Employee Benefit and Retirement Plans (Net Periodic Pension Cost) (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2016
Retirement Benefits [Abstract]
Interest cost	$ 5,727	$ 5,772	$ 7,014
Expected return on plan assets	(8,936)	(8,079)	(8,142)
Recognized net actuarial loss	1,601	1,771	1,412
Pension benefit cost	$ (1,608)	$ (536)	$ 284