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