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v3.25.3

Marketable Securities Held in Trusts (Details) $ in Millions | Sep. 30, 2025 USD ($) | Dec. 31, 2024 USD ($) | Aug. 31, 2016 USD ($)
--- | --- | --- | ---
Investments, Debt and Equity Securities [Abstract] |  |  |
Amount deposited by Mosaic into the RCRA Trusts |  |  | $ 630.0
Number Of Decades Remaining For Trust | 3 |  |
Available-for-sale Securities, Fair Value to Amortized Cost Basis |  |  |
Amortized cost | $ 723.6 | $ 712.3 |
Gross unrealized gains | 15.2 | 1.5 |
Gross unrealized losses | (4.6) | (18.6) |
Debt Securities, Available-for-sale | 734.2 | 695.2 |
Cash and Cash Equivalents | Level 1 |  |  |
Available-for-sale Securities, Fair Value to Amortized Cost Basis |  |  |
Amortized cost | 2.5 | 3.1 |
Gross unrealized gains | 0.0 | 0.0 |
Gross unrealized losses | 0.0 | 0.0 |
Debt Securities, Available-for-sale | 2.5 | 3.1 |
Corporate debt securities | Level 2 |  |  |
Available-for-sale Securities, Fair Value to Amortized Cost Basis |  |  |
Amortized cost | 218.1 | 203.3 |
Gross unrealized gains | 3.9 | 0.8 |
Gross unrealized losses | (3.1) | (6.8) |
Debt Securities, Available-for-sale | 218.9 | 197.3 |
Municipal bonds | Level 2 |  |  |
Available-for-sale Securities, Fair Value to Amortized Cost Basis |  |  |
Amortized cost | 212.0 | 210.8 |
Gross unrealized gains | 3.4 | 0.7 |
Gross unrealized losses | (1.5) | (4.0) |
Debt Securities, Available-for-sale | 213.9 | 207.5 |
U.S. government bonds | Level 2 |  |  |
Available-for-sale Securities, Fair Value to Amortized Cost Basis |  |  |
Amortized cost | 291.0 | 295.1 |
Gross unrealized gains | 7.9 | 0.0 |
Gross unrealized losses | 0.0 | (7.8) |
Debt Securities, Available-for-sale | 298.9 | $ 287.3 |
Debt securities |  |  |
Available-for-sale Securities, Fair Value to Amortized Cost Basis |  |  |
Debt Securities, Available-for-sale | $ 731.7 |  |

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