Employee Benefit Plans (Details) - Schedule of recognized in accumulated other comprehensive loss (USD $) In Millions, unless otherwise specified	May 31, 2013	May 31, 2012
Employee Benefit Plans (Details) - Schedule of recognized in accumulated other comprehensive loss [Line Items]
Net actuarial gain (loss)	$ (75.5)	$ (95.6)
Net prior service credit	0.5	0.8
Net amount recognized in Accumulated other comprehensive income (loss)	(75.0)	(94.8)
Pension Plan, Defined Benefit [Member]
Employee Benefit Plans (Details) - Schedule of recognized in accumulated other comprehensive loss [Line Items]
Net actuarial gain (loss)	(62.1)	(76.4)
Net amount recognized in Accumulated other comprehensive income (loss)	(62.1)	(76.4)
Other Postretirement Benefit Plan, Defined Benefit [Member]
Employee Benefit Plans (Details) - Schedule of recognized in accumulated other comprehensive loss [Line Items]
Net actuarial gain (loss)	(13.4)	(19.2)
Net prior service credit	0.5	0.8
Net amount recognized in Accumulated other comprehensive income (loss)	$ (12.9)	$ (18.4)