Note 8 - Segment Reporting (Details) - Financial Information by Segment (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Segment Reporting Information [Line Items]
Revenues	$ 242,100	$ 254,490	$ 468,076	$ 482,368
Gross profit	58,568	62,219	106,705	114,790
Operating income (loss)	15,823	18,654	22,641	29,841
Energy And Mining [Member]
Segment Reporting Information [Line Items]
Revenues	108,592	127,900	217,283	240,224
Gross profit	26,294	32,969	50,560	59,757
Operating income (loss)	6,156	13,748	11,607	21,476
North American Water and Wastewater [Member]
Segment Reporting Information [Line Items]
Revenues	87,979	79,492	165,620	153,829
Gross profit	19,979	17,097	34,429	31,667
Operating income (loss)	8,958	5,883	12,683	10,073
International Water and Wastewater [Member]
Segment Reporting Information [Line Items]
Revenues	27,757	26,276	53,911	52,946
Gross profit	5,597	3,107	10,308	6,712
Operating income (loss)	82	(2,270)	(1,081)	(4,348)
Commercial And Structural [Member]
Segment Reporting Information [Line Items]
Revenues	17,772	20,822	31,262	35,369
Gross profit	6,698	9,046	11,408	16,654
Operating income (loss)	$ 627	$ 1,293	$ (568)	$ 2,640