SEGMENT REPORTING - Operating Segments and Reconciliation of Information to Condensed Consolidated Financial Statements (Detail) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Segment Reporting Information [Line Items]
Interest income	$ 106,036	$ 114,261
Interest expense	4,585	9,661
Provision/ (credit) for credit losses	1,635	(34,708)	$ (45,556)
Non-interest income	20,595	28,866
Non-interest expense	62,147	68,173
Income before income tax expense	58,264	100,001
Income tax expense	14,329	24,537
Net income	43,935	75,464
Assets	12,967,416	12,873,366	$ 12,590,726
Inter-Segment Elimination
Segment Reporting Information [Line Items]
Interest income	(3)	(3)
Interest expense	(3)	(3)
Provision/ (credit) for credit losses	0	0
Non-interest income	(2,308)	(217)
Non-interest expense	(236)	(217)
Income before income tax expense	(2,072)	0
Income tax expense	0	0
Net income	(2,072)	0
Assets	(68,791)	(73,137)
Community Banking | Operating Segments
Segment Reporting Information [Line Items]
Interest income	106,037	114,261
Interest expense	4,588	9,664
Provision/ (credit) for credit losses	1,635	(34,708)
Non-interest income	15,055	21,725
Non-interest expense	57,379	63,695
Income before income tax expense	57,490	97,335
Income tax expense	13,555	23,838
Net income	43,935	73,497
Assets	12,967,935	12,878,311
Insurance | Operating Segments
Segment Reporting Information [Line Items]
Interest income	0	1
Interest expense	0	0
Provision/ (credit) for credit losses	0	0
Non-interest income	2,120	2,151
Non-interest expense	1,476	1,487
Income before income tax expense	644	665
Income tax expense	180	183
Net income	464	482
Assets	9,871	11,504
Investment Management | Operating Segments
Segment Reporting Information [Line Items]
Interest income	2	2
Interest expense	0	0
Provision/ (credit) for credit losses	0	0
Non-interest income	5,728	5,207
Non-interest expense	3,528	3,208
Income before income tax expense	2,202	2,001
Income tax expense	594	516
Net income	1,608	1,485
Assets	$ 58,401	$ 56,688