v3.24.1.u1
Segments (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Mar. 31, 2024
Mar. 31, 2023
Mar. 31, 2024
Mar. 31, 2023
Sep. 30, 2023
Segment Reporting Information          
Net Sales $ 1,999.0 $ 1,619.9 $ 3,964.9 $ 3,186.2  
Interest expense, net 80.0 63.8 158.1 129.7  
Loss (gain) on extinguishment of debt, net 0.3 (6.1) (2.8) (14.8)  
(Income) expense on swaps, net (13.3) 9.0 7.8 (3.3)  
Earnings before income taxes and equity method loss 125.9 74.5 242.6 192.9  
Depreciation and amortization 119.6 94.2 232.0 186.8  
Assets 12,191.1   12,191.1   $ 11,646.7
Operating Segments          
Segment Reporting Information          
Net Sales 1,999.0 1,619.9 3,964.9 3,186.2  
Segment Profit (Loss) 244.7 191.2 509.7 392.1  
Depreciation and amortization 112.5 93.0 222.0 184.5  
Operating Segments | Post Consumer Brands          
Segment Reporting Information          
Net Sales 1,065.5 599.1 2,054.1 1,153.8  
Segment Profit (Loss) 139.7 75.5 272.4 154.8  
Depreciation and amortization 51.7 32.8 101.2 65.1  
Assets 4,983.5   4,983.5   4,782.2
Operating Segments | Weetabix          
Segment Reporting Information          
Net Sales 138.0 124.9 267.1 243.0  
Segment Profit (Loss) 18.1 19.4 39.1 40.9  
Depreciation and amortization 9.8 8.9 19.4 17.4  
Assets 1,818.6   1,818.6   1,737.8
Operating Segments | Foodservice          
Segment Reporting Information          
Net Sales 554.8 633.2 1,121.9 1,233.7  
Segment Profit (Loss) 64.5 78.1 140.2 157.2  
Depreciation and amortization 33.3 32.0 65.8 63.7  
Operating Segments | Refrigerated Retail          
Segment Reporting Information          
Net Sales 240.4 262.7 521.3 555.7  
Segment Profit (Loss) 22.4 18.2 58.0 39.2  
Depreciation and amortization 17.7 19.3 35.6 38.3  
Operating Segments | Foodservice and Refrigerated Retail          
Segment Reporting Information          
Assets 4,924.5   4,924.5   4,921.6
Eliminations and Corporate          
Segment Reporting Information          
Net Sales 0.3 0.0 0.5 0.0  
Corporate          
Segment Reporting Information          
General corporate expenses and other 51.8 50.0 104.0 87.6  
Depreciation and amortization 7.1 1.2 10.0 2.3  
Assets 464.5   464.5   $ 205.1
Cereal | Operating Segments          
Segment Reporting Information          
Net Sales 706.6 690.3 1,361.8 1,327.7  
Eggs and egg products | Operating Segments          
Segment Reporting Information          
Net Sales 517.0 609.4 1,039.8 1,178.1  
Side dishes (including potato products) | Operating Segments          
Segment Reporting Information          
Net Sales 184.8 184.7 401.8 390.0  
Pet Food | Operating Segments          
Segment Reporting Information          
Net Sales 460.7 0.0 887.3 0.0  
Cheese and dairy | Operating Segments          
Segment Reporting Information          
Net Sales 41.4 47.9 90.0 101.0  
Sausage | Operating Segments          
Segment Reporting Information          
Net Sales 40.1 40.2 89.2 92.3  
Nut butters | Operating Segments          
Segment Reporting Information          
Net Sales 27.3 26.0 54.7 54.9  
Protein-based products and supplements | Operating Segments          
Segment Reporting Information          
Net Sales 8.4 7.7 13.5 14.2  
Other | Operating Segments          
Segment Reporting Information          
Net Sales 12.7 14.5 26.8 28.8  
Eliminations | Eliminations and Corporate          
Segment Reporting Information          
Net Sales $ 0.0 $ (0.8) $ 0.0 $ (0.8)