Benefit Plans (Summary Of Performance Shares and Units Activity) (Details) - shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Nonvested, January 1 (in shares/awards)	288,430	288,848	279,880
Granted (in shares/awards)	68,585	90,806	102,442
Vested (in shares/awards)	(98,186)	(91,224)	(90,470)
Forfeited (in shares/awards)	(1,230)	0	(3,004)
Nonvested, December 31 (in shares/awards)	257,599	288,430	288,848
Performance Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Nonvested, January 1 (in shares/awards)	116,412	127,330	131,824
Granted (in shares/awards)	23,918	35,674	40,844
Vested (in shares/awards)	(42,760)	(45,690)	(41,502)
Forfeited (in shares/awards)	(4,250)	(902)	(3,836)
Nonvested, December 31 (in shares/awards)	93,320	116,412	127,330