Retirement Plans - Plan Assets and Estimated Future Benefit Payments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Retirement plans
Expected contribution in next fiscal year	$ 0.5
Estimated future benefit payments
Fiscal 2017	1.0
Fiscal 2018	1.0
Fiscal 2019	1.0
Fiscal 2020	1.0
Fiscal 2021	1.1
Fiscal 2022 ‑ Fiscal 2026	$ 6.6
Target and actual asset allocations
Total target plan assets	100.00%
Total actual plan assets	100.00%
Total assets	$ 21.7	$ 13.9	$ 32.5
United States Retirement Plan
Target and actual asset allocations
Expected long-term return assumption (percentage)	7.00%
Canadian Retirement Plan
Target and actual asset allocations
Expected long-term return assumption (percentage)	5.50%
Equity securities
Target and actual asset allocations
Total target plan assets	60.00%
Total actual plan assets	74.51%
Debt securities
Target and actual asset allocations
Total target plan assets	40.00%
Total actual plan assets	22.53%
Other
Target and actual asset allocations
Total target plan assets	0.00%
Total actual plan assets	2.96%
U.S. equity
Target and actual asset allocations
Total assets	$ 12.5	7.7
International equity
Target and actual asset allocations
Total assets	3.7	2.7
Total equity based funds
Target and actual asset allocations
Total assets	16.2	10.4
Common/collective trust - fixed income
Target and actual asset allocations
Total assets	4.9	2.9
Money market funds
Target and actual asset allocations
Total assets	$ 0.6	$ 0.6