Stock-Based Compensation (Schedule Of Stock Option Plans Activity) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Shares
Options outstanding at beginning of year (in shares)	169,000
Options exercised (in shares)	(78,000)
Options forfeited and expired (in shares)	0
Options outstanding at end of year (in shares)	91,000	169,000
Options exercisable at end of year (in shares)	90,000
Weighted average exercise price
Options exercised during the year (usd per share)	$ 59.24
Options outstanding at the end of year (usd per share)	63.84	$ 61.73
Options exercisable at end of year (usd per share)	$ 63.82
Stock options plans
Shares
Options outstanding at beginning of year (in shares)	169,000	298,000	425,000
Options exercised (in shares)	(78,000)	(66,000)	(108,000)
Options forfeited and expired (in shares)	0	(63,000)	(19,000)
Options outstanding at end of year (in shares)	91,000	169,000	298,000
Options exercisable at end of year (in shares)	90,000	164,000	257,000
Minimum
Weighted average exercise price
Options exercised during the year (usd per share)	$ 28.37	$ 28.37	$ 28.37
Options forfeited and expired during the year (usd per share)	0.00	28.37	46.80
Options outstanding at the end of year (usd per share)	57.34	28.37	28.37
Options exercisable at end of year (usd per share)	57.34	28.37	28.37
Maximum
Weighted average exercise price
Options exercised during the year (usd per share)	93.65	93.65	93.65
Options forfeited and expired during the year (usd per share)	0.00	88.33	93.65
Options outstanding at the end of year (usd per share)	66.14	93.65	93.65
Options exercisable at end of year (usd per share)	$ 66.14	$ 93.65	$ 93.65