Debt (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	May 31, 2011
Debt
Total debt	$ 355.7	$ 337.2
Current portion of long-term debt	(1.0)	(1.3)
Total long-term debt, less current portion	354.7	335.9
U.S. Dollar revolving loans under the Amended Credit Agreement
Debt
Total debt	112.5	93.0
Maximum commitment	250.0		250.0
Maximum leverage ratio	3.0
Minimum interest coverage ratio	3.0
U.S. Dollar revolving loans under the Amended Credit Agreement | Minimum
Debt
Interest rate added to base rate (as a percent)	0.80%
Facility fee (as a percent)	0.20%
U.S. Dollar revolving loans under the Amended Credit Agreement | Maximum
Debt
Interest rate added to base rate (as a percent)	1.65%
Facility fee (as a percent)	0.35%
U.S. Dollar revolving loans under the Amended Credit Agreement | LIBOR
Debt
Variable interest rate base	LIBOR
U.S. Dollar revolving loans under the Amended Credit Agreement | Adjusted LIBOR
Debt
Variable interest rate base	adjusted LIBOR
Interest rate added to base rate (as a percent)	1.00%
U.S. Dollar revolving loans under the Amended Credit Agreement | Federal Funds
Debt
Variable interest rate base	federal funds rate
Interest rate added to base rate (as a percent)	0.50%
U.S. Dollar revolving loans under the Amended Credit Agreement | Prime rate
Debt
Variable interest rate base	prime rate
Note Purchase Agreement
Debt
Total debt	240.0	240.0
Capital lease obligations and other loans
Debt
Total debt	$ 3.2	$ 4.2