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Summary Of Significant Accounting Policies (Narrative) (Details) - USD ($) | 12 Months Ended
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Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Summary Of Significant Accounting Policies [Line Items] |  |  |
Interest capitalized | $ 53,097,000 | $ 53,881,000 | $ 54,911,000
Salaries And Related Costs Capitalized | 13,700,000 | 12,900,000 | 10,400,000
Cash FDIC Insured Limit | 250,000 |  |
Separate Unrestricted Cash For Deferred Compensation Plan. | 43,600,000 | 39,500,000 |
Gains from investments in securities | 5,626,000 | 5,261,000 | 6,417,000
Straight Line Rent Adjustments | 104,300,000 | 104,900,000 | 58,400,000
Above and below market rent adjustments, net | 4,200,000 | 6,500,000 | 20,900,000
Impairment loss | 0 | 0 | 24,038,000
Boston Properties Limited Partnership |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |
Interest capitalized | 53,097,000 | 53,881,000 | 54,911,000
Gains from investments in securities | 5,626,000 | 5,261,000 | 6,417,000
Impairment loss | $ 0 | $ 0 | 22,272,000
one tower center |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |
Impairment loss |  |  | 24,000,000
one tower center | Boston Properties Limited Partnership |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |
Impairment loss |  |  | $ 22,300,000

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