			273,158	98,298
Income tax expense (benefit)	22,187			10,521			57,469	20,642
Net income	82,961			39,579			215,688	77,655
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	(63,260)			16,140			(143,743)	71,498
Net intersegment interest (expense)	(17,225)			(9,320)			(29,454)	(62,014)
Segment net interest income	(80,485)			6,820			(173,197)	9,484
Noninterest income	2,823			8,381			9,071	16,021
Total revenue	(77,663)			15,201			(164,126)	25,505
Provision for credit losses	496			(283)			(975)	(38,756)
Noninterest expense	24,814			28,997			58,980	66,940
Income before income taxes	(102,972)			(13,513)			(222,131)	(2,679)
Income tax expense (benefit)	(22,065)			(325)			(41,308)	5,286
Net income	$ (80,907)			$ (13,189)			(180,823)	(7,965)
Segment Balance Sheet Data
Allocated goodwill							$ 0	$ 0