Operations by Business Segment (Details) $ in Thousands		3 Months Ended
		Mar. 30, 2019 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments		2
Revenues		$ 247,889	$ 208,651
Income (loss) from operations		2,966	(5,666)
Interest expense		(2,151)	(1,401)
Interest income		83	78
Other income (expense), net		(1,655)	(1,662)
Loss before income taxes		(757)	(8,651)
Segment assets, total		565,478	474,200	$ 526,623
Utility [Member]
Segment Reporting Information [Line Items]
Revenues		140,469	118,687
Income (loss) from operations		5,880	1,814
Segment assets, total		231,060	200,201
Residential commercial [Member]
Segment Reporting Information [Line Items]
Revenues		107,395	89,345
Income (loss) from operations		507	(3,105)
Segment assets, total		217,044	188,789
All other [Member]
Segment Reporting Information [Line Items]
Revenues		25	619
Income (loss) from operations		(2,968)	(3,792)
Segment assets, total		0	0
Reconciling adjustments [Member]
Segment Reporting Information [Line Items]
Revenues		0	0
Income (loss) from operations	[1]	(453)	(583)
Interest expense		(2,151)	(1,401)
Interest income		83	78
Other income (expense), net		(1,655)	(1,662)
Segment assets, total	[2]	$ 117,374	$ 85,210

[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.