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Company and Summary of Significant Accounting Policies - Stock-Based Compensation (Details) - Equity Incentive 2011 Plan [Member]
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Significant Accounting Policies [Line Items]    
Expected term (in years) 6 years 6 years
Weighted average volatility (percentage) 108.58% 64.38%
Weighted average risk free interest rate (percentage) 0.46% 1.92%
Expected dividends 0.00% 0.00%
Weighted-average expected forfeiture rate (percentage) 7.72% 9.26%