Income Taxes Deferred Taxes Classified in Consolidated Statements of Financial Position (Detail) - USD ($) $ in Millions	Sep. 30, 2016	Sep. 30, 2015
Income Tax Disclosure [Abstract]
Other noncurrent assets	$ 2,905	$ 1,873
Other noncurrent liabilities	(1,597)	(391)
Net deferred tax asset	$ 1,308	$ 1,482