Segment Data - Revenues to Unaffiliated Customers and Long-lived Assets Including Property, Plant and Equipment (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 4,784	$ 3,855	$ 4,253	$ 4,225	$ 4,584	$ 4,350	$ 4,195	$ 4,160	$ 17,117	$ 17,290	$ 15,983
Long-Lived Assets	45,043				45,101				45,043	45,101	46,494
Corporate
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-Lived Assets	411				377				411	377	375
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									9,716	9,730	8,768
Long-Lived Assets	36,468				37,053				36,468	37,053	38,982
Europe
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									3,480	3,359	3,298
Long-Lived Assets	5,835				5,483				5,835	5,483	5,640
Greater Asia
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									2,568	2,726	2,460
Long-Lived Assets	1,521				1,328				1,521	1,328	851
Other
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									1,353	1,476	1,457
Long-Lived Assets	$ 808				$ 861				$ 808	$ 861	$ 645