Debt (Details 3) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014	May. 31, 2011
Revolving Loans
Revolving loans
Total Amount Committed by Lenders	$ 462.8
Outstanding Borrowings	129.5
Outstanding Letters of Credit	134.9	$ 150.3
Total Amount Available	198.4
Other revolving lines of credit
Revolving loans
Total Amount Committed by Lenders	212.8
Outstanding Letters of Credit	132.2
Total Amount Available	$ 80.6
Amended Credit Agreement | US Dollar revolving loans
Revolving loans
Weighted Average Interest Rate (as a percent)	1.50%
Total Amount Committed by Lenders	$ 250.0		$ 250.0
Outstanding Borrowings	129.5
Outstanding Letters of Credit	2.7
Total Amount Available	$ 117.8