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Basis Of Presentation And Summary Of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2018 | Sep. 30, 2017 | Sep. 30, 2018 | Sep. 30, 2017
Entity Information [Line Items] |  |  |  |
Payroll and related costs from management services contracts | $ 2,516 | $ 0 | $ 7,371 | $ 0
Direct reimbursements of payroll and related costs from management services contracts | 2,516 | 0 | 7,371 | 0
Net Cash Provided by (Used in) Operating Activities |  |  | 770,627 | 584,965
Cumulative effect of a change in accounting principle |  |  | 5,496 | (2,035)
Net Cash Provided by (Used in) Investing Activities |  |  | 1,020,067 | 593,895
Net Cash Provided by (Used in) Financing Activities |  |  | 167,855 | 165,676
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect |  |  | (81,585) | 156,746
Interest Expense | 95,366 | 92,032 | 277,790 | 282,709
Boston Properties Limited Partnership |  |  |  |
Entity Information [Line Items] |  |  |  |
Payroll and related costs from management services contracts | 2,516 | 0 | 7,371 | 0
Direct reimbursements of payroll and related costs from management services contracts | 2,516 | 0 | 7,371 | 0
Net Cash Provided by (Used in) Operating Activities |  |  | 770,627 | 584,965
Cumulative effect of a change in accounting principle |  |  | 4,933 | (272)
Net Cash Provided by (Used in) Investing Activities |  |  | 1,020,067 | 593,895
Net Cash Provided by (Used in) Financing Activities |  |  | 167,855 | 165,676
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect |  |  | (81,585) | 156,746
Interest Expense | 95,366 | $ 92,032 | 277,790 | 282,709
Dividends In Excess Of Earnings [Member] |  |  |  |
Entity Information [Line Items] |  |  |  |
Cumulative effect of a change in accounting principle |  |  | 4,933 | (272)
Noncontrolling Interests [Member] |  |  |  |
Entity Information [Line Items] |  |  |  |
Cumulative effect of a change in accounting principle |  |  | 563 | (1,763)
Noncontrolling Interests [Member] | Boston Properties Limited Partnership |  |  |  |
Entity Information [Line Items] |  |  |  |
Cumulative effect of a change in accounting principle |  |  | 563 | (1,763)
Accounting Standards Update 2014-09 [Member] |  |  |  |
Entity Information [Line Items] |  |  |  |
Payroll and related costs from management services contracts | 2,500 |  | 7,400 |
Direct reimbursements of payroll and related costs from management services contracts | 2,500 |  | 7,400 |
Cumulative effect of a change in accounting principle |  |  | 4,900 |
Accounting Standards Update 2014-09 [Member] | Boston Properties Limited Partnership |  |  |  |
Entity Information [Line Items] |  |  |  |
Cumulative effect of a change in accounting principle |  |  | 4,900 |
Accounting Standards Update 2014-09 [Member] | Noncontrolling Interests [Member] |  |  |  |
Entity Information [Line Items] |  |  |  |
Cumulative effect of a change in accounting principle |  |  | 600 |
Accounting Standards Update 2014-09 [Member] | Noncontrolling Interests [Member] | Boston Properties Limited Partnership |  |  |  |
Entity Information [Line Items] |  |  |  |
Cumulative effect of a change in accounting principle |  |  | $ 600 |
Accounting Standards Update 2016-18 [Member] |  |  |  |
Entity Information [Line Items] |  |  |  |
Net Cash Provided by (Used in) Operating Activities |  |  |  | (7,700)
Net Cash Provided by (Used in) Investing Activities |  |  |  | 28,500
Net Cash Provided by (Used in) Financing Activities |  |  |  | (200)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect |  |  |  | $ (20,600)
Accounting Standards Update 2017-12 [Member] |  |  |  |
Entity Information [Line Items] |  |  |  |
Interest Expense | $ 1,700 |  |  |

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