Retirement Benefits (Plan Assets Target Allocation) (Details) - Defined Benefit Pension Plan	Sep. 30, 2020	Sep. 30, 2019
U.S.
Defined Benefit Plan Disclosure [Line Items]
Actual allocation (percent)	100.00%	100.00%
U.S. | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Actual allocation (percent)	51.00%	38.00%
U.S. | Bonds (government and corporate)
Defined Benefit Plan Disclosure [Line Items]
Actual allocation (percent)	43.00%	56.00%
U.S. | Real estate/other
Defined Benefit Plan Disclosure [Line Items]
Actual allocation (percent)	5.00%	6.00%
U.S. | Cash
Defined Benefit Plan Disclosure [Line Items]
Actual allocation (percent)	1.00%	0.00%
U.S. | Minimum | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Target allocation (percent)	42.00%
U.S. | Minimum | Bonds (government and corporate)
Defined Benefit Plan Disclosure [Line Items]
Target allocation (percent)	35.00%
U.S. | Minimum | Real estate/other
Defined Benefit Plan Disclosure [Line Items]
Target allocation (percent)	0.00%
U.S. | Minimum | Cash
Defined Benefit Plan Disclosure [Line Items]
Target allocation (percent)	0.00%
U.S. | Maximum | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Target allocation (percent)	57.00%
U.S. | Maximum | Bonds (government and corporate)
Defined Benefit Plan Disclosure [Line Items]
Target allocation (percent)	50.00%
U.S. | Maximum | Real estate/other
Defined Benefit Plan Disclosure [Line Items]
Target allocation (percent)	10.00%
U.S. | Maximum | Cash
Defined Benefit Plan Disclosure [Line Items]
Target allocation (percent)	0.00%
International
Defined Benefit Plan Disclosure [Line Items]
Actual allocation (percent)	100.00%	100.00%
International | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Actual allocation (percent)	43.00%	42.00%
International | Bonds (government and corporate)
Defined Benefit Plan Disclosure [Line Items]
Actual allocation (percent)	56.00%	57.00%
International | Real estate/other
Defined Benefit Plan Disclosure [Line Items]
Actual allocation (percent)	0.00%	0.00%
International | Cash
Defined Benefit Plan Disclosure [Line Items]
Actual allocation (percent)	1.00%	1.00%
International | Minimum | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Target allocation (percent)	40.00%
International | Minimum | Bonds (government and corporate)
Defined Benefit Plan Disclosure [Line Items]
Target allocation (percent)	51.00%
International | Minimum | Real estate/other
Defined Benefit Plan Disclosure [Line Items]
Target allocation (percent)	0.00%
International | Minimum | Cash
Defined Benefit Plan Disclosure [Line Items]
Target allocation (percent)	0.00%
International | Maximum | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Target allocation (percent)	49.00%
International | Maximum | Bonds (government and corporate)
Defined Benefit Plan Disclosure [Line Items]
Target allocation (percent)	60.00%
International | Maximum | Real estate/other
Defined Benefit Plan Disclosure [Line Items]
Target allocation (percent)	0.00%
International | Maximum | Cash
Defined Benefit Plan Disclosure [Line Items]
Target allocation (percent)	0.00%