Tangible Stockholder Return Plan (Tables)

12 Months Ended

Dec. 31, 2019

Share-based Payment Arrangement [Abstract]

Schedule of Fair Value of Performance Plans Assumptions

The fair value of each option grant is estimated on the grant date using the Black-Scholes option-pricing model, and the following weighted average assumptions:

	Year Ended December 31,
	2019			2018
Estimated dividend yield	0.00		%	0.00		%
Expected volatility	102.14		%	81.73		%
Risk-free interest rate	1.87		%	2.75		%
Expected life of options (in years)	5.20			5.68
Weighted-average fair value per share	$	1.77		$	2.06

The fair value of the SARs was estimated using the Black-Scholes option-pricing model for the respective periods, using the following assumptions:

	July 31, 2019			December 31, 2018
Estimated dividend yield	—			—
Expected volatility	115.82		%	86.71		%
Risk-free interest rate	2.07		%	2.63		%
Expected term (years)	0.51			1.09
Fair value per share of common stock underlying the SAR	$	2.66		$	0.83
SAR exercise price	$	3.80		$	3.80

The fair value of the Performance Plan is estimated at each financial reporting date using the Monte Carlo simulation model and the following assumptions:

	December 31,
	2019			2018
Estimated dividend yield	—			—
Expected volatility	128.30		%	87.19		%
Risk-free interest rate	1.53		%	2.47		%
Expected term (years)	2.17			3.17
Fair value per share of common stock underlying the Performance Plan	$	0.86		$	0.83