Deferred and restricted stock (Details) - USD ($)	12 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
Restricted stock [Line Items]
Deferred compensation liabilities	$ 815,000	$ 529,000
Vesting period	P4Y
Restricted stock grants	178,000	254,000
Restricted stock granted, weighted average grant price	$ 8.06	$ 7.29
Restricted stock issued	(101,000)	(123,000)
Restricted stock forfeited	(7,000)	(4,000)
Restricted stock, forfeitures, weighted average grant price	$ 7.15	$ 6.72
Deferred shares outstanding		290,000	163,000
Restricted stock, outstanding, weighted average grant price	$ 9.05	$ 8.75	$ 6.40
Restricted stock, aggregate intrinsic value	$ 3,254,000	$ 2,533,000	$ 1,040,000
Unrecognized restricted stock expense	$ 100,000
Cost is expected to be recognized over the weighted-average period	1 year
Director [Member]
Restricted stock [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Method of Measuring Cost of Award	mark-to-market adjustment on a quarterly basis
Deferred shares granted value	$ 40,000
Vesting period	stock vests on the date of grant
distributed to the directors upon their separation from service	distributed to the directors upon their separation from service
Deferred shares outstanding	90,070
Restricted Stock [Member]
Restricted stock [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Method of Measuring Cost of Award	The Company calculates restricted stock compensation expense based on the grant date fair value and recognizes expense on a straight-line basis over the vesting period.
Deferred shares outstanding	360,000
Unrecognized restricted stock expense	$ 1,400,000
Cost is expected to be recognized over the weighted-average period	1 year 1 month
Restricted Stock [Member] | Minimum [Member]
Restricted stock [Line Items]
Vesting period restricted stock	3 years
Restricted Stock [Member] | Maximum [Member]
Restricted stock [Line Items]
Vesting period restricted stock	4 years