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Debt Debt Line of Credit and Commercial Paper (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2015 | Dec. 31, 2014
Line of Credit Facility [Line Items] |  |
Debt Instrument, Basis Spread on Variable Rate | 0.00% |
Unamortized Discount | $ 46,260 |
A 175 billion LOC [Member] |  |
Line of Credit Facility [Line Items] |  |
Unsecured revolving credit facility | 1,750,000 |
A 250 billion LOC [Member] [Domain] |  |
Line of Credit Facility [Line Items] |  |
Unsecured revolving credit facility | $ 2,500,000 |
Debt Instrument, Maturity Date | Apr. 01, 2018 |
500.0 million ability to increase | $ 500,000 |
Line Of Credit Facility Commitment Fee | 15 Basis Points |
Remaining borrowing capacity | $ 2,070,000 | $ 2,120,000
Amount restricted/dedicated to support letters of credit | $ 45,100 | $ 43,800
Weighted average interest rate on revolving letter of credit | 1.07% | 0.95%
Commercial Paper [Member] |  |
Line of Credit Facility [Line Items] |  |
Commercial paper, maximum borrowing capacity | $ 500,000 |
Commercial Paper, net | 387,300 |
commercial paper principal outstanding | 387,500 |
Unamortized Discount | $ 200 |
Weighted Average Interest Rate Commercial Paper | 0.56% |
Revolving Credit Facility [Member] |  |
Line of Credit Facility [Line Items] |  |
Long-term Line of Credit |  | $ 333,000
London Interbank Offered Rate (LIBOR) [Member] | Revolving Credit Facility [Member] | A 250 billion LOC [Member] [Domain] |  |
Line of Credit Facility [Line Items] |  |
Debt Instrument, Description of Variable Rate Basis | LIBOR plus 0.95% |

X
- Definition Represents the amount by which available borrowings on the unsecured revolving credit facility may be increased. The available borrowings may be increased by adding additional banks to the facility or obtaining the agreement of existing banks to increase their commitments. + References No definition available. + Details
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Balance Type: | credit
Period Type: | duration

X
- Definition Maximum borrowing capacity under the commercial paper program without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the program. + References No definition available. + Details
Name: | eqr_Commercialpapermaximumborrowingcapacity
Namespace Prefix: | eqr_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Represents the gross amount of commercial paper outstanding, not adjusted for the discount. + References No definition available. + Details
Name: | eqr_Commercialpaperprincipaloutstanding
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Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The fee, expressed as a percentage of the line of credit facility, for the line of credit facility regardless of whether the facility has been used. + References No definition available. + Details
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Namespace Prefix: | eqr_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The weighted average interest rate on commercial paper during the period. + References No definition available. + Details
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Namespace Prefix: | eqr_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition The weighted average interest rate on the revolving line of credit during the period. + References No definition available. + Details
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Balance Type: | na
Period Type: | duration

X
- Definition Carrying value as of the balance sheet date of short-term borrowings using unsecured obligations issued by banks, corporations and other borrowers to investors. The maturities of these money market securities generally do not exceed 270 days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(a)(3)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.13(2)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 16 -Article 7 + Details
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Balance Type: | credit
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X
- Definition Percentage points added to the reference rate to compute the variable rate on the debt instrument. + References No definition available. + Details
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- Definition The reference rate for the variable rate of the debt instrument, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR. + References No definition available. + Details
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- Definition Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(2)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition The amount of debt discount that was originally recognized at the issuance of the instrument that has yet to be amortized. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 1A -URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28541-108399 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=34725769&loc=d3e28878-108400 + Details
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X
- Definition The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.16) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.16) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 19, 20, 22 -Article 5 + Details
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Balance Type: | credit
Period Type: | instant

X
- Definition Net increase or decrease in the carrying amount of the credit facility for the period for reasons other than accrued, but unpaid interest, additional borrowings, repayments, and forgiveness. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(f)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690 + Details
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Balance Type: | credit
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Definition Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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Balance Type: | credit
Period Type: | instant

X
- Definition Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Details
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- Details
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- Details
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- Details
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Namespace Prefix: |
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- Details
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