STOCK BASED COMPENSATION - Options (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
STOCK BASED COMPENSATION
Options granted (in shares)	194,031
Stock-based compensation expense	$ 1,312	$ 325	$ 300
Options outstanding (in shares)	4,238,892		4,079,888
Weighted-average fair value of options granted (in dollars per share)	$ 21.65	$ 1.54
Unrecognized stock-based compensation balance for unvested options	$ 15,400	$ 5,300
Unrecognized stock-based compensation balance for unvested options expected to be recognized (in years)	1 year 7 months 6 days	2 years 3 months 18 days

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

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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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Gross number of share options (or share units) granted during the period.

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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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Number of options outstanding, including both vested and non-vested options.

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