Stockholders' equity - Narrative (Details) $ / shares in Units, $ in Millions			12 Months Ended
	Feb. 23, 2021 USD ($)	Jun. 01, 2020 $ / shares shares	Dec. 31, 2021 $ / shares shares	Oct. 18, 2021 $ / shares	Dec. 31, 2020 $ / shares shares	May 31, 2020 shares
Class of Stock [Line Items]
Conversation ratio of reverse stock split		0.05
Common stock authorized (shares)		22,500,000	22,500,000		22,500,000	450,000,000
Common stock, par value (USD per share) | $ / shares		$ 0.01	$ 0.01	$ 0.01	$ 0.01
Preferred stock authorized (shares)		50,000,000	50,000,000		50,000,000
Preferred stock, par value (USD per share) | $ / shares		$ 0.01	$ 0.01		$ 0.01
Capital stock authorized (shares)		72,500,000
At-the-Market Offering
Class of Stock [Line Items]
Consideration received from sale of stock | $	$ 75.0
Stock issued in sale (in shares)			1,438,105
Maximum | At-the-Market Offering
Class of Stock [Line Items]
Consideration received from sale of stock | $	$ 72.5