Condensed Consolidated Statements of Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2017	Jan. 31, 2016
Income Statement [Abstract]
Total revenue	$ 1,769,993	$ 1,565,940	$ 5,660,127	$ 5,539,132
Cost of goods sold (exclusive of depreciation and amortization, shown separately below)	1,380,364	1,194,771	4,377,185	4,313,731
Gross profit	389,629	371,169	1,282,942	1,225,401
Operating expenses	292,321	259,625	879,738	791,185
Depreciation and amortization	51,152	43,822	145,682	125,028
Interest, net	10,559	10,132	31,174	30,225
Income before income taxes	35,597	57,590	226,348	278,963
Federal and state income taxes	12,762	19,491	78,941	100,025
Net income	$ 22,835	$ 38,099	$ 147,407	$ 178,938
Net income per common share
Basic (in dollars per share)	$ 0.58	$ 0.98	$ 3.76	$ 4.59
Diluted (in dollars per share)	$ 0.58	$ 0.97	$ 3.72	$ 4.54
Basic weighted average shares outstanding (in shares)	39,194,671	39,033,987	39,183,388	39,003,820
Plus effect of stock compensation (in shares)	463,445	403,421	466,380	397,551
Diluted weighted average shares outstanding (in shares)	39,658,116	39,437,408	39,649,768	39,401,371
Dividends declared per share (in dollars per share)	$ 0.24	$ 0.22	$ 0.72	$ 0.66