Note 7 - Preferred Stock (Details Textual)	Mar. 18, 2009 $ / shares shares	Jun. 30, 2018 $ / shares	Dec. 31, 2017 $ / shares
Preferred Stock Dividends Number of Preferred Share Purchase Rights Distributed for each Share of Common Stock Outstanding	1
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01	$ 0.01
Preferred Stock, Par or Stated Value Per Share		$ 0.01	$ 0.01
Preferred Share Purchase Right [Member]
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right | shares	0.001
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 25
Series A Junior Participating Preferred Stock [Member]
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right | shares	101
Preferred Stock, Par or Stated Value Per Share	$ 0.01