Significant accounting policies Inventories (Details) (USD $) In Thousands, unless otherwise specified	Jan. 31, 2015	Jan. 31, 2014
Inventories [Abstract]
Raw materials	$ 22,887us-gaap_InventoryRawMaterials	$ 27,330us-gaap_InventoryRawMaterials
Work in process	1,254us-gaap_InventoryWorkInProcess	2,855us-gaap_InventoryWorkInProcess
Finished goods	6,550us-gaap_InventoryFinishedGoods	4,311us-gaap_InventoryFinishedGoods
Subtotal	30,691us-gaap_InventoryGross	34,496us-gaap_InventoryGross
Less allowances	921	949
Inventories, net	$ 29,770us-gaap_InventoryNet	$ 33,547us-gaap_InventoryNet

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Amount before valuation and LIFO reserves of completed merchandise or goods expected to be sold within one year or operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 6

-Subparagraph a

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-Publisher FASB

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-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.6(a)(1))

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Gross amount, as of the balance sheet date, of merchandise, goods, commodities, or supplies held for future sale or to be used in manufacturing, servicing or production process.

+ References

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Amount after valuation and LIFO reserves of inventory expected to be sold, or consumed within one year or operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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-Name Accounting Standards Codification

-Topic 330

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Amount before valuation and LIFO reserves of raw materials expected to be sold, or consumed within one year or operating cycle, if longer.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

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-Topic 210

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-Subparagraph (SX 210.5-02.6(a)(4))

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Amount before valuation and LIFO reserves of merchandise or goods in the production process expected to be completed within one year or operating cycle, if longer.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

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Total of allowances and reserves, the valuation and qualifying accounts that are either netted against the cost of an asset (in order to value it at its carrying value) or that reflect a liability established to represent expected future costs.

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