Subsequent Events	3 Months Ended
Dec. 31, 2020
Subsequent Events [Abstract]
Subsequent Events	SUBSEQUENT EVENTS Acquisitions On January 25, 2021, the Company completed its previously announced acquisition of the Peter Pan peanut butter brand from Conagra Brands, Inc. for $102.0, subject to working capital and other adjustments, resulting in a payment at closing of $103.4. The acquisition was completed using cash on hand. Peter Pan is a nationally recognized brand with a diversified customer base across key channels and will be reported in the Post Consumer Brands segment (see Note 19). All Peter Pan peanut butter products are currently co-manufactured by 8th Avenue, in which the Company has a 60.5% common equity interest (see Note 3). On February 1, 2020, the Company completed its previously announced acquisition of Almark Foods (“Almark”) for $52.0, subject to working capital and other adjustments, resulting in a payment at closing of $51.3. The acquisition was completed using cash on hand. Almark is a provider of hard-cooked and deviled egg products, offering conventional, organic and cage-free products and distributes its products across retail outlets, including in the perimeter-of-the-store and the deli counter, as well as to foodservice distributors. Almark will be reported in two reportable segments. The results of Almark’s foodservice operations will be reported in the Foodservice segment, and the results of Almark’s retail operations will be reported in the Refrigerated Retail segment (see Note 19). These transactions will be accounted for as business combinations under the acquisition method of accounting. The Company will record the assets acquired and liabilities assumed at their fair values as of the acquisition dates. Due to the limited time since the closing of the acquisitions, the valuation efforts and related acquisition accounting are incomplete for both acquisitions at the time of filing of the condensed consolidated financial statements. As a result, the Company is unable to provide amounts recognized as of the acquisition date for major classes of assets and liabilities acquired, including goodwill and other intangible assets. In addition, because the acquisition accounting is incomplete for both acquisitions, the Company is unable to provide the supplemental pro forma revenue and earnings for the combined entity, as the pro forma adjustments are expected to primarily consist of estimates for the amortization of identifiable intangible assets acquired and related income tax effects which will result from the purchase price allocations and determination of the fair values for the assets acquired and liabilities assumed.

On January 25, 2021, the Company completed its previously announced acquisition of the Peter Pan peanut butter brand from Conagra Brands, Inc. for $102.0, subject to working capital and other adjustments, resulting in a payment at closing of $103.4. The acquisition was completed using cash on hand. Peter Pan is a nationally recognized brand with a diversified customer base across key channels and will be reported in the Post Consumer Brands segment (see Note 19). All Peter Pan peanut butter products are currently co-manufactured by 8th Avenue, in which the Company has a 60.5% common equity interest (see Note 3).

On February 1, 2020, the Company completed its previously announced acquisition of Almark Foods (“Almark”) for $52.0, subject to working capital and other adjustments, resulting in a payment at closing of $51.3. The acquisition was completed using cash on hand. Almark is a provider of hard-cooked and deviled egg products, offering conventional, organic and cage-free products and distributes its products across retail outlets, including in the perimeter-of-the-store and the deli counter, as well as to foodservice distributors. Almark will be reported in two reportable segments. The results of Almark’s foodservice operations will be reported in the Foodservice segment, and the results of Almark’s retail operations will be reported in the Refrigerated Retail segment (see Note 19).

These transactions will be accounted for as business combinations under the acquisition method of accounting. The Company will record the assets acquired and liabilities assumed at their fair values as of the acquisition dates. Due to the limited time since the closing of the acquisitions, the valuation efforts and related acquisition accounting are incomplete for both acquisitions at the time of filing of the condensed consolidated financial statements. As a result, the Company is unable to provide amounts recognized as of the acquisition date for major classes of assets and liabilities acquired, including goodwill and other intangible assets. In addition, because the acquisition accounting is incomplete for both acquisitions, the Company is unable to provide the supplemental pro forma revenue and earnings for the combined entity, as the pro forma adjustments are expected to primarily consist of estimates for the amortization of identifiable intangible assets acquired and related income tax effects which will result from the purchase price allocations and determination of the fair values for the assets acquired and liabilities assumed.