Commitments and Contingencies (Details) - USD ($)	1 Months Ended	12 Months Ended
	Oct. 31, 2015	Apr. 30, 2016	Apr. 30, 2015	Apr. 30, 2014
Future minimum lease payments under noncancelable operating leases
2017		$ 4,347,000
2018		3,450,000
2019		3,012,000
2020		2,854,000
2021		2,006,000
Thereafter		4,236,000
Total		19,905,000
Future minimum lease payments under non cancellable capital leases
2017		424,000
2018		304,000
2019		168,000
Total		896,000
Less: amounts representing interest		(57,000)
Present value of capital lease obligations		839,000
Less: Current portion		(390,000)
Long-term portion of capital lease obligations		449,000
Rental expense under operating leases		4,820,000	$ 4,350,000	$ 4,981,000
Letters of credit outstanding		$ 1,080,000	1,755,000
Period of claims		P3Y
Paid Settlement agreement	$ 50,000,000
Cost of sales		$ 151,995,000	155,130,000	158,090,000
ASBC
Future minimum lease payments under non cancellable capital leases
Cost of sales		3,607,000,000
UAS
Future minimum lease payments under non cancellable capital leases
Cost of sales		132,209,000	128,233,000	127,992,000
UAS | ASBC
Future minimum lease payments under non cancellable capital leases
Cost of sales		3,203,000,000
EES
Future minimum lease payments under non cancellable capital leases
Cost of sales		19,786,000	$ 26,897,000	$ 30,098,000
EES | ASBC
Future minimum lease payments under non cancellable capital leases
Cost of sales		$ 404,000,000