Convertible Debentures (Details) $ / shares in Units, $ in Thousands				12 Months Ended
	Sep. 14, 2017 shares	Jun. 06, 2017 shares $ / shares	Jul. 21, 2014 USD ($) shares $ / shares	Dec. 31, 2017 USD ($) shares $ / shares	Dec. 31, 2016 USD ($) $ / shares	Sep. 13, 2017 USD ($)
Debt Instrument [Line Items]
Total convertible debt				$ 0	$ 12,028
Common stock, par value (in dollars per share) | $ / shares				$ 0.001	$ 0.001
Change in fair value of warrant liability				$ (102)	$ (5,396)
Debentures converted in shares of common stock, value				262	265
Loss on extinguishment of debentures				$ (11,799)	0
Preferred stock, par value (in dollars per share) | $ / shares				$ 0.10
Interest expense related to convertible debenture				$ 3,117	$ 3,525
Series C Convertible Preferred Stock [Member]
Debt Instrument [Line Items]
Aggregate principal amount of debt						$ 40,465
Number of shares debt convertible (in shares) | shares				15,049,000
Senior secured convertible debentures conversion price (in dollars per share) | $ / shares				$ 2.69
Beneficial ownership percentage				9.99%
Preferred stock, par value (in dollars per share) | $ / shares				$ 0.10	$ 0.10
Senior Secured 2.25% Convertible Debentures [Member]
Debt Instrument [Line Items]
Total convertible debt					$ 7,174
Debt instrument, unamortized discount					24,314
Deferred financing costs					524
Interest rate				2.25%
Aggregate principal amount of debt				$ 32,500
Number of shares debt convertible (in shares) | shares				8,666,668
Senior secured convertible debentures conversion price (in dollars per share) | $ / shares				$ 3.75
Maturity period				5 years
Maturity date				Jun. 30, 2021
Debt instrument, convertible, beneficial conversion feature				$ 27,300
Senior Secured 2.25% Convertible Debentures [Member] | Minimum [Member]
Debt Instrument [Line Items]
Senior secured convertible debentures conversion price (in dollars per share) | $ / shares				$ 3.75
Senior Secured 2.25% Convertible Debentures [Member] | Maximum [Member]
Debt Instrument [Line Items]
Senior secured convertible debentures conversion price (in dollars per share) | $ / shares				$ 6.90
Senior Secured 4% Convertible Debentures [Member]
Debt Instrument [Line Items]
Total convertible debt					4,854
Debt instrument, unamortized discount			$ 10,353		3,469
Deferred financing costs					$ 392
Interest rate		4.00%		4.00%
Aggregate principal amount of debt			$ 15,000	$ 15,000
Number of shares debt convertible (in shares) | shares			1,169,595
Senior secured convertible debentures conversion price (in dollars per share) | $ / shares			$ 12.825
Maturity period				5 years
Maturity date				Jun. 30, 2021
Debt instrument, convertible, beneficial conversion feature			$ 4,565
Fair value of warrants			5,296
Change in fair value of warrant liability			491
Debt instrument initial carrying amount			$ 4,647
Debentures converted in shares of common stock, value				$ 262
Debt conversion, converted instrument, issued (in shares) | shares				70,000
Interest expense on debt				$ 197
Senior Secured 4% Convertible Debentures [Member] | Series A Warrants [Member]
Debt Instrument [Line Items]
Number of warrants to purchase common stock (in shares) | shares			1,239,769
Exercise price of warrants (in dollars per share) | $ / shares			$ 12.25
Common stock, par value (in dollars per share) | $ / shares			$ 0.001
Warrants expiration date				Jul. 31, 2019
Senior Secured 2.25% Convertible Debentures and Senior Secured 4% Convertible Debentures [Member] | Series C Convertible Preferred Stock [Member]
Debt Instrument [Line Items]
Number of shares debt convertible (in shares) | shares		15,049,000
Senior secured convertible debentures conversion price (in dollars per share) | $ / shares		$ 2.69
Debt conversion, converted instrument, issued (in shares) | shares	40,482
Preferred stock, par value (in dollars per share) | $ / shares		$ 1,000		$ 1,000
Each share of preferred stock to common stock (in shares) | shares		372
Senior Secured 2.25% Convertible Debentures and Senior Secured 4% Convertible Debentures [Member] | Series C Convertible Preferred Stock [Member] | Maximum [Member]
Debt Instrument [Line Items]
Beneficial ownership percentage		9.99%