Debt Of The Operating Partnership (Revolving Credit Facility) (Details) In Thousands, unless otherwise specified			12 Months Ended							12 Months Ended																		12 Months Ended
	Dec. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)	Dec. 31, 2011 Revolving Credit Facility [Member] USD ($) years	Dec. 31, 2011 Global Revolving Credit Facility [Member] USD ($)		Dec. 31, 2011 Corporate Revolving Credit Facility [Member]		Dec. 31, 2010 Corporate Revolving Credit Facility [Member] USD ($)		Dec. 31, 2011 Asia Pacific Revolving Credit Facility [Member]		Dec. 31, 2011 USD [Member] Global Revolving Credit Facility [Member] USD ($)	Dec. 31, 2010 USD [Member] Corporate Revolving Credit Facility [Member] USD ($)	Dec. 31, 2011 Euro [Member]	Dec. 31, 2010 Euro [Member]	Dec. 31, 2011 British Sterling [Member]	Dec. 31, 2010 British Sterling [Member]	Dec. 31, 2011 British Sterling [Member] Global Revolving Credit Facility [Member] GBP (£)		Dec. 31, 2010 British Sterling [Member] Corporate Revolving Credit Facility [Member] GBP (£)		Dec. 31, 2011 SGD [Member]	Dec. 31, 2011 SGD [Member] Global Revolving Credit Facility [Member] SGD		Dec. 31, 2011 AUD [Member]	Dec. 31, 2011 AUD [Member] Global Revolving Credit Facility [Member] AUD		Dec. 31, 2011 US LIBOR, EURIBOR and GBP LIBOR [Member] Revolving Credit Facility [Member]	Dec. 31, 2011 SIBOR And BBR [Member] Asia Pacific Revolving Credit Facility [Member]
Debt of the Operating Partnership [Line Items]
Maturity date				Nov. 03, 2015		Aug. 31, 2012	[1]			Aug. 17, 2012	[1]
Balance/Principal Outstanding	$ 275,106	$ 333,534	$ 275,100	$ 275,106	[2]			$ 333,534	[1],[3]			$ 194,000	$ 312,500					£ 49,892	[4]	£ 21,034	[5]		28,151	[4]		3,063	[4]
Revolving credit facility, basis spread on variable rate				125 basis points
Line of credit facility interest rate calculation maturity range minimum (months)																												1	1
Line of credit facility interest rate calculation maturity range maximum (months)																												6	6
Line of credit facility interest rate calculation margin range minimum										1.20%																		1.10%
Line of credit facility interest rate calculation margin range maximum										1.75%																		2.00%
Revolving credit facility rate calculation federal funds rate per annum						1
Revolving credit facility rate calculation federal funds rate margin minimum			0.10%
Revolving credit facility rate calculation federal funds rate margin maximum			1.00%
Fee incurred for unused portion of credit facility minimum percentage						0.125%				0.25%
Fee incurred for unused portion of credit facility maximum percentage						0.20%				0.50%
Revolving credit facility commitments extension (years)			1
Weighted-average interest rate	1.67%	1.42%										1.54%	1.40%					1.99%		1.69%			1.56%			5.89%
Exchange rate														1.30	1.34	1.55	1.56					0.77			1.02
Global Revolving credit facilities	$ 275,106	$ 333,534		$ 275,106
Revolving credit facilities interest rates				Various	[6]	Various	[1]			Various	[1]

[1] On November 3, 2011, the Operating Partnership replaced its corporate and Asia Pacific revolving credit facilities with an expanded global revolving credit facility. The interest rate for borrowings under our corporate revolving credit facility equaled, at our election, either (i) US LIBOR, EURIBOR and GBP LIBOR (ranging from 1- to 6-month maturities) plus a margin of between 1.10% and 2.00% or (ii) the greater of (x) the base rate announced by the lender and (y) 1/2 of 1% per annum above the federal funds rate, plus a margin of between 0.100%—1.000%. In each case, the margin was based on our total leverage ratio. We incurred a fee ranging from 0.125% to 0.20% for the unused portion of our corporate revolving credit facility. The interest rate for borrowings under our Asia Pacific revolving credit facility equaled SIBOR or BBR (ranging from 1- to 6-month maturities) plus a margin of between 1.20% and 1.75%. We incurred a fee ranging from 0.25% to 0.50% for the unused portion of our Asia Pacific revolving credit facility.

[2] (2) Balances as of December 31, 2011 are as follows (balances, in thousands): Denomination of Draw Balance as ofDecember 31,2011 Weighted-averageinterest rate US ($) $ 194,000 1.54 % British Sterling (£) 49,892 (a) 1.99 % Singapore Dollar (SGD) 28,151 (a) 1.56 % Australian Dollar (AUD) 3,063 (a) 5.89 % Total $ 275,106 1.67 % (a) 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.

[3] (4) Balances as of December 31, 2010 are as follows (balances, in thousands): Denomination of Draw Balance as ofDecember 31,2010 Weighted-averageinterest rate US ($) $ 312,500 1.40 % Euro (€) — — British Sterling (£) 21,034 (a) 1.69 % Total $ 333,534 1.42 % (a) Based on exchange rate of $1.56 to £1.00 as of December 31, 2010.

[4] 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.

[5] Based on exchange rate of $1.56 to £1.00 as of December 31, 2010.

[6] The interest rate for borrowings under the global revolving credit facility equals the applicable index plus a margin which is based on the credit rating of our long-term debt and is currently 125 basis points. An annual facility fee on the unused portion of the facility, based on the credit rating of our long-term debt and currently 25 basis points, is payable quarterly.