Notes Payable - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended			1 Months Ended	6 Months Ended		6 Months Ended		1 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011	May 10, 2011 Senior Secured Notes 8.625 Percent Due May 2019	Jun. 30, 2012 Senior Secured Notes 8.625 Percent Due May 2019	Dec. 31, 2011 Senior Secured Notes 8.625 Percent Due May 2019	Jun. 30, 2012 Senior Secured Notes 8.625 Percent Due May 2019 Semi Annual Payment, Second Payment	Jun. 30, 2012 Senior Secured Notes 8.625 Percent Due May 2019 Semi Annual Payment, First Payment	May 10, 2011 Secured Debt
Debt Instrument [Line Items]
Principal amount of debt issued						$ 750,000,000
Principal payment on debt											779,600,000
Interest payment on debt											2,500,000
Gain (loss) on extinquishment of debt	0	(88,384,000)	0	(88,384,000)							(88,400,000)
Interest payment date									May 15	November 15
Maturity date							May 15, 2019
Accrued interest	$ 8,086,000		$ 8,086,000		$ 8,122,000		$ 8,100,000	$ 8,100,000