Earnings Per Share (Schedule Of Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Earnings Per Share [Abstract]
Income (loss) of basic earnings (loss) per common share	$ (205,281)	$ 67,522	$ (728,024)	$ 178,827
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	$ (205,281)	$ 67,522	$ (728,024)	$ 178,827
Weighted shares of basic earnings (loss) per common share	49,155	48,650	49,094	48,596
Weighted shares of effect of dilutive stock options, restricted stock, and stock appreciation rights (SARs)	0	527	0	458
Weighted shares of diluted earnings (loss) per common share	49,155	49,177	49,094	49,054
Per-Share amount of basic earnings (loss) per common share	$ (4.18)	$ 1.39	$ (14.83)	$ 3.68
Per-Share amount of effect of dilutive stock options, restricted stock, and stock appreciation rights (SARs)	0.00	(0.02)	0.00	(0.03)
Per-Share amount of diluted earnings (loss) per common share	$ (4.18)	$ 1.37	$ (14.83)	$ 3.65