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Warranty (Details) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
Jul. 31, 2018
Jul. 31, 2017
Jul. 31, 2018
Jul. 31, 2017
Warranty claim activity        
Beginning balance $ 925 $ 1,000 $ 925 $ 1,000
Provision 86 112 141 182
Costs incurred (86) (112) (141) (182)
Ending balance $ 925 $ 1,000 $ 925 $ 1,000
Maximum [Member]        
Warranty [Line Items]        
Product warranty period     10 years