Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Supplemental disclosure of cash flow information:
Interest paid	$ 17.7	$ 22.1	$ 25.6
Non-cash investing and financing activities:
Stock repurchases not yet settled (accrued in accounts payable)	1.8	0.2	0.8
Unpaid purchases of property and equipment	4.6	10.5	1.8
Purchases of property and equipment through capital leasing arrangements	$ 0.2	$ 0.0	$ 0.0