| Document and Entity Information | Oct. 10, 2019 |
| Cover page. | |
| Document Type | 8-K |
| Document Period End Date | Oct. 10, 2019 |
| 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 | 3033 Campus Drive |
| Entity Address, Address Line Two | Suite E490 |
| Entity Address, City or Town | Plymouth, |
| Entity Address, State or Province | MN |
| Entity Address, Postal Zip Code | 55441 |
| 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 |
