Note 6 - Financial Instruments and Fair Value (Details Textual)	3 Months Ended				9 Months Ended		12 Months Ended
	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2011 USD ($)	Dec. 31, 2015 USD ($)
Auction Rate Securities [Member]
Available-for-sale Securities	$ 6,231,000				$ 6,231,000				$ 6,650,000
Available-for-sale Securities, Amortized Cost Basis	6,700,000				$ 6,700,000				$ 7,150,000
Auction Rate Securities Redeemed	$ 200,000	$ 250,000	$ 275,000	$ 150,000
Derivative, Basis Spread on Variable Rate	2.25%				2.25%
Asset Impairment Charges					$ 8,247,000			$ 1,000,000
Available-for-sale Debt Securities Gross Unrealized Gain							$ 427,000
Impairment of Real Estate					$ 7,500,000
Number of Properties Sold	2
Real Estate Sold, Cost Basis	$ 4,400,000