Note 11 - Segment and Geographic Information (Detail) - Financial Information by Segment (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Revenues:
Revenues	$ 274,683	$ 265,155	$ 257,531	$ 230,594	$ 256,795	$ 246,218	$ 224,985	$ 210,587	$ 1,027,963	$ 938,585	$ 914,975
Operating income (loss):
Operating income (loss)	23,718	26,142	18,363	10,899	21,710	9,498	7,840	5,489	79,122	44,537	87,035
Total assets:
Assets	1,217,894				1,124,964				1,217,894	1,124,964	933,310
Capital expenditures:
Capital expenditures									45,894	21,554	36,858
Depreciation and amortization:
Depreciation and amortization									38,117	36,039	30,732
Energy and Mining [Member]
Revenues:
Revenues									525,107	433,230	382,246
Operating income (loss):
Operating income (loss)									57,313	35,011	41,121
Total assets:
Assets	584,919				479,194				584,919	479,194	390,592
Capital expenditures:
Capital expenditures									35,952	11,375	14,603
Depreciation and amortization:
Depreciation and amortization									18,634	16,613	14,504
North American Sewer and Water Rehabilitation [Member]
Revenues:
Revenues									317,338	357,507	413,828
Operating income (loss):
Operating income (loss)									22,057	6,749	40,831
Total assets:
Assets	268,097				281,353				268,097	281,353	310,839
Capital expenditures:
Capital expenditures									3,023	3,378	13,256
Depreciation and amortization:
Depreciation and amortization									8,886	9,405	9,796
European Sewer and Water Rehabilitation [Member]
Revenues:
Revenues									72,534	87,017	74,260
Operating income (loss):
Operating income (loss)									2,117	6,000	5,013
Total assets:
Assets	65,637				62,791				65,637	62,791	60,861
Capital expenditures:
Capital expenditures									2,737	1,798	1,768
Depreciation and amortization:
Depreciation and amortization									1,808	2,007	2,047
Asia-Pacific Sewer and Water Rehabilitation [Member]
Revenues:
Revenues									38,501	43,717	44,641
Operating income (loss):
Operating income (loss)									(11,501)	(2,512)	70
Total assets:
Assets	54,829				76,932				54,829	76,932	63,100
Capital expenditures:
Capital expenditures									1,645	1,908	5,094
Depreciation and amortization:
Depreciation and amortization									2,597	2,728	2,060
Commercial and Structural [Member]
Revenues:
Revenues									74,483	17,114
Operating income (loss):
Operating income (loss)									9,136	(711)
Total assets:
Assets	142,561				128,358				142,561	128,358
Capital expenditures:
Capital expenditures									443	43
Depreciation and amortization:
Depreciation and amortization									4,509	1,183
Corporate [Member]
Total assets:
Assets	101,851				96,336				101,851	96,336	104,118
Capital expenditures:
Capital expenditures									2,094	3,052	2,137
Depreciation and amortization:
Depreciation and amortization									1,683	4,103	2,325
Discontinued Operations [Member]
Total assets:
Assets											$ 3,800