Pension Benefits (Net Periodic Pension Cost) (Details) - USD ($) $ in Thousands	3 Months Ended
	Jul. 31, 2021	Jul. 31, 2020
Pension and Other Postretirement Benefits Cost (Reversal of Cost) [Abstract]
Interest cost	$ 1,349	$ 1,165
Expected return on plan assets	(1,543)	(2,107)
Recognized net actuarial loss	499	440
Net periodic pension benefit	$ 305	$ (502)