Note 6 - Financial Instruments and Fair Value (Details Textual) - USD ($)	3 Months Ended				6 Months Ended		12 Months Ended
	Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2014	Dec. 31, 2011	Dec. 31, 2015
Auction Rate Securities [Member]
Available-for-sale Securities	$ 6,417,000				$ 6,417,000				$ 6,650,000
Available-for-sale Securities, Amortized Cost Basis	6,900,000				$ 6,900,000				$ 7,150,000
Auction Rate Securities Redeemed	$ 250,000		$ 275,000	$ 150,000
Derivative, Basis Spread on Variable Rate	2.25%				2.25%
Asset Impairment Charges					$ 8,236,000			$ 1,000,000
Available-for-sale Debt Securities Gross Unrealized Gain							$ 427,000
Impairment of Real Estate	$ 400,000	$ 7,100,000