Name:	eqc_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipPercentage
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Data Type:	num:percentItemType
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Period Type:	instant

Represents the total number of common shares of beneficial interest owned by the parent in a less than wholly owned subsidiary.

No definition available.

Name:	eqc_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipSharesOwned
Namespace Prefix:	eqc_
Data Type:	xbrli:sharesItemType
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Period Type:	instant

Represents the total number of common shares of beneficial interest of equity method investee owned by an investor.

No definition available.

Name:	eqc_EquityMethodInvestmentNumberOfSharesOwned
Namespace Prefix:	eqc_
Data Type:	xbrli:sharesItemType
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Represents the number of common shares of beneficial interest of equity method investee sold by an investor.

No definition available.

Name:	eqc_EquityMethodInvestmentNumberOfSharesSold
Namespace Prefix:	eqc_
Data Type:	xbrli:sharesItemType
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Period Type:	duration

The number of buildings owned as of the balance sheet date.

No definition available.

Name:	eqc_NumberOfBuildings
Namespace Prefix:	eqc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

Name:	eqc_OrganizationLineItems
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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Area of a real estate property.

No definition available.

Name:	us-gaap_AreaOfRealEstateProperty
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Data Type:	num:areaItemType
Balance Type:	na
Period Type:	instant

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 323

-SubTopic 10

-Section 50

-Paragraph 3

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571

Name:	us-gaap_EquityMethodInvestmentOwnershipPercentage
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Data Type:	num:percentItemType
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Percentage of subsidiary's or equity investee's stock owned by parent company before stock transaction.

No definition available.

Name:	us-gaap_SaleOfStockPercentageOfOwnershipBeforeTransaction
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
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Period Type:	duration

Number of new stock issued during the period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.3-04)

-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 29, 30

-Article 5

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Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

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Namespace Prefix:
Data Type:	na
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Namespace Prefix:
Data Type:	na
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