Business Segments - Selected Business Segment Financial Information (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Business segment financial information
Net Interest Income (Loss)	$ 114,846		$ 124,348		$ 228,784	$ 260,303
Provision for Credit Losses	2,400		2,500		4,400	4,500
Net Interest Income (Loss) After Provision for Credit Losses	112,446		121,848		224,384	255,803
Noninterest Income	42,087		43,255		84,372	83,992
Noninterest Expense	(109,226)		(104,036)		(215,085)	(215,955)
Income (Loss) Before Provision for Income Taxes	45,307		61,067		93,671	123,840
Provision for Income Taxes	(11,224)		(15,006)		(23,197)	(30,937)
Net Income (Loss)	34,083	$ 36,391	46,061	$ 46,842	70,474	92,903
Total Assets	23,300,768		24,947,936		23,300,768	24,947,936	$ 23,733,296
Consumer Banking
Business segment financial information
Net Interest Income (Loss)	98,205		98,114		195,199	194,697
Provision for Credit Losses	2,873		1,392		5,160	4,061
Net Interest Income (Loss) After Provision for Credit Losses	95,332		96,722		190,039	190,636
Noninterest Income	33,653		31,944		65,635	63,098
Noninterest Expense	(87,011)		(81,192)		(169,716)	(166,167)
Income (Loss) Before Provision for Income Taxes	41,974		47,474		85,958	87,567
Provision for Income Taxes	(10,685)		(12,219)		(21,865)	(22,493)
Net Income (Loss)	31,289		35,255		64,093	65,074
Total Assets	8,357,830		8,715,172		8,357,830	8,715,172
Commercial Banking
Business segment financial information
Net Interest Income (Loss)	50,885		52,257		102,378	107,798
Provision for Credit Losses	473		(15)		467	(16)
Net Interest Income (Loss) After Provision for Credit Losses	50,412		52,272		101,911	107,814
Noninterest Income	6,698		7,939		13,492	16,588
Noninterest Expense	(18,010)		(19,302)		(36,653)	(39,591)
Income (Loss) Before Provision for Income Taxes	39,100		40,909		78,750	84,811
Provision for Income Taxes	(9,887)		(10,336)		(19,895)	(20,822)
Net Income (Loss)	29,213		30,573		58,855	63,989
Total Assets	5,835,399		5,714,929		5,835,399	5,714,929
Treasury and Other
Business segment financial information
Net Interest Income (Loss)	(34,244)		(26,023)		(68,793)	(42,192)
Provision for Credit Losses	(946)		1,123		(1,227)	455
Net Interest Income (Loss) After Provision for Credit Losses	(33,298)		(27,146)		(67,566)	(42,647)
Noninterest Income	1,736		3,372		5,245	4,306
Noninterest Expense	(4,205)		(3,542)		(8,716)	(10,197)
Income (Loss) Before Provision for Income Taxes	(35,767)		(27,316)		(71,037)	(48,538)
Provision for Income Taxes	9,348		7,549		18,563	12,378
Net Income (Loss)	(26,419)		(19,767)		(52,474)	(36,160)
Total Assets	$ 9,107,539		$ 10,517,835		$ 9,107,539	$ 10,517,835