Segment Reporting (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2024	Jun. 30, 2023
Segment Income Statement Data Abstract
Net interest income	$ 256,593		$ 257,917		$ 514,451	$ 531,927
Net intersegment interest (expense)	0		0		0	0
Segment net interest income	256,593		257,917		514,451	531,927
Noninterest income	65,159		65,543		130,144	127,616
Total revenue	321,752		323,460		644,595	659,543
Provision for credit losses	23,008		22,100		47,009	40,071
Noninterest expense	195,861		190,673		393,518	378,086
Income before income taxes	102,884		110,687		204,068	241,386
Income tax expense (benefit)	(12,689)		23,533		7,326	50,873
Net income	115,573	$ 81,169	87,154	$ 103,360	196,742	190,514
Allocated goodwill	1,104,992		1,104,992		1,104,992	1,104,992
Operating Segments | Corporate and Commercial Specialty
Segment Income Statement Data Abstract
Net interest income	251,196		240,542		494,127	459,665
Net intersegment interest (expense)	(99,238)		(100,711)		(192,974)	(181,691)
Segment net interest income	151,958		139,832		301,153	277,975
Noninterest income	35,131		32,451		69,553	65,168
Total revenue	187,089		172,282		370,707	343,143
Provision for credit losses	16,492		13,674		31,920	27,456
Noninterest expense	65,394		61,137		131,744	123,256
Income before income taxes	105,204		97,471		207,042	192,431
Income tax expense (benefit)	17,765		17,086		38,846	34,811
Net income	87,438		80,385		168,196	157,619
Allocated goodwill	525,836		525,836		525,836	525,836
Operating Segments | Community, Consumer, and Business
Segment Income Statement Data Abstract
Net interest income	57,808		72,460		116,000	152,744
Net intersegment interest (expense)	135,332		105,841		265,491	193,920
Segment net interest income	193,140		178,301		381,491	346,664
Noninterest income	25,418		30,252		49,912	56,199
Total revenue	218,559		208,554		431,404	402,863
Provision for credit losses	5,591		7,328		12,416	14,086
Noninterest expense	107,565		108,928		218,055	220,663
Income before income taxes	105,403		92,298		200,933	168,114
Income tax expense (benefit)	22,134		19,383		42,196	35,304
Net income	83,268		72,915		158,737	132,810
Allocated goodwill	579,156		579,156		579,156	579,156
Operating Segments | Risk Management and Shared Services
Segment Income Statement Data Abstract
Net interest income	(52,411)		(55,085)		(95,677)	(80,483)
Net intersegment interest (expense)	(36,095)		(5,130)		(72,517)	(12,229)
Segment net interest income	(88,506)		(60,216)		(168,194)	(92,712)
Noninterest income	4,610		2,840		10,678	6,249
Total revenue	(83,896)		(57,376)		(157,515)	(86,463)
Provision for credit losses	925		1,097		2,672	(1,471)
Noninterest expense	22,902		20,609		43,719	34,167
Income before income taxes	(107,722)		(79,082)		(203,906)	(119,159)
Income tax expense (benefit)	(52,589)		(12,935)		(73,716)	(19,243)
Net income	(55,133)		(66,146)		(130,191)	(99,916)
Allocated goodwill	$ 0		$ 0		$ 0	$ 0