Note 2 - Correction of Immaterial Errors (Details) - Financial Revisions - Annual Statement of Income (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended												6 Months Ended	9 Months Ended	12 Months Ended
	Apr. 30, 2014	Jan. 31, 2014	Oct. 31, 2013	Jul. 31, 2013	Apr. 30, 2013	Jan. 31, 2013	Oct. 31, 2012	Jul. 31, 2012	Apr. 30, 2012	Jan. 31, 2012	Oct. 31, 2011	Jul. 31, 2011	Oct. 31, 2013	Jan. 31, 2014	Apr. 30, 2014	Apr. 30, 2013	Apr. 30, 2012
Cost of goods sold		$ 1,513,365	$ 1,696,600	$ 1,772,328									$ 3,468,928	$ 4,982,293	$ 6,618,239	$ 6,179,771	$ 5,987,659
Interest, net		10,123	9,896	9,576									19,472	29,595	39,915	35,265	35,192
Federal and state income taxes		6,556	21,014	32,575									53,589	60,145	66,824	59,802	65,276
Net income	20,932	12,653	39,430	53,795	21,604	13,757	31,146	37,307	21,509	16,162	37,632	39,391	93,225	105,878	126,820	103,814	114,694
Net income per common share
Basic (in Dollars per share)	$ 0.54	$ 0.33	$ 1.03	$ 1.40	$ 0.56	$ 0.36	$ 0.81	$ 0.98	$ 0.56	$ 0.42	$ 0.99	$ 1.04	$ 2.43	$ 2.76	$ 3.30	$ 2.71	$ 3.01
Diluted (in Dollars per share)	$ 0.54	$ 0.33	$ 1.01	$ 1.39	$ 0.56	$ 0.36	$ 0.81	$ 0.97	$ 0.56	$ 0.42	$ 0.98	$ 1.03	$ 2.40	$ 2.73	$ 3.26	$ 2.69	$ 2.99
Scenario, Previously Reported [Member]
Cost of goods sold		1,510,182	1,693,584	1,769,239									3,462,823	4,973,005	6,605,996	6,168,475	5,984,114
Interest, net		9,947	9,748	9,456									19,204	29,151	39,270	35,048	35,192
Federal and state income taxes		7,899	22,289	33,869									56,158	64,057	72,018	64,504	66,724
Net income		$ 14,669	$ 41,319	$ 55,710									$ 97,029	$ 111,698	$ 134,514	$ 110,625	$ 116,791
Net income per common share
Basic (in Dollars per share)		$ 0.38	$ 1.07	$ 1.45									$ 2.53	$ 2.91	$ 3.50	$ 2.89	$ 3.07
Diluted (in Dollars per share)		$ 0.38	$ 1.06	$ 1.43									$ 2.50	$ 2.87	$ 3.46	$ 2.86	$ 3.04