Nature of Business (Details) $ / shares in Units, $ in Thousands				12 Months Ended
	Mar. 06, 2019	Feb. 01, 2017 USD ($) $ / shares shares	Jan. 13, 2017	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Proceeds from initial public offering of common stock, net of issuance costs				$ 0	$ 107,008
Reverse stock split			0.27100271
Cash, cash equivalents, and marketable securities				$ 195,900
IPO
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Issuance of common stock (in shares) | shares		7,319,750
Public offering share price (in dollars per share) | $ / shares		$ 16
Proceeds from initial public offering of common stock, net of issuance costs		$ 117,100
Proceeds from IPO, net of discounts, commissions, and other offering expenses		$ 106,400
Stock converted upon completion of IPO (in shares) | shares		22,283,690
Over-Allotment Option
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Issuance of common stock (in shares) | shares		954,750
Scenario, Forecast
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Duration of funding requirement	12 months