Stockholders' Equity (Details) - USD ($) $ / shares in Units, $ in Thousands				3 Months Ended	9 Months Ended		12 Months Ended
	Apr. 02, 2018	May 03, 2017	Apr. 26, 2017	Sep. 30, 2018	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Class of Stock [Line Items]
Proceeds from issuance of common stock, net of offering costs					$ 103,259	$ 34,294
Registered Direct Offering
Class of Stock [Line Items]
Number of shares issued or sold (in shares)			1,100,000
Common stock purchase price (in dollars per share)			$ 21.50
Proceeds from issuance of common stock, net of offering costs			$ 23,700
At the Market Offering
Class of Stock [Line Items]
Number of shares issued or sold (in shares)				0	0		599,284
Common stock maximum amount available for issuance		$ 75,000
Proceeds of stock sale							$ 10,800
Public Offering
Class of Stock [Line Items]
Number of shares issued or sold (in shares)	4,500,000
Common stock purchase price (in dollars per share)	$ 21.25
Over-allotment option
Class of Stock [Line Items]
Number of shares issued or sold (in shares)	675,000
Common stock purchase price (in dollars per share)	$ 21.25
Public offering and over-allotment option
Class of Stock [Line Items]
Proceeds from issuance of common stock, net of offering costs	$ 103,000