Earnings Per Share (Schedule Of Computation Of Earnings Per Share) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Earnings Per Share [Abstract]
Net Income, Earnings	$ 17,432	$ 20,845	$ 54,318	$ 62,564
Net Income, Earnings, Shares	18,184,000	18,960,000	18,436,000	18,977,000
Net Income, Earnings per Share	$ 0.96	$ 1.10	$ 2.95	$ 3.30
Dilutive stock options, Shares	235,000	341,000	287,000	313,000
Nonvested stock awards, Shares	103,000	103,000	101,000	92,000
Net Income, Diluted Earnings, Shares	18,522,000	19,404,000	18,824,000	19,382,000
Net Income, Diluted Earnings per Share	$ 0.94	$ 1.07	$ 2.89	$ 3.23
Stock options excluded from computation of earnings per share	434,000	1,400,000	31,000	1,400,000