Rate and Regulatory Matters (Details) - USD ($) $ in Millions	1 Months Ended	9 Months Ended	12 Months Ended
	Jul. 31, 2019	Sep. 30, 2020	Dec. 31, 2019
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			$ 0.5
New Jersey Board Of Public Utilities [Member] | Middlesex [Member]
Regulatory Liabilities [Line Items]
Approved increase in annual operating revenues		$ 0.6
Pennsylvania Public Utilities Commissio [Member] | Twin Lakes [Member]
Regulatory Liabilities [Line Items]
Approved increase in annual operating revenues	$ 0.2	$ 0.1