FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS - Current Available-for-Sale Marketable Debt Securities (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost		$ 24,947,000
Gross Unrealized Gains		1,000
Gross Unrealized Losses		(1,000)
Fair Value	$ 0	24,947,000
Proceeds from maturities of marketable debt securities	25,000,000	35,000,000
Gross realized gains (losses) from the maturities of available-for-sale marketable debt securities	$ 0	0
Treasury discount notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost		24,947,000
Gross Unrealized Gains		1,000
Gross Unrealized Losses		(1,000)
Fair Value		$ 24,947,000