Accounting Changes - Additional Information (Detail) - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Income tax (benefit) provision	$ (271)	$ 32	$ (123)	$ 107
Excess Tax Benefit from Share-based Compensation, Operating Activities			(60)	$ 0
New Accounting Pronouncement, Early Adoption, Effect
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Income tax (benefit) provision	$ 12		$ 60
Weighted Average Number of Shares Outstanding, Basic, Increase (Decrease)			1
Excess Tax Benefit from Share-based Compensation, Operating Activities			$ 60