Income taxes Deferred income tax disclosure (Details) - USD ($) $ in Thousands	Jan. 31, 2018	Jan. 31, 2017
Components of deferred income tax assets
U.S. Federal NOL carryforward	$ 1,795	$ 7,765
Deferred compensation	341	346
Research tax credit	2,703	2,703
Foreign NOL carryforward	332	185
Foreign tax credit	9,749	4,695
Stock compensation	506	804
Other accruals not yet deducted	270	514
State NOL carryforward	2,157	1,574
Accrued commissions and incentives	423	765
Inventory valuation allowance	96	110
Other	81	5
Deferred tax assets, gross	18,453	19,466
Valuation allowance	(17,198)	(16,551)
Total deferred tax assets, net of valuation allowances	1,255	2,915
Components of the deferred income tax liability
Depreciation	(1,941)	(2,778)
Foreign subsidiaries unremitted earnings	(101)	(1,750)
Prepaid	(64)	(69)
Total deferred tax liabilities	(2,106)	(4,597)
Deferred tax liabilities, net	(851)	(1,682)
Balance sheet classification
Deferred tax long-term assets	391	147
Deferred tax long-term liabilities	$ (1,242)	$ (1,829)