ACCRUED AND OTHER LIABILITIES - Environmental Reserves (Details)		3 Months Ended			12 Months Ended		24 Months Ended	27 Months Ended
	Jun. 30, 2016 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jun. 30, 2016 USD ($)	Dec. 31, 2015 USD ($) a	Dec. 31, 2014 USD ($) a	Dec. 31, 2015 USD ($) a	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)
Environmental Reserve for Monitoring Environmental Remediation Work Previously Performed
Environmental reserves
Additional environmental reserve accrued			$ 51,000		$ 500,000	$ 110,000	$ 661,000
Environmental costs funded		$ 528,000
Environmental reserve accrued		133,000						$ 133,000
Wetlands restoration
Environmental reserves
Acres | a					148.4		148.4
Estimated cost	$ 2,000,000	2,000,000		$ 2,000,000				2,000,000
Environmental costs funded		1,300,000						1,300,000
Accrued restoration cost		$ 700,000			$ 1,700,000		$ 1,700,000	$ 700,000	$ 708,000
Area of previously disposed land subject to remediation | a					148.4		148.4
Increase in accrual of remediation costs				$ 300,000
Minimum | Environmental Reserve for Monitoring Environmental Remediation Work Previously Performed
Environmental reserves
Estimated cost					$ 500,000
Minimum | Wetlands restoration
Environmental reserves
Estimated cost					1,700,000
Maximum | Environmental Reserve for Monitoring Environmental Remediation Work Previously Performed
Environmental reserves
Acres | a						1
Estimated cost					1,000,000
Maximum | Wetlands restoration
Environmental reserves
Estimated cost					$ 1,900,000