Note 15 - Fair Value Disclosure of Financial Instruments (Details Textual) $ in Thousands		12 Months Ended
		Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Impairment of Real Estate		$ 48,700	$ 79,200
Measurement Input, Cap Rate [Member]
Real Estate, Measurement Input		0.1050
Measurement Input, Cap Rate [Member] | Minimum [Member]
Real Estate, Measurement Input			0.0850
Measurement Input, Cap Rate [Member] | Maximum [Member]
Real Estate, Measurement Input			0.0975
Measurement Input, Discount Rate [Member]
Real Estate, Measurement Input		0.1150
Measurement Input, Discount Rate [Member] | Minimum [Member]
Real Estate, Measurement Input			0.0925
Measurement Input, Discount Rate [Member] | Maximum [Member]
Real Estate, Measurement Input			0.1125
Estimate of Fair Value Measurement [Member]
Notes Payable, Fair Value Disclosure	[1]	$ 4,983,763	$ 4,126,450
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member]
Notes Payable, Fair Value Disclosure		4,800	4,000,000
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member]
Notes Payable, Fair Value Disclosure		$ 199,900	$ 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 December 31, 2019 and 2018, were $4.8 billion and $4.0 billion, respectively. The estimated fair value amounts classified as Level 3 as of December 31, 2019 and 2018, were $199.9 million and $97.6 million, respectively.