Debt - Components of Debt (Parenthetical) (Detail) (USD $)	3 Months Ended		6 Months Ended						6 Months Ended		0 Months Ended	6 Months Ended								3 Months Ended	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 7.125% Senior Secured Notes, due April 2017 Secured Debt	Jun. 30, 2013 10.5% Senior Notes, due October 2017 Senior Notes	Jun. 30, 2013 3.375% Convertible Senior Notes, due June 2038 Convertible Debt	Jun. 30, 2012 3.375% Convertible Senior Notes, due June 2038 Convertible Debt	Jun. 30, 2013 10.25% Senior Notes, due April 2019 Senior Notes	Jun. 30, 2013 7.375% Senior Notes, due April 2018 Senior Notes	Jul. 08, 2013 8.75% Percent Senior Notes Senior Notes	Jun. 30, 2013 8.75% Percent Senior Notes Senior Notes	Jun. 30, 2013 Revolving Credit Facility Senior Secured Credit Facility	Jun. 30, 2013 Revolving Credit Facility Federal Funds Rate Senior Secured Credit Facility	Jun. 30, 2013 Revolving Credit Facility Eurodollar Rate Senior Secured Credit Facility	Jun. 30, 2013 Revolving Credit Facility Additional Margin over Alternate Base Rate Minimum Senior Secured Credit Facility	Jun. 30, 2013 Revolving Credit Facility Additional Margin over Alternate Base Rate Maximum Senior Secured Credit Facility	Jun. 30, 2013 Revolving Credit Facility Additional Margin over Eurodollar Rate Minimum Senior Secured Credit Facility	Jun. 30, 2013 Revolving Credit Facility Additional Margin over Eurodollar Rate Maximum Senior Secured Credit Facility	Jun. 30, 2012 Loss on Extinguishment of Debt 3.375% Convertible Senior Notes, due June 2038 Convertible Debt	Jun. 30, 2012 Loss on Extinguishment of Debt 3.375% Convertible Senior Notes, due June 2038 Convertible Debt
Debt Instrument [Line Items]
Debt instrument percentage rate					7.125%	10.50%	3.375%	3.375%	10.25%	7.375%	8.75%
Minimum other indebtedness in default that would trigger event of cross default under certain conditions (in dollars)					$ 25,000,000	$ 25,000,000	$ 25,000,000		$ 25,000,000			$ 25,000,000	$ 25,000,000
Credit facility alternate base rate description													The Alternate Base Rate ("ABR") (the highest of the administrative agent's corporate base rate of interest, the federal funds rate plus 0.5%, or the one-month Eurodollar rate (as defined in the Credit Agreement) plus 1%)
Maximum secured leverage ratio													350.00%
Debt Instrument, Basis Spread on Variable Rate														0.50%	1.00%	3.00%	4.50%	4.00%	5.50%
Maturity Date Of Debt Instrument											2021-07
Loss On Debt Retirement	$ 0	$ 9,156,000	$ 0	$ 9,156,000																$ 1,300,000	$ 1,300,000