Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Cash Flows from Operating Activities:
Net earnings including redeemable noncontrolling interest	$ 165.5	$ 116.0	$ 114.4
Adjustments to reconcile net earnings including redeemable noncontrolling interest to net cash provided by operating activities:
Depreciation and amortization	28.3	21.3	53.7
Loss on extinguishment and refinancing of debt, net	0.0	17.6	1.6
Non-cash stock-based compensation expense	14.2	9.8	4.6
Deferred income taxes	(6.0)	(4.0)	(1.5)
Other, net	1.2	1.4	3.0
Other changes in operating assets and liabilities:
Decrease (increase) in receivables	5.5	(70.7)	(21.0)
Decrease (increase) in inventories	6.4	(83.9)	32.4
(Increase) decrease in prepaid expenses and other current assets	(0.8)	1.1	(5.7)
(Increase) decrease in other assets	(1.8)	2.3	2.5
Increase in accounts payable and other current liabilities	3.1	10.3	42.1
Decrease in non-current liabilities	0.0	(0.2)	0.0
Net Cash Provided by Operating Activities	215.6	21.0	226.1
Cash Flows from Investing Activities:
Additions to property	(1.8)	(1.8)	(1.6)
Net Cash Used in Investing Activities	(1.8)	(1.8)	(1.6)
Cash Flows from Financing Activities:
Proceeds from issuance of long-term debt	115.0	164.0	20.0
Repayments of long-term debt	(189.0)	(674.9)	(113.8)
Payment of merger consideration	0.0	(115.5)	0.0
Purchases of treasury stock	(125.5)	(42.8)	0.0
Payments of debt issuance, extinguishment and refinancing costs and deferred financing fees	0.0	(11.9)	(1.6)
Distributions from (to) Post Holdings, Inc., net	0.0	547.2	(24.6)
Other, net	(2.2)	(1.1)	(0.9)
Net Cash Used in Financing Activities	(201.7)	(135.0)	(120.9)
Effect of Exchange Rate Changes on Cash and Cash Equivalents	0.5	(1.0)	0.3
Net Increase (Decrease) in Cash and Cash Equivalents	12.6	(116.8)	103.9
Cash and Cash Equivalents, Beginning of Year	35.8	152.6	48.7
Cash and Cash Equivalents, End of Year	48.4	35.8	152.6
Noncash Investing and Financing Items [Abstract]
Debt issued to Post Holdings, Inc. in connection with Spin-off	$ 0.0	$ 840.0	$ 0.0