Business Segments - Selected Business Segment Financial Information (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Business segment financial information
Net Interest Income	$ 141,655			$ 126,819			$ 399,820	$ 370,902
Provision for Credit Losses				(10,400)			(8,000)	(40,800)
Net Interest Income After Provision for Credit Losses	141,655			137,219			407,820	411,702
Noninterest Income	30,660			41,378			116,369	128,779
Noninterest Expense	(105,749)			(96,519)			(312,562)	(291,911)
Income (Loss) Before Provision for Income Taxes	66,566			82,078			211,627	248,570
Provision for Income Taxes	(13,765)			(20,025)			(47,130)	(59,035)
Net Income	52,801	$ 56,862	$ 54,834	62,053	$ 67,533	$ 59,949	164,497	189,535
Total Assets	23,134,040			22,965,383			23,134,040	22,965,383	$ 22,784,941
Consumer Banking
Business segment financial information
Net Interest Income	85,666			72,062			232,654	212,991
Provision for Credit Losses	1,148			1,235			3,463	5,088
Net Interest Income After Provision for Credit Losses	84,518			70,827			229,191	207,903
Noninterest Income	30,974			32,046			94,811	98,344
Noninterest Expense	(83,278)			(71,377)			(247,724)	(222,426)
Income (Loss) Before Provision for Income Taxes	32,214			31,496			76,278	83,821
Provision for Income Taxes	(8,104)			(8,001)			(19,151)	(20,840)
Net Income	24,110			23,495			57,127	62,981
Total Assets	8,399,068			7,530,513			8,399,068	7,530,513
Commercial Banking
Business segment financial information
Net Interest Income	56,249			50,088			152,391	146,269
Provision for Credit Losses	(1)			(42)			(200)	205
Net Interest Income After Provision for Credit Losses	56,250			50,130			152,591	146,064
Noninterest Income	(911)			7,906			17,650	22,339
Noninterest Expense	(17,073)			(15,924)			(52,757)	(47,343)
Income (Loss) Before Provision for Income Taxes	38,266			42,112			117,484	121,060
Provision for Income Taxes	(9,273)			(10,373)			(28,721)	(29,634)
Net Income	28,993			31,739			88,763	91,426
Total Assets	5,486,330			5,087,831			5,486,330	5,087,831
Treasury and Other
Business segment financial information
Net Interest Income	(260)			4,669			14,775	11,642
Provision for Credit Losses	(1,147)			(11,593)			(11,263)	(46,093)
Net Interest Income After Provision for Credit Losses	887			16,262			26,038	57,735
Noninterest Income	597			1,426			3,908	8,096
Noninterest Expense	(5,398)			(9,218)			(12,081)	(22,142)
Income (Loss) Before Provision for Income Taxes	(3,914)			8,470			17,865	43,689
Provision for Income Taxes	3,612			(1,651)			742	(8,561)
Net Income	(302)			6,819			18,607	35,128
Total Assets	$ 9,248,642			$ 10,347,039			$ 9,248,642	$ 10,347,039