GOODWILL AND INTANGIBLE ASSETS - Summary of Other Intangible Assets (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	$ 118,364	$ 118,373
Accumulated Amortization	(25,429)	(22,456)
Total	92,935	95,917
Core deposits
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	95,711	95,711
Accumulated Amortization	(15,679)	(13,326)
Total	$ 80,032	$ 82,385
Amortization Period	10 years	10 years
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	$ 17,561	$ 17,561
Accumulated Amortization	(7,816)	(7,416)
Total	$ 9,745	$ 10,145
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	(157)	(146)
Total	$ 64	$ 75
Amortization Period	5 years	5 years
Loan servicing rights
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	$ 4,871	$ 4,880
Accumulated Amortization	(1,777)	(1,568)
Total	3,094	3,312
Impairment loss	$ 300	$ 500
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