Pension Benefits (Net Periodic Pension Cost) (Details) - USD ($) $ in Thousands	3 Months Ended
	Jul. 31, 2020	Jul. 31, 2019
Pension and Other Postretirement Benefits Cost (Reversal of Cost) [Abstract]
Interest cost	$ 1,165	$ 1,493
Expected return on plan assets	(2,107)	(2,081)
Recognized net actuarial loss	440	423
Net periodic pension benefit	$ (502)	$ (165)