Debt (Details 2) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	May 31, 2011
Revolving Loans
Revolving loans
Total Amount Committed by Lenders	$ 469.2
Outstanding Borrowings	112.5
Outstanding Letters of Credit	176.7
Total Amount Available	180.0
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	112.5
Outstanding Letters of Credit	0.5
Total Amount Available	137.0
Other revolving loans
Revolving loans
Total Amount Committed by Lenders	219.2
Outstanding Letters of Credit	176.2
Total Amount Available	$ 43.0