Summary of Significant Accounting Policies (Details) (USD $)	12 Months Ended
	Dec. 31, 2014 item	Dec. 31, 2013	Dec. 31, 2012	Jun. 19, 2013
Summary of Significant Accounting Policies
Realized gains or losses from sale of marketable securities	$ 0	$ 2,700	$ 0
Restricted cash current, standby letters of credit	200,000	200,000
Property and equipment, estimated useful lives	3 years
Intangible asset, amortization expense			111,000
Reclassification of preferred stock warrants liability to additional paid-in capital	157,000	157,000
Issuance of warrant to purchase shares of common stock	38,997
Exercise price of warrants issued (in dollars per share)	5.13
Number of operating segments	1
Loan and Security Agreement [Member]
Summary of Significant Accounting Policies
Exercise price of warrants issued (in dollars per share)	12.11			12.11
Loan and Security Agreement [Member] | Maximum [Member]
Summary of Significant Accounting Policies
Issuance of warrant to purchase shares of common stock	49,548			49,548
Warrant [Member] | Loan and Security Agreement [Member]
Summary of Significant Accounting Policies
Fair value of warrants issued	$ 130,000