Investments in Non-Consolidated Companies (Details 2) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Equity Method Investment, Summarized Financial Information, Income Statement
Net sales	$ 2,871.2	$ 2,307.9	$ 3,787.4
Net earnings	95.3	11.9	30.2
Mosaic’s share of equity in net earnings (loss)	16.7	(15.4)	(2.4)
Equity Method Investment Summarized Financial Information Balance Sheet
Total assets	8,623.6	8,665.4	6,745.4
Total liabilities	5,971.9	6,310.1	4,698.6
Mosaic's share of equity in net assets	$ 712.8	$ 651.5	$ 589.3

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