Convertible Senior Secured Notes (Details)		12 Months Ended				32 Months Ended	38 Months Ended
	May 03, 2013 USD ($)	Dec. 31, 2016 USD ($) item $ / shares shares	Dec. 31, 2015 USD ($) shares	Dec. 31, 2014 USD ($)	Dec. 31, 2013 shares	Dec. 31, 2015 USD ($)	Dec. 31, 2016 USD ($) $ / shares shares
Notes payable
Amount issued		$ 4,600,000					$ 4,600,000
Details of Notes reflected in balance sheet
Accretion of debt discount and deferred financing costs		520,000	$ 748,000	$ 2,090,000
Remaining outstanding balance		4,165,000	7,085,000			$ 7,085,000	4,165,000
Loss on extinguishment of debt		671,000	2,338,000	$ 2,592,000
Occurrence of fundamental change
Notes payable
Conversion ratio, principal amount		$ 1,000					$ 1,000
Required notice period for notification of fundamental change		1 day
Redemption price (as a percent)		100.00%
Occurrence of fundamental change | Maximum
Notes payable
Period from notice date within which note holders can exercise their right to exchange the notes		35 days
Occurrence of fundamental change | Minimum
Notes payable
Period from notice date within which note holders can exercise their right to exchange the notes		20 days
Occurrence of make-whole fundamental change
Notes payable
Required notice period for notification of fundamental change		50 days
Company redeems Notes on or after May 1, 2017
Notes payable
Threshold trading days (whether or not consecutive) | item		20
Consecutive trading day period		30 days
Conversion price, per share of Common Stock | $ / shares		$ 7.42					$ 7.42
Redemption price (as a percent)		100.00%
Threshold percentage of common stock price to determine eligibility of conversion		140.00%
7.50% Convertible Senior Secured Notes due 2019
Notes payable
Amount issued	$ 90,000,000
Conversion ratio, principal amount		$ 1,000					$ 1,000
Conversion rate for the Notes (in shares) | shares					188.7059
Conversion price, per share of Common Stock | $ / shares		$ 5.30					$ 5.30
Details of Notes reflected in balance sheet
Gross proceeds						90,000,000
Initial value of interest make-whole derivative reported as debt discount						(9,270,000)
Conversion option reported as debt discount and APIC	900,000					(22,336,000)
Conversion of debt to equity - principal		$ (3,962,000)	(27,500,000)			(81,463,000)	$ (85,400,000)
Conversion of debt to equity - accretion of debt discount and deferred financing costs		764,000	25,003,000			25,003,000	764,000
Accretion of debt discount and deferred financing costs		278,000				5,151,000
Remaining outstanding balance		4,165,000	$ 7,085,000			$ 7,085,000	4,165,000
Unamortized debt issuance costs	$ 2,600,000	$ 30,000					$ 30,000
Shares of common stock issued in conversion of Notes | shares		700,000	5,200,000				16,120,128
Shares of common stock issued in settlement of the interest make-whole provision | shares		24,000	500,000				2,219,908
Loss on extinguishment of debt		$ 700,000	$ 2,300,000
7.50% Convertible Senior Secured Notes due 2019 | Company obtains stockholder approval prior to day before November 1, 2018
Notes payable
Conversion ratio, principal amount		$ 1,000					$ 1,000
Threshold trading days (whether or not consecutive) | item		20
Consecutive trading day period		30 days
Number of trading days prior to a conversion date within which threshold trading days should complete | item		5
Threshold trading days period prior to a conversion date during which principal amount of notes for such trading day was less than 98% of the product of the last reported sale price of common stock | item		5
Consecutive trading day period prior to a conversion date during which principal amount of notes for such trading day was less than 98% of the product of the last reported sale price of common stock		5 days
Maximum ratio of trading price for each day in measurement period to last reported sales price of Company's stock on each day of measurement period (as a percent)					98.00%
7.50% Convertible Senior Secured Notes due 2019 | Company calls Notes for redemption prior to day before redemption date and Note holder converts on or after November 1, 2018
Notes payable
Conversion ratio, principal amount		$ 1,000					1,000
7.50% Convertible Senior Secured Notes due 2019 | On or after November 1, 2013, Company makes interest make-whole payments
Notes payable
Conversion ratio, principal amount		$ 1,000					$ 1,000
Threshold trading days (whether or not consecutive) | item		20
Consecutive trading day period		30 days
Number of trading days prior to a conversion date within which threshold trading days should complete | item		5
Discount rate (as a percent)		2.00%
Stock value as percentage of simple average of the daily volume-weighted average price if the company elects to pay an interest make-whole payment in common stock		95.00%					95.00%
Number of trading days ending on and including the trading day immediately preceding the conversion date use to determine daily volume weighted average price | item		10
7.50% Convertible Senior Secured Notes due 2019 | On or after November 1, 2013, Company makes interest make-whole payments | Maximum
Notes payable
Conversion rate for the Notes (in shares) | shares		221.7294