Business Segment Reporting - Schedule of Segment Financial Results (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Segment Reporting Information [Line Items]
Net interest income	$ 233,485	$ 209,765	$ 668,631	$ 604,951
Provision for credit losses	22,000	(5,000)	28,900	11,500
Noninterest income	128,723	107,907	428,736	348,393
Noninterest expense	231,396	208,869	660,301	611,153
Income before income taxes	108,812	113,803	408,166	330,691
Income tax expense (benefit)	20,822	19,336	76,657	56,169
NET INCOME	87,990	94,467	331,509	274,522
Average assets	36,310,000	35,873,000	37,666,000	34,402,000
Commercial Banking [Member]
Segment Reporting Information [Line Items]
Net interest income	150,080	150,871	444,176	430,158
Provision for credit losses	20,156	(5,720)	25,183	8,096
Noninterest income	16,785	17,048	100,379	62,306
Noninterest expense	87,120	78,708	246,230	221,883
Income before income taxes	59,589	94,931	273,142	262,485
Income tax expense (benefit)	11,403	16,130	51,298	44,584
NET INCOME	48,186	78,801	221,844	217,901
Average assets	17,658,000	15,766,000	17,122,000	14,987,000
Institutional Banking [Member]
Segment Reporting Information [Line Items]
Net interest income	43,382	21,203	104,615	64,599
Provision for credit losses	162	172	402	539
Noninterest income	89,386	65,568	243,740	202,769
Noninterest expense	82,073	73,369	234,185	217,257
Income before income taxes	50,533	13,230	113,768	49,572
Income tax expense (benefit)	9,670	2,248	21,367	8,419
NET INCOME	40,863	10,982	92,401	41,153
Average assets	11,999,000	11,976,000	13,396,000	11,734,000
Personal Banking [Member]
Segment Reporting Information [Line Items]
Net interest income	40,023	37,691	119,840	110,194
Provision for credit losses	1,682	548	3,315	2,865
Noninterest income	22,552	25,291	84,617	83,318
Noninterest expense	62,203	56,792	179,886	172,013
Income before income taxes	(1,310)	5,642	21,256	18,634
Income tax expense (benefit)	(251)	958	3,992	3,166
NET INCOME	(1,059)	4,684	17,264	15,468
Average assets	$ 6,653,000	$ 8,131,000	$ 7,148,000	$ 7,681,000