Revenue (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue
Net sales	$ 204.2	$ 237.6	$ 705.7	$ 639.9
Shakes and other beverages
Disaggregation of Revenue
Net sales	167.7	191.3	578.9	493.6
Powders
Disaggregation of Revenue
Net sales	25.8	27.9	85.4	90.0
Nutrition Bars
Disaggregation of Revenue
Net sales	9.4	16.1	36.3	48.9
Other Products
Disaggregation of Revenue
Net sales	$ 1.3	$ 2.3	$ 5.1	$ 7.4