Investment in joint venture (Details) (USD $)	3 Months Ended		9 Months Ended
	Oct. 31, 2013	Oct. 31, 2012	Oct. 31, 2013	Oct. 31, 2012	Jan. 31, 2013
Investment in joint venture [Line Items]
date of investment in joint venture			Oct. 18, 2009
initial investment in joint venture			$ 5,900,000
Payment to acquire interest in joint venture			2,000,000
Joint venture ownership percentage	49.00%		49.00%
Advance to joint venture			3,900,000
Loan to joint venture	1,000,000		1,000,000
Income from joint venture	715,000	531,000	248,000	354,000
Current assets	12,312,000		12,312,000		14,058,000
Noncurrent assets	18,613,000		18,613,000		19,442,000
Current liabilities	2,306,000		2,306,000		2,703,000
Noncurrent liabilities	15,989,000		15,989,000		18,274,000
Equity	12,630,000		12,630,000		12,524,000
Revenue			19,913,000	19,389,000
Gross profit			3,157,000	3,616,000
Income from continuing operations			1,570,000	1,827,000
Net income			$ 516,000	$ 726,000