Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Segment Reporting Information [Line Items]
Contract revenues:	$ 253,634	$ 244,148
Income from operations:	3,307	11,597
T&D [Member]
Segment Reporting Information [Line Items]
Contract revenues:	182,974	189,223
Income from operations:	10,669	16,834
C&I [Member]
Segment Reporting Information [Line Items]
Contract revenues:	70,660	54,925
Income from operations:	2,156	2,836
General Corporate [Member]
Segment Reporting Information [Line Items]
Income from operations:	$ (9,518)	$ (8,073)