INTEREST RATE SWAPS - CASH FLOW HEDGES (Details) - Interest rate swap - Cash flow hedge $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2013 DerivativeInstrument
Derivative [Line Items]
Number of derivative agreements | DerivativeInstrument			2
Summary information about interest rate swaps
Notional amount	$ 20,000
Assets / (Liabilities)	275	$ (91)
Unrealized Gain (Loss) in AOCI	217	(73)
1-month LIBOR
Summary information about interest rate swaps
Notional amount	$ 10,000
Pay rate (as a percent)	2.17%
Assets / (Liabilities)	$ 139	(60)
Unrealized Gain (Loss) in AOCI	110	(25)
3-month LIBOR
Summary information about interest rate swaps
Notional amount	$ 10,000
Pay rate (as a percent)	2.33%
Assets / (Liabilities)	$ 136	(31)
Unrealized Gain (Loss) in AOCI	$ 107	$ (48)