Nature of Business and Basis of Presentation - Additional Information (Details) - USD ($)			6 Months Ended
	Apr. 30, 2018	Dec. 31, 2017	Jun. 30, 2019
Nature Of Business And Basis Of Presentation [Line Items]
Initial public offering of common stock		6,900,000
Common stock offering price per share		$ 13.00
Additional shares of common stock		900,000
Net proceeds after deducting underwriting discounts		$ 79,327,000
Underwriting discounts and commission amount		6,279,000
Offering costs		$ 4,094,000
Convertible outstanding preferred stock		4,038,000
Aggregate shares of common stock		40,382,000
Temporary equity to additional paid-in capital		$ 97,439,000
Temporary equity to common stock		$ 40,000
Follow-on Offering
Nature Of Business And Basis Of Presentation [Line Items]
Initial public offering of common stock	0
Net proceeds after deducting underwriting discounts	$ 0
Offering costs	$ 41,000
Number of shares sold by selling stockholders	7,350,000
Sale of stock, price per share	$ 25.00
Profit after offering cost amount disgorged by selling shareholders in connection with sale of shares	$ 3,770,000
Transaction costs incurred on behalf of selling stockholders	856,000
Follow-on Offering | Selling, General and Administrative Expenses
Nature Of Business And Basis Of Presentation [Line Items]
Transaction costs incurred on behalf of selling stockholders	$ 815,000
Convertible Preferred Stock [Member]
Nature Of Business And Basis Of Presentation [Line Items]
Conversion of preferred stock, description			ten-for-one