Capitalization (Narrative) (Details) - USD ($) $ in Millions	1 Months Ended	6 Months Ended
	May 31, 2022	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021	Nov. 30, 2021
Schedule of Capitalization [Line Items]
Other long term debt		$ 1,606.0		$ 2,123.0
Customer advances for construction		$ 229.0		23.5
Common Stock [Member]
Schedule of Capitalization [Line Items]
Issuance of common stock		76,550	7,787
Proceeds amount		$ 7.0	$ 0.6
Delaware SRF Program [Member]
Schedule of Capitalization [Line Items]
Maximum borrowing capacity, construction loan					$ 50.0
First Mortgage Bonds [Member]
Schedule of Capitalization [Line Items]
Other long term debt	$ 52.2
Maturity date	Aug. 01, 2056
First Mortgage Bonds [Member] | Series 2022A [Member]
Schedule of Capitalization [Line Items]
Other long term debt	$ 16.2
Interest rate	2.70%
First Mortgage Bonds [Member] | Series 2022B [Member]
Schedule of Capitalization [Line Items]
Other long term debt	$ 360.0
Interest rate	3.00%
Tidewater [Member]
Schedule of Capitalization [Line Items]
Maximum borrowing capacity, construction loan		$ 2.2		$ 50.0
Interest rate				2.00%
Dividend Reinvestment and Common Stock Purchase Plan [Member]
Schedule of Capitalization [Line Items]
Percentage of discount purchase of common stock in investment plan		3.00%
Number of shares offering for discount		200,000
Remaing shares available		93,000