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Stock Option and Incentive Plan (Narrative) (Details) - USD ($) $ in Millions | Feb. 06, 2020 | Feb. 04, 2020
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MYLTIP 2020 [Member] |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period |  | 4 years
TSR measurement (in years) |  | three-year
Minimum earned awards |  | 0
Maximum Earned Awards |  | 203,278
Earned wards - Target |  | 101,638
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights |  | Earned awards (if any) will vest 50% on February 3, 2023 and 50% on February 3, 2024, based on continued employment. 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 3, 2023, earned awards will be calculated based on TSR performance up to the date of the change of control. The 2020 MYLTIP awards are in the form of LTIP Units issued on the grant date which (i) are subject to forfeiture to the extent awards are not earned and (ii) prior to the performance measurement date are only entitled to one-tenth (10%) of the regular quarterly distributions payable on common partnership units.
Value of MYLTIP Awards |  | $ 13.7
MYLTIP 2017 [Member] |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Value of MYLTIP Awards | $ 17.6 |
Final awards percentage of target | 83.80% |
MYLTIP Units forfeited | 270,942 |

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- Definition Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901 + Details
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