Condensed Consolidated Statements of Income (Unaudited) - USD ($)	3 Months Ended
	Jul. 31, 2016	Jul. 31, 2015
Income Statement [Abstract]
Total revenue	$ 1,970,079,000	$ 2,048,592,000
Cost of goods sold (exclusive of depreciation and amortization, shown separately below)	1,520,284,000	1,637,350,000
Gross profit	449,795,000	411,242,000
Operating expenses	292,128,000	263,582,000
Depreciation and amortization	45,855,000	39,399,000
Interest, net	10,540,000	10,084,000
Income before income taxes	101,272,000	98,177,000
Federal and state income taxes	33,880,000	36,371,000
Net income	$ 67,392,000	$ 61,806,000
Net income per common share
Basic (in dollars per share)	$ 1.72	$ 1.59
Diluted (in dollars per share)	$ 1.70	$ 1.57
Basic weighted average shares outstanding (in shares)	39,156,462	38,964,765
Plus effect of stock compensation (in shares)	474,677	420,727
Diluted weighted average shares outstanding (in shares)	39,631,139	39,385,492
Dividends declared per share (in dollars per share)	$ 0.24	$ 0.22