Investments in Non-Consolidated Companies - MWSPC Joint Venture (Details) t in Millions, $ in Millions		12 Months Ended
		Dec. 31, 2015 USD ($) financialinstitution t	Jan. 31, 2016 USD ($)	Dec. 31, 2014 USD ($)
Schedule of Equity Method Investments
Future capital commitment	[1]	$ 120.0		$ 0.0
Investments in nonconsolidated companies		980.5		$ 849.8
Mosaic investment in MWSPC Joint Venture
Schedule of Equity Method Investments
Future capital commitment		$ 120.0
Percentage of joint venture production Mosaic expects to market		25.00%
Investments in nonconsolidated companies		$ 608.0
Future Cash Payments To Acquire Interest In Joint Venture		362.0
Mosaic investment in MWSPC Joint Venture | Maximum
Schedule of Equity Method Investments
Mosaic's exposure in MWSPC credit facility		200.0
Total cash investment from investors to acquire interest in MWSPC		850.0
MWSPC Joint Venture
Schedule of Equity Method Investments
Aggregate cost of investment in phosphates greenfield mine including Mosaic's portion		$ 8,000.0
Annual production of finished product (Tonnes) | t		3.5
Number of lenders in MWSPC credit facility | financialinstitution		20
MWSPC line of credit facility, maximum borrowing capacity		$ 5,000.0
Expected amount of subsidy from government		$ 404.0
After project completion, number of months of shareholder tax amounts and severance fees for which the joint venture parties may have exposure		36 months
MWSPC Joint Venture | Subsequent Event
Schedule of Equity Method Investments
MWSPC line of credit facility, maximum borrowing capacity			$ 1,100.0
MWSPC Joint Venture | Minimum
Schedule of Equity Method Investments
Expected amount of subsidy from government		$ 260.0
MWSPC Joint Venture | Maximum
Schedule of Equity Method Investments
Total cash investment from investors to acquire interest in MWSPC		$ 2,400.0

[1] Future capital commitment for a non-consolidated company as discussed in Note 8 of our Notes to Consolidated Financial Statements.