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, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Earnings Per Share [Abstract]
Net Income, Earnings	$ 20,845	$ 21,887	$ 62,564	$ 60,274
Net Income, Earnings, Shares	18,960,000	20,674,000	18,977,000	20,934,000
Net Income, Earnings per Share	$ 1.10	$ 1.06	$ 3.30	$ 2.88
Dilutive stock options, Shares	341,000	293,000	313,000	379,000
Nonvested stock awards, Shares	103,000	88,000	92,000	87,000
Net Income, Diluted Earnings, Shares	19,404,000	21,055,000	19,382,000	21,400,000
Net Income, Diluted Earnings per Share	$ 1.07	$ 1.04	$ 3.23	$ 2.82
Stock options excluded from computation of earnings per share	1,400,000	1,500,000	1,400,000	980,000