Summary of Significant Accounting Policies (Details) - USD ($) shares in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Summary of Significant Accounting Policies [Abstract]
Foreign exchange gain		$ 100,000	$ 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	$ 5,131,085	24,182,000
Net changes in valuation	(4,438,000)	(19,051,000)
Ending balance	$ 693,457	$ 5,131,085	$ 24,182,000
Antidilutive securities excluded from computation of earning per share amount (in shares)	21.4	17.4	14.7
Recurring [Member]
Fair value measurements by level for assets and liabilities measured at fair value on a recurring basis
Cash equivalents	$ 20,673,000	$ 31,159,000
Short-term investments	35,035,000	45,622,000
Warrant liability	$ (693,000)	(5,131,000)
Minimum [Member]
Property, Plant and Equipment [Line Items]
Useful life	3 years
Maximum [Member]
Property, Plant and Equipment [Line Items]
Useful life	5 years
Level I [Member] | Recurring [Member]
Fair value measurements by level for assets and liabilities measured at fair value on a recurring basis
Cash equivalents	$ 20,673,000	31,159,000
Short-term investments	35,035,000	45,622,000
Warrant liability	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 liability	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 liability	$ (693,000)	$ (5,131,000)