Business Segments - Selected Business Segment Financial Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Business segment financial information
Net Interest Income	$ 125,263	$ 120,569
Provision for Credit Losses	(5,500)	(14,300)
Net Interest Income After Provision for Credit Losses	130,763	134,869
Noninterest Income	43,551	42,970
Noninterest Expense	(103,874)	(98,865)
Income Before Provision for Income Taxes	70,440	78,974
Provision for Income Taxes	(15,606)	(19,025)
Net Income	54,834	59,949
Total Assets	23,000,317	21,947,271	$ 22,784,941
Consumer Banking
Business segment financial information
Net Interest Income	70,235	69,762
Provision for Credit Losses	1,683	2,866
Net Interest Income After Provision for Credit Losses	68,552	66,896
Noninterest Income	31,969	33,698
Noninterest Expense	(81,698)	(78,181)
Income Before Provision for Income Taxes	18,823	22,413
Provision for Income Taxes	(4,710)	(5,474)
Net Income	14,113	16,939
Total Assets	7,900,273	7,556,756
Commercial Banking
Business segment financial information
Net Interest Income	46,349	47,143
Provision for Credit Losses	(197)	50
Net Interest Income After Provision for Credit Losses	46,546	47,093
Noninterest Income	10,198	7,858
Noninterest Expense	(18,669)	(15,677)
Income Before Provision for Income Taxes	38,075	39,274
Provision for Income Taxes	(9,197)	(9,558)
Net Income	28,878	29,716
Total Assets	5,174,115	5,224,386
Treasury and Other
Business segment financial information
Net Interest Income	8,679	3,664
Provision for Credit Losses	(6,986)	(17,216)
Net Interest Income After Provision for Credit Losses	15,665	20,880
Noninterest Income	1,384	1,414
Noninterest Expense	(3,507)	(5,007)
Income Before Provision for Income Taxes	13,542	17,287
Provision for Income Taxes	(1,699)	(3,993)
Net Income	11,843	13,294
Total Assets	$ 9,925,929	$ 9,166,129