GOODWILL AND INTANGIBLE ASSETS - Intangible assets (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Finite-lived intangible assets
Gross Carrying Amount	$ 71,083		$ 71,083
Accumulated Amortization	(37,959)		(36,197)
Total	33,124		34,886
Amortization of intangible assets	1,762	$ 1,810
Core deposits
Finite-lived intangible assets
Gross Carrying Amount	57,012		57,012
Accumulated Amortization	(32,131)		(30,674)
Total	24,881		26,338
Customer relationship
Finite-lived intangible assets
Gross Carrying Amount	14,071		14,071
Accumulated Amortization	(5,828)		(5,523)
Total	$ 8,243		$ 8,548