Equity Incentive Plans (Tables)

12 Months Ended

Dec. 31, 2020

Summary of Changes in Outstanding Options

The following table summarizes the changes in outstanding stock options for the years ended December 31, 2018, December 31, 2019, and December 31, 2020.

	Options			Average Exercise Price		Average Fair Value of Time-Based Options at Grant Date		Aggregate Intrinsic Value			Weighted Average Remaining Contractual Term (Years)
Outstanding at December 31, 2017		8,024,761
Granted		187,080		$	14.63		4.98
Exercised		(425,505	)		5.33
Forfeited		(859,162	)		7.84
Outstanding at December 31, 2018		6,927,174			9.39				4,089			5.2
Granted		337,000			6.43		2.16
Exercised		(215,300	)		5.33
Forfeited		(730,157	)		13.00
Outstanding at December 31, 2019		6,318,717			8.95				41,784			4.4
Granted		300,000			3.67		5.04
Exercised		(114,000	)		5.04
Forfeited		(3,216,984	)		5.99
Outstanding at December 31, 2020		3,287,733			7.63				(41,545	)		3.3
Exercisable at December 31, 2020		2,952,075			10.49				(28,698	)		3.8
Expected to vest at December 31, 2020    (excluding performance-based options)		329,411		$	8.40			$	(2,346	)		7.7

Time Based Stock Options [Member]

Fair Value of Options Granted

The fair value of time-based options granted during the year ended December 31, 2020 was estimated on the grant date using a Black-Scholes option valuation model based on the assumptions in the following table:

Expected dividend rate	—%
Risk-free interest rate	0.2% to 2.44%
Volatility	29.06% to 135.74%
Expected option term	1.8 years — 5 years

Performance-based Restricted Stock Units [Member]

Fair Value of Options Granted

The PRSUs and Restricted Cash awards are measured at fair value based on Monte Carlo simulation models, based on the assumptions in the table below.

Expected dividend rate	—%
Risk-free interest rate	0.30% to 0.32%
Volatility	106.31% to 140.02%
Weighted average grant date fair value	$	1.02