Stockholders' Equity - Stock Options and a Summary of Activity (Details) - $ / shares	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Stockholders' Equity Note [Abstract]
Fair value of options issued (in dollars per share)	$ 2.72	$ 5.59
Exercise price (in dollars per share)	$ 3.63	$ 7.42
Expected life of options (in years)	5 years 9 months 18 days	5 years 9 months 18 days
Risk-free interest rate	2.10%	1.60%
Expected volatility	91.90%	93.30%
Dividend yield	0.00%	0.00%
Number of Options
Outstanding at beginning of period (in shares)	530,734
Granted (in shares)	180,924
Exercised (in shares)	(40,500)
Canceled/forfeited (in shares)	(282,869)
Expired (in shares)	(56,111)
Outstanding at end of period (in shares)	332,178
Vested and expected to vest at period end (in shares)	301,559
Exercisable at period end (in shares)	186,253
Weighted Average Exercise Price Per Share
Outstanding at beginning of period (in dollars per share)	$ 7.48
Granted (in dollars per share)	3.63
Exercised (in dollars per share)	2.30
Canceled/forfeited (in dollars per share)	5.49
Expired (in dollars per share)	10.65
Outstanding at end of period (in dollars per share)	7.17
Vested and expected to vest at period end (in dollars per share)	7.55
Exercisable at period end (in dollars per share)	$ 9.91
Weighted Average Remaining Contractual Life (in years)
Outstanding at end of period	8 years 2 months 12 days
Vested and expected to vest at period end	8 years
Exercisable at period end	7 years 1 month 6 days