Summary of Transaction Affecting Debt Balances (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Extinguishment of Debt [Line Items]
Repayment of debt	$ (23,000)	$ (113,214)	$ (74,889)
Exchange of debt for common shares			(28,071)
Gain (loss) on extinguishment
2008 Senior Notes balance prior to emergence from bankruptcy
Extinguishment of Debt [Line Items]
Senior notes			210,000
Rights Offering
Extinguishment of Debt [Line Items]
Repayment of debt			(64,889)
Exchange of debt for common shares			(3,071)
Under the Backstop Agreement
Extinguishment of Debt [Line Items]
Exchange of debt for common shares			(20,000)
Under the Supplemental Equity Exchange
Extinguishment of Debt [Line Items]
Exchange of debt for common shares			(5,000)
Repayment in cash
Extinguishment of Debt [Line Items]
Repayment of debt			(10,000)
Exchange of 2008 Senior Notes for 2014 Notes
Extinguishment of Debt [Line Items]
Exchange of senior notes			$ (107,040)