Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2020	Nov. 01, 2020
Cover [Abstract]
Document type	10-Q
Document quarterly report	true
Document period end date	Sep. 30, 2020
Document transition report	false
Entity file number	001-32327
Entity registrant name	MOSAIC CO
State of incorporation	DE
Employer identification number	20-1026454
Address line one	101 East Kennedy Blvd
Address line two	Suite 2500
City	Tampa
State	FL
Zip code	33602
Area code	800
Phone number	918-8270
Title of each class	Common Stock, par value $0.01 per share
Trading symbol	MOS
Name of each exchange on which registered	NYSE
Entity current reporting status	Yes
Entity interactive data current	Yes
Entity filer category	Large Accelerated Filer
Smaller reporting company	false
Emerging growth company	false
Entity shell company	false
Entity common stock shares outstanding		379,090,013
Entity central index key	0001285785
Amendment flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Current fiscal year end date	--12-31