STOCKHOLDERS' EQUITY - Stock options (Details)	1 Months Ended	6 Months Ended
Apr. 30, 2018 individual shares	Jun. 30, 2019 shares
Share-Based Compensation Awards
Granted (in shares)		356,000
Stock options \| Nonemployees
Share-Based Compensation Awards
Number of individuals \| individual	1
2015 Plan \| Nonemployees
Share-Based Compensation Awards
Granted (in shares)	72,373
Vesting period	4 years
Term of award	10 years
2015 Plan \| Nonemployees \| Tranche one
Share-Based Compensation Awards
Vesting period	12 months
Vesting (as a percent)	25.00%
2015 Plan \| Nonemployees \| Tranche two
Share-Based Compensation Awards
Vesting period	3 years

Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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-Section 50
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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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

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Percentage of vesting of share-based compensation awards.

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Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Number of individuals.

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