Goodwill and Purchased Intangible Assets - Schedule of Changes in Goodwill (Details) $ in Millions	6 Months Ended
Mar. 31, 2021 USD ($)
Changes in goodwill
Net goodwill at the beginning of the period	$ 1,009.5
Foreign currency translation	1.6
Acquisition	75.4
Net goodwill at the end of the period	1,086.5
Access Equipment
Changes in goodwill
Net goodwill at the beginning of the period	882.6
Foreign currency translation	1.5
Net goodwill at the end of the period	884.1
Defense
Changes in goodwill
Acquisition	75.4
Net goodwill at the end of the period	75.4
Fire & Emergency
Changes in goodwill
Net goodwill at the beginning of the period	106.1
Net goodwill at the end of the period	106.1
Commercial
Changes in goodwill
Net goodwill at the beginning of the period	20.8
Foreign currency translation	0.1
Net goodwill at the end of the period	$ 20.9

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(10)(1))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
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-Section 45
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