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Stock Option and Incentive Plan (Narrative) (Details) - USD ($) $ in Millions | May 20, 2021 | Feb. 02, 2021
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MYLTIP 2021 |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Vesting Period |  | 3 years
Distributions percent before measurement date |  | 10.00%
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights |  | Earned awards (if any) will vest 100% on February 1, 2024, but may not be converted, redeemed, sold or otherwise transferred for one additional year thereafter. Vesting will be accelerated in the event of a change in control, termination of employment by Boston Properties, Inc. without cause, or termination of employment by the award recipient for good reason, death, disability or retirement. If there is a change of control prior to February 1, 2024, earned awards will be calculated based on TSR performance up to the date of the change of control.
Value of MYLTIP Awards |  | $ 15.3
Share-based Compensation Arrangement by Share-based Payment Award, Terms of Award |  | The 2021 MYLTIP awards consist of two, equally-weighted (50% each) components that utilize Boston Properties, Inc.’s TSR over a three-year measurement period as the performance metric. The first component of the 2021 MYLTIP, which represents one-half (50%) of the target grant-date value, retains the basic general structure of the 2020 MYLTIP awards with certain changes, including a change to the custom index against which Boston Properties, Inc.’s TSR is compared. The number of LTIP Units that can be earned under this component ranges from zero to 200% of the target number of LTIP Units, based on Boston Properties, Inc.’s annualized relative TSR performance compared to a custom index. Under this component, 100% of the target number of LTIP Units will be earned if Boston Properties, Inc.’s TSR equals the custom index TSR; for relative TSR performance between -1,000 basis points and +1,000 basis points, the number of LTIP Units earned will be determined using linear interpolation.The second component represents the remaining one-half (50%) of the target grant-date value of the 2021 MYLTIP. The number of LTIP Units that can be earned under this component ranges from zero to 200% of the target number of LTIP Units, based on Boston Properties, Inc.’s cumulative absolute TSR during the performance period. Under this component, 100% of the target number of LTIP Units will be earned if Boston Properties, Inc.’s achieves an absolute TSR equal to +1,000 basis points; if Boston Properties, Inc.’s absolute TSR is greater than -4,000 basis points but less than +6,000 basis points, then the number of LTIP Units earned will be determined using linear interpolation.
2021 Stock Incentive Plan |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Share-based Compensation Arrangement by Share-based Payment Award, Description | The material features of the 2021 Plan include, among other things: (i) the maximum number of shares of Common Stock reserved and available for issuance under the 2021 Plan is 5,400,000 shares less one share for every one share that was granted between March 4, 2021 and May 19, 2021 under the 2012 Plan, (ii) shares of Common Stock underlying awards granted under the 2021 Plan or the 2012 Plan that are forfeited, canceled or otherwise terminated (other than by exercise) will be added back to the shares of Common Stock available for issuance under the 2021 Plan and, with respect to “full-value” awards under the 2021 Plan or the 2012 Plan, shares tendered or held back for taxes and shares previously reserved for issuance pursuant to such an award to the extent that such shares are not issued and are no longer issuable pursuant to such an award (e.g., in the event that a full-value award that may be settled in cash or by issuance of shares of Common Stock is settled in cash) will be added back to the shares available for issuance under the 2021 Plan, (iii) the award of stock options (both incentive and non-qualified options), stock appreciation rights, restricted stock units, restricted stock, unrestricted stock, dividend equivalent rights, cash-based awards and other equity-based awards (including LTIP Units) is permitted, (iv) stock options may not be repriced and “underwater” stock options may not be exchanged for another award or cash without stockholder approval; and (v) the term of the 2021 Plan is for ten years from the date of stockholder approval. |
Minimum [Member] | MYLTIP 2021 |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Common stock available for issuance |  | 0
Maximum [Member] | MYLTIP 2021 | Boston Properties Limited Partnership |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Common stock available for issuance |  | 352,021
Target | MYLTIP 2021 |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Common stock available for issuance |  | 176,009

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