Calculation of Earnings or Loss Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Oct. 31, 2012	Jul. 31, 2012	Apr. 30, 2012	Jan. 31, 2012	Oct. 31, 2011	Jul. 31, 2011	Apr. 30, 2011	Jan. 31, 2011	Oct. 31, 2012	Oct. 31, 2011	Oct. 31, 2010
Earnings Per Share Disclosure [Line Items]
Net income (loss)	$ 9,347	$ 28,721	$ 23,865	$ (7,989)	$ (21,562)	$ (55,683)	$ (16,276)	$ (33,556)	$ 53,944	$ (127,077)	$ 134,820
Distributed and undistributed (earnings) to unvested restricted stock									(1,612)	0
Distributed and undistributed earnings to common shareholders - Basic									$ 52,332	$ (127,077)
Weighted average shares outstanding - Basic									22,280	22,130
Weighted average shares outstanding - Diluted									22,282	22,130
Earnings per common share - Basic									$ 2.35	$ (5.74)	$ 6.07
Earnings per common share - Diluted	$ 0.41	$ 1.25	$ 1.05	$ (0.36)	$ (0.97)	$ (2.51)	$ (0.74)	$ (1.52)	$ 2.35	$ (5.74)	$ 6.07