Revenue (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue
Net Sales	$ 282.4	$ 244.0
Shakes and other beverages
Disaggregation of Revenue
Net Sales	234.2	199.8
Powders
Disaggregation of Revenue
Net Sales	35.4	29.0
Nutrition bars
Disaggregation of Revenue
Net Sales	11.6	13.9
Other
Disaggregation of Revenue
Net Sales	$ 1.2	$ 1.3