Quarterly report pursuant to Section 13 or 15(d)

Intangible assets, royalties, and goodwill - Additional information (Details)

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Intangible assets, royalties, and goodwill - Additional information (Details) - USD ($)
3 Months Ended 6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Jun. 30, 2021
Jun. 30, 2020
Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]          
Amortization expense $ 400,000 $ 400,000 $ 800,000 $ 800,000  
Goodwill 18,614,000   18,614,000   $ 18,614,000
Goodwill, accumulated impairment loss $ 0   0    
Goodwill, impairment expense     $ 0    
Weighted Average          
Finite-Lived Intangible Assets [Line Items]          
Estimated useful lives of intangible assets     9 years 9 months 18 days