Restructuring Charges - Accrued Liability Rollforward (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2017	Jan. 31, 2016
Restructuring Cost and Reserve [Line Items]
Balance at April 30, 2016			$ 1,043
Restructuring charges	$ 0	$ 0	1,094	$ 0
Payments			(1,221)
Non-cash settlements of restructuring charges			(566)
Balance at January 31, 2017	350		350
Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Balance at April 30, 2016			497
Restructuring charges			459
Payments			(941)
Non-cash settlements of restructuring charges			0
Balance at January 31, 2017	15		15
Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Balance at April 30, 2016			546
Restructuring charges			635
Payments			(280)
Non-cash settlements of restructuring charges			(566)
Balance at January 31, 2017	$ 335		$ 335