Share-Based Compensation (Schedule Of Stock Option Activity) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Options outstanding, January 1	741,676	871,671	516,674
Options outstanding, December 31	541,679	741,676	871,671
Options exercisable, December 31	188,331
Weighted Average Exercise Price, Options outstanding, January 1	$ 65.84	$ 60.43	$ 59.20
Weighted Average Exercise Price, Options outstanding, December 31	63.73	$ 65.84	$ 60.43
Weighted Average Exercise Price, Options exercisable, December 31	$ 63.56
Weighted Average Remaining Contractual Life (Years), Options outstanding, December 31	3 years 5 months 10 days
Weighted Average Remaining Contractual Life (Years), Options exercisable, December 31	2 years 7 months 9 days
Aggregate Intrinsic Value, Options outstanding, December 31	$ 5,657
Aggregate Intrinsic Value, Options exercisable, December 31	$ 1,998
2005 Plan [Member]
Options granted		20,000
Options exercised	(61,666)	(66,670)	(26,670)
Options forfeited			(15,000)
Weighted Average Exercise Price, Options granted		$ 72.11
Weighted Average Exercise Price, Options exercised	$ 52.36	$ 46.87	$ 47.52
Weighted Average Exercise Price, Options forfeited			$ 64.49
2012 Plan [Member]
Options granted	470,000	450,000	400,000
Options exercised	(608,331)	(421,657)	(3,333)
Options forfeited		(111,668)
Weighted Average Exercise Price, Options granted	$ 60.78	$ 72.11	$ 61.31
Weighted Average Exercise Price, Options exercised	$ 65.18	63.03	$ 61.31
Weighted Average Exercise Price, Options forfeited		$ 71.95
Grant Date 2-21-2012 [Member]
Options outstanding, December 31	15,000
Weighted Average Exercise Price, Options outstanding, December 31	$ 47.52
Weighted Average Remaining Contractual Life (Years), Options outstanding, December 31	1 month 22 days
Grant Date 2-25-2013 [Member]
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 year 1 month 26 days
Grant Date 2-25-2014 [Member]
Options outstanding, December 31	65,000
Weighted Average Exercise Price, Options outstanding, December 31	$ 61.31
Weighted Average Remaining Contractual Life (Years), Options outstanding, December 31	2 years 1 month 26 days
Grant Date 2-20-2015 [Member]
Options outstanding, December 31	150,007
Weighted Average Exercise Price, Options outstanding, December 31	$ 72.11
Weighted Average Remaining Contractual Life (Years), Options outstanding, December 31	3 years 1 month 21 days
Grant Date 2-22-2016 [Member]
Options outstanding, December 31	270,005
Weighted Average Exercise Price, Options outstanding, December 31	$ 60.52
Weighted Average Remaining Contractual Life (Years), Options outstanding, December 31	4 years 1 month 24 days
Grant Date 3-8-2016 [Member]
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	4 years 2 months 8 days