Quarterly report pursuant to Section 13 or 15(d)

Offerings of Common Stock and Warrants and At-the-Market Offering Program (Details)

Offerings of Common Stock and Warrants and At-the-Market Offering Program (Details) $ / shares in Units, $ in Thousands						3 Months Ended	5 Months Ended	9 Months Ended		12 Months Ended
	Oct. 21, 2016 USD ($)	Oct. 18, 2016 $ / shares shares	Apr. 22, 2016 USD ($) shares	Apr. 19, 2016 $ / shares shares	Aug. 28, 2015 USD ($)	Dec. 31, 2016 shares	Sep. 30, 2016 shares	Dec. 31, 2016 USD ($) shares	Dec. 31, 2015 USD ($)	Mar. 31, 2016 USD ($) shares
Number of common stock shares available to accredited investors		3,600,000
Share price of common stock sold (in dollars per share) \| $ / shares		$ 1.20
Net proceeds from offering of common stock and warrants \| $	$ 6,800		$ 13,100					$ 19,886	$ 7,412
Number of common stock shares available in public offering				2,700,000
Beneficial ownership of common stock resulting from purchase of stock in public offering (as a percent)				4.99
Number of warrants or shares of common stock to be sold to purchase common stock				2
Common stock sold (in shares)										6,900,000
Net proceeds from sale of the common stock, after deducting fees and other offering expenses (in dollars) \| $										$ 12,700
Maximum
Aggregate offering price for at-the-market offering program \| $					$ 30,000
Series A Warrants
Number of shares of common stock that could be purchased with warrants				4,100,000
Exercise price (in dollars per share) \| $ / shares		$ 1.34		$ 3.50
Number of warrants or shares of common stock to be sold to purchase common stock				1
Number of shares of common stock purchased with each warrant				1
Length of time from issue date until warrants are exercisable				6 months
Length of time from exercise date until warrants expire				5 years
Balance, April 22, 2016 (in shares)						4,107,500	4,107,500
Issuance of warrants October 21, 2016 (in shares)						6,300,000
Balance, end of period (in shares)			4,107,500			10,407,500	4,107,500	10,407,500
Series A Warrants \| Maximum
Number of shares of common stock that could be purchased with warrants		6,300,000
Series B Warrants
Exercise price (in dollars per share) \| $ / shares		$ 1.20		$ 3.48
Exercise price pre-funded at closing (in dollars per share) \| $ / shares		1.19
Exercise price, payable upon exercise (in dollars per share) \| $ / shares		$ 0.01
Number of warrants or shares of common stock to be sold to purchase common stock				2
Length of time from exercise date until warrants expire				9 months
Balance, April 22, 2016 (in shares)						1,407,500	5,515,000
Issuance of warrants October 21, 2016 (in shares)						2,700,000
Warrants exercised (in shares)						(1,407,500)	(4,107,500)
Balance, end of period (in shares)			5,515,000			2,700,000	1,407,500	2,700,000
Series B Warrants \| Maximum
Number of shares of common stock that could be purchased with warrants		2,700,000		5,500,000