Condensed Consolidated Statements Of Comprehensive Income (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Oct. 31, 2012	Oct. 31, 2011	Oct. 31, 2012	Oct. 31, 2011
Condensed Consolidated Statements Of Comprehensive Income [Abstract]
Total revenue	$ 1,911,644	$ 1,782,518	$ 3,779,946	$ 3,656,350
Cost of goods sold (exclusive of depreciation and amortization, shown separately below)	1,632,331	1,519,600	3,213,659	3,126,650
Gross profit	279,313	262,918	566,287	529,700
Operating expenses	190,040	171,832	379,439	343,248
Depreciation and amortization	27,148	23,432	53,684	46,327
Interest, net	8,637	8,777	17,541	17,711
Income before income taxes	53,488	58,877	115,623	122,414
Federal and state income taxes	20,629	21,245	43,733	45,391
Net income	32,859	37,632	71,890	77,023
Other comprehensive income
Comprehensive income	$ 32,859	$ 37,632	$ 71,890	$ 77,023
Net income per common share
Basic	$ 0.86	$ 0.99	$ 1.88	$ 2.02
Diluted	$ 0.85	$ 0.98	$ 1.86	$ 2.01
Basic weighted average shares outstanding	38,304,840	38,055,909	38,264,724	38,040,142
Plus effect of stock compensation	353,690	342,934	354,434	328,239
Diluted weighted average shares outstanding	38,658,530	38,398,843	38,619,158	38,368,381
Dividends declared per share	$ 0.165	$ 0.15	$ 0.33	$ 0.30