Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended												12 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2017
Results of Operations
Net sales	$ 641.4	$ 609.9	$ 556.5	$ 572.4	$ 618.0	$ 572.2	$ 487.8	$ 479.8					$ 2,380.2	$ 2,157.7	$ 1,797.6
Gross profit	122.9	123.2	107.0	91.7	114.9	96.1	85.7	85.6					444.8	382.3	300.8
Operating income (loss)	67.9	73.2	55.4	45.0	60.0	45.7	41.4	42.2					241.4	189.3	121.5
Net income (loss)	$ 48.9	$ 51.1	$ 35.5	$ 31.5	$ 42.8	$ 30.2	$ 92.1	$ 23.4					$ 167.0	$ 188.5	$ 47.0
Earnings per common share
Basic (in dollars per share)	$ 1.01	$ 1.06	$ 0.73	$ 0.66	$ 0.90	$ 0.63	$ 1.93	$ 0.49					$ 3.46	$ 3.96	$ 0.99
Diluted (in dollars per share)	$ 1.00	$ 1.05	$ 0.73	$ 0.65	$ 0.88	$ 0.63	$ 1.92	$ 0.49					$ 3.43	$ 3.92	$ 0.99
Weighted average common shares outstanding
Basic (in shares)					47.7	47.7	47.7	47.6	47.4	47.2	47.2	47.1	47.7	47.2	47.0
Diluted (in shares)					48.1	48.1	48.0	48.2	48.0	47.7	47.6	47.3	48.1	47.6	47.1