Note 7 - Notes and Mortgages Payable (Details Textual) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Medium-term Notes [Member]
Repayments of Unsecured Debt		$ 300,000
Debt Instrument, Interest Rate, Stated Percentage		5.783%
Mortgages [Member] | Fair Market Value Adjustment Amount [Member]
Long-term Debt, Fair Value		$ 300
Mortgages [Member]
Repayments of Long-term Debt		$ 101,500
Number of Real Estate Properties		7
Repayments of Unsecured Debt		$ 300,000	$ 500,000
Long-term Debt, Fair Value	[1]	$ 1,521,165		$ 1,629,760

[1] The Company determined that its valuation of Mortgages payable was classified within Level 3 of the fair value hierarchy.