STOCK-BASED COMPENSATION (Tables)

12 Months Ended

Dec. 31, 2020

Tabular disclosure of stock option grants under the Plan

Grantee Type	# of Options Granted	Issued and Outstanding	Vesting Period	Weighted Average Exercise Price		Weighted Average Grant Date Fair Value (Per Option)
Director Group	150,000	100,000	5 years	$	9.98	$	4.36
Employee Group	4,662,630	3,014,931	3-5 years	$	5.60	$	3.08
Total		3,114,931

Schedule of fair value assumptions of stock option grants

	2020	2019	2018
Weighted average expected life	6.0 years	6.3 years	6.5 years
Risk-free interest rates	0.39% to 0.47%	1.45% to 2.58%	2.28% to 3.00%
Expected volatility	41.0% to 42.5%	32.5% to 37.9%	36.7% to 39.9%
Expected dividend yield	0.00%	0.00%	0.00%

Schedule of summary of option activity under the Plan and changes during the period

	Shares	Weighted Average Exercise Price		Weighted Average Remaining Contractual Terms (Years)	Aggregate Intrinsic Value (in millions)
Outstanding as of January 1, 2019	2,066,529	$	10.23	8.5	$	—
Granted	631,136		3.20
Forfeited or expired	(388,741)		9.73
Outstanding as of December 31, 2019	2,308,924		8.39	8.0		0.2
Granted	2,029,900		1.75
Forfeited or expired	(1,223,893)		2.96
Outstanding as of December 31, 2020	3,114,931	$	6.19	7.9	$	5.9
Exercisable as of December 31, 2020	1,139,811		9.26	6.7		0.4
Vested and expected to vest as of December 31, 2020	3,114,931	$	6.19	7.9	$	5.9

Summary of restricted stock unit grants under the Plan

Grantee Type	# of Restricted Stock Units Granted	Issued and Outstanding	Vesting Period	Weighted Average Grant Date Fair Value (Per Unit)
Director Group	893,996	340,415	1-2 years	$	2.75
Employee Group	1,568,655	254,386	5 years	$	10.59
Total		594,801

Summary of restricted stock awards activity under the Plan

	Units	Weighted Average Grant Date Fair Value (Per Unit)
Non-vested as of January 1, 2019	841,361	$	10.44
Granted	753,986		2.45
Vested	(187,956)		10.35
Forfeited	(226,509)		10.16
Non-vested as of December 31, 2019	1,180,882		5.44
Granted	108,498		2.77
Vested	(600,900)		4.05
Forfeited	(93,679)		9.42
Non-vested as of December 31, 2020	594,801	$	5.72

Summary of performance stock unit grants under the Plan

	Units	Weighted Average Grant Date Fair Value (Per Unit)
Non-vested as of January 1, 2020	—	$	—
Granted	2,471,500		1.14
Vested	—		—
Forfeited	(755,400)		0.59
Non-vested as of December 31, 2020	1,716,100	$	1.38

Performance Stock Units

Schedule of fair value assumptions of stock option grants

	As of December 31, 2020
	Liability-classified	Equity-classified
Term	2.3 to 2.6 years	1.9 to 3.0 years
Risk-free interest rate	0.14% to 0.15%	0.13% to 0.21%
Expected volatility	92.3% to 96.5%	86.1% to 102.2%
Expected dividend yield	0.00%	0.00%