Segment Data - Revenues by Geographic Areas (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Revenues	$ 3,080	$ 2,922
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Revenues	1,657	1,630
International
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Revenues	$ 1,423	$ 1,292