Debt - Components of Debt (Parenthetical) (Detail) (USD $)	9 Months Ended				9 Months Ended		9 Months Ended		9 Months Ended	6 Months Ended	9 Months Ended		6 Months Ended			9 Months Ended	6 Months Ended	9 Months Ended	6 Months Ended	9 Months Ended	6 Months Ended	9 Months Ended
	Sep. 30, 2013 7.125% Senior Secured Notes, due April 2017 Secured Debt	Sep. 30, 2013 10.5% Senior Notes, due October 2017 Senior Notes	Sep. 30, 2013 3.375% Convertible Senior Notes, due June 2038 Convertible Debt	Sep. 30, 2012 3.375% Convertible Senior Notes, due June 2038 Convertible Debt	Sep. 30, 2013 10.25% Senior Notes, due April 2019 Senior Notes	Sep. 30, 2013 7.375% Senior Notes, due April 2018 Senior Notes	Sep. 30, 2013 8.75% Senior Notes, due July 2021 Senior Notes	Jul. 08, 2013 8.75% Senior Notes, due July 2021 Senior Notes	Sep. 30, 2013 7.5% Senior Notes, due October 2021 Senior Notes	Jul. 07, 2013 Revolving Credit Facility Senior Secured Credit Facility	Sep. 30, 2013 Revolving Credit Facility Senior Secured Credit Facility	Sep. 30, 2013 Revolving Credit Facility Amended Senior Secured Credit Facility	Jul. 07, 2013 Federal Funds Rate Revolving Credit Facility Senior Secured Credit Facility	Jul. 07, 2013 Eurodollar Rate Revolving Credit Facility Senior Secured Credit Facility	Jul. 07, 2013 Additional Margin over Alternate Base Rate Alternative Base Rate Revolving Credit Facility Minimum Senior Secured Credit Facility	Sep. 30, 2013 Additional Margin over Alternate Base Rate Alternative Base Rate Revolving Credit Facility Minimum Amended Senior Secured Credit Facility	Jul. 07, 2013 Additional Margin over Alternate Base Rate Alternative Base Rate Revolving Credit Facility Maximum Senior Secured Credit Facility	Sep. 30, 2013 Additional Margin over Alternate Base Rate Alternative Base Rate Revolving Credit Facility Maximum Amended Senior Secured Credit Facility	Jul. 07, 2013 Additional Margin over Eurodollar Rate Eurodollar Rate Revolving Credit Facility Minimum Senior Secured Credit Facility	Sep. 30, 2013 Additional Margin over Eurodollar Rate Eurodollar Rate Revolving Credit Facility Minimum Amended Senior Secured Credit Facility	Jul. 07, 2013 Additional Margin over Eurodollar Rate Eurodollar Rate Revolving Credit Facility Maximum Senior Secured Credit Facility	Sep. 30, 2013 Additional Margin over Eurodollar Rate Eurodollar Rate Revolving Credit Facility Maximum Amended Senior Secured Credit Facility
Debt Instrument [Line Items]
Debt instrument percentage rate	7.125%	10.50%	3.375%	3.375%	10.25%	7.375%	8.75%	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		$ 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%	1.50%	4.50%	3.00%	4.00%	2.50%	5.50%	4.00%