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Stock-Based Compensation - Schedule of Black Scholes Option-Pricing Model (Details) - 2015 ESPP - $ / shares
12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Expected term (in years) 6 months 6 months
Volatility 63.30%  
Volatility, Minimum   81.50%
Volatility, Maximum   127.50%
Risk-free interest rate 0.10%  
Risk-free interest rate, Minimum   0.10%
Risk-free interest rate, Maximum   0.20%
Weighted-average grant date fair value per share $ 5.16 $ 5.42