Goodwill (Details) $ in Millions	3 Months Ended
	Mar. 31, 2020 USD ($)
Goodwill [Line Items]
Goodwill, Gross	$ 1,100.0
Goodwill, net of accumulated amortization	1,156.9
Foreign currency translation	(79.9)
Goodwill, net of accumulated amortization	1,077.0
Potash segment
Goodwill [Line Items]
Goodwill, net of accumulated amortization	1,039.8
Foreign currency translation	(72.6)
Goodwill, net of accumulated amortization	$ 967.2
Reporting Unit, Percentage of Fair Value in Excess of Carrying Amount	14.20%
Mosaic Fertilizantes segment
Goodwill [Line Items]
Goodwill, net of accumulated amortization	$ 105.0
Foreign currency translation	(7.3)
Goodwill, net of accumulated amortization	97.7
Corporate, other and intersegment eliminations
Goodwill [Line Items]
Goodwill, net of accumulated amortization	12.1
Foreign currency translation	0.0
Goodwill, net of accumulated amortization	$ 12.1