FAIR VALUE, Carrying Amounts and Estimated Fair Value of Financial Instruments Not Carried at Fair Value (Details) - USD ($) $ in Millions	Mar. 31, 2020	Sep. 30, 2019
Carrying amount
Financial assets:
Bank loans, net	$ 21,693	$ 20,783
Financial liabilities:
Bank deposits	1,150	605
Senior notes payable	2,044	1,550
Recurring | Total estimated fair value
Financial assets:
Bank loans, net	21,879	20,785
Financial liabilities:
Bank deposits	1,191	617
Senior notes payable	2,208	1,760
Recurring | Level 2 | Total estimated fair value
Financial assets:
Bank loans, net	56	75
Financial liabilities:
Bank deposits	0	0
Senior notes payable	2,208	1,760
Recurring | Level 3 | Total estimated fair value
Financial assets:
Bank loans, net	21,823	20,710
Financial liabilities:
Bank deposits	1,191	617
Senior notes payable	$ 0	$ 0