Significant accounting policies Investment in joint venture (Details) (USD $)	12 Months Ended
	Jan. 31, 2013	Jan. 31, 2012
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Summarized Financial Information, Current Assets	$ 14,058,000	$ 14,381,000
Equity Method Investment, Summarized Financial Information, Noncurrent Assets	19,442,000	14,259,000
date of investment in joint venture	Oct. 18, 2009
Income (Loss) from Equity Method Investments	1,386,000	1,558,000
Equity Method Investment, Aggregate Cost	5,900,000
Payments to Acquire Interest in Joint Venture	2,000,000
Equity Method Investment, Ownership Percentage	49.00%
Advances to Affiliate	3,900,000
Payments to Fund Long-term Loans to Related Parties	989,000	0
Equity Method Investment, Summarized Financial Information, Current Liabilities	2,703,000	3,449,000
Equity Method Investment, Summarized Financial Information, Noncurrent Liabilities	18,274,000	15,403,000
Equity Method Investment, Summarized Financial Information, Equity or Capital	12,524,000	9,789,000
Equity Method Investment, Summarized Financial Information, Revenue	30,448,000	29,010,000
Equity Method Investment, Summarized Financial Information, Gross Profit (Loss)	7,211,000	7,565,000
Equity Method Investment, Summarized Financial Information, Income (Loss) from Continuing Operations before Extraordinary Items	3,380,000	5,137,000
Equity Method Investment, Summarized Financial Information, Net Income (Loss)	2,680,000	3,189,000
loan to joint venture	$ (1,000,000)