Market For Common Stock And Related Shareholder Matters (Price Ranges And Dividends Declared) (Details)	3 Months Ended								12 Months Ended
	Sep. 30, 2017 $ / shares	Jun. 30, 2017 $ / shares	Mar. 31, 2017 $ / shares	Dec. 31, 2016 $ / shares	Sep. 30, 2016 $ / shares	Jun. 30, 2016 $ / shares	Mar. 31, 2016 $ / shares	Dec. 31, 2015 $ / shares	Sep. 30, 2017 entity $ / shares
Class of Stock [Line Items]
Number of Common Stock Shareholders | entity									11,211
Dividends Declared	$ 0.415	$ 0.415	$ 0.405	$ 0.405	$ 0.405	$ 0.405	$ 0.395	$ 0.395
High [Member]
Class of Stock [Line Items]
Price Range	59.92	61.20	61.25	58.78	59.62	57.06	51.53	56.64	$ 59.92
Low [Member]
Class of Stock [Line Items]
Price Range	$ 54.89	$ 53.03	$ 54.67	$ 50.61	$ 53.81	$ 47.49	$ 39.79	$ 37.03	$ 54.89