Summary of Significant Accounting Policies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011
Accounting Policies [Abstract]
Other-than-temporary impairment of available-for-sale securities	$ 0	$ 4	$ 0
Expected average employee future service period for United States plans (in years)	8 years
Building
Property, Plant and Equipment [Line Items]
Estimated useful life	40 years
Minimum
Property, Plant and Equipment [Line Items]
Acquired long-lived intangible assets useful life	1 year
Minimum | Furniture and Fixtures
Property, Plant and Equipment [Line Items]
Estimated useful life	2 years
Minimum | Building Improvements
Property, Plant and Equipment [Line Items]
Estimated useful life	3 years
Maximum
Property, Plant and Equipment [Line Items]
Acquired long-lived intangible assets useful life	15 years
Maximum | Furniture and Fixtures
Property, Plant and Equipment [Line Items]
Estimated useful life	7 years
Maximum | Building Improvements
Property, Plant and Equipment [Line Items]
Estimated useful life	40 years