Supplementary Data (Unaudited) - Additional Information (Detail) - USD ($) $ / shares in Units, $ 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
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 4,784	$ 3,855	$ 4,253	$ 4,225	$ 4,584	$ 4,350	$ 4,195	$ 4,160	$ 17,117	$ 17,290	$ 15,983
Gross Profit	2,206	1,659	1,734	1,978	2,266	2,074	1,974	1,974	7,577	8,288
Net Income	$ 128	$ 286	$ 183	$ 278	$ 163	$ 451	$ 20	$ 599	$ 874	$ 1,233	$ 311
Earnings (loss) per Share:
Earnings Per Share, Basic	$ 0.36	$ 0.98	$ 0.53	$ 0.88	$ 0.46	$ 1.53	$ (0.07)	$ 2.09	$ 2.75	$ 4.01	$ 0.62
Diluted Earnings per Share (USD per share)	$ 0.36	$ 0.97	$ 0.53	$ 0.87	$ 0.45	$ 1.51	$ (0.07)	$ 2.05	$ 2.71	$ 3.94	$ 0.60