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Commitments and Contingent Liabilities (Narrative) (Details) $ in Thousands	12 Months Ended
	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

Budgeted construction cost for construction program, next year

+ References

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- Definition

Budgeted construction cost for construction program, year one.

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- Definition

Budgeted construction cost for construction program, year two

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- Definition

Commitment And Contingencies [Line Items].

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- Definition

Estimated obligation expend.

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- Definition

The expiration date of a long-term purchase commitment.

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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
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- Definition

Amount of rent expense incurred for leased assets, including but not limited to, furniture and equipment, that is not directly or indirectly associated with the manufacture, sale or creation of a product or product line.

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- Definition

Term of lessor's operating lease renewal, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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Number of units of goods that must be purchased within the specified time period of the agreement to avoid penalties or unfavorable effects on pricing, among other adverse consequences.

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