Operating Segments - Geographic Information (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
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 216,462	$ 281,281	$ 674,923	$ 841,018
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	174,573	210,460	522,161	654,034
Africa / Australia [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	8,035	19,314	33,904	74,416
South America [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	15,690	21,976	43,852	36,036
Mexico [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	13,070	18,443	48,696	56,381
Other foreign [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 5,094	$ 11,088	$ 26,310	$ 20,151