Note 15 - Fair Value Disclosure of Financial Instruments (Details Textual) $ in Thousands		12 Months Ended
		Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Impairment of Real Estate		$ 79,200	$ 67,300
Measurement Input, Cap Rate [Member] | Minimum [Member]
Real Estate, Measurement Input		0.085	0.085
Measurement Input, Cap Rate [Member] | Maximum [Member]
Real Estate, Measurement Input		0.0975	0.095
Measurement Input, Discount Rate [Member] | Minimum [Member]
Real Estate, Measurement Input		0.0925	0.09
Measurement Input, Discount Rate [Member] | Maximum [Member]
Real Estate, Measurement Input		0.1125	0.105
Estimate of Fair Value Measurement [Member]
Notes Payable, Fair Value Disclosure	[1]	$ 4,126,450	$ 4,601,479
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member]
Notes Payable, Fair Value Disclosure		4,000,000	4,600,000
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member]
Notes Payable, Fair Value Disclosure		$ 97,600	$ 1,900

[1] The Company determined that the valuation of its Senior Unsecured Notes were classified within Level 2 of the fair value hierarchy and Credit Facility were classified within Level 3 of the fair value hierarchy. The estimated fair value amounts classified as Level 2 as of December 31, 2018 and 2017, were $4.0 billion and $4.6 billion, respectively. The estimated fair value amounts classified as Level 3 as of December 31, 2018 and 2017, were $97.6 million and $1.9 million, respectively.