Senior Unsecured Notes (Summary Of Senior Unsecured Notes) (Details) (USD $)
In Thousands, unless otherwise specified |
12 Months Ended | |||||||
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Dec. 31, 2011
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Dec. 31, 2010
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Long-Term Debt [Line Items] | ||||||||
Senior Unsecured Notes | $ 1,119,267 | $ 1,118,451 | ||||||
5.250% Senior Unsecured Notes, Due January 15, 2012 [Member]
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Long-Term Debt [Line Items] | ||||||||
Senior Unsecured Notes | 99,988 | [1] | 99,793 | [1] | ||||
Effective Rate | 5.457% | [1],[2] | ||||||
Interest rate of the Senior Unsecured Notes | 5.25% | [1] | ||||||
Maturity date of the Senior Unsecured Notes | Jan. 15, 2012 | [1] | ||||||
6.150% Senior Unsecured Notes, Due December 15, 2012 [Member]
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Long-Term Debt [Line Items] | ||||||||
Senior Unsecured Notes | 94,438 | 93,946 | ||||||
Effective Rate | 6.894% | [2] | ||||||
Interest rate of the Senior Unsecured Notes | 6.15% | |||||||
Maturity date of the Senior Unsecured Notes | Dec. 15, 2012 | |||||||
5.820% Senior Unsecured Notes, Due March 15, 2013 [Member]
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Long-Term Debt [Line Items] | ||||||||
Senior Unsecured Notes | 25,972 | 25,861 | ||||||
Effective Rate | 6.448% | [2] | ||||||
Interest rate of the Senior Unsecured Notes | 5.82% | |||||||
Maturity date of the Senior Unsecured Notes | Mar. 15, 2013 | |||||||
4.600% Senior Unsecured Notes, Due June 15, 2013 [Member]
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Long-Term Debt [Line Items] | ||||||||
Senior Unsecured Notes | 99,958 | 99,930 | ||||||
Effective Rate | 4.742% | [2] | ||||||
Interest rate of the Senior Unsecured Notes | 4.60% | |||||||
Maturity date of the Senior Unsecured Notes | Jun. 15, 2013 | |||||||
5.125% Senior Unsecured Notes, Due February 15, 2014 [Member]
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Long-Term Debt [Line Items] | ||||||||
Senior Unsecured Notes | 200,509 | 200,749 | ||||||
Effective Rate | 5.11% | [2] | ||||||
Interest rate of the Senior Unsecured Notes | 5.125% | |||||||
Maturity date of the Senior Unsecured Notes | Feb. 15, 2014 | |||||||
5.125% Senior Unsecured Notes, Due January 15, 2015 [Member]
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Long-Term Debt [Line Items] | ||||||||
Senior Unsecured Notes | 149,717 | 149,625 | ||||||
Effective Rate | 5.297% | [2] | ||||||
Interest rate of the Senior Unsecured Notes | 5.125% | |||||||
Maturity date of the Senior Unsecured Notes | Jan. 15, 2015 | |||||||
5.800% Senior Unsecured Notes, Due January 15, 2016 [Member]
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Long-Term Debt [Line Items] | ||||||||
Senior Unsecured Notes | 200,313 | 200,389 | ||||||
Effective Rate | 5.806% | [2] | ||||||
Interest rate of the Senior Unsecured Notes | 5.80% | |||||||
Maturity date of the Senior Unsecured Notes | Jan. 15, 2016 | |||||||
7.750% Senior Unsecured Notes, Due August 15, 2019 [Member]
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Long-Term Debt [Line Items] | ||||||||
Senior Unsecured Notes | $ 248,372 | $ 248,158 | ||||||
Effective Rate | 8.017% | [2] | ||||||
Interest rate of the Senior Unsecured Notes | 7.75% | |||||||
Maturity date of the Senior Unsecured Notes | Aug. 15, 2019 | |||||||
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