Earnings Per Share (Schedule Of Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Earnings Per Share [Abstract]
Income (loss) of basic earnings (loss) per common share	$ (274,389)	$ 54,360	$ (522,743)	$ 111,305
Income of effect of dilutive stock options, restricted stock, and stock appreciation rights (SARs)	0	0	0	0
Income (loss) of diluted earnings (loss) per common share	$ (274,389)	$ 54,360	$ (522,743)	$ 111,305
Weighted shares of basic earnings (loss) per common share	49,148	48,642	49,063	48,568
Weighted shares of effect of dilutive stock options, restricted stock, and stock appreciation rights (SARs)	0	474	0	442
Weighted shares of diluted earnings (loss) per common share	49,148	49,116	49,063	49,010
Per-Share amount of basic earnings (loss) per common share	$ (5.58)	$ 1.12	$ (10.66)	$ 2.29
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 (loss) per common share	$ (5.58)	$ 1.11	$ (10.66)	$ 2.27