Lease Intangibles (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Leases [Abstract]
Amortization of acquired in-place leases, depreciation and amortization	$ 0	$ 275	$ 2,133
Amortization of above and below market leases, increase (decrease) to rental income	$ 0	$ 117	$ (54)

Aggregate amount of intangible asset amortization recognized as expense during the period included under depreciation and amortization.

No definition available.

Name:	eqc_FiniteLivedIntangibleAssetsAmortizationExpenseIncludedInDepreciationAndAmortization
Namespace Prefix:	eqc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration