Revenue (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disaggregation of Revenue
Net Sales	$ 342.6	$ 204.2	$ 907.1	$ 705.7
Shakes and other beverages
Disaggregation of Revenue
Net Sales	278.6	167.7	740.2	578.9
Powders
Disaggregation of Revenue
Net Sales	49.7	25.8	126.5	85.4
Nutrition bars
Disaggregation of Revenue
Net Sales	11.9	9.4	34.6	36.3
Other
Disaggregation of Revenue
Net Sales	$ 2.4	$ 1.3	$ 5.8	$ 5.1