LOANS - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net deferred loan origination fees and unamortized premium and discount	$ 13,600,000		$ 13,600,000		$ 13,600,000
Non-accretable discount on acquired credit impaired loans	234,000		234,000		1,400,000
Accrued interest receivable on loans	9,300,000		$ 9,300,000		8,800,000
Nonaccrual status, days past due			90 days
Total nonaccrual loans	54,800,000		$ 54,800,000		57,300,000
Interest foregone on nonaccrual loans	1,300,000	$ 1,100,000	2,400,000	$ 2,800,000
Related Allowance	10,368,000		10,368,000		5,667,000
Pre-modification outstanding recorded investment			0	9,066,000
Recorded investment	0	9,035,000	0	9,035,000
Allowance for loan losses, troubled debt restructurings	244,000		244,000
Troubled debt restructuring	901,000		901,000
Consumer and other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Overdrafts	55,000		55,000		48,000
Related Allowance	32,000		32,000		$ 34,000
Pre-modification outstanding recorded investment			0	208,000
Recorded investment	$ 0	$ 214,000	$ 0	$ 214,000
Reserved based energy loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of total funded loans	0.40%		0.40%		0.60%
Loans	$ 14,300,000		$ 14,300,000		$ 19,200,000
Energy related service industry loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of total funded loans	0.80%		0.80%		1.10%
Loans	$ 10,100,000		$ 10,100,000		$ 17,500,000