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Summary of Significant Accounting Policies - Construction in Progress (Details) - USD ($) $ in Thousands | Dec. 31, 2016 | Dec. 31, 2015
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Property, Plant and Equipment [Line Items] |  |
Construction in progress | $ 63,570 | $ 83,516
Park Van Ness |  |
Property, Plant and Equipment [Line Items] |  |
Construction in progress | 0 | 77,245
N. Glebe Road |  |
Property, Plant and Equipment [Line Items] |  |
Construction in progress | 58,147 | 0
Other |  |
Property, Plant and Equipment [Line Items] |  |
Construction in progress | $ 5,423 | $ 6,271

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- Definition The current amount of expenditures for a real estate project that has not yet been completed. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.10) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Phase -URI http://asc.fasb.org/extlink&oid=49177889 + Details
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