Nature of Business and Basis of Presentation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		12 Months Ended
	Apr. 02, 2018	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Conversion of convertible preferred stock into common stock upon initial public offering, Shares	24,168,656
Net loss		$ 23,852	$ 10,217	$ 55,577
Accumulated deficit		$ 119,610		$ 95,758
Initial Public Offering
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Shares issued and sold	10,350,000
Common stock at a public offering price	$ 16.00
Net proceeds from initial public offering after underwriting discounts and commissions and offering expenses	$ 150,800