Restructuring Charges - Accrued Liability Rollforward (Details) - USD ($) $ in Thousands	3 Months Ended
	Jul. 31, 2017	Jul. 31, 2016
Restructuring Cost and Reserve [Line Items]
Balance at April 30, 2016	$ 1,407	$ 1,043
Restructuring charges	40	327
Payments	(1,161)	(470)
Non-cash settlements of restructuring charges	(24)
Balance at July 31, 2017	262	900
Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Balance at April 30, 2016	1,108	497
Restructuring charges	40	327
Payments	(1,148)	(341)
Non-cash settlements of restructuring charges	0
Balance at July 31, 2017	0	483
Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Balance at April 30, 2016	299	546
Restructuring charges	0	0
Payments	(13)	(129)
Non-cash settlements of restructuring charges	(24)
Balance at July 31, 2017	$ 262	$ 417