Organization - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands			3 Months Ended
	Apr. 10, 2019	Mar. 22, 2019	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Entity incorporation date			Jul. 05, 2016
Net proceeds received from offering		$ 46,600	$ 46,816	$ 89,938
Underwriting discounts and commissions and other offering expenses		$ 3,500
Accumulated deficit			(82,462)		$ (71,393)
Cash, cash equivalents and marketable securities			$ 143,100
Subsequent Event
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Net proceeds received from offering	$ 3,100
Underwriting discounts and commissions and other offering expenses	$ 300
Initial Public Offering
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of common stock shares sold		7,200,000
Issuance price per shares		$ 6.95
Initial Public Offering | Maximum
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Option to purchase of common stock at public offering price		1,080,000
Initial Public Offering | Subsequent Event
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of common stock shares sold	487,934
Issuance price per shares	$ 6.95