Fair Value Summary of Long-Term Debt with Fixed Interest Rates (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt with fixed interest rates	$ 603,000	$ 604,925
Fair Value | 10.375% Senior Unsecured Notes due 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt with fixed interest rates	316,500	319,500
Fair Value | 7.25% Senior Unsecured Notes due 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt with fixed interest rates	286,500	280,500
Fair Value | 4.50% Convertible Notes due 2012
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt with fixed interest rates	0	4,925
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt with fixed interest rates	594,759	598,307
Carrying Value | 10.375% Senior Unsecured Notes due 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt with fixed interest rates	294,759	293,561
Carrying Value | 7.25% Senior Unsecured Notes due 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt with fixed interest rates	300,000	300,000
Carrying Value | 4.50% Convertible Notes due 2012
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt with fixed interest rates	$ 0	$ 4,746