Debt Of The Operating Partnership (Global Revolving Credit Facility) (Narrative) (Details)	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2012 Global Revolving Credit Facility [Member] USD ($)	Dec. 31, 2011 Global Revolving Credit Facility [Member] USD ($)	Nov. 03, 2011 Global Revolving Credit Facility [Member] USD ($)	Mar. 31, 2012 USD [Member] Global Revolving Credit Facility [Member] USD ($)	Dec. 31, 2011 USD [Member] Global Revolving Credit Facility [Member] USD ($)	Mar. 31, 2012 EUR [Member] Global Revolving Credit Facility [Member] EUR (€)		Mar. 31, 2012 GBP [Member] Global Revolving Credit Facility [Member] GBP (£)		Dec. 31, 2011 GBP [Member] Global Revolving Credit Facility [Member] GBP (£)		Mar. 31, 2012 SGD [Member] Global Revolving Credit Facility [Member] SGD		Dec. 31, 2011 SGD [Member] Global Revolving Credit Facility [Member] SGD		Mar. 31, 2012 AUD [Member] Global Revolving Credit Facility [Member] AUD		Dec. 31, 2011 AUD [Member] Global Revolving Credit Facility [Member] AUD		Mar. 31, 2012 HKD [Member] Global Revolving Credit Facility [Member] HKD
Debt of the Operating Partnership [Line Items]
Revolving credit facility borrowing capacity		$ 1,500,000,000		$ 850,000,000
Revolving credit facility commitments extension (years)	1
Revolving credit facility basis spread on variable rate		125
Basis rate for unused portion of the credit facility		25
Blended interest rate					1.50%		1.72%		1.98%				1.56%				5.67%				1.55%
Revolving credit facility maturity date		November 2015
Line of credit facility interest rate description		As of March 31, 2012, borrowings under the global revolving credit facility bore interest at a blended rate of 1.50% (U.S), 1.72% (Euro), 1.98% (GBP), 1.56% (Singapore Dollars), 5.67% (Australian Dollars) and 1.55% (Hong Kong Dollars), which are based on 1-month LIBOR, 1-month EURIBOR, 1-month GBP LIBOR, 1-month SIBOR, 1-month BBR and 1-month HIBOR, respectively, plus a margin of 1.25%.
Capitalized financing costs related to global revolving facilities		10,200,000
Letter of credit security amount		23,000,000
Principal outstanding		$ 678,554,000	$ 275,106,000		$ 498,000,000	$ 194,000,000	€ 65,914,000	[1]	£ 51,386,000	[1]	£ 49,892,000	[2]	44,923,000	[1]	28,151,000	[2]	14,484,000	[1]	3,063,000	[2]	3,847,000	[1]

[1] Based on exchange rates of $1.33 to €1.00, $1.60 to £1.00, $0.80 to 1.00 SGD, $1.03 to 1.00 AUD and $0.13 to 1.00 HKD, respectively, as of March 31, 2012.

[2] Based on exchange rates of $1.55 to £1.00, $0.77 to 1.00 SGD and $1.02 to 1.00 AUD, respectively, as of December 31, 2011.