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Summary of Significant Accounting Policies - Stock-Based Compensation - ASU 2016-09 (Details) - USD ($)
$ in Thousands
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]      
Accumulated deficit $ (68,193) $ (113,483)  
Accounting Standards Update 2016-09      
New Accounting Pronouncements or Change in Accounting Principle [Line Items]      
Change in Accounting Principle, Accounting Standards Update, Adopted true    
Change in Accounting Principle, Accounting Standards Update, Adoption Date Jan. 01, 2018    
Accounting Standards Update 2016-09 | Cumulative Effect, Period of Adoption, Adjustment      
New Accounting Pronouncements or Change in Accounting Principle [Line Items]      
Accumulated deficit     $ (200)