STOCK-BASED COMPENSATION PLANS - Stock-Based Compensation (Details) - USD ($)	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Stock-based compensation
Stock-based compensation	$ 2,976,000	$ 4,139,000
Tax benefit from stock based compensation expense	0	0
Fair value of the assumed awards attributable to future stock-based compensation expense	$ 26,300,000
Expected period for unrecognized expense	3 years
Product cost of revenue
Stock-based compensation
Stock-based compensation	$ 27,000	14,000
Service cost of revenue
Stock-based compensation
Stock-based compensation	130,000	92,000
Research and development
Stock-based compensation
Stock-based compensation	558,000	507,000
Sales and marketing
Stock-based compensation
Stock-based compensation	752,000	984,000
General and administrative
Stock-based compensation
Stock-based compensation	$ 1,509,000	$ 2,542,000

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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