Note 8 - Segment Reporting (Details) - Financial Information by Segment (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Revenues:
Revenues	$ 322,868	$ 242,100	$ 629,102	$ 468,076
Gross profit:
Gross profit	71,918	58,568	132,981	106,705
Operating income (loss):
Operating income (loss)	20,619	15,823	29,753	22,641
Energy And Mining [Member]
Revenues:
Revenues	175,608	108,592	359,518	217,283
Gross profit:
Gross profit	35,967	26,294	71,476	50,560
Operating income (loss):
Operating income (loss)	7,743	6,156	15,418	11,607
Water and Wastewater [Member]
Revenues:
Revenues	129,710	115,736	235,843	219,531
Gross profit:
Gross profit	29,257	25,576	49,359	44,737
Operating income (loss):
Operating income (loss)	12,654	9,040	15,674	11,602
Commercial And Structural [Member]
Revenues:
Revenues	17,550	17,772	33,741	31,262
Gross profit:
Gross profit	6,694	6,698	12,146	11,408
Operating income (loss):
Operating income (loss)	$ 222	$ 627	$ (1,339)	$ (568)