Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 item	Jun. 30, 2012
Segment Information
Number of reporting segments			2
Segment contract revenues and operating income (loss)
Contract revenues	$ 213,916	$ 260,410	$ 415,258	$ 500,638
Operating income (loss)	15,362	15,657	26,752	25,885
T&D
Segment contract revenues and operating income (loss)
Contract revenues	174,041	215,816	334,573	420,814
Operating income (loss)	21,746	20,911	38,440	37,723
C&I
Segment contract revenues and operating income (loss)
Contract revenues	39,875	44,594	80,685	79,824
Operating income (loss)	1,429	1,860	4,155	2,959
General Corporate
Segment contract revenues and operating income (loss)
Operating income (loss)	$ (7,813)	$ (7,114)	$ (15,843)	$ (14,797)