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Commitments and Contingent Liabilities (Details) - USD ($) $ in Thousands | Mar. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2005
--- | --- | --- | ---
Soil and Groundwater Contamination |  |  |
Loss Contingencies |  |  |
Accrual for environmental loss contingencies | $ 837 | $ 837 |
Subsurface Remedial and Wetlands/Marsh Management |  |  |
Loss Contingencies |  |  |
Accrual for environmental loss contingencies | 1,183 | 1,245 |
Subsurface Remediation and Soil Vapor Extraction |  |  |
Loss Contingencies |  |  |
Accrual for environmental loss contingencies | 1,183 | 1,220 |
New Jersey Locations | PCB Remediation |  |  |
Loss Contingencies |  |  |
Accrual for environmental loss contingencies | 837 | 842 | $ 500
Chester And Baltimore Facilities | PCB Remediation |  |  |
Loss Contingencies |  |  |
Accrual for environmental loss contingencies | $ 463 | $ 701 |

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- Definition Total costs accrued as of the balance sheet date for environmental loss contingencies. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14326-108349 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 30 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13207-110859 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 25 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6395460&loc=d3e13647-108346 + Details
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