Business Segments (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
Segment Reporting Information [Abstract]
Revenues from external customers									$ 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
Operations and maintenance expenses									242,701,000	225,460,000	220,130,000
Depreciation									103,210,000	102,857,000	98,523,000
Income from equity method investments									23,904,000	24,027,000	28,854,000
Gain on sale of interest in equity method investment									0	0	49,674,000
Interest expense									20,097,000	43,992,000	43,711,000
Operating Income (Loss) Before Income Taxes									194,560,000	206,959,000	199,663,000
Income before income taxes									198,064,000	185,854,000	233,830,000
Total assets	3,563,887,000				3,054,093,000				3,563,887,000	3,054,093,000	2,864,895,000
Equity method investments in non-utility activities	87,867,000				85,121,000				87,867,000	85,121,000	80,287,000
Utility capital expenditures									529,576,000	243,641,000	199,059,000
Segment Reporting Information Operating Income Loss Abstract
Segment Operating Income Before Income Taxes									194,560,000	206,959,000	199,663,000
Utility income taxes									69,101,000	64,068,000	62,082,000
Non Utility Activities Before Income Taxes									264,000	120,000	697,000
Operating Income	(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 by segment
Income before income taxes for reportable segments									198,064,000	185,854,000	233,830,000
Income taxes									(78,217,000)	(72,286,000)	(91,876,000)
Net Income	(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
Segment Consolidated Assets [Abstract]
Total Assets	3,769,939,000				3,242,541,000				3,769,939,000	3,242,541,000
Segment Reporting, Disclosure of Major Customers									No single customer accounts for more than 10% of our consolidated revenues.
Regulated Operation [Member]
Segment Reporting Information [Abstract]
Revenues from external customers									1,122,780,000	1,433,905,000	1,552,295,000
Margin									575,446,000	573,639,000	552,592,000
Operations and maintenance expenses									242,599,000	225,351,000	219,829,000
Depreciation									103,192,000	102,829,000	98,494,000
Income from equity method investments									0	0	0
Gain on sale of interest in equity method investment											0
Interest expense									20,097,000	43,992,000	43,711,000
Operating Income (Loss) Before Income Taxes									194,824,000	207,079,000	200,360,000
Income before income taxes									174,424,000	161,925,000	155,923,000
Total assets	3,475,640,000				2,968,574,000				3,475,640,000	2,968,574,000	2,784,087,000
Equity method investments in non-utility activities	0				0				0	0	0
Utility capital expenditures									529,576,000	243,641,000	199,059,000
Segment Reporting Information Operating Income Loss Abstract
Segment Operating Income Before Income Taxes									194,824,000	207,079,000	200,360,000
Non Utility Activities [Member]
Segment Reporting Information [Abstract]
Revenues from external customers									0	0	0
Margin									0	0	0
Operations and maintenance expenses									102,000	109,000	301,000
Depreciation									18,000	28,000	29,000
Income from equity method investments									23,904,000	24,027,000	28,854,000
Gain on sale of interest in equity method investment											49,674,000
Interest expense									0	0	0
Operating Income (Loss) Before Income Taxes									(264,000)	(120,000)	(697,000)
Income before income taxes									23,640,000	23,929,000	77,907,000
Total assets	88,247,000				85,519,000				88,247,000	85,519,000	80,808,000
Equity method investments in non-utility activities	87,867,000				85,121,000				87,867,000	85,121,000	80,287,000
Utility capital expenditures									0	0	0
Segment Reporting Information Operating Income Loss Abstract
Segment Operating Income Before Income Taxes									(264,000)	(120,000)	(697,000)
Reportable Segment [Member]
Segment Consolidated Assets [Abstract]
Total Assets	3,563,887,000				3,054,093,000				3,563,887,000	3,054,093,000
Corporate Elimination [Member]
Segment Consolidated Assets [Abstract]
Total Assets	$ 206,052,000				$ 188,448,000				$ 206,052,000	$ 188,448,000