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Senior, Senior Subordinated, Convertible Senior Notes (Details Textual) (USD $)
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3 Months Ended | 9 Months Ended | ||||||||||||||||
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Sep. 30, 2013
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Sep. 30, 2012
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Sep. 30, 2013
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Sep. 30, 2012
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Sep. 30, 2013
7.731% senior subordinated notes due 2017 [Member]
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Dec. 31, 2012
7.731% senior subordinated notes due 2017 [Member]
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Sep. 30, 2013
4.50% senior notes due two thousand eighteen [Member]
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Sep. 30, 2013
7.00% senior notes due 2022 [Member]
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Dec. 31, 2012
7.00% senior notes due 2022 [Member]
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Sep. 30, 2013
7.15% senior notes due 2020 [Member]
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Dec. 31, 2012
7.15% senior notes due 2020 [Member]
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Sep. 30, 2013
1.875% convertible senior notes due 2032 [Member]
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Dec. 31, 2012
1.875% convertible senior notes due 2032 [Member]
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Sep. 30, 2013
Revolving Credit Facility [Member]
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Dec. 31, 2012
Revolving Credit Facility [Member]
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Sep. 30, 2013
Credit Facility Accordion Feature [Member]
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Sep. 30, 2013
Consolidated EBITDA [Member]
Revolving Credit Facility [Member]
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Sep. 30, 2013
Consolidated Interest Incurred [Member]
Revolving Credit Facility [Member]
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| Debt Instrument [Line Items] | ||||||||||||||||||
| Line of credit facility, maximum borrowing capacity | $ 135,000,000 | $ 135,000,000 | $ 75,000,000 | |||||||||||||||
| Minimum net worth required for compliance | 360,000,000 | |||||||||||||||||
| Leverage ratio | 60.00% | |||||||||||||||||
| Interest coverage ratio | 1.50 | 1.00 | ||||||||||||||||
| Line of credit facility, amount outstanding | 0 | 0 | 0 | 0 | ||||||||||||||
| Debt instrument, stated rate | 7.731% | 4.50% | 7.00% | 7.15% | 1.875% | |||||||||||||
| Percentage of wholly owned subsidiary | 100.00% | 100.00% | ||||||||||||||||
| Senior notes unamortized discount | 3,162,900 | 3,528,000 | ||||||||||||||||
| Year in which senior and senior subordinated notes due | 2017 | 2017 | 2018 | 2022 | 2022 | 2020 | 2020 | 2032 | 2032 | |||||||||
| Aggregate principal amount of offering | 175,000,000 | |||||||||||||||||
| Aggregate principal amount repurchased | 99,800,000 | |||||||||||||||||
| Senior and Senior Subordinated Notes (Textual) [Abstract] | ||||||||||||||||||
| Loss on early extinguishment of debt | $ 0 | $ 0 | $ 3,796,000 | $ 5,772,000 | ||||||||||||||