Accounting policies - Cash and cash equivalents (Details) - USD ($)	Dec. 31, 2021	Dec. 31, 2020
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash Equivalents, at Carrying Value	$ 7,738,216	$ 9,275,893
Cash, Uninsured Amount	7,800,000
Cash And Restricted Cash Equivalents Held In Foreign Bank	33,100,000
Deposits held in foreign bank	6,400,000
Certificate of deposit [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash Equivalents, at Carrying Value	7,400,000	$ 8,500,000
Deposits held in foreign bank	$ 2,500,000