Stockholders' equity - Narrative (Details)	3 Months Ended				6 Months Ended		12 Months Ended
	Jun. 30, 2023 USD ($) $ / shares shares	Mar. 31, 2023 USD ($) shares	Jun. 30, 2022 shares	Mar. 31, 2022 USD ($) shares	Jun. 30, 2023 USD ($) vote $ / shares shares	Jun. 30, 2022 USD ($) shares	Dec. 31, 2013 $ / shares shares	Dec. 31, 2022 $ / shares shares	Nov. 30, 2022 USD ($)	Jun. 09, 2022 $ / shares shares	Jun. 08, 2022 shares	Feb. 28, 2022 USD ($)	May 31, 2020 USD ($)
Class of Stock [Line Items]
Preferred stock, shares authorized (in shares)	25,000,000				25,000,000			25,000,000
Preferred stock, shares issued (in shares)	0				0			0
Net proceeds from public offering of common stock | $					$ 93,620,000	$ 100,361,000
Number of shares into which warrant issued during period may be converted (in shares)							129,491
Warrant exercise price per share (in dollars per share) | $ / shares							$ 0.05
Contractual life of warrants							10 years
Number of shares of common stock into which warrants may be converted (in shares)	22,590				22,590
Exercise of common stock warrant in exchange for common stock (in shares)					0
Common stock, par value (in dollars per share) | $ / shares	$ 0.0001				$ 0.0001			$ 0.0001		$ 0.0001
Common stock, shares authorized (in shares)	350,000,000				350,000,000			350,000,000		350,000,000	175,000,000
Number of shares reserved for future issuance (in shares)	16,052,928				16,052,928			11,944,664
Common Stock
Class of Stock [Line Items]
Issuance of common stock under public offering, net of issuance costs (in shares)	10,929,438	3,535,093	9,904,964	13,169,903
Exercise of common stock warrant in exchange for common stock (in shares)			16,654
Number of votes per common share | vote					1
2020 ATM
Class of Stock [Line Items]
Amount of shares authorized to be offered and sold | $													$ 100,000,000
Net proceeds from public offering of common stock | $				$ 54,800,000
2020 ATM | Common Stock
Class of Stock [Line Items]
Issuance of common stock under public offering, net of issuance costs (in shares)				11,740,210
At-the-market Equity Offering Program (February 2022 ATM)
Class of Stock [Line Items]
Amount of shares authorized to be offered and sold | $												$ 100,000,000
Net proceeds from public offering of common stock | $		$ 1,600,000				$ 45,800,000
At-the-market Equity Offering Program (February 2022 ATM) | Common Stock
Class of Stock [Line Items]
Issuance of common stock under public offering, net of issuance costs (in shares)		256,386				11,334,657
At-the-market Equity Offering Program (November 2022 ATM)
Class of Stock [Line Items]
Amount of shares authorized to be offered and sold | $									$ 150,000,000
Net proceeds from public offering of common stock | $					$ 92,200,000
At-the-market Equity Offering Program (November 2022 ATM) | Common Stock
Class of Stock [Line Items]
Issuance of common stock under public offering, net of issuance costs (in shares)					14,208,145
Remaining unsold and available amount | $	$ 55,900,000				$ 55,900,000