Significant accounting policies Investment in joint venture (Details) (USD $)	12 Months Ended
	Jan. 31, 2014	Jan. 31, 2013
Schedule of Equity Method Investments [Line Items]
date of investment in joint venture		Oct. 18, 2009
Equity Method Investment, Aggregate Cost	$ 5,900,000
Payments to acquire interest in joint venture	2,000,000
Ownership percentage of joint venture	49.00%
Advances to joint venture	3,900,000
loan to joint venture	(1,000,000)
Payments to fund long-term loans to joint venture	0	989,000
Income from joint venture	528,000	1,386,000
Equity Method Investment, Summarized Financial Information, Current Assets	13,034,000	14,058,000
Equity Method Investment, Summarized Financial Information, Noncurrent Assets	17,093,000	19,442,000
Equity Method Investment, Summarized Financial Information, Current Liabilities	2,921,000	2,703,000
Equity Method Investment, Summarized Financial Information, Noncurrent Liabilities	14,837,000	18,274,000
Equity Method Investment, Summarized Financial Information, Equity or Capital	12,369,000	12,523,000
Equity Method Investment, Summarized Financial Information, Revenue	29,110,000	30,448,000
Equity Method Investment, Summarized Financial Information, Gross Profit (Loss)	4,748,000	7,211,000
Equity Method Investment, Summarized Financial Information, Income (Loss) from Continuing Operations before Extraordinary Items	2,619,000	3,380,000
Equity Method Investment, Summarized Financial Information, Net Income (Loss)	$ 1,078,000	$ 2,680,000