Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Supplemental Cash Flow Information
Cash paid for interest	$ 2.6	$ 1.1	$ 0.7
Capitalized interest	0.3	0.4	0.6
Income taxes paid, net of refunds	9.5	13.9	17.7
Non-cash increase (decrease) in accounts payable and accrued liabilities for changes in unpaid capital expenditures	$ 1.9	$ (0.1)	$ 1.7