Earnings Per Share (Schedule Of Earnings Per Share) (Details) (USD $) In Thousands, except Per 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]
Income of Basic earnings per common share	$ 46,586	$ 53,360	$ 79,723	$ 144,206
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	$ 46,586	$ 53,360	$ 79,723	$ 144,206
Weighted Shares of Basic earnings per common share	47,938	47,687	47,891	47,642
Weighted Shares of Effect of dilutive stock options, restricted stock and stock appreciation rights (SARs)	263	281	215	290
Weighted Shares of Diluted earnings per common share	48,201	47,968	48,106	47,932
Per-Share Amount of Basic earnings per common share	$ 0.97	$ 1.12	$ 1.66	$ 3.03
Per-Share Amount of Effect of dilutive stock options, restricted stock and stock appreciation rights (SARs)	$ 0.00	$ (0.01)	$ 0.00	$ (0.02)
Per-Share Amount of Diluted earnings per common share	$ 0.97	$ 1.11	$ 1.66	$ 3.01