Earnings Per Share (Schedule Of Earnings Per Share) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Earnings Per Share [Abstract]
Income of basic earnings per common share	$ 40,206	$ 52,439
Income of effect of dilutive stock options, restricted stock and stock appreciation rights (SARs)	0	0
Income of diluted earnings per common share	$ 40,206	$ 52,439
Weighted shares of basic earnings per common share	48,117	47,829
Weighted shares of effect of dilutive stock options, restricted stock and stock appreciation rights (SARs)	295	297
Weighted shares of diluted earnings per common share	48,412	48,126
Per-Share amount of basic earnings per common share	$ 0.84	$ 1.10
Per-Share amount of effect of dilutive stock options, restricted stock and stock appreciation rights (SARs)	$ (0.01)	$ (0.01)
Per-Share amount of diluted earnings per common share	$ 0.83	$ 1.09