Note 7 - Investments In and Advances to Real Estate Joint Ventures (Details Textual) ft² in Thousands, $ in Thousands	12 Months Ended
Dec. 31, 2020 USD ($) ft²	Dec. 31, 2019 USD ($) ft²	Dec. 31, 2018 USD ($)
Gross Leasable Area (Square Foot) \| ft²		290
Proceeds from Equity Method Investment, Distribution	$ 149,022	$ 93,877	$ 104,626
Other Liabilities, Total	324,538	346,183
Equity Method Investments	$ 590,700	578,100
Prudential Investment Program [Member]
Tangible Asset Impairment Charges, Total		$ 29,900
All Equity Method Investments [Member]
Number of Real Estate Properties	97	98
Gross Leasable Area (Square Foot) \| ft²	21,200	21,300
Prudential Investment Program [Member]
Tangible Asset Impairment Charges, Total		$ 3,700
Other Joint Venture Programs [Member]
Proceeds from Equity Method Investment, Distribution			3,600
Impairment of Long-Lived Assets to be Disposed of			$ 5,200
Other Liabilities, Total	$ 3,700	$ 3,500
Real Estate Joint Ventures [Member] \| Operating Properties [Member]
Number of Real Estate Properties, Interest Disposed of or Transferred		9	11
Equity Method Investment, Sales Price		$ 247,400	$ 213,500
Equity Method Investment, Realized Gain (Loss) on Disposal, Total		$ 14,400	$ 18,500
KIR [Member]
Equity Method Investment, Ownership Percentage	48.60%

Represents the amount of sale price for the entity's equity method investment.

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- Definition

The amount of floor space available to be rented in a commercial property.

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No definition available.

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- Definition

Represents the number of real estate property interests disposed of or transferred.

+ References

No definition available.

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- Definition

Amount of distribution received from equity method investee for return on investment, classified as operating activities. Excludes distribution for return of investment, classified as investing activities.

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- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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- Definition

Amount of gain (loss) on sale or disposal of an equity method investment.

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This item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.

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The aggregate amount of write-downs for impairments recognized during the period for long-lived assets held for abandonment, exchange or sale.

+ References

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- Definition

The number of real estate properties owned as of the balance sheet date.

+ References

No definition available.

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Amount of liabilities classified as other.

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The charge against earnings resulting from the aggregate write down of tangible assets from their carrying value to their fair value.

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