Board of Trustees (Details)	May 23, 2014 item	Feb. 18, 2014
Board of Trustees
Minimum holders of outstanding common shares consented to the proposal, reaching the required threshold (as a percent)		66.67%
Number of trustees	7

Represents the minimum holders of outstanding common shares consented to the proposal, reaching the required threshold, expressed as a percent.

No definition available.

Name:	eqc_MinimumPercentageOfCommonStockShareholdersConsentedForTheProposalContributingRequiredThreshold
Namespace Prefix:	eqc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant