Consolidated Statements of Changes in Stockholders' Equity (Deficit) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)
Beginning balance at Dec. 31, 2013	$ (67,028)	$ 3	$ 119,481	$ (186,512)
Beginning balance, shares at Dec. 31, 2013		3,224
Common stock issued in connection with early stock option exercises, shares		231
Common stock issued in connection with all other stock option exercises	332	$ 1	331
Common stock issued in connection with all other stock option exercises, shares		275
Vesting of early exercised stock options	54		54
Common stock repurchased, shares		(2)
Stock-based compensation	1,175		1,175
Accretion of preferred stock	(11,301)		(11,301)
Net income (loss)	297			297
Ending balance at Dec. 31, 2014	(76,471)	$ 4	109,740	(186,215)
Ending balance, shares at Dec. 31, 2014		3,728
Common stock issued in connection with early stock option exercises, shares		2
Common stock issued in connection with all other stock option exercises	530		530
Common stock issued in connection with all other stock option exercises, shares		654
Vesting of early exercised stock options	119		119
Common stock repurchased, shares		(2)
Stock-based compensation	1,188		1,188
Accretion of preferred stock	(11,301)		(11,301)
Net income (loss)	900			900
Ending balance at Dec. 31, 2015	(85,035)	$ 4	100,276	(185,315)
Ending balance, shares at Dec. 31, 2015		4,382
Common stock issued in connection with early stock option exercises, shares		59
Common stock issued in connection with all other stock option exercises	$ 286		286
Common stock issued in connection with all other stock option exercises, shares	196	138
Vesting of early exercised stock options	$ 167		167
Stock-based compensation	2,765		2,765
Accretion of preferred stock	(6,258)		(6,258)
Conversion of Preferred Stock Warrants Into Common Stock Warrants Initial Public Offering	505		505
Common Stock Issued in Connection with Net Exercises of Common Stock Warrants		55
Conversion of preferred stock into common stock at initial public offering	106,084	$ 9	106,075
Conversion of preferred stock into common stock at initial public offering, shares		8,655
Issuance of common stock from initial public offering, net of issuance costs	107,192	$ 7	107,185
Issuance of common stock from initial public offering, net of issuance costs, shares		7,047
Net cumulative effect adjustment upon adoption of share-based payment guidance to account for forfeitures as they occur			215	(215)
Net income (loss)	(1,673)			(1,673)
Other comprehensive income (loss)	(10)				$ (10)
Ending balance at Dec. 31, 2016	$ 124,023	$ 20	$ 311,216	$ (187,203)	$ (10)
Ending balance, shares at Dec. 31, 2016		20,336