v3.26.1
Accumulated Other Comprehensive Income (Loss) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Mar. 31, 2026
Dec. 31, 2025
Mar. 31, 2025
Dec. 31, 2024
Accumulated Other Comprehensive Income (Loss) [Line Items]                
Accumulated other comprehensive loss $ (2,166.7)   $ (2,166.7)     $ (2,131.9)    
Other Comprehensive Income (Loss), Tax (72.9) $ 241.3 (27.7) $ 360.9        
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, after Tax (3.0) 5.3 (6.1) 1.8        
Net (loss) gain on marketable securities held in trust fund (1.0) 7.7 (5.6) 15.6        
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Tax (0.1) 0.0 (0.1) 0.0        
Other comprehensive income (loss) (75.9) 246.6 (33.8) 362.7        
Total Mosaic stockholders' equity 11,463.9   11,463.9     12,084.9    
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest 0.4 (1.2) (1.0) (2.8)        
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]                
Accumulated Other Comprehensive Income (Loss) [Line Items]                
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, before Tax (71.8) 231.0 (20.9) 340.1        
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax (2.1) 8.8 (1.4) 7.8        
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax (73.9) 239.8 (22.3) 347.9        
Total Mosaic stockholders' equity (2,139.0) (2,075.2) (2,139.0) (2,075.2) $ (2,065.5) (2,115.7) $ (2,313.8) $ (2,420.3)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest 0.4 (1.2) (1.0) (2.8)        
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]                
Accumulated Other Comprehensive Income (Loss) [Line Items]                
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, before Tax 0.2 0.3 0.5 0.5        
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, after Tax (1.1) (1.2) (6.3) (1.3)        
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, after Tax (0.9) (0.9) (5.8) (0.8)        
Total Mosaic stockholders' equity (30.6) (22.9) (30.6) (22.9) (29.7) (24.8) (22.0) (22.1)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest 0.0 0.0 0.0 0.0        
AOCI, Derivative Qualifying as Hedge, Excluded Component, Noncontrolling Interest [Member]                
Accumulated Other Comprehensive Income (Loss) [Line Items]                
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax (0.1) 0.0 (0.1) 0.0        
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax 0.0 0.0 0.0 0.0        
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Tax (0.1) 0.0 (0.1) 0.0        
Total Mosaic stockholders' equity 7.8 8.0 7.8 8.0 7.9 7.9 8.0 8.0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest 0.0 0.0 0.0 0.0        
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent [Member]                
Accumulated Other Comprehensive Income (Loss) [Line Items]                
Net (loss) gain on marketable securities held in trust fund, net of tax 0.2 (2.3) 1.6 (4.7)        
Net (loss) gain on marketable securities held in trust fund (1.0) 7.7 (5.6) 15.6        
Other Comprehensive Income (Loss), Securities, Available-for-sale, Tax (1.2) 10.0 (7.2) 20.3        
Total Mosaic stockholders' equity (4.9) 1.0 (4.9) 1.0 (3.9) 0.7 (6.7) (14.6)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest 0.0 0.0 0.0 0.0        
Accumulated Other Comprehensive Loss                
Accumulated Other Comprehensive Income (Loss) [Line Items]                
Total Mosaic stockholders' equity $ (2,166.7) $ (2,089.1) $ (2,166.7) $ (2,089.1) $ (2,091.2) $ (2,131.9) $ (2,334.5) $ (2,449.0)