Assets and Liabilities Measured at Fair Value (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Millions	Jun. 30, 2018	Sep. 30, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	$ 41	$ 36
Total	(147)	(92)
Fair value of borrowings	23,665	25,874
Interest rate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset		10
Derivative Liabilities	(370)	(122)
Foreign exchange
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset	479	403
Derivative Liabilities	(311)	(427)
Other Derivative
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset	14	8
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	41	36
Total	41	36
Fair value of borrowings	0	0
Level 1 \| Interest rate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset		0
Derivative Liabilities	0	0
Level 1 \| Foreign exchange
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset	0	0
Derivative Liabilities	0	0
Level 1 \| Other Derivative
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset	0	0
Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	0	0
Total	(188)	(128)
Fair value of borrowings	22,442	23,110
Level 2 \| Interest rate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset		10
Derivative Liabilities	(370)	(122)
Level 2 \| Foreign exchange
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset	479	403
Derivative Liabilities	(311)	(427)
Level 2 \| Other Derivative
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset	14	8
Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	0	0
Total	0	0
Fair value of borrowings	1,223	2,764
Level 3 \| Interest rate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset		0
Derivative Liabilities	0	0
Level 3 \| Foreign exchange
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset	0	0
Derivative Liabilities	0	0
Level 3 \| Other Derivative
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset	$ 0	$ 0

Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

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-Name Accounting Standards Codification
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Fair value of asset after deduction of liability.

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