SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) segment	Jun. 30, 2019 USD ($)	Jan. 01, 2020 USD ($)	Dec. 31, 2019 USD ($)
Property, Plant and Equipment [Line Items]
Available-for-sale securities, cost basis						$ 2,000,000.0
Fair value						2,000,000.0
Unrealized gain						0
Unrealized loss						0
Long-term investments	$ 0		$ 0			0
Impairment charges	0	$ 0	0	$ 0
Realized investment gains (losses)	0	0	0	0
Unrealized gain on investments	0	9,000	0	14,000
Income tax penalties and interest expense	0	$ 0	$ 0	$ 0
Number of operating segments | segment			1
Operating lease liability	397,000		$ 397,000		$ 400,000	0
Operating lease right-of-use asset, net	$ 584,000		$ 584,000		$ 400,000	$ 0
Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives			3 years
Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives			5 years