|**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,﻿
				
				2017
				
				2016
				
				2017
				
				2016﻿Average common shares outstanding during the period for basic computation
				
				177,609
				
				177,288
				
				177,545
				
				177,196﻿Dilutive effect of employee stock-based compensation
				
				436
				
				796
				
				497
				
				724﻿Average common shares outstanding during the period for diluted computation
				
				178,045
				
				178,084
				
				178,042
				
				177,920﻿
		﻿
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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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+ ReferencesReference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257
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