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Summary Of Significant Accounting Policies | 9 Months Ended
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Sep. 30, 2025
Accounting Policies [Abstract] |
Summary Of Significant Accounting Policies | 2. Summary of Significant Accounting Policies BXP does not have any other significant assets, liabilities or operations, other than its investment in BPLP, nor does it have employees of its own. BPLP, not BXP, generally executes all significant business relationships other than transactions involving securities of BXP. 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 (loss). 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 (the “SEC”). 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, 2024. The Company bases its estimates on historical experience and on various other assumptions that it considers to be reasonable under the circumstances, including the impact of extraordinary events, the results of which form the basis for making significant judgments about the carrying values of assets and liabilities, assessments of future collectability, and other areas of the financial statements that are impacted by the use of estimates. Actual results may differ from these estimates under different assumptions or conditions. 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 assets of each VIE are only available to satisfy such VIE's respective liabilities. The Company has identified 11 entities that are VIEs as of September 30, 2025 and has determined that it is the primary beneficiary for eight of these entities as of September 30, 2025. Consolidated Variable Interest Entities As of September 30, 2025, BXP has identified eight consolidated VIEs, including BPLP. Excluding BPLP, the consolidated VIEs consisted of (i) the following six in-service properties: 767 Fifth Avenue (the General Motors Building), 7 Times Square (formerly Times Square Tower), 601 Lexington Avenue, 300 Binney Street, Atlantic Wharf Office Building and 100 Federal Street and (ii) 290 Binney Street, which is currently under development. The Company consolidates these VIEs because it is the primary beneficiary. The third parties’ interests in these consolidated entities (excluding BPLP’s interest) are reflected as noncontrolling interests in property partnerships in the accompanying consolidated financial statements (See Note 9). In addition, BXP’s only significant asset is its investment in BPLP and, consequently, substantially all of BXP’s assets and liabilities are the assets and liabilities of BPLP. Variable Interest Entities Not Consolidated As of September 30, 2025, BXP has identified three unconsolidated joint venture entities that are classified as VIEs. The CAB 290 Coles Venture LLC, CAB 290 Coles Holdco LLC, and 17 Hartwell JV LLC joint ventures are VIEs because they do not have sufficient equity at risk. In addition, the Company does not consolidate the entities as it does not have the power to direct the activities that, when taken together, most significantly impact the VIEs’ performance and, therefore, the Company is not considered to be the primary beneficiary. Exchangeable Debt On September 29, 2025, BPLP issued $1.0 billion aggregate principal amount of 2.00% Exchangeable Senior Notes due 2030 (the “Notes”) in a private placement (see Note 6). The Company accounts for the Notes in accordance with Accounting Standards Codification (“ASC”) 470-20, Debt with Conversion and Other Options (after the adoption of Accounting Standards Update (“ASU”) 2020-06, Debt - Debt and Other Options (Subtopic 470-20) and Derivatives and Hedging - Contracts in Entity's Own Equity (Subtopic 815-40): Accounting for Contracts in an Entity's Own Equity (“ASU 2020-06”)). The exchange feature embedded within the Notes is eligible for an exception from derivative accounting because it is indexed to BXP’s stock. BPLP is the entity through which BXP conducts substantially all of its business and owns, either directly or through subsidiaries, substantially all of its assets. As such, the exchange feature embedded within the Notes meets the equity classification under ASC 815-40, Derivatives and Hedging—Contracts in Entity's Own Equity, therefore, the exchange feature is not bifurcated. At each reporting period, the Company calculates the effect of the Notes on its dilutive earnings per common share / common unit using the if-converted method (See Note 12). Concurrently with the pricing of the Notes, the Company entered into capped call transactions (“Capped Call Transactions”) with certain financial institutions. The Capped Call Transactions cover, subject to customary adjustments, the number of shares of BXP’s common stock initially underlying the Notes. Similar to the exchange feature embedded in the Notes, the Capped Call Transactions meet all the conditions for equity classification, and therefore, the related premiums paid are recorded as a reduction to stockholders' equity for BXP and partners’ capital for BPLP. Fair Value Measurements The Company follows the authoritative guidance for fair value measurements when valuing its financial instruments for disclosure purposes. The table below presents for September 30, 2025 and December 31, 2024, the financial instruments that are being valued for disclosure purposes, as well as the Level at which they are categorized as defined in ASC 820 “Fair Value Measurements and Disclosures” (“ASC 820”).
Financial Instrument | Level
Unsecured commercial paper | Level 1
Investment in securities | Level 1
Unsecured senior notes (1) | Level 1
Unsecured exchangeable senior notes (1) | Level 1
Related party notes receivable | Level 3
Notes receivable | Level 3
Sales-type lease receivable | Level 3
Mortgage notes payable | Level 3
Unsecured line of credit | Level 3
Unsecured term loans | Level 3
_______________ (1)If trading volume for the period is low, the valuation could be categorized as Level 2. Because the Company’s valuations of its financial instruments are based on the above Levels and involve the use 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. At September 30, 2025 and December 31, 2024, the Company had $750.0 million and $500.0 million, respectively, outstanding under its unsecured commercial paper program (See Note 6). Due to their short-term maturity and stated interest rates that approximate current market rates, the fair value of outstanding commercial paper borrowings approximates the Company's carrying amount at September 30, 2025 and December 31, 2024. The Company’s non-real estate investments are shown within Prepaid Expenses and Other Assets on the Consolidated Balance Sheets and were approximately $9.4 million and $7.1 million at September 30, 2025 and December 31, 2024, respectively. The non-real estate investments utilize net asset value as the practical expedient. Non-Recurring Fair Value The following table presents the aggregate carrying value of the Company’s non-recurring fair value financial instruments and the Company’s corresponding estimate of fair value as of September 30, 2025 and December 31, 2024 (in thousands):
| September 30, 2025 |  | December 31, 2024
| Carrying Amount |  | Estimated Fair Value |  | Carrying Amount |  | Estimated Fair Value
Related party notes receivable, net (1) | $ | 88,879 |  |  | $ | 87,987 |  |  | $ | 88,779 |  |  | $ | 89,213 |
Note receivable, net | 8,898 |  |  | 8,515 |  |  | 4,947 |  |  | 6,187 |
Sales-type lease receivable, net | 15,430 |  |  | 13,863 |  |  | 14,657 |  |  | 13,632 |
Total | $ | 113,207 |  |  | $ | 110,365 |  |  | $ | 108,383 |  |  | $ | 109,032 |
Mortgage notes payable, net | $ | 4,279,482 |  |  | $ | 3,971,687 |  |  | $ | 4,276,609 |  |  | $ | 3,808,095 |
Unsecured senior notes, net | 9,803,336 |  |  | 9,494,698 |  |  | 10,645,077 |  |  | 10,005,606 |
Unsecured exchangeable senior notes, net | 975,080 |  |  | 999,132 |  |  | — |  |  | — |
Unsecured line of credit | — |  |  | — |  |  | — |  |  | — |
Unsecured term loans, net | 796,798 |  |  | 796,312 |  |  | 798,813 |  |  | 799,580 |
Unsecured commercial paper | 750,000 |  |  | 750,000 |  |  | 500,000 |  |  | 500,000 |
Total | $ | 16,604,696 |  |  | $ | 16,011,829 |  |  | $ | 16,220,499 |  |  | $ | 15,113,281 |
_______________ (1)See Note 14. During the three months ended September 30, 2025, in conjunction with the Company’s strategy to sell non-core assets, the Company evaluated its properties that were under negotiation for sale with third-parties. Based on shorter-than-expected hold periods, the Company reduced the carrying values of the properties that exceeded their fair value and recognized non-cash impairment losses (See Note 3). As a result, during the three and nine months ended September 30, 2025, BXP and BPLP recognized aggregate impairment losses of approximately $68.9 million and $66.0 million, respectively. The Company’s estimated fair value was based on Level 3 inputs as defined in ASC 820, including pending offers from third-parties, as pending offers are classified as Level 3 inputs and there were no other unobservable inputs utilized in the consolidated impairment analysis. Recurring Fair Value Derivatives In addition to the financial instruments noted above, the Company uses interest rate swap agreements to manage its interest rate risk (See Note 7). The valuation of these instruments is determined using widely accepted valuation techniques, including discounted cash flow analysis on the expected cash flows of each derivative. This analysis reflects the contractual terms of the derivatives, including the period to maturity, and uses observable market-based inputs, including interest rate curves. To comply with the provisions of ASC 820, the Company incorporates credit valuation adjustments to appropriately reflect both its own nonperformance risk and the respective counterparty’s nonperformance risk in the fair value measurements. Although the Company has determined that the majority of the inputs used to value its derivatives fall within Level 2 of the fair value hierarchy, the credit valuation adjustments associated with its derivatives utilize Level 3 inputs, such as estimates of current credit spreads to evaluate the likelihood of default by the Company and its counterparties. The Company assessed the significance of the impact of the credit valuation adjustments on the overall valuation of its derivative positions and determined that the credit valuation adjustments were not significant to the overall valuation of its derivatives. As a result, the Company has determined that its derivative valuations in their entirety are classified in Level 2 of the fair value hierarchy. The following table presents the aggregate fair value of the Company’s interest rate swaps as of September 30, 2025 and December 31, 2024 (in thousands):
Fair value |  | September 30, 2025 |  | December 31, 2024
Interest rate swaps |  | $ | (8,510) |  |  | $ | 5,252 |
Investments The Company accounts for investments in equity securities at fair value, with gains or losses resulting from changes in fair value recognized currently in earnings. The Company maintains deferred compensation plans that are designed to allow each officer and non-employee director of BXP to defer a portion of the officer’s income and the non-employee director’s compensation, respectively, on a pre-tax basis and receive a tax-deferred return on the amounts deferred based on the performance of specific investments selected by the plan participant. The Company’s obligation under the plans is that of an unsecured promise to pay the deferred compensation to the plan participants in the future. At September 30, 2025 and December 31, 2024, the Company had maintained approximately $43.4 million and $39.4 million, respectively, in separate accounts, which are not restricted as to their use. The Company recognized gains of approximately $2.4 million and $2.2 million on its investments in the accounts associated with the Company’s deferred compensation plans during the three months ended September 30, 2025 and September 30, 2024, respectively, and approximately $4.6 million and $4.8 million during the nine months ended September 30, 2025 and September 30, 2024, respectively, primarily due to the observable change in fair value. Reclassification Certain prior year amounts have been reclassified to conform to the current year presentation.

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- Definition The entire disclosure for the basis of presentation and significant accounting policies concepts. Basis of presentation describes the underlying basis used to prepare the financial statements (for example, US Generally Accepted Accounting Principles, Other Comprehensive Basis of Accounting, IFRS). Accounting policies describe all significant accounting policies of the reporting entity. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 235 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147483426/235-10-50-1 + Details
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