Net Income (loss) Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 31, 2020	Jul. 31, 2019	Jul. 31, 2020	Jul. 31, 2019
Numerator:
Net income	$ 9,339	$ 1,395	$ 17,973	$ 930
Denominator:
Denominator for basic net income per share (weighted-average shares which exclude shares in the treasury, 509,242 at July 31, 2020 and 471.289 for July 31, 2019	7,976,275	8,012,475	7,974,370	8,013,150
Effect of dilutive securities from restricted stock plan	103,469	89,867	87,948	83,077
Denominator for diluted earnings per share (adjusted weighted average shares)	8,079,744	8,102,342	8,062,318	8,096,227
Basic net income per share	$ 1.17	$ 0.17	$ 2.25	$ 0.12
Diluted net income per share	$ 1.16	$ 0.17	$ 2.23	$ 0.11