Impairments - Fair Value Measurements Table (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012		Sep. 30, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-lived assets held for use	$ 38		$ 395
Cost-method investment	34		38
Fair Value, Inputs, Level 3 [Member] | Income Approach Valuation Technique [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-lived assets held for use	38	[1]	395	[1]
Cost-method investment	$ 34	[1]	$ 38	[1]

[1] The income approach was used to measure fair value.