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Schedule III - Real Estate and Accumulated Depreciation (Reconciliations) (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward] |  |  |
Balance at the Beginning of the Year | $ 4,006,459 | $ 3,951,719 | $ 3,830,824
Additions: |  |  |
Acquisitions | 9,722 | 0 | 509,654
Capital expenditures and assets placed into service | 113,221 | 145,378 | 129,274
Less: |  |  |
Dispositions/impairments/placed into redevelopment | (619,086) | (50,792) | (469,517)
Retirements | (36,207) | (39,846) | (48,516)
Balance at the end of the year | 3,474,109 | 4,006,459 | 3,951,719
Operating properties | 3,474,109 | 4,006,459 | 3,951,719
Tax basis of assets, cost for income tax purposes | 2,900,000 | 3,200,000 |
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward] |  |  |
Balance at the beginning of the year | 973,318 | 885,407 | 913,297
Real Estate Accumulated Depreciation Additions [Abstract] |  |  |
Depreciation expense | 138,822 | 144,131 | 137,213
Real Estate Accumulated Depreciation Less Dispositions [Abstract] |  |  |
Dispositions/impairments/placed into redevelopment | (182,526) | (16,783) | (117,589)
Retirements | (33,053) | (39,437) | (47,514)
Balance at the end of the year | 896,561 | 973,318 | 885,407
Per consolidated balance sheet | $ 896,561 | $ 973,318 | $ 885,407
Leashold Interest Land |  |  |
Real Estate Accumulated Depreciation Less Dispositions [Abstract] |  |  |
Lease agreement term | 99 years |  |
Maximum |  |  |
Real Estate Accumulated Depreciation Less Dispositions [Abstract] |  |  |
Useful life | 55 years |  |

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- Definition Cost basis of real estate investments for federal income tax purposes for entities with a substantial portion of business acquiring and holding investment real estate. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 12 -Footnote 6 -Subsection 28 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 970 -SubTopic 360 -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-28(Footnote 6)) -URI http://asc.fasb.org/extlink&oid=120402810&loc=d3e638233-123024 + Details
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- Definition Amount of accumulated depreciation pertaining to real estate investments for entities with a substantial portion of business acquiring and holding investment real estate. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 970 -SubTopic 360 -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-28(Column F)) -URI http://asc.fasb.org/extlink&oid=120402810&loc=d3e638233-123024 + Details
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