Subsequent Events (Details) (USD $)	12 Months Ended			12 Months Ended	0 Months Ended					0 Months Ended				12 Months Ended	0 Months Ended							0 Months Ended
	Dec. 31, 2010	Feb. 03, 2012	Dec. 31, 2011	Dec. 31, 2011 OPP Units Two Thousand And Eleven [Member] years days	Jan. 25, 2012 OPP Units Two Thousand And Twelve [Member] years	Feb. 03, 2012 Restricted Stock [Member]	Dec. 31, 2011 Restricted Stock [Member]	Dec. 31, 2010 Restricted Stock [Member]	Dec. 31, 2009 Restricted Stock [Member]	Feb. 20, 2012 2.875% Exchangeable Senior Notes [Member]	Feb. 15, 2012 2.875% Exchangeable Senior Notes [Member]	Jan. 10, 2012 2.875% Exchangeable Senior Notes [Member]	Nov. 09, 2011 2.875% Exchangeable Senior Notes [Member]	Dec. 31, 2011 2.875% Exchangeable Senior Notes [Member]	Jan. 12, 2011 Montvale Center [Member]	Jul. 05, 2011 12310 Sunrise Valley Drive [Member]	Jan. 03, 2012 12300 Sunrise Valley Drive [Member]	Feb. 10, 2012 453 Ravendale Avenue [Member]	Feb. 16, 2012 100 Federal Street [Member]	Feb. 13, 2012 Executive Vice President [Member] months years	Feb. 13, 2012 2011 Outperformance Award [Member] Executive Vice President [Member]	Feb. 13, 2012 For 2011 [Member] Executive Vice President [Member]
Subsequent Event [Line Items]
Stated interest rate												2.875%		2.875%
Debt instrument repurchase date by company												Feb. 15, 2012
Put Right expiration date												Feb. 08, 2012
Notes redemption date												Feb. 20, 2012
Debt instrument in connection with redemption last day to exchange notes												Feb. 16, 2012
Debt instrument redemption price percentage of principal										100.00%		100.00%
Principal Amount			$ 1,773,694,000											$ 576,194,000
Repayments of unsecured debt	700,000,000									333,459,000	242,735,000		50,200,000
Aggregate rewards of OPP awards, maximum cap				40,000,000	40,000,000
Performance measurement period, years				15	3
Measurement period for 2012 OPP Awards				February 1, 2011 to January 31, 2014	February 7, 2012 to February 6, 2015
Award additional vesting period, years				2	2
Aggregate value of 2012 OPP Awards					7,700,000
Amortization into earnings period, years					5
Maturity date														Feb. 15, 2037	Jun. 06, 2012
Debt Instrument, Debt Default, Accrued Interest Rate															9.93%
Shares issued	140,278,005		148,186,511			19,521	19,030	69,499	62,876
LTIP units issued		156,652
Non-qualified stock options issued		165,538	146,844
Cash payment related to resignation																				1,533,333
Cash bonus for 2011 as part of resignation agreement																						950,000
Consulting period, months																				2
Consulting fee, per month																				20,000
Accelerated share vesting with respect to LTIP units																				23,502
Accelerated share vesting with respect to stock options																				4,464
Accelerated share vesting with respect to common stock																				5,117
Common stock exercise price per share for stock options																				$ 92.71
Common stock exercise price per share for common stock																				$ 104.47
Percentage of outperformance award retained by Mr. Norville																					36.00%
Non-compete agreement, years																				1
Net rentable square footage																268,000	256,000	30,000	1,300,000
Acquisition aggregate purchase price																		6,700,000	615,000,000
Number of floors in building																			37
Earnest Money Deposits																			$ 25,000,000