Business Segments - Selected Business Segment Financial Information (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	Dec. 31, 2022
Business segment financial information
Net Interest Income	$ 124,348		$ 132,902		$ 260,303	$ 258,165
Provision for Credit Losses	2,500		(2,500)		4,500	(8,000)
Net Interest Income (Loss) After Provision for Credit Losses	121,848		135,402		255,803	266,165
Noninterest Income	43,255		42,158		83,992	85,709
Noninterest Expense	(104,036)		(102,939)		(215,955)	(206,813)
Income (Loss) Before Provision for Income Taxes	61,067		74,621		123,840	145,061
Provision for Income Taxes	(15,006)		(17,759)		(30,937)	(33,365)
Net Income (Loss)	46,061	$ 46,842	56,862	$ 54,834	92,903	111,696
Total Assets	24,947,936		23,232,699		24,947,936	23,232,699	$ 23,606,877
Consumer Banking
Business segment financial information
Net Interest Income	99,814		76,872		197,822	147,233
Provision for Credit Losses	1,392		632		4,061	2,315
Net Interest Income (Loss) After Provision for Credit Losses	98,422		76,240		193,761	144,918
Noninterest Income	31,944		31,868		63,098	63,837
Noninterest Expense	(81,275)		(82,856)		(166,348)	(164,666)
Income (Loss) Before Provision for Income Taxes	49,091		25,252		90,511	44,089
Provision for Income Taxes	(12,645)		(6,339)		(23,268)	(11,053)
Net Income (Loss)	36,446		18,913		67,243	33,036
Total Assets	8,739,294		8,205,352		8,739,294	8,205,352
Commercial Banking
Business segment financial information
Net Interest Income	53,673		49,791		110,378	96,140
Provision for Credit Losses	(15)		(1)		(16)	(198)
Net Interest Income (Loss) After Provision for Credit Losses	53,688		49,792		110,394	96,338
Noninterest Income	7,939		8,363		16,588	18,561
Noninterest Expense	(19,302)		(17,014)		(39,591)	(35,683)
Income (Loss) Before Provision for Income Taxes	42,325		41,141		87,391	79,216
Provision for Income Taxes	(10,710)		(10,252)		(21,503)	(19,449)
Net Income (Loss)	31,615		30,889		65,888	59,767
Total Assets	5,714,929		5,339,224		5,714,929	5,339,224
Treasury and Other
Business segment financial information
Net Interest Income	(29,139)		6,239		(47,897)	14,792
Provision for Credit Losses	1,123		(3,131)		455	(10,117)
Net Interest Income (Loss) After Provision for Credit Losses	(30,262)		9,370		(48,352)	24,909
Noninterest Income	3,372		1,927		4,306	3,311
Noninterest Expense	(3,459)		(3,069)		(10,016)	(6,464)
Income (Loss) Before Provision for Income Taxes	(30,349)		8,228		(54,062)	21,756
Provision for Income Taxes	8,349		(1,168)		13,834	(2,863)
Net Income (Loss)	(22,000)		7,060		(40,228)	18,893
Total Assets	$ 10,493,713		$ 9,688,123		$ 10,493,713	$ 9,688,123