Business Segments - Financial Information by Business Segment (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Segment Reporting Information [Line Items]
Interest and dividend income	$ 118,447	$ 123,327	$ 230,621	$ 248,382
Interest expense	6,219	7,472	10,683	16,050
NET INTEREST INCOME	112,228	115,855	219,938	232,332
Provision for credit losses	(812)	(21,025)	(4,250)	(48,984)
Net interest income after provision for credit losses	113,040	136,880	224,188	281,316
Non-interest income	26,983	36,112	57,365	69,320
Non-interest expense	87,019	83,812	174,569	170,139
Income before provision for income taxes	53,004	89,180	106,984	180,497
Provision for income taxes	10,256	18,592	20,114	36,793
Net income	42,748	70,588	86,870	143,704
Preferred stock dividends	2,531	2,531	5,063	5,063
Net income available to common shareholders	40,217	68,057	81,807	138,641
Community Banking [Member]
Segment Reporting Information [Line Items]
Interest and dividend income	118,447	123,327	230,621	248,382
Interest expense	6,219	7,472	10,683	16,050
NET INTEREST INCOME	112,228	115,855	219,938	232,332
Provision for credit losses	(812)	(21,025)	(4,250)	(48,984)
Net interest income after provision for credit losses	113,040	136,880	224,188	281,316
Non-interest income	20,456	28,963	43,003	54,540
Non-interest expense	83,112	79,818	166,339	161,829
Income before provision for income taxes	50,384	86,025	100,852	174,027
Provision for income taxes	9,706	17,929	18,826	35,434
Net income	40,678	68,096	82,026	138,593
Preferred stock dividends	2,531	2,531	5,063	5,063
Net income available to common shareholders	38,147	65,565	76,963	133,530
Trust and Investment Services [Member]
Segment Reporting Information [Line Items]
Non-interest income	6,527	7,149	14,362	14,780
Non-interest expense	3,907	3,994	8,230	8,310
Income before provision for income taxes	2,620	3,155	6,132	6,470
Provision for income taxes	550	663	1,288	1,359
Net income	2,070	2,492	4,844	5,111
Net income available to common shareholders	$ 2,070	$ 2,492	$ 4,844	$ 5,111