Revenue Recognition (Narrative) (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2020 item
Schedule of Equity Method Investments [Line Items]
Categories | item			4
Aqua Infrastructure [Member]
Schedule of Equity Method Investments [Line Items]
Ownership percentage		49.00%	49.00%
Scenario, Forecast [Member] | Peoples Gas Acquisition [Member] | Customer Rate Credits [Member]
Schedule of Equity Method Investments [Line Items]
Revenues from contracts with customers	$ 23,000
Water And Wastewater Utility Systems [Member] | Customer Rate Credits [Member]
Schedule of Equity Method Investments [Line Items]
Revenues from contracts with customers		$ 4,080
Water And Wastewater Utility Systems [Member] | Peoples Gas Acquisition [Member] | Customer Rate Credits [Member]
Schedule of Equity Method Investments [Line Items]
Revenues from contracts with customers		$ 4,080
Natural Gas Utility [Member] | Scenario, Forecast [Member] | Customer Rate Credits [Member]
Schedule of Equity Method Investments [Line Items]
Revenues from contracts with customers	$ 18,920