Pension Benefits (Net Periodic Pension Cost) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2020	Jan. 31, 2019
Pension and Other Postretirement Benefits Cost (Reversal of Cost) [Abstract]
Interest cost	$ 1,493	$ 1,567	$ 4,480	$ 4,702
Expected return on plan assets	(2,082)	(2,127)	(6,245)	(6,382)
Recognized net actuarial loss	423	412	1,269	1,236
Net periodic pension benefit	$ (166)	$ (148)	$ (496)	$ (444)