Stock-Based Compensation, Summary of Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation [Abstract]
Per share market price of common stock on last trading day of year (in dollars per share)	$ 2.40
Proceeds from exercise of options	$ 135	$ 22	$ 20
Stock Options [Member]
Options, number of shares [Roll Forward]
Outstanding, beginning of period (in shares)	5,138,066	5,378,571	4,999,928
Options granted (in shares)	1,095,000	1,613,500	429,000
Options exercised (in shares)	(117,229)	(12,500)	(50,357)
Options cancelled (in shares)	(117,000)	(1,841,505)
Outstanding, end of period (in shares)	5,998,837	5,138,066	5,378,571
Options exercisable, end of period (in shares)	3,855,119
Options, weighted average exercise price [Roll Forward]
Outstanding, beginning of period (in dollars per share)	$ 8.41	$ 8.52	$ 8.76
Options granted (in dollars per share)	3.52	4.06	4.77
Options exercised (in dollars per share)	1.15	1.74	0.40
Options cancelled (in dollars per share)	5.34	4.71
Outstanding, end of period (in dollars per share)	7.72	$ 8.41	$ 8.52
Options exercisable, end of period (in dollars per share)	$ 9.87
Options, additional disclosures [Abstract]
Options outstanding, weighted average remaining contractual life	6 years 1 month 28 days
Options exercisable, weighted average remaining contractual life	4 years 8 months 26 days
Options outstanding, aggregate intrinsic value	$ 810
Options exercisable, aggregate intrinsic value	809
Share-based Compensation [Abstract]
Proceeds from exercise of options	135	$ 22	$ 20
Total intrinsic value of options exercised	$ 46	$ 25	$ 91
Restricted Stock Units (RSUs) [Member]
RSUs, number of RSUs [Roll Forward]
Outstanding, beginning of period (in shares)	469,661	423,435	359,956
RSUs granted (in shares)	246,663	220,664	219,331
RSUs vested (in shares)	(211,330)	(174,438)	(155,852)
Outstanding, end of period (in shares)	504,994	469,661	423,435
RSUs, weighted average grant date fair value [Abstract]
Outstanding, beginning of period (in dollars per share)	$ 5.19	$ 8.08	$ 13.22
RSUs granted (in dollars per share)	3.26	3.83	4.75
RSUs vested (in dollars per share)	6.19	10.47	15.27
Outstanding, end of period (in dollars per share)	$ 3.83	$ 5.19	$ 8.08
RSUs, aggregate intrinsic value [Abstract]
Outstanding, end of period	$ 0	$ 0	$ 0	$ 0