Segment Information - Segment Information (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Apr. 30, 2018	Jan. 31, 2018	Oct. 31, 2017	Jul. 31, 2017	Apr. 30, 2017	Jan. 31, 2017	Oct. 31, 2016	Jul. 31, 2016	Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2016
Segment Reporting Information [Line Items]
Revenues	$ 44,508	$ 38,190	$ 41,471	$ 33,881	$ 34,579	$ 30,371	$ 36,329	$ 37,279	$ 158,050	$ 138,558	$ 128,626
Depreciation									2,761	2,702	2,592
Earnings (loss) before income taxes									9,480	6,746	5,739
Income tax expense (benefit)									4,115	2,126	1,862
Net earnings attributable to noncontrolling interest	57	35	41	44	7	17	51	30	177	105	75
Net earnings (loss) attributable to Kewaunee Scientific Corporation	1,433	$ 883	$ 1,724	$ 1,148	1,388	$ 341	$ 1,486	$ 1,300	5,188	4,515	3,802
Segment assets	84,358				80,916				84,358	80,916	72,405
Expenditures for segment assets									3,395	2,611	2,187
Non-US [Member]
Segment Reporting Information [Line Items]
Revenues									44,924	27,045	27,373
Corporate / Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment revenues									(15,437)	(8,154)	(6,921)
Earnings (loss) before income taxes									(6,238)	(4,982)	(4,470)
Income tax expense (benefit)									(3,433)	(1,595)	(1,076)
Net earnings (loss) attributable to Kewaunee Scientific Corporation									(2,805)	(3,387)	(3,394)
Domestic [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues									114,594	113,081	103,047
Intersegment revenues									11,333	4,463	3,612
Depreciation									2,532	2,478	2,375
Earnings (loss) before income taxes									10,732	8,221	7,471
Income tax expense (benefit)									5,892	2,522	1,834
Net earnings (loss) attributable to Kewaunee Scientific Corporation									4,840	5,699	5,637
Segment assets	60,879				57,246				60,879	57,246	54,030
Expenditures for segment assets									2,826	2,572	1,995
Domestic [Member] | Operating Segments [Member] | Non-US [Member]
Segment Reporting Information [Line Items]
Revenues									1,468	1,568	1,794
International [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues									43,456	25,477	25,579
Intersegment revenues									4,104	3,691	3,309
Depreciation									229	224	217
Earnings (loss) before income taxes									4,986	3,507	2,738
Income tax expense (benefit)									1,656	1,199	1,104
Net earnings attributable to noncontrolling interest									177	105	75
Net earnings (loss) attributable to Kewaunee Scientific Corporation									3,153	2,203	1,559
Segment assets	$ 23,479				$ 23,670				23,479	23,670	18,375
Expenditures for segment assets									569	39	192
International [Member] | Operating Segments [Member] | Non-US [Member]
Segment Reporting Information [Line Items]
Revenues									$ 43,456	$ 25,477	$ 25,579