Debt - Revolving Loan Arrangements (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Revolving Loans
Revolving loans
Total Amount Committed by Lenders	$ 734.4
Outstanding Borrowings	25.0
Outstanding Letters of Credit	137.7	$ 150.3
Total Amount Available	571.7
Other lines of credit
Revolving loans
Total Amount Committed by Lenders	234.4
Outstanding Letters of Credit	136.7
Total Amount Available	$ 97.7
2015 Credit Agreement | US Dollar revolving loans
Revolving loans
Weighted Average Interest Rate (as a percent)	1.50%
Total Amount Committed by Lenders	$ 500.0
Outstanding Borrowings	25.0
Outstanding Letters of Credit	1.0
Total Amount Available	$ 474.0