Condensed Consolidated Statements of Income (Unaudited) - USD ($)	3 Months Ended		9 Months Ended
	Jan. 31, 2016	Jan. 31, 2015	Jan. 31, 2016	Jan. 31, 2015
Income Statement [Abstract]
Total revenue	$ 1,565,940,000	$ 1,671,961,000	$ 5,539,132,000	$ 6,113,358,000
Cost of goods sold (exclusive of depreciation and amortization, shown separately below)	1,194,771,000	1,320,915,000	4,313,731,000	5,020,116,000
Gross profit	371,169,000	351,046,000	1,225,401,000	1,093,242,000
Operating expenses	259,625,000	238,782,000	791,185,000	727,881,000
Depreciation and amortization	43,822,000	40,431,000	125,028,000	113,955,000
Interest, net	10,132,000	10,191,000	30,225,000	31,057,000
Income before income taxes	57,590,000	61,642,000	278,963,000	220,349,000
Federal and state income taxes	19,491,000	22,323,000	100,025,000	81,064,000
Net income	$ 38,099,000	$ 39,319,000	$ 178,938,000	$ 139,285,000
Net income per common share
Basic (in dollars per share)	$ 0.98	$ 1.01	$ 4.59	$ 3.60
Diluted (in dollars per share)	$ 0.97	$ 1.01	$ 4.54	$ 3.57
Basic weighted average shares outstanding (in shares)	39,033,987	38,795,477	39,003,820	38,701,232
Plus effect of stock compensation (in shares)	403,421	322,674	397,551	309,125
Diluted weighted average shares outstanding (in shares)	39,437,408	39,118,151	39,401,371	39,010,357
Dividends	$ 0.22	$ 0.20	$ 0.66	$ 0.60