Summary of Significant Accounting Policies Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 172,497	$ 167,467	$ 307,330	$ 284,877
Total operating revenue	175,484	179,031	301,047	305,142
Total non-regulated revenue	4,208	5,130	8,035	10,031
Regulated Water and WasteWater Services
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	172,497	167,467	307,330	284,877
Regulatory balancing account revenue	2,987	11,564	(6,283)	20,265
Total operating revenue	175,484	179,031	301,047	305,142
Residential
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	116,453	107,349	208,998	191,609
Business
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	28,531	31,706	56,223	57,186
Industrial
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	6,622	7,524	14,500	14,788
Public authorities
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	7,711	7,613	13,608	12,084
Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	13,180	13,275	14,001	9,210
Operating and maintenance revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2,789	3,273	5,288	6,319
Other non-regulated revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	834	1,267	1,599	2,563
Non-Regulated Services
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	3,623	4,540	6,887	8,882
Lease Income	585	590	1,148	1,149
Total non-regulated revenue	$ 4,208	$ 5,130	$ 8,035	$ 10,031