Employee Benefit and Retirement Plans (Narrative) (Details) $ in Thousands	12 Months Ended
	Apr. 30, 2019 USD ($) plan	Apr. 30, 2018 USD ($)	Apr. 30, 2017 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Recognized expenses for profit-sharing contributions	$ 3,800	$ 3,700	$ 3,600
401(k) contributions, percent match of employee's annual contribution			100.00%
Effective maximum contribution of base earnings			4.00%
Number of defined benefit pension plans | plan	2
Accumulated other comprehensive loss	$ 66,300
Accumulated other comprehensive loss, net of tax	49,491	49,069
Expected recognized net actuarial losses in net periodic pension benefit cost, before tax	1,700
Expected recognized net actuarial losses in net periodic pension benefit cost, after tax	1,300
Accumulated benefit obligation	168,800	163,400
Expected company contributions to pension plan in 2015	500
Company contributions	$ 7,283	$ 19,319
Plan asset actual allocation	100.00%	100.00%
Equity Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan asset actual allocation	31.00%	40.00%
Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Percent of after tax earnings contributed in profit sharing	0.00%
Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Percent of after tax earnings contributed in profit sharing	5.00%
401(k) Plan [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
401(k) contributions, percent match of employee's annual contribution	4.00%
Eligibility period	60 days
Expense for 401(k) matching contributions	$ 9,900	$ 8,000	$ 7,200
Maximum annual contribution per employee (as a percent)	3.00%
Annually escalated percent, beginning January 1, 2021	1.00%
Maximum escalated percent	8.00%
ERROR in label resolution.
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, minimum age requirement	18 years
Defined contribution plan, minimum consecutive months employed requirement	6 months