Real Estate (Summary of Real Estate Subject to Operating Leases) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Property Subject to or Available for Operating Lease [Line Items]
Real estate subject to operating leases, gross	$ 5,333,557	$ 5,199,682
Less accumulated depreciation and amortization	(538,435)	(511,667)
Real estate subject to operating leases before work in process	4,795,122	4,688,015
Accounted for using the operating method, net of accumulated depreciation and amortization	4,823,155us-gaap_RealEstateInvestmentPropertyNet	4,716,923us-gaap_RealEstateInvestmentPropertyNet
Land and improvements
Property Subject to or Available for Operating Lease [Line Items]
Land and improvements	1,816,363	1,783,822
Buildings and improvements
Property Subject to or Available for Operating Lease [Line Items]
Buildings and improvements	3,515,904	3,414,570
Leasehold interests
Property Subject to or Available for Operating Lease [Line Items]
Leasehold interests	1,290	1,290
Work in progress
Property Subject to or Available for Operating Lease [Line Items]
Work in progress	$ 28,033	$ 28,908

Aggregate carrying amounts as of the balance sheet date of investments in leasehold interests

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- Definition

Real Estate Subject To Operating Leases Before Work In Process

+ References

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- Definition

Real Estate Subject to Operating Leases, Gross

+ References

No definition available.

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- Definition

The current amount of expenditures for a real estate project that has not yet been completed.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.10)

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- Definition

Aggregate of the carrying amounts as of the balance sheet date of investments in building and building improvements.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

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- Definition

Amount before accumulated depletion of real estate held for productive use, excluding land held for sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

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- Definition

The amount of accumulated depreciation, by major property class, recorded on property subject to or available for lease as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 20

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-Paragraph 3

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- Definition

Amount of real estate investment property, net of accumulated depreciation, which may include the following: (1) land available-for-sale; (2) land available-for-development; (3) investments in building and building improvements; (4) tenant allowances; (5) developments in-process; (6) rental properties; and (7) other real estate investments.

+ References

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