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number of investors

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Number Of Variable Mortgage Loans

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Number of extensions

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Percentage points added to the reference rate to compute the variable rate on the debt instrument.

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Discussion of whether the debt instrument is secured or unsecured, and, if secured, a description of the collateral and guarantees required or provided.

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Face (par) amount of debt instrument at time of issuance.

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Contractual interest rate for funds borrowed, under the debt agreement.

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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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Weighted average interest rate of debt outstanding.

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

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Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

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

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The cash inflow during the period from additional borrowings in aggregate debt. Includes proceeds from short-term and long-term debt.

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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.

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Mortgage Notes Payable, Net (Details) $ in Thousands					12 Months Ended
Mortgage Notes Payable, Net (Details) $ in Thousands	Dec. 31, 2021 USD ($) Rate	Dec. 14, 2021 USD ($) loanExtension yr Rate shares	Dec. 10, 2021 USD ($) Rate	Mar. 26, 2021 USD ($) Rate	Dec. 31, 2021 USD ($) Rate	Dec. 31, 2020 USD ($) Rate	Dec. 31, 2019 USD ($)	Dec. 15, 2021	Dec. 09, 2021 USD ($) Rate
Debt Instrument [Line Items]
Mortgage notes payable, net	$ 3,267,914				$ 3,267,914	$ 2,909,081
Debt Instrument, Collateral					each collateralized by one or more buildings and related land included in real estate assets	each collateralized by one or more buildings and related land included in real estate assets
Number Of Variable Mortgage Loans	0				0	0
Repayments of Secured Debt					$ 832,296	$ 17,168	$ 46,173
Loss from early extinguishment of debt					45,182	0	29,540
Assumption of mortgage notes payable					200,311	0	0
Debt Instrument, Basis Spread on Variable Rate	0.775%
Boston Properties Limited Partnership
Debt Instrument [Line Items]
Mortgage notes payable, net	$ 3,267,914				3,267,914	2,909,081
Repayments of Secured Debt					832,296	17,168	46,173
Loss from early extinguishment of debt					45,182	0	29,540
Assumption of mortgage notes payable					200,311	0	$ 0
601 Lexington Avenue
Debt Instrument [Line Items]
Noncontrolling Interest, Ownership Percentage by Parent			55.00%
Loss from early extinguishment of debt			$ 100
360 Park South Avenue
Debt Instrument [Line Items]
Debt - Total loan amount		$ 220,000
Noncash or Part Noncash Acquisition, Value of Assets Acquired		300,700
Assumption of mortgage notes payable		$ 200,300
number of investors								2
Ownership Percentage								42.21%
360 Park South Avenue \| Boston Properties Limited Partnership
Debt Instrument [Line Items]
Noncash or Part Noncash Acquisition, Noncash Financial or Equity Instrument Consideration, Shares Issued \| shares		866,503
Fixed Rate Mortgage [Member]
Debt Instrument [Line Items]
Mortgage notes payable, net	$ 3,300,000				$ 3,300,000	$ 2,900,000
Debt, Weighted Average Interest Rate \| Rate	3.24%				3.24%	3.72%
Fixed Rate Mortgage [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage \| Rate	2.79%				2.79%	3.43%
Fixed Rate Mortgage [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage \| Rate	3.43%				3.43%	6.94%
Fixed Rate Mortgage [Member] \| University Place
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage \| Rate				6.94%
Repayments of Secured Debt				$ 900
Fixed Rate Mortgage [Member] \| 601 Lexington Avenue
Debt Instrument [Line Items]
Mortgage notes payable, net			$ 1,000,000						$ 616,100
Debt Instrument, Interest Rate, Stated Percentage \| Rate			2.79%						4.75%
Fixed Rate Mortgage [Member] \| 360 Park South Avenue
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage \| Rate		6.044%
Repayments of Secured Debt		$ 200,300
Adjustable Rate Loans \| 360 Park South Avenue
Debt Instrument [Line Items]
Debt - Total loan amount		220,000
Proceeds from Issuance of Debt		$ 202,000
Debt Instrument, Basis Spread on Variable Rate \| Rate		2.40%
Number of extensions \| loanExtension		2
Extension Option (in years) \| yr		1