Rate and Regulatory Matters (Narrative) (Details) $ in Thousands		1 Months Ended			12 Months Ended
	Mar. 01, 2019	Nov. 30, 2019 USD ($) Customer	Oct. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Regulatory Liabilities [Line Items]
Regulatory Liability - Cost of Utility Plant Removal					$ 69,152	$ 79,112
Corporate tax rate	3.35%
Regulatory liabilities					31,500	31,700
Deferred income tax benefits					$ (11,719)	(8,724)	$ 7,944
Maximum [Member]
Regulatory Liabilities [Line Items]
Corporate tax rate					35.00%
Minimum [Member]
Regulatory Liabilities [Line Items]
Corporate tax rate					21.00%
Pinelands Water Company [Member]
Regulatory Liabilities [Line Items]
Approved increase in annual operating revenues			$ 500
Pinelands Wastewater [Member]
Regulatory Liabilities [Line Items]
Approved increase in annual operating revenues			$ 500
Delaware Public Service Commission [Member]
Regulatory Liabilities [Line Items]
Percentage of consumer price index					3.00%
Maturity date					Dec. 31, 2029
Delaware Public Service Commission [Member] | Tidewater [Member]
Regulatory Liabilities [Line Items]
Approved increase in annual operating revenues					$ 500
Number of customers | Customer		1,000
Purchase of the wastewater utility assets		$ 1,800
New Jersey Board Of Public Utilities [Member] | Middlesex [Member]
Regulatory Liabilities [Line Items]
Approved increase in annual operating revenues		$ 500		$ 5,500
Additional annual costs					100
Base rate amount				$ 245,500
Return on equity				9.60%
Regulatory liabilities					24,200	$ 34,600
Deferred income tax benefits				$ 28,700
Amortization period				4 years
New Jersey Board Of Public Utilities [Member] | Pinelands Water Company [Member]
Regulatory Liabilities [Line Items]
Approved increase in annual operating revenues					500
New Jersey Board Of Public Utilities [Member] | Pinelands Wastewater [Member]
Regulatory Liabilities [Line Items]
Approved increase in annual operating revenues					700
Pennsylvania Public Utilities Commissio [Member] | Twin Lakes [Member]
Regulatory Liabilities [Line Items]
Approved increase in annual operating revenues					$ 200