Segment Reporting (Detail) - Schedule of Segment Reporting Information, Profit Loss and Revenue Percentage (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Apr. 30, 2013	Apr. 30, 2012
Net sales and revenues	$ 178,747	$ 151,006
Gross profit	9,097	5,525
Income from continuing operations before income taxes	5,937	1,872
Interest expense	(1,059)	(1,276)
Interest income	25	36
Ethanol [Member] | Alternative Energy Segment [Member]
Sale of Product	74.00%	78.00%
Dried Distillers Grains [Member] | Alternative Energy Segment [Member]
Sale of Product	17.00%	17.00%
Modified Distillers Grains [Member] | Alternative Energy Segment [Member]
Sale of Product	6.00%	3.00%
Other Products [Member] | Alternative Energy Segment [Member]
Sale of Product	3.00%	2.00%
Alternative Energy Segment [Member]
Net sales and revenues	178,324	150,664
Gross profit	9,026	5,510
Income from continuing operations before income taxes	6,626	2,469
Sale of Product	100.00%	100.00%
Real Estate Segment [Member]
Net sales and revenues	423	342
Gross profit	71	15
Income from continuing operations before income taxes	8	(60)
Lease revenue	100.00%	100.00%
Corporate Segment [Member]
Income from continuing operations before income taxes	(701)	(548)
Interest expense	(14)	(18)
Interest income	$ 18	$ 29