Note 16 - Contingencies (Details Textual)	6 Months Ended
	Jun. 30, 2019 USD ($) mi² Subsidiary Site	Dec. 31, 2018 USD ($)
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies	$ 17,101,000	$ 17,411,000
Accrual for environmental loss contingencies, period increase (decrease)	350,000
Accrual for environmental loss contingencies, payments	660,000
Bayonne [Member]
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies	533,000
Clifton and Carlstadt [Member]
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies	1,734,000
Berrys Creek Site [Member]
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies	$ 9,502,000
Number of subsidiaries notice received | Subsidiary	2
Environmental exit costs, reasonably possible losses, estimated share	2.40%
Maybrook Site [Member]
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies	$ 365,000
Harriman Site [Member]
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies	3,365,000
Harriman Site [Member] | Minimum [Member]
Loss Contingencies [Line Items]
Site contingency loss exposure, estimated range	2,000,000
Harriman Site [Member] | Maximum [Member]
Loss Contingencies [Line Items]
Site contingency loss exposure, estimated range	7,000,000
Scientific Chemical Processing SCP Superfund Site [Member]
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies	$ 732,000
Number of other sites named PRP of SCP superfund site | Site	130
Site contingency, recovery from third party of environmental remediation cost	$ 468,000
Newark Bay Complex Litigation [Member]
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies	$ 0
Site contingency clean up plan, miles of clean up | mi²	8.3
Amount of estimated cost to clean up site that the company is not exposed	$ 1,380,000,000
Other Non-current Liabilities [Member]
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies	$ 16,462,000	$ 16,599,000