Convertible Preferred Stock - Additional Information (Details)			12 Months Ended
	Apr. 12, 2016 USD ($) $ / shares shares	Mar. 10, 2015 USD ($) $ / shares shares	Dec. 31, 2017 $ / shares shares	Dec. 31, 2016 $ / shares shares	Dec. 31, 2015 USD ($)
Class Of Stock [Line Items]
Distributions declared or paid prior to conversion		$ 0
Preferred stock, par value | $ / shares	$ 0.0001		$ 0.0001	$ 0.0001
Adjustments to additional paid in capital, increase in carrying amount of convertible preferred stock					$ 228,000
Convertible preferred stock, terms of conversion			a ratio of one share of common stock for each share of convertible preferred stock
Common Stock
Class Of Stock [Line Items]
Conversion of preferred stock, conversion unit	1
Number of shares issued | shares			3,000,000	5,482,000
Convertible preferred stock converted into common stock | shares	7,172,496		0
Convertible preferred stock converted into common stock, carrying value	$ 58,300,000
Series A Convertible Preferred Shares
Class Of Stock [Line Items]
Conversion of preferred stock, conversion unit		1
Preferred stock, par value | $ / shares		$ 0.0001
Deemed dividend per share | $ / shares		$ 0.11
Adjustments to additional paid in capital, increase in carrying amount of convertible preferred stock		$ 228,000
Series B Convertible Preferred Stock
Class Of Stock [Line Items]
Preferred stock, par value | $ / shares		$ 0.0001
Number of shares issued | shares		4,929,948
Preferred stock issuance price | $ / shares		$ 8.93
Gross proceeds from issuance of preferred stock		$ 44,000,000
Offering costs		$ 321,000