Debt - Schedule of Cash and Non-Cash Interest Expense (Parenthetical) (Detail)	Sep. 30, 2013
1.875% Convertible Senior Notes due 2013 [Member]
Debt Instrument [Line Items]
Interest rates for senior notes	1.875%
4.0% Convertible Senior Notes due 2014 [Member]
Debt Instrument [Line Items]
Interest rates for senior notes	4.00%
8.0% Senior Notes due 2016 [Member]
Debt Instrument [Line Items]
Interest rates for senior notes	8.00%
8.25% Senior Notes [Member]
Debt Instrument [Line Items]
Interest rates for senior notes	8.25%
5.625% Senior Notes [Member]
Debt Instrument [Line Items]
Interest rates for senior notes	5.625%
5.75% Senior Notes [Member]
Debt Instrument [Line Items]
Interest rates for senior notes	5.75%