Rate and Regulatory Matters (Details) - USD ($) $ in Thousands	1 Months Ended	6 Months Ended
	Oct. 17, 2017	Jun. 30, 2018	Jun. 30, 2017
Regulatory Liabilities [Line Items]
Deferred income tax benefits		$ (2,760)	$ 4,395
Regulatory liabilities		$ 32,600
Minimum [Member]
Regulatory Liabilities [Line Items]
Corporate tax rate		21.00%
Base rate amount		$ 4,900
Maximum [Member]
Regulatory Liabilities [Line Items]
Corporate tax rate		35.00%
Base rate amount		$ 10,400
Middlesex [Member]
Regulatory Liabilities [Line Items]
Base rate amount	$ 15,300
Deferred income tax benefits		$ 28,700
Amortization period		4 years
Middlesex [Member] | New Jersey Board Of Public Utilities [Member]
Regulatory Liabilities [Line Items]
Approved increase in annual operating revenues		$ 5,500
Base rate amount		$ 245,500
Return on equity		9.60%
Tidewater Utilities Inc [Member]
Regulatory Liabilities [Line Items]
Projected annual revenue		$ 200