Common stock and Class A common stock (Details) $ / shares in Units, $ in Millions		3 Months Ended
	Apr. 23, 2019 USD ($) $ / shares shares	Mar. 31, 2020 Vote $ / shares shares	Dec. 31, 2019 $ / shares shares
Share Price | $ / shares		$ 8.25	$ 12.23
Number of votes | Vote		1
Common stock
Common stock, issued (in shares)		21,824,990	21,746,392
Common stock, outstanding (in shares)		21,824,990	21,746,392
Common stock, shares authorized		100,000,000	100,000,000
Class A common stock
Common stock, issued (in shares)		3,819,732	3,819,732
Common stock, outstanding (in shares)		3,819,732	3,819,732
Common stock, shares authorized		3,900,000	3,900,000
Number of common stock issued upon conversion of each share		1
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 | $	$ 74.6
Offering costs | $	$ 9.4
Stock issued upon conversion of Preferred Stock (in shares)	14,582,161