Common stock and Class A common stock (Details) $ / shares in Units, $ in Thousands		12 Months Ended
	Apr. 23, 2019 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) Vote $ / shares shares	Dec. 31, 2018 $ / shares shares
Share Price | $ / shares		$ 12.23	$ 10.33
Offering costs | $		$ 9,400
Number of votes | Vote		1
Common stock
Common stock, issued (in shares)		21,746,392	1,006,595
Common stock, outstanding (in shares)		21,746,392	1,006,595
Common stock, shares authorized		100,000,000	18,454,860
Class A common stock
Common stock, issued (in shares)		3,819,732	0
Common stock, outstanding (in shares)		3,819,732	0
Common stock, shares authorized		3,900,000	0
Number of common stock issued upon conversion of each share		1
Common Stock | Common stock
Issuance of common stock upon initial public offering		6,000,000
Stock issued upon conversion of Preferred Stock (in shares)		14,582,161
Common Stock | Class A common stock
Stock issued upon conversion of Preferred Stock (in shares)		3,819,732
IPO
Share Price | $ / shares		$ 14.00
Offering costs | $		$ 9,386
IPO | Common stock
Stock issued upon conversion of Preferred Stock (in shares)	14,582,161
IPO | Class A common stock
Stock issued upon conversion of Preferred Stock (in shares)	3,819,732
IPO | Common Stock
Issuance of common stock upon initial public offering	6,000,000
Share Price | $ / shares	$ 14.00
Proceeds from Issuance Initial Public Offering | $	$ 74,600
Offering costs | $	$ 9,400
Stock issued upon conversion of Preferred Stock (in shares)	14,582,161