Business Segment Reporting - Schedule of Segment Financial Results (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Segment Reporting Information [Line Items]
Net interest income	$ 222,287	$ 233,485	$ 689,594	$ 668,631
Provision for credit losses	4,977	22,000	41,227	28,900
Noninterest income	133,317	128,723	401,599	428,736
Noninterest expense	231,441	231,396	709,166	660,301
Income (loss) before taxes	119,186	108,812	340,800	408,166
Income tax expense (benefit)	22,632	20,822	61,699	76,657
NET INCOME	96,554	87,990	279,101	331,509
Average assets	39,524,000	36,310,000	39,472,000	37,666,000
Commercial Banking [Member]
Segment Reporting Information [Line Items]
Net interest income	148,666	150,080	444,083	444,176
Provision for credit losses	3,010	20,156	35,110	25,183
Noninterest income	23,091	16,785	71,658	100,379
Noninterest expense	81,767	87,120	251,667	246,230
Income (loss) before taxes	86,980	59,589	228,964	273,142
Income tax expense (benefit)	16,311	12,859	41,114	52,001
NET INCOME	70,669	46,730	187,850	221,141
Average assets	20,838,000	17,658,000	20,425,000	17,122,000
Institutional Banking [Member]
Segment Reporting Information [Line Items]
Net interest income	43,133	43,382	148,615	104,615
Provision for credit losses	423	162	754	402
Noninterest income	86,521	89,386	257,573	243,740
Noninterest expense	87,502	82,073	268,464	234,185
Income (loss) before taxes	41,729	50,533	136,970	113,768
Income tax expense (benefit)	7,866	7,735	24,558	22,353
NET INCOME	33,863	42,798	112,412	91,415
Average assets	12,232,000	11,999,000	12,476,000	13,396,000
Personal Banking [Member]
Segment Reporting Information [Line Items]
Net interest income	30,488	40,023	96,896	119,840
Provision for credit losses	1,544	1,682	5,363	3,315
Noninterest income	23,705	22,552	72,368	84,617
Noninterest expense	62,172	62,203	189,035	179,886
Income (loss) before taxes	(9,523)	(1,310)	(25,134)	21,256
Income tax expense (benefit)	(1,545)	228	(3,973)	2,303
NET INCOME	(7,978)	(1,538)	(21,161)	18,953
Average assets	$ 6,454,000	$ 6,653,000	$ 6,571,000	$ 7,148,000