Summary of Significant Accounting Policies (Details 2) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012 property	Dec. 31, 2011	Dec. 31, 2010
Real Estate Properties
Net reductions to rental income from amortization of capitalized above market and below market leases	$ 9,661	$ 7,764	$ 4,931
Net reductions to income from discontinued operations from amortization of capitalized above market and below market leases	301	716	2,517
Amortization included in depreciation and amortization	49,668	38,128	21,761
Amortization included in income from discontinued operations	547	1,837	4,822
Future amortization of net intangible lease assets and liabilities
2013	62,892
2014	57,183
2015	50,750
2016	42,360
2017	33,674
Thereafter	111,593
Loss on asset impairment from discontinued operations	(168,632)	(7,319)	(99,315)
Number of properties impaired	58
Accrued environmental remediation costs	10,798	14,625
Other Assets, Net
Deferred financing fees	58,783	45,763
Accumulated amortization for deferred financing fees	21,623	16,108
Deferred leasing costs for properties held and used in operations	151,115	130,176
Accumulated amortization for deferred leasing costs for properties held and used in operations	49,652	44,974
Deferred leasing costs for properties held for sale	4,771
Accumulated amortization for deferred leasing costs for properties held for sale	2,110
Capitalized lease incentives	20,491	16,636
Accumulated amortization for capitalized lease incentives	3,828	1,692
Future amortization of deferred financing fees and leasing costs
Future amortization of deferred financing fees and leasing costs, in 2013	25,910
Future amortization of deferred financing fees and leasing costs, in 2014	24,242
Future amortization of deferred financing fees and leasing costs, in 2015	21,899
Future amortization of deferred financing fees and leasing costs, in 2016	16,219
Future amortization of deferred financing fees and leasing costs, in 2017	12,194
Future amortization of deferred financing fees and leasing costs, thereafter	38,159
Future amortization of capitalized lease incentives
Future amortization of capitalized lease incentives, in 2013	2,232
Future amortization of capitalized lease incentives, in 2014	2,186
Future amortization of capitalized lease incentives, in 2015	2,166
Future amortization of capitalized lease incentives, in 2016	2,147
Future amortization of capitalized lease incentives, in 2017	2,090
Future amortization of capitalized lease incentives, thereafter	5,842
Accounting Policy for Derivative Instruments
Fair value of derivative instrument	16,624	15,796
Income Taxes
Minimum percentage of likelihood of realization of tax benefits	50.00%
Foreign currency translation adjustments	17,071	11,009
Above market leases
Real Estate Properties
Capitalized leases for properties held and used in operations	190,402	173,909
Accumulated amortization of capitalized leases for properties held and used in operations	56,374	51,578
Capitalized leases for properties held for sale	1,191
Accumulated amortization of capitalized leases for properties held for sale	1,060
Below market leases
Real Estate Properties
Capitalized leases for properties held and used in operations	106,643	101,039
Accumulated amortization of capitalized leases for properties held and used in operations	37,339	30,860
Capitalized leases for properties held for sale	92
Accumulated amortization of capitalized leases for properties held for sale	71
In place leases
Real Estate Properties
Capitalized leases for properties held and used in operations	393,068	299,616
Accumulated amortization of capitalized leases for properties held and used in operations	99,340	78,030
Capitalized leases for properties held for sale	2,297
Accumulated amortization of capitalized leases for properties held for sale	$ 1,975