Annual report pursuant to Section 13 and 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
Dec. 31, 2012
Dec. 31, 2011
Carrying Amount [Member]
   
Long-term Debt    
Long term debt Fair value $ 425,000 $ 425,000
Carrying Amount [Member] | 9.125% Senior Notes, due April 2018 (Issued March 22, 2010) [Member]
   
Long-term Debt    
Long term debt Fair value 300,000 300,000
Carrying Amount [Member] | 9.125% Senior Notes, due April 2018 (Issued April 25, 2012) [Member]
   
Long-term Debt    
Long term debt Fair value 125,000  
Carrying Amount [Member] | 2.125% Convertible Senior Notes due July 2012 [Member]
   
Long-term Debt    
Long term debt Fair value   125,000
Fair Value [Member]
   
Long-term Debt    
Long term debt Fair value 453,688 438,204
Fair Value [Member] | 9.125% Senior Notes, due April 2018 (Issued March 22, 2010) [Member]
   
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]
   
Long-term Debt    
Long term debt Fair value 133,438  
Fair Value [Member] | 2.125% Convertible Senior Notes due July 2012 [Member]
   
Long-term Debt    
Long term debt Fair value   $ 123,204