DISCLOSURES ABOUT FAIR VALUE - Non-Financial Assets Measured at Fair Value on a Non-Recurring Basis (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Investment in unconsolidated affiliate, total loss	$ 1,355,000
Fair Value Measured on a Non-recurring Basis | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Investment in unconsolidated affiliate	0
Mindjet
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Investment in unconsolidated affiliate, total loss	1,312,000
Carrying value of other investments	$ 0	$ 2,300,000