Stock-Based Compensation - Restricted Stock (Details) - 2008 Plan - Restricted stock	12 Months Ended
	Dec. 31, 2017 $ / shares shares
Shares
Outstanding and unvested at the beginning of the period (in shares) | shares	50,000
Granted (in shares) | shares	70,000
Vested (in shares) | shares	(16,665)
Canceled (in shares) | shares	(6,667)
Outstanding and unvested at the end of the period (in shares) | shares	96,668
Weighted Average Grant Date Fair Value (per share)
Outstanding and unvested at the beginning of the period (in dollars per share) | $ / shares	$ 4.72
Granted (in dollars per share) | $ / shares	2.32
Vested (in dollars per share) | $ / shares	4.72
Canceled (in dollars per share) | $ / shares	4.72
Outstanding and unvested at the end of the period (in dollars per share) | $ / shares	$ 2.98