Segment Reporting (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2022	Mar. 31, 2022	Jun. 30, 2023	Jun. 30, 2022
Segment Income Statement Data Abstract
Net interest income	$ 257,917		$ 216,146		$ 531,927	$ 403,893
Net intersegment interest income (expense)	0		0		0	0
Segment net interest income	257,917		216,146		531,927	403,893
Noninterest income	65,543		75,458		127,616	149,925
Total revenue	323,460		291,604		659,543	553,819
Provision for credit losses	22,100		(2)		40,071	(3,992)
Noninterest expense	190,673		181,420		378,086	354,712
Income before income taxes	110,687		110,187		241,386	203,099
Income tax expense (benefit)	23,533		23,363		50,873	42,013
Net income	87,154	$ 103,360	86,824	$ 74,262	190,514	161,086
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	240,542		111,359		459,665	201,992
Net intersegment interest income (expense)	(100,711)		(5,301)		(181,691)	3,224
Segment net interest income	139,831		106,058		277,975	205,216
Noninterest income	32,447		39,229		65,162	76,958
Total revenue	172,278		145,287		343,136	282,174
Provision for credit losses	13,674		12,246		27,456	24,900
Noninterest expense	61,083		56,679		123,144	113,207
Income before income taxes	97,521		76,361		192,536	144,067
Income tax expense (benefit)	17,096		13,974		34,833	26,281
Net income	80,425		62,387		157,703	117,786
Segment Balance Sheet Data
Allocated goodwill					525,836	525,836
Operating Segments | Community, Consumer, and Business
Segment Income Statement Data Abstract
Net interest income	72,460		76,999		152,744	146,543
Net intersegment interest income (expense)	105,841		30,638		193,920	49,470
Segment net interest income	178,301		107,636		346,664	196,013
Noninterest income	30,256		32,121		56,206	65,327
Total revenue	208,558		139,757		402,870	261,341
Provision for credit losses	7,328		4,924		14,086	9,580
Noninterest expense	109,028		104,967		220,722	203,428
Income before income taxes	92,201		29,866		168,062	48,332
Income tax expense (benefit)	19,362		6,272		35,293	10,150
Net income	72,839		23,594		132,769	38,183
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	(55,085)		27,789		(80,483)	55,358
Net intersegment interest income (expense)	(5,130)		(25,337)		(12,229)	(52,694)
Segment net interest income	(60,216)		2,452		(92,712)	2,664
Noninterest income	2,840		4,108		6,249	7,640
Total revenue	(57,376)		6,560		(86,463)	10,304
Provision for credit losses	1,097		(17,172)		(1,471)	(38,472)
Noninterest expense	20,562		19,774		34,219	38,077
Income before income taxes	(79,035)		3,959		(119,211)	10,700
Income tax expense (benefit)	(12,926)		3,117		(19,254)	5,583
Net income	$ (66,109)		$ 842		(99,958)	5,117
Segment Balance Sheet Data
Allocated goodwill					$ 0	$ 0