INVESTMENTS, AVAILABLE-FOR-SALE SECURITIES (Details) - USD ($)	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Available-for-sale Securities Reconciliation [Abstract]
Amortized cost	$ 10,800,000		$ 10,800,000
Gross unrealized gains	0		0
Gross unrealized losses	(730,000)		(730,000)
Fair value	10,070,000		10,070,000
Available-For-Sale Securities, Unrealized Loss Positions [Abstract]
Continuous unrealized loss position, 12 months or more, aggregated fair value	10,070,000		10,070,000
Continuous unrealized loss position, 12 months or more, gross unrealized losses	(730,000)		(730,000)
Continuous unrealized loss position, 12 months or less, gross unrealized losses	0	$ 0
Auction Rate Securities [Member]
Available-for-sale Securities Reconciliation [Abstract]
Amortized cost	10,800,000		10,800,000
Gross unrealized gains	0		0
Gross unrealized losses	(730,000)		(730,000)
Fair value	10,070,000		10,070,000
Available-For-Sale Securities, Unrealized Loss Positions [Abstract]
Continuous unrealized loss position, 12 months or more, aggregated fair value	10,070,000		10,070,000
Continuous unrealized loss position, 12 months or more, gross unrealized losses	$ (730,000)		$ (730,000)