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Senior, Senior Subordinated, Convertible Senior Notes (Details Textual) (USD $)
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12 Months Ended | 12 Months Ended | ||||||||||||||||||||
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Dec. 31, 2013
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Dec. 31, 2012
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Dec. 31, 2011
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Dec. 31, 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, 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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Apr. 30, 2012
7.731% senior subordinated notes due 2017 [Member]
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Dec. 31, 2013
Senior Notes Due Two Thousand Eighteen [Member] [Domain]
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Dec. 31, 2012
Senior Notes Due Two Thousand Eighteen [Member] [Domain]
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Dec. 31, 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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Apr. 30, 2012
7.00% senior notes due 2022 [Member]
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Dec. 31, 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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Dec. 31, 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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Dec. 31, 2013
Revolving Credit Facility [Member]
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Dec. 31, 2012
Revolving Credit Facility [Member]
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Jul. 24, 2012
Revolving Credit Facility [Member]
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Dec. 31, 2013
Consolidated EBITDA [Member]
Revolving Credit Facility [Member]
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Dec. 31, 2013
Consolidated Interest Incurred [Member]
Revolving Credit Facility [Member]
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| Debt Instrument [Line Items] | ||||||||||||||||||||||
| Debt instrument, stated rate | 6.25% | 7.731% | 7.731% | 4.50% | 7.00% | 7.00% | 7.15% | 7.15% | 1.875% | 1.88% | ||||||||||||
| Debt Instrument, Unamortized Premium | $ 3,555,000 | |||||||||||||||||||||
| Percentage of wholly owned subsidiary | 100.00% | |||||||||||||||||||||
| Add-on to existing 7.15% senior notes due 2020 | 100,000,000 | |||||||||||||||||||||
| Aggregate principal amount of offering | 175,000,000 | 300,000,000 | ||||||||||||||||||||
| Aggregate principal amount repurchased | 285,000,000 | 99,800,000 | 26,100,000 | |||||||||||||||||||
| Loss on early extinguishment of debt | (3,796,000) | (5,772,000) | 0 | |||||||||||||||||||
| Senior, senior subordinated and convertible notes | 905,055,000 | 722,797,000 | 0 | 99,825,000 | 175,000,000 | 0 | 300,000,000 | 300,000,000 | 303,555,000 | 196,472,000 | 126,500,000 | 126,500,000 | ||||||||||
| Line of credit facility, maximum borrowing capacity | 200,000,000 | 125,000,000 | ||||||||||||||||||||
| Available for issuance | 120,000,000 | |||||||||||||||||||||
| Minimum net worth required for compliance | 360,000,000 | |||||||||||||||||||||
| Leverage ratio | 60.00% | |||||||||||||||||||||
| Interest coverage ratio | 1.50 | 1.00 | ||||||||||||||||||||
| Letters of Credit Outstanding, Amount | 42,068,000 | 37,466,000 | ||||||||||||||||||||
| Line of Credit Facility, Remaining Borrowing Capacity | 157,900,000 | |||||||||||||||||||||
| Line of credit facility, amount outstanding | 0 | 0 | ||||||||||||||||||||
| Senior notes unamortized discount | 3,528,000 | |||||||||||||||||||||
| Year in which senior and senior subordinated notes due | 2015 | 2017 | 2018 | 2022 | 2020 | 2020 | 2032 | 2032 | 2016 | |||||||||||||
| Percent of debt instrument par value issued | 106.699% | |||||||||||||||||||||
| Debt Instrument, Interest Rate, Effective Percentage | 6.00% | |||||||||||||||||||||
| Debt instrument, convertible, conversion ratio | 17.1985 | |||||||||||||||||||||
| Conversion Principal Amount | 1,000 | |||||||||||||||||||||
| Debt instrument, convertible, conversion price | $ 58.14 | |||||||||||||||||||||
| Conversion premium | 47.50% | |||||||||||||||||||||
| Restricted Cash and Cash Equivalents | $ 0 | $ 38,938,000 | ||||||||||||||||||||