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

Board of Trustees - Narrative (Details) - trustee	Jun. 16, 2015	Jul. 31, 2014	May. 23, 2014	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 elected		7	7
Total number of trustees	9	11