Incentive Plans (Summary Of Activity Of Executive Continuity And Restricted Stock Award Program) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares/units, outstanding	5,950,130	5,857,733	7,275,934
Shares/units, granted	2,163,912	2,617,982	1,863,623
Shares/units, shares issued	(1,876,134)	(2,316,085)	(2,959,160)
Shares/units, forfeited	(438,024)	(209,500)	(322,664)
Shares/Units, outstanding	5,799,884	5,950,130	5,857,733
Weighted average grant date fair value, outstanding	$ 35.89	$ 38.69	$ 34.98
Weighted average grant date fair value, granted	51.78	37.26	53.25
Weighted average grant date fair value, shares issued	51.00	43.82	37.09
Weighted average grant date fair value, outstanding	36.17	35.89	38.69
Weighted average grant date fair value, forfeited	$ 45.96	$ 43.61	$ 53.97
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares/units, outstanding	169,331	120,368	114,599
Shares/units, granted	63,319	117,881	36,300
Shares/units, shares issued	(59,650)	(59,418)	(27,365)
Shares/units, forfeited	(6,700)	(9,500)	(3,166)
Shares/Units, outstanding	166,300	169,331	120,368
Weighted average grant date fair value, outstanding	$ 45.34	$ 48.24	$ 47.03
Weighted average grant date fair value, granted	57.24	42.81	50.06
Weighted average grant date fair value, shares issued	47.90	47.14	45.35
Weighted average grant date fair value, outstanding	48.63	45.34	48.24
Weighted average grant date fair value, forfeited	$ 53.53	$ 39.36	$ 50.04