Share-Based Compensation (Schedule Of Stock Option Activity) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Options outstanding, January 1	541,679	741,676	871,671
Options outstanding, December 31	859,182	541,679	741,676
Options exercisable, December 31	465,831
Weighted Average Exercise Price, Options outstanding, January 1	$ 65.84	$ 60.43	$ 60.43
Weighted Average Exercise Price, Options outstanding, December 31	70.11	$ 65.84	$ 60.43
Weighted Average Exercise Price, Options exercisable, December 31	$ 69.85
Weighted Average Remaining Contractual Life (Years), Options outstanding, December 31	3 years 4 months 22 days
Weighted Average Remaining Contractual Life (Years), Options exercisable, December 31	3 years 4 days
Aggregate Intrinsic Value, Options outstanding, December 31	$ 4,531
Aggregate Intrinsic Value, Options exercisable, December 31	$ 2,578
2005 Plan [Member]
Options granted			20,000
Options exercised	(15,000)	(61,666)	(66,670)
Weighted Average Exercise Price, Options granted			$ 72.11
Weighted Average Exercise Price, Options exercised	$ 47.52	$ 52.36	$ 46.87
2012 Plan [Member]
Options granted	495,000	470,000	450,000
Options exercised	(155,829)	(608,331)	(421,657)
Options forfeited	(6,668)		(111,668)
Weighted Average Exercise Price, Options granted	$ 74.90	$ 60.78	$ 72.11
Weighted Average Exercise Price, Options exercised	65.73	$ 65.18	63.03
Weighted Average Exercise Price, Options forfeited	$ 60.52		$ 71.95
Grant Date 2-25-2013
Options outstanding, December 31	15,000
Weighted Average Exercise Price, Options outstanding, December 31	$ 64.49
Weighted Average Remaining Contractual Life (Years), Options outstanding, December 31	1 month 26 days
Grant Date 2-25-2014
Options outstanding, December 31	48,334
Weighted Average Exercise Price, Options outstanding, December 31	$ 61.31
Weighted Average Remaining Contractual Life (Years), Options outstanding, December 31	1 year 1 month 26 days
Grant Date 2-20-2015
Options outstanding, December 31	120,004
Weighted Average Exercise Price, Options outstanding, December 31	$ 72.11
Weighted Average Remaining Contractual Life (Years), Options outstanding, December 31	2 years 1 month 21 days
Grant Date 2-22-2016
Options outstanding, December 31	185,842
Weighted Average Exercise Price, Options outstanding, December 31	$ 60.52
Weighted Average Remaining Contractual Life (Years), Options outstanding, December 31	3 years 1 month 24 days
Grant Date 3-8-2016
Options outstanding, December 31	26,667
Weighted Average Exercise Price, Options outstanding, December 31	$ 63.63
Weighted Average Remaining Contractual Life (Years), Options outstanding, December 31	3 years 2 months 8 days
Grant Date 2-22-2017
Options outstanding, December 31	453,335
Weighted Average Exercise Price, Options outstanding, December 31	$ 74.78
Weighted Average Remaining Contractual Life (Years), Options outstanding, December 31	4 years 1 month 24 days
Grant Date 9-1-2017
Options outstanding, December 31	10,000
Weighted Average Exercise Price, Options outstanding, December 31	$ 80.55
Weighted Average Remaining Contractual Life (Years), Options outstanding, December 31	4 years 8 months 5 days