Selected Quarterly Financial Data (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Oct. 31, 2014	Jul. 31, 2014	Apr. 30, 2014	Jan. 31, 2014	Oct. 31, 2013	Jul. 31, 2013	Apr. 30, 2013	Jan. 31, 2013	Oct. 31, 2014	Oct. 31, 2013	Oct. 31, 2012
Quarterly Financial Data [Abstract]
Operating Revenues	$ 185,821	$ 164,187	$ 462,247	$ 657,733	$ 200,000	$ 162,943	$ 399,411	$ 515,875	$ 1,469,988	$ 1,278,229	$ 1,122,780
Margin	112,326	104,847	211,523	261,512	109,011	97,000	183,856	231,623	690,208	621,490	575,446
Operating Income	6,993	3,254	67,299	102,319	5,886	591	51,504	86,213	179,865	144,194	125,723
Net income (loss)	$ (8,967)	$ (7,344)	$ 62,540	$ 97,572	$ (5,003)	$ (2,293)	$ 55,790	$ 85,923	$ 143,801	$ 134,417	$ 119,847
Earnings Per Share of Common Stock:
Basic (usd per share)	$ (0.11)	$ (0.09)	$ 0.80	$ 1.27	$ (0.07)	$ (0.03)	$ 0.74	$ 1.19	$ 1.85	$ 1.80	$ 1.67
Diluted (usd per share)	$ (0.11)	$ (0.09)	$ 0.80	$ 1.26	$ (0.07)	$ (0.03)	$ 0.74	$ 1.18	$ 1.84	$ 1.78	$ 1.66