Share-Based Compensation - Activity (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) $ / shares shares
Number of Options
Outstanding at beginning of year (in shares) | shares	1,412,940
Granted (in shares) | shares	219,130
Expired/canceled/forfeited (in shares) | shares	(23,424)
Exercised (in shares) | shares	0
Outstanding at end of year (in shares) | shares	1,608,646
Wgtd. Avg. Exercise Price
Outstanding at beginning of year (in dollars per share) | $ / shares	$ 7.13
Granted (in dollars per share) | $ / shares	1.85
Expired/canceled/forfeited (in dollars per share) | $ / shares	21.49
Exercised (in dollars per share) | $ / shares
Outstanding at end of year (in dollars per share) | $ / shares	$ 6.20
Additional Disclosures
Options exercisable at end of year (in shares) | shares	705,594
Options expected to vest (in shares) | shares	1,563,493
Options exercisable at end of year (usd per share) | $ / shares	$ 10.34
Options expected to vest (usd per share) | $ / shares	$ 6.29
Outstanding, remaining contractual term	8 years 29 days
Exercisable, remaining contractual term	7 years
Vested and expected to vest, remaining contractual term	8 years 22 days
Outstanding, intrinsic value | $	$ 9
Exercisable, intrinsic value | $	0
Vested and expected to vest, intrinsic value | $	$ 8