Segment Information (Details 2) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Identifiable assets, consisting of contract receivables, costs and estimated earnings in excess of billings on uncompleted contracts, construction materials inventory, goodwill and intangibles for each segment
Assets	$ 466,348	$ 412,568
T&D
Identifiable assets, consisting of contract receivables, costs and estimated earnings in excess of billings on uncompleted contracts, construction materials inventory, goodwill and intangibles for each segment
Assets	223,719	182,016
C&I
Identifiable assets, consisting of contract receivables, costs and estimated earnings in excess of billings on uncompleted contracts, construction materials inventory, goodwill and intangibles for each segment
Assets	63,554	49,492
Other
Identifiable assets, consisting of contract receivables, costs and estimated earnings in excess of billings on uncompleted contracts, construction materials inventory, goodwill and intangibles for each segment
Assets	$ 179,075	$ 181,060