| Document and Entity Information | Jan. 28, 2020 |
| Cover page. | |
| Document Type | 8-K |
| Document Period End Date | Jan. 28, 2020 |
| Entity Registrant Name | MOSAIC CO |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-32327 |
| Entity Tax Identification Number | 20-1026454 |
| Entity Address, Address Line One | 101 East Kennedy Boulevard |
| Entity Address, Address Line Two | Suite 2500 |
| Entity Address, City or Town | Tampa, |
| Entity Address, State or Province | FL |
| Entity Address, Postal Zip Code | 33602 |
| City Area Code | 800 |
| Local Phone Number | 918-8270 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of each class | Common Stock, par value $0.01 per share |
| Trading Symbol | MOS |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001285785 |
| Amendment Flag | false |
