Unsecured Debt (Details 2) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Aggregate maturities of unsecured debt
2011	$ 96,373
2012	104,385
2013	221,885
2014	311,930
2015	324,744
Thereafter	647,868
Unsecured Debt, Total	1,707,185	1,603,834
Bank Lines [Member]
Aggregate maturities of unsecured debt
2011	0
2012	5,000
2013	0
2014	0
2015	0
Thereafter	0
Unsecured Debt, Total	5,000
Senior Unsecured Notes [Member]
Aggregate maturities of unsecured debt
2011	96,373
2012	99,385
2013	221,885
2014	311,930
2015	324,744
Thereafter	647,868
Unsecured Debt, Total	$ 1,702,185

Maturities of unsecured debt.

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- Definition

Amount of unsecured debt maturities after year five following the date of the latest balance sheet presented in the financial statements.

+ Details

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- Definition

Amount of unsecured debt maturing within the next twelve months following the date of the latest balance sheet presented in the financial statements.

+ Details

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- Definition

Amount of unsecured debt maturing in year five following the date of the latest balance sheet presented in the financial statements.

+ Details

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- Definition

Amount of unsecured debt maturing in year four following the date of the latest balance sheet presented in the financial statements.

+ Details

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- Definition

Amount of unsecured debt maturing in year three following the date of the latest balance sheet presented in the financial statements.

+ Details

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- Definition

Amount of unsecured debt maturing in year two following the date of the latest balance sheet presented in the financial statements.

+ Details

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- Definition

Including the current and noncurrent portions, carrying value as of the balance sheet date of uncollateralized debt obligations (with maturities initially due after one year or beyond the operating cycle if longer).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 5
-Section 02
-Subsection 19, 20, 22

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 03
-Paragraph 16
-Article 9

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.16)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 4: 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

+ Details

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