SECURITIES SOLD UNDER REPURCHASE AGREEMENTS - Summary of Securities Sold Under Repurchase Agreements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	$ 30,638	$ 53,505
Weighted Average
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	$ 28,694	$ 44,324	$ 50,988
Average interest rate during the year	0.20%	0.22%	0.34%
Weighted average interest rate at year-end	0.18%	0.19%	0.30%
Maximum
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	$ 49,836	$ 56,203	$ 68,300