Business Segments - Selected Business Segment Financial Information (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	Dec. 31, 2021
Business segment financial information
Net Interest Income	$ 132,902		$ 123,514		$ 258,165	$ 244,083
Provision for Credit Losses	(2,500)		(16,100)		(8,000)	(30,400)
Net Interest Income After Provision for Credit Losses	135,402		139,614		266,165	274,483
Noninterest Income	42,158		44,431		85,709	87,401
Noninterest Expense	(102,939)		(96,527)		(206,813)	(195,392)
Income Before Provision for Income Taxes	74,621		87,518		145,061	166,492
Provision for Income Taxes	(17,759)		(19,985)		(33,365)	(39,010)
Net Income	56,862	$ 54,834	67,533	$ 59,949	111,696	127,482
Total Assets	23,232,699		22,672,183		23,232,699	22,672,183	$ 22,784,941
Consumer Banking
Business segment financial information
Net Interest Income	75,868		71,167		146,103	140,929
Provision for Credit Losses	502		987		2,185	3,853
Net Interest Income After Provision for Credit Losses	75,366		70,180		143,918	137,076
Noninterest Income	31,953		32,600		63,922	66,298
Noninterest Expense	(82,740)		(72,868)		(164,438)	(151,049)
Income Before Provision for Income Taxes	24,579		29,912		43,402	52,325
Provision for Income Taxes	(6,162)		(7,365)		(10,872)	(12,839)
Net Income	18,417		22,547		32,530	39,486
Total Assets	8,179,647		7,479,986		8,179,647	7,479,986
Commercial Banking
Business segment financial information
Net Interest Income	49,562		49,038		95,911	96,181
Provision for Credit Losses	(1)		197		(198)	247
Net Interest Income After Provision for Credit Losses	49,563		48,841		96,109	95,934
Noninterest Income	8,279		6,575		18,477	14,433
Noninterest Expense	(17,026)		(15,742)		(35,695)	(31,419)
Income Before Provision for Income Taxes	40,816		39,674		78,891	78,948
Provision for Income Taxes	(10,145)		(9,703)		(19,342)	(19,261)
Net Income	30,671		29,971		59,549	59,687
Total Assets	5,337,656		5,127,431		5,337,656	5,127,431
Treasury and Other
Business segment financial information
Net Interest Income	7,472		3,309		16,151	6,973
Provision for Credit Losses	(3,001)		(17,284)		(9,987)	(34,500)
Net Interest Income After Provision for Credit Losses	10,473		20,593		26,138	41,473
Noninterest Income	1,926		5,256		3,310	6,670
Noninterest Expense	(3,173)		(7,917)		(6,680)	(12,924)
Income Before Provision for Income Taxes	9,226		17,932		22,768	35,219
Provision for Income Taxes	(1,452)		(2,917)		(3,151)	(6,910)
Net Income	7,774		15,015		19,617	28,309
Total Assets	$ 9,715,396		$ 10,064,766		$ 9,715,396	$ 10,064,766