Quarterly report pursuant to Section 13 or 15(d)

Fair Value of Financial Instruments - Fair Values and Related Carrying Values of Debt Instruments (Detail)

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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
Dec. 31, 2012
Carrying Amount [Member]
   
Long-term Debt    
Long term debt Fair value $ 650,000 $ 425,000
Carrying Amount [Member] | 7.50% Senior Notes, due August 2020 [Member]
   
Long-term Debt    
Long term debt Fair value 225,000 0
Carrying Amount [Member] | 9.125% Senior Notes, due April 2018 [Member]
   
Long-term Debt    
Long term debt Fair value 425,000 425,000
Fair Value [Member]
   
Long-term Debt    
Long term debt Fair value 679,750 453,688
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]
   
Long-term Debt    
Long term debt Fair value $ 454,750 $ 453,688