Commitments and Contingencies - Narrative (Details) $ in Millions	3 Months Ended			9 Months Ended	12 Months Ended
	Sep. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jun. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2017 CAD ($)	Jul. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Jul. 07, 2016 USD ($)
Rochester, New Hampshire
Loss Contingencies [Line Items]
Expense associated with expected costs of site investigation		$ 100,000	$ 200,000
Rochester, New Hampshire | Environmental Contamination
Loss Contingencies [Line Items]
Reduction to accrual for environmental liability, payments						$ 200,000
Accrual for environmental liability, including revision (fully offset)	$ 0			$ 0		200,000	$ 100,000
Revision of estimate for environmental liability accrual	100,000
Accrual for environmental liability						0
Texel | Quebec, Canada
Loss Contingencies [Line Items]
Indemnification assets, minimum estimated outcome												$ 900,000
Indemnification assets, maximum estimated outcome										$ 1,500,000		$ 1,500,000
Environment remediation indemnity secured by environmental escrow account	2,300,000			2,300,000					$ 3.0
Environmental remediation indemnity secured by general escrow account	10,800,000			10,800,000					14.0
Environmental remediation indemnity secured by general escrow account, reduced amount after share purchase agreement	5,400,000			5,400,000					$ 7.0
Texel | Quebec, Canada | Environmental Contamination
Loss Contingencies [Line Items]
Reduction to accrual for environmental liability, payments				600,000		700,000
Accrual for environmental liability, including revision (fully offset)	200,000			200,000		$ 800,000		$ 1,500,000
Revision of estimate for environmental liability accrual				(600,000)
Accrual for environmental liability	$ 200,000			$ 200,000							$ 900,000
Forecast | Rochester, New Hampshire
Loss Contingencies [Line Items]
Expense associated with expected costs of site investigation					$ 200,000