Debt (Details 2) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	May 31, 2011
Revolving Loans
Revolving loans
Total Amount Committed by Lenders	$ 432.8
Outstanding Borrowings	93.0
Outstanding Letters of Credit	144.1
Total Amount Available	195.7
U.S. Dollar revolving loans under the Amended Credit Agreement
Revolving loans
Weighted Average Interest Rate (as a percent)	1.30%
Total Amount Committed by Lenders	250.0	250.0
Outstanding Borrowings	93.0
Outstanding Letters of Credit	1.8
Total Amount Available	155.2
Other revolving loans
Revolving loans
Total Amount Committed by Lenders	182.8
Outstanding Letters of Credit	142.3
Total Amount Available	$ 40.5