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Senior and Senior Subordinated Notes (Details Textual) (USD $)
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3 Months Ended | 6 Months Ended | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
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Jun. 30, 2012
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Jun. 30, 2011
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Jun. 30, 2012
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Jun. 30, 2011
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Jun. 30, 2012
6.25% senior notes due 2015 [Member]
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Apr. 30, 2012
6.25% senior notes due 2015 [Member]
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Dec. 31, 2011
6.25% senior notes due 2015 [Member]
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Jun. 30, 2012
7.731% senior subordinated notes due 2017 [Member]
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Apr. 30, 2012
7.731% senior subordinated notes due 2017 [Member]
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Dec. 31, 2011
7.731% senior subordinated notes due 2017 [Member]
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Jun. 30, 2012
7.00% senior notes due 2022 [Member]
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Apr. 30, 2012
7.00% senior notes due 2022 [Member]
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Dec. 31, 2011
7.00% senior notes due 2022 [Member]
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Jun. 30, 2012
7.15% senior notes due 2020 [Member]
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Dec. 31, 2011
7.15% senior notes due 2020 [Member]
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| Debt Instrument [Line Items] | |||||||||||||||
| Debt instrument, Stated rate | 6.25% | 7.731% | 7.00% | 7.15% | |||||||||||
| Percentage of wholly owned subsidiary | 100.00% | 100.00% | |||||||||||||
| Senior notes unamortized discount | $ 451,000 | $ 3,771,000 | $ 4,015,000 | ||||||||||||
| Year in which senior and senior subordinated notes due | 2015 | 2015 | 2017 | 2017 | 2022 | 2020 | 2020 | ||||||||
| Aggregate principal amount of offering | 300,000,000 | ||||||||||||||
| Aggregate principal amount repurchased | 285,000,000 | 26,100,000 | |||||||||||||
| Senior and Senior Subordinated Notes (Textual) [Abstract] | |||||||||||||||
| Loss on extinguishment of debt | $ (5,772,000) | $ 0 | $ (5,772,000) | $ 0 | |||||||||||