Pension Benefits (Net Periodic Pension Cost) (Details) - USD ($) $ in Thousands	3 Months Ended
	Jul. 31, 2015	Jul. 31, 2014
Pension and Other Postretirement Benefit Expense [Abstract]
Interest cost	$ 1,754	$ 1,617
Expected return on plan assets	(2,036)	(1,917)
Recognized net actuarial loss	353	216
Net periodic pension (benefit) cost	$ 71	$ (84)