Derivative and Other Fair Value Instruments (Details Textuals) (USD $)	6 Months Ended	12 Months Ended
Jun. 30, 2011	Dec. 31, 2010
Derivative and Other Fair Value Instruments (Textuals) [Abstract]
Total Debt	$ 4,352,372,000	$ 4,762,896,000
Notes, net	5,096,250,000	5,185,180,000
Fair value of the mortgage notes payable	4,400,000,000
Fair value of the unsecured notes payable	5,400,000,000
Forward starting swaps counterparty terminations designated for 2012 maturity	750,000,000
Forward starting swaps counterparty terminations designated for 2013 maturity	200,000,000
Deferred Gains In OCI	81,600,000	58,300,000
Estimated Future Losses In OCI	$ 4,300,000

Derivative and Other Fair Value Instruments.

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- Definition

Aggregate notional amount of derivatives designated as cash flow hedging instruments with mandatory counterparty terminations designated for year three maturity. The notional amount relates to a number of currency units, shares, bushels, pounds, or other units specified in a derivative instrument.

+ Details

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- Definition

Aggregate notional amount of derivatives designated as cash flow hedging instruments with mandatory counterparty terminations designated for year two maturity. The notional amount relates to a number of currency units, shares, bushels, pounds, or other units specified in a derivative instrument.

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- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-Subparagraph (a)
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-Section 50
-Paragraph 12
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- Definition

The estimated net amount of unrealized gains or losses on interest rate cash flow hedges as of the balance sheet date expected to be reclassified to earnings within the next twelve months.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 133
-Paragraph 45
-Subparagraph b(2)
-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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-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6887037&loc=d3e80748-113994

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- Definition

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

+ Details

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- Definition

Including the current and noncurrent portions, aggregate carrying amount of all types of notes payable, as of the balance sheet date, with initial maturities beyond one year or beyond the normal operating cycle, if longer.

+ 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 210.7-03.16)
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 19, 20, 22
-Article 5

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- Definition

Carrying value as of the balance sheet date , including the current and noncurrent portions, of collateralized debt obligations (with maturities initially due after one year or beyond the operating cycle, if longer). Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower.

+ 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 210.7-03.16)
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-Publisher SEC
-Name Regulation S-X (SX)
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-Publisher SEC
-Name Regulation S-X (SX)
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-Publisher FASB
-Name Accounting Standards Codification
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- Definition

Amount of unrealized gain (loss) related to the increase or decrease in fair value of interest rate derivatives designated as cash flow hedging instruments, which was recorded in accumulated other comprehensive income to the extent that the cash flow hedge was determined to be effective.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 133
-Paragraph 46
-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 Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6935481&loc=SL5624171-113959

+ Details

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