|**Net Income Per Common Share (Tables)**                                     | 6 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
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|**Net Income Per Common Share [Abstract]**                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Schedule Of Earnings Per Share                                               | ﻿﻿﻿
				
				Three Months Ended
				
				Six Months Ended﻿
				
				June 30,
				
				June 30,﻿
				
				2018
				
				2017
				
				2018
				
				2017﻿Average common shares outstanding during the period for basic computation
				
				177,901
				
				177,609
				
				177,852
				
				177,545﻿Dilutive effect of employee stock-based compensation
				
				372
				
				436
				
				447
				
				497﻿Average common shares outstanding during the period for diluted computation
				
				178,273
				
				178,045
				
				178,299
				
				178,042﻿
		﻿
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|﻿Average common shares outstanding during the period for basic computation   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|﻿Dilutive effect of employee stock-based compensation                        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|﻿Average common shares outstanding during the period for diluted computation |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
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