Stockholders' equity (Details)		3 Months Ended
	Nov. 12, 2020 USD ($)	Mar. 31, 2022 USD ($) Vote $ / shares shares	Mar. 31, 2021 USD ($) shares	Dec. 31, 2021 $ / shares shares
Stockholders' equity
Stock, shares authorized		440,000,000
Common stock, shares authorized		400,000,000		400,000,000
Common stock, par value (in dollars per share) | $ / shares		$ 0.001		$ 0.001
Preferred stock, shares authorized		40,000,000
Preferred stock, par value (in dollars per share) | $ / shares		$ 0.001
Number of shares issued		0	0
Commission payable as a percentage of gross proceeds from sale of common stock under ATM offering	3.00%
Number of voting rights per common share | Vote		1
Stock based compensation expense | $		$ 2,084,060	$ 1,822,562
Shelf Registration Statement
Maximum amount to be issued under universal shelf registration statement | $	$ 350,000,000.0
Maximum amount to be issued under at-the-market offering program | $	$ 50,000,000.0