Organization and nature of operations (Details) $ / shares in Units, $ in Millions				1 Months Ended
	May 15, 2019 $ / shares shares	May 13, 2019 $ / shares shares	Apr. 26, 2019	May 31, 2019 USD ($) $ / shares shares	Sep. 30, 2019 shares	Dec. 31, 2018 shares
Organization and nature of operations
Reverse stock split			0.1880
Common shares, Shares outstanding (in shares)					24,490,742	596,787
Initial public offering
Organization and nature of operations
Common shares, Shares outstanding (in shares)		24,490,742
Initial public offering | Common shares
Organization and nature of operations
Number of shares issued during the period		5,500,000		6,325,000
Share Price | $ / shares		$ 15.00		$ 15.00
Gross proceeds of initial public offering | $				$ 94.9
Number of preferred shares converted in to common shares				17,550,802
Underwriters option | Common shares
Organization and nature of operations
Number of shares issued during the period	825,000
Share Price | $ / shares	$ 15.00