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Fair Value of Financial Instruments - Narrative (Details) - USD ($)
6 Months Ended
Apr. 04, 2018
Jun. 30, 2020
Jun. 30, 2019
Apr. 14, 2020
Dec. 31, 2019
Mar. 27, 2018
Debt Instrument [Line Items]            
Proceeds from debt   $ 4,791,000 $ 0      
Unsecured obligations | 2.50% Convertible notes due 2023            
Debt Instrument [Line Items]            
Proceeds from debt $ 171,500,000          
Fair value   $ 122,800,000     $ 133,800,000  
Aggregate principal amount $ 171,500,000         $ 150,000,000.0
Unsecured obligations | PPP            
Debt Instrument [Line Items]            
Aggregate principal amount       $ 4,800,000