Debt (Details 2) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	May 31, 2011	Feb. 29, 2008
Revolving Loans
Revolving loans
Total Amount Committed by Lenders	$ 430.9
Outstanding Borrowings	20.0
Outstanding Letters of Credit	123.6
Total Amount Available	287.3
U.S. Dollar revolving loans under the Amended Credit Agreement
Revolving loans
Weighted Average Interest Rate (as a percent)	1.50%
Total Amount Committed by Lenders	250.0	250.0	230.0
Outstanding Borrowings	20.0
Outstanding Letters of Credit	0.5
Total Amount Available	229.5
Other revolving loans
Revolving loans
Total Amount Committed by Lenders	180.9
Outstanding Letters of Credit	123.1
Total Amount Available	$ 57.8