Guarantor and Non-Guarantor Subsidiaries Financial Information - Additional Information (Detail)	3 Months Ended	12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014
13.75% Holdings Notes due 2019
Parent Company Only Financial Information [Line Items]
Interest rate	13.75%	13.75%
Maturity date	2019	2019
5.625% Senior Secured Notes
Parent Company Only Financial Information [Line Items]
Interest rate	5.625%	5.625%
Maturity date	2022	2022
6.00% Senior Secured Notes due 2021
Parent Company Only Financial Information [Line Items]
Interest rate	6.00%	6.00%
Maturity date	2021	2021
6.25% Senior Secured Notes
Parent Company Only Financial Information [Line Items]
Interest rate	6.25%	6.25%
Maturity date	2021	2021
6.75% Senior Notes due 2022
Parent Company Only Financial Information [Line Items]
Interest rate	6.75%	6.75%
Maturity date	2022	2022