Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013 item	Mar. 31, 2012
Segment Information
Number of reporting segments	2
Segment contract revenues and operating income (loss)
Contract revenues	$ 201,342	$ 240,228
Operating income (loss)	11,390	10,228
T&D
Segment contract revenues and operating income (loss)
Contract revenues	160,532	204,998
Operating income (loss)	16,694	16,812
C&I
Segment contract revenues and operating income (loss)
Contract revenues	40,810	35,230
Operating income (loss)	2,726	1,099
General Corporate
Segment contract revenues and operating income (loss)
Operating income (loss)	$ (8,030)	$ (7,683)