v3.25.0.1
Segments (Details) - USD ($)
$ in Millions
 3 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Sep. 30, 2024
Segment Reporting Information      
Net Sales $ 1,974.7 $ 1,965.9  
Interest expense, net 84.1 78.1  
Loss (gain) on extinguishment of debt, net 5.8 (3.1)  
(Income) expense on swaps, net (15.4) 21.1  
Earnings before income taxes and equity method (earnings) loss 145.4 116.7  
Depreciation and amortization 120.3 112.4  
Assets 12,819.6   $ 12,854.2
Operating Segments      
Segment Reporting Information      
Net Sales 1,974.7 1,965.9  
Segment Profit (Loss) 257.2 265.0  
Depreciation and amortization 119.3 109.5  
Operating Segments | Post Consumer Brands      
Segment Reporting Information      
Net Sales 963.9 988.6  
Segment Profit (Loss) 131.0 132.7  
Depreciation and amortization 58.2 49.5  
Assets 5,122.4   5,106.5
Operating Segments | Weetabix      
Segment Reporting Information      
Net Sales 127.6 129.1  
Segment Profit (Loss) 15.9 21.0  
Depreciation and amortization 12.0 9.6  
Assets 1,815.4   1,948.4
Operating Segments | Foodservice      
Segment Reporting Information      
Net Sales 616.6 567.1  
Segment Profit (Loss) 86.1 75.7  
Depreciation and amortization 31.7 32.5  
Operating Segments | Refrigerated Retail      
Segment Reporting Information      
Net Sales 266.6 280.9  
Segment Profit (Loss) 24.2 35.6  
Depreciation and amortization 17.4 17.9  
Operating Segments | Foodservice and Refrigerated Retail      
Segment Reporting Information      
Assets 4,867.1   4,875.2
Corporate      
Segment Reporting Information      
Net Sales 0.0 0.2  
Corporate      
Segment Reporting Information      
General corporate expenses and other 37.3 52.2  
Depreciation and amortization 1.0 2.9  
Assets 1,014.7   $ 924.1
Cereal | Operating Segments      
Segment Reporting Information      
Net Sales 645.0 655.2  
Eggs and egg products | Operating Segments      
Segment Reporting Information      
Net Sales 559.0 522.8  
Side dishes (including potato products) | Operating Segments      
Segment Reporting Information      
Net Sales 212.6 217.0  
Pet Food | Operating Segments      
Segment Reporting Information      
Net Sales 408.9 426.6  
Cheese and dairy | Operating Segments      
Segment Reporting Information      
Net Sales 42.7 48.6  
Sausage | Operating Segments      
Segment Reporting Information      
Net Sales 50.7 49.1  
Peanut butter | Operating Segments      
Segment Reporting Information      
Net Sales 28.1 27.4  
Protein-based products and supplements | Operating Segments      
Segment Reporting Information      
Net Sales 13.6 5.1  
Other | Operating Segments      
Segment Reporting Information      
Net Sales $ 14.1 $ 14.1