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Fair Value of Financial Instruments - Fair Values and Related Carrying Values of Debt Instruments (Detail) (USD $)
In Thousands, unless otherwise specified |
Sep. 30, 2013
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Dec. 31, 2012
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Dec. 31, 2011
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|---|---|---|---|
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Carrying Amount [Member]
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| Long-term Debt | |||
| Long term debt Fair value | $ 650,000 | $ 425,000 | $ 425,000 |
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Carrying Amount [Member] | 9.125% Senior Notes, due April 2018 ( issued march 22, 2010) [Member]
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| Long-term Debt | |||
| Long term debt Fair value | 300,000 | 300,000 | |
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Carrying Amount [Member] | 9.125% Senior Notes, due April 2018 (Issued April 25, 2012) [Member]
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| Long-term Debt | |||
| Long term debt Fair value | 125,000 | ||
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Carrying Amount [Member] | 2.125% Convertible Senior Notes due July 2012 [Member]
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| Long-term Debt | |||
| Long term debt Fair value | 0 | 125,000 | |
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Carrying Amount [Member] | 7.50% Senior Notes, due August 2020 [Member]
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| Long-term Debt | |||
| Long term debt Fair value | 225,000 | 0 | |
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Carrying Amount [Member] | 9.125% Senior Notes, due April 2018 [Member]
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| Long-term Debt | |||
| Long term debt Fair value | 425,000 | 425,000 | |
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Fair Value [Member]
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| Long-term Debt | |||
| Long term debt Fair value | 679,750 | 453,688 | 438,204 |
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Fair Value [Member] | 9.125% Senior Notes, due April 2018 ( issued march 22, 2010) [Member]
|
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| Long-term Debt | |||
| Long term debt Fair value | 320,250 | 315,000 | |
|
Fair Value [Member] | 9.125% Senior Notes, due April 2018 (Issued April 25, 2012) [Member]
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| Long-term Debt | |||
| Long term debt Fair value | 133,438 | ||
|
Fair Value [Member] | 2.125% Convertible Senior Notes due July 2012 [Member]
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| Long-term Debt | |||
| Long term debt Fair value | 0 | 123,204 | |
|
Fair Value [Member] | 7.50% Senior Notes, due August 2020 [Member]
|
|||
| Long-term Debt | |||
| Long term debt Fair value | 225,000 | 0 | |
|
Fair Value [Member] | 9.125% Senior Notes, due April 2018 [Member]
|
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| Long-term Debt | |||
| Long term debt Fair value | $ 454,750 | $ 453,688 |