Capitalization (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		12 Months Ended
	Nov. 30, 2019	May 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Aug. 31, 2019	Apr. 30, 2019	Sep. 30, 2018	Aug. 31, 2018	Mar. 31, 2018
Schedule of Capitalization [Line Items]
Issuance of Common Stock	$ 43,700
Public offering, price per share	$ 60.50
Issuance of Common Stock in a public offering, shares	800,000
Shares authorized			40,000,000	40,000,000
Issuance of shares under the DRP			$ 12,738	$ 1,150	$ 1,234
Additional Shares Authorized By SEC To Be Issued			400,000
Maximum number of shares authorized for grant			100,000
Preferred Stock, Shares Authorized			120,000	120,000
Preferred Stock, Shares Outstanding			20,000	23,000
Convertible preferred stock converted, value			$ 350
Amount drawn			78,967	$ 22,076	11,523
Long-term debt			234,397	162,904
Proceeds from issuance of first mortgage bond		$ 9,500
Deobligated principal payments			130
Other long term debt			83,000	61,500
Customer advances			$ 23,905	$ 22,572
All Long-term Debt [Member]
Schedule of Capitalization [Line Items]
Weighted average interest rate			3.17%	3.30%
First Mortgage Bonds - Series 2019A [Member]
Schedule of Capitalization [Line Items]
Long-term debt			$ 32,500
Interest rate			4.00%
Maturity date			Aug. 01, 2059
First Mortgage Bonds - Series 2019B [Member]
Schedule of Capitalization [Line Items]
Long-term debt			$ 21,200
Interest rate			5.00%
Maturity date			Aug. 01, 2059
Convertible Preferred Stock $7.00 Series [Member]
Schedule of Capitalization [Line Items]
Shares issued upon conversion			12
Percentage of stock that may be redeemed in a given calander year			10.00%
Convertible Preferred Stock $8.00 Series [Member]
Schedule of Capitalization [Line Items]
Shares issued upon conversion			3,000
Convertible preferred stock converted, shares			41,142
Convertible preferred stock converted, value			$ 300
Outside Director Stock Compensation Plan [Member]
Schedule of Capitalization [Line Items]
Authorized shares under plan			56,643
Common stock granted and issued under plan			3,521	4,004	3,976
Maximum number of shares authorized for grant			100,000
Preferred Stock, Shares Outstanding			100,000
New Jersey Infrastructure Bank [Member]
Schedule of Capitalization [Line Items]
Maximum borrowing capacity, construction loan								$ 8,700	$ 43,500
Percentage of principal with stated interest rate			75.00%
Percentage of principal with market interest rate			25.00%
Long-term debt			$ 82,700
Interest rate			0.00%
Deobligated principal payments			$ 100
Construction Loan [Member]
Schedule of Capitalization [Line Items]
Interest rate			0.00%
New Jersey Economic Development Authority [Member]
Schedule of Capitalization [Line Items]
Proceeds from issuance of first mortgage bond			$ 140,000
Maturity date			Dec. 31, 2022
New Jersey Infrastructure Bank [Member]
Schedule of Capitalization [Line Items]
Amount drawn			$ 31,800
First Mortgage Bonds [Member]
Schedule of Capitalization [Line Items]
Maximum borrowing capacity, construction loan			60,800			$ 53,700
Amount drawn			17,300
Amount of drawn expected remaining			43,800
New Jersey Economic Development Authority [Member]
Schedule of Capitalization [Line Items]
Long-term debt			109,100
Delaware State Revolving Fund [Member]
Schedule of Capitalization [Line Items]
Maximum borrowing amount				$ 10,000						$ 900
Maximum borrowing capacity, construction loan			1,300				$ 1,700
Series 2018A [Member]
Schedule of Capitalization [Line Items]
Proceeds from issuance of first mortgage bond		$ 7,100
Interest rate		0.00%
Maturity date		Aug. 01, 2047
Series 2018A [Member] | Minimum [Member]
Schedule of Capitalization [Line Items]
Interest rate		3.00%
Series 2018A [Member] | Maximum [Member]
Schedule of Capitalization [Line Items]
Interest rate		5.00%
Series 2018B [Member]
Schedule of Capitalization [Line Items]
Proceeds from issuance of first mortgage bond		$ 2,400
Maturity date		Aug. 01, 2047
Amortizing Secured Notes [Member]
Schedule of Capitalization [Line Items]
Long-term debt			33,600
Series 2019A [Member]
Schedule of Capitalization [Line Items]
Interest rate						4.00%
Dividend Reinvestment and Common Stock Purchase Plan [Member]
Schedule of Capitalization [Line Items]
Issuance of Common Stock			$ 12,700
Dividend Reinvestment & Common Stock Purchase Plan, cumulative shares			200,000