Accounting Changes (Details) - USD ($) $ in Millions	Jun. 30, 2023	Mar. 31, 2023	Oct. 01, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2021
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Beneficial conversion feature	$ 4,373			$ 6,074	$ 6,005
Common Stock | Cumulative effect of change in accounting - ASU 2020-06 (Note 3)
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Beneficial conversion feature			$ (6)
Preferred Stock
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Beneficial conversion feature	167	$ 167		162	162	$ 161	$ 213
Preferred Stock | Cumulative effect of change in accounting - ASU 2020-06 (Note 3)
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Beneficial conversion feature			6	5		1	1
Retained Earnings
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Beneficial conversion feature	$ 2,974	$ 3,842		4,841	$ 4,674	4,757	4,081
Retained Earnings | Cumulative effect of change in accounting - ASU 2020-06 (Note 3)
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Beneficial conversion feature			$ 1	$ 1		$ (1)	$ (1)