Portion of Building Leased (percentage)

No definition available.

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- Definition

Sale Price Of Sold Property

+ References

No definition available.

+ Details

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Balance Type:	debit
Period Type:	instant

- Definition

Amount of assets acquired at the acquisition date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=56956791&loc=d3e4845-128472

+ Details

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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3602-108585

+ Details

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Period Type:	duration

- Definition

This element represents the amount of gain (loss) on sale of properties during the reporting period gross of the applicable income taxes realized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 974
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-15.(a)(1)(ii)
-URI http://asc.fasb.org/extlink&oid=6875705&loc=d3e641549-123027

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=51719941&loc=d3e2921-110230

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3602-108585

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The parent entity's interest in net assets of the subsidiary, expressed as a percentage.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	instant

- Definition

Net rentable area for properties owned.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:areaItemType
Balance Type:	na
Period Type:	instant

- Definition

The net result for the period of deducting operating expenses from operating revenues.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3179-108585

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

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.

+ Details

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Data Type:	xbrli:stringItemType
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- Definition

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1)
-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

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- Details

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- Details

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Real Estate (Narrative) (Details)					1 Months Ended	3 Months Ended		5 Months Ended	9 Months Ended
Real Estate (Narrative) (Details)	Aug. 19, 2016 USD ($) ft²	Aug. 16, 2016 USD ($)	Feb. 03, 2016 USD ($) ft²	Feb. 01, 2016 USD ($) ft²	Jan. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 16, 2016 ft²	Jun. 24, 2016 ft²	May 27, 2016 ft²	Apr. 22, 2016 USD ($) ft²
Real Estate Properties [Line Items]
Net income (loss)						$ 157,605,000	$ 227,750,000		$ 626,082,000	$ 638,885,000
Proceeds from sales of real estate									122,750,000	389,457,000
Gains on sales of real estate						12,983,000	199,479,000		80,606,000	294,563,000
Impairment loss						1,783,000	0		1,783,000	0
Depreciation and amortization						203,748,000	153,015,000		516,371,000	475,082,000
Revenues						625,228,000	629,884,000		1,914,759,000	1,866,581,000
415 Main Street [Member]
Real Estate Properties [Line Items]
Net income (loss)					$ 1,200,000		(35,000)			6,200,000
Sale Price Of Sold Property				$ 105,400,000
Proceeds from sales of real estate				$ 104,900,000
Net Rentable Area (in sf) \| ft²				231,000
Broad Run Business Park [Member]
Real Estate Properties [Line Items]
Sale Price Of Sold Property		$ 18,000,000
Proceeds from sales of real estate		17,900,000
Gains on sales of real estate		$ 13,000,000
601 Massachusetts Avenue [Member]
Real Estate Properties [Line Items]
Net Rentable Area (in sf) \| ft²													479,000
804 Carnegie Center [Member]
Real Estate Properties [Line Items]
Net Rentable Area (in sf) \| ft²													130,000
10 CityPoint [Member]
Real Estate Properties [Line Items]
Net Rentable Area (in sf) \| ft²												241,000
888 Boylston Street [Member]
Real Estate Properties [Line Items]
Net Rentable Area (in sf) \| ft²											425,000
Terminated lease at 250 West 55thStreet in NYC [Member]
Real Estate Properties [Line Items]
Net Rentable Area (in sf) \| ft²			85,000
Revenues			$ 45,000,000
Boston Properties Inc \| 415 Main Street [Member]
Real Estate Properties [Line Items]
Gains on sales of real estate				$ 60,800,000
Boston Properties Limited Partnership
Real Estate Properties [Line Items]
Net income (loss)						162,771,000	229,748,000		635,219,000	644,880,000
Proceeds from sales of real estate									122,750,000	389,457,000
Gains on sales of real estate						12,983,000	199,723,000		82,775,000	294,807,000
Impairment loss						1,783,000	0		1,783,000	0
Depreciation and amortization						198,582,000	151,017,000		507,234,000	469,087,000
Revenues						625,228,000	$ 629,884,000		$ 1,914,759,000	$ 1,866,581,000
Boston Properties Limited Partnership \| 415 Main Street [Member]
Real Estate Properties [Line Items]
Gains on sales of real estate				$ 63,000,000
Consolidated Properties [Member] \| 601 Lexington Avenue [Member]
Real Estate Properties [Line Items]
Ownership Percentage by the Company	55.00%
Peterson Way [Member]
Real Estate Properties [Line Items]
Purchase price														$ 78,000,000
Net income (loss)								$ 6,000
Net Rentable Area (in sf) \| ft²														218,000
Portion of Building Leased (percentage)														100.00%
Revenues								$ 2,400,000
Future development [Member] \| Peterson Way [Member]
Real Estate Properties [Line Items]
Net Rentable Area (in sf) \| ft²														632,000
Land [Member] \| Washingtonian North [Member]
Real Estate Properties [Line Items]
Impairment loss						$ 1,800,000
Property Partnerships Member \| 601 Lexington Avenue [Member]
Real Estate Properties [Line Items]
Depreciation and amortization	$ 21,400,000
Property Partnerships Member \| Boston Properties Inc \| 601 Lexington Avenue [Member]
Real Estate Properties [Line Items]
Depreciation and amortization	50,800,000
Property Partnerships Member \| Boston Properties Limited Partnership \| 601 Lexington Avenue [Member]
Real Estate Properties [Line Items]
Depreciation and amortization	$ 47,600,000
Property Partnerships Member \| Office [Member] \| 601 Lexington Avenue [Member]
Real Estate Properties [Line Items]
Net Rentable Area (in sf) \| ft²	195,000
Property Partnerships Member \| Retail Member] \| 601 Lexington Avenue [Member]
Real Estate Properties [Line Items]
Net Rentable Area (in sf) \| ft²	25,000