LOANS - Summary of Information Pertaining to Impaired Loans (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended		12 Months Ended
	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Impaired Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 16,813	$ 14,202	$ 17,083	$ 16,813	$ 17,083	$ 14,202
Troubled debt restructurings not included above	11,023	13,599	12,169	11,023	12,169	13,599
Total impaired loans	27,836	27,801	29,252	27,836	29,252	27,801
Interest income recognized on impaired loans	185	1,010	320	424	560	1,867
Foregone interest income on impaired loans	221	197	247	411	521	950
Purchased Impaired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	33,557	15,428	17,357	33,557	17,357	15,428
Troubled debt restructurings not included above	20,607	20,472	21,020	20,607	21,020	20,472
Total impaired loans	54,164	35,900	38,377	54,164	38,377	35,900
Interest income recognized on impaired loans	280	379	374	976	753	1,625
Foregone interest income on impaired loans	$ 280	$ 281	$ 265	$ 525	$ 601	$ 1,239