Business Segment Reporting - Schedule of Segment Financial Results (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Segment Reporting Information [Line Items]
Net interest income	$ 210,355	$ 194,115
Provision for credit losses	(6,500)	(7,500)
Noninterest income	123,678	108,897
Noninterest expense	214,778	200,946
Income before income taxes	125,755	109,566
Income tax expense	19,792	16,923
NET INCOME	105,963	92,643
Average assets	39,154,000	33,052,000
Commercial Banking [Member]
Segment Reporting Information [Line Items]
Net interest income	145,002	136,410
Provision for credit losses	(7,040)	(8,178)
Noninterest income	26,707	8,176
Noninterest expense	79,596	69,725
Income before income taxes	99,153	83,039
Income tax expense	15,606	12,826
NET INCOME	83,547	70,213
Average assets	16,827,000	14,204,000
Institutional Banking [Member]
Segment Reporting Information [Line Items]
Net interest income	26,253	22,138
Provision for credit losses	151	220
Noninterest income	73,262	68,421
Noninterest expense	75,592	71,282
Income before income taxes	23,772	19,057
Income tax expense	3,741	2,943
NET INCOME	20,031	16,114
Average assets	14,677,000	11,603,000
Personal Banking [Member]
Segment Reporting Information [Line Items]
Net interest income	39,100	35,567
Provision for credit losses	389	458
Noninterest income	23,709	32,300
Noninterest expense	59,590	59,939
Income before income taxes	2,830	7,470
Income tax expense	445	1,154
NET INCOME	2,385	6,316
Average assets	$ 7,650,000	$ 7,245,000