Name:	eqc_DeferredTaxAssetsMinimumPercentageOfProbabilityOfRealizationOfLargestAmountOfTaxBenefit
Namespace Prefix:	eqc_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

Represents the percentage of ownership held in the subsidiary either directly or indirectly.

No definition available.

Name:	eqc_OwnershipPercentageHeldInSubsidiary
Namespace Prefix:	eqc_
Data Type:	dtr-types:percentItemType
Balance Type:	na
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Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3602-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 45
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=123351718&loc=d3e2420-110228

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Data Type:	xbrli:monetaryItemType
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The number of real estate properties owned as of the balance sheet date.

No definition available.

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Data Type:	xbrli:integerItemType
Balance Type:	na
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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.

No definition available.

Name:	us-gaap_PropertyPlantAndEquipmentLineItems
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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

No definition available.

Name:	us-gaap_PropertyPlantAndEquipmentUsefulLife
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Data Type:	xbrli:durationItemType
Balance Type:	na
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Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_BuildingAndBuildingImprovementsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_RangeAxis=srt_MaximumMember
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