Segment Information (Details 1) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Oct. 31, 2011	Oct. 31, 2010
Segment Reporting Information [Line Items]
Total profit for reportable segments	$ 82,833	$ 80,249
Unallocated amounts:
Administrative costs	(30,480)	(31,569)
Restructuring charges	0	(3,641)
Investment and other income (expense)	(202)	290
Interest expense	(5,047)	(5,687)
Income before income taxes	43,841	36,206
Income taxes	(11,109)	(9,925)
Net income	32,732	26,281
Corporate and Eliminations [Member]
Segment Reporting Information [Line Items]
Corporate and eliminations	$ (3,263)	$ (3,436)