Consolidated Statement of Changes in Shareholders' Equity - USD ($) $ in Millions	Total	Common shares	Treasury shares	Additional paid-in capital	Retained earnings	Accumulated other comprehensive loss
Common shares, issued (in shares) at Sep. 30, 2019		65,200,000
Treasury shares (in shares) at Sep. 30, 2019			(11,000,000.0)
Shareholders' equity at Sep. 30, 2019	$ 1,303.5	$ 0.7	$ (803.8)	$ 1,627.7	$ 714.8	$ (235.9)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	67.6	0.0	0.0	0.0	67.6	0.0
Foreign currency translation adjustments	29.9	0.0	0.0	0.0	0.0	29.9
Pension and postretirement activity, net of tax	17.7	0.0	0.0	0.0	0.0	17.7
Deferred gain (loss) on hedging activity, net of tax	(3.3)	$ 0.0	$ 0.0	0.0	0.0	(3.3)
Activity under share plans (in shares)		0	100,000
Activity under share plans (in usd)	17.5	$ 0.0	$ 13.4	4.1	0.0	0.0
Common shares, issued (in shares) at Sep. 30, 2020		65,200,000
Treasury shares (in shares) at Sep. 30, 2020			(10,900,000)
Shareholders' equity at Sep. 30, 2020	1,432.9	$ 0.7	$ (790.4)	1,631.8	782.4	(191.6)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	117.0	0.0	0.0	0.0	117.0	0.0
Dividends declared to common shareholders	(33.7)				(33.7)
Foreign currency translation adjustments	5.6	0.0	0.0	0.0	0.0	5.6
Pension and postretirement activity, net of tax	44.8	0.0	0.0	0.0	0.0	44.8
Deferred gain (loss) on hedging activity, net of tax	4.3	$ 0.0	$ 0.0	0.0	0.0	4.3
Treasury Stock, Shares, Acquired			(300,000)
Repurchase of shares (in usd)	(9.2)		$ 9.2
Activity under share plans (in shares)		0	300,000
Activity under share plans (in usd)	$ 22.6	$ 0.0	$ 23.3	(0.7)	0.0	0.0
Common shares, issued (in shares) at Sep. 30, 2021	65,251,989	65,200,000
Treasury shares (in shares) at Sep. 30, 2021	(10,882,275)		(10,900,000)
Shareholders' equity at Sep. 30, 2021	$ 1,584.3	$ 0.7	$ (776.3)	1,631.1	865.7	(136.9)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	98.6	0.0	0.0	0.0	98.6	0.0
Dividends declared to common shareholders	(32.6)				(32.6)
Foreign currency translation adjustments	(89.4)	0.0	0.0	0.0	0.0	(89.4)
Pension and postretirement activity, net of tax	4.7	0.0	0.0	0.0	0.0	4.7
Deferred gain (loss) on hedging activity, net of tax	$ 5.5	$ 0.0	$ 0.0	0.0	0.0	5.5
Treasury Stock, Shares, Acquired	(3,300,000)		(3,300,000)
Repurchase of shares (in usd)	$ (125.3)		$ 125.3
Activity under share plans (in shares)		0	500,000
Activity under share plans (in usd)	$ 13.9	$ 0.0	$ 40.7	(26.8)	0.0	0.0
Common shares, issued (in shares) at Sep. 30, 2022	65,251,989	65,200,000
Treasury shares (in shares) at Sep. 30, 2022	(13,678,988)		(13,700,000)
Shareholders' equity at Sep. 30, 2022	$ 1,459.7	$ 0.7	$ (860.9)	$ 1,604.3	$ 931.7	$ (216.1)