Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2022	Mar. 31, 2021
Disaggregation of Revenue
Net Sales	$ 315.2	$ 282.1	$ 621.7	$ 564.5
Shakes and other beverages
Disaggregation of Revenue
Net Sales	246.0	227.4	491.0	461.6
Powders
Disaggregation of Revenue
Net Sales	59.1	41.4	109.9	76.8
Nutrition bars
Disaggregation of Revenue
Net Sales	7.8	11.1	16.9	22.7
Other
Disaggregation of Revenue
Net Sales	$ 2.3	$ 2.2	$ 3.9	$ 3.4