Comprehensive Income (Loss) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Apr. 30, 2012	Apr. 30, 2011	Apr. 30, 2012	Apr. 30, 2011
Total comprehensive income (loss)
Net income (loss)	$ 27,652	$ 28,589	$ (29,570)	$ 79,069
Unrealized (loss) gain on cash flow hedges	(499)	(315)	1,179	(1,206)
Amortization of (gain) loss on post-retirement medical plans	(391)	(31)	124	(126)
Foreign currency translation adjustments	(3,936)	30,512	(34,769)	60,267
Total comprehensive income (loss)	$ 22,826	$ 58,755	$ (63,036)	$ 138,004