STOCK OPTIONS - Narrative (Details) $ / shares in Units, $ in Thousands		1 Months Ended	12 Months Ended
	Jan. 15, 2020 shares	Oct. 31, 2015 shares	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) employee $ / shares shares	Dec. 31, 2017 USD ($) $ / shares shares	Aug. 31, 2019 shares	Aug. 31, 2017 shares	Jul. 31, 2015 shares	Jul. 31, 2012 shares	Oct. 30, 2007 shares	Dec. 31, 2001 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option expiration period			10 years
Option vesting period			7 years
Granted (in shares)			1,379,500	225,000	1,728,000
Share-based compensation expense | $			$ 3,581	$ 2,224	$ 871
Closing stock price for computation of intrinsic value (in dollars per share) | $ / shares			$ 8.46
Stock options outstanding and expected to vest (in shares)			3,772,139
Aggregate intrinsic value of all stock options outstanding and expected to vest | $			$ 14,820
Stock options outstanding and expected to vest, weighted average exercise price (in dollars per share) | $ / shares			$ 4.53
Stock options outstanding and exercisable (in shares)			2,481,929
Aggregate intrinsic value of currently exercisable stock options | $			$ 12,730
Weighted average exercise price (in dollars per share) | $ / shares			$ 3.33
Weighted average remaining contractual term			6 years
Stock options outstanding and exercisable, weighted average remaining contractual term			7 years
Intrinsic value of options exercised | $			$ 1,420	4,460	220
Intrinsic value of options granted | $			$ 6,300	$ 540	$ 3,140
Weighted average grant date fair value of options granted (in dollars per share) | $ / shares			$ 4.57	$ 2.40	$ 1.82
Fair value of option shares vested | $			$ 2,130	$ 1,440	$ 810
Shares issued in stock swaps (in shares)			222,601	720,772	47,372
Shares surrendered in period (in shares)				22,711	34,687
Stock swap to acquire options (in shares)				17,289	19,688
Number of employees, modified vesting terms | employee				2
Compensation costs | $				$ 190
Unrecognized stock-based compensation cost | $			$ 3,520
Unrecognized stock-based compensation cost, recognition period			1 year
Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares received in stock swaps (in shares)			125,948	570,343	129,378
Restricted
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option vesting period		5 years
Unrecognized stock-based compensation cost | $			$ 70
Grants to date (in shares)		225,922
Shares vested to date (in shares)			180,740
2001 Executive and Employee Stock Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized under common stock option plans (in shares)											1,200,000
2003 Executive and Employee Stock Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized under common stock option plans (in shares)										1,700,000
2012 Share Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized under common stock option plans (in shares)									750,000
Remaining shares for issuance (in shares)			160,000
2015 Executive and Employee Stock Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized under common stock option plans (in shares)								2,000,000
Remaining shares for issuance (in shares)			900,000
2017 Executive and Employee Stock Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized under common stock option plans (in shares)							3,000,000
Remaining shares for issuance (in shares)			480,000
2019 Share Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized under common stock option plans (in shares)						2,000,000
Remaining shares for issuance (in shares)			2,000,000
Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option vesting period	3 years
Granted (in shares)	1,300,000