Nature of the Business and Basis of Presentation - Additional Information (Details) $ / shares in Units, $ in Thousands			3 Months Ended						9 Months Ended
	Jul. 22, 2019 USD ($) $ / shares shares	Jul. 05, 2019	Sep. 30, 2019 USD ($) shares	Jun. 30, 2019 shares	Mar. 31, 2019 shares	Sep. 30, 2018 shares	Jun. 30, 2018 shares	Mar. 31, 2018 shares	Sep. 30, 2019 USD ($) shares	Dec. 31, 2018 USD ($) shares
Nature Of Business And Basis Of Presentation [Line Items]
Net proceeds of common stock | $									$ 64,443
Reverse stock split		one-for-seven
Stock split		0.14285
Accumulated deficit | $			$ 134,678						$ 134,678	$ 68,124
Convertible Preferred Stock
Nature Of Business And Basis Of Presentation [Line Items]
Convertible preferred stock, share outstanding	112,500,000		112,500,000						112,500,000	100,000,000
Common Stock
Nature Of Business And Basis Of Presentation [Line Items]
Issuance of common stock, Shares			116,167	148,320	134,013	140,691	187,421	125,123
IPO
Nature Of Business And Basis Of Presentation [Line Items]
Issuance of common stock, Shares	4,500,000
Shares issued, price per share | $ / shares	$ 16.00
Net proceeds of common stock | $	$ 64,000
IPO | Common Stock
Nature Of Business And Basis Of Presentation [Line Items]
Number of preferred stock converted into common stock	16,071,418