STOCKHOLDERS' EQUITY - Restricted Stock Activity (Details)	9 Months Ended
	Sep. 30, 2021 $ / shares shares
Restricted Stock Awards
Number of Shares
Unvested restricted stock awards, beginning balance (in shares) | shares	1,345,819
Granted (in shares) | shares	483,900
Vested (in shares) | shares	(653,758)
Forfeited (in shares) | shares	(136,506)
Unvested restricted stock awards, ending balance (in shares) | shares	1,039,455
Weighted Average Grant Date Fair Value (in usd per share)
Unvested restricted stock awards, beginning balance (in dollars per share) | $ / shares	$ 7.04
Granted (in dollars per share) | $ / shares	13.32
Vested (in dollars per share) | $ / shares	7.22
Forfeited (in dollars per share) | $ / shares	7.73
Unvested restricted stock awards, ending balance (in dollars per share) | $ / shares	$ 9.75
Performance Stock Awards
Number of Shares
Unvested restricted stock awards, beginning balance (in shares) | shares	548,151
Granted (in shares) | shares	168,324
Vested (in shares) | shares	0
Forfeited (in shares) | shares	(194,309)
Unvested restricted stock awards, ending balance (in shares) | shares	522,166
Weighted Average Grant Date Fair Value (in usd per share)
Unvested restricted stock awards, beginning balance (in dollars per share) | $ / shares	$ 7.64
Granted (in dollars per share) | $ / shares	12.69
Vested (in dollars per share) | $ / shares	0
Forfeited (in dollars per share) | $ / shares	9.32
Unvested restricted stock awards, ending balance (in dollars per share) | $ / shares	$ 8.64