Stockholders' Equity - Stock Option Activity (Details)	6 Months Ended
	Jun. 30, 2017 USD ($) $ / shares shares
Number of shares
Beginning balance outstanding (in shares) | shares	1,772,050
Granted (in shares) | shares	515,073
Exercised (in shares) | shares	(56,955)
Forfeited (in shares) | shares	(44,560)
Expired (in shares) | shares	(16,068)
Ending balance outstanding (in shares) | shares	2,169,540
Vested and expected to vest (in shares) | shares	2,163,371
Exercisable (in shares) | shares	1,095,905
Weighted average exercise price
Beginning balance outstanding (in dollars per share) | $ / shares	$ 5.74
Granted (in dollars per share) | $ / shares	4.83
Exercised (in dollars per share) | $ / shares	3.86
Forfeited (in dollars per share) | $ / shares	7.05
Expired (in dollars per share) | $ / shares	8.35
Ending balance outstanding (in dollars per share) | $ / shares	5.52
Vested and expected to vest (in dollars per share) | $ / shares	5.54
Exercisable (in dollars per share) | $ / shares	$ 4.41
Weighted average contractual term
Outstanding (in years)	8 years 4 months 24 days
Vested and expected to vest (in years)	8 years 4 months 24 days
Exercisable (in years)	7 years 9 months 18 days
Aggregate intrinsic value
Outstanding (in dollars) | $	$ 2,289,662
Vested and expected to vest (in dollars) | $	2,263,752
Exercisable (in dollars) | $	$ 1,994,814