The charge against earnings in the period to reduce the carrying amount of real property to fair value.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109226691&loc=d3e2921-110230

Name:	us-gaap_ImpairmentOfRealEstate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Unconsolidated Joint Ventures -Liberty Washington, LP (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019	Sep. 30, 2018
Schedule of Equity Method Investments [Line Items]
Impairment charges - real estate assets		$ 99	$ 26,000
DC Metro \| Liberty Washington, LP [Member] \| Discontinued operations
Schedule of Equity Method Investments [Line Items]
Impairment charges - real estate assets	$ 10,300	26,700
DC Metro \| Liberty Property Limited Partnership \| Other Investments \| Equity Method Investee \| Liberty Washington, LP [Member]
Schedule of Equity Method Investments [Line Items]
Impairment charges - real estate assets	$ 2,600	$ 6,700