BENEFIT PLANS: (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2015	Apr. 30, 2014
Interest cost on projected benefit obligation	$ 1,370	$ 1,294
Expected return on assets	(2,230)	(2,075)
Plan expenses	247	234
Recognized net actuarial loss	1,257	1,662
Settlement (gain) loss	1,067	0
Total cost recognized in pretax income	1,711	1,115
Cost (gain) recognized in pretax other comprehensive income	2,674	(3,853)
Net periodic pension cost (income)	$ 4,385	$ (2,738)