STOCK BASED COMPENSATION (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Stock-based compensation
Weighted average grant date fair value of options granted	$ 9.35	$ 3.71	$ 3.88	$ 3.71
2009 plan
Stock-based compensation
Unrecognized compensation expense	$ 19.1	$ 23.0	$ 19.1	$ 23.0
Weighted average expense recognition period			2 years 7 months 2 days	2 years 8 months 1 day

Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Amount of cost to be recognized for option under share-based payment arrangement.

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- Definition

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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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