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Square Footage Of Signed Lease.

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No definition available.

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Term of Lease Signed (in years)

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No definition available.

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The end date of the period reflected on the cover page if a periodic report. For all other reports and registration statements containing historical data, it is the date up through which that historical data is presented. If there is no historical data in the report, use the filing date. The format of the date is CCYY-MM-DD.

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No definition available.

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Area of land held.

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No definition available.

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Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

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The current period expense charged against earnings on long-lived, physical assets not used in production, and which are not intended for resale, to allocate or recognize the cost of such assets over their useful lives; or to record the reduction in book value of an intangible asset over the benefit period of such asset; or to reflect consumption during the period of an asset that is not used in production.

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Amount of operating income (loss) attributable to disposal group, including, but not limited to, discontinued operation.

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Amount of lessee's right to use underlying asset under finance lease.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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This element represents the amount of gain (loss) on sale of properties during the reporting period gross of the applicable income taxes realized.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-URI http://asc.fasb.org/extlink&oid=6875705&loc=d3e641549-123027

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Term of lessee's finance lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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Net rentable area for properties owned.

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No definition available.

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Cash received from the sale of real estate that is held for investment, that is, it is part of an investing activity during the period.

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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.

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No definition available.

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Real Estate Narrative (Details) $ in Thousands					1 Months Ended	2 Months Ended	3 Months Ended			5 Months Ended	6 Months Ended			12 Months Ended
Real Estate Narrative (Details) $ in Thousands	Jun. 28, 2019 USD ($) ft²	Jun. 03, 2019 USD ($)	May 09, 2019 ft²	Jan. 24, 2019 USD ($) ft² a	Jan. 23, 2019 USD ($)	Jun. 02, 2019 USD ($)	Jun. 30, 2019 USD ($)	Jun. 27, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 02, 2019 USD ($)	Jun. 30, 2019 USD ($)	Jun. 27, 2019 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)	Apr. 18, 2019 USD ($) ft²	Jan. 10, 2019 USD ($) ft²
Real Estate [Line Items]
Document Period End Date											Jun. 30, 2019
Accelerated depreciation							$ 177,411		$ 156,417		$ 342,005		$ 322,214
Right of use assets - finance leases							187,269				187,269			$ 0
Proceeds from sales of real estate											60,398		141,249
Gains (loss) on sales of real estate							1,686		18,292		$ 781		114,689
Boston Properties Limited Partnership
Real Estate [Line Items]
Document Period End Date											Jun. 30, 2019
Accelerated depreciation							175,199		154,474		$ 337,881		318,327
Right of use assets - finance leases							187,269				187,269			0
Proceeds from sales of real estate											60,398		141,249
Gains (loss) on sales of real estate							1,835		18,770		930		117,677
325 Main Street [Member]
Real Estate [Line Items]
Term of Lease Signed (in years)			15-year
Net Rentable Area (in sf) \| ft²			115,000
Accelerated depreciation							9,900
325 Main Street [Member] \| Boston Properties Limited Partnership
Real Estate [Line Items]
Accelerated depreciation							$ 9,500
Platform 16 [Member]
Real Estate [Line Items]
Net Rentable Area (in sf) \| ft²				1,100,000
Finance Lease fixed purchase price				$ 134,800
Right of use assets - finance leases				$ 122,600
Lessee, Finance Lease, Term of Contract				65 years
Area of Land \| a				5.6
Carnegie Center [Member]
Real Estate [Line Items]
Net Rentable Area (in sf) \| ft²																1,700,000
Aggregate purchase price																$ 51,500
Deferred purchase price																$ 8,600
164 exington Road [Member]
Real Estate [Line Items]
Net Rentable Area (in sf) \| ft²	64,000
Gross Sale Price	$ 4,000
Proceeds from sales of real estate	3,800
Net income (loss)								$ (100)	(100)			$ (100)	(100)
Gains (loss) on sales of real estate	2,500
164 exington Road [Member] \| Boston Properties Limited Partnership
Real Estate [Line Items]
Gains (loss) on sales of real estate	$ 2,600
2600 Tower Oaks Boulevard [Member]
Real Estate [Line Items]
Net Rentable Area (in sf) \| ft²				179,000
Gross Sale Price				$ 22,700
Proceeds from sales of real estate				$ 21,400
Net income (loss)					$ (200)				(100)				(300)
Gains (loss) on sales of real estate											(600)
Impairment loss														3,100
2600 Tower Oaks Boulevard [Member] \| Boston Properties Limited Partnership
Real Estate [Line Items]
Impairment loss														$ 1,500
One Tower Center [Member]
Real Estate [Line Items]
Net Rentable Area (in sf) \| ft²															410,000
Gross Sale Price															$ 38,000
Proceeds from sales of real estate		$ 36,600
Net income (loss)						$ (100)			$ (700)	$ (900)			$ (1,300)
Gains (loss) on sales of real estate		$ (800)
Impairment loss											24,000
One Tower Center [Member] \| Boston Properties Limited Partnership
Real Estate [Line Items]
Impairment loss											$ 22,300
Future Office Building [Member] \| 325 Main Street [Member]
Real Estate [Line Items]
Net Rentable Area (in sf) \| ft²			420,000
Square Footage Of Signed Lease \| ft²			379,000
Future Retail Building [Member] \| 325 Main Street [Member]
Real Estate [Line Items]
Net Rentable Area (in sf) \| ft²			41,000