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Unsecured Credit Facility (Details) - USD ($) $ in Thousands |  |  | 3 Months Ended | 9 Months Ended |
--- | --- | --- | --- | --- | ---
Jun. 15, 2021 | Mar. 16, 2021 | Sep. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2021 | Sep. 30, 2020 | Dec. 31, 2020
Line of Credit Facility [Line Items] |  |  |  |  |  |  |
Line of Credit Facility, Maximum Borrowing Capacity | $ 1,500,000 |  |  |  |  |  |
Debt Instrument, Basis Spread on Variable Rate | 0.775% |  |  |  |  |  |
Line of Credit Facility, Interest Rate Description | At Boston Properties Limited Partnership’s option, loans under the 2021 Credit Facility will bear interest at a rate per annum equal to (1) (a) in the case of loans denominated in Dollars, LIBOR, (b) in the case of loans denominated in Euro, EURIBOR, (c) in the case of loans denominated in Canadian Dollars, CDOR, and (d) in the case of loans denominated in Sterling, SONIA, in each case, plus a margin ranging from 70.0 to 140.0 basis points based on Boston Properties Limited Partnership’s credit rating or (2) an alternate base rate equal to the greatest of (a) the Federal Funds rate plus 0.5%, (b) the Administrative Agent’s prime rate, (c) LIBOR for a one-month period plus 1.00%, and (d) 1.00%, in each case, plus a margin ranging from 0 to 40 basis points based on Boston Properties Limited Partnership’s credit rating. |  |  |  |  |  |
Line of Credit Facility, Covenant Terms | Among other covenants, the 2021 Credit Facility requires that Boston Properties Limited Partnership maintain on an ongoing basis: (1) a leverage ratio not to exceed 60%, however, the leverage ratio may increase to no greater than 65% provided that it is reduced back to 60% within one year, (2) a secured debt leverage ratio not to exceed 55%, (3) a fixed charge coverage ratio of at least 1.40, (4) an unsecured debt leverage ratio not to exceed 60%, however, the unsecured debt leverage ratio may increase to no greater than 65% provided that it is reduced to 60% within one year, (5) an unsecured debt interest coverage ratio of at least 1.75 and (6) limitations on permitted investments. |  |  |  |  |  |
Long-term Line of Credit |  |  | $ 0 |  | $ 0 |  | $ 0
Loss from early extinguishment of debt |  |  | 0 | $ 0 | 898 | $ 0 |
Repayments of Unsecured Debt |  |  |  |  | $ 843,710 | 0 |
Line of Credit Facility, Expiration Date | Jun. 15, 2026 |  |  |  |  |  |
Line of Credit Facility, Commitment Fee Percentage | 0.15% |  |  |  |  |  |
Line of Credit Facility, Covenant Compliance |  |  |  |  | At September 30, 2021, Boston Properties Limited Partnership was in compliance with each of these financial and other covenant requirements. |  |
Line of Credit, Additional Borrowing Capacity | $ 500,000 |  |  |  |  |  |
Line of credit facility, maximum percent for loan advances | 65.00% |  |  |  |  |  |
Boston Properties Limited Partnership |  |  |  |  |  |  |
Line of Credit Facility [Line Items] |  |  |  |  |  |  |
Long-term Line of Credit |  |  | 0 |  | $ 0 |  | $ 0
Loss from early extinguishment of debt |  |  | 0 | $ 0 | 898 | 0 |
Repayments of Unsecured Debt |  |  |  |  | 843,710 | $ 0 |
Maximum [Member] |  |  |  |  |  |  |
Line of Credit Facility [Line Items] |  |  |  |  |  |  |
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage | 1.40% |  |  |  |  |  |
Line of Credit Facility, Commitment Fee Percentage | 0.30% |  |  |  |  |  |
Minimum [Member] |  |  |  |  |  |  |
Line of Credit Facility [Line Items] |  |  |  |  |  |  |
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage | 0.70% |  |  |  |  |  |
Line of Credit Facility, Commitment Fee Percentage | 0.10% |  |  |  |  |  |
Revolving Credit Facility [Member] | Boston Properties Limited Partnership |  |  |  |  |  |  |
Line of Credit Facility [Line Items] |  |  |  |  |  |  |
Long-term Line of Credit |  |  | $ 0 |  | $ 0 |  |
Delayed Draw Facility [Member] |  |  |  |  |  |  |
Line of Credit Facility [Line Items] |  |  |  |  |  |  |
Line of Credit Facility, Maximum Borrowing Capacity | $ 500,000 |  |  |  |  |  |
Loss from early extinguishment of debt |  | $ 500 |  |  |  |  |
Repayments of Unsecured Debt |  | $ 500,000 |  |  |  |  |

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- Definition Percentage points added to the reference rate to compute the variable rate on the debt instrument. + References No definition available. + Details
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- Definition Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 50 -Section 40 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=117329964&loc=d3e12355-112629 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 50 -Section 40 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=117329964&loc=d3e12317-112629 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585 + Details
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- Definition The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(22)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 Reference 2: 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(16)) -URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878 Reference 3: 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(16)) -URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910 + Details
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- Definition The fee, expressed as a percentage of the line of credit facility, for the line of credit facility regardless of whether the facility has been used. + References No definition available. + Details
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- Definition Identification of whether the entity has been in compliance with any credit facility debt covenants during the period. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(19)(b)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(22)(b)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
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- Definition Description of the conditions for borrowing under the credit facility including the nature of any restrictions. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
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- Definition Date the credit facility terminates, in CCYY-MM-DD format. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
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- Definition Description of the interest rate for the amounts borrowed under the credit facility, including the terms and the method for determining the interest rate (for example, fixed or variable, LIBOR plus a percentage, increasing rate, timing of interest rate resets, remarketing provisions). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
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- Definition Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
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- Definition The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility. + References No definition available. + Details
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- Definition The cash outflow to repay long-term debt that is not secured by collateral. Excludes repayments of tax exempt unsecured debt. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3291-108585 + Details
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