Debt - Revolving Loan Arrangements (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Revolving lines of credit
Total Amount Committed by Lenders	$ 732.7
Outstanding Borrowings	171.0
Outstanding Letters of Credit	131.5
Total Amount Available	430.2
Revolving Loans
Revolving lines of credit
Outstanding Letters of Credit	131.5	$ 137.7
Other lines of credit
Revolving lines of credit
Total Amount Committed by Lenders	232.7
Outstanding Letters of Credit	130.4
Total Amount Available	$ 102.3
2015 Credit Agreement | US Dollar revolving loan
Revolving lines of credit
Weighted Average Interest Rate (as a percent)	2.00%
Total Amount Committed by Lenders	$ 500.0
Outstanding Borrowings	171.0
Outstanding Letters of Credit	1.1
Total Amount Available	$ 327.9