Derivative Instruments and Hedging Activities Location and Fair Values of Derivative Instruments and Hedging Activities (Details) - USD ($)	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Derivative Instruments [Line Items]
Gross amount recognized, derivative assets	$ 91,000,000	$ 95,000,000
Gross amount, derivative liabilities	2,105,000,000	2,980,000,000
Equity swap
Derivative Instruments [Line Items]
Derivative, Amount of Hedged Item	58,000,000	0
Designated as Hedging Instrument
Derivative Instruments [Line Items]
Gross amount recognized, derivative assets	36,000,000	46,000,000
Gross amount, derivative liabilities	2,080,000,000	2,957,000,000
Designated as Hedging Instrument | Other current assets | Foreign currency exchange derivatives
Derivative Instruments [Line Items]
Gross amount recognized, derivative assets	27,000,000	41,000,000
Designated as Hedging Instrument | Other current assets | Commodity derivatives
Derivative Instruments [Line Items]
Gross amount recognized, derivative assets	9,000,000	4,000,000
Designated as Hedging Instrument | Other noncurrent assets | Interest rate swaps
Derivative Instruments [Line Items]
Gross amount recognized, derivative assets	0	1,000,000
Designated as Hedging Instrument | Other noncurrent assets | Equity swap
Derivative Instruments [Line Items]
Gross amount recognized, derivative assets	0	0
Designated as Hedging Instrument | Other current liabilities | Foreign currency exchange derivatives
Derivative Instruments [Line Items]
Gross amount, derivative liabilities	21,000,000	48,000,000
Designated as Hedging Instrument | Other current liabilities | Commodity derivatives
Derivative Instruments [Line Items]
Gross amount, derivative liabilities	1,000,000	0
Designated as Hedging Instrument | Liabilities held for sale [Domain] | Foreign currency exchange derivatives
Derivative Instruments [Line Items]
Gross amount, derivative liabilities	0	0
Designated as Hedging Instrument | Current portion of long-term debt | Fixed rate debt swapped to floating
Derivative Instruments [Line Items]
Gross amount, derivative liabilities	0	551,000,000
Designated as Hedging Instrument | Long-term debt | Fixed rate debt swapped to floating
Derivative Instruments [Line Items]
Gross amount, derivative liabilities	0	301,000,000
Designated as Hedging Instrument | Long-term debt | Foreign Currency Denominated Debt [Member]
Derivative Instruments [Line Items]
Gross amount, derivative liabilities	2,058,000,000	938,000,000
Designated as Hedging Instrument | Noncurrent liabilities held for sale [Domain] | Foreign currency exchange derivatives
Derivative Instruments [Line Items]
Gross amount, derivative liabilities	0	1,119,000,000
Not Designated as Hedging Instrument
Derivative Instruments [Line Items]
Gross amount recognized, derivative assets	55,000,000	49,000,000
Gross amount, derivative liabilities	25,000,000	23,000,000
Not Designated as Hedging Instrument | Other current assets | Foreign currency exchange derivatives
Derivative Instruments [Line Items]
Gross amount recognized, derivative assets	0	49,000,000
Not Designated as Hedging Instrument | Other current assets | Commodity derivatives
Derivative Instruments [Line Items]
Gross amount recognized, derivative assets	0	0
Not Designated as Hedging Instrument | Other noncurrent assets | Interest rate swaps
Derivative Instruments [Line Items]
Gross amount recognized, derivative assets	0	0
Not Designated as Hedging Instrument | Other noncurrent assets | Equity swap
Derivative Instruments [Line Items]
Gross amount recognized, derivative assets	55,000,000	0
Not Designated as Hedging Instrument | Other current liabilities | Foreign currency exchange derivatives
Derivative Instruments [Line Items]
Gross amount, derivative liabilities	25,000,000	18,000,000
Not Designated as Hedging Instrument | Other current liabilities | Commodity derivatives
Derivative Instruments [Line Items]
Gross amount, derivative liabilities	0	0
Not Designated as Hedging Instrument | Liabilities held for sale [Domain] | Foreign currency exchange derivatives
Derivative Instruments [Line Items]
Gross amount, derivative liabilities	0	5,000,000
Not Designated as Hedging Instrument | Current portion of long-term debt | Fixed rate debt swapped to floating
Derivative Instruments [Line Items]
Gross amount, derivative liabilities	0	0
Not Designated as Hedging Instrument | Long-term debt | Fixed rate debt swapped to floating
Derivative Instruments [Line Items]
Gross amount, derivative liabilities	0	0
Not Designated as Hedging Instrument | Long-term debt | Foreign Currency Denominated Debt [Member]
Derivative Instruments [Line Items]
Gross amount, derivative liabilities	0	0
Not Designated as Hedging Instrument | Noncurrent liabilities held for sale [Domain] | Foreign currency exchange derivatives
Derivative Instruments [Line Items]
Gross amount, derivative liabilities	0	0
Cash Flow Hedging
Derivative Instruments [Line Items]
Amount of Gain (Loss) Reclassified from AOCI into Income	33,000,000	(32,000,000)	$ (9,000,000)
Net financing charges | Cash Flow Hedging | Forward Treasury Locks
Derivative Instruments [Line Items]
Amount of Gain (Loss) Reclassified from AOCI into Income	$ 0	$ 1,000,000	$ 1,000,000