Revenue Recognition (Schedule Of Disaggregation Of Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Revenue	$ 243,626	$ 226,137	$ 663,650	$ 632,344
Water [Member]
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	213,153	199,327	573,701	554,309
Revenue	213,088	198,632	573,918	553,494
Water [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	145,643	130,711	386,240	367,078
Water [Member] | Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	42,883	37,608	108,329	101,405
Water [Member] | Fire Protection [Member]
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	8,565	8,196	24,903	24,103
Water [Member] | Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	8,730	8,233	23,052	21,902
Water [Member] | Other Water [Member]
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	7,332	14,579	31,177	39,821
Water [Member] | Alternative Revenue Program [Member]
Disaggregation of Revenue [Line Items]
Revenue	(65)	(695)	217	(815)
Wastewater [Member]
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	26,622	24,544	77,983	69,196
Revenue	26,784	24,419	77,930	69,235
Wastewater [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	21,437	18,799	61,647	53,915
Wastewater [Member] | Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	4,037	3,610	11,400	9,473
Wastewater [Member] | Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	390	451	1,358	1,427
Wastewater [Member] | Other Wastewater [Member]
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	758	1,684	3,578	4,381
Wastewater [Member] | Alternative Revenue Program [Member]
Disaggregation of Revenue [Line Items]
Revenue	162	(125)	(53)	39
Other [Member]
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	2,984	2,310	9,234	6,963
Revenue	3,754	3,086	11,802	9,615
Other [Member] | Other And Eliminations [Member]
Disaggregation of Revenue [Line Items]
Revenue	770	776	2,568	2,652
Other [Member] | Other Utility [Member]
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 2,984	$ 2,310	$ 9,234	$ 6,963