Note 12 - Segment and Geographic Information (Details) - Financial Information by Segment (USD $) In Thousands, unless otherwise specified	3 Months Ended													12 Months Ended
	Dec. 31, 2013		Sep. 30, 2013		Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012		Sep. 30, 2012		Jun. 30, 2012		Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenues:
Revenues	$ 315,679	[1]	$ 307,665	[1]	$ 242,100	$ 225,976	$ 271,595	[2]	$ 262,867	[2]	$ 254,490	[2]	$ 227,879	$ 1,091,420	$ 1,016,831	$ 925,766
Operating income (loss):														40,329	37,658	35,532
Operating income (loss)	22,209	[1]	22,032	[1]	15,823	6,818	25,097	[2]	26,865	[2]	18,654	[2]	11,187	66,882	81,803	45,707
Assets
Assets	1,362,918						1,217,894							1,362,918	1,217,894	1,124,964
Capital expenditures:
Payments to Acquire Property, Plant, and Equipment														26,085	44,738	21,271
Energy And Mining [Member]
Revenues:
Revenues														562,119	513,975	420,411
Operating income (loss):														21,954	18,175	16,106
Operating income (loss)														38,395	59,994	36,181
Assets
Assets	723,468						569,109							723,468	569,109	465,792
Capital expenditures:
Payments to Acquire Property, Plant, and Equipment														15,367	34,796	11,092
North American Water And Wastewater [Member]
Revenues:
Revenues														359,536	317,338	357,507
Operating income (loss):														8,398	8,886	9,405
Operating income (loss)														33,029	22,057	6,749
Assets
Assets	263,173						268,097							263,173	268,097	281,353
Capital expenditures:
Payments to Acquire Property, Plant, and Equipment														4,858	3,023	3,378
International Water And Wastewater [Member]
Revenues:
Revenues														109,602	111,035	130,734
Operating income (loss):														4,304	4,405	4,735
Operating income (loss)														208	(9,384)	3,488
Assets
Assets	112,546						120,466							112,546	120,466	139,723
Capital expenditures:
Payments to Acquire Property, Plant, and Equipment														3,500	4,382	3,706
Commercial And Structural [Member]
Revenues:
Revenues														60,163	74,483	17,114
Operating income (loss):														3,850	4,509	1,183
Operating income (loss)														(4,750)	9,136	(711)
Assets
Assets	139,058						142,561							139,058	142,561	128,358
Capital expenditures:
Payments to Acquire Property, Plant, and Equipment														470	443	43
Corporate and Other [Member]
Revenues:
Operating income (loss):														1,823	1,683	4,103
Assets
Assets	116,317						101,851							116,317	101,851	96,336
Capital expenditures:
Payments to Acquire Property, Plant, and Equipment														1,890	2,094	3,052
Discontinued Operations [Member]
Assets
Assets	$ 8,356						$ 15,810							$ 8,356	$ 15,810	$ 13,402

[1] (1) Includes the financial results of Brinderson, which was acquired in July 2013.

[2] (2) Includes the financial results of Fyfe Asia, which was acquired in April 2012.