Quarterly report pursuant to Section 13 or 15(d)

Commitments and Contingent Liabilities (Details)

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Commitments and Contingent Liabilities (Details) - USD ($)
$ in Thousands
Jun. 30, 2018
Dec. 31, 2017
Dec. 31, 2005
Soil and Groundwater Contamination      
Loss Contingencies      
Accrual for environmental loss contingencies $ 821 $ 837  
Subsurface Remedial and Wetlands/Marsh Management      
Loss Contingencies      
Accrual for environmental loss contingencies 1,107 1,245  
Subsurface Remediation and Soil Vapor Extraction      
Loss Contingencies      
Accrual for environmental loss contingencies 1,080 1,220  
New Jersey Locations | PCB Remediation      
Loss Contingencies      
Accrual for environmental loss contingencies 948 842 $ 500
Chester And Baltimore Facilities | PCB Remediation      
Loss Contingencies      
Accrual for environmental loss contingencies $ 670 $ 701