Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Income Statement [Abstract]
Net sales	$ 988.3	$ 854.4	$ 827.5
Cost of goods sold	650.3	542.6	549.8
Gross profit	338.0	311.8	277.7
Selling, general and administrative expenses	151.8	127.1	135.1
Amortization of intangible assets	22.2	22.2	22.8
Operating profit	164.0	162.5	119.8
Interest expense, net	54.7	0.0	0.0
Earnings before income taxes	109.3	162.5	119.8
Income tax expense	9.2	39.4	23.7
Net earnings including redeemable noncontrolling interest	100.1	123.1	96.1
Less: Net earnings attributable to redeemable noncontrolling interest	76.6	123.1	96.1
Net earnings available to Class A common stockholders	$ 23.5	$ 0.0	$ 0.0
Earnings per Class A common share, basic (in usd per share)	$ 0.60	$ 0	$ 0
Earnings per Class A common share, diluted (in usd per share)	$ 0.60	$ 0	$ 0
Weighted-Average Class A common shares outstanding, basic (in shares)	39.4	0.0	0.0
Weighted-Average Class A common shares outstanding, diluted (in shares)	39.5	0.0	0.0