Operations by Business Segment (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2012		Jul. 02, 2011		Jun. 30, 2012		Jul. 02, 2011		Dec. 31, 2011
Segment Reporting Information [Line Items]
Revenues	$ 182,411		$ 173,953		$ 329,055		$ 305,277
Income (loss) from operations	17,270		16,567		17,778		8,347
Interest expense	(707)		(984)		(1,410)		(1,874)
Interest income	29		9		56		14
Other income (expense), net	(874)		(661)		(1,509)		(1,324)
Income before income taxes	15,718		14,931		14,915		5,163
Segment assets, total	312,652		309,107		312,652		309,107		303,734
Utility services [Member]
Segment Reporting Information [Line Items]
Revenues	78,989		79,153		159,485		153,804
Income (loss) from operations	1,928		2,006		5,055		1,336
Segment assets, total	124,964		126,441		124,964		126,441
Residential commercial services [Member]
Segment Reporting Information [Line Items]
Revenues	87,294		80,690		138,426		126,349
Income (loss) from operations	14,867		13,810		12,133		7,970
Segment assets, total	114,934		112,383		114,934		112,383
All other [Member]
Segment Reporting Information [Line Items]
Revenues	16,128		14,110		31,144		25,124
Income (loss) from operations	1,754		1,332		1,602		96
Segment assets, total	18,807		17,722		18,807		17,722
Reconciling adjustments [Member]
Segment Reporting Information [Line Items]
Revenues	0		0		0		0
Income (loss) from operations	(1,279)	[1]	(581)	[1]	(1,012)	[1]	(1,055)	[1]
Interest expense	(707)		(984)		(1,410)		(1,874)
Interest income	29		9		56		14
Other income (expense), net	(874)		(661)		(1,509)		(1,324)
Segment assets, total	$ 53,947	[2]	$ 52,561	[2]	$ 53,947	[2]	$ 52,561	[2]

[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.