Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Cash Flows from Operating Activities:
Net earnings including redeemable noncontrolling interest	$ 116.0	$ 114.4	$ 100.1
Adjustments to reconcile net earnings including redeemable noncontrolling interest to net cash provided by operating activities:
Depreciation and amortization	21.3	53.7	25.3
Loss on extinguishment and refinancing of debt, net	17.6	1.6	0.0
Non-cash stock-based compensation expense	9.8	4.6	2.5
Deferred income taxes	(4.0)	(1.5)	(3.3)
Other, net	1.4	3.0	5.9
Other changes in operating assets and liabilities:
Increase in receivables	(70.7)	(21.0)	(14.2)
(Increase) decrease in inventories	(83.9)	32.4	(11.5)
Decrease (increase) in prepaid expenses and other current assets	1.1	(5.7)	(0.2)
Decrease in other assets	2.3	2.5	2.6
Increase (decrease) in accounts payable and other current liabilities	10.3	42.1	(12.1)
(Decrease) increase in non-current liabilities	(0.2)	0.0	2.1
Net Cash Provided by Operating Activities	21.0	226.1	97.2
Cash Flows from Investing Activities:
Additions to property	(1.8)	(1.6)	(2.1)
Net Cash Used in Investing Activities	(1.8)	(1.6)	(2.1)
Cash Flows from Financing Activities:
Proceeds from issuance of long-term debt	164.0	20.0	881.0
Payment of merger consideration	(115.5)	0.0	0.0
Proceeds from issuance of common stock, net of issuance costs	0.0	0.0	524.4
Repayments of long-term debt	(674.9)	(113.8)	(1,416.3)
Purchases of treasury stock	(42.8)	0.0	0.0
Payments of debt issuance, extinguishment and refinancing costs and deferred financing fees	(11.9)	(1.6)	(9.6)
Distributions from (to) Post Holdings, Inc., net	547.2	(24.6)	(32.1)
Other, net	(1.1)	(0.9)	0.0
Net Cash Used in Financing Activities	(135.0)	(120.9)	(52.6)
Effect of Exchange Rate Changes on Cash and Cash Equivalents	(1.0)	0.3	0.7
Net (Decrease) Increase in Cash and Cash Equivalents	(116.8)	103.9	43.2
Cash and Cash Equivalents, Beginning of Year	152.6	48.7	5.5
Cash and Cash Equivalents, End of Year	35.8	152.6	48.7
Noncash Investing and Financing Items [Abstract]
Debt issued to Post Holdings, Inc. in connection with Spin-off	$ 840.0	$ 0.0	$ 0.0