Earnings Per Share (Schedule Of Earnings Per Share) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Earnings Per Share [Abstract]
Income of basic earnings per common share	$ 54,360	$ 59,007	$ 111,305	$ 99,213
Income of effect of dilutive stock options, restricted stock, and stock appreciation rights (SARs)	0	0	0	0
Income of diluted earnings per common share	$ 54,360	$ 59,007	$ 111,305	$ 99,213
Weighted shares of basic earnings per common share	48,642	48,208	48,568	48,162
Weighted shares of effect of dilutive stock options, restricted stock, and stock appreciation rights (SARs)	474	298	442	329
Weighted shares of diluted earnings per common share	49,116	48,506	49,010	48,491
Per-Share amount of basic earnings per common share	$ 1.12	$ 1.22	$ 2.29	$ 2.06
Per-Share amount of effect of dilutive stock options, restricted stock, and stock appreciation rights (SARs)	$ (0.01)	$ 0.00	$ (0.02)	$ (0.01)
Per-Share amount of diluted earnings per common share	$ 1.11	$ 1.22	$ 2.27	$ 2.05