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Long-Term Debt - Summary of Company's Current Debt Portfolio (Parenthetical) (Detail) (USD $)
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12 Months Ended | 12 Months Ended | 12 Months Ended | 3 Months Ended | 12 Months Ended | 9 Months Ended | 9 Months Ended | 12 Months Ended | 12 Months Ended | ||||||||
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Dec. 31, 2012
9.125% Senior Notes, due April 2018 ( issued march 22, 2010) [Member]
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Dec. 31, 2011
9.125% Senior Notes, due April 2018 ( issued march 22, 2010) [Member]
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Mar. 22, 2010
9.125% Senior Notes, due April 2018 ( issued march 22, 2010) [Member]
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Dec. 31, 2012
9.125% Senior Notes, due April 2018 (Issued April 25, 2012) [Member]
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Dec. 31, 2011
9.125% Senior Notes, due April 2018 (Issued April 25, 2012) [Member]
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Apr. 25, 2012
9.125% Senior Notes, due April 2018 (Issued April 25, 2012) [Member]
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Dec. 31, 2012
2.125% Convertible Senior Notes, due July 2012 [Member]
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Dec. 31, 2011
2.125% Convertible Senior Notes, due July 2012 [Member]
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Dec. 31, 2012
Term Note [Member]
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Dec. 31, 2012
Term Note [Member]
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Dec. 31, 2011
Term Note [Member]
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Sep. 30, 2013
7.50% Senior Notes, due August 2020 [Member]
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Jul. 30, 2013
7.50% Senior Notes, due August 2020 [Member]
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Sep. 30, 2013
9.125% Senior Notes, due April 2018 [Member]
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Dec. 31, 2012
9.125% Senior Notes, due April 2018 [Member]
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Mar. 22, 2010
9.125% Senior Notes, due April 2018 [Member]
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Dec. 31, 2012
Term Note Due December Twenty Seventeen [Member]
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| Debt Instrument [Line Items] | |||||||||||||||||
| Aggregate principal Convertible Senior Notes | $ 300,000,000 | $ 125,000,000 | $ 125,000,000 | $ 125,000,000 | $ 225,000,000 | $ 300,000,000 | |||||||||||
| Debt Instrument Maturity Date | April 2018 | April 2018 | April 2018 | April 2018 | July 2012 | July 2012 | August 2020 | April 2018 | April 2018 | December 2017 | |||||||
| Debt Instrument issuance date | March 22, 2010 | March 22, 2010 | April 25, 2012 | April 25, 2012 | |||||||||||||
| Debt instrument fixed interest rate | 9.125% | 9.125% | 9.125% | 9.125% | 2.125% | 2.125% | 7.50% | 7.50% | 9.125% | 9.125% | |||||||
| Net unamortized discount | 3,277,000 | ||||||||||||||||
| Amortization Term Loan | $ 6,000,000 | $ 2,500,000 | |||||||||||||||
| LIBOR Plus | 3.21% | 3.55% | |||||||||||||||