Business Segment Information - Schedule of Income (Loss) from Continuing Operations by Product Lines and Reportable 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
Operating income (loss):
Operating income (loss)		$ 127.4		$ 118.6		$ 133.6		$ 109.1	$ 203.1	$ 257.8	$ 175.6	$ 160.5		$ 488.7	$ 797.0	$ 656.0
Interest expense, net of interest income	[5]													(51.8)	(47.6)	(55.6)
Miscellaneous other (expense) income	[6]													2.2	1.3	(5.8)
Income before income taxes and earnings (losses) of unconsolidated affiliates														439.1	750.7	594.6
Commercial
Operating income (loss):
Miscellaneous other (expense) income														6.2
Operating Segments | Access Equipment
Operating income (loss):
Operating income (loss)	[7]													198.6	502.6	387.5
Operating Segments | Defense
Operating income (loss):
Operating income (loss)	[8]													183.5	203.3	225.4
Operating Segments | Fire & Emergency
Operating income (loss):
Operating income (loss)	[9]													151.1	176.5	137.6
Operating Segments | Commercial
Operating income (loss):
Operating income (loss)	[10]													81.2	66.8	67.5
Corporate, Non-segment
Operating income (loss):
Operating income (loss)	[11]													$ (125.7)	$ (152.2)	$ (162.0)

[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.

[5] Fiscal 2020 results include $8.5 million in debt extinguishment costs and $3.3 million interest income from an arbitration settlement in the Defense segment. Fiscal 2018 results include $9.9 million in debt extinguishment costs.

[6] Fiscal 2020 results include a $6.2 million gain from insurance proceeds in excess of property loss in the Commercial segment.

[7] Fiscal 2020 results include $10.4 million of restructuring costs and $4.7 million operating expenses related to restructuring plans. Fiscal 2018 results include $4.7 million of restructuring costs and $24.8 million of operating expenses related to restructuring plans.

[8] Fiscal 2020 results include reimbursement of $0.9 million of legal costs associated with an arbitration settlement. Fiscal 2018 results include a $19.0 million gain for a litigation settlement (See Note 18 of the Notes to Consolidated Financial Statements for additional details regarding the settlement).

[9] Fiscal 2020 includes $1.4 million of restructuring costs.

[10] Fiscal 2020 results include $1.5 million of restructuring costs, $4.1 million of accelerated depreciation related to restructuring actions, a gain of $12.3 million arising from a business interruption insurance recovery and a gain on the sale of a business of $3.1 million. Fiscal 2018 results include $5.4 million of restructuring costs, a business interruption insurance gain of $6.6 million and a loss on the sale of a small product line of $1.4 million

[11] Fiscal 2020 includes $1.1 million of restructuring costs.