LOANS - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net deferred loan origination fees and unamortized premium and discount	$ 13,500,000		$ 13,500,000		$ 13,500,000
Non-accretable discount on acquired credit impaired loans	232,000		232,000		1,400,000
Accrued interest receivable on loans	10,800,000		$ 10,800,000		8,800,000
Nonaccrual status, days past due			90 days
Total nonaccrual loans	62,100,000		$ 62,100,000		57,300,000
Interest foregone on nonaccrual loans	1,400,000	$ 1,000,000	3,800,000	$ 3,800,000
Related Allowance	9,170,000		9,170,000		5,667,000
Pre-modification outstanding recorded investment			0	9,066,000
Recorded investment	0	8,938,000	0	8,938,000
Allowance for loan losses, troubled debt restructurings	243,000		243,000
Troubled debt restructuring	899,000		899,000
Consumer and other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Overdrafts	42,000		42,000		48,000
Related Allowance	33,000		33,000		$ 34,000
Pre-modification outstanding recorded investment			0	208,000
Recorded investment	$ 0	$ 208,000	$ 0	$ 208,000
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	0.70%		0.70%		1.10%
Loans	$ 10,000,000		$ 10,000,000		$ 17,500,000