Debt - Long-term Debt (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015		Sep. 30, 2014
Debt Instrument [Line Items]
Total debt	$ 2,995		$ 3,030
Less: current portion	13		13
Long-term debt	2,982		3,017
Senior Term Loan Facility due 2020
Debt Instrument [Line Items]
Total debt	1,288	[1]	1,294	[1]
Less: current portion	13		13
5.625% Senior Secured Notes
Debt Instrument [Line Items]
Total debt	275		275
6.00% Senior Secured Notes
Debt Instrument [Line Items]
Total debt	450		450
6.25% Senior Secured Notes
Debt Instrument [Line Items]
Total debt	172	[2]	201	[2]
6.75% Senior Notes due 2022
Debt Instrument [Line Items]
Total debt	660		660
13.75% Holdings Notes due 2019
Debt Instrument [Line Items]
Total debt	$ 150		$ 150

[1] Principal amount of $1.294 billion and $1.300 billion less unamortized discount of $6 million and $6 million at March 31, 2015 and September 30, 2014, respectively. Of this amount, $13 million, representing the scheduled amortization of the Senior Term Loan Facility, was included in the current portion of long-term debt at March 31, 2015 and September 30, 2014.

[2] Face amount of €158 million. Above amounts represent the dollar equivalent of such notes at March 31, 2015 and September 30, 2014.