Selected Quarterly Financial Data (Details) (USD $)	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
Quarterly Financial Data [Abstract]
Operating Revenues	$ 181,385,000	$ 161,123,000	$ 308,432,000	$ 471,840,000	$ 192,008,000	$ 197,274,000	$ 392,567,000	$ 652,056,000	$ 1,122,780,000	$ 1,433,905,000	$ 1,552,295,000
Margin	96,798,000	86,460,000	171,951,000	220,237,000	88,739,000	81,963,000	172,931,000	230,006,000	575,446,000	573,639,000	552,592,000
Operating Income (Loss)	(365,000)	(2,513,000)	48,782,000	79,819,000	(1,174,000)	389,000	52,927,000	90,869,000	125,723,000	143,011,000	138,278,000
Net Income (Loss)	$ (1,959,000)	$ (4,613,000)	$ 50,192,000	$ 76,227,000	$ (9,577,000)	$ (8,703,000)	$ 47,408,000	$ 84,440,000	$ 119,847,000	$ 113,568,000	$ 141,954,000
Earnings Per Share of Common Stock
Basic	$ (0.03)	$ (0.06)	$ 0.70	$ 1.06	$ (0.13)	$ (0.12)	$ 0.66	$ 1.17	$ 1.67	$ 1.58	$ 1.96
Diluted	$ (0.03)	$ (0.06)	$ 0.70	$ 1.05	$ (0.13)	$ (0.12)	$ 0.66	$ 1.16	$ 1.66	$ 1.57	$ 1.96