Basis Of Presentation And Summary Of Significant Accounting Policies Recent Accounting Pronouncements (Policies)	9 Months Ended
Sep. 30, 2017
Recent Accounting Pronouncements [Abstract]
Recent Accounting Pronouncement [Policy Text Block]	Recent Accounting Pronouncements In May 2014, the Financial Standards Accounting Board (“FASB”) issued ASU 2014-09, “Revenue from Contracts with Customers (Topic 606)” (“ASU 2014-09”). The objective of ASU 2014-09 is to establish a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and will supersede most of the existing revenue recognition guidance, including industry-specific guidance. The core principle is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. In applying ASU 2014-09, companies will perform a five-step analysis of transactions to determine when and how revenue is recognized. ASU 2014-09 applies to all contracts with customers except those that are within the scope of other topics in the FASB’s ASC. In August 2015, the FASB issued ASU 2015-14, “Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date” (“ASU 2015-14”), which delayed the effective date of ASU 2014-09 by one year making it effective for the first interim period within annual reporting periods beginning after December 15, 2017. Early adoption is permitted as of the original effective date. In May 2016, the FASB issued ASU No. 2016-12, “Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients” (“ASU 2016-12”). ASU 2016-12 is intended to clarify and provide practical expedients for certain aspects of ASU 2014-09, which outlines a single comprehensive model for entities to use in accounting for revenues arising from contracts with customers and notes that lease contracts with customers are a scope exception. ASU 2014-09 is effective for the Company for reporting periods beginning after December 15, 2017. The Company will adopt ASU 2014-09 effective January 1, 2018 using the modified retrospective approach. The Company’s project team has completed the compilation of the inventory of the sources of revenue that will be impacted by the adoption of ASU 2014-09. The Company expects that executory costs and certain non-lease components of revenue from leases (upon the adoption of ASU 2016-02), certain of its development and management services revenue and gains on sales of real estate may be impacted by the adoption of ASU 2014-09, although the Company anticipates that the impact will be to the pattern of revenue recognition and not the total revenue recognized over time. The Company is progressing with its analysis and evaluation of the impact that the adoption of ASU 2014-09 will have on the recognition pattern of each of its sources of revenue and is nearing completion of its assessment of the overall impact of adopting ASU 2014-09. The Company does not expect that the adoption of ASU 2014-09 will have a material impact on its consolidated financial statements. In February 2016, the FASB issued ASU 2016-02, “Leases (Topic 842)” (“ASU 2016-02”), which sets out the principles for the recognition, measurement, presentation and disclosure of leases for both parties to a contract (i.e., lessees and lessors). ASU 2016-02 requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase of the leased asset by the lessee. This classification will determine whether the lease expense is recognized based on an effective interest method or on a straight-line basis over the term of the lease. A lessee is also required to record a right-of-use asset and a lease liability for all leases with a term of greater than 12 months regardless of their classification. Leases with a term of 12 months or less will be accounted for similar to existing guidance for operating leases today. The new standard requires lessors to account for leases using an approach that is substantially equivalent to existing guidance for sales-type leases, direct financing leases and operating leases. ASU 2016-02 supersedes previous leasing standards. ASU 2016-02 is effective for the Company for reporting periods beginning after December 15, 2018, with early adoption permitted. The Company will adopt ASU 2016-02 effective January 1, 2019 using the modified retrospective approach. The Company is in the process of evaluating whether it will elect to apply the practical expedients. The Company is in the process of adopting ASU 2016-02, with its project team compiling an inventory of its leases that will be impacted by the adoption of ASU 2016-02. The Company continues to assess the impact of adopting ASU 2016-02. However, the Company will account for operating leases under which it is the lessor on its balance sheet in a manner similar to its current accounting with the underlying leased asset recognized as real estate. The Company expects that executory costs and certain other non-lease components will need to be accounted for separately from the lease component of the lease with the lease component continuing to be recognized on a straight-line basis over the lease term and the executory costs and certain other non-lease components being accounted for under the new revenue recognition guidance in ASU 2014-09. For leases in which the Company is the lessee, primarily consisting of ground leases, the Company will recognize a right-of-use asset and a lease liability equal to the present value of the minimum lease payments with rental payments being applied to the lease liability and to interest expense and the right-of-use asset being amortized to expense over the term of the lease. In addition, under ASU 2016-02, lessors will only capitalize incremental direct leasing costs. As a result, the Company will no longer be able to capitalize legal costs and internal leasing wages and instead will be required to expense these and other non-incremental costs as incurred. In March 2016, the FASB issued ASU 2016-09, “Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting” (“ASU 2016-09”). ASU 2016-09 is intended to improve the accounting for share-based payments and affects all organizations that issue share-based payment awards to their employees. Several aspects of the accounting for share-based payment awards are simplified with ASU 2016-09, including income tax consequences, classification of awards as equity or liabilities and classification on the statement of cash flows. ASU 2016-09 is effective for the Company for reporting periods beginning after December 15, 2016, with early adoption permitted. On January 1, 2017, the Company adopted ASU 2016-09 and elected to make an accounting policy change to its method of accounting for forfeitures on its awards of stock-based compensation including the issuance of shares of restricted common stock, LTIP Units and MYLTIP Units. The Company now accounts for forfeitures as they occur instead of estimating the number of forfeitures upon the issuance of such awards of stock-based compensation. The adoption resulted in the Company recognizing cumulative effect of a change in accounting principle adjustments to its consolidated balance sheets totaling approximately $0.3 million to Dividends in Excess of Earnings and Partners’ Capital for Boston Properties, Inc. and Boston Properties Limited Partnership, respectively, and approximately $1.8 million to noncontrolling interests - common units of Boston Properties Limited Partnership and noncontrolling interests - redeemable partnership units for Boston Properties, Inc. and Boston Properties Limited Partnership, respectively. In January 2017, the FASB issued ASU 2017-01, “Business Combinations (Topic 805): Clarifying the Definition of a Business” (“ASU 2017-01”). ASU 2017-01 clarifies the framework for determining whether an integrated set of assets and activities meets the definition of a business. The revised framework establishes a screen for determining whether an integrated set of assets and activities is a business and narrows the definition of a business, which is expected to result in fewer transactions being accounted for as business combinations. Acquisitions of integrated sets of assets and activities that do not meet the definition of a business are accounted for as asset acquisitions. This update is effective for fiscal years, and for interim periods within those fiscal years, beginning after December 15, 2017, with early adoption permitted for transactions that have not been reported in previously issued (or available to be issued) financial statements and shall be applied on a prospective basis. The Company early adopted ASU 2017-01 during the first quarter of 2017. The Company expects that acquisitions of real estate or in-substance real estate will not meet the revised definition of a business because substantially all of the fair value is concentrated in a single identifiable asset or group of similar identifiable assets (i.e. land, buildings, and related intangible assets) or because the acquisition does not include a substantive process in the form of an acquired workforce or an acquired contract that cannot be replaced without significant cost, effort or delay. In February 2017, the FASB issued ASU No. 2017-05, “Other Income - Gains and Losses from the Derecognition of Nonfinancial Assets (Subtopic 610-20): Clarifying the Scope of Asset Derecognition Guidance and Accounting for Partial Sales of Nonfinancial Assets” (“ASU 2017-05”). ASU 2017-05 updates the definition of an “in substance nonfinancial asset” and clarifies the derecognition guidance for nonfinancial assets to conform with the new revenue recognition standard. The effective date and transition methods of ASU 2017-05 are aligned with ASU 2014-09 described above and are effective for the first interim period within annual reporting periods beginning after December 15, 2017. The Company is currently assessing the potential impact that the adoption of ASU 2017-05 will have on its consolidated financial statements. In May 2017, the FASB issued ASU 2017-09, “Compensation - Stock Compensation (Topic 718): Scope of Modification Accounting” (“ASU 2017-09”). ASU 2017-09 is intended to provide clarity and reduce (1) diversity in practice, (2) cost and (3) complexity when applying the guidance in Topic 718 to a change to the terms or conditions of a share-based payment award. ASU 2017-09 is effective for public entities for fiscal years and interim periods beginning after December 15, 2017. The Company is currently assessing the potential impact that the adoption of ASU 2017-09 will have on its consolidated financial statements. In August 2017, the FASB issued ASU 2017-12, “Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities” (“ASU 2017-12”). ASU 2017-12 was issued with the objective of improving the financial reporting of hedging relationships to better portray the economic results of an entity’s risk management activities in its financial statements. ASU 2017-12 also makes certain targeted improvements to simplify the application of the hedge accounting guidance. ASU 2017-12 is effective for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Early adoption is permitted. The Company is currently assessing the potential impact that the adoption of ASU 2017-12 will have on its consolidated financial statements.

Recent Accounting Pronouncements

In May 2014, the Financial Standards Accounting Board (“FASB”) issued ASU 2014-09, “Revenue from Contracts with Customers (Topic 606)” (“ASU 2014-09”). The objective of ASU 2014-09 is to establish a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and will supersede most of the existing revenue recognition guidance, including industry-specific guidance. The core principle is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. In applying ASU 2014-09, companies will perform a five-step analysis of transactions to determine when and how revenue is recognized. ASU 2014-09 applies to all contracts with customers except those that are within the scope of other topics in the FASB’s ASC. In August 2015, the FASB issued ASU 2015-14, “Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date” (“ASU 2015-14”), which delayed the effective date of ASU 2014-09 by one year making it effective for the first interim period within annual reporting periods beginning after December 15, 2017. Early adoption is permitted as of the original effective date. In May 2016, the FASB issued ASU No. 2016-12, “Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients” (“ASU 2016-12”). ASU 2016-12 is intended to clarify and provide practical expedients for certain aspects of ASU 2014-09, which outlines a single comprehensive model for entities to use in accounting for revenues arising from contracts with customers and notes that lease contracts with customers are a scope exception. ASU 2014-09 is effective for the Company for reporting periods beginning after December 15, 2017. The Company will adopt ASU 2014-09 effective January 1, 2018 using the modified retrospective approach. The Company’s project team has completed the compilation of the inventory of the sources of revenue that will be impacted by the adoption of ASU 2014-09. The Company expects that executory costs and certain non-lease components of revenue from leases (upon the adoption of ASU 2016-02), certain of its development and management services revenue and gains on sales of real estate may be impacted by the adoption of ASU 2014-09, although the Company anticipates that the impact will be to the pattern of revenue recognition and not the total revenue recognized over time. The Company is progressing with its analysis and evaluation of the impact that the adoption of ASU 2014-09 will have on the recognition pattern of each of its sources of revenue and is nearing completion of its assessment of the overall impact of adopting ASU 2014-09. The Company does not expect that the adoption of ASU 2014-09 will have a material impact on its consolidated financial statements.

In February 2016, the FASB issued ASU 2016-02, “Leases (Topic 842)” (“ASU 2016-02”), which sets out the principles for the recognition, measurement, presentation and disclosure of leases for both parties to a contract (i.e., lessees and lessors). ASU 2016-02 requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase of the leased asset by the lessee. This classification will determine whether the lease expense is recognized based on an effective interest method or on a straight-line basis over the term of the lease. A lessee is also required to record a right-of-use asset and a lease liability for all leases with a term of greater than 12 months regardless of their classification. Leases with a term of 12 months or less will be accounted for similar to existing guidance for operating leases today. The new standard requires lessors to account for leases using an approach that is substantially equivalent to existing guidance for sales-type leases, direct financing leases and operating leases. ASU 2016-02 supersedes previous leasing standards. ASU 2016-02 is effective for the Company for reporting periods beginning after December 15, 2018, with early adoption permitted. The Company will adopt ASU 2016-02 effective January 1, 2019 using the modified retrospective approach. The Company is in the process of evaluating whether it will elect to apply the practical expedients. The Company is in the process of adopting ASU 2016-02, with its project team compiling an inventory of its leases that will be impacted by the adoption of ASU 2016-02. The Company continues to assess the impact of adopting ASU 2016-02. However, the Company will account for operating leases under which it is the lessor on its balance sheet in a manner similar to its current accounting with the underlying leased asset recognized as real estate. The Company expects that executory costs and certain other non-lease components will need to be accounted for separately from the lease component of the lease with the lease component continuing to be recognized on a straight-line basis over the lease term and the executory costs and certain other non-lease components being accounted for under the new revenue recognition guidance in ASU 2014-09. For leases in which the Company is the lessee, primarily consisting of ground leases, the Company will recognize a right-of-use asset and a lease liability equal to the present value of the minimum lease payments with rental payments being applied to the lease liability and to interest expense and the right-of-use asset being amortized to expense over the term of the lease. In addition, under ASU 2016-02, lessors will only capitalize incremental direct leasing costs. As a result, the Company will no longer be able to capitalize legal costs and internal leasing wages and instead will be required to expense these and other non-incremental costs as incurred.

In March 2016, the FASB issued ASU 2016-09, “Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting” (“ASU 2016-09”). ASU 2016-09 is intended to improve the accounting for share-based payments and affects all organizations that issue share-based payment awards to their employees. Several aspects of the accounting for share-based payment awards are simplified with ASU 2016-09, including income tax consequences, classification of awards as equity or liabilities and classification on the statement of cash flows. ASU 2016-09 is effective for the Company for reporting periods beginning after December 15, 2016, with early adoption permitted. On January 1, 2017, the Company adopted ASU 2016-09 and elected to make an accounting policy change to its method of accounting for forfeitures on its awards of stock-based compensation including the issuance of shares of restricted common stock, LTIP Units and MYLTIP Units. The Company now accounts for forfeitures as they occur instead of estimating the number of forfeitures upon the issuance of such awards of stock-based compensation. The adoption resulted in the Company recognizing cumulative effect of a change in accounting principle adjustments to its consolidated balance sheets totaling approximately $0.3 million to Dividends in Excess of Earnings and Partners’ Capital for Boston Properties, Inc. and Boston Properties Limited Partnership, respectively, and approximately $1.8 million to noncontrolling interests - common units of Boston Properties Limited Partnership and noncontrolling interests - redeemable partnership units for Boston Properties, Inc. and Boston Properties Limited Partnership, respectively.

In January 2017, the FASB issued ASU 2017-01, “Business Combinations (Topic 805): Clarifying the Definition of a Business” (“ASU 2017-01”). ASU 2017-01 clarifies the framework for determining whether an integrated set of assets and activities meets the definition of a business. The revised framework establishes a screen for determining whether an integrated set of assets and activities is a business and narrows the definition of a business, which is expected to result in fewer transactions being accounted for as business combinations. Acquisitions of integrated sets of assets and activities that do not meet the definition of a business are accounted for as asset acquisitions. This update is effective for fiscal years, and for interim periods within those fiscal years, beginning after December 15, 2017, with early adoption permitted for transactions that have not been reported in previously issued (or available to be issued) financial statements and shall be applied on a prospective basis. The Company early adopted ASU 2017-01 during the first quarter of 2017. The Company expects that acquisitions of real estate or in-substance real estate will not meet the revised definition of a business because substantially all of the fair value is concentrated in a single identifiable asset or group of similar identifiable assets (i.e. land, buildings, and related intangible assets) or because the acquisition does not include a substantive process in the form of an acquired workforce or an acquired contract that cannot be replaced without significant cost, effort or delay.

In February 2017, the FASB issued ASU No. 2017-05, “Other Income - Gains and Losses from the Derecognition of Nonfinancial Assets (Subtopic 610-20): Clarifying the Scope of Asset Derecognition Guidance and Accounting for Partial Sales of Nonfinancial Assets” (“ASU 2017-05”). ASU 2017-05 updates the definition of an “in substance nonfinancial asset” and clarifies the derecognition guidance for nonfinancial assets to conform with the new revenue recognition standard. The effective date and transition methods of ASU 2017-05 are aligned with ASU 2014-09 described above and are effective for the first interim period within annual reporting periods beginning after December 15, 2017. The Company is currently assessing the potential impact that the adoption of ASU 2017-05 will have on its consolidated financial statements.

In May 2017, the FASB issued ASU 2017-09, “Compensation - Stock Compensation (Topic 718): Scope of Modification Accounting” (“ASU 2017-09”). ASU 2017-09 is intended to provide clarity and reduce (1) diversity in practice, (2) cost and (3) complexity when applying the guidance in Topic 718 to a change to the terms or conditions of a share-based payment award. ASU 2017-09 is effective for public entities for fiscal years and interim periods beginning after December 15, 2017. The Company is currently assessing the potential impact that the adoption of ASU 2017-09 will have on its consolidated financial statements.

In August 2017, the FASB issued ASU 2017-12, “Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities” (“ASU 2017-12”). ASU 2017-12 was issued with the objective of improving the financial reporting of hedging relationships to better portray the economic results of an entity’s risk management activities in its financial statements. ASU 2017-12 also makes certain targeted improvements to simplify the application of the hedge accounting guidance. ASU 2017-12 is effective for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Early adoption is permitted. The Company is currently assessing the potential impact that the adoption of ASU 2017-12 will have on its consolidated financial statements.