Pension Benefits (Net Periodic Pension Cost) (Details) - USD ($) $ in Thousands	3 Months Ended
	Jul. 31, 2019	Jul. 31, 2018
Pension and Other Postretirement Benefits Cost (Reversal of Cost) [Abstract]
Interest cost	$ 1,493	$ 1,567
Expected return on plan assets	(2,081)	(2,127)
Recognized net actuarial loss	423	412
Net periodic pension benefit	$ (165)	$ (148)