Summary of Significant Accounting Policies (Details) (USD $) Share data in Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Summary of Significant Accounting Policies [Abstract]
Reverse stock split conversation ratio	1-for-7
Foreign exchange gain	$ 100,000	$ 200,000
Sub lease revenue			200,000
Maximum maturity of highly liquid debt instrument	90 days
Maximum maturity to be considered as available for sale	12 months
Changes in carrying amounts of warrant liabilities [Abstract]
Beginning balance	24,182,324	3,972,000
Net changes in valuation	(19,051,000)	20,210,000
Ending balance	5,131,085	24,182,324	3,972,000
Antidilutive securities excluded from computation of earning per share amount (in shares)	17.4	14.7	11.0
Shares reserved for future issuance (in shares)	0.7
Recurring [Member]
Fair value measurements by level for assets and liabilities measured at fair value on a recurring basis
Cash equivalents	31,159,000	10,281,000
Short-term investments	45,622,000	27,085,000
Warrant liabilities	(5,131,000)	(24,182,000)
Level I [Member] | Recurring [Member]
Fair value measurements by level for assets and liabilities measured at fair value on a recurring basis
Cash equivalents	31,159,000	10,281,000
Short-term investments	45,622,000	27,085,000
Warrant liabilities	0	0
Level II [Member] | Recurring [Member]
Fair value measurements by level for assets and liabilities measured at fair value on a recurring basis
Cash equivalents	0	0
Short-term investments	0	0
Warrant liabilities	0	0
Level III [Member] | Recurring [Member]
Fair value measurements by level for assets and liabilities measured at fair value on a recurring basis
Cash equivalents	0	0
Short-term investments	0	0
Warrant liabilities	$ (5,131,000)	$ (24,182,000)
Minimum [Member]
Property, Plant and Equipment [Line Items]
Useful life	3 years
Maximum [Member]
Property, Plant and Equipment [Line Items]
Useful life	5 years