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Summary of Significant Accounting Policies - Narrative (Details) - USD ($)
shares in Thousands, $ in Thousands
9 Months Ended
Sep. 30, 2022
Sep. 30, 2022
Sep. 30, 2021
Aug. 31, 2022
Dec. 31, 2021
Feb. 14, 2020
Feb. 05, 2020
Subsidiary, Sale of Stock [Line Items]              
Cash and cash equivalents $ 60,715 $ 60,715     $ 50,708    
Marketable securities 45,760 45,760     106,513    
Commission percentage             3.00%
Proceeds from sale of shares   10,532 $ 0        
4.50% Exchangeable Senior Notes Due 2023 | Senior Notes              
Subsidiary, Sale of Stock [Line Items]              
Long-term debt $ 26,375 $ 26,375     $ 143,750    
Debt instrument, interest rate (as a percent) 4.50% 4.50%     4.50%    
4.50 Percent Exchangeable Senior Notes Due October 2023 | Senior Notes              
Subsidiary, Sale of Stock [Line Items]              
Long-term debt $ 117,375 $ 117,375     $ 0    
Debt instrument, interest rate (as a percent) 4.50% 4.50%          
At-The-Market Offering Program              
Subsidiary, Sale of Stock [Line Items]              
Maximum aggregate offering price of ADS under shelf registration $ 135,000 $ 135,000          
Open Market Sales Agreement, 2020 Prospectus              
Subsidiary, Sale of Stock [Line Items]              
Maximum aggregate offering price of ADS under shelf registration           $ 50,000  
Remaining value of ADSs available for sale $ 39,142 39,142          
Open Market Sales Agreement, 2020 Prospectus | Common Stock              
Subsidiary, Sale of Stock [Line Items]              
Shares sold (in shares) 1,768            
Proceeds from sale of shares $ 10,532            
Open Market Sales Agreement, 2022 Prospectus              
Subsidiary, Sale of Stock [Line Items]              
Maximum aggregate offering price of ADS under shelf registration       $ 100,000      
Remaining value of ADSs available for sale $ 100,000 $ 100,000