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Stock-based Compensation (Tables)
3 Months Ended
Mar. 31, 2021
Stock-based Compensation  
Summary of performance share units activity

Weighted-Average

Shares

Grant Date Fair Value

Outstanding at December 31, 2020

283,223

$

24.26

Granted

213,180

35.12

Vested

(60,990)

22.45

Forfeited

Performance adjustment

(12,609)

21.80

Outstanding at March 31, 2021

422,804

$

30.07

Summary of restricted stock units activity

Weighted-Average

Shares

Grant Date Fair Value

Outstanding at December 31, 2020

1,242,387

$

19.42

Granted

1,163,664

24.43

Vested

(352,548)

19.42

Forfeited

(14,968)

21.35

Outstanding at March 31, 2021

2,038,535

$

22.27

Summary of stock option activity

 

 

 

Weighted-

 

 

Weighted-

 

Average

 

Average

 

Remaining

Aggregate

Exercise Price

 

Contractual

Intrinsic

    

Shares

    

per Share

    

Term (in years)

    

Value

Outstanding at December 31, 2020

 

3,860,481

$

17.78

 

7.2

$

13,011

Granted

 

63,000

19.97

Exercised

 

(289,164)

14.18

Cancelled

 

(25,491)

19.30

Outstanding at March 31, 2021

 

3,608,826

$

18.09

 

7.0

$

20,895

Exercisable at March 31, 2021

 

2,353,069

$

17.57

 

6.3

$

14,949

Schedule of fair value assumption using Black-Scholes option-pricing model

Three months ended March 31, 

2021

2020

Risk-free interest rate

0.5

%  

1.5

%  

Volatility

68.3

%  

65.5

%  

Expected term (years)

6.0

6.1

Expected dividend yield

%  

%  

Summary of stock-based compensation

Three months ended March 31, 

2021

2020

Research and development

$

1,217

    

$

770

Selling, general and administrative

 

5,662

 

4,181

Total stock-based compensation expense

$

6,879

$

4,951