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Schedule III - Real Estate and Accumulated Depreciation (Rollforward) (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Changes in cost of properties |  |  |
Beginning balance | $ 4,348,006 | $ 4,148,529 | $ 3,980,813
Improvements and other additions | 405,940 | 480,418 | 224,524
Sales | (65,475) | (242,497) | (53,547)
Impairments | (1,530) | (329) | (2,493)
Other dispositions | (139) | (340) | (768)
Reclassification to right-of use asset | 0 | (37,775) | 0
Ending balance | 4,686,802 | 4,348,006 | 4,148,529
Changes in accumulated depreciation |  |  |
Beginning balance | 1,007,120 | 897,903 | 801,038
Depreciation expense | 119,377 | 117,973 | 112,610
Sales | (2,105) | (8,416) | (14,845)
Impairments | 0 | 0 | (132)
Other dispositions | (139) | (340) | (768)
Ending balance | $ 1,124,253 | $ 1,007,120 | $ 897,903

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- Definition Represents the amount of impairment charged to real estate investments during the period. + References No definition available. + 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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- Definition Amount of decrease to accumulated depreciation for real estate investments sold 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(Footnote 4)) -URI http://asc.fasb.org/extlink&oid=120402810&loc=d3e638233-123024 + Details
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- Definition Amount, before accumulated depreciation, of real estate investment by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate. Excludes real estate not held as investment or interest. + 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 E)) -URI http://asc.fasb.org/extlink&oid=120402810&loc=d3e638233-123024 + Details
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- Definition Amount of increase in real estate investments related to improvements 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(Footnote 4)) -URI http://asc.fasb.org/extlink&oid=120402810&loc=d3e638233-123024 + Details
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