v3.26.1
Segments (Details)
$ in Millions
 3 Months Ended 9 Months Ended
Jun. 30, 2026
USD ($)
Jun. 30, 2025
USD ($)
Jun. 30, 2026
USD ($)
Jun. 30, 2025
USD ($)
Sep. 30, 2025
USD ($)
Segment Reporting          
Number of Reportable Segments     4    
Net Sales $ 1,948.0 $ 1,984.3 $ 6,165.5 $ 5,911.1  
Cost of goods sold 1,381.7 1,388.1 4,343.1 4,173.8  
Selling, general and administrative expenses 326.1 312.1 1,009.6 958.5  
Interest expense, net 108.2 88.5 317.3 259.6  
Loss on extinguishment of debt, net 0.0 0.0 17.5 5.8  
(Income) expense on swaps, net (3.3) 2.6 (6.9) (7.3)  
Earnings before income taxes and equity method (earnings) loss 86.6 143.3 320.5 371.1  
Additions to property and intangibles 82.1 131.0 289.8 360.5  
Depreciation and amortization 133.5 132.2 424.2 378.1  
Assets 12,852.7   12,852.7   $ 13,528.4
Eliminations          
Segment Reporting          
Net Sales (0.7) 0.0 (4.3) 0.0  
Operating Segments          
Segment Reporting          
Net Sales 1,948.7 1,984.3 6,169.8 5,911.1  
Segment Profit (Loss) 263.7 288.2 852.3 780.9  
Depreciation and amortization 126.8 121.0 388.8 361.7  
Operating Segments | Cereal and granola          
Segment Reporting          
Net Sales 651.5 651.3 1,990.5 1,952.2  
Operating Segments | Eggs and egg products          
Segment Reporting          
Net Sales 569.5 648.1 1,712.6 1,756.8  
Operating Segments | Pet Food          
Segment Reporting          
Net Sales 318.8 364.9 1,025.9 1,206.9  
Operating Segments | Side dishes (including potato products)          
Segment Reporting          
Net Sales 183.5 182.9 599.3 566.2  
Operating Segments | Nut butters          
Segment Reporting          
Net Sales 92.0 23.3 299.1 72.0  
Operating Segments | Sausage          
Segment Reporting          
Net Sales 33.0 36.2 127.2 126.9  
Operating Segments | Cheese and dairy          
Segment Reporting          
Net Sales 10.3 37.0 87.3 116.7  
Operating Segments | Protein-based products          
Segment Reporting          
Net Sales 40.5 28.3 108.6 71.8  
Operating Segments | Other          
Segment Reporting          
Net Sales 49.6 12.3 219.3 41.6  
Operating Segments | Post Consumer Brands          
Segment Reporting          
Net Sales 974.2 914.0 3,122.9 2,865.8  
Cost of goods sold 665.3 614.7 2,167.0 1,918.1  
Selling, general and administrative expenses 156.1 156.6 487.1 489.4  
Segment Reporting, Other Segment Item, Amount 25.5 22.2 75.2 67.2  
Segment Profit (Loss) 127.3 120.5 393.6 391.1  
Additions to property and intangibles 36.0 65.9 146.9 195.6  
Depreciation and amortization 62.4 55.4 192.6 173.0  
Assets 5,626.8   5,626.8   6,290.2
Operating Segments | Foodservice          
Segment Reporting          
Net Sales 652.9 698.5 1,949.4 1,923.0  
Cost of goods sold 497.8 528.0 1,458.4 1,506.5  
Selling, general and administrative expenses 41.2 33.6 123.8 106.4  
Segment Reporting, Other Segment Item, Amount 13.1 13.0 39.1 38.6  
Segment Profit (Loss) 100.8 123.9 328.1 271.5  
Depreciation and amortization 36.0 33.5 107.3 97.3  
Operating Segments | Refrigerated Retail          
Segment Reporting          
Net Sales 184.5 233.9 686.4 725.1  
Cost of goods sold 133.5 160.3 480.4 507.2  
Selling, general and administrative expenses 32.8 38.3 114.5 121.2  
Segment Reporting, Other Segment Item, Amount 8.7 10.8 29.5 31.8  
Segment Profit (Loss) 9.5 24.5 62.0 64.9  
Depreciation and amortization 17.1 18.9 54.8 54.4  
Operating Segments | Weetabix          
Segment Reporting          
Net Sales 137.1 137.9 411.1 397.2  
Cost of goods sold 80.6 88.9 248.3 250.6  
Selling, general and administrative expenses 29.2 29.1 91.1 92.2  
Segment Reporting, Other Segment Item, Amount 1.2 0.6 3.1 1.0  
Segment Profit (Loss) 26.1 19.3 68.6 53.4  
Additions to property and intangibles 8.7 9.9 25.8 25.1  
Depreciation and amortization 11.3 13.2 34.1 37.0  
Assets 1,917.2   1,917.2   1,924.9
Operating Segments | Foodservice and Refrigerated Retail          
Segment Reporting          
Additions to property and intangibles 37.3 55.2 115.3 139.8  
Assets 4,956.0   4,956.0   5,028.1
Corporate and eliminations          
Segment Reporting          
Net Sales (0.7) 0.0 (4.3) 0.0  
Corporate          
Segment Reporting          
General corporate expenses and other 72.2 53.8 203.9 151.7  
Additions to property and intangibles 0.1 0.0 1.8 0.0  
Depreciation and amortization 6.7 $ 11.2 35.4 $ 16.4  
Assets $ 352.7   $ 352.7   $ 285.2