Basis of Presentation - Additional Information (Detail) - USD ($) $ in Millions	Mar. 31, 2017	Sep. 30, 2016
Basis Of Presentation [Line Items]
Prepaid expenses and other current assets	$ 56	$ 49
Other assets	$ 46	40
Accounting Standards Update 2015-03 [Member] | Restatement Adjustment [Member]
Basis Of Presentation [Line Items]
Prepaid expenses and other current assets		1
Other assets		3
Adjustments for New Accounting Principle Early Adoption [Member]
Basis Of Presentation [Line Items]
Reclassification of current deferred tax assets to noncurrent deferred tax assets		41
Reclassification of current deferred tax liabilities to noncurrent deferred tax liabilities		$ 1