Discontinued operations (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jul. 31, 2014	Jul. 31, 2013	Jul. 31, 2014	Jul. 31, 2013
Discontinued operations
Net proceeds from sale of discontinued operations			$ 0	$ 16,378
Disposal date HVAC subsidiary			Jun. 26, 2013
Net sales	0	863	176	11,282
(Loss) gain on disposal of discontinued operations	0	(1,617)	(12)	9,953
(Loss) income from discontinued operations	(111)	1,574	(178)	1,729
(Loss) income from discontinued operations before income taxes	(111)	(43)	(190)	11,682
Income tax expense	0	42	292	2,398
(Loss) income from discontinued operations, net of tax	$ (111)	$ (85)	$ (482)	$ 9,284