Note 8 - Segment Reporting (Details) - Financial Information by Segment (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Revenues:
Revenues	$ 307,665	$ 262,867	$ 775,741	$ 745,236
Gross profit:
Gross profit	69,411	62,931	176,116	177,722
Operating income (loss):
Operating income (loss)	22,032	26,865	44,673	56,706
Energy And Mining [Member]
Revenues:
Revenues	168,708	137,386	385,991	377,610
Gross profit:
Gross profit	37,118	33,710	87,678	93,466
Operating income (loss):
Operating income (loss)	12,874	21,426	24,481	42,902
North American Water And Wastewater [Member]
Revenues:
Revenues	95,997	77,818	261,616	231,647
Gross profit:
Gross profit	21,357	17,183	55,786	48,850
Operating income (loss):
Operating income (loss)	10,328	6,289	23,010	16,361
International Water And Wastewater [Member]
Revenues:
Revenues	26,152	27,766	80,064	80,712
Gross profit:
Gross profit	5,116	2,890	15,424	9,603
Operating income (loss):
Operating income (loss)	(257)	(3,195)	(1,338)	(7,542)
Commercial And Structural [Member]
Revenues:
Revenues	16,808	19,897	48,070	55,267
Gross profit:
Gross profit	5,820	9,148	17,228	25,803
Operating income (loss):
Operating income (loss)	$ (913)	$ 2,345	$ (1,480)	$ 4,985