Operations by Business Segment (Details) $ in Thousands		3 Months Ended
		Mar. 31, 2018 USD ($)	Apr. 01, 2017 USD ($)	Dec. 31, 2017 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments		2
Revenues		$ 208,651	$ 192,813
Income (loss) from operations		(5,666)	(3,995)
Interest expense		(1,401)	(1,257)
Interest income		78	70
Other income (expense), net		(1,662)	(1,139)
Loss before income taxes		(8,651)	(6,321)
Segment assets, total		474,200	448,089	$ 473,135
Utility [Member]
Segment Reporting Information [Line Items]
Revenues		118,687	112,478
Income (loss) from operations		1,814	2,658
Segment assets, total		200,201	176,504
Residential commercial [Member]
Segment Reporting Information [Line Items]
Revenues		89,345	79,587
Income (loss) from operations		(3,105)	(3,582)
Segment assets, total		188,789	171,777
All other [Member]
Segment Reporting Information [Line Items]
Revenues		619	748
Income (loss) from operations		(3,792)	(2,228)
Segment assets, total		0	0
Reconciling adjustments [Member]
Segment Reporting Information [Line Items]
Revenues		0	0
Income (loss) from operations	[1]	(583)	(843)
Interest expense		(1,401)	(1,257)
Interest income		78	70
Other income (expense), net		(1,662)	(1,139)
Segment assets, total	[2]	$ 85,210	$ 99,808

[1] (a)Reclassification of depreciation expense and allocation of corporate expenses

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