Condensed Consolidated Statements of Stockholders’ Equity - USD ($) $ in Thousands	Common stock Underwritten public offering	Common stock At-the-market offering	Common stock	Additional paid-in capital Underwritten public offering	Additional paid-in capital At-the-market offering	Additional paid-in capital	Accumulated other comprehensive loss	Accumulated deficit	Underwritten public offering	At-the-market offering	Total
Beginning Balance at Dec. 31, 2017			$ 22			$ 210,196		$ (144,352)			$ 65,866
Beginning balance (in shares) at Dec. 31, 2017			21,707,041
Increase (Decrease) in Stockholders' Equity
Exercise of common stock warrants (in shares)			16,718
Exercise of common stock options and vesting restricted stock						684					684
Exercise of common stock options and vesting restricted stock (in shares)			427,651
Sale of common stock, net						(53)					(53)
Stock-based compensation expense						3,393					3,393
Net loss								(22,202)			(22,202)
Ending Balance at Sep. 30, 2018			$ 22			214,220		(166,554)			47,688
Ending Balance (in shares) at Sep. 30, 2018			22,151,410
Beginning Balance at Jun. 30, 2018			$ 22			212,050		(158,897)			53,175
Beginning balance (in shares) at Jun. 30, 2018			21,980,681
Increase (Decrease) in Stockholders' Equity
Exercise of common stock options and vesting restricted stock						303					303
Exercise of common stock options and vesting restricted stock (in shares)			170,729
Stock-based compensation expense						1,867					1,867
Net loss								(7,657)			(7,657)
Ending Balance at Sep. 30, 2018			$ 22			214,220		(166,554)			47,688
Ending Balance (in shares) at Sep. 30, 2018			22,151,410
Beginning Balance at Dec. 31, 2018			$ 22			216,931		(175,888)			41,065
Beginning balance (in shares) at Dec. 31, 2018			22,369,036
Increase (Decrease) in Stockholders' Equity
Exercise of common stock warrants (in shares)			45,690
Exercise of common stock options and vesting restricted stock			$ 1			2,175					2,176
Exercise of common stock options and vesting restricted stock (in shares)			406,246
Sale of common stock, net	$ 3	$ 2		$ 64,526	$ 48,017				$ 64,529	$ 48,019
Sale of common stock, net (in shares)	2,732,673	2,186,163
Issuance of shares for acquisition of Uman						5,467					5,467
Issuance of shares for acquisition of Uman (in shares)			191,152
ESPP stock purchase						799					799
ESPP stock purchase (in shares)			36,753
Stock-based compensation expense						4,713					4,713
Cumulative translation adjustment							$ (1,135)				(1,135)
Net loss								(29,838)			(29,838)
Ending Balance at Sep. 30, 2019			$ 28			342,628	(1,135)	(205,286)			136,235
Ending Balance (in shares) at Sep. 30, 2019			27,967,713
Beginning Balance at Jun. 30, 2019			$ 25			270,136		(195,416)			74,745
Beginning balance (in shares) at Jun. 30, 2019			24,894,019
Increase (Decrease) in Stockholders' Equity
Exercise of common stock warrants (in shares)			45,690
Exercise of common stock options and vesting restricted stock						265					265
Exercise of common stock options and vesting restricted stock (in shares)			87,476
Sale of common stock, net	$ 3			$ 64,526					$ 64,529
Sale of common stock, net (in shares)	2,732,673
Issuance of shares for acquisition of Uman						5,467					5,467
Issuance of shares for acquisition of Uman (in shares)			191,152
ESPP stock purchase						406					406
ESPP stock purchase (in shares)			16,703
Stock-based compensation expense						1,828					1,828
Cumulative translation adjustment							(1,135)				(1,135)
Net loss								(9,870)			(9,870)
Ending Balance at Sep. 30, 2019			$ 28			$ 342,628	$ (1,135)	(205,286)			136,235
Ending Balance (in shares) at Sep. 30, 2019			27,967,713
Increase (Decrease) in Stockholders' Equity
Cumulative-effect adjustment for the adoption of ASC 606								$ 440			$ 440