CONSOLIDATED STATEMENTS OF CHANGES IN CAPITAL OF ERP OPERATING LIMITED PARTNERSHIP (Parenthetical) - Series K Preferred Stock [Member]	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Preferred Stock Preference Units Dividend Rate Percentage	8.29%	8.29%	8.29%
Preferred Stock \| ERPOP [Member]
Preferred Stock Preference Units Dividend Rate Percentage	8.29%	8.29%	8.29%

The percentage rate used to calculate dividend payments on preferred shares/preference units.

No definition available.

Name:	eqr_PreferredStockPreferenceUnitsDividendRatePercentage
Namespace Prefix:	eqr_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration