Income Taxes Effective tax rate (Details 2) (USD $) In Millions, unless otherwise specified	12 Months Ended
May 31, 2013	May 31, 2012	May 31, 2011
The components of earnings from consolidated companies before income taxes, and the effects of significant adjustments to tax computed at the federal statutory rate, were as follows:
United States earnings	$ 1,158.1	$ 1,412.7	$ 1,477.5
Non-U.S. earnings	1,056.4	1,216.2	1,793.8
Earnings from consolidated companies before income taxes	2,214.5	2,628.9	3,271.3
Effective Income Tax Rate Continuing Operations Tax Rate Reconciliation [Abstract]
Computed tax at the federal statutory rate of 35%	35.00%	35.00%	35.00%
State and local income taxes, net of federal income tax benefit	1.60%	1.60%	1.30%
Percentage depletion in excess of basis	(7.10%)	(6.60%)	(4.50%)
Impact of offshore earnings	(10.20%)	(2.90%)	(7.50%)
Change in valuation allowance	(3.60%)	0.40%	0.50%
Other items (none in excess of 5% of computed tax)	(0.30%)	(0.40%)	(1.80%)
Effective tax rate	15.40%	27.10%	23.00%
IncomeTaxExpenseBenefitContinuingOperationsIncomeTaxReconciliationAbstract
Tax impact from sale of Fosfertil	$ 341.0	$ 711.4	$ 752.8

A ratio calculated by dividing the reported amount of income tax expense attributable to continuing operations for the period by GAAP-basis pretax income from continuing operations.

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The domestic federal statutory tax rate applicable under enacted tax laws to the Company's pretax income from continuing operations for the period. The "statutory" tax rate is the regular tax rate if there are alternative tax systems.

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The portion of the difference between the effective income tax rate and domestic federal statutory income tax rate attributable to changes in the valuation allowance for deferred tax assets.

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The portion of the difference between the effective income tax rate and domestic federal statutory income tax rate that can be explained by the different methods of depletion allowed under generally accepted accounting principles and enacted tax laws.

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The portion of the difference between the effective income tax rate and domestic federal statutory income tax rate attributable to all other items not otherwise listed in the existing taxonomy.

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The portion of the difference between the effective income tax rate and domestic federal statutory income tax rate that can be explained by the state and local income tax expense or benefit, net of the federal tax benefit (expense) thereon, recorded during the period.

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The portion of earnings or loss from continuing operations before income taxes that is attributable to domestic operations.

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The portion of earnings or loss from continuing operations before income taxes that is attributable to foreign operations, which is defined as Income or Loss generated from operations located outside the entity's country of domicile.

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Sum of operating profit and nonoperating income or expense before Income or Loss from equity method investments, income taxes, extraordinary items, and noncontrolling interest.

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The sum of the current income tax expense or benefit and the deferred income tax expense or benefit pertaining to continuing operations.

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