Summary Of Significant Accounting Policies (Schedule Of Disaggregation Of Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Revenue	$ 226,042	$ 243,626	$ 218,892	$ 201,132	$ 205,747	$ 226,137	$ 211,860	$ 194,347	$ 889,692	$ 838,091	$ 809,525
Water [Member]
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									767,400	731,441
Revenue									767,480	730,733
Wastewater [Member]
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									105,204	94,170
Revenue									105,115	94,478
Other [Member]
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									13,835	9,427
Revenue									17,097	12,880
Other [Member] | Other And Eliminations [Member]
Disaggregation of Revenue [Line Items]
Revenue									3,262	3,453
Residential [Member] | Water [Member]
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									518,192	482,946
Residential [Member] | Wastewater [Member]
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									83,561	73,418
Commercial [Member] | Water [Member]
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									145,599	133,753
Commercial [Member] | Wastewater [Member]
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									15,222	13,147
Fire Protection [Member] | Water [Member]
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									33,589	32,236
Industrial [Member] | Water [Member]
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									30,667	28,848
Industrial [Member] | Wastewater [Member]
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									1,765	1,857
Other Water [Member] | Water [Member]
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									39,353	53,658
Other Wastewater [Member] | Wastewater [Member]
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									4,656	5,748
Alternative Revenue Program [Member] | Water [Member]
Disaggregation of Revenue [Line Items]
Revenue									80	(708)
Alternative Revenue Program [Member] | Wastewater [Member]
Disaggregation of Revenue [Line Items]
Revenue									(89)	308
Other Utility [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers									$ 13,835	$ 9,427