Reportable Operating Segments - Selected Business Segment Financial Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Selected business segment financial information
Net interest income (expense)	$ 636,127	$ 613,549	$ 530,559
Benefit (provision) for credit losses	(26,630)	(1,392)	39,000
Net interest income after provision for credit losses	609,497	612,157	569,559
Noninterest income	200,815	179,525	184,916
Noninterest expense	(501,138)	(440,471)	(405,479)
Income before provision for income taxes	309,174	351,211	348,996
(Provision) benefit for income taxes	(74,191)	(85,526)	(83,261)
Net income	234,983	265,685	265,735
Total assets	24,926,474	24,577,223	24,992,410
Retail Banking
Selected business segment financial information
Net interest income (expense)	458,125	436,228	385,656
Benefit (provision) for credit losses	(9,899)	967	16,267
Net interest income after provision for credit losses	448,226	437,195	401,923
Noninterest income	97,651	94,085	91,672
Noninterest expense	(304,731)	(293,563)	(247,949)
Income before provision for income taxes	241,146	237,717	245,646
(Provision) benefit for income taxes	(58,091)	(58,077)	(58,710)
Net income	183,055	179,640	186,936
Total assets	7,589,607	7,463,002	7,148,376
Commercial Banking
Selected business segment financial information
Net interest income (expense)	175,569	157,128	162,997
Benefit (provision) for credit losses	(14,961)	1,154	22,452
Net interest income after provision for credit losses	160,608	158,282	185,449
Noninterest income	75,358	77,539	72,781
Noninterest expense	(112,839)	(109,906)	(100,932)
Income before provision for income taxes	123,127	125,915	157,298
(Provision) benefit for income taxes	(27,927)	(30,158)	(37,525)
Net income	95,200	95,757	119,773
Total assets	6,966,731	6,850,638	5,972,567
Treasury and Other
Selected business segment financial information
Net interest income (expense)	2,433	20,193	(18,094)
Benefit (provision) for credit losses	(1,770)	(3,513)	281
Net interest income after provision for credit losses	663	16,680	(17,813)
Noninterest income	27,806	7,901	20,463
Noninterest expense	(83,568)	(37,002)	(56,598)
Income before provision for income taxes	(55,099)	(12,421)	(53,948)
(Provision) benefit for income taxes	11,827	2,709	12,974
Net income	(43,272)	(9,712)	(40,974)
Total assets	$ 10,370,136	$ 10,263,583	$ 11,871,467