Cover Page - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2021	Feb. 01, 2022
Cover [Abstract]
Document type	10-K
Document Annual Report	true
Document period end date	Dec. 31, 2021
Document Transition Report	false
Entity File Number	001-32327
Entity registrant name	Mosaic Co
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	20-1026454
Entity Address, Address Line One	101 East Kennedy Blvd
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
Title of 12(b) Security	Common Stock, par value $0.01 per share
Trading Symbol	MOS
Security Exchange Name	NYSE
Entity well known seasoned issuer	Yes
Entity voluntary filers	No
Entity current reporting status	Yes
Entity Interactive Data Current	Yes
Entity filer category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity public float	$ 12.1
Entity common stock shares outstanding		368,309,275
Entity central index key	0001285785
Amendment flag	false
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--12-31
ICFR Auditor Attestation Flag	true
Auditor Firm ID	185
Auditor Location	Dallas, TX
Auditor Name	KPMG LLP