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Fair Value Measurements - Additional Information (Details) - USD ($)
$ in Thousands
Dec. 31, 2019
Dec. 31, 2018
Jul. 31, 2018
Significant Unobservable Inputs (Level 3)      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Fair value of financial liabilities measured at fair value on a recurring basis $ 585 $ 585  
3.5% Convertible Notes Due 2023      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Fair value of convertible debt 126,000 141,000  
Carrying value of convertible debt $ 157,560 $ 148,101 $ 143,723