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Basis Of Presentation And Summary Of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2018 | Jun. 30, 2017 | Jun. 30, 2018 | Jun. 30, 2017
Entity Information [Line Items] |  |  |  |
Payroll and related costs from management services contracts | $ 1,970 | $ 0 | $ 4,855 | $ 0
Direct reimbursements of payroll and related costs from management services contracts | 1,970 | 0 | 4,855 | 0
Net Cash Provided by (Used in) Operating Activities |  |  | 560,846 | 364,809
Cumulative effect of a change in accounting principle |  |  | 5,496 | (2,035)
Net Cash Provided by (Used in) Investing Activities |  |  | 485,801 | 547,678
Net Cash Provided by (Used in) Financing Activities |  |  | (146,646) | (302,561)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect |  |  | (221,691) | (119,692)
Interest Expense | 92,204 | 95,143 | 182,424 | 190,677
Boston Properties Limited Partnership |  |  |  |
Entity Information [Line Items] |  |  |  |
Payroll and related costs from management services contracts | 1,970 | 0 | 4,855 | 0
Direct reimbursements of payroll and related costs from management services contracts | 1,970 | 0 | 4,855 | 0
Net Cash Provided by (Used in) Operating Activities |  |  | 560,846 | 364,809
Cumulative effect of a change in accounting principle |  |  | 4,933 | (272)
Net Cash Provided by (Used in) Investing Activities |  |  | 485,801 | 547,678
Net Cash Provided by (Used in) Financing Activities |  |  | (146,646) | (302,561)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect |  |  | (221,691) | (119,692)
Interest Expense | 92,204 | $ 95,143 | 182,424 | 190,677
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 | 2,000 |  | 4,900 |
Direct reimbursements of payroll and related costs from management services contracts | 2,000 |  | 4,900 |
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 |  |  |  | (7,500)
Net Cash Provided by (Used in) Investing Activities |  |  |  | 8,200
Net Cash Provided by (Used in) Financing Activities |  |  |  | 100
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect |  |  |  | $ 15,800
Accounting Standards Update 2017-12 [Member] |  |  |  |
Entity Information [Line Items] |  |  |  |
Interest Expense | $ 1,700 |  |  |

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