GOODWILL AND INTANGIBLE ASSETS - Summary of Other Intangible Assets (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	$ 114,824	$ 116,515
Accumulated Amortization	(32,951)	(31,957)
Total	81,873	84,558
Core deposits
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	93,811	95,711
Accumulated Amortization	(23,148)	(22,727)
Total	$ 70,663	$ 72,984
Amortization Period	10 years	10 years
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	$ 15,281	$ 15,281
Accumulated Amortization	(6,919)	(6,600)
Total	$ 8,362	$ 8,681
Customer relationships | Minimum
Finite-Lived Intangible Assets [Line Items]
Amortization Period	7 years	7 years
Customer relationships | Maximum
Finite-Lived Intangible Assets [Line Items]
Amortization Period	15 years	15 years
Non-compete agreements
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	$ 221	$ 221
Accumulated Amortization	(201)	(190)
Total	$ 20	$ 31
Amortization Period	5 years	5 years
Loan servicing rights
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	$ 5,511	$ 5,302
Accumulated Amortization	(2,683)	(2,440)
Total	2,828	2,862
Impairment loss	$ (100)	$ 200
Loan servicing rights | Minimum
Finite-Lived Intangible Assets [Line Items]
Amortization Period	10 years	10 years
Loan servicing rights | Maximum
Finite-Lived Intangible Assets [Line Items]
Amortization Period	25 years	25 years