Reportable Operating Segments - Selected Business Segment Financial Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Selected business segment financial information
Total interest income	$ 235,150	$ 244,952
Total interest expense	(74,624)	(90,525)
Net interest income (expense)	160,526	154,427
Provision for credit losses	(10,500)	(6,300)
Net interest income after provision for credit losses	150,026	148,127
Noninterest income	50,477	51,371
Salaries and employee benefits	60,104	59,262
Contracted services and professional fees	14,839	15,739
Occupancy	(8,100)	(6,941)
Equipment	(13,871)	(13,413)
Card rewards program	7,919	8,508
Noninterest expense	(123,560)	(128,813)
Income (loss) before (provision) benefit for income taxes	76,943	70,685
(Provision) benefit for income taxes	(17,695)	(16,465)
Net income	59,248	54,220
Operating Segments
Selected business segment financial information
Total interest income	235,150	244,952
Total interest expense	(74,624)	(90,525)
Net interest income (expense)	160,526	154,427
Provision for credit losses	(10,500)	(6,300)
Net interest income after provision for credit losses	150,026	148,127
Noninterest income	50,477	51,371
Salaries and employee benefits	(60,104)	(59,262)
Contracted services and professional fees	(14,839)	(15,739)
Occupancy	(8,100)	(6,941)
Equipment	(13,871)	(13,413)
Card rewards program	(7,919)	(8,508)
Other segment items	(18,727)	(24,950)
Noninterest expense	(123,560)	(128,813)
Income (loss) before (provision) benefit for income taxes	76,943	70,685
(Provision) benefit for income taxes	(17,695)	(16,465)
Net income	59,248	54,220
Other Segment Disclosures:
Depreciation and amortization	5,528	4,917
Segment earning assets	20,984,647	21,617,600
Retail Banking
Selected business segment financial information
Total interest income	21,402	22,026
Total interest expense	108,480	106,031
Net interest income (expense)	129,882	128,057
Noninterest income	26,651	26,035
Retail Banking | Operating Segments
Selected business segment financial information
Total interest income	84,412	84,223
Total interest expense	(54,881)	(58,372)
Net interest income (expense)	129,882	128,057
Provision for credit losses	(4,691)	(3,379)
Net interest income after provision for credit losses	125,191	124,678
Noninterest income	26,651	26,035
Salaries and employee benefits	(24,612)	(25,238)
Contracted services and professional fees	(3,053)	(2,881)
Occupancy	(7,295)	(7,416)
Equipment	(1,395)	(1,308)
Other segment items	(36,770)	(39,797)
Noninterest expense	(73,125)	(76,640)
Income (loss) before (provision) benefit for income taxes	78,717	74,073
(Provision) benefit for income taxes	(18,774)	(17,928)
Net income	59,943	56,145
Other Segment Disclosures:
Depreciation and amortization	1,048	1,136
Segment earning assets	7,323,191	7,474,076
Retail Banking | Intersegment Eliminations
Selected business segment financial information
Intersegment interest allocations	(63,010)	(62,197)
Intersegment interest allocations	163,361	164,403
Commercial Banking
Selected business segment financial information
Total interest income	30,140	33,536
Total interest expense	12,402	11,845
Net interest income (expense)	42,542	45,381
Noninterest income	17,755	17,958
Commercial Banking | Operating Segments
Selected business segment financial information
Total interest income	107,271	116,775
Total interest expense	(13,934)	(15,313)
Net interest income (expense)	42,542	45,381
Provision for credit losses	(5,309)	(3,713)
Net interest income after provision for credit losses	37,233	41,668
Noninterest income	17,755	17,958
Salaries and employee benefits	(4,791)	(4,996)
Contracted services and professional fees	(3,870)	(4,389)
Occupancy	(495)	(491)
Equipment	(449)	(361)
Card rewards program	(7,919)	(8,508)
Other segment items	(2,247)	(6,940)
Noninterest expense	(19,771)	(25,685)
Income (loss) before (provision) benefit for income taxes	35,217	33,941
(Provision) benefit for income taxes	(6,961)	(7,273)
Net income	28,256	26,668
Other Segment Disclosures:
Depreciation and amortization	68	68
Segment earning assets	6,974,197	6,880,199
Commercial Banking | Intersegment Eliminations
Selected business segment financial information
Intersegment interest allocations	(77,131)	(83,239)
Intersegment interest allocations	26,336	27,158
Treasury and Other
Selected business segment financial information
Total interest income	183,608	189,390
Total interest expense	(195,506)	(208,401)
Net interest income (expense)	(11,898)	(19,011)
Noninterest income	6,071	7,378
Treasury and Other | Operating Segments
Selected business segment financial information
Total interest income	43,467	43,954
Total interest expense	(5,809)	(16,840)
Net interest income (expense)	(11,898)	(19,011)
Provision for credit losses	(500)	792
Net interest income after provision for credit losses	(12,398)	(18,219)
Noninterest income	6,071	7,378
Salaries and employee benefits	(30,701)	(29,028)
Contracted services and professional fees	(7,916)	(8,469)
Occupancy	(310)	966
Equipment	(12,027)	(11,744)
Other segment items	20,290	21,787
Noninterest expense	(30,664)	(26,488)
Income (loss) before (provision) benefit for income taxes	(36,991)	(37,329)
(Provision) benefit for income taxes	8,040	8,736
Net income	(28,951)	(28,593)
Other Segment Disclosures:
Depreciation and amortization	4,412	3,713
Segment earning assets	6,687,259	7,263,325
Treasury and Other | Intersegment Eliminations
Selected business segment financial information
Intersegment interest allocations	140,141	145,436
Intersegment interest allocations	$ (189,697)	$ (191,561)