Segment Reporting (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2022	Mar. 31, 2022	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2022	Jun. 30, 2021
Segment Income Statement Data Abstract
Net interest income	$ 216,146		$ 179,515		$ 403,893	$ 355,416
Net intersegment interest income (expense)	0		0		0	0
Segment net interest income	216,146		179,515		403,893	355,416
Noninterest income(a)	75,458		73,443		149,925	168,786
Total revenue	291,604		252,957		553,819	524,202
Provision for credit losses	(2)		(35,004)		(3,992)	(58,009)
Noninterest expense	181,420		174,475		354,712	349,821
Income before income taxes	110,187		113,487		203,099	232,389
Income tax expense (benefit)	23,363		22,480		42,013	47,082
Net income	86,824	$ 74,262	91,007	$ 94,301	161,086	185,307
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	111,359		90,039		201,992	179,700
Net intersegment interest income (expense)	(5,301)		4,324		3,224	8,994
Segment net interest income	106,058		94,363		205,216	188,694
Noninterest income(a)	39,133		37,281		76,923	79,109
Total revenue	145,191		131,643		282,139	267,803
Provision for credit losses	12,246		15,716		24,900	32,395
Noninterest expense	56,847		53,902		113,406	109,349
Income before income taxes	76,098		62,026		143,833	126,058
Income tax expense (benefit)	13,919		11,214		26,232	23,106
Net income	62,179		50,812		117,601	102,953
Segment Balance Sheet Data
Allocated goodwill					525,836	525,836
Operating Segments | Community, Consumer, and Business
Segment Income Statement Data Abstract
Net interest income	76,999		73,477		146,543	145,253
Net intersegment interest income (expense)	30,638		15,992		49,470	30,881
Segment net interest income	107,636		89,470		196,013	176,134
Noninterest income(a)	32,121		32,967		65,327	80,298
Total revenue	139,757		122,437		261,341	256,432
Provision for credit losses	4,924		5,279		9,580	11,207
Noninterest expense	105,139		101,735		203,802	202,086
Income before income taxes	29,695		15,424		47,959	43,139
Income tax expense (benefit)	6,236		3,239		10,071	9,059
Net income	23,459		12,185		37,888	34,080
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	27,789		15,999		55,358	30,464
Net intersegment interest income (expense)	(25,337)		(20,316)		(52,694)	(39,875)
Segment net interest income	2,452		(4,318)		2,664	(9,412)
Noninterest income(a)	4,204		3,195		7,675	9,379
Total revenue	6,656		(1,123)		10,339	(33)
Provision for credit losses	(17,172)		(55,999)		(38,472)	(101,610)
Noninterest expense	19,434		18,839		37,505	38,386
Income before income taxes	4,394		36,037		11,307	63,191
Income tax expense (benefit)	3,209		8,027		5,710	14,917
Net income	$ 1,186		$ 28,010		5,597	48,274
Segment Balance Sheet Data
Allocated goodwill					$ 0	$ 0