Business Segment Information - Schedule of Net Sales by Geographical Segments (Details) - USD ($) $ in Millions	3 Months Ended												12 Months Ended
	Sep. 30, 2020	[1]	Jun. 30, 2020	[2]	Mar. 31, 2020	[3]	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	[4]	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues	$ 1,784.2		$ 1,580.8		$ 1,796.7		$ 1,695.1	$ 2,195.7	$ 2,392.7	$ 1,990.2	$ 1,803.4		$ 6,856.8	$ 8,382.0	$ 7,705.5
North America
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues													6,023.7	7,216.6	6,489.6
Europe, Africa and Middle East
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues													413.7	664.2	851.8
Rest of the World
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues													419.4	501.2	364.1
Intersegment Eliminations
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues													(25.4)	(18.1)	(24.6)
Intersegment Eliminations | North America
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues													(25.4)	(18.1)	(24.6)
Access Equipment
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues													2,505.7	4,079.7	3,776.8
Access Equipment | Operating Segments
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues													2,515.1	4,079.7	3,776.8
Access Equipment | Operating Segments | North America
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues													1,881.6	3,147.9	2,849.9
Access Equipment | Operating Segments | Europe, Africa and Middle East
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues													275.3	548.6	630.2
Access Equipment | Operating Segments | Rest of the World
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues													358.2	383.2	296.7
Access Equipment | Intersegment Eliminations
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues													9.4
Defense
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues													2,260.3	2,030.3	1,827.3
Defense | Operating Segments
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues													2,262.2	2,032.1	1,828.9
Defense | Operating Segments | North America
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues													2,151.1	1,946.7	1,612.9
Defense | Operating Segments | Europe, Africa and Middle East
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues													107.0	84.0	215.0
Defense | Operating Segments | Rest of the World
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues													4.1	1.4	1.0
Defense | Intersegment Eliminations
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues													1.9	1.8	1.6
Fire & Emergency
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues													1,138.1	1,249.8	1,053.6
Fire & Emergency | Operating Segments
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues													1,147.1	1,266.1	1,069.7
Fire & Emergency | Operating Segments | North America
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues													1,069.4	1,142.3	1,006.8
Fire & Emergency | Operating Segments | Europe, Africa and Middle East
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues													29.8	27.7	4.7
Fire & Emergency | Operating Segments | Rest of the World
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues													47.9	96.1	58.2
Fire & Emergency | Intersegment Eliminations
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues													9.0	16.3	16.1
Commercial
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues													951.3	1,020.1	1,046.8
Commercial | Operating Segments
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues													957.8	1,022.2	1,054.7
Commercial | Operating Segments | North America
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues													947.0	997.8	1,044.6
Commercial | Operating Segments | Europe, Africa and Middle East
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues													1.6	3.9	1.9
Commercial | Operating Segments | Rest of the World
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues													9.2	20.5	8.2
Commercial | Intersegment Eliminations
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues													$ 6.5	$ 2.1	$ 7.9

[1] ^{The fourth quarter of fiscal 2020 was impacted by restructuring-related charges of $13.0 million ($9.5 million, net of tax) in the Access Equipment, Fire & Emergency and Commercial segments and Corporate, a gain of $4.2 million ($3.2 million, net of tax) for an arbitration settlement in the Defense segment, business interruption insurance proceeds of $18.5 million ($14.2 million, net of tax) in the Commercial segment and a gain on the sale of a business of $3.1 million ($2.8 million net of tax) in the Commercial segment.}

[2] ^{The third quarter of fiscal 2020 was impacted by restructuring charges of $10.2 million ($8.4 million, net of tax) in the Access Equipment, Fire & Emergency and Commercial segments.}

[3] ^{The second quarter of fiscal 2020 was impacted by debt extinguishment costs of $8.5 million ($6.5 million, net of tax) and a tax charge of $11.4 million related to the establishment of a valuation allowance on net operating losses for an entity in Europe.}

[4] The first quarter of fiscal 2019 was impacted by tax expense related to tax reform in the U.S. of $7.0 million.