Valuation and Qualifying Accounts (Detail) - USD ($) $ in Millions		12 Months Ended
		Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Allowance for Doubtful Accounts
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period		$ 12	$ 11	$ 2
Additions Charged to Cost and Expenses		6	7	2
Deductions			(6)
Other	[1]	1		7
Balance at End of period		19	12	11
Reserves for Sales Returns
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period		44	54	53
Additions Charged to Cost and Expenses		131	161	194
Deductions		(142)	(171)	(193)
Balance at End of period		33	44	54
Allowance for Deferred Tax Asset
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period		344	394	296
Additions Charged to Cost and Expenses		27	34	101
Deductions		(61)	(84)	(3)
Balance at End of period		$ 310	$ 344	$ 394

[1] Other changes due to acquisitions and dispositions.