Note 11 - Fair Value Measurements (Details Textual) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Impairment of Real Estate		$ 3,000	$ 4,200
Estimate of Fair Value Measurement [Member]
Notes Payable, Fair Value Disclosure	[1]	5,041,889		$ 4,983,763
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member]
Notes Payable, Fair Value Disclosure		$ 4,400		4,800
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member]
Notes Payable, Fair Value Disclosure			$ 625,400	$ 199,900

[1] The Company determined that the valuation of its Senior Unsecured Notes were classified within Level 2 of the fair value hierarchy and its unsecured revolving credit facility was classified within Level 3 of the fair value hierarchy. The estimated fair value amounts classified as Level 2, as of March 31, 2020 and December 31, 2019, were $4.4 billion and $4.8 billion, respectively. The estimated fair value amounts classified as Level 3, as of March 31, 2020 and December 31, 2019, were $625.4 million and $199.9 million, respectively.