Deferred Compensation And Retirement Plans (Components Of Net Periodic Benefit Costs) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2016	Apr. 30, 2015	Apr. 30, 2014
Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 167	$ 154	$ 137
Amortization of actuarial loss	128	21	8
Net periodic benefit cost	295	$ 175	$ 145
Pension Plans, Defined Benefit | Hay Group
Defined Benefit Plan Disclosure [Line Items]
Interest cost	554
Expected return on plan assets	(682)
Net periodic benefit cost	(128)
Supplemental Pension Benefits | Hay Group
Defined Benefit Plan Disclosure [Line Items]
Interest cost	58
Net periodic benefit cost	58
Medical And Life Insurance | Hay Group
Defined Benefit Plan Disclosure [Line Items]
Service cost	62
Interest cost	208
Net periodic benefit cost	$ 270