CONSOLIDATED STATEMENTS OF OPERATIONS (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Debt discounts, premiums and deferred financing fees	$ 3,135	$ 3,725	$ 1,028

The component of interest expense representing the noncash expenses charged against earnings in the period to allocate debt discount and premium, and the costs to issue debt and obtain financing over the related instruments excluding discontinued operations.

No definition available.

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