INTEREST RATE SWAPS - CASH FLOW HEDGES (Details) - Interest rate swap - Cash flow hedge $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2013 item
Derivative [Line Items]
Number of derivative agreements | item			2
Summary information about interest rate swaps
Notional amount	$ 20,000
Assets / (Liabilities)	(285)	$ (393)
Unrealized Gain (Loss) in AOCI	(185)	(256)
1-month LIBOR
Summary information about interest rate swaps
Notional amount	$ 10,000
Pay rate (as a percent)	2.17%
Assets / (Liabilities)	$ (126)	(186)
Unrealized Gain (Loss) in AOCI	(82)	(121)
3-month LIBOR
Summary information about interest rate swaps
Notional amount	$ 10,000
Pay rate (as a percent)	2.33%
Assets / (Liabilities)	$ (159)	(207)
Unrealized Gain (Loss) in AOCI	$ (103)	$ (135)