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Schedule III - Real Estate and Accumulated Depreciation-Overall Summary (Details) | Dec. 31, 2020 USD ($) Property ApartmentUnit | Dec. 31, 2019 USD ($) | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($)
--- | --- | --- | --- | ---
Overall summary of real estate and accumulated depreciation |  |  |  |
Investment in Real Estate, Gross | $ 27,203,325,000 | $ 27,533,607,000 | $ 26,511,022,000 | $ 26,026,896,000
Accumulated Depreciation | $ (7,859,657,000) | $ (7,276,786,000) | $ (6,696,281,000) | $ (6,040,378,000)
Investment in Real Estate - Wholly Owned Unencumbered [Member] |  |  |  |
Overall summary of real estate and accumulated depreciation |  |  |  |
Properties | Property | 246 |  |  |
Units | ApartmentUnit | 64,363 |  |  |
Investment in Real Estate, Gross | $ 22,528,561,227 |  |  |
Accumulated Depreciation | (6,521,859,521) |  |  |
Investment in Real Estate, Net | 16,006,701,706 |  |  |
Encumbrances | $ 0 |  |  |
Investment in Real Estate - Wholly Owned Encumbered [Member] |  |  |  |
Overall summary of real estate and accumulated depreciation |  |  |  |
Properties | Property | 42 |  |  |
Units | ApartmentUnit | 10,127 |  |  |
Investment in Real Estate, Gross | $ 3,704,582,050 |  |  |
Accumulated Depreciation | (1,032,587,859) |  |  |
Investment in Real Estate, Net | 2,671,994,191 |  |  |
Encumbrances | $ 2,088,144,904 |  |  |
Wholly Owned Properties |  |  |  |
Overall summary of real estate and accumulated depreciation |  |  |  |
Properties | Property | 288 |  |  |
Units | ApartmentUnit | 74,490 |  |  |
Investment in Real Estate, Gross | $ 26,233,143,277 |  |  |
Accumulated Depreciation | (7,554,447,380) |  |  |
Investment in Real Estate, Net | 18,678,695,897 |  |  |
Encumbrances | $ 2,088,144,904 |  |  |
Investment in Real Estate - Partially Owned Unencumbered [Member] |  |  |  |
Overall summary of real estate and accumulated depreciation |  |  |  |
Properties | Property | 14 |  |  |
Units | ApartmentUnit | 2,699 |  |  |
Investment in Real Estate, Gross | $ 672,990,027 |  |  |
Accumulated Depreciation | (231,543,640) |  |  |
Investment in Real Estate, Net | 441,446,387 |  |  |
Encumbrances | $ 0 |  |  |
Investment in Real Estate - Partially Owned Encumbered [Member] |  |  |  |
Overall summary of real estate and accumulated depreciation |  |  |  |
Properties | Property | 2 |  |  |
Units | ApartmentUnit | 700 |  |  |
Investment in Real Estate, Gross | $ 297,191,796 |  |  |
Accumulated Depreciation | (73,666,183) |  |  |
Investment in Real Estate, Net | 223,525,613 |  |  |
Encumbrances | $ 205,744,819 |  |  |
NONCONTROLLING INTERESTS - PARTIALLY OWNED PROPERTIES |  |  |  |
Overall summary of real estate and accumulated depreciation |  |  |  |
Properties | Property | 16 |  |  |
Units | ApartmentUnit | 3,399 |  |  |
Investment in Real Estate, Gross | $ 970,181,823 |  |  |
Accumulated Depreciation | (305,209,823) |  |  |
Investment in Real Estate, Net | 664,972,000 |  |  |
Encumbrances | $ 205,744,819 |  |  |
Unencumbered Properties [Member] |  |  |  |
Overall summary of real estate and accumulated depreciation |  |  |  |
Properties | Property | 260 |  |  |
Units | ApartmentUnit | 67,062 |  |  |
Investment in Real Estate, Gross | $ 23,201,551,254 |  |  |
Accumulated Depreciation | (6,753,403,161) |  |  |
Investment in Real Estate, Net | 16,448,148,093 |  |  |
Encumbrances | $ 0 |  |  |
Encumbered Properties [Member] |  |  |  |
Overall summary of real estate and accumulated depreciation |  |  |  |
Properties | Property | 44 |  |  |
Units | ApartmentUnit | 10,827 |  |  |
Investment in Real Estate, Gross | $ 4,001,773,846 |  |  |
Accumulated Depreciation | (1,106,254,042) |  |  |
Investment in Real Estate, Net | 2,895,519,804 |  |  |
Encumbrances | $ 2,293,889,723 |  |  |
Total Consolidated Investment in Real Estate [Member] |  |  |  |
Overall summary of real estate and accumulated depreciation |  |  |  |
Properties | Property | 304 |  |  |
Units | ApartmentUnit | 77,889 |  |  |
Investment in Real Estate, Gross | $ 27,203,325,100 |  |  |
Accumulated Depreciation | (7,859,657,203) |  |  |
Investment in Real Estate, Net | 19,343,667,897 |  |  |
Encumbrances | $ 2,293,889,723 |  |  |

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