Significant Acquisitions and Dispositions (Summary of Allocation of Fair Value of Amounts Recognized) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012 Other Two Thousand Twelve Acquisitions [Member] [Domain]	Dec. 31, 2011 Other 2011 Acquisitions [Member]	Dec. 31, 2011 Premier Portfolio [Member]	Apr. 04, 2011 Premier Portfolio [Member]	Dec. 31, 2010 Premier Portfolio [Member]	Dec. 31, 2010 Other 2010 Acquisitions [Member]	Jul. 01, 2010 Dugan Realty [Member]
Real estate assets	$ 668,149	$ 503,556	$ 403,616	$ 153,656	$ 249,960	$ 254,014	$ 502,418
Lease-related intangible assets	111,509	70,994	56,536	25,445	31,091	71,844	107,155
Other assets	5,714	879	4,372	2,571	1,801	3,652	28,658
Total acquired assets	785,372	575,429	464,524	181,672	282,852	329,510	638,231
Secured debt	100,826	40,072	283,241	125,003	158,238	63,458	285,376
Other liabilities	11,928	8,300	8,359	4,284	4,075	5,645	20,243
Total assumed liabilities	112,754	48,372	291,600	129,287	162,313	69,103	305,619
Fair value of acquired net assets	$ 672,618	$ 527,057	$ 172,924	$ 52,385	$ 120,539	$ 260,407	$ 332,612

The amount of acquisition cost of a business combination allocated to an identifiable intangible asset that will be amortized.

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The amount of acquisition cost of a business combination allocated to assets acquired.

+ References

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141

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The total purchase price of the acquired entity. This includes cash paid to equity interest holders of the acquired entity, fair value of debt and equity securities issued to equity holders of the acquired entity, and transaction costs paid to third parties to consummate the acquisition.

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The amount of acquisition cost of a business combination allocated to other current liabilities of the acquired entity. Does not include amounts allocated to the current portion of long-term debt, accounts payable and accrued expenses.

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The amount of acquisition cost of a business combination allocated to liabilities assumed.

+ References

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

-Publisher FASB

-Name Emerging Issues Task Force (EITF)

-Number 98-1

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

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The amount of acquisition cost of a business combination allocated to the noncurrent portion of the long-term debt assumed from the acquired entity.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141

-Paragraph 51

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Emerging Issues Task Force (EITF)

-Number 98-1

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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Amount of acquisition cost of a business combination allocated to other noncurrent assets not separately disclosed.

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-Publisher FASB

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-Number 141

-Paragraph 51

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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-Publisher FASB

-Name Emerging Issues Task Force (EITF)

-Number 98-1

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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The amount of acquisition cost of a business combination allocated to land and building to be used in the normal course of business, not including assets that are held-for-sale.

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