|**Employee Stock And Incentive Plan (Tables)**                                                                                                                            | 12 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
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|**Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                                                                                        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|Summary Of Value Of Restricted Stock Units                                                                                                                                | Years ended December 31,201920182017Weighted average fair value of RSUs granted$36.25$35.15$30.37Intrinsic value of vested RSUs1,4561,605896Fair value of vested RSUs1,3411,268751                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       
|                                                                                                                                                                          |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|                                                                                                                                                                          | Years ended December 31,                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
|                                                                                                                                                                          |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|Weighted average fair value of RSUs granted                                                                                                                               | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Intrinsic value of vested RSUs                                                                                                                                            |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|Fair value of vested RSUs                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|Performance Share Units [Member]                                                                                                                                          |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|**Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                                                                                        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|Schedule Of Performance Goals                                                                                                                                             | Performance Grant of:20182017Metric 1 – Company’s total shareholder return (“TSR”) compared to the TSR for a specific peer group of investor-owned water companies (a market-based condition)25.0%26.47%Metric 2 – Company’s TSR compared to the TSR for the companies listed in the Standard and Poor’s Midcap Utilities Index (a market-based condition)25.0%26.47%Metric 3 – Achievement of a targeted cumulative level of rate base growth as a result of acquisitions (a performance-based condition)25.0%23.53%Metric 4 – Achievement of targets for maintaining consolidated operations and maintenance expenses over the three year measurement period (a performance-based condition)25.0%23.53%
|                                                                                                                                                                          |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|                                                                                                                                                                          | Performance Grant of:                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|                                                                                                                                                                          | 2018                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|Metric 1 – Company’s total shareholder return (“TSR”) compared to the TSR for a specific peer group of investor-owned water companies (a market-based condition)          | 25.0%                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Metric 2 – Company’s TSR compared to the TSR for the companies listed in the Standard and Poor’s Midcap Utilities Index (a market-based condition)                        | 25.0%                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Metric 3 – Achievement of a targeted cumulative level of rate base growth as a result of acquisitions (a performance-based condition)                                     | 25.0%                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Metric 4 – Achievement of targets for maintaining consolidated operations and maintenance expenses over the three year measurement period (a performance-based condition) | 25.0%                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Summary Of Compensation Costs                                                                                                                                             | Years ended December 31,201920182017Stock-based compensation within operations and maintenance expense$2,741$4,817$4,351Income tax benefit7671,3441,766                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
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|                                                                                                                                                                          | Years ended December 31,                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
|                                                                                                                                                                          |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|Stock-based compensation within operations and maintenance expense                                                                                                        | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Income tax benefit                                                                                                                                                        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|Summary Of Nonvested PSU Transactions                                                                                                                                     | Number of Share UnitsWeighted Average Fair ValueNonvested share units at beginning of period443,410$27.20Granted--Performance criteria adjustment(82,921)33.56Forfeited(9,767)33.21Share units issued(89,324)52.39Nonvested share units at end of period261,39816.35                                                                                                                                                                                                                                                                                                                                                                                                                                     
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|                                                                                                                                                                          | Number of Share Units                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Nonvested share units at beginning of period                                                                                                                              | 443,410                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
|Granted                                                                                                                                                                   | -                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Performance criteria adjustment                                                                                                                                           | (82,921)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
|Forfeited                                                                                                                                                                 | (9,767)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
|Share units issued                                                                                                                                                        | (89,324)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
|Nonvested share units at end of period                                                                                                                                    | 261,398                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
|Assumptions Used In The Pricing Model                                                                                                                                     | Years ended December 31,201920182017Expected term (years)-3.03.0Risk-free interest rate-2.43%1.49%Expected volatility-17.2%17.9%Weighted average fair value of PSUs granted$-$37.42$30.79Intrinsic value of vested PSUs$3,181$4,704$3,926Fair value of vested PSUs$2,569$3,613$3,207                                                                                                                                                                                                                                                                                                                                                                                                                     
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|                                                                                                                                                                          | Years ended December 31,                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
|                                                                                                                                                                          |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|Expected term (years)                                                                                                                                                     |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|Risk-free interest rate                                                                                                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|Expected volatility                                                                                                                                                       |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|Weighted average fair value of PSUs granted                                                                                                                               | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Intrinsic value of vested PSUs                                                                                                                                            | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Fair value of vested PSUs                                                                                                                                                 | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Restricted Stock Units [Member]                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|**Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                                                                                        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|Summary Of Compensation Costs                                                                                                                                             | Years ended December 31,201920182017Stock-based compensation within operations and maintenance expense$1,650$1,605$1,183Income tax benefit466456489                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      
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|                                                                                                                                                                          | Years ended December 31,                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
|                                                                                                                                                                          |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|Stock-based compensation within operations and maintenance expense                                                                                                        | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Income tax benefit                                                                                                                                                        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|Summary Of Nonvested RSU Transactions                                                                                                                                     | Number of Stock UnitsWeighted Average Fair ValueNonvested stock units at beginning of period130,085$33.13Granted57,29036.25Stock units vested and issued(40,971)32.89Forfeited(4,520)35.28Nonvested stock units at end of period141,88434.39                                                                                                                                                                                                                                                                                                                                                                                                                                                             
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|                                                                                                                                                                          | Number of Stock Units                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Nonvested stock units at beginning of period                                                                                                                              | 130,085                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
|Granted                                                                                                                                                                   | 57,290                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
|Stock units vested and issued                                                                                                                                             | (40,971)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
|Forfeited                                                                                                                                                                 | (4,520)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
|Nonvested stock units at end of period                                                                                                                                    | 141,884                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
|Stock Options [Member]                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|**Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                                                                                        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|Summary Of Compensation Costs                                                                                                                                             | Years ended December 31,201920182017Stock-based compensation within operations and maintenance expenses$2,280$546$245Income tax benefit643184208                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         
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|                                                                                                                                                                          | Years ended December 31,                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
|                                                                                                                                                                          |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|Stock-based compensation within operations and maintenance expenses                                                                                                       | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Income tax benefit                                                                                                                                                        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|Assumptions Used In The Pricing Model                                                                                                                                     | Years ended December 31,201920182017Expected term (years)5.475.465.45Risk-free interest rate2.53%2.72%2.01%Expected volatility17.7%17.2%17.7%Dividend yield2.44%2.37%2.51%Grant date fair value per option$5.25$5.10$4.07                                                                                                                                                                                                                                                                                                                                                                                                                                                                                
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|                                                                                                                                                                          |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|                                                                                                                                                                          | Years ended December 31,                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
|                                                                                                                                                                          | 2019                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|Expected term (years)                                                                                                                                                     |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|Risk-free interest rate                                                                                                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|Expected volatility                                                                                                                                                       |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|Dividend yield                                                                                                                                                            |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|Grant date fair value per option                                                                                                                                          | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Summary Of Stock Option Transactions                                                                                                                                      | SharesWeighted Average Exercise PriceWeighted Average Remaining Life (years)Aggregate Intrinsic ValueOutstanding, beginning of year422,972$25.97Granted769,11535.94Forfeited(36,479)35.46Expired / Cancelled(2,532)32.28Exercised(119,306)15.91Outstanding at end of year1,033,770$34.208.4$13,171Exercisable at end of year164,117$26.865.4$3,296                                                                                                                                                                                                                                                                                                                                                       
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|                                                                                                                                                                          | Shares                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
|Outstanding, beginning of year                                                                                                                                            | 422,972                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
|Granted                                                                                                                                                                   | 769,115                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
|Forfeited                                                                                                                                                                 | (36,479)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
|Expired / Cancelled                                                                                                                                                       | (2,532)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
|Exercised                                                                                                                                                                 | (119,306)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                
|Outstanding at end of year                                                                                                                                                | 1,033,770                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                
|                                                                                                                                                                          |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|Exercisable at end of year                                                                                                                                                | 164,117                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
|Summary Of Stock Options Exercised And Vested                                                                                                                             | Years ended December 31,201920182017Intrinsic value of options exercised$2,552$1,806$2,767Fair value of options vested422156-                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
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|                                                                                                                                                                          | Years ended December 31,                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
|                                                                                                                                                                          |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|Intrinsic value of options exercised                                                                                                                                      | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Fair value of options vested                                                                                                                                              |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|Summary Of Options Outstanding And Options Excercisable                                                                                                                   | Options OutstandingOptions ExercisableSharesWeighted Average Remaining Life (years)Weighted Average Exercise PriceSharesWeighted Average Exercise PriceRange of prices:$13.00-14.9947,3880.1$13.7247,388$13.72$15.00-33.9999,6617.230.4767,64930.47$34.00-34.99138,1138.234.5146,21434.51$35.00-35.99748,6089.235.932,86635.441,033,7708.434.20164,11726.86                                                                                                                                                                                                                                                                                                                                              
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|                                                                                                                                                                          |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|                                                                                                                                                                          | Options Outstanding                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      
|                                                                                                                                                                          | Shares                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
|Range of prices:                                                                                                                                                          |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|$13.00-14.99                                                                                                                                                              | 47,388                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
|$15.00-33.99                                                                                                                                                              | 99,661                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
|$34.00-34.99                                                                                                                                                              | 138,113                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
|$35.00-35.99                                                                                                                                                              | 748,608                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
|                                                                                                                                                                          | 1,033,770                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                
|Stock Awards [Member]                                                                                                                                                     |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|**Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                                                                                        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|Summary Of Compensation Costs                                                                                                                                             | Years ended December 31,201920182017Stock-based compensation within operations and maintenance expense$698$600$563Income tax benefit202173233                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
|                                                                                                                                                                          |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|                                                                                                                                                                          |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|                                                                                                                                                                          | Years ended December 31,                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
|                                                                                                                                                                          |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|Stock-based compensation within operations and maintenance expense                                                                                                        | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Income tax benefit                                                                                                                                                        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|Summary Of Value Of Stock Awards                                                                                                                                          | Years ended December 31,201920182017Intrinsic and fair value of stock awards vested$698$600$563Weighted average fair value of stock awards granted41.7534.9534.42                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
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|                                                                                                                                                                          |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|                                                                                                                                                                          | Years ended December 31,                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
|                                                                                                                                                                          |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|Intrinsic and fair value of stock awards vested                                                                                                                           | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Weighted average fair value of stock awards granted                                                                                                                       |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|Summary Of Nonvested Share Activity                                                                                                                                       | Number of Stock AwardsWeighted Average Fair ValueNonvested stock awards at beginning of period-$-Granted16,71441.75Vested(16,714)41.75Nonvested stock awards at end of period--                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|                                                                                                                                                                          |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|                                                                                                                                                                          | Number of Stock Awards                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
|Nonvested stock awards at beginning of period                                                                                                                             | -                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Granted                                                                                                                                                                   | 16,714                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
|Vested                                                                                                                                                                    | (16,714)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
|Nonvested stock awards at end of period                                                                                                                                   | -                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        

X- DefinitionTabular disclosure of allocation of amount expensed and capitalized for award under share-based payment arrangement to statement of income or comprehensive income and statement of financial position. Includes, but is not limited to, corresponding line item in financial statement.
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