Retirement Plans Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Pension Plan | United States
Components of Net Periodic Benefit Cost:
Service cost	$ 0	$ 8	$ 15
Interest cost	67	108	105
Expected return on plan assets	(180)	(199)	(229)
Net actuarial (gain) loss	244	361	7
Amortization of prior service cost (credit)	0	0	0
Curtailment gain	0	0	0
Settlement loss	6	13	0
Net periodic benefit cost (credit)	$ 137	$ 291	$ (102)
Expense Assumptions:
Discount rate	2.95%	4.10%	3.80%
Expected return on plan assets	6.90%	7.10%	7.50%
Rate of compensation increase		3.50%	3.20%
Pension Plan | Foreign Plan
Components of Net Periodic Benefit Cost:
Service cost	$ 25	$ 22	$ 23
Interest cost	36	54	57
Expected return on plan assets	(111)	(105)	(114)
Net actuarial (gain) loss	43	236	(22)
Amortization of prior service cost (credit)	1	0	0
Curtailment gain	(8)	0	(2)
Settlement loss	0	4	0
Net periodic benefit cost (credit)	$ (14)	$ 211	$ (58)
Expense Assumptions:
Discount rate	1.50%	2.45%	2.40%
Expected return on plan assets	5.20%	5.20%	5.35%
Rate of compensation increase	2.80%	2.95%	2.90%
Postretirement Benefits
Components of Net Periodic Benefit Cost:
Service cost	$ 1	$ 1	$ 2
Interest cost	4	6	7
Expected return on plan assets	(9)	(9)	(10)
Net actuarial (gain) loss	2	17	5
Amortization of prior service cost (credit)	(3)	0	0
Curtailment gain	0	0	0
Settlement loss	0	0	0
Net periodic benefit cost (credit)	$ (5)	$ 15	$ 4
Expense Assumptions:
Discount rate	2.65%	3.80%	3.70%
Expected return on plan assets	5.70%	5.65%	5.65%
Discontinued Operations | Pension Plan | United States
Components of Net Periodic Benefit Cost:
Net periodic benefit cost (credit)	$ 0	$ (2)	$ (5)
Discontinued Operations | Pension Plan | Foreign Plan
Components of Net Periodic Benefit Cost:
Net periodic benefit cost (credit)	0	0	(7)
Discontinued Operations | Postretirement Benefits
Components of Net Periodic Benefit Cost:
Net periodic benefit cost (credit)	0	0	(2)
Continuing Operations [Member] | Pension Plan | United States
Components of Net Periodic Benefit Cost:
Net periodic benefit cost (credit)	137	289	(107)
Continuing Operations [Member] | Pension Plan | Foreign Plan
Components of Net Periodic Benefit Cost:
Service cost	25	22
Interest cost	36	54
Net periodic benefit cost (credit)	(14)	211	(65)
Continuing Operations [Member] | Postretirement Benefits
Components of Net Periodic Benefit Cost:
Net periodic benefit cost (credit)	$ (5)	$ 15	$ 2