Stockholders' Equity - Restricted Stock Units (Details)	3 Months Ended
	Mar. 31, 2018 $ / shares shares
Restricted Stock Units
Outstanding at beginning of period (in shares) | shares	248,512
Granted (in shares) | shares	25,035
Canceled/forfeited (in shares) | shares	(20,523)
Outstanding at end of period (in shares) | shares	253,024
Weighted Average Grant Date Fair Value
Outstanding at beginning of period (in dollars per share) | $ / shares	$ 5.76
Granted (in dollars per share) | $ / shares	2.46
Canceled/forfeited (in dollars per share) | $ / shares	10.09
Outstanding at end of period (in dollars per share) | $ / shares	$ 5.08
Weighted Average Remaining Contractual Life (in years)
Outstanding at end of period	7 years 9 months 18 days
Restricted Stock Units
Restricted Stock Units
Outstanding at beginning of period (in shares) | shares	306,142
Granted (in shares) | shares	421,514
Released (in shares) | shares	(74,655)
Canceled/forfeited (in shares) | shares	(11,571)
Outstanding at end of period (in shares) | shares	641,430
Weighted Average Grant Date Fair Value
Outstanding at beginning of period (in dollars per share) | $ / shares	$ 3.37
Granted (in dollars per share) | $ / shares	2.48
Released (in dollars per share) | $ / shares	4.10
Canceled/forfeited (in dollars per share) | $ / shares	3.80
Outstanding at end of period (in dollars per share) | $ / shares	$ 2.69
Weighted Average Remaining Contractual Life (in years)
Outstanding at end of period	2 years 8 months 12 days