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Segment Information - Real Estate Investments, at Cost of Company's Reportable Segments (Details) - USD ($) $ in Thousands | Sep. 30, 2021 | Dec. 31, 2020
--- | --- | ---
Segment Reporting Information [Line Items] |  |
Operating properties | $ 3,437,074 | $ 3,474,109
Right of use asset - operating leases, net | 20,478 | 20,977
Construction-in-progress | 266,263 | 210,311
Land held for development | 118,684 | 117,984
Prepaid leasehold interests in land held for development, net | 27,762 | 39,185
Philadelphia CBD |  |
Segment Reporting Information [Line Items] |  |
Operating properties | 1,430,724 | 1,433,927
Pennsylvania Suburbs |  |
Segment Reporting Information [Line Items] |  |
Operating properties | 875,586 | 871,530
Austin, Texas |  |
Segment Reporting Information [Line Items] |  |
Operating properties | 771,977 | 728,741
Metropolitan Washington, D.C. |  |
Segment Reporting Information [Line Items] |  |
Operating properties | 271,929 | 352,794
Other |  |
Segment Reporting Information [Line Items] |  |
Operating properties | $ 86,858 | $ 87,117

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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://fasb.org/us-gaap/role/ref/legacyRef -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=120400017&loc=d3e572229-122910 + Details
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- Definition Carrying amount of land available for development. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.(a),1(d)) -URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910 + Details
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- Definition Amount of lessee's right to use underlying asset under operating lease. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 45 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123391704&loc=SL77918627-209977 + Details
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- Definition Carrying amount as of the balance sheet date of expenditures made in advance of when the economic benefit of the cost will be realized, and which will be expensed in future periods with the passage of time or when a triggering event occurs. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.10) -URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -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=120400017&loc=d3e572229-122910 + Details
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- Definition Amount of real estate investment property which may include the following: (1) land available-for-sale; (2) land available-for-development; (3) investments in building and building improvements; (4) tenant allowances; (5) developments in-process; (6) rental properties; and (7) other real estate investments. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.1(d)) -URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910 + Details
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