Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2019	Jul. 26, 2019
Document And Entity Information [Line Items]
Entity Registrant Name	EQUITY RESIDENTIAL
Entity Central Index Key	0000906107
Document Type	10-Q
Document Period End Date	Jun. 30, 2019
Amendment Flag	false
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Trading Symbol	EQR
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		370,852,718
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity File Number	1-12252
Entity Tax Identification Number	133675988
Entity Address, Address Line One	Two North Riverside Plaza
Entity Address, City or Town	Chicago
Entity Address, State or Province	Illinois
Entity Address, Postal Zip Code	60606
City Area Code	312
Local Phone Number	474-1300
ERPOP [Member]
Document And Entity Information [Line Items]
Entity Registrant Name	ERP OPERATING LIMITED PARTNERSHIP
Entity Central Index Key	0000931182
Document Type	10-Q
Document Period End Date	Jun. 30, 2019
Amendment Flag	false
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity File Number	0-24920
Entity Tax Identification Number	363894853
Entity Address, Address Line One	Two North Riverside Plaza
Entity Address, City or Town	Chicago
Entity Address, State or Province	Illinois
Entity Address, Postal Zip Code	60606
City Area Code	312
Local Phone Number	474-1300