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Summary Of Significant Accounting Policies (Narrative) (Details) |  | 12 Months Ended
--- | --- | ---
Jul. 31, 2015 yr | Dec. 31, 2015 USD ($) yr | Dec. 31, 2014 USD ($) | Dec. 31, 2013 USD ($)
Entity Information [Line Items] |  |  |  |
Probable Sale Term of Property After Classified As Held For Sale (Years) | yr |  | 1 |  |
Maximum Period After Construction The Company Considers A Construction Project As Substantially Completed (In Years) | yr |  | 1 |  |
Interest costs capitalized |  | $ 34,213,000 | $ 52,476,000 | $ 68,152,000
Salaries And Related Costs Capitalized |  | 10,400,000 | 8,500,000 | 7,700,000
Cash FDIC Insured Limit |  | 250,000 |  |
Separate Unrestricted Cash For Deferred Compensation Plan. |  | 20,400,000 | 19,500,000 |
Gains (losses) from investments in securities |  | (653,000) | 1,038,000 | 2,911,000
Internal Leasing Salaries And Related Costs Capitalized |  | 5,500,000 | 6,000,000 | 5,100,000
Straight-line rent adjustments |  | (80,000,000) | (63,100,000) | (65,800,000)
Above and below market rent adjustments, net |  | $ 35,900,000 | 48,300,000 | 28,000,000
Ground Lease Expiration Date, Maximum |  | 2114 |  |
REIT Annual Taxable Income Distribution Requirement Percentage, Minimum |  | 90.00% |  |
Boston Properties Limited Partnership [Member] |  |  |  |
Entity Information [Line Items] |  |  |  |
Interest costs capitalized |  | $ 34,213,000 | 52,476,000 | 68,152,000
Gains (losses) from investments in securities |  | (653,000) | 1,038,000 | $ 2,911,000
Net Difference Between Tax Basis And Company's Assets And Liabilities. |  | $ 2,600,000,000 | 1,400,000,000 |
Boston Properties, Inc. [Member] |  |  |  |
Entity Information [Line Items] |  |  |  |
Company Annual Taxable Income Distribution Percentage |  | 100.00% |  |
Net Difference Between Tax Basis And Company's Assets And Liabilities. |  | $ 1,600,000,000 | $ 2,200,000,000 |
Clarendon Garage [Member] |  |  |  |
Entity Information [Line Items] |  |  |  |
Ground Lease Term (in years) | yr | 99 | 99 |  |
Operating Leases, Future Minimum Payments Due |  | $ 28,900,000 |  |

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