Pension Benefits (Net Periodic Pension Cost) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Oct. 31, 2020	Oct. 31, 2019	Oct. 31, 2020	Oct. 31, 2019
Pension and Other Postretirement Benefits Cost (Reversal of Cost) [Abstract]
Interest cost	$ 1,166	$ 1,494	$ 2,331	$ 2,987
Expected return on plan assets	(2,108)	(2,082)	(4,215)	(4,163)
Recognized net actuarial loss	440	423	880	846
Net periodic pension benefit	$ (502)	$ (165)	$ (1,004)	$ (330)