Intangible Assets, net (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Mar. 31, 2021	Mar. 31, 2021	Sep. 30, 2020
Finite-Lived Intangible Assets
Finite-lived intangible assets, gross	$ 425.9	$ 425.9	$ 425.9
Finite-lived intangible assets, accumulated amortization	(180.7)	(180.7)	(151.6)
Finite-lived intangible assets, net	245.2	245.2	274.3
Accelerated amortization	17.7	18.1
Customer relationships
Finite-Lived Intangible Assets
Finite-lived intangible assets, gross	209.4	209.4	209.4
Finite-lived intangible assets, accumulated amortization	(93.7)	(93.7)	(76.9)
Finite-lived intangible assets, net	115.7	115.7	132.5
Customer relationships | Supreme Protein
Finite-Lived Intangible Assets
Finite-lived intangible assets, net	7.5	7.5
Trademarks and brands
Finite-Lived Intangible Assets
Finite-lived intangible assets, gross	213.4	213.4	213.4
Finite-lived intangible assets, accumulated amortization	(83.9)	(83.9)	(71.6)
Finite-lived intangible assets, net	129.5	129.5	141.8
Trademarks and brands | Supreme Protein
Finite-Lived Intangible Assets
Finite-lived intangible assets, net	4.7	4.7
Other intangible assets
Finite-Lived Intangible Assets
Finite-lived intangible assets, gross	3.1	3.1	3.1
Finite-lived intangible assets, accumulated amortization	(3.1)	(3.1)	(3.1)
Finite-lived intangible assets, net	$ 0.0	$ 0.0	$ 0.0