FAIR VALUE MEASUREMENTS (Change in Fair Value at Level 3) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Transfers into Level 3	$ 0	$ 0
Commodity contract [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	0	(84,000)
Purchases	0	0
Settlements	0	45,000
Unrealized gain (loss) included in earnings	0	39,000
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Balance at end of period	$ 0	$ 0