Amounts in Accumulated Other Comprehensive Income Expected to be Recognized as Components of Net Periodic Benefit Cost over Next Fiscal Year (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Amortization of:
Net actuarial (gain) loss	$ (10)	$ (420)	$ 393
Postretirement Benefits
Amortization of:
Service cost	2	2	2
Interest cost	7	6	6
Expected return on plan assets	(10)	(10)	(10)
Net actuarial (gain) loss	5	(5)	(2)
Amortization of prior service cost (credit)	0	0	(1)
Curtailment gain	0	0	0
Settlement (gain) loss	0	0	0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	$ 4	$ (7)	$ (5)
Discount rate	3.70%	3.30%	3.75%
Expected return on plan assets	5.65%	5.60%	5.45%
Discontinued Operations | Postretirement Benefits
Amortization of:
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	$ 0	$ 0	$ (1)
Continuing Operations [Member] | Postretirement Benefits
Amortization of:
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	4	(7)	(6)
UNITED STATES | Pension Benefits
Amortization of:
Service cost	15	18	16
Interest cost	105	113	104
Expected return on plan assets	(229)	(229)	(191)
Net actuarial (gain) loss	7	(220)	268
Amortization of prior service cost (credit)	0	0	0
Curtailment gain	0	0	0
Settlement (gain) loss	0	(16)	11
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	$ (102)	$ (334)	$ 208
Discount rate	3.80%	3.70%	4.40%
Expected return on plan assets	7.50%	7.50%	7.50%
Rate of compensation increase	3.20%	3.20%	3.25%
UNITED STATES | Discontinued Operations | Pension Benefits
Amortization of:
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	$ 0	$ 0	$ (1)
UNITED STATES | Continuing Operations [Member] | Pension Benefits
Amortization of:
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	(102)	(334)	207
Non-US [Member] | Pension Benefits
Amortization of:
Service cost	23	32	30
Interest cost	57	48	44
Expected return on plan assets	(114)	(92)	(61)
Net actuarial (gain) loss	(22)	(195)	237
Amortization of prior service cost (credit)	0	0	1
Curtailment gain	(2)	(19)	0
Settlement (gain) loss	0	(1)	6
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	$ (58)	$ (227)	$ 257
Discount rate	2.40%	1.90%	3.10%
Expected return on plan assets	5.35%	4.60%	4.50%
Rate of compensation increase	2.90%	2.65%	3.30%
Non-US [Member] | Discontinued Operations | Pension Benefits
Amortization of:
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	$ 0	$ 0	$ (111)
Non-US [Member] | Continuing Operations [Member] | Pension Benefits
Amortization of:
Service cost	23	32
Interest cost	57	48
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	$ (58)	$ (227)	$ 146