Debt (Details 2) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Feb. 29, 2008
Revolving Loans
Revolving loans
Total Amount Committed by Lenders	$ 435.5
Outstanding Borrowings	93.0
Outstanding Letters of Credit	143.2
Total Amount Available	199.3
U.S. Dollar revolving loans under the Amended Credit Agreement
Revolving loans
Weighted Average Interest Rate (as a percent)	1.40%
Total Amount Committed by Lenders	250.0	250.0	230.0
Outstanding Borrowings	93.0
Outstanding Letters of Credit	1.5
Total Amount Available	155.5
Other revolving loans
Revolving loans
Total Amount Committed by Lenders	185.5
Outstanding Letters of Credit	141.7
Total Amount Available	$ 43.8