Accounting Policies and Recent Accounting Pronouncements (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014 Segment	Dec. 31, 2013	Dec. 31, 2012
Restricted Cash [Abstract]
Restricted cash	$ 225,000								$ 225,000
Decrease in restricted cash									100,000
Long-lived assets [Abstract]
Impairment of long-lived assets									0	0	0
Numerator [Abstract]
Net loss as reported	(10,635,000)	(11,324,000)	(10,623,000)	(11,476,000)	(11,729,000)	(12,224,000)	(8,627,000)	(12,635,000)	(44,058,000)	(45,215,000)	(37,315,000)
Less: income from change in fair value of warrant liability									(3,791,000)	0	0
Numerator for diluted net loss per common share									$ (47,849,000)	$ (45,215,000)	$ (37,315,000)
Denominator [Abstract]
Basic weighted average common shares outstanding (in shares)	85,358,000	85,209,000	85,061,000	84,728,000	73,129,000	54,792,000	49,135,000	43,657,000	85,095,000	55,258,000	39,396,000
Dilutive common shares from assumed warrant exercises (in shares)									930,000	0	0
Diluted weighted average common shares outstanding (in shares)	85,560,000	85,209,000	85,882,000	84,728,000	73,129,000	54,792,000	49,866,000	43,657,000	86,025,000	55,258,000	39,396,000
Number of shares of common stock potentially issuable exercise of certain stock options and warrants (in shares)									22,000,000	20,200,000	11,900,000
Potential common stock issuable upon exercise of stock options and warrants (in shares)									17,400,000	15,400,000	7,000,000
Business segments [Abstract]
Number of operating segments									1
Minimum [Member]
Property and equipment [Line Items]
Estimated useful life of property and equipment									3 years
Maximum [Member]
Property and equipment [Line Items]
Estimated useful life of property and equipment									10 years