Business Segments (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Oct. 31, 2015 USD ($)	Jul. 31, 2015 USD ($)	Apr. 30, 2015 USD ($)	Jan. 31, 2015 USD ($)	Oct. 31, 2014 USD ($)	Jul. 31, 2014 USD ($)	Apr. 30, 2014 USD ($)	Jan. 31, 2014 USD ($)	Oct. 31, 2015 USD ($) segment		Oct. 31, 2014 USD ($)		Oct. 31, 2013 USD ($)
Segment Reporting Information [Line Items]
Number of Reportable Segments | segment									3
Segment Reporting, Disclosure of Major Customers									0
Segment Reporting Information [Abstract]
Revenues from external customers	$ 181,257	$ 158,266	$ 424,924	$ 607,271	$ 185,821	$ 164,187	$ 462,247	$ 657,733	$ 1,371,718	[1]	$ 1,469,988	[1]	$ 1,278,229	[1]
Margin	120,031	111,572	225,621	270,070	112,326	104,847	211,523	261,512	727,294		690,208		621,490
Operations and maintenance expenses									294,703		271,101		253,301
Depreciation									128,722		119,014		112,225
Operating income (loss) before income taxes									261,594		262,655		221,176
Income from equity method investments									34,461		32,753		26,056
Interest charges									68,631		54,686		24,938
Income before income taxes									227,233		238,619		220,363
Total assets	4,949,596				4,602,754				4,949,596		4,602,754		4,174,091
Equity method investments in non-utility activities	206,956				170,171				206,956		170,171		128,469
Construction expenditures									443,654		460,444		599,999
Segment Reporting Information, Operating Income (Loss) [Abstract]
Segment income (loss) before income taxes									261,594		262,655		221,176
Utility income taxes segment									(76,934)		(83,176)		(77,334)
Operating Income	(1,085)	5,233	75,123	105,758	6,993	3,254	67,299	102,319	185,029		179,865		144,194
Segment Reporting Information, Profit (Loss) [Abstract]
Income before income taxes for reportable segments									227,233		238,619		220,363
Income taxes									(90,222)		(94,818)		(85,946)
Net Income	(14,109)	$ (8,260)	$ 66,402	$ 92,978	(8,967)	$ (7,344)	$ 62,540	$ 97,572	137,011		143,801		134,417
Segment Consolidated Assets [Abstract]
Total Assets	5,110,750				4,774,307				5,110,750		4,774,307
Operating Segments
Segment Consolidated Assets [Abstract]
Total Assets	4,949,596				4,602,754				4,949,596		4,602,754
Intersegment Eliminations
Segment Consolidated Assets [Abstract]
Total Assets	161,154				171,553				161,154		171,553
Regulated Operation
Segment Reporting Information [Abstract]
Revenues from external customers									1,371,718		1,469,988		1,278,229
Margin									727,294		690,208		621,490
Operations and maintenance expenses									294,517		270,877		253,120
Depreciation									128,704		118,996		112,207
Operating income (loss) before income taxes									261,963		263,041		221,528
Income from equity method investments									0		0		0
Interest charges									68,631		54,686		24,938
Income before income taxes									193,140		206,253		194,659
Total assets	4,742,284				4,432,239				4,742,284		4,432,239		4,045,259
Equity method investments in non-utility activities	0				0				0		0		0
Construction expenditures									443,654		460,444		599,999
Segment Reporting Information, Operating Income (Loss) [Abstract]
Segment income (loss) before income taxes									261,963		263,041		221,528
Segment Reporting Information, Profit (Loss) [Abstract]
Income before income taxes for reportable segments									193,140		206,253		194,659
Regulated Non-Utility Activities
Segment Reporting Information [Abstract]
Revenues from external customers									0		0		0
Margin									0		0		0
Operations and maintenance expenses									81		132		103
Depreciation									0		0		0
Operating income (loss) before income taxes									(152)		(183)		(150)
Income from equity method investments									15,060		12,318		10,584
Interest charges									0		0		0
Income before income taxes									14,909		12,135		10,434
Total assets	165,630				129,206				165,630		129,206		90,097
Equity method investments in non-utility activities	165,630				129,206				165,630		129,206		90,097
Construction expenditures									0		0		0
Segment Reporting Information, Operating Income (Loss) [Abstract]
Segment income (loss) before income taxes									(152)		(183)		(150)
Segment Reporting Information, Profit (Loss) [Abstract]
Income before income taxes for reportable segments									14,909		12,135		10,434
Unregulated Non-Utility Activities
Segment Reporting Information [Abstract]
Revenues from external customers									0		0		0
Margin									0		0		0
Operations and maintenance expenses									105		92		78
Depreciation									18		18		18
Operating income (loss) before income taxes									(217)		(203)		(202)
Income from equity method investments									19,401		20,435		15,472
Interest charges									0		0		0
Income before income taxes									19,184		20,231		15,270
Total assets	41,682				41,309				41,682		41,309		38,735
Equity method investments in non-utility activities	$ 41,326				$ 40,965				41,326		40,965		38,372
Construction expenditures									0		0		0
Segment Reporting Information, Operating Income (Loss) [Abstract]
Segment income (loss) before income taxes									(217)		(203)		(202)
Segment Reporting Information, Profit (Loss) [Abstract]
Income before income taxes for reportable segments									$ 19,184		$ 20,231		$ 15,270

[1] See Note 13 for amounts attributable to affiliates.