Summary of Significant Accounting Policies (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2018
Sales And Receivables [Line Items]
Receivables, net	$ 838.5	$ 642.6		$ 660.8
Canadian resources taxes and royalties included in cost of goods sold	198.8	142.0	$ 121.6
Assets related to PIS and Cofins and income tax credits in Brazil	90.4
Expected Annualized Impact Of Change In Estimate On Depreciation And Operating Income	65.0
Accounts Payable and Accrued Liabilities, Current [Abstract]
Structured accounts payable arrangements	$ 572.8	386.2
Minimum | Machinery and equipment
Useful life	3 years
Minimum | Buildings and Leashold Improvements
Useful life	3 years
Maximum
Duration of short term investments in number of days	90 days
Maximum | Machinery and equipment
Useful life	25 years
Maximum | Buildings and Leashold Improvements
Useful life	40 years
Canpotex
Sales And Receivables [Line Items]
Net sales	$ 820.1	700.6	$ 604.5
Receivables, net		$ 37.8