Schedule III - Real Estate and Accumulated Depreciation-Overall Summary (Details)	Dec. 31, 2019 USD ($) Property ApartmentUnit	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Overall summary of real estate and accumulated depreciation
Investment in Real Estate, Gross	$ 27,533,607,000	$ 26,511,022,000	$ 26,026,896,000	$ 25,386,425,000
Accumulated Depreciation	$ (7,276,786,000)	$ (6,696,281,000)	$ (6,040,378,000)	$ (5,360,389,000)
Investment in Real Estate - Wholly Owned Unencumbered [Member]
Overall summary of real estate and accumulated depreciation
Properties | Property	257
Units | ApartmentUnit	68,002
Investment in Real Estate, Gross	$ 23,408,268,350
Accumulated Depreciation	(6,199,955,243)
Investment in Real Estate, Net	17,208,313,107
Encumbrances	$ 0
Investment in Real Estate - Wholly Owned Encumbered [Member]
Overall summary of real estate and accumulated depreciation
Properties | Property	35
Units | ApartmentUnit	8,425
Investment in Real Estate, Gross	$ 3,204,805,398
Accumulated Depreciation	(792,348,079)
Investment in Real Estate, Net	2,412,457,319
Encumbrances	$ 1,630,731,451
Wholly Owned Properties
Overall summary of real estate and accumulated depreciation
Properties | Property	292
Units | ApartmentUnit	76,427
Investment in Real Estate, Gross	$ 26,613,073,748
Accumulated Depreciation	(6,992,303,322)
Investment in Real Estate, Net	19,620,770,426
Encumbrances	$ 1,630,731,451
Investment in Real Estate - Partially Owned Unencumbered [Member]
Overall summary of real estate and accumulated depreciation
Properties | Property	9
Units | ApartmentUnit	1,847
Investment in Real Estate, Gross	$ 524,897,809
Accumulated Depreciation	(133,111,488)
Investment in Real Estate, Net	391,786,321
Encumbrances	$ 0
Investment in Real Estate - Partially Owned Encumbered [Member]
Overall summary of real estate and accumulated depreciation
Properties | Property	8
Units | ApartmentUnit	1,688
Investment in Real Estate, Gross	$ 395,635,869
Accumulated Depreciation	(151,371,564)
Investment in Real Estate, Net	244,264,305
Encumbrances	$ 310,878,101
NONCONTROLLING INTERESTS - PARTIALLY OWNED PROPERTIES
Overall summary of real estate and accumulated depreciation
Properties | Property	17
Units | ApartmentUnit	3,535
Investment in Real Estate, Gross	$ 920,533,678
Accumulated Depreciation	(284,483,052)
Investment in Real Estate, Net	636,050,626
Encumbrances	$ 310,878,101
Unencumbered Properties [Member]
Overall summary of real estate and accumulated depreciation
Properties | Property	266
Units | ApartmentUnit	69,849
Investment in Real Estate, Gross	$ 23,933,166,159
Accumulated Depreciation	(6,333,066,731)
Investment in Real Estate, Net	17,600,099,428
Encumbrances	$ 0
Encumbered Properties [Member]
Overall summary of real estate and accumulated depreciation
Properties | Property	43
Units | ApartmentUnit	10,113
Investment in Real Estate, Gross	$ 3,600,441,267
Accumulated Depreciation	(943,719,643)
Investment in Real Estate, Net	2,656,721,624
Encumbrances	$ 1,941,609,552
Total Consolidated Investment in Real Estate [Member]
Overall summary of real estate and accumulated depreciation
Properties | Property	309
Units | ApartmentUnit	79,962
Investment in Real Estate, Gross	$ 27,533,607,426
Accumulated Depreciation	(7,276,786,374)
Investment in Real Estate, Net	20,256,821,052
Encumbrances	$ 1,941,609,552