Stock-Based Compensation - Restricted Stock Units (Details) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($) $ / shares shares
Weighted Average Exercise Price Per Share
Unrecognized stock-based compensation expense | $	$ 5.8
Unrecognized compensation expense, weighted-average period expected to be recognized	2 years 10 months 24 days
Restricted stock units
Number of Restricted Stock Units
Balance, beginning of period | shares	93,560
Granted | shares	92,000
Vested | shares	(9,902)
Cancelled/forfeited | shares	(7,250)
Balance, end of period | shares	168,408
Weighted Average Exercise Price Per Share
Balance, beginning of period (price per share) | $ / shares	$ 8.38
Granted (price per share) | $ / shares	6.57
Vested (price per share) | $ / shares	8.93
Cancelled/forfeited (price per share) | $ / shares	8.22
Balance, end of period (price per share) | $ / shares	$ 7.36
2016 Employee Incentive Plan | Restricted stock units
Weighted Average Exercise Price Per Share
Unrecognized stock-based compensation expense | $	$ 1.1
Unrecognized compensation expense, weighted-average period expected to be recognized	3 years 2 months 12 days