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Commitments and Contingent Liabilities (Narrative) (Details) $ in Thousands | 12 Months Ended
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Dec. 31, 2018 USD ($) gal | Dec. 31, 2017 USD ($)
Commitment And Contingencies [Line Items] |  |
Guarant liabilty for AWM's performance | $ 1,500 | $ 100
Budgeted construction cost for construction program, 2019 | 118,000 |
Budgeted construction cost for construction program, 2020 | 101,000 |
Budgeted construction cost for construction program, 2021 | 76,000 |
Rental expenses under operating leases | $ 500 | $ 100
Rental commitment under operating lease terms | 5 years |
Estimated obligation expend | $ 28,000 |
NJ Water Supply Authority [Member] |  |
Commitment And Contingencies [Line Items] |  |
Purchase commitment expiration date of contract | Nov. 30, 2023 |
Water purchase per commitment | gal | 27,000 |
Regulated Water Authority [Member] |  |
Commitment And Contingencies [Line Items] |  |
Purchase commitment expiration date of contract | Feb. 27, 2021 |
Water purchase per commitment | gal | 3,000 |
City of Dover [Member] |  |
Commitment And Contingencies [Line Items] |  |
Water purchase per commitment | gal | 15,000 |

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- Definition This item represents a non-contingent liability for the fair value of an obligation to stand ready to perform over the term of a guaranty issued in the event that specified triggering events or conditions occur. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.15) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.15) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 460 -SubTopic 10 -Section 25 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=82913062&loc=d3e11019-110243 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 460 -SubTopic 10 -Section 25 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=82913062&loc=d3e11049-110243 + Details
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