Fair Value Summary of Long-Term Debt with Fixed Interest Rates (Detail) (USD $)	Jun. 30, 2011	Dec. 31, 2010
4.5% Convertible Notes due 2012 | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt with fixed interest rates	$ 5,047	$ 225,975
10.375% Senior Unsecured Notes due 2016 | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt with fixed interest rates	330,000	335,712
7.25% Senior Unsecured Notes due 2019 | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt with fixed interest rates	289,500
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt with fixed interest rates	624,547	561,687
4.5% Convertible Notes due 2012 | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt with fixed interest rates	4,659	214,049
10.375% Senior Unsecured Notes due 2016 | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt with fixed interest rates	293,009	292,487
7.25% Senior Unsecured Notes due 2019 | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt with fixed interest rates	300,000
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt with fixed interest rates	$ 597,668	$ 506,536