Note 2 - Real Estate (Details Textual) - USD ($)	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Off-market Lease, Unfavorable	$ 231,300,000	$ 259,300,000
In-place Leases, Tenant Relationships and Above-market Leases [Member]
Finite-Lived Intangible Assets, Accumulated Amortization	499,022	485,040
Below Market Rents [Member]
Finite-Lived Intangible Assets, Accumulated Amortization	219,600,000	207,000,000.0
Above and Below Market Leases [Member]
Amortization of above and below Market Leases	22,500,000	20,000,000.0	$ 14,900,000
In-place Leases and Tenant Relationships [Member]
Amortization of above and below Market Leases	$ 26,300,000	$ 33,100,000	$ 47,400,000

Amount of non-cash amortization of intangible asset (liability) for above and below market leases.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

This element represents a liability associated with the acquisition of an off-market lease when the terms of the lease are unfavorable to the market terms for the lease at the date of acquisition.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.24)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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- Details

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- Details

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- Details

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