Benefit Plans (Summary Of Performance Shares and Performance Units Activity) (Details) - shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
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)	223,511	257,599	288,430
Granted (in shares/awards)	74,163	65,350	68,585
Vested (in shares/awards)	(90,806)	(99,438)	(98,186)
Forfeited (in shares/awards)	(3,680)	0	(1,230)
Nonvested, December 31 (in shares/awards)	203,188	223,511	257,599
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)	71,737	93,320	116,412
Granted (in shares/awards)	19,840	21,558	23,918
Vested (in shares/awards)	(31,910)	(37,395)	(42,760)
Forfeited (in shares/awards)	(1,906)	(5,746)	(4,250)
Nonvested, December 31 (in shares/awards)	57,761	71,737	93,320