Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	6 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Cash Flows from Operating Activities:
Net Earnings Including Redeemable Noncontrolling Interest	$ 75.1	$ 43.2
Adjustments to reconcile net earnings including redeemable noncontrolling interest to net cash provided by operating activities:
Depreciation and amortization	10.5	10.6
Loss on extinguishment of debt, net	0.0	17.6
Non-cash stock-based compensation expense	7.0	3.3
Deferred income taxes	(0.9)	1.7
Other, net	0.2	(0.9)
Other changes in operating assets and liabilities:
Increase in receivables, net	(19.8)	(28.9)
Increase in inventories	(64.5)	(27.3)
Decrease in prepaid expenses and other current assets	0.3	0.7
Decrease in other assets	0.9	1.1
Increase (decrease) in accounts payable and other current liabilities	11.5	(3.4)
Decrease in non-current liabilities	0.0	(0.1)
Net Cash Provided by Operating Activities	20.3	17.6
Cash Flows from Investing Activities:
Additions to property	(0.5)	(1.1)
Net Cash Used in Investing Activities	(0.5)	(1.1)
Cash Flows from Financing Activities:
Proceeds from issuance of long-term debt	115.0	109.0
Payment of merger consideration	0.0	(115.5)
Repayments of long-term debt	(75.0)	(609.9)
Purchases of treasury stock	(68.5)	(18.1)
Payments of debt issuance, extinguishment costs and deferred financing fees	0.0	(11.1)
Distributions to Post Holdings, Inc., net	0.0	547.2
Other, net	(2.2)	(1.1)
Net Cash Used in Financing Activities	(30.7)	(99.5)
Effect of Exchange Rate Changes on Cash and Cash Equivalents	0.6	(0.1)
Net Decrease in Cash and Cash Equivalents	(10.3)	(83.1)
Cash and Cash Equivalents, Beginning of Year	35.8	152.6
Cash and Cash Equivalents, End of Period	25.5	69.5
Noncash Investing and Financing Items [Abstract]
Noncash Transaction, Debt Assumed	$ 0.0	$ 840.0