Real Estate and Accumulated Depreciation - Overall Summary and Encumbrances Reconciliation (Details)	12 Months Ended
	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2016 USD ($)
Real Estate and Accumulated Depreciation [Line Items]
Apartment Units				77,458
Overall summary of real estate and accumulated depreciation
Accumulated Depreciation	$ (6,084,616,000)	$ (5,432,805,000)	$ (4,807,709,000)	$ (5,360,389,000)
Changes in total real estate
Balance, beginning of year	28,542,697,000	27,675,383,000	26,800,948,000
Acquisitions and development	832,803,000	964,645,000	1,121,423,000
Improvements	174,981,000	186,104,000	191,243,000
Dispositions and other	(4,164,056,000)	(283,435,000)	(438,231,000)
Balance, end of year	25,386,425,000	28,542,697,000	27,675,383,000
Changes in accumulated depreciation
Balance, beginning of year	(6,084,616,000)	(5,432,805,000)	(4,807,709,000)
Depreciation	705,649,000	765,895,000	758,861,000
Dispositions and other	(1,429,876,000)	(114,084,000)	(133,765,000)
Balance, end of year	(5,360,389,000)	$ (6,084,616,000)	$ (5,432,805,000)
EQR-Fanwell 2007 LP [Member]
Overall summary of real estate and accumulated depreciation
Encumbrances				$ 299,795,866
Real Estate and Accumulated Depreciation Encumbrances Reconciliation [Abstract]
Number of Properties Encumbered				4
EQR-Wellfan 2008 LP [Member]
Overall summary of real estate and accumulated depreciation
Encumbrances				$ 549,337,934
Real Estate and Accumulated Depreciation Encumbrances Reconciliation [Abstract]
Number of Properties Encumbered				10
Archstone Master Property [Domain]
Overall summary of real estate and accumulated depreciation
Encumbrances				$ 796,845,087
Real Estate and Accumulated Depreciation Encumbrances Reconciliation [Abstract]
Number of Properties Encumbered				13
Portfolio Entity Encumbrances [Member]
Real Estate and Accumulated Depreciation Encumbrances Reconciliation [Abstract]
Number of Properties Encumbered				27
Individual Property Encumbrances [Member]
Overall summary of real estate and accumulated depreciation
Encumbrances				$ 2,473,201,938
Investment in Real Estate - Wholly Owned Unencumbered [Member]
Overall summary of real estate and accumulated depreciation
Properties				204
Units				52,102
Investment in Real Estate, Gross				$ 18,448,319,778
Accumulated Depreciation	(3,651,990,171)			(3,651,990,171)
Investment in Real Estate Net				14,796,329,607
Encumbrances				$ 0
Changes in accumulated depreciation
Balance, end of year	(3,651,990,171)
Investment in Real Estate - Wholly Owned Encumbered [Member]
Overall summary of real estate and accumulated depreciation
Properties				79
Units				21,196
Investment in Real Estate, Gross				$ 6,291,785,512
Accumulated Depreciation	(1,497,361,379)			(1,497,361,379)
Investment in Real Estate Net				4,794,424,133
Encumbrances				$ 3,818,071,013
Changes in accumulated depreciation
Balance, end of year	(1,497,361,379)
Wholly Owned Properties
Overall summary of real estate and accumulated depreciation
Properties				283
Units				73,298
Investment in Real Estate, Gross				$ 24,740,105,290
Accumulated Depreciation	(5,149,351,550)			(5,149,351,550)
Investment in Real Estate Net				19,590,753,740
Encumbrances				$ 3,818,071,013
Changes in accumulated depreciation
Balance, end of year	(5,149,351,550)
Investment in Real Estate - Partially Owned Unencumbered [Member]
Overall summary of real estate and accumulated depreciation
Properties				9
Units				1,527
Investment in Real Estate, Gross				$ 288,230,337
Accumulated Depreciation	(98,826,978)			(98,826,978)
Investment in Real Estate Net				189,403,359
Encumbrances				$ 0
Changes in accumulated depreciation
Balance, end of year	(98,826,978)
Investment in Real Estate - Partially Owned Encumbered [Member]
Overall summary of real estate and accumulated depreciation
Properties				8
Units				1,688
Investment in Real Estate, Gross				$ 358,089,848
Accumulated Depreciation	(112,210,888)			(112,210,888)
Investment in Real Estate Net				245,878,960
Encumbrances				$ 301,109,812
Changes in accumulated depreciation
Balance, end of year	(112,210,888)
NONCONTROLLING INTERESTS – PARTIALLY OWNED PROPERTIES
Overall summary of real estate and accumulated depreciation
Properties				17
Units				3,215
Investment in Real Estate, Gross				$ 646,320,185
Accumulated Depreciation	(211,037,866)			(211,037,866)
Investment in Real Estate Net				435,282,319
Encumbrances				$ 301,109,812
Changes in accumulated depreciation
Balance, end of year	(211,037,866)
Unencumbered Properties [Member]
Overall summary of real estate and accumulated depreciation
Properties				213
Units				53,629
Investment in Real Estate, Gross				$ 18,736,550,115
Accumulated Depreciation	(3,750,817,149)			(3,750,817,149)
Investment in Real Estate Net				14,985,732,966
Encumbrances				$ 0
Changes in accumulated depreciation
Balance, end of year	(3,750,817,149)
Encumbered Properties [Member]
Overall summary of real estate and accumulated depreciation
Properties				87
Units				22,884
Investment in Real Estate, Gross				$ 6,649,875,360
Accumulated Depreciation	(1,609,572,267)			(1,609,572,267)
Investment in Real Estate Net				5,040,303,093
Encumbrances				$ 4,119,180,825
Changes in accumulated depreciation
Balance, end of year	(1,609,572,267)
Total Consolidated Investment in Real Estate [Member]
Overall summary of real estate and accumulated depreciation
Properties				300
Units				76,513
Investment in Real Estate, Gross				$ 25,386,425,475
Accumulated Depreciation	(5,360,389,416)			(5,360,389,416)
Investment in Real Estate Net				20,026,036,059
Encumbrances				$ 4,119,180,825
Changes in accumulated depreciation
Balance, end of year	$ (5,360,389,416)