Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Supplemental disclosure of cash flow information:
Interest paid	$ 0.3	$ 0.1
Non-cash investing and financing activities:
Stock repurchases not yet settled (accrued in accounts payable)	0.1	1.8
Unpaid purchases of property and equipment	$ 2.0	$ 1.3