Stock-Based Compensation - Non-vested Stock Option Activity (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Number of Options
Outstanding at beginning of year (in shares)	1,039,750	1,191,125	1,546,500
Granted (in shares)	176,000	81,000	126,000
Outstanding at end of year (in shares)	1,116,750	1,039,750	1,191,125
Weighted- Average Exercise Price
Granted (in dollars per share)	$ 0.68	$ 1.11	$ 1.54
Non-Vested Stock Options
Number of Options
Outstanding at beginning of year (in shares)	0
Granted (in shares)	176,000
Vested (in shares)	(176,000)
Forfeited (in shares)	0
Outstanding at end of year (in shares)	0	0
Weighted- Average Exercise Price
Outstanding at beginning of year (in dollars per share)	$ 0.00
Granted (in dollars per share)	0.68
Vested (in dollars per share)	0.68
Forfeited (in dollars per share)	0.00
Outstanding at end of year (in dollars per share)	$ 0.00	$ 0.00