Business Segment Information - Schedule of Reportable Segments (Details) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Sales	$ 6,997.4	$ 6,329.8	$ 6,694.8
Sales and operating results of reportable segments
Purchase accounting depreciation and amortization	(55.1)	(41.4)	(16.6)
Corporate and other	(120.6)	(98.9)	(108.8)
Non-operating pension and postretirement benefit (cost) credit	(63.8)	(37.4)	8.4
Gain (loss) on investments	397.4	153.9	(402.2)
Valuation adjustments related to the registration of PTC Shares	0.0	0.0	33.7
Legal settlement	70.0	0.0	0.0
Interest (expense) income - net	(93.0)	(98.0)	(87.1)
Income before income taxes	1,526.2	1,136.1	901.0
Operating Segments
Segment Reporting Information [Line Items]
Sales	6,997.4	6,329.8	6,694.8
Segment operating earnings	1,391.3	1,257.9	1,473.6
Intelligent Devices
Segment Reporting Information [Line Items]
Sales	3,311.9	2,956.0
Intelligent Devices \| Operating Segments
Segment Reporting Information [Line Items]
Sales	3,311.9	2,956.0	3,279.7
Segment operating earnings	702.1	587.8	697.0
Software & Control
Segment Reporting Information [Line Items]
Sales	1,947.0	1,681.3
Software & Control \| Operating Segments
Segment Reporting Information [Line Items]
Sales	1,947.0	1,681.3	1,790.0
Segment operating earnings	531.0	473.8	531.2
Lifecycle Services \| Operating Segments
Segment Reporting Information [Line Items]
Sales	1,738.5	1,692.5	1,625.1
Segment operating earnings	$ 158.2	$ 196.3	$ 245.4

Equity Securities, FV-NI, Unrealized Gain (Loss), Loss On Investment

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Non-operating pension costs consist of defined benefit plan interest cost, expected return on plan assets, amortization of actuarial gains and losses and the impacts of any plan curtailments or settlements. These costs are excluded from segment operating earnings.

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