Goodwill and Purchased Intangible Assets - Goodwill Allocated to Reportable Segments (Details) - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Goodwill [Line Items]
Gross	$ 2,119.5	$ 2,105.7
Accumulated Impairment	(1,110.0)	(1,110.0)
Net	1,009.5	995.7	$ 1,007.9
Access Equipment
Goodwill [Line Items]
Gross	1,814.7	1,800.9
Accumulated Impairment	(932.1)	(932.1)
Net	882.6	868.8	880.9
Fire & Emergency
Goodwill [Line Items]
Gross	108.1	108.1
Accumulated Impairment	(2.0)	(2.0)
Net	106.1	106.1	106.1
Commercial
Goodwill [Line Items]
Gross	196.7	196.7
Accumulated Impairment	(175.9)	(175.9)
Net	$ 20.8	$ 20.8	$ 20.9