Contingencies (Details) $ in Millions	12 Months Ended
	Dec. 31, 2014 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Aug. 31, 2016	Dec. 31, 2013 USD ($)
Applicability, Impact and Conclusion of Environmental Loss Contingencies [Abstract]
Environmental contingency accrual		$ 33.2	$ 39.3
New Wales water loss incident
Loss Contingencies [Line Items]
Number Of Cells With Sinkholes				1
Number Of Cells In The Active Stack				2
Brazilian subsidiary judicial and administrative proceedings
Loss Contingencies [Line Items]
Maximum potential liabilitiy		69.3
Brazilian subsidiary labor claims
Loss Contingencies [Line Items]
Loss Contingency Accrual		55.9
Brazilian subsidiary Potash Mine occupational hazard
Loss Contingencies [Line Items]
Loss Contingency Accrual		2.1
Catalao overtime pay matter
Loss Contingencies [Line Items]
Loss Contingency Accrual		2.2
Brazilian subsidiary environmental claims
Loss Contingencies [Line Items]
Loss Contingency Accrual		4.1
Brazilian subsidiary other civil contingent liabilities and other claims
Loss Contingencies [Line Items]
Maximum potential liabilitiy		9.2
Uberaba gypstacks settled litigation
Loss Contingencies [Line Items]
Loss Contingency, Damages Awarded, Value	$ 0.3
Uberaba EHS Class Action pending litigation
Loss Contingencies [Line Items]
Maximum potential liabilitiy					$ 27.9
Brazilian subsidiary indemnification of mining rights exploration costs
Loss Contingencies [Line Items]
Loss Contingency Accrual		0.1
Tapira Overtime Pay Matter
Loss Contingencies [Line Items]
Loss Contingency Accrual		5.9
Sergipe Overime Pay Matter
Loss Contingencies [Line Items]
Loss Contingency Accrual		3.9
Maximum | Brazilian subsidiary judicial and administrative proceedings
Loss Contingencies [Line Items]
Maximum potential liabilitiy		900.0
Maximum | Brazilian Non Income Tax Proceedings
Loss Contingencies [Line Items]
Maximum potential liabilitiy		344.0
Maximum | Brazilian Non Income Tax Proceedings | Indemnification Agreement Vale S.A.
Loss Contingencies [Line Items]
Maximum potential liabilitiy		166.0
Maximum | Brazilian Non Income Tax Proceedings | PIS And Cofins Cases
Loss Contingencies [Line Items]
Maximum potential liabilitiy		233.0
Maximum | Brazilian subsidiary labor claims
Loss Contingencies [Line Items]
Maximum potential liabilitiy		607.4
Maximum | Brazilian subsidiary environmental claims
Loss Contingencies [Line Items]
Maximum potential liabilitiy		115.0
Maximum | Brazilian subsidiary other civil contingent liabilities and other claims
Loss Contingencies [Line Items]
Maximum potential liabilitiy		144.0
Maximum | Brazilian subsidiary indemnification of mining rights exploration costs
Loss Contingencies [Line Items]
Maximum potential liabilitiy		13.0
Minimum | New Wales water loss incident
Loss Contingencies [Line Items]
Financial assurance to support off-site monitoring and sinkhole remediation costs		$ 40.0