Shareholders' Equity (Details)								12 Months Ended
	Dec. 23, 2015 USD ($) shares	Dec. 18, 2015 shares	Sep. 17, 2014 USD ($) $ / shares shares	Jul. 09, 2014 USD ($) warrant_holder $ / shares shares	Jan. 21, 2014 USD ($) $ / shares shares	Aug. 16, 2013 USD ($) $ / shares shares	Jun. 16, 2011 USD ($)	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2014 USD ($) $ / shares shares	Jul. 31, 2015 shares
Shareholders' Equity
Number of common shares sold | shares			15,784,313
Offering price (in dollars per share) | $ / shares			$ 2.55
Proceeds from issuance of common stock | $			$ 37,500,000			$ 8,200,000
Number of shares of common stock sold | shares								23,789,000	23,786,000
Underwriter's discount | $			2,400,000
Issuance cost | $			$ 300,000
Series A Convertible Preferred Stock
Shareholders' Equity
Shares issued upon conversion | shares	1,250	1,250
MLV
Shareholders' Equity
Proceeds from issuance of common stock | $								$ 7,100,000	$ 4,800,000
Amount of net capacity remaining on the ATM | $								$ 7,800,000
Lincoln Park
Shareholders' Equity
Proceeds from issuance of common stock | $									$ 3,700,000
Period over which shares of common stock to be purchased					30 months
Floor price for sale of shares of common stock (in dollars per share) (less than) | $ / shares					$ 2.50
Number of shares of common stock sold | shares									935,499
August 2013 warrants
Shareholders' Equity
Number of shares purchased on exercise of warrants | shares				362,500				724,950		226,299
Offering price (in dollars per share) | $ / shares								$ 2.58	$ 3.04
Number of warrant holders | warrant_holder				1
Exercise price of warrants (in dollars per share) | $ / shares				$ 4.80				$ 4.80
Net proceeds from exercise of warrants | $				$ 1,500,000
Maximum | MLV
Shareholders' Equity
Expected proceeds from sale of common stock | $							$ 20,300,000.0
Percentage of gross proceeds payable as commission							3.00%
Maximum | Lincoln Park
Shareholders' Equity
Value of shares of common stock to be sold | $					$ 15,000,000.0
Number of shares of common stock to be purchased in regular purchases | shares					50,000
Number of shares of common stock to be purchased depending upon the closing sale price of the common stock | shares					100,000
Period of business days over which purchase price of shares of common stock will be determined					10 days
Threshold on percentage of outstanding shares of the common stock that can be beneficially owned by counterparty (more than)								9.99%
Value of remaining shares of common stock to be sold | $									$ 11,300,000
Minimum | Lincoln Park
Shareholders' Equity
Threshold closing sale price of the common stock on the date of a regular purchase to trigger purchase of additional amounts as accelerated purchases (in dollars per share) (equals or exceeds) | $ / shares					$ 3.00
Common Stock
Shareholders' Equity
Number of common shares sold | shares						1,500,000.0			18,655,000
Stock issued to underwriter for exercise of over allotment option (in shares) | shares						50,000
Offering price (in dollars per share) | $ / shares						$ 6.00
Shares converted | shares	1,250,000	1,250,000
Shares issued upon conversion | shares								3,000	408,000
Conversion of stock, amount converted | $	$ 3,200,000
Warrants
Shareholders' Equity
Fair market value of the warrants | $						$ 5,900,000
Warrants | Maximum
Shareholders' Equity
Number of shares purchased on exercise of warrants | shares						1,500,000.0