Summary Of Significant Accounting Policies (Narrative) (Details)	12 Months Ended
	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