CONDESNSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS EQUITY (unaudited) - USD ($) $ in Thousands	Total	Common Stock	Treasury Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Loss
Beginning balance at Dec. 31, 2017	$ 140,063	$ 60	$ (3)	$ 305,676	$ (163,135)	$ (2,535)
Beginning balance (in shares) at Dec. 31, 2017		59,663,969	(2,587,535)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued upon exercise of stock options	5,440	$ 0		5,440
Common stock issued upon exercise of stock options (in shares)		644,830
Common stock issued upon vesting of restricted stock units	0
Common stock issued upon vesting of restricted stock units (in shares)		103,339
Stock-based compensation	2,437			2,437
Common stock issued under Employee Stock Purchase Plan	490			490
Common stock issued under Employee Stock Purchase Plan (in shares)		39,888
Common stock repurchase	(1,345)			(1,345)
Common stock repurchase (in shares)			(93,750)
Issuance of common stock in connection with acquisitions	1,000			1,000
ASC 606 prior period adjustment (see note 1)	676				676
Issuance of common stock in connection with acquisitions (in shares)		85,681
Net loss	(3,203)				(3,203)
Other comprehensive income	559					559
Ending balance at Mar. 31, 2018	146,117	$ 60	$ (3)	313,698	(165,662)	(1,976)
Ending balance (in shares) at Mar. 31, 2018		60,537,707	(2,681,285)
Beginning balance at Dec. 31, 2018	170,729	$ 64	$ (3)	362,590	(187,491)	(4,431)
Beginning balance (in shares) at Dec. 31, 2018		63,676,229	(2,681,285)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued upon exercise of stock options	$ 6,477	$ 1		6,476
Common stock issued upon exercise of stock options (in shares)	626,000	626,478
Common stock issued upon vesting of restricted stock units	$ 0
Common stock issued upon vesting of restricted stock units (in shares)		414,742
Stock-based compensation	5,188			5,188
Common stock issued under Employee Stock Purchase Plan	721			721
Common stock issued under Employee Stock Purchase Plan (in shares)		30,349
Common stock repurchase	(709)			(709)
Common stock repurchase (in shares)			(23,421)
Issuance of debt conversion option	52,900			52,900
Debt conversion option issuance costs	(1,986)			(1,986)
Capped call option issuance costs	(23,184)			(23,184)
Net loss	(18,890)				(18,890)
Other comprehensive income	(207)					(207)
Ending balance at Mar. 31, 2019	$ 191,039	$ 65	$ (3)	$ 401,996	$ (206,381)	$ (4,638)
Ending balance (in shares) at Mar. 31, 2019		64,747,798	(2,704,706)