Net Income per Common Share - Reconciliation of Numerator and Denominator of Basic and Diluted Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2013	Jan. 31, 2012
Earnings Per Share [Line Items]
Net (loss) income	$ (8,684)	$ (89,954)	$ 18,504	$ (57,222)
Restricted stock dividends	(60)	(57)	(119)	(115)
Preferential dividends	0	0	(797)	(818)
Preferential dividends on dilutive stock options	0	0	(5)	(5)
Denominator for basic net income per share for both Class A and Class B	51,177	52,447	51,108	52,552
Plus: Effect of dilutive stock options	0	0	399	0
Denominator for diluted net income per share for both Class A and Class B	51,177	52,447	51,507	52,552
Class A nonvoting common stock [Member]
Earnings Per Share [Line Items]
Numerator for basic and diluted Class A and Class B net (loss) income per share	(8,744)	(90,011)	18,385	(57,337)
Basic net (loss) income (USD per share)	$ (0.17)	$ (1.72)	$ 0.36	$ (1.09)
Diluted net (loss) income (USD per share)	$ (0.17)	$ (1.72)	$ 0.36	$ (1.09)
Class B voting common stock [Member]
Earnings Per Share [Line Items]
Numerator for basic and diluted Class A and Class B net (loss) income per share	$ (8,744)	$ (90,011)	$ 17,583	$ (58,160)
Basic net (loss) income (USD per share)	$ (0.17)	$ (1.72)	$ 0.34	$ (1.11)
Diluted net (loss) income (USD per share)	$ (0.17)	$ (1.72)	$ 0.34	$ (1.11)