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Summary Of Significant Accounting Policies (Narrative) (Details) | 12 Months Ended
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Dec. 31, 2016 USD ($) yr | Dec. 31, 2015 USD ($) | Dec. 31, 2014 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 | $ 39,237,000 | $ 34,213,000 | $ 52,476,000
Salaries And Related Costs Capitalized | 11,100,000 | 10,400,000 | 8,500,000
Cash FDIC Insured Limit | 250,000 |  |
Separate Unrestricted Cash For Deferred Compensation Plan. | 23,800,000 | 20,400,000 |
Gains (losses) from investments in securities | 2,273,000 | (653,000) | 1,038,000
Internal Leasing Salaries And Related Costs Capitalized | 7,200,000 | 5,500,000 | 6,000,000
Straight-line rent adjustments | (31,700,000) | (80,000,000) | (63,100,000)
Above and below market rent adjustments, net | $ 30,200,000 | 35,900,000 | 48,300,000
Ground Lease Expiration Date, Maximum | 2114 |  |
REIT Annual Taxable Income Distribution Requirement Percentage, Minimum | 90.00% |  |
Company Annual Taxable Income Distribution Percentage | 100.00% |  |
Net Difference Between Tax Basis And Company's Assets And Liabilities. | $ 1,700,000,000 | 1,600,000,000 |
Deferred Finance Costs, Net | 2,358,000 |  |
Boston Properties Limited Partnership |  |  |
Entity Information [Line Items] |  |  |
Interest costs capitalized | 39,237,000 | 34,213,000 | 52,476,000
Gains (losses) from investments in securities | 2,273,000 | (653,000) | $ 1,038,000
Net Difference Between Tax Basis And Company's Assets And Liabilities. | 2,700,000,000 | 2,600,000,000 |
Deferred Finance Costs, Net | (2,400,000) |  |
Mortgages [Member] |  |  |
Entity Information [Line Items] |  |  |
Deferred Finance Costs, Net | 2,400,000 | 3,500,000 |
Unsecured Debt [Member] |  |  |
Entity Information [Line Items] |  |  |
Deferred Finance Costs, Net | 35,300,000 | 24,500,000 |
Line of Credit [Member] |  |  |
Entity Information [Line Items] |  |  |
Deferred Finance Costs, Net | $ 1,900,000 | $ 3,100,000 |

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