Capitalization (Narrative) (Details) - USD ($) $ in Thousands			1 Months Ended	3 Months Ended	12 Months Ended
	Jan. 08, 2024	Oct. 14, 2022	Jan. 31, 2023	Mar. 31, 2024	Dec. 31, 2023	Aug. 31, 2023
Debt Instrument [Line Items]
Issuance of common stock from forward equity sale agreement		$ 500,000
At Market Sales Agreements [Member]
Debt Instrument [Line Items]
Stock remaining available for sale, amount				$ 110,000
First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Face Amount						$ 225,000
First Mortgage Bonds Due In 2053 [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate						5.48%
Face Amount						$ 175,000
First Mortgage Bonds Due In 2061 [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate						5.56%
Face Amount						$ 50,000
Notes at 5.375%, due 2034 [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate	5.375%			5.375%	5.375%
Maturity date				2034	2034
Debt issuance expense	$ 4,610
Maturity Year	2034
Unsecured notes payable	$ 500,000			$ 500,000
Notes At 5.30%, Due 2052 [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate				5.30%	5.30%
Maturity date				2052	2052
Unsecured notes payable				$ 500,000	$ 500,000
Aqua Pennsylvania, Inc [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate			5.60%
Face Amount			$ 75,000
Maturity Year			2043