Operating Segments - Summary of Revenue for Continuing Operations by Product Line and Major Geographic Area (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 31, 2016	Jul. 31, 2015	Jul. 31, 2016	Jul. 31, 2015
Entity Wide Information Revenue From External Customer [Line Items]
Revenues	$ 159,049	$ 176,317	$ 318,788	$ 350,588
Water systems [Member]
Entity Wide Information Revenue From External Customer [Line Items]
Revenues	49,394	54,896	104,872	107,405
Water treatment technologies [Member]
Entity Wide Information Revenue From External Customer [Line Items]
Revenues	3,152	2,417	7,421	6,127
Sewer rehabilitation [Member]
Entity Wide Information Revenue From External Customer [Line Items]
Revenues	52,976	41,790	100,510	89,810
Water and wastewater plant construction [Member]
Entity Wide Information Revenue From External Customer [Line Items]
Revenues	21,132	39,434	42,440	73,157
Pipeline construction [Member]
Entity Wide Information Revenue From External Customer [Line Items]
Revenues	13,569	8,785	30,542	18,975
Environmental and specialty drilling [Member]
Entity Wide Information Revenue From External Customer [Line Items]
Revenues	3,393	2,215	6,276	3,598
Exploration drilling [Member]
Entity Wide Information Revenue From External Customer [Line Items]
Revenues	13,618	24,424	23,912	45,488
Other [Member]
Entity Wide Information Revenue From External Customer [Line Items]
Revenues	1,815	2,356	2,815	6,028
United States [Member]
Entity Wide Information Revenue From External Customer [Line Items]
Revenues	152,228	160,905	306,268	321,951
Africa / Australia [Member]
Entity Wide Information Revenue From External Customer [Line Items]
Revenues		3,872	152	7,962
South America [Member]
Entity Wide Information Revenue From External Customer [Line Items]
Revenues	1,838	2,073	2,301	3,983
Mexico [Member]
Entity Wide Information Revenue From External Customer [Line Items]
Revenues	4,966	8,806	9,966	15,467
Other foreign [Member]
Entity Wide Information Revenue From External Customer [Line Items]
Revenues	$ 17	$ 661	$ 101	$ 1,225