Interim Reporting (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Net sales	$ 534.1	$ 650.0	$ 598.4	$ 469.1	$ 536.9	$ 623.8	$ 547.7	$ 463.3	$ 2,251.6	$ 2,171.7	$ 2,087.3
Gross profit	228.6	280.3	242.3	189.6	219.0	240.9	230.4	190.2	940.8	880.5	951.2
Net earnings	$ 29.9	$ 53.0	$ 19.4	$ 12.4	$ 33.7	$ 30.8	$ 23.5	$ 11.5	$ 114.7	$ 99.5	$ 117.8
Basic net earnings per share	$ 0.59	$ 1.04	$ 0.38	$ 0.24	$ 0.65	$ 0.59	$ 0.43	$ 0.21	$ 2.24	$ 1.87	$ 2.17
Dilutive net earnings per share	$ 0.58	$ 1.02	$ 0.37	$ 0.24	$ 0.64	$ 0.58	$ 0.43	$ 0.20	$ 2.21	$ 1.85	$ 2.13
Previously reported
Gross profit		$ 279.7	$ 241.7	$ 189.0	$ 218.8	$ 240.6	$ 230.1	$ 189.9		$ 879.4	$ 950.1
Net earnings		$ 52.5	$ 19.0	$ 11.9	$ 33.7	$ 30.5	$ 23.2	$ 11.2		$ 98.6	$ 117.0
Basic net earnings per share		$ 1.03	$ 0.37	$ 0.23	$ 0.65	$ 0.58	$ 0.43	$ 0.21		$ 1.86	$ 2.15
Dilutive net earnings per share		$ 1.01	$ 0.37	$ 0.23	$ 0.64	$ 0.57	$ 0.43	$ 0.20		$ 1.84	$ 2.12
Restatement adjustment
Net sales		$ 0.0	$ 0.0	$ 0.0	$ 0.0	$ 0.0	$ 0.0	$ 0.0
Gross profit		0.6	0.6	0.6	0.2	0.3	0.3	0.3		$ 1.1	$ 1.1
Net earnings		$ 0.5	$ 0.4	$ 0.5	$ 0.0	$ 0.3	$ 0.3	$ 0.3		$ 0.9	$ 0.8	$ 5.7
Basic net earnings per share		$ 0.01	$ 0.01	$ 0.01	$ 0	$ 0.01	$ 0	$ 0		$ 0.01	$ 0.02
Dilutive net earnings per share		$ 0.01	$ 0	$ 0.01	$ 0	$ 0.01	$ 0	$ 0		$ 0.01	$ 0.01