Note 12 - Fair Value Measurements (Details Textual) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Impairment of Real Estate		$ 4,200	$ 7,600
Estimate of Fair Value Measurement [Member]
Notes Payable, Fair Value Disclosure	[1]	4,302,177		$ 4,126,450
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member]
Notes Payable, Fair Value Disclosure		4,200,000		4,000,000
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member]
Notes Payable, Fair Value Disclosure		$ 97,900		$ 97,600

[1] The Company determined that the valuation of its Senior Unsecured Notes were classified within Level 2 of the fair value hierarchy and its 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, 2019 and December 31, 2018, were $4.2 billion and $4.0 billion, respectively. The estimated fair value amounts classified as Level 3 as of March 31, 2019 and December 31, 2018, were $97.9 million and $97.6 million, respectively.