CONSOLIDATED STATEMENT OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Follow On Public Offering [Member]
Offering costs incurred	$ 6,492
IPO
Offering costs incurred		$ 2,272
Private Placement [Member]
Offering costs incurred	$ 1,453
Series B convertible preferred stock
Temporary equity, issuance costs			$ 60
Series C convertible preferred stock
Temporary equity, issuance costs		$ 136