Supplemental Statements of Cash Flows Information (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2011
Supplemental disclosures of cash flows information
Interest paid	$ 533	$ 704	$ 728
Income taxes paid, net	9,177	7,536	508
Seismic equipment purchases included in accounts payable at year-end	4,268	9,900	3,229
Stock issued for accrued compensation	$ 516	$ 303	$ 185