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Noncontrolling Interests (Narrative) (Details) - USD ($) $ in Thousands | Sep. 30, 2021 | Dec. 31, 2020
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Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items] |  |
Noncontrolling Interest in Limited Partnerships | $ 1,728,101 | $ 1,726,933
Boston Properties Limited Partnership | OP Units [Member] |  |
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items] |  |
Noncontrolling Interest, Outstanding | 15,989,304 |
Boston Properties Limited Partnership | LTIP Units [Member] |  |
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items] |  |
Noncontrolling Interest, Outstanding | 1,487,492 |
Boston Properties Limited Partnership | 2012 OPP and 2013-2018 MYLTIP |  |
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items] |  |
Noncontrolling Interest, Outstanding | 419,423 |
Boston Properties Limited Partnership | MYLTIP 2019 [Member] |  |
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items] |  |
Noncontrolling Interest, Outstanding | 219,916 |
Boston Properties Limited Partnership | MYLTIP 2020 [Member] |  |
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items] |  |
Noncontrolling Interest, Outstanding | 203,278 |
Boston Properties Limited Partnership | MYLTIP 2021 |  |
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items] |  |
Noncontrolling Interest, Outstanding | 352,021 |

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