Shareholders' Equity (Details)								3 Months Ended	12 Months Ended
	Dec. 21, 2016 USD ($) $ / shares shares	Nov. 22, 2016 shares	Oct. 10, 2016 USD ($)	Dec. 23, 2015 USD ($) shares	Dec. 18, 2015 shares	Jul. 09, 2014 USD ($) warrant_holder $ / shares shares	Jan. 21, 2014 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2014 shares	Sep. 09, 2016 $ / shares	Dec. 31, 2015 $ / shares shares	Aug. 31, 2013 $ / shares shares
Shareholders' Equity
Number of shares of common stock sold (in shares)								31,595,000	31,595,000			23,789,000
Proceeds from issuance of common stock | $	$ 18,000,000
Number of common shares sold (in shares)	7,130,000
Offering price (in dollars per share) | $ / shares	$ 2.75
Underwriter's discount | $	$ 1,400,000
Issuance cost | $	$ 200,000
Series A Convertible Preferred Stock
Shareholders' Equity
Shares issued upon conversion (in shares)				1,250	1,250
Common Stock
Shareholders' Equity
Number of common shares sold (in shares)									7,538,000	18,655,000
Shares converted (in shares)				1,250,000	1,250,000
Shares issued upon conversion (in shares)										408,000
Conversion of stock, amount converted | $				$ 3,200,000
Preferred Stock
Shareholders' Equity
Shares converted (in shares)		1,250,000		1,250,000
Lincoln Park
Shareholders' Equity
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 (in shares)								985,499	985,499
Proceeds from issuance of common stock | $									$ 3,900,000
Cowen and Company, LLC
Shareholders' Equity
At-the-market sales agreement, maximum aggregate proceeds | $			$ 25,000,000.0
At-the-market-sales agreement, proceeds from issuance of common stock | $								$ 800,000
Amount of net capacity remaining on the ATM | $								$ 24,200,000	$ 24,200,000
Cowen and Company, LLC | Common Stock
Shareholders' Equity
At-the-market sales agreement, shares issued (in shares)								357,856
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							50,000
Number of shares of common stock to be purchased depending upon the closing sale price of the common stock (in 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									9.99%
Maximum | Cowen and Company, LLC
Shareholders' Equity
Percentage of gross proceeds payable as commission			3.00%
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
August 2013 warrants
Shareholders' Equity
Number of warrant holders (in holders) | warrant_holder						1
Number of shares purchased on exercise of warrants (in shares)						362,500							724,950
Exercise price of warrants (in dollars per share) | $ / shares						$ 4.80							$ 4.80
Net proceeds from exercise of warrants | $						$ 1,500,000
Offering price (in dollars per share) | $ / shares								$ 3	$ 3		$ 2.20	$ 2.58