Risks and Uncertainties - Additional Information (Details)		1 Months Ended	3 Months Ended
	Jun. 21, 2018 USD ($) $ / shares shares	Jun. 30, 2018 USD ($) $ / shares shares	Mar. 31, 2019 USD ($) Distributor	Dec. 31, 2018 USD ($)
Risks And Uncertainties [Line Items]
Working capital			$ 51,900,000	$ 65,600,000
Number of specialty pharmaceutical distributor | Distributor			1
Specialty Pharmaceutical Distributor In United States
Risks And Uncertainties [Line Items]
Accounts receivable			$ 211,600	$ 195,730
IPO
Risks And Uncertainties [Line Items]
Proceeds from issuance of common stock net of underwriting discount and other offering expenses	$ 77,500,000	$ 77,500,000
IPO | Common Stock
Risks And Uncertainties [Line Items]
Common stock, shares issued | shares	5,980,000	5,980,000
Common stock, issue price per share | $ / shares	$ 15.00	$ 15.00