Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements (Details)

v3.21.1
Fair Value Measurements (Details) - USD ($)
3 Months Ended
Mar. 31, 2021
Mar. 31, 2020
Dec. 31, 2020
Summary of financial instruments measured at fair value on a recurring basis      
Investment in non-marketable debt security $ 1,067,000   $ 1,000,000
Total 123,142,000   128,567,000
Convertible Debt [Member]      
Summary of financial instruments measured at fair value on a recurring basis      
Credit losses 0 $ 0  
Other-than-temporary impairment losses 0 $ 0  
Money Market Funds [Member]      
Summary of financial instruments measured at fair value on a recurring basis      
Money market funds 122,075,000   127,567,000
Level 1 [Member]      
Summary of financial instruments measured at fair value on a recurring basis      
Total 122,075,000   127,567,000
Level 1 [Member] | Money Market Funds [Member]      
Summary of financial instruments measured at fair value on a recurring basis      
Money market funds 122,075,000   127,567,000
Level 3 [Member]      
Summary of financial instruments measured at fair value on a recurring basis      
Investment in non-marketable debt security 1,067,000   1,000,000
Total $ 1,067,000   $ 1,000,000