Unconsolidated Joint Ventures Liberty/Comcast 1701 JFK Boulevard, LP (Details) - USD ($) $ in Thousands	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017
Schedule of Equity Method Investments [Line Items]
Repayments of mortgage loans	$ 30,377	$ 3,876
Liberty Comcast 1701 JFK Boulevard, LP [Member]
Schedule of Equity Method Investments [Line Items]
Ownership percentage of equity method investment	20.00%
Philadelphia [Member] \| Liberty Comcast 1701 JFK Boulevard, LP [Member]
Schedule of Equity Method Investments [Line Items]
Ownership percentage of equity method investment	20.00%
Equity Method Investee [Member] \| Liberty Comcast 1701 JFK Boulevard, LP [Member] \| Philadelphia [Member]
Schedule of Equity Method Investments [Line Items]
Repayments of mortgage loans	$ 305,200

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=66011266&loc=d3e33918-111571

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The cash outflow to repay long-term debt that is wholly or partially secured by collateral. Excludes repayments of tax exempt secured debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3291-108585

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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