Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jan. 31, 2019	Jan. 31, 2018	Jan. 31, 2019	Jan. 31, 2018
Segment Reporting Information [Line Items]
Revenues from external customers	$ 32,372	$ 38,190	$ 111,802	$ 113,542
Intersegment revenues	0	0	0	0
Earnings (loss) before income taxes	35	2,529	3,688	7,069
Corporate / Eliminations
Segment Reporting Information [Line Items]
Revenues from external customers	0	0	0	0
Intersegment revenues	(2,747)	(2,506)	(5,459)	(13,589)
Earnings (loss) before income taxes	(1,045)	(1,838)	(4,491)	(4,715)
Domestic Operations | Operating Segments
Segment Reporting Information [Line Items]
Revenues from external customers	25,217	29,734	91,909	80,420
Intersegment revenues	612	1,145	1,490	10,298
Earnings (loss) before income taxes	60	3,004	6,005	7,765
International Operations | Operating Segments
Segment Reporting Information [Line Items]
Revenues from external customers	7,155	8,456	19,893	33,122
Intersegment revenues	2,135	1,361	3,969	3,291
Earnings (loss) before income taxes	$ 1,020	$ 1,363	$ 2,174	$ 4,019