Overview (Details)	Jun. 30, 2013 Number_of_Properties
Overview [Line Items]
Number of office properties owned	59
Wholly Owned Consolidated Properties [Member]
Overview [Line Items]
Number of office properties owned	51
Number of multifamily properties owned	9
Number of land parcels	2

Number of parcels of land subject to ground rent, in which we own fee interests as of the balance sheet date.

No definition available.

Name:	nysedei_NumberOfLandParcels
Namespace Prefix:	nysedei_
Data Type:	xbrli:positiveIntegerItemType
Balance Type:	na
Period Type:	instant