Capital Stock - Textual (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	9 Months Ended
	Apr. 30, 2018	Sep. 30, 2018	Sep. 30, 2017
Class of Stock [Line Items]
Stock options exercised (shares)		729,596	63,509
Weighted average exercise price of stock options exercised (usd per share)		$ 5.92	$ 2.76
Proceeds from exercises of stock options		$ 4,319	$ 175
Public offering price (usd per share)	$ 9.25
Proceeds from issuance of common stock, net of costs	$ 37,300
Underwritten Public Offering [Member]
Class of Stock [Line Items]
Issuance of common stock, net of issuance costs (shares)	4,312,500
Over-Allotment Option [Member]
Class of Stock [Line Items]
Issuance of common stock, net of issuance costs (shares)	562,500