Earnings Per Share (Schedule Of Computation Of Earnings Per Share) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Earnings Per Share [Abstract]
Net Income, Earnings	$ 22,278	$ 20,445
Net Income, Earnings, Shares	18,522,000	18,958,000
Net Income, Earnings per Share	$ 1.20	$ 1.08
Dilutive stock options, Shares	371,000	304,000
Nonvested stock awards, Shares	107,000	91,000
Net Income, Diluted Earnings, Shares	19,000,000	19,353,000
Net Income, Diluted Earnings per Share	$ 1.17	$ 1.06
Stock options excluded from computation of earnings per share	11,000	1,400,000