Goodwill and Purchased Intangible Assets - Goodwill Allocated to Reportable Segments (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021	Sep. 30, 2021	Sep. 30, 2020
Goodwill [Line Items]
Gross	$ 2,145.8	$ 2,150.7	$ 2,153.7
Accumulated Impairment	(1,103.8)	(1,101.7)	(1,101.7)
Net	1,042.0	1,049.0	1,052.0	$ 1,009.5
Access Equipment
Goodwill [Line Items]
Gross	1,797.9	1,809.7	1,812.7
Accumulated Impairment	(932.1)	(932.1)	(932.1)
Net	865.8	877.6	880.6	882.6
Defense
Goodwill [Line Items]
Gross	44.4	44.4	44.4
Net	44.4	44.4	44.4
Fire & Emergency
Goodwill [Line Items]
Gross	115.2	108.1	108.1
Accumulated Impairment	(2.0)	(2.0)	(2.0)
Net	113.2	106.1	106.1	106.1
Commercial
Goodwill [Line Items]
Gross	188.3	188.5	188.5
Accumulated Impairment	(169.7)	(167.6)	(167.6)
Net	$ 18.6	$ 20.9	$ 20.9	$ 20.8