Subsequent Events - Schedule of Proforma Debt (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014		Sep. 30, 2013
Proforma Debt Instrument [Line Items]
Current portion of long-term debt	$ 13		$ 13
Total long-term debt	2,869		2,867
Long-term debt	2,856		2,854
Term Loan Facility due 2020
Proforma Debt Instrument [Line Items]
Current portion of long-term debt	13		13
Total long-term debt	1,300	[1]	1,303	[1]
6.00% Senior Secured Notes
Proforma Debt Instrument [Line Items]
Total long-term debt	450		450
6.25% Senior Secured Notes
Proforma Debt Instrument [Line Items]
Total long-term debt	217	[2]	213	[2]
13.75% Holdings Notes due 2019
Proforma Debt Instrument [Line Items]
Total long-term debt	150		150
Revolving Credit Facility
Proforma Debt Instrument [Line Items]
Current portion of long-term debt		[3]		[3]
Pro Forma
Proforma Debt Instrument [Line Items]
Current portion of long-term debt	13
Total long-term debt	3,052
Long-term debt	3,039
Pro Forma | Term Loan Facility due 2020
Proforma Debt Instrument [Line Items]
Current portion of long-term debt	13
Total long-term debt	1,300	[4]
Pro Forma | 5.625% Senior Secured
Proforma Debt Instrument [Line Items]
Total long-term debt	275
Pro Forma | 6.00% Senior Secured Notes
Proforma Debt Instrument [Line Items]
Total long-term debt	450
Pro Forma | 6.25% Senior Secured Notes
Proforma Debt Instrument [Line Items]
Total long-term debt	217	[5]
Pro Forma | 6.75% Senior Notes due 2022
Proforma Debt Instrument [Line Items]
Total long-term debt	660
Pro Forma | 11.5% Senior Notes due 2018
Proforma Debt Instrument [Line Items]
Total long-term debt
Pro Forma | 13.75% Holdings Notes due 2019
Proforma Debt Instrument [Line Items]
Total long-term debt	150
Pro Forma | Revolving Credit Facility
Proforma Debt Instrument [Line Items]
Current portion of long-term debt		[6]

[1] Principal amount of $1.307 billion less unamortized discount of $7 million at March 31, 2014. Principal amount of $1.310 billion less unamortized discount of $7 million at September 30, 2013. Of this amount, $13 million at both March 31, 2014 and September 30, 2013, representing the scheduled amortization, was included in the current portion of long term debt.

[2] Face amount of €158 million. Amounts above represent the dollar equivalent of such notes at March 31, 2014 and September 30, 2013.

[3] Reflects $150 million of commitments under the Revolving Credit Facility, less letters of credit outstanding of approximately $11 million and $1 million at March 31, 2014 and September 30, 2013, respectively. There were no loans outstanding under the Revolving Credit Facility at March 31, 2014 or September 30, 2013.

[4] Principal amount of $1.307 billion less unamortized discount of $7 million at March 31, 2014. Of this amount, $13 million at March 31, 2014, representing the scheduled amortization, was included in the current portion of long term debt.

[5] Face amount of €158 million. Amounts above represent the dollar equivalent of such notes at March 31, 2014.

[6] Reflects $150 million of commitments under the Revolving Credit Facility, less letters of credit outstanding of approximately $11 million at March 31, 2014. There were no loans outstanding under the Revolving Credit Facility at March 31, 2014.