Investments in Real Estate - Schedule of Net Real Estate (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Real Estate [Line Items]
Buildings and building improvements	$ 3,144,176	$ 2,962,982
Land, land estates and land improvements	367,272	355,697
Construction in progress	3,116	1,895
Real estate - intangible assets	409,293	409,756
Investments in real estate under construction	75,906	13,313
Real estate, gross	3,999,763	3,743,643
Accumulated depreciation and amortization	(884,465)	(887,629)
Real estate, net	3,115,298	2,856,014
Accumulated amortization	199,997	212,033
Amortization expense, next 12 months	32,240
Amortization expense, year 2	30,559
Amortization expense, year 3	29,560
Amortization expense, year 4	23,801
Amortization expense, year 5	19,802
In-place lease values
Real Estate [Line Items]
Real estate - intangible assets	357,640	339,154
Tenant relationships
Real Estate [Line Items]
Real estate - intangible assets	33,327	42,396
Above-market leases
Real Estate [Line Items]
Real estate - intangible assets	$ 18,326	$ 28,206

Real Estate Investment Property, Finite-Lived Intangible Assets and Construction in Progress, Gross

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The current amount of expenditures for a real estate project that has not yet been completed.

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

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Amount of amortization for assets, excluding financial assets and goodwill, lacking physical substance with finite life expected to be recognized in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of amortization for assets, excluding financial assets and goodwill, lacking physical substance with finite life expected to be recognized in fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of amortization for assets, excluding financial assets and goodwill, lacking physical substance with finite life expected to be recognized in second fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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

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Aggregate of the carrying amounts as of the balance sheet date of investments in building and building improvements.

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Amount before accumulated deprecation and depletion of real estate held for productive use and additions or improvements to real estate held for productive use, examples include, but are not limited to, walkways, driveways, fences, and parking lots. Excludes land held for sale.

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Carrying amount as of the balance sheet date of unprocessed goods that will be used in the course of a construction project which will become a part of the finished inventory.

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The cumulative amount of depreciation for real estate property held for investment purposes.

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Amount of real estate investment property, net of accumulated depreciation, which may include the following: (1) land available-for-sale; (2) land available-for-development; (3) investments in building and building improvements; (4) tenant allowances; (5) developments in-process; (6) rental properties; and (7) other real estate investments.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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