Financial Instruments - Financial Instruments Measured at Fair Value (Parenthetical) (Detail)	Sep. 30, 2013	Dec. 31, 2012
7.875% Senior Notes [Member]
Financial Instruments And Fair Value Measurements [Line Items]
Debt stated interest rate	7.875%	7.875%
6.50% Convertible Senior Notes, Net of Unamortized Discounts [Member]
Financial Instruments And Fair Value Measurements [Line Items]
Debt stated interest rate	6.50%	6.50%
Total Fair Value [Member] | 7.875% Senior Notes [Member]
Financial Instruments And Fair Value Measurements [Line Items]
Debt stated interest rate	7.875%	7.875%
Total Fair Value [Member] | 6.50% Convertible Senior Notes, Net of Unamortized Discounts [Member]
Financial Instruments And Fair Value Measurements [Line Items]
Debt stated interest rate		6.50%