Business Segments - Financial Information by Business Segment (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]
Interest and dividend income	$ 134,117	$ 121,378	$ 364,738	$ 369,760
Interest expense	9,616	6,103	20,299	22,153
NET INTEREST INCOME	124,501	115,275	344,439	347,607
Provision for credit losses	(535)	(1,730)	(4,785)	(50,714)
Net interest income after provision for credit losses	125,036	117,005	349,224	398,321
Non-interest income	32,256	32,755	89,622	102,076
Non-interest expense	91,941	94,701	266,511	264,840
Income before provision for income taxes	65,351	55,059	172,335	235,557
Provision for income taxes	12,318	10,651	32,432	47,445
Net income	53,033	44,408	139,903	188,112
Preferred stock dividends	2,531	2,531	7,594	7,594
Net income available to common shareholders	50,502	41,877	132,309	180,518
Community Banking [Member]
Segment Reporting Information [Line Items]
Interest and dividend income	134,117	121,378	364,738	369,760
Interest expense	9,616	6,103	20,299	22,153
NET INTEREST INCOME	124,501	115,275	344,439	347,607
Provision for credit losses	(535)	(1,730)	(4,785)	(50,714)
Net interest income after provision for credit losses	125,036	117,005	349,224	398,321
Non-interest income	25,739	25,466	68,743	80,007
Non-interest expense	88,144	90,599	254,484	252,428
Income before provision for income taxes	62,631	51,872	163,483	225,900
Provision for income taxes	11,747	9,982	30,573	45,417
Net income	50,884	41,890	132,910	180,483
Preferred stock dividends	2,531	2,531	7,594	7,594
Net income available to common shareholders	48,353	39,359	125,316	172,889
Trust and Investment Services [Member]
Segment Reporting Information [Line Items]
Non-interest income	6,517	7,289	20,879	22,069
Non-interest expense	3,797	4,102	12,027	12,412
Income before provision for income taxes	2,720	3,187	8,852	9,657
Provision for income taxes	571	669	1,859	2,028
Net income	2,149	2,518	6,993	7,629
Net income available to common shareholders	$ 2,149	$ 2,518	$ 6,993	$ 7,629