Basis of Presentation and Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2019
Accounting Policies [Abstract]
Basis of Presentation	Boston Properties, Inc. does not have any other significant assets, liabilities or operations, other than its investment in Boston Properties Limited Partnership, nor does it have employees of its own. Boston Properties Limited Partnership, not Boston Properties, Inc., generally executes all significant business relationships other than transactions involving securities of Boston Properties, Inc. All majority-owned subsidiaries and joint ventures over which the Company has financial and operating control and variable interest entities (“VIEs”) in which the Company has determined it is the primary beneficiary are included in the consolidated financial statements. All significant intercompany balances and transactions have been eliminated in consolidation. The Company accounts for all other unconsolidated joint ventures using the equity method of accounting. Accordingly, the Company’s share of the earnings of these joint ventures and companies is included in consolidated net income. The accompanying interim financial statements are unaudited; however, the financial statements have been prepared in accordance with generally accepted accounting principles (“GAAP”) for interim financial information and in conjunction with the rules and regulations of the Securities and Exchange Commission. Accordingly, they do not include all of the disclosures required by GAAP for complete financial statements. In the opinion of management, all adjustments (consisting solely of normal recurring matters) necessary for a fair statement of the financial statements for these interim periods have been included. The results of operations for the interim periods are not necessarily indicative of the results to be obtained for other interim periods or for the full fiscal year. The year-end consolidated balance sheet data was derived from audited financial statements, but does not include all disclosure required by GAAP. These financial statements should be read in conjunction with the Company’s financial statements and notes thereto contained in the Company’s Annual Report in the Company’s Form 10-K for its fiscal year ended December 31, 2018.
Fair Value of Financial Instruments	The Company follows the authoritative guidance for fair value measurements when valuing its financial instruments for disclosure purposes. Boston Properties Limited Partnership determines the fair value of its unsecured senior notes using market prices. The inputs used in determining the fair value of Boston Properties Limited Partnership’s unsecured senior notes is categorized at a Level 1 basis (as defined in Accounting Standards Codification (“ASC”) 820 “Fair Value Measurements and Disclosures” (“ASC 820”)) due to the fact that it uses quoted market rates to value these instruments. However, the inputs used in determining the fair value could be categorized at a Level 2 basis (as defined in ASC 820) if trading volumes are low. The Company determines the fair value of its related party note receivable, note receivable and mortgage notes payable using discounted cash flow analysis by discounting the spread between the future contractual interest payments and hypothetical future interest payments on note receivables / mortgage debt based on current market rates for similar securities. In determining the current market rates, the Company adds its estimates of market spreads to the quoted yields on federal government treasury securities with similar maturity dates to its debt. The inputs used in determining the fair value of the Company’s related party note receivable, note receivable, and mortgage notes payable are categorized at a Level 3 basis (as defined in ASC 820) due to the fact that the Company considers the rates used in the valuation techniques to be unobservable inputs. To the extent that there are outstanding borrowings under the unsecured line of credit or unsecured term loan, the Company utilizes a discounted cash flow methodology in order to estimate the fair value. To the extent that credit spreads have changed since the origination, the net present value of the difference between future contractual interest payments and future interest payments based on the Company’s estimate of a current market rate would represent the difference between the book value and the fair value. The Company’s estimate of a current market rate is based upon the rate, considering current market conditions and Boston Properties Limited Partnership’s specific credit profile, at which it estimates it could obtain similar borrowings. To the extent there are outstanding borrowings, this current market rate is estimated and therefore would be primarily based upon a Level 3 input. Because the Company’s valuations of its financial instruments are based on these types of estimates, the actual fair values of its financial instruments may differ materially from those estimates. In addition, the Company’s estimated fair values for these instruments as of the end of the applicable reporting period are not projections of nor necessarily indicative of estimated or actual fair values in future reporting periods.
Variable Interest Entities (VIEs)	Consolidated VIEs are those for which the Company is considered to be the primary beneficiary of a VIE. The primary beneficiary is the entity that has a controlling financial interest in the VIE, which is defined by the entity having both of the following characteristics: (1) the power to direct the activities that, when taken together, most significantly impact the VIE’s performance and (2) the obligation to absorb losses or the right to receive the returns from the VIE that could potentially be significant to the VIE. The Company has determined that it is the primary beneficiary for six of the eight entities that are VIEs.
New Accounting Pronouncements	New Accounting Pronouncements Adopted Leases On January 1, 2019, the Company adopted Accounting Standards Update (“ASU”) 2016-02, “Leases (Topic 842)” (“ASU 2016-02” or “Topic 842”). For information pertaining to the Company’s adoption and disclosures with respect to leases, see Note 4. New Accounting Pronouncements Issued but not yet Adopted Financial Instruments - Credit Losses In June 2016, the Financial Accounting Standards Board (“FASB”) issued ASU 2016-13, “Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments” (“ASU 2016-13”). ASU 2016-13 is intended to provide financial statement users with more decision-useful information about the expected credit losses on financial instruments and other commitments to extend credit held by a reporting entity at each reporting date by replacing the current incurred loss impairment methodology with a methodology that reflects expected credit losses and requires consideration of a broader range of reasonable and supportable information to inform credit loss estimates. In November 2018, the FASB issued ASU 2018-19, “Codification Improvements to Topic 326, Financial Instruments - Credit Losses” (“ASU 2018-19”). ASU 2018-19 clarifies that receivables arising from operating leases are not within the scope of Accounting Standards Codification (“ASC”) 326-20, “Financial Instruments - Credit Losses - Measured at Amortized Cost,” which addresses financial assets measured at amortized cost basis, including net investments in leases arising from sales-type and direct financing leases. Instead, impairment of receivables arising from operating leases should be accounted for in accordance with ASC 842, “Leases” (“ASC 842”). ASU 2016-13 and ASU 2018-19 are effective for the Company for reporting periods beginning after December 15, 2019, with early adoption permitted. The Company will adopt ASU 2016-13 and ASU 2018-19 effective January 1, 2020 using the modified retrospective approach, which is expected to result in the Company recognizing on January 1, 2020 the cumulative effect of adopting ASU 2016-13 and ASU 2018-19 to certain of its financial instruments outstanding on January 1, 2020. The Company expects that (1) certain of its accounts receivable, except for amounts arising from operating leases accounted for under ASC 842, (2) its related party note receivable, (3) its note receivable and (4) certain of its financial guarantees may be impacted by the adoption of ASU 2016-13 and ASU 2018-19.