|**Business Segments (Tables)**                                          | 3 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
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|**Segment Reporting [Abstract]**                                        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|Operations By Segment                                                   | Operations by segment for thethreemonths endedJanuary 31, 2015and2014are presented below.Regulated UtilityRegulatedNon-UtilityActivitiesUnregulatedNon-UtilityActivitiesTotalIn thousands20152014201520142015201420152014Three MonthsRevenues from external customers$607,271$657,733$—$—$—$—$607,271$657,733Margin270,070261,512————270,070261,512Operations and maintenanceexpenses66,15060,639316382366,21960,668Income from equity methodinvestments——3,7713,1074,4946,8348,2659,941Operating income (loss) beforeincome taxes162,030162,121(31)(7)(121)(102)161,878162,012Income before income taxes144,401151,2693,7403,1014,3736,732152,514161,102
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|                                                                        | Regulated Utility                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|In thousands                                                            | 2015                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|Three Months                                                            |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|Revenues from external customers                                        | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Margin                                                                  | 270,070                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
|Operations and maintenance                                              |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|expenses                                                                | 66,150                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
|Income from equity method                                               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|investments                                                             | —                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Operating income (loss) before                                          |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|income taxes                                                            | 162,030                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
|Income before income taxes                                              | 144,401                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
|Reconciliation of Operating Profit (Loss) from Segments to Consolidated | Reconciliations to the condensed consolidated statements of comprehensive income for thethreemonths endedJanuary 31, 2015and2014are presented below.Three MonthsIn thousands20152014Operating Income:Segment operating income before income taxes$161,878$162,012Utility income taxes(56,272)(59,802)Regulated non-utility activities operating loss before income taxes317Unregulated non-utility activities operating loss before income taxes121102Operating income$105,758$102,319Net Income:Income before income taxes for reportable segments$152,514$161,102Income taxes(59,536)(63,530)Total$92,978$97,572                                       
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|                                                                        | Three Months                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|In thousands                                                            | 2015                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|Operating Income:                                                       |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|Segment operating income before income taxes                            | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Utility income taxes                                                    | (56,272                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
|Regulated non-utility activities operating loss before income taxes     | 31                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       
|Unregulated non-utility activities operating loss before income taxes   | 121                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      
|Operating income                                                        | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
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|Net Income:                                                             |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|Income before income taxes for reportable segments                      | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Income taxes                                                            | (59,536                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
|Total                                                                   | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        

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