Stock-based Compensation, Option Plans and Warrants (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		12 Months Ended
	Jan. 31, 2017	May 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense			$ 3,238	$ 3,194	$ 3,912
Director Stock Awards [Abstract]
Shares reserved for issuance (in shares)			11,921,506
Warrants [Abstract]
Stock issuance (in shares)	28,800,000	28,800,000
Proceeds from issuance of common stock, net of offering costs of $1.6 million and $3.8 million, respectively	$ 65,200	$ 27,200	$ 65,224	$ 27,135	$ 0
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options outstanding, Number (in shares)			8,317,416
Exercisable, Number (in shares)			5,983,678
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred Compensation Arrangement with Individual, Common Stock Reserved for Future Issuance			12,600,000
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Forfeiture Rate			2.00%	4.00%	5.00%
Stock-based compensation expense			$ 1,800	$ 2,000	$ 2,400
Weighted average assumptions used in fair value of the options [Abstract]
Weighted average value per option granted during the period (in dollars per share)			$ 1.81	$ 0.68	$ 2.37
Assumptions [Abstract]
Expected dividend yield (in hundredths)			0.00%	0.00%	0.00%
Volatility (in hundredths)			67.60%	71.10%	81.10%
Risk free interest rate (in hundredths)			2.16%	1.72%	1.92%
Expected life (years)			6 years 10 months 24 days	7 years	7 years
Fair value of options granted			$ 574	$ 2,307	$ 3,792
Options expiration period			10 years
Options [Roll Forward]
Options outstanding, beginning balance (in shares)	8,154,000		8,154,000	6,808,000	5,885,000
Granted (in shares)			317,000	2,265,000	1,601,000
Exercised (in shares)			(5,000)	(83,000)	(164,000)
Forfeited/Expired (in shares)			(149,000)	(836,000)	(514,000)
Options outstanding, ending balance (in shares)			8,317,000	8,154,000	6,808,000
Exercisable at end of year (in shares)			5,984,000
Weighted average exercise price [Roll Forward]
Options outstanding, beginning balance (in dollars per share)	$ 2.39		$ 2.39	$ 2.89	$ 2.88
Granted (in dollars per share)			1.81	1.02	3.22
Exercised (in dollars per share)			0.97	1.40	1.03
Forfeited/Expired (in dollars per share)			3.58	2.84	4.36
Options outstanding, ending balance (in dollars per share)			$ 2.35	2.39	2.89
Options outstanding weighted average exercise price of options exercisable
Weighted average remaining life [Abstract]
Options outstanding ending balance			5 years 9 months 18 days
Exercisable at end of year			4 years 11 months 8 days
Fair value per share [Abstract]
Options outstanding, ending balance (in dollars per share)				1.67
Exercisable at end of year, Fair value (in dollars per share)				1.83
Other information pertaining to stock options activity [Abstract]
Weighted average grant date fair value of stock options granted (in dollars per share)			$ 1.81	$ 0.68	$ 2.37
Total fair value of options vested			$ 2,795	$ 2,776	$ 2,035
Total intrinsic value of options exercised			5	39	124
Compensation cost related to non-vested awards not yet recognized			1,600
Restricted Unit Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense			1,400	$ 1,200	$ 1,500
Restricted Stock Awards [Abstract]
Compensation cost not yet recognized			$ 700
Number of Shares [Roll Forward]
Unvested, Beginning balance (in shares)	1,492,465		1,492,465	1,643,284	1,776,090
Granted (in shares)			44,000	0	0
Vested/Released (in shares)			(56,340)	(52,017)	(127,729)
Forfeited (in shares)			(750)	(98,802)	(5,077)
Unvested, Ending balance (in shares)			1,479,375	1,492,465	1,643,284
Weighted average grant date fair value [Roll Forward]
Unvested, beginning balance (in dollars per share)	$ 3.47		$ 3.47	$ 3.44	$ 3.43
Granted (in dollars per share)			1.75	0.00	0.00
Vested/Released (in dollars per share)			3.14	2.40	3.38
Forfeited (in dollars per share)			2.63	3.63	2.56
Unvested, Ending balance (in dollars per share)			$ 3.43	$ 3.47	$ 3.44
2005 Directors Plan [Member]
Director Stock Awards [Abstract]
Shares reserved for issuance (in shares)			2,900,000
Number of shares to be granted for participation in board and committee meetings as per agreement (in shares)			25,000
Maximum shares that can be awarded to one person (in shares)			100,000
Percentage of exercise price awarded (in hundredths)			100.00%
0.97 - 1.99
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Stock option plans exercise price range, lower range limit (in dollars per share)			$ 0.97
Stock option plans exercise price range, upper limit (in dollars per share)			$ 1.99
Options outstanding, Number (in shares)			3,770,542
Options outstanding, Weighted average remaining life			6 years
Options outstanding, Weighted average exercise price (in dollars per share)			$ 1.28
Exercisable, Number (in shares)			2,257,292
Exercisable, Weighted average remaining life			4 years 6 months
Exercisable, Weighted average exercise price (in dollars per share)			$ 1.44
2.00 - 2.99
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Stock option plans exercise price range, lower range limit (in dollars per share)			2.00
Stock option plans exercise price range, upper limit (in dollars per share)			$ 2.99
Options outstanding, Number (in shares)			1,243,725
Options outstanding, Weighted average remaining life			4 years 2 months 12 days
Options outstanding, Weighted average exercise price (in dollars per share)			$ 2.35
Exercisable, Number (in shares)			1,239,225
Exercisable, Weighted average remaining life			4 years 2 months 12 days
Exercisable, Weighted average exercise price (in dollars per share)			$ 2.35
3.00 - 3.99
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Stock option plans exercise price range, lower range limit (in dollars per share)			3.00
Stock option plans exercise price range, upper limit (in dollars per share)			$ 3.99
Options outstanding, Number (in shares)			2,617,399
Options outstanding, Weighted average remaining life			6 years 4 months 24 days
Options outstanding, Weighted average exercise price (in dollars per share)			$ 3.27
Exercisable, Number (in shares)			1,807,911
Exercisable, Weighted average remaining life			6 years 2 months 12 days
Exercisable, Weighted average exercise price (in dollars per share)			$ 3.33
4.00 - 4.99
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Stock option plans exercise price range, lower range limit (in dollars per share)			4.00
Stock option plans exercise price range, upper limit (in dollars per share)			$ 4.99
Options outstanding, Number (in shares)			585,750
Options outstanding, Weighted average remaining life			4 years 2 months 12 days
Options outstanding, Weighted average exercise price (in dollars per share)			$ 4.56
Exercisable, Number (in shares)			580,250
Exercisable, Weighted average remaining life			4 years 1 month 6 days
Exercisable, Weighted average exercise price (in dollars per share)			$ 4.56
5.00 - 5.99
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Stock option plans exercise price range, lower range limit (in dollars per share)			5.00
Stock option plans exercise price range, upper limit (in dollars per share)			$ 5.99
Options outstanding, Number (in shares)			99,000
Options outstanding, Weighted average remaining life			6 years 4 months 24 days
Options outstanding, Weighted average exercise price (in dollars per share)			$ 5.39
Exercisable, Number (in shares)			98,250
Exercisable, Weighted average remaining life			6 years 4 months 24 days
Exercisable, Weighted average exercise price (in dollars per share)			$ 5.38
6.00 - 6.28
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Stock option plans exercise price range, lower range limit (in dollars per share)			6.00
Stock option plans exercise price range, upper limit (in dollars per share)			$ 6.28
Options outstanding, Number (in shares)			1,000
Options outstanding, Weighted average remaining life			6 years 6 months
Options outstanding, Weighted average exercise price (in dollars per share)			$ 6.28
Exercisable, Number (in shares)			750
Exercisable, Weighted average remaining life			6 years 6 months
Exercisable, Weighted average exercise price (in dollars per share)			$ 6.28