Note 11 - Fair Value Measurements (Details Textual) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Asset Impairment Charges, Total		$ 138	$ 17,451	$ 3,112	$ 21,626
Estimate of Fair Value Measurement [Member]
Notes Payable, Fair Value Disclosure	[1]	5,044,336		5,044,336		$ 4,983,763
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member]
Notes Payable, Fair Value Disclosure		4,700,000		4,700,000		4,800,000
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member]
Notes Payable, Fair Value Disclosure		$ 325,000		$ 325,000		$ 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 and term loan were classified within Level 3 of the fair value hierarchy. The estimated fair value amounts classified as Level 2, as of June 30, 2020 and December 31, 2019, were $4.7 billion and $4.8 billion, respectively. The estimated fair value amounts classified as Level 3, as of June 30, 2020 and December 31, 2019, were $325.0 million and $199.9 million, respectively.