Unsecured Exchangeable Senior Notes (Schedule Of Unsecured Exchangeable Senior Notes) (Detail) (USD $)			9 Months Ended			1 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2012 3.625% Exchangeable Senior Notes [Member]		Aug. 13, 2008 3.625% Exchangeable Senior Notes [Member]	Dec. 17, 2007 3.750% Exchangeable Senior Notes [Member]	Sep. 30, 2012 3.750% Exchangeable Senior Notes [Member]		Dec. 31, 2007 3.750% Exchangeable Senior Notes [Member]
Debt Instrument [Line Items]
3.625% Exchangeable Senior Notes	$ 1,197,500,000		$ 747,500,000				$ 450,000,000
Net unamortized discount	(2,012,000)	(3,462,000)
Adjustment for the equity component allocation, net of accumulated amortization	(32,533,000)
Total	1,162,955,000	1,715,685,000
Coupon/ Stated Rate			3.625%				3.75%
Effective Rate			4.037%	[1]			3.787%	[1]
Exchange Rate			8.5051	[2]			10.0066	[3]
First Optional Redemption Date by the Company							May 18, 2013	[4]
Maturity Date			Feb. 15, 2014				May 15, 2036
Initial exchange on principal amount of note			1,000						1,000
Initial exchange price per share			$ 117.58
Initial exchange rate			8.5051						9.3900
Revised exchange price due to capped call transaction			$ 137.17
Premium over closing price			40.00%
Closing price per share of common stock					$ 97.98
Effective exchange price			$ 134.77
Net cost of capped call transaction			$ 44,400,000
Special distribution per share common stock						$ 5.98
Revised exchange rate									10.0066
Revised exchange price resulting from special distribution									$ 99.93
Repurchase price for the notes							100.00%

[1] Yield on issuance date including the effects of discounts on the notes but excluding the effects of the adjustment for the equity component allocation.

[2] The initial exchange rate is 8.5051 shares per $1,000 principal amount of the notes (or an initial exchange price of approximately $117.58 per share of Boston Properties, Inc.'s common stock). In addition, the Company entered into capped call transactions with affiliates of certain of the initial purchasers, which are intended to reduce the potential dilution upon future exchange of the notes. The capped call transactions were intended to increase the effective exchange price to the Company of the notes from $117.58 to approximately $137.17 per share (subject to adjustment), representing an overall effective premium of approximately 40% over the closing price on August 13, 2008 of $97.98 per share of Boston Properties, Inc.'s common stock. The net cost of the capped call transactions was approximately $44.4 million. As of September 30, 2012, the effective exchange price was $134.77 per share.

[3] In connection with the special distribution of $5.98 per share of Boston Properties, Inc.'s common stock declared on December 17, 2007, the exchange rate was adjusted from 9.3900 to 10.0066 shares per $1,000 principal amount of notes effective as of December 31, 2007, resulting in an exchange price of approximately $99.93 per share of Boston Properties, Inc.'s common stock.

[4] Holders may require the Operating Partnership to repurchase the notes for cash on May 18, 2013 and on May 15 of 2016, 2021, 2026 and 2031 and at any time prior to their maturity upon a fundamental change, in each case at a price equal to 100% of the principal amount of the notes being repurchased plus any accrued and unpaid interest up to, but excluding, the repurchase date.