BENEFIT PLANS: (Details 4) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Apr. 30, 2013	Apr. 30, 2012	Apr. 30, 2011
Accumulated comprehensive loss, Pre-tax	$ 19,991	$ 14,897
Net actuarial loss, Pre-tax	1,802	1,145	1,155
Amortization of net loss, Pre-tax	(1,802)	(1,145)
Accumulated comprehensive loss, Pre-tax	18,806	19,991	14,897
Accumulated comprehensive loss, Net of Tax	(12,298)	9,140
Net actuarial loss, Net of Tax	383	3,868
Amortization of net loss, Net of Tax	(1,117)	(710)
Accumulated comprehensive loss, Net of Tax	$ (11,564)	$ (12,298)	$ 9,140