Stock Option Plan - Summary of stock-based compensation activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Number of Stock Options Outstanding
Balance, January 1, 2016	1,909,911
Granted	160,000
Exercised
Forfeited/Cancelled
Balance, March 31, 2016	2,069,911	1,909,911
Exercisable	1,518,909
Weighted Average Exercise Price
Balance	$ 2.58
Granted	$ 2.23
Exercised
Forfeited/Cancelled
Balance	$ 2.58	$ 2.58
Exercisable	$ 2.61
Weighted Average Remaining Contractual Term, Options Outstanding (in years)	8 years 5 months 5 days	8 years 6 months 22 days
Weighted Average Remaining Contractual Term, Options Exercisable (in years)	8 years 1 month 10 days
Aggregate Intrinsic Value, Options Outstanding	$ 515	$ 813
Aggregate Intrinsic Value, Options Exercisable	$ 510