Operating Segments - Additional Financial Information for Segments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Oct. 31, 2013	Oct. 31, 2012	Oct. 31, 2013	Oct. 31, 2012
Segment Reporting Information [Line Items]
Revenues	$ 216,462	$ 281,281	$ 674,923	$ 841,018
Water systems [Member]
Segment Reporting Information [Line Items]
Revenues	47,783	57,482	141,708	165,373
Water treatment technologies [Member]
Segment Reporting Information [Line Items]
Revenues	8,580	13,349	29,157	36,205
Sewer rehabilitation [Member]
Segment Reporting Information [Line Items]
Revenues	43,806	32,115	111,971	101,682
Water and wastewater plant construction [Member]
Segment Reporting Information [Line Items]
Revenues	38,104	32,260	121,482	97,098
Pipeline construction [Member]
Segment Reporting Information [Line Items]
Revenues	17,529	25,636	64,029	91,902
Soil stabilization [Member]
Segment Reporting Information [Line Items]
Revenues	22,032	54,240	70,670	130,548
Environmental and specialty drilling [Member]
Segment Reporting Information [Line Items]
Revenues	1,979	1,557	4,613	6,369
Exploration drilling [Member]
Segment Reporting Information [Line Items]
Revenues	35,040	62,924	126,955	206,615
Other product [Member]
Segment Reporting Information [Line Items]
Revenues	$ 1,609	$ 1,718	$ 4,338	$ 5,226