SEGMENT REPORTING - Operating Segments and Reconciliation of Information to Condensed Consolidated Financial Statements (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Interest income	$ 450,284	$ 423,560	$ 347,869
Interest expense	25,766	60,401	82,561
Provision/ (credit) for credit losses	(45,556)	85,669	4,684
Non-interest income	102,055	102,716	71,322
Non-interest expenses	260,470	255,782	179,085
Income before income tax expense	311,659	124,424	152,861
Income tax expense	76,552	27,471	36,428
Net income	235,107	96,953	116,433
Assets	12,590,726	12,798,429	8,629,002
Inter-Segment Elimination
Segment Reporting Information [Line Items]
Interest income	(12)	(13)	(37)
Interest expense	(12)	(13)	(37)
Provision/ (credit) for credit losses	0	0	0
Non-interest income	(7,411)	(865)	(667)
Non-interest expenses	(868)	(865)	(667)
Income before income tax expense	(6,543)	0	0
Income tax expense	0	0	0
Net income	(6,543)	0	0
Assets	(67,659)	(71,211)	(22,352)
Community Banking | Operating Segments
Segment Reporting Information [Line Items]
Interest income	450,284	423,560	347,867
Interest expense	25,778	60,414	82,598
Provision/ (credit) for credit losses	(45,556)	85,669	4,684
Non-interest income	80,077	78,940	55,042
Non-interest expenses	240,996	237,910	166,802
Income before income tax expense	309,143	118,507	148,825
Income tax expense	74,036	25,907	35,350
Net income	235,107	92,600	113,475
Assets	12,590,176	12,800,537	8,624,590
Insurance | Operating Segments
Segment Reporting Information [Line Items]
Interest income	2	6	26
Interest expense	0	0	0
Provision/ (credit) for credit losses	0	0	0
Non-interest income	7,011	6,810	6,621
Non-interest expenses	5,869	5,686	5,731
Income before income tax expense	1,144	1,130	916
Income tax expense	339	313	258
Net income	805	817	658
Assets	9,110	11,335	10,340
Investment Management | Operating Segments
Segment Reporting Information [Line Items]
Interest income	10	7	13
Interest expense	0	0	0
Provision/ (credit) for credit losses	0	0	0
Non-interest income	22,378	17,831	10,326
Non-interest expenses	14,473	13,051	7,219
Income before income tax expense	7,915	4,787	3,120
Income tax expense	2,177	1,251	820
Net income	5,738	3,536	2,300
Assets	$ 59,099	$ 57,768	$ 16,424