Note 12 - Fair Value Measurements (Details Textual) - Estimate of Fair Value Measurement [Member] - USD ($) $ in Thousands		Jun. 30, 2021	Dec. 31, 2020
Notes Payable, Fair Value Disclosure	[1]	$ 5,443,088	$ 5,486,953
Fair Value, Inputs, Level 2 [Member]
Notes Payable, Fair Value Disclosure		$ 5,400,000	$ 5,500,000

[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 June 30, 2021 and December 31, 2020, were $5.4 billion and $5.5 billion, respectively.