Commitments and Contingent Liabilities (Narrative) (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) gal	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Guaranty liabilty for AWM's performance	$ 1,500		$ 1,500		$ 1,500
Budgeted construction cost for construction program, 2018			116,000
Contractual construction agreements			77,000
Rental expenses under operating leases	$ 100	$ 100	$ 300	$ 100
Estimated incremental borrowing rate	4.03%		4.03%
Lease maturity date			2030
NJ Water Supply Authority [Member]
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Purchase commitment expiration date of contract			Nov. 30, 2023
Water purchase per commitment | gal			27,000,000
Regulated Water Authority [Member]
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Purchase commitment expiration date of contract			Feb. 27, 2021
Water purchase per commitment | gal			3,000,000
City of Dover [Member]
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Water purchase per commitment | gal			15,000,000