SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Adoption of the new revenue standard Income Statement (Details 6) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue	$ 4,058	$ 5,401	$ 3,760	$ 2,911	$ 3,060	$ 5,707	$ 2,542	$ 4,156	$ 16,131	$ 15,465
Costs and expenses									15,819	15,940
Provision for income taxes									(8)	543
Net income	$ 639	$ 1,277	$ (188)	$ (495)	$ (559)	$ 1,145	$ 114	$ 301	$ 1,233	$ 1,001
Net income per share - basic (in dollars per share)	$ 0.03	$ 0.06	$ (0.01)	$ (0.02)	$ (0.03)	$ 0.05	$ 0.01	$ 0.01	$ 0.06	$ 0.05
Net income per share - diluted (in dollars per share)	$ 0.03	$ 0.06	$ (0.01)	$ (0.02)	$ (0.03)	$ 0.05	$ 0.01	$ 0.01	$ 0.06	$ 0.05
Accounting Standards Update 2014-09 | As Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue										$ 16,282
Costs and expenses										16,054
Provision for income taxes										965
Net income										$ 1,282
Net income per share - basic (in dollars per share)										$ 0.06
Net income per share - diluted (in dollars per share)										$ 0.06
Accounting Standards Update 2014-09 | Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue										$ (817)
Costs and expenses										(114)
Provision for income taxes										(422)
Net income										$ (281)
Net income per share - basic (in dollars per share)										$ (0.01)
Net income per share - diluted (in dollars per share)										$ (0.01)