FAIR VALUE, Carrying Amounts and Estimated Fair Value of Financial Instruments Not Carried at Fair Value (Details) - USD ($) $ in Millions	Mar. 31, 2021	Sep. 30, 2020
Carrying amount
Financial assets:
Bank loans, net	$ 22,700	$ 21,125
Financial liabilities:
Bank deposits - certificates of deposit	889	1,017
Senior notes payable	2,045	2,045
Recurring | Total estimated fair value
Financial assets:
Bank loans, net	22,570	21,191
Financial liabilities:
Bank deposits - certificates of deposit	917	1,056
Senior notes payable	2,400	2,504
Recurring | Level 2 | Total estimated fair value
Financial assets:
Bank loans, net	52	72
Financial liabilities:
Bank deposits - certificates of deposit	0	0
Senior notes payable	2,400	2,504
Recurring | Level 3 | Total estimated fair value
Financial assets:
Bank loans, net	22,518	21,119
Financial liabilities:
Bank deposits - certificates of deposit	917	1,056
Senior notes payable	$ 0	$ 0