Quarterly Financial Information (Revisons to Previously Issued Unaudited Quarterly Financial Information) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Jul. 31, 2015	Apr. 30, 2015	Jan. 31, 2015	Oct. 31, 2014	Jul. 31, 2014	Apr. 30, 2014	Jan. 31, 2014	Oct. 31, 2013	Jul. 31, 2015	Jul. 31, 2014	Jul. 31, 2013
Net Sales	$ 610,578	$ 575,588	$ 588,537	$ 596,510	$ 668,226	$ 624,234	$ 581,622	$ 599,384	$ 2,371,213	$ 2,473,466	$ 2,436,948
Cost of sales		381,488	385,449						1,562,629	1,595,640	1,589,821
Gross margin	202,344	194,100	203,088	209,052	238,323	223,461	201,648	214,394	808,584	877,826	847,127
Operating income		67,116	65,839						288,310	355,739	343,329
Earnings before income taxes		67,849	65,424						288,603	360,703	348,181
Income taxes		20,073	17,469						80,492	100,479	100,804
Net earnings	$ 56,433	$ 47,776	$ 47,955	$ 55,947	$ 72,956	$ 67,336	$ 58,340	$ 61,592	$ 208,111	$ 260,224	$ 247,377
Basic earnings per share	$ 0.41	$ 0.35	$ 0.35	$ 0.40	$ 0.51	$ 0.46	$ 0.40	$ 0.42	$ 1.51	$ 1.79	$ 1.67
Diluted earnings per share	$ 0.41	$ .34	$ 0.34	$ 0.40	$ 0.50	$ 0.46	$ 0.39	$ 0.41	$ 1.49	$ 1.76	$ 1.64
Comprehensive income		$ 46,989	$ 1,786						$ 91,931	$ 251,887	$ 311,792
As Previously Reported [Member]
Net Sales		568,013	596,944
Cost of sales		376,040	391,469
Gross margin		191,973	205,475
Operating income		64,989	68,226
Earnings before income taxes		65,722	67,811
Income taxes		19,350	18,281
Net earnings		$ 46,372	$ 49,530
Basic earnings per share		$ 0.34	$ 0.36
Diluted earnings per share		$ 0.33	$ 0.35
Comprehensive income		$ 45,585	$ 3,361
Effect of Revision [Member]
Net Sales		7,575	(8,407)
Cost of sales		5,448	(6,020)
Gross margin		2,127	(2,387)
Operating income		2,127	(2,387)
Earnings before income taxes		2,127	(2,387)
Income taxes		723	(812)
Net earnings		$ 1,404	$ (1,575)
Basic earnings per share		$ 0.01	$ (0.01)
Diluted earnings per share		$ 0.01	$ (0.01)
Comprehensive income		$ 1,404	$ (1,575)