Note 12 - Segment and Geographic Information (Detail) - Financial Information by Segment (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Revenues:
Revenues	$ 256,795	$ 246,218	$ 224,985	$ 210,587	$ 246,016	$ 239,585	$ 230,192	$ 199,182	$ 938,585	$ 914,975	$ 726,866
Operating income (loss):
Operating income (loss)	21,710	9,498	7,840	5,489	24,827	26,955	22,747	12,506	44,537	87,035	49,117
Total assets:
Assets	1,124,964				933,310				1,124,964	933,310	866,583
Capital expenditures:
Capital expenditures									21,554	36,858	21,837
Depreciation and amortization:
Depreciation and amortization									36,039	30,732	28,440
Energy and Mining [Member]
Revenues:
Revenues									433,230	382,246	241,678
Operating income (loss):
Operating income (loss)									35,011	41,121	10,924
Total assets:
Assets	479,194				390,592				479,194	390,592	334,925
Capital expenditures:
Capital expenditures									11,375	14,603	3,890
Depreciation and amortization:
Depreciation and amortization									16,613	14,504	12,129
North American Sewer and Water Rehabilitation [Member]
Revenues:
Revenues									357,507	413,828	365,889
Operating income (loss):
Operating income (loss)									6,749	40,831	36,050
Total assets:
Assets	281,353				310,839				281,353	310,839	302,806
Capital expenditures:
Capital expenditures									3,378	13,256	8,988
Depreciation and amortization:
Depreciation and amortization									9,405	9,796	10,106
European Sewer and Water Rehabilitation [Member]
Revenues:
Revenues									87,017	74,260	86,043
Operating income (loss):
Operating income (loss)									6,000	5,013	(1,276)
Total assets:
Assets	62,791				60,861				62,791	60,861	76,235
Capital expenditures:
Capital expenditures									1,798	1,768	1,858
Depreciation and amortization:
Depreciation and amortization									2,007	2,047	2,347
Asia-Pacific Sewer and Water Rehabilitation [Member]
Revenues:
Revenues									43,717	44,641	33,256
Operating income (loss):
Operating income (loss)									(2,512)	70	3,419
Total assets:
Assets	76,932				63,100				76,932	63,100	51,873
Capital expenditures:
Capital expenditures									1,908	5,094	5,567
Depreciation and amortization:
Depreciation and amortization									2,728	2,060	1,313
Commercial and Structural [Member]
Revenues:
Revenues									17,114
Operating income (loss):
Operating income (loss)									(711)
Total assets:
Assets	128,358								128,358
Capital expenditures:
Capital expenditures									43
Depreciation and amortization:
Depreciation and amortization									1,183
Corporate [Member]
Total assets:
Assets	96,336				104,118				96,336	104,118	96,251
Capital expenditures:
Capital expenditures									3,052	2,137	1,534
Depreciation and amortization:
Depreciation and amortization									4,103	2,325	2,545
Discontinued Operations [Member]
Total assets:
Assets					$ 3,800					$ 3,800	$ 4,493