Regulatory Assets And Liabilities (Narrative) (Details) - USD ($) $ in Thousands		1 Months Ended	12 Months Ended
	May 18, 2019	May 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Regulatory Assets And Liabilities [Line Items]
Amortization of deferred repair tax adjustment			$ 38,000
Amortization period			10 years
Increase in net income			$ 16,274	$ 16,734	$ 16,734
Statutory federal tax rate			21.00%	35.00%	35.00%
Redemption of debt		$ 313,500	$ 1,048,471	$ 914,125	$ 359,068
Make whole payment	$ 25,237	$ 25,237	$ 25,237
Scenario, Plan [Member]
Regulatory Assets And Liabilities [Line Items]
Statutory federal tax rate			21.00%
Minimum [Member]
Regulatory Assets And Liabilities [Line Items]
Water tank painting costs amortization period			7 years
Maturity date			2022
Rate case filing expense amortization period			1 year
Maturity		2019
Redemption percentage	3.57%	3.57%
Maximum [Member]
Regulatory Assets And Liabilities [Line Items]
Water tank painting costs amortization period			10 years
Maturity date			2029
Rate case filing expense amortization period			5 years
Maturity		2037
Redemption percentage	5.83%	5.83%
Postretirement Benefits [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory asset recovery period			10 years