Earnings Per Share (Earnings And Diluted Earnings Per Share) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Earnings Per Share [Abstract]
Earnings	$ 21,887	$ 20,988	$ 60,274	$ 59,201
Earnings per share, basic	$ 1.06	$ 0.93	$ 2.88	$ 2.62
Earnings per share, diluted	$ 1.04	$ 0.91	$ 2.82	$ 2.57
Average number of shares outstanding, basic	20,674,000	22,597,000	20,934,000	22,604,000
Average number of shares outstanding, diluted	21,055,000	22,996,000	21,400,000	23,006,000
Dilutive stock options	293,000	304,000	379,000	314,000
Nonvested stock awards	88,000	95,000	87,000	88,000
Stock options excluded from computation of earnings per share	1,500,000	990,000	980,000	986,000
Percent of senior convertible notes			1.875%