Note 12 - Quarterly Financial Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2014		Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014
Revenue			$ 2,948
Operating expenses	$ 3,273		2,814	$ 2,508	$ 1,933
Net (loss) income attributable to common stockholders - basic	$ 5,938		(7,458)	$ (4,460)	$ (4,343)
Revenue			2,948
Operating expenses	$ 3,273		2,814	$ 2,508	$ 1,933
Net loss	7,233		(5,181)	(2,563)	(2,831)
Net (loss) income attributable to common stockholders - basic	5,938		(7,458)	(4,460)	(4,343)
Net (loss) income attributable to common stockholders - diluted	$ 5,938		$ (7,458)	$ (4,460)	$ (4,343)
Basic (in dollars per share)	$ 0.52		$ (31)	$ (18.55)	$ (18.09)
Diluted (in dollars per share)	$ 0.48		$ (31)	$ (18.55)	$ (18.09)
Basic (in shares)	11,444,807	[1]	240,610	240,374	240,138
Diluted (in shares)	12,295,431	[1]	240,610	240,374	240,138

[1] In October 2014, the Company completed its initial public offering of common stock which resulted in net proceeds of approximately $62.5 million from the issuance of 7,026,500 shares of common stock, which includes the sale of 916,500 shares under the underwriter's over allotment option. Immediately prior to the closing of the Company's IPO, 498,889 shares of Common Stock were issued upon the exercise of warrants with aggregate proceeds of $1.4 million. In connection with the public offering, all of the Company's outstanding redeemable convertible preferred stock was converted to 8,651,805 shares of common stock.