Note 12 - Fair Value Measurements - Estimate of Fair Value Differs From Carrying Amounts (Details) - USD ($) $ in Thousands		Jun. 30, 2018	Dec. 31, 2017
Reported Value Measurement [Member]
Notes payable	[1]	$ 4,591,178	$ 4,596,140
Reported Value Measurement [Member] | Mortgages [Member]
Mortgages payable	[2]	477,538	882,787
Estimate of Fair Value Measurement [Member]
Notes payable	[1]	4,338,371	4,601,479
Estimate of Fair Value Measurement [Member] | Mortgages [Member]
Mortgages payable	[2]	$ 470,651	$ 881,427

[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 June 30, 2018 and December 31, 2017, were $4.3 billion and $4.6 billion, respectively. The estimated fair value amounts classified as Level 3 as of June 30, 2018 and December 31, 2017, were $0 and $1.9 million, respectively.

[2] The Company determined that its valuation of Mortgages payable, net was classified within Level 3 of the fair value hierarchy.