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Acquisition of Mosaic Fertilizantes P&K S.A. (Details) $ / shares in Units, $ in Millions				3 Months Ended	12 Months Ended
	Jan. 08, 2018 USD ($) $ / shares shares	Dec. 28, 2017 USD ($) shares	Dec. 19, 2016 USD ($) shares	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($) $ / shares	Dec. 31, 2017 USD ($) $ / shares	Dec. 31, 2016 USD ($)	Dec. 31, 2019 USD ($)
Business Acquisition [Line Items]
Long-term receivable					$ 91.7	$ 0.0
Recoverable taxes					352.7	492.1
Indemnification asset					30.7	0.0
Business Acquisition, Pro Forma Revenue						8,605.7
Payments to Acquire Businesses, Gross					$ 985.3	$ 0.0	$ 0.0
Common Stock, Par or Stated Value Per Share \| $ / shares					$ 0.01	$ 0.01
Goodwill, Acquired During Period					$ 96.2
Business Acquisition, Pro Forma Net Income (Loss)						$ (43.3)
Business Acquisition, Pro Forma Earnings Per Share, Basic \| $ / shares						$ (0.11)
Business Acquisition, Pro Forma Earnings Per Share, Diluted \| $ / shares						$ (0.11)
Miski Mayo Mine
Business Acquisition [Line Items]
Equity Method Investment, Ownership Percentage						35.00%
Vale Fertilizantes S.A. [Member]
Business Acquisition [Line Items]
Long-term receivable	$ 116.3
Recoverable taxes	101.6
Indemnification asset	37.2
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets	638.1
Payments to Acquire Businesses, Gross	$ 1,080.0	$ 1,150.0	$ 1,250.0
Business acquisition - noncash consideration \| shares	34,176,574	34,176,574	42,286,874
Common Stock, Par or Stated Value Per Share \| $ / shares	$ 0.01
Share Price \| $ / shares	$ 26.92
Business Combination, Contingent Consideration, Liability, Noncurrent					12.4
Business Combination, Contingent Consideration, Liability, Noncurrent Expiration					130.0
Number of phosphate rock mines acquired	5
Number of chemical plants acquired	4
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment	$ 2,503.2
Goodwill, Acquired During Period	96.2
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Assets Noncurrent	48.3
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Liabilities Noncurrent	128.3
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Asset Retirement Obligations	247.3
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Noncurrent Assets	292.2
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets	3,578.0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Long-term Debt	6.7
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Financial Liabilities	98.2
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Accounts Payable	373.3
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities	478.2
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt	64.6
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Other	215.3
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities	1,133.7
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net	2,444.3
Noncontrolling Interest, Increase from Business Combination	(453.0)
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents	86.0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Receivables	100.3
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Inventory	344.2
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Other	107.6
Business Combination, Consideration Transferred, Other	$ 1,905.3
Business Combination, Acquisition and Integration costs					45.3	$ 26.2
Business Combination, Separately Recognized Transactions, Revenues and Gains Recognized					1,300.0
Business Combination, Separately Recognized Transactions, Net Gains and Losses					83.6
Vale Fertilizantes S.A. [Member] \| Maximum
Business Acquisition [Line Items]
Business Acquisition, Addition To Board Of Directors	2
Vale Fertilizantes S.A. [Member] \| Estimate \| Maximum
Business Acquisition [Line Items]
Business Combination, Contingent Consideration, Liability, Noncurrent								$ 260.0
Miski Mayo Joint Venture [Member]
Business Acquisition [Line Items]
Business Acquisition, Percentage of Voting Interests Acquired	40.00%
Business Combination, Step Acquisition, Equity Interest in Acquiree, Including Subsequent Acquisition, Percentage	75.00%
Brazil Landco [Member]
Business Acquisition [Line Items]
Business Acquisition, Percentage of Voting Interests Acquired	49.00%
Vale Fertilizantes S.A. [Member]
Business Acquisition [Line Items]
Costs and Expenses, Related Party				$ 11.1
Phosphates Segment [Member]
Business Acquisition [Line Items]
Goodwill, Acquired During Period					96.2
Phosphates Segment [Member] \| Vale Fertilizantes S.A. [Member]
Business Acquisition [Line Items]
Goodwill, Acquired During Period					$ 96.2
Brazil Landco [Member]
Business Acquisition [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	51.00%