|**Employee Stock And Incentive Plan (Tables)**                     | 12 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                             
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|Summary Of Value Of Restricted Stock Units                         | Years ended December 31,2014
				
				2013
				
				2012Weighted average fair value of RSUs granted
				$
				24.80
				$
				23.28
				$
				17.99                                                                                                                                                                                                                                                                                                                         
|                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|                                                                   | Years ended December 31,                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Weighted average fair value of RSUs granted                        | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Summary Of Stock Option Transactions                               | Shares
				
				Weighted Average Exercise Price
				Weighted Average Remaining Life (years)
				
				Aggregate Intrinsic ValueOutstanding, beginning of year
				1,538,110
				$
				16.82Granted
				-
				
				-Forfeited
				-
				
				-Expired
				(3,706)
				
				17.87Exercised
				(449,412)
				
				16.23Outstanding and exercisable at end of year
				1,084,992
				$
				17.06
				3.0
				$
				10,457                                                       
|                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|                                                                   | Shares                                                                                                                                                                                                                                                                                                                                                                                                                                                                      
|Outstanding, beginning of year                                     | 1,538,110                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
|Granted                                                            | -                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Forfeited                                                          | -                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Expired                                                            | (3,706)                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|Exercised                                                          | (449,412)                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
|Outstanding and exercisable at end of year                         | 1,084,992                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
|Summary Of Options Outstanding And Options Excercisable            | Options Outstanding and ExercisableShares
				Weighted Average Remaining Life (years)
				
				Weighted Average Exercise PriceRange of prices:$13.00-14.99
				327,471
				3.1
				$
				13.98$15.00-15.99
				215,674
				4.1
				
				15.30$16.00-16.99
				178,298
				3.1
				
				16.15$17.00-19.99
				164,316
				2.1
				
				18.61$20.00-23.99
				199,233
				1.2
				
				23.571,084,992
				3.0
				$
				17.06                                                 
|                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|                                                                   | Options Outstanding and Exercisable                                                                                                                                                                                                                                                                                                                                                                                                                                         
|                                                                   | Shares                                                                                                                                                                                                                                                                                                                                                                                                                                                                      
|Range of prices:                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|$13.00-14.99                                                       | 327,471                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|$15.00-15.99                                                       | 215,674                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|$16.00-16.99                                                       | 178,298                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|$17.00-19.99                                                       | 164,316                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|$20.00-23.99                                                       | 199,233                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|                                                                   | 1,084,992                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
|Summary Of Nonvested Share Activity - Restricted Stock             | Number of Shares
				
				Weighted Average Fair ValueNonvested shares at beginning of period
				62,500
				$
				17.70Granted
				14,000
				
				25.19Vested
				(45,250)
				
				20.02Forfeited
				-
				
				-Nonvested shares at end of period
				31,250
				$
				17.70                                                                                                                                                                                            
|                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|                                                                   | Number of Shares                                                                                                                                                                                                                                                                                                                                                                                                                                                            
|Nonvested shares at beginning of period                            | 62,500                                                                                                                                                                                                                                                                                                                                                                                                                                                                      
|Granted                                                            | 14,000                                                                                                                                                                                                                                                                                                                                                                                                                                                                      
|Vested                                                             | (45,250)                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Forfeited                                                          | -                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Nonvested shares at end of period                                  | 31,250                                                                                                                                                                                                                                                                                                                                                                                                                                                                      
|Performance Share Units [Member]                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Summary Of Compensation Costs                                      | Years ended December 31,2014
				
				2013
				
				2012Stock-based compensation within operations and maintenance expense
				$
				4,996
				$
				3,437
				$
				2,536Income tax benefit
				
				2,044
				
				1,400
				
				1,033                                                                                                                                                                                                                                   
|                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|                                                                   | Years ended December 31,                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Stock-based compensation within operations and maintenance expense | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Income tax benefit                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Summary Of Nonvested PSU Transactions                              | Number of Share Units
				
				Weighted Average Fair ValueNonvested share units at beginning of period
				528,092
				$
				21.25Granted
				143,630
				
				25.31Performance criteria adjustment
				81,148
				
				22.26Forfeited
				(14,078)
				
				23.53Share units vested in prior period and issued in current period
				18,000
				
				19.51Share units issued
				(174,148)
				
				18.93Nonvested share units at end of period
				582,644
				$
				22.98
|                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|                                                                   | Number of Share Units                                                                                                                                                                                                                                                                                                                                                                                                                                                       
|Nonvested share units at beginning of period                       | 528,092                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|Granted                                                            | 143,630                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|Performance criteria adjustment                                    | 81,148                                                                                                                                                                                                                                                                                                                                                                                                                                                                      
|Forfeited                                                          | (14,078)                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Share units vested in prior period and issued in current period    | 18,000                                                                                                                                                                                                                                                                                                                                                                                                                                                                      
|Share units issued                                                 | (174,148)                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
|Nonvested share units at end of period                             | 582,644                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|Assumptions Used In The Pricing Model                              | Years ended December 31,2014
				
				2013
				
				2012Expected term (years)
				
				3.0
				
				3.0
				
				3.0Risk-free interest rate
				
				0.68%
				
				0.36%
				
				0.43%Expected volatility
				
				19.8%
				
				20.0%
				
				22.1%Weighted average fair value of PSUs granted
				$
				25.31
				$
				26.88
				$
				19.11                                                                                                                         
|                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|                                                                   | Years ended December 31,                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Expected term (years)                                              |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Risk-free interest rate                                            |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Expected volatility                                                |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Weighted average fair value of PSUs granted                        | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Restricted Stock Units [Member]                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Summary Of Compensation Costs                                      | Years ended December 31,2014
				
				2013
				
				2012Stock-based compensation within operations and maintenance expense
				$
				1,122
				$
				813
				$
				634Income tax benefit
				
				464
				
				336
				
				262                                                                                                                                                                                                                                             
|                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|                                                                   | Years ended December 31,                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Stock-based compensation within operations and maintenance expense | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Income tax benefit                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Summary Of Nonvested RSU Transactions                              | Number of Stock Units
				
				Weighted Average Fair ValueNonvested stock units at beginning of period
				112,666
				$
				20.16Granted
				41,150
				
				24.80Stock units vested but not paid
				(5,750)
				
				17.99Stock units vested and paid
				(24,772)
				
				17.77Forfeited
				(729)
				
				21.77Nonvested stock units at end of period
				122,565
				$
				22.29                                                                                    
|                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|                                                                   | Number of Stock Units                                                                                                                                                                                                                                                                                                                                                                                                                                                       
|Nonvested stock units at beginning of period                       | 112,666                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|Granted                                                            | 41,150                                                                                                                                                                                                                                                                                                                                                                                                                                                                      
|Stock units vested but not paid                                    | (5,750)                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|Stock units vested and paid                                        | (24,772)                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Forfeited                                                          | (729)                                                                                                                                                                                                                                                                                                                                                                                                                                                                       
|Nonvested stock units at end of period                             | 122,565                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|Stock Options [Member]                                             |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Summary Of Compensation Costs                                      | Years ended December 31,2014
				
				2013
				
				2012Stock-based compensation within operations and maintenance expense
				$
				-
				$
				30
				$
				612Income tax benefit
				
				189
				
				461
				
				580                                                                                                                                                                                                                                                  
|                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|                                                                   | Years ended December 31,                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Stock-based compensation within operations and maintenance expense | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Income tax benefit                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Summary Of Stock Options Exercised And Vested                      | Years ended December 31,2014
				
				2013
				
				2012Intrinsic value of options exercised
				$
				4,054
				$
				12,658
				$
				5,547Fair value of options vested
				
				-
				
				500
				
				1,318                                                                                                                                                                                                                                                            
|                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|                                                                   | Years ended December 31,                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Intrinsic value of options exercised                               | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Fair value of options vested                                       |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Restricted Stock [Member]                                          |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Summary Of Compensation Costs                                      | Years ended December 31,2014
				
				2013
				
				2012Stock-based compensation within operations and maintenance expense
				$
				691
				$
				770
				$
				1,737Income tax benefit
				
				287
				
				320
				
				720                                                                                                                                                                                                                                             
|                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|                                                                   | Years ended December 31,                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Stock-based compensation within operations and maintenance expense | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Income tax benefit                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Summary Of Value Of Restricted Stock Awards                        | Years ended December 31,2014
				
				2013
				
				2012Intrinsic value of restricted stock awards vested
				$
				1,097
				$
				2,236
				$
				2,384Fair value of restricted stock awards vested
				
				906
				
				1,560
				
				1,971Weighted average fair value of restricted stock awards granted
				
				25.19
				
				25.09
				
				18.47                                                                                                                 
|                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|                                                                   | Years ended December 31,                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Intrinsic value of restricted stock awards vested                  | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Fair value of restricted stock awards vested                       |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Weighted average fair value of restricted stock awards granted     |                                                                                                                                                                                                                                                                                                                                                                                                                                                                             

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