Fair Value Measurements - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
8.625 % Senior Notes Due 2017
Debt Instrument [Line Items]
Long term debt, Fair Value	$ 401,250	$ 386,250
6.75 % Senior Notes Due 2014
Debt Instrument [Line Items]
Long term debt, Fair Value		199,000
Convertible Notes Due 2017
Debt Instrument [Line Items]
Liability component of convertible note	249,601
7.5% Senior Notes due 2022
Debt Instrument [Line Items]
Liability component of convertible note	$ 314,250