Operations by Business Segment (Details) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2023 USD ($)	Oct. 01, 2022 USD ($)	Sep. 30, 2023 USD ($)	Oct. 01, 2022 USD ($)	Dec. 31, 2022 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments				2
Revenues		$ 450,634	$ 398,945	$ 1,267,174	$ 1,143,548
Income (loss) from operations		36,237	33,013	97,195	79,502
Interest expense		(4,751)	(2,164)	(13,588)	(5,312)
Interest income		502	303	1,329	489
Other income (expense), net		(2,890)	(3,371)	(4,365)	(8,241)
Income before income taxes		29,098	27,781	80,571	66,438
Segment assets, total		1,266,553	899,971	1,266,553	899,971	$ 956,221
Utility
Segment Reporting Information [Line Items]
Revenues		247,478	217,305	700,378	637,900
Income (loss) from operations		17,656	16,790	51,197	49,260
Segment assets, total		372,114	331,393	372,114	331,393
Residential and commercial
Segment Reporting Information [Line Items]
Revenues		201,753	180,706	563,942	504,064
Income (loss) from operations		24,398	21,204	61,312	50,759
Segment assets, total		368,062	305,216	368,062	305,216
All other
Segment Reporting Information [Line Items]
Revenues		1,403	934	2,854	1,584
Income (loss) from operations		(4,188)	(4,033)	(11,439)	(14,852)
Segment assets, total		0	0	0	0
Reconciling Adjustments
Segment Reporting Information [Line Items]
Revenues		0	0	0	0
Income (loss) from operations	[1]	(1,629)	(948)	(3,875)	(5,665)
Interest expense		(4,751)	(2,164)	(13,588)	(5,312)
Interest income		502	303	1,329	489
Other income (expense), net		(2,890)	(3,371)	(4,365)	(8,241)
Segment assets, total	[2]	$ 526,377	$ 263,362	$ 526,377	$ 263,362

[1] Reclassification of depreciation expense and allocation of corporate expenses

[2] Corporate assets include cash, prepaid expenses, corporate facilities, enterprise-wide information systems and other nonoperating assets.