Supplemental Cash Flow Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Supplemental disclosure of cash flow information:
Interest paid	$ 0.4	$ 0.4
Income taxes paid	0.7	0.2
Supplemental disclosure of non-cash transactions:
Stock repurchases not yet settled (accrued in accounts payable)	1.5	0
Non-cash capital expenditures	2.7	1.8
Capital leases acquired	$ 0.1	$ 0