Summary of Significant Accounting Policies - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 253,337	$ 238,268	$ 592,768	$ 595,860
Regulatory balancing account revenue	1,639	28,039	(12,648)	49,634
Operating revenue	254,976	266,307	580,120	645,494
Total non-regulated revenue	4,535	4,573	13,643	16,772
Residential
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	150,031	140,585	342,806	348,965
Business
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	47,707	44,031	117,527	115,472
Multiple residential
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	18,778	17,333	50,280	48,343
Industrial
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	8,165	8,086	19,672	20,174
Public authorities
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	14,522	13,441	29,938	31,310
Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	14,134	14,792	32,545	31,596
Operating and maintenance revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2,918	3,184	9,229	9,822
Other non-regulated revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	972	720	2,553	4,951
Non-regulated revenue from contracts with customers
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	3,890	3,904	11,782	14,773
Lease revenue	645	669	1,861	1,999
Total non-regulated revenue	$ 4,535	$ 4,573	$ 13,643	16,772
Insurance Program
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers				$ 2,700