Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Supplemental disclosure of cash flow information:
Interest paid	$ 13.3	$ 12.1
Non-cash investing and financing activities:
Stock repurchases not yet settled (accrued in accounts payable)	0.1	0.3
Unpaid purchases of property and equipment	$ 3.8	$ 1.1