Condensed Consolidated Statements of Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Oct. 31, 2016	Oct. 31, 2015	Oct. 31, 2016	Oct. 31, 2015
Income Statement [Abstract]
Total revenue	$ 1,920,055	$ 1,924,600	$ 3,890,134	$ 3,973,192
Cost of goods sold (exclusive of depreciation and amortization, shown separately below)	1,476,537	1,481,610	2,996,821	3,118,960
Gross profit	443,518	442,990	893,313	854,232
Operating expenses	295,289	267,978	587,417	531,560
Depreciation and amortization	48,675	41,807	94,530	81,206
Interest, net	10,075	10,009	20,615	20,093
Income before income taxes	89,479	123,196	190,751	221,373
Federal and state income taxes	32,299	44,163	66,179	80,534
Net income	$ 57,180	$ 79,033	$ 124,572	$ 140,839
Net income per common share
Basic (in dollars per share)	$ 1.46	$ 2.03	$ 3.18	$ 3.61
Diluted (in dollars per share)	$ 1.44	$ 2.00	$ 3.14	$ 3.57
Basic weighted average shares outstanding (in shares)	39,189,804	39,002,546	39,177,746	38,987,530
Plus effect of stock compensation (in shares)	472,735	423,747	472,713	419,687
Diluted weighted average shares outstanding (in shares)	39,662,539	39,426,293	39,650,459	39,407,217
Dividends declared per share (in dollars per share)	$ 0.24	$ 0.22	$ 0.48	$ 0.44