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Summary Of Significant Accounting Policies (Narrative) (Details) $ / shares in Units, $ in Thousands | 3 Months Ended |  |
--- | --- | --- | ---
Mar. 31, 2021 USD ($) | Mar. 31, 2020 USD ($) | Mar. 18, 2021 $ / shares | Dec. 31, 2020 USD ($)
Summary Of Significant Accounting Policies [Line Items] |  |  |  |
Interest capitalized | $ 12,032 | $ 14,149 |  |
Gains (losses) from investments in securities | 1,659 | (5,445) |  |
Adoption of ASU 2016-13 and 2018-19 | (570,982) |  |  | $ (509,653)
Adoption of ASU 2016-13 and 2018-19 | $ 620,106 |  |  | 616,596
Number of VIEs - Total | 7 |  |  |
Number of VIEs | 6 |  |  |
Distributions Payable, Amount Per Unit | $ / shares |  |  | $ 0.98 |
Boston Properties Limited Partnership |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |
Interest capitalized | $ 12,032 | 14,149 |  |
Gains (losses) from investments in securities | 1,659 | $ (5,445) |  |
Adoption of ASU 2016-13 and 2018-19 | 4,392,624 |  |  | 4,554,639
Adoption of ASU 2016-13 and 2018-19 | $ 1,780,044 |  |  | $ 1,643,024
Distributions Payable, Amount Per Unit | $ / shares |  |  | $ 0.98 |
Commercial Real Estate Properties [Member] |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |
Number of VIEs | 5 |  |  |

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