Stockholders' Equity (Details 2) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Number of Options
Stock options outstanding at beginning of period	4,361,606	3,346,066
Granted	635,000	1,697,883	2,056,700
Exercised	(22,373)	(213,048)	(28,467)
Forfeited or expired	(1,215,563)	(469,295)
Stock options outstanding	3,758,670	4,361,606	3,346,066
Vested and expected to vest at end of period	3,625,650	4,101,178
Exercisable at end of period	2,323,528	2,014,021
Weighted Average Exercise Price per Share
Outstanding at beginning of period	$ 5.8	$ 7.10
Granted	2.15	3.32
Exercised	3.35	1.92
Forfeited or expired	8.72	7.86
Outstanding at end of period	4.26	5.8	$ 7.10
Vested and expected to vest at end of period	4.31	5.97
Exercisable at end of period	$ 5.12	$ 8.78
Weighted Average Remaining Contractual Term
Outstanding at beginning of period	4 years 9 months 18 days	4 years 2 months 12 days
Outstanding at end of period	4 years 8 months 12 days	4 years 9 months 18 days
Vested and expected to vest at end of period	4 years 8 months 12 days	4 years 8 months 12 days
Exercisable at end of period	4 years 2 months 12 days	3 years 3 months 18 days
Aggregate Intrinsic Value
Outstanding at beginning of period	$ 37
Exercised	29
Outstanding at end of period	270	$ 37
Vested and expected to vest at end of period	254	35
Exercisable at end of period	$ 47	$ 12