Quarterly Financial Information (Quarterly Financial Information) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Jul. 31, 2013	Apr. 30, 2013	Jan. 31, 2013	Oct. 31, 2012	Jul. 31, 2012	Apr. 30, 2012	Jan. 31, 2012	Oct. 31, 2011	Jul. 31, 2013	Jul. 31, 2012	Jul. 31, 2011
Quarterly Financial Information [Abstract]
Net Sales	$ 632,594	$ 619,371	$ 596,036	$ 588,947	$ 656,833	$ 647,237	$ 580,883	$ 608,295	$ 2,436,948	$ 2,493,248	$ 2,294,029
Gross margin	228,356	221,501	198,977	198,293	229,783	228,229	200,817	214,934	847,127	873,763	813,796
Net earnings	$ 72,609	$ 69,842	$ 50,813	$ 54,113	$ 70,981	$ 70,946	$ 53,821	$ 68,553	$ 247,377	$ 264,301	$ 225,291
Basic earnings per share	$ 0.49	$ 0.47	$ 0.34	$ 0.36	$ 0.47	$ 0.47	$ 0.36	$ 0.46	$ 1.67	$ 1.76	$ 1.46
Diluted earnings per share	$ 0.48	$ 0.46	$ 0.34	$ 0.36	$ 0.47	$ 0.46	$ 0.35	$ 0.45	$ 1.64	$ 1.73	$ 1.43
Dividends declared per share	$ 0.130	$ 0.130	$ 0.100	$ 0.090	$ 0.090	$ 0.090	$ 0.080	$ 0.075	$ 0.450	$ 0.335	$ 0.280
Dividends paid per share	$ 0.130	$ 0.100	$ 0.090	$ 0.090	$ 0.090	$ 0.080	$ 0.075	$ 0.075