COMMITMENTS, CONTINGENCIES AND DERIVATIVES (Schedule of Swapped Variable Cost for Fixed Cost and Terms of Interest Rate Swap Agreements) (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Derivative [Line Items]
Derivative, fair value	$ 98,000	$ 15,000
Loss on Cash Flow Hedge Ineffectiveness	0	0
Interest rate swaps
Derivative [Line Items]
Notional Amount	43,000,000	43,000,000
Derivative, fair value	(6,711,000)	(5,682,000)
Interest rate swaps | Contract, One
Derivative [Line Items]
Notional Amount	$ 10,000,000	10,000,000
Trade Date	Mar. 18, 2009
Maturity Date	Jun. 30, 2021
Variable Index Received	3 months
Fixed Rate Paid	5.09%
Derivative, fair value	$ (303,000)	(272,000)
Interest rate swaps | Contract, Two
Derivative [Line Items]
Notional Amount	$ 10,000,000	10,000,000
Trade Date	Jul. 08, 2009
Maturity Date	Jun. 30, 2029
Variable Index Received	3 months
Fixed Rate Paid	5.84%
Derivative, fair value	$ (1,932,000)	(1,655,000)
Interest rate swaps | Contract, Three
Derivative [Line Items]
Notional Amount	$ 10,000,000	10,000,000
Trade Date	May 06, 2010
Maturity Date	Jun. 30, 2030
Variable Index Received	3 months
Fixed Rate Paid	5.71%
Derivative, fair value	$ (1,938,000)	(1,636,000)
Interest rate swaps | Contract, Four
Derivative [Line Items]
Notional Amount	$ 5,000,000	5,000,000
Trade Date	Mar. 14, 2011
Maturity Date	Mar. 30, 2031
Variable Index Received	3 months
Fixed Rate Paid	4.35%
Derivative, fair value	$ (1,036,000)	(877,000)
Interest rate swaps | Contract, Five
Derivative [Line Items]
Notional Amount	$ 8,000,000	8,000,000
Trade Date	May 04, 2011
Maturity Date	Jul. 07, 2031
Variable Index Received	3 months
Fixed Rate Paid	4.14%
Derivative, fair value	$ (1,502,000)	(1,242,000)
Forward-Starting Interest Rate Swap
Derivative [Line Items]
Notional Amount	$ 0	25,000,000
Forward-Starting Interest Rate Swap | Contract, One
Derivative [Line Items]
Variable Index Received	1 month
Forward-Starting Interest Rate Swap | Contract, Two
Derivative [Line Items]
Notional Amount	$ 0	25,000,000
Trade Date	Feb. 25, 2015
Maturity Date	Feb. 25, 2019
Variable Index Received	1 month
Fixed Rate Paid	1.74%
Derivative, fair value	$ 0	$ 30,000