Business Segment Reporting - Schedule of Segment Financial Results (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Segment Reporting Information [Line Items]
Net interest income	$ 245,108	$ 225,611	$ 484,542	$ 467,307
Provision for credit losses	14,050	13,000	24,050	36,250
Noninterest income	144,919	138,082	304,163	268,282
Noninterest expense	249,067	240,673	503,871	477,725
Income before income taxes	126,910	110,020	260,784	221,614
Income tax expense (benefit)	25,565	19,910	49,181	39,067
Net income (loss)	101,345	90,110	211,603	182,547
Average assets	42,476,000	40,365,000	42,246,000	39,443,000
Commercial Banking [Member]
Segment Reporting Information [Line Items]
Net interest income	160,487	144,389	317,734	295,416
Provision for credit losses	11,480	11,055	19,000	32,099
Noninterest income	27,720	25,666	70,686	48,568
Noninterest expense	85,780	85,896	178,199	169,900
Income before income taxes	90,947	73,104	191,221	141,985
Income tax expense (benefit)	17,858	12,996	35,153	24,638
Net income (loss)	73,089	60,108	156,068	117,347
Average assets	21,153,000	20,888,000	21,314,000	20,209,000
Institutional Banking [Member]
Segment Reporting Information [Line Items]
Net interest income	51,502	50,397	101,362	105,482
Provision for credit losses	846	234	1,325	331
Noninterest income	95,092	86,813	187,808	171,051
Noninterest expense	95,531	91,591	195,907	180,962
Income before income taxes	50,217	45,385	91,938	95,240
Income tax expense (benefit)	9,297	8,011	16,828	16,523
Net income (loss)	40,920	37,374	75,110	78,717
Average assets	14,367,000	12,756,000	13,984,000	12,603,000
Personal Banking [Member]
Segment Reporting Information [Line Items]
Net interest income	33,119	30,825	65,446	66,409
Provision for credit losses	1,724	1,711	3,725	3,820
Noninterest income	22,107	25,603	45,669	48,663
Noninterest expense	67,756	63,186	129,765	126,863
Income before income taxes	(14,254)	(8,469)	(22,375)	(15,611)
Income tax expense (benefit)	(1,590)	(1,097)	(2,800)	(2,094)
Net income (loss)	(12,664)	(7,372)	(19,575)	(13,517)
Average assets	$ 6,956,000	$ 6,721,000	$ 6,948,000	$ 6,631,000