Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies - Foreign currency (Details)

v3.20.4
Summary of Significant Accounting Policies - Foreign currency (Details) - USD ($)
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Other (expense) income, net      
Foreign exchange gains (losses) $ 1,105,000 $ (137,000) $ (15,257,000)