Operations by Business Segment (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 29, 2012		Oct. 01, 2011		Sep. 29, 2012		Oct. 01, 2011		Dec. 31, 2011
Segment Reporting Information [Line Items]
Revenues	$ 178,647		$ 178,799		$ 507,702		$ 484,076
Income (loss) from operations	14,652		13,342		32,430		21,689
Interest expense	(661)		(1,041)		(2,071)		(2,915)
Interest income	65		14		121		28
Other income (expense), net	(638)		(1,043)		(2,147)		(2,367)
Income before income taxes	13,418		11,272		28,333		16,435
Segment assets, total	328,914		315,183		328,914		315,183		303,734
Utility services [Member]
Segment Reporting Information [Line Items]
Revenues	80,874		86,038		240,359		239,842
Income (loss) from operations	2,343		3,336		7,398		4,672
Segment assets, total	125,178		128,214		125,178		128,214
Residential commercial services [Member]
Segment Reporting Information [Line Items]
Revenues	81,438		76,522		219,864		202,871
Income (loss) from operations	10,925		9,400		23,058		17,370
Segment assets, total	114,940		107,285		114,940		107,285
All other [Member]
Segment Reporting Information [Line Items]
Revenues	16,335		16,239		47,479		41,363
Income (loss) from operations	1,633		2,117		3,235		2,213
Segment assets, total	21,528		17,744		21,528		17,744
Reconciling adjustments [Member]
Segment Reporting Information [Line Items]
Revenues	0		0		0		0
Income (loss) from operations	(249)	[1]	(1,511)	[1]	(1,261)	[1]	(2,566)	[1]
Interest expense	(661)		(1,041)		(2,071)		(2,915)
Interest income	65		14		121		28
Other income (expense), net	(638)		(1,043)		(2,147)		(2,367)
Segment assets, total	$ 67,268	[2]	$ 61,940	[2]	$ 67,268	[2]	$ 61,940	[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.