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Senior, Senior Subordinated, Convertible Senior Notes (Details Textual) (USD $)
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3 Months Ended | 9 Months Ended | 3 Months Ended | 9 Months Ended | 3 Months Ended | |||||||||||||||||
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Sep. 30, 2012
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Sep. 30, 2011
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Sep. 30, 2012
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Sep. 30, 2011
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Sep. 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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Sep. 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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Sep. 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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Sep. 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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Sep. 30, 2012
1.875% convertible senior notes due 2032 [Member]
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Sep. 30, 2012
1.875% convertible senior notes due 2032 [Member]
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Sep. 30, 2012
Revolving Credit Facility [Member]
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Dec. 31, 2011
Revolving Credit Facility [Member]
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Jan. 01, 2013
Consolidated EBITDA [Member]
Revolving Credit Facility [Member]
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Sep. 30, 2012
Consolidated EBITDA [Member]
Revolving Credit Facility [Member]
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Jan. 01, 2013
Consolidated Interest Incurred [Member]
Revolving Credit Facility [Member]
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Sep. 30, 2012
Consolidated Interest Incurred [Member]
Revolving Credit Facility [Member]
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| Debt Instrument [Line Items] | ||||||||||||||||||||||
| Line of credit facility, maximum borrowing capacity | $ 40,000,000 | $ 40,000,000 | $ 125,000,000 | |||||||||||||||||||
| Available for issuance | 50,000,000 | |||||||||||||||||||||
| Line of credit facility, expiration date | Jul. 24, 2015 | |||||||||||||||||||||
| Minimum net worth required for compliance | 360,000,000 | |||||||||||||||||||||
| Leverage ratio | 60.00% | |||||||||||||||||||||
| Interest coverage ratio | 1.50 | 1 | 1 | 1 | ||||||||||||||||||
| Line of credit facility, amount outstanding | 0 | 0 | ||||||||||||||||||||
| Debt instrument, stated rate | 6.25% | 6.25% | 7.731% | 7.731% | 7.00% | 7.15% | 7.15% | 1.875% | 1.875% | |||||||||||||
| Percentage of wholly owned subsidiary | 100.00% | 100.00% | ||||||||||||||||||||
| Senior notes unamortized discount | 451,000 | 3,650,000 | 4,015,000 | |||||||||||||||||||
| Year in which senior and senior subordinated notes due | 2015 | 2015 | 2017 | 2017 | 2022 | 2020 | 2020 | 2032 | 2032 | |||||||||||||
| Aggregate principal amount of offering | 300,000,000 | 126,500,000 | 126,500,000 | |||||||||||||||||||
| Aggregate principal amount repurchased | 285,000,000 | 26,100,000 | ||||||||||||||||||||
| Debt instrument, convertible, conversion ratio | 17.1985 | |||||||||||||||||||||
| Conversion principal amount | 1,000 | |||||||||||||||||||||
| Debt instrument, convertible, conversion price | $ 58.14 | $ 58.14 | ||||||||||||||||||||
| Senior and Senior Subordinated Notes (Textual) [Abstract] | ||||||||||||||||||||||
| Loss on extinguishment of debt | $ 0 | $ 0 | $ (5,772,000) | $ 0 | ||||||||||||||||||