Condensed Consolidated Statements of Cash Flows - USD ($)	6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash Flows from Operating Activities:
Net earnings including redeemable noncontrolling interest	$ 50,400,000	$ 56,100,000
Adjustments to reconcile net earnings including redeemable noncontrolling interest to net cash flow used in operating activities:
Depreciation and amortization	12,800,000	12,700,000
Non-cash stock-based compensation expense	1,100,000	0
Deferred income taxes	(3,400,000)	2,600,000
Other, net	2,500,000	5,500,000
Other changes in operating assets and liabilities:
Increase in receivables	(42,700,000)	(25,100,000)
Increase in inventories	(12,900,000)	(34,500,000)
Increase in prepaid expenses and other current assets	(2,700,000)	(1,800,000)
Decrease in other assets	1,200,000	100,000
Decrease in accounts payable and other current liabilities	(11,400,000)	(14,700,000)
Decrease in non-current liabilities	0	700,000
Net Cash (Used in) Provided by Operating Activities	(5,100,000)	1,600,000
Cash Flows from Investing Activities:
Additions to property	(1,200,000)	(1,400,000)
Net Cash Used in Investing Activities	(1,200,000)	(1,400,000)
Cash Flows from Financing Activities:
Proceeds from issuance of long-term debt	871,000,000.0	0
Proceeds from issuance of common stock, net of issuance costs	524,400,000	0
Repayments of long-term debt	(1,298,700,000)	0
Payments of debt issuance costs and deferred financing fees	(9,600,000)	0
Distributions (to) from Post Holdings, Inc., net	(9,500,000)	(8,000,000.0)
Net Cash Provided by (Used in) Financing Activities	77,600,000	(8,000,000.0)
Effect of exchange rate changes on cash and cash equivalents	(100,000)	(200,000)
Cash and Cash Equivalents,Period Increase (Decrease), Including Exchange Rate Effect, Total	71,200,000	(8,000,000.0)
Cash and Cash Equivalents, Beginning of Period	5,500,000	10,900,000
Cash and Cash Equivalents, End of Period	$ 76,700,000	$ 2,900,000