Acquisitions (Details) $ in Thousands		1 Months Ended								3 Months Ended						9 Months Ended		12 Months Ended
	Aug. 06, 2021 USD ($) customer	Aug. 31, 2022 USD ($) customer	Jul. 31, 2022 USD ($)	Mar. 31, 2022 USD ($) customer	Oct. 31, 2021 USD ($) customer	Jul. 31, 2021 USD ($) customer	Apr. 30, 2021 USD ($) customer	Jan. 31, 2021 USD ($) customer	Sep. 30, 2019 USD ($) item customer	Sep. 30, 2022 USD ($)	Jun. 30, 2022 USD ($)	Mar. 31, 2022 USD ($)	Sep. 30, 2021 USD ($)	Jun. 30, 2021 USD ($)	Mar. 31, 2021 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Dec. 31, 2021 USD ($) customer
Business Acquisition [Line Items]
Goodwill										$ 2,340,792						$ 2,340,792		$ 2,340,815
Operating revenues										434,618			$ 361,860			1,582,649	$ 1,342,457
Net income										$ 68,638	$ 82,291	$ 199,376	$ 50,503	$ 80,914	$ 183,689	$ 350,305	$ 315,106
Wastewater Utility System [Member]
Business Acquisition [Line Items]
Total purchase price			$ 885,000
Illinois [Member] | Water Utility System [Member]
Business Acquisition [Line Items]
Number of customers | customer	6,500
Total purchase price	$ 32,100
Illinois [Member] | Water And Wastewater Utility Systems [Member]
Business Acquisition [Line Items]
Number of customers | customer							4,000
Total purchase price							$ 12,500
Illinois [Member] | Wastewater Utility System [Member]
Business Acquisition [Line Items]
Number of customers | customer					7,600
Total purchase price					$ 41,250
Pennsylvania [Member] | Water Utility System [Member]
Business Acquisition [Line Items]
Number of customers | customer						2,930
Total purchase price						$ 12,000
Pennsylvania [Member] | Wastewater Utility System [Member]
Business Acquisition [Line Items]
Number of customers | customer								2,300
Total purchase price								$ 17,500
Delaware [Member] | Wastewater Utility System [Member]
Business Acquisition [Line Items]
Number of customers | customer									16,000
Retail customers | customer									198,000
Municipalities | item									42
Total purchase price									$ 276,500
Texas [Member] | Water Utility System [Member]
Business Acquisition [Line Items]
Number of customers | customer	992
Total purchase price	$ 4,000
Village of Frankfort [Member] | Water And Wastewater Utility Systems [Member]
Business Acquisition [Line Items]
Number of customers | customer		1,422
Total purchase price		$ 1,400
East Whiteland Township [Member] | Wastewater Utility System [Member]
Business Acquisition [Line Items]
Number of customers | customer		3,895
Total purchase price		$ 54,374
Lower Makefield Township [Member] | Wastewater Utility System [Member]
Business Acquisition [Line Items]
Number of customers | customer				11,000
Total purchase price				$ 53,000
Southern Oaks [Member] | Water Utility System [Member]
Business Acquisition [Line Items]
Number of customers | customer																		740
Total purchase price																		$ 3,300