Organization and Basis of Presentation - Additional Information (Details) $ / shares in Units, $ in Thousands		3 Months Ended	12 Months Ended
	Mar. 11, 2019 USD ($) $ / shares shares	Mar. 31, 2019 USD ($) shares	Dec. 31, 2018 USD ($)	Mar. 05, 2019 shares
Organization and Basis of Presentation [Line Items]
Entity incorporation, date of incorporation		Jun. 17, 2009
Net proceeds from IPO, after deducting underwriters’ discounts and commissions | $	$ 7,100
Common stock, conversion basis		one-to-one basis
Stock split, conversion ratio		12.2
Stockholders' equity, reverse stock split		The Company’s common stock and convertible preferred stock on a 12.2-for-one basis (the “Reverse Stock Split”)
Accumulated deficit | $		$ (139,664)	$ (126,865)
Cash and cash equivalents | $		$ 138,064	39,643
Common Stock
Organization and Basis of Presentation [Line Items]
Common stock issued		6,555,000
Proceeds from initial public offering | $	$ 100,100
Issuance of common stock upon net exercise of warrants, shares	101,744	101,744
Fractional shares issued in reverse stock split		45
Warrants
Organization and Basis of Presentation [Line Items]
Convertible preferred stock, shares issued upon conversion	54,903
Preferred Stock
Organization and Basis of Presentation [Line Items]
Fractional shares issued in reverse stock split		69
Initial Public Offering
Organization and Basis of Presentation [Line Items]
Common stock issued	6,555,000
Common stock, offering price per share | $ / shares	$ 17.00
Offering costs | $	$ 4,200
Stock split, conversion ratio	1
Initial Public Offering | Common Stock
Organization and Basis of Presentation [Line Items]
Convertible preferred stock, shares issued upon conversion				18,670,259
Over Allotment Option
Organization and Basis of Presentation [Line Items]
Common stock issued	855,000
Offering costs | $			$ 1,500
Private Placement
Organization and Basis of Presentation [Line Items]
Common stock issued	588,235
Proceeds from issuance of common stock | $	$ 10,000