Earnings Per Share (Schedule Of Earnings Per Share) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended									12 Months Ended
	Dec. 31, 2014		Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Earnings Per Share [Abstract]
Income of basic earnings per common share	$ (42,551)		$ 67,522	$ 54,360	$ 56,945	$ 51,301	$ 34,232	$ 59,007	$ 40,206	$ 136,276	$ 184,746	$ 23,176
Income of effect of dilutive stock options, restricted stock, and SARs										0	0	0
Income of diluted earnings per common share										$ 136,276	$ 184,746	$ 23,176
Weighted shares of basic earnings per common share										48,611	48,218	47,909
Weighted shares of effect of dilutive stock options, restricted stock, and SARs										472	354	245
Weighted shares of diluted earnings per common share										49,083	48,572	48,154
Per share amount of basic earnings per common share	$ (0.88)		$ 1.39	$ 1.12	$ 1.17	$ 1.06	$ 0.71	$ 1.22	$ 0.84	$ 2.80	$ 3.83	$ 0.48
Per share amount of effect of dilutive stock options, restricted stock, and SARs										$ (0.02)	$ (0.03)	$ 0.00
Per share amount of diluted earnings per common share	$ (0.88)	[1]	$ 1.37	$ 1.11	$ 1.17	$ 1.05	$ 0.70	$ 1.22	$ 0.83	$ 2.78	$ 3.80	$ 0.48

[1] Due to the effect of the loss in the fourth quarter, the diluted earnings per share for the year's four quarters does not equal annual earnings per share.