Benefit Obligations - Benefit Obligations Narrative (Details) - USD ($) $ in Millions		12 Months Ended
	Jan. 31, 2014	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013	Jul. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Savings Plan Benefit Cost			$ 6	$ 7	$ 10
Pension Benefits - U.S.
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Return on Plan Assets			179	168	162
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)			1	1	1
Defined Benefit Plan, Net Periodic Benefit Cost			60	65	104
Defined Benefit Plan, Amortization of Net Actuarial Gain (Loss)			97	82	120
Actuarial loss (gain)			205	249
Prescription Drug Benefit, Reduction in Accumulated Postretirement Benefit Obligation for Subsidy			0	0
Contributions by employer			95	160	108
Defined Benefit Plan, Estimated Future Employer Contributions in Current Fiscal Year			87
Defined Benefit Plan, Expected Future Benefit Payments, Next 12 months			218
Defined Benefit Plan, Benefit Obligation, Period Increase (Decrease)			$ 8
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate in Next Fiscal Year			4.23%
Curtailments, settlements and other			$ 0	$ 0
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets Next Fiscal Year			8.00%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Basis Point Reduction Next Fiscal Year			0.02%
Defined Benefit Plan, Effect of Change in Assumption Used Calculating Net Periodic Benefit Cost, Discount Rate Decrease			$ 6
Plan Asset Allocations			100.00%	100.00%
Discount rate			4.23%	4.21%
Defined Benefit Plan, benefit obligation			$ 3,444	$ 3,333	3,174
Defined Benefit Plan, fair value of plan assets			2,218	2,321	2,176
Pension Benefits - U.S. | U.S. equity
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, fair value of plan assets			488	215
Pension Benefits - U.S. | Non-U.S. equity
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, fair value of plan assets			0	74
Pension Benefits - U.S. | Change in Assumptions for Plans
Defined Benefit Plan Disclosure [Line Items]
Actuarial loss (gain)			189
Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer			28	45	52
Defined Benefit Plan, Expected Future Benefit Payments, Next 12 months			40
Postretirement Benefits - U.S.
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Return on Plan Assets			10	11	10
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)			(13)	(13)	(14)
Defined Benefit Plan, Net Periodic Benefit Cost			3	4	(5)
Defined Benefit Plan, Amortization of Net Actuarial Gain (Loss)			5	4	7
Actuarial loss (gain)			(14)	14
Reduction to accumulated benefit obligation						$ 62
Prescription Drug Benefit, Reduction in Accumulated Postretirement Benefit Obligation for Subsidy			62	3
Contributions by employer			28	45
Defined Benefit Plan, Expected Future Benefit Payments, Next 12 months			35
Defined Benefit Plan, Benefit Obligation, Period Increase (Decrease)			$ 8
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate in Next Fiscal Year			4.35%
Curtailments, settlements and other			$ 0	$ 0
Defined Benefit Plan, Benefit Obligation, Period Increase (Decrease) in Next Fiscal Year			$ 1
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets Next Fiscal Year			5.90%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Basis Point Reduction Next Fiscal Year			0.18%
Defined Benefit Plan, Effect of Change in Assumption Used Calculating Net Periodic Benefit Cost, Discount Rate Decrease			$ 1
Plan Asset Allocations			100.00%	100.00%
Discount rate			4.35%	4.17%
Defined Benefit Plan, benefit obligation			$ 388	$ 486	500
Defined Benefit Plan, fair value of plan assets			$ 159	$ 173	164
Postretirement Benefits - U.S. | Fixed Income Securities
Defined Benefit Plan Disclosure [Line Items]
Plan Asset Allocations				70.00%
Postretirement Benefits - U.S. | U.S. equity
Defined Benefit Plan Disclosure [Line Items]
Plan Asset Allocations				21.00%
Postretirement Benefits - U.S. | Non-U.S. equity
Defined Benefit Plan Disclosure [Line Items]
Plan Asset Allocations				9.00%
Postretirement Benefits - U.S. | US Government Agencies Debt Securities
Defined Benefit Plan Disclosure [Line Items]
Plan Asset Allocations			60.00%
Postretirement Benefits - U.S. | U.S. equity securities
Defined Benefit Plan Disclosure [Line Items]
Plan Asset Allocations			22.00%
Postretirement Benefits - U.S. | Non-U.S. equity securities
Defined Benefit Plan Disclosure [Line Items]
Plan Asset Allocations			18.00%
Postretirement Benefits - U.S. | Change in Assumptions for Plans
Defined Benefit Plan Disclosure [Line Items]
Actuarial loss (gain)			$ (1)
Pension Benefits - Non-U.S.
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Return on Plan Assets			2	$ 2	2
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)			0	0	0
Defined Benefit Plan, Net Periodic Benefit Cost			27	30	31
Defined Benefit Plan, Amortization of Net Actuarial Gain (Loss)			7	4	5
Actuarial loss (gain)			6	57
Prescription Drug Benefit, Reduction in Accumulated Postretirement Benefit Obligation for Subsidy			1	0
Contributions by employer			25	27	25
Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year			26
Defined Benefit Plan, Expected Future Benefit Payments, Next 12 months			26
Defined Benefit Plan, Benefit Obligation, Period Increase (Decrease)			$ 13
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate in Next Fiscal Year			2.53%
Curtailments, settlements and other			$ (3)	$ 0
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Basis Point Reduction Next Fiscal Year			0.10%
Plan Asset Allocations			100.00%	100.00%
Discount rate			2.53%	2.63%
Defined Benefit Plan, benefit obligation			$ 554	$ 616	596
Defined Benefit Plan, fair value of plan assets			$ 59	60	51
Pension Benefits - Non-U.S. | Bonds
Defined Benefit Plan Disclosure [Line Items]
Plan Asset Allocations			100.00%
Not Pre-Funded | Pension Benefits - U.S.
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer			$ 6	7	6
Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year			7
Pre-Funded | Pension Benefits - U.S.
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer			89	$ 153	102
Process of Liquidation, No Estimate | Pension Benefits - U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair Value Hedge Assets, Process of Liquidation			$ 8
Netherlands | Pension Benefits - Non-U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan Asset Allocations			77.00%
Other Restructuring | Pension Benefits - U.S.
Defined Benefit Plan Disclosure [Line Items]
Curtailments, settlements and other					(2)
Other Restructuring | Postretirement Benefits - U.S.
Defined Benefit Plan Disclosure [Line Items]
Curtailments, settlements and other					$ (11)
Communications Workers of America [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Contract Extension Period	2 years
Scenario, Forecast [Member] | Minimum [Member] | Pension Benefits - U.S. | Change in Assumptions for Plans
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost		$ 30
Scenario, Forecast [Member] | Maximum [Member] | Pension Benefits - U.S. | Change in Assumptions for Plans
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost		$ 35