Note 10 - Stockholders' Equity (Details) - Waived Warrants (USD $)	12 Months Ended
	Dec. 31, 2014	Oct. 30, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Oct. 28, 2013	Jun. 03, 2013
Class of Warrant or Right [Line Items]
Shares of common stock associated with waived warrants (in Shares)	5,069,815	3,100,000	3,170,520	1,747,478	2,583,778
Strike price	$ 8.18		$ 10.65	$ 15.17	$ 1,418
Per share fair value	$ 8.18		$ 10.65	$ 15.17	$ 1,418
February 26, 2018 [Member]
Class of Warrant or Right [Line Items]
Shares of common stock associated with waived warrants (in Shares)	1,323,496
Expiration date of waived warrants	Feb. 26, 2018
Strike price	$ 5.31
Per share fair value	$ 5.31
February 26, 2018 [Member] | Estimate of Fair Value Measurement [Member]
Class of Warrant or Right [Line Items]
Strike price						$ 3.86	$ 6.60
Per share fair value						$ 3.86	$ 6.60
July 25, 2016 [Member]
Class of Warrant or Right [Line Items]
Shares of common stock associated with waived warrants (in Shares)	31,243
Expiration date of waived warrants	Jul. 25, 2016
Strike price	$ 18.99
Per share fair value	$ 18.99
July 25, 2016 [Member] | Estimate of Fair Value Measurement [Member]
Class of Warrant or Right [Line Items]
Strike price						$ 2.10	$ 4.41
Per share fair value						$ 2.10	$ 4.41
July 6, 2016 [Member]
Class of Warrant or Right [Line Items]
Shares of common stock associated with waived warrants (in Shares)	12,628
Expiration date of waived warrants	Jul. 06, 2016
Strike price	$ 14.09
Per share fair value	$ 14.09
July 6, 2016 [Member] | Estimate of Fair Value Measurement [Member]
Class of Warrant or Right [Line Items]
Strike price						$ 2.40	$ 4.81
Per share fair value						$ 2.40	$ 4.81
November 25, 2017 [Member]
Class of Warrant or Right [Line Items]
Shares of common stock associated with waived warrants (in Shares)	31,448
Expiration date of waived warrants	Nov. 25, 2017
Strike price	$ 12.47
Per share fair value	$ 12.47
November 25, 2017 [Member] | Estimate of Fair Value Measurement [Member]
Class of Warrant or Right [Line Items]
Strike price						$ 3.16	$ 5.56
Per share fair value						$ 3.16	$ 5.56