Accounting Changes - Additional Information (Detail) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Income tax provision	$ 131	$ 37
Excess Tax Benefit from Share-based Compensation, Operating Activities	(27)	$ 0
New Accounting Pronouncement, Early Adoption, Effect
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Income tax provision	$ 27
Weighted Average Number of Shares Outstanding, Basic, Increase (Decrease)	1
Excess Tax Benefit from Share-based Compensation, Operating Activities	$ 27