Represents the number of properties secured by mortgage notes.

No definition available.

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

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
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+ Details

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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.

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- Definition

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 50
-Section 40
-Paragraph 4
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- Definition

Amount of real estate investment property, net of accumulated depreciation, which may include the following: (1) land available-for-sale; (2) land available-for-development; (3) investments in building and building improvements; (4) tenant allowances; (5) developments in-process; (6) rental properties; and (7) other real estate investments.

+ References

+ Details

Name:	us-gaap_RealEstateInvestmentPropertyNet
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Carrying value as of the balance sheet date, including the current and noncurrent portions, of collateralized debt obligations (with maturities initially due after one year or beyond the operating cycle, if longer). Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
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+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Including the current and noncurrent portions, carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer). Senior note holders are paid off in full before any payments are made to junior note holders.

+ References

+ Details

Name:	us-gaap_SeniorNotes
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_DebtInstrumentAxis=us-gaap_MortgagesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Indebtedness - Narrative (Details) $ in Thousands	3 Months Ended		6 Months Ended
Indebtedness - Narrative (Details) $ in Thousands	Jun. 30, 2019 USD ($) property	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) property	Jun. 30, 2018 USD ($)	Jun. 28, 2019 USD ($)	Dec. 31, 2018 USD ($)
Debt Instrument [Line Items]
Senior unsecured notes, net					$ 250,000
Interest rate stated percentage	5.875%		5.875%
Loss on early extinguishment of debt	$ 6,374	$ 1,536	$ 6,374	$ 6,403
Real estate properties, net	463,803		463,803			$ 763,674
Mortgage notes payable, net	$ 26,091		$ 26,091			$ 26,482
Mortgage notes
Debt Instrument [Line Items]
Number of real estate properties secured by mortgage \| property	1		1
Real estate properties, net	$ 43,900		$ 43,900
Mortgage notes payable, net	$ 26,100		$ 26,100