Retirement Plans - Plan Assets and Estimated Future Benefit Payments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Retirement plans
Expected contribution in next fiscal year	$ 1.2
Estimated future benefit payments
Fiscal 2020	1.1
Fiscal 2021	1.1
Fiscal 2022	1.2
Fiscal 2023	1.2
Fiscal 2024	1.3
Fiscal 2025 ‑ Fiscal 2028	$ 8.0
Target and actual asset allocations
Total target plan assets	100.00%
Total actual plan assets	100.00%
Total assets	$ 27.0	$ 22.2	$ 25.3
United States Retirement Plan
Target and actual asset allocations
Expected long-term return assumption (percentage)	6.50%
Canadian Retirement Plan
Target and actual asset allocations
Expected long-term return assumption (percentage)	5.00%
Total equity based funds
Target and actual asset allocations
Total target plan assets	60.00%
Total actual plan assets	55.70%
Total assets	$ 15.0	17.7
Debt securities
Target and actual asset allocations
Total target plan assets	40.00%
Total actual plan assets	44.00%
Other
Target and actual asset allocations
Total target plan assets	0.00%
Total actual plan assets	0.30%
U.S. equity
Target and actual asset allocations
Total assets	$ 5.5	14.1
International equity
Target and actual asset allocations
Total assets	9.5	3.6
Common/collective trust - fixed income
Target and actual asset allocations
Total assets	11.9	4.4
Money market funds
Target and actual asset allocations
Total assets	$ 0.1	$ 0.1