Organization (Narratives) (Details)	3 Months Ended
Mar. 31, 2017
Organization
Common limited partnership interest in the Operating Partnership	93.60%
Washington DC \| Washington Dc Northern Virginia
Real Estate Properties
Pro rata basis of distribution	1:2

The number of units or percentage investment held by one or more members or limited partners of the LLC or LP.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 272
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6373374&loc=d3e70478-108055

Name:	us-gaap_LimitedLiabilityCompanyLLCOrLimitedPartnershipLPMembersOrLimitedPartnersOwnershipInterest
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration