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, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012		Sep. 30, 2012		Jun. 30, 2012		Mar. 31, 2012		Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Earnings Per Share [Abstract]
Income of basic earnings per common share	$ 51,301	$ 34,232	$ 59,007	$ 40,206	$ (56,547)		$ 46,586		$ (19,302)		$ 52,439		$ 184,746	$ 23,176	$ 195,867
Income of effect of dilutive stock options, restricted stock, and SARs													0	0	0
Income of diluted earnings per common share													$ 184,746	$ 23,176	$ 195,867
Weighted shares of basic earnings per common share													48,218	47,909	47,658
Weighted shares of effect of dilutive stock options, restricted stock, and SARs													354	245	293
Weighted shares of diluted earnings per common share													48,572	48,154	47,951
Per share amount of basic earnings per common share	$ 1.06	$ 0.71	$ 1.22	$ 0.84	$ (1.18)	[1]	$ 0.97	[1]	$ (0.40)	[1]	$ 1.10	[1]	$ 3.83	$ 0.48	$ 4.11
Per share amount of effect of dilutive stock options, restricted stock, and SARs													$ (0.03)	$ 0.00	$ (0.03)
Per share amount of diluted earnings per common share	$ 1.05	$ 0.70	$ 1.22	$ 0.83	$ (1.18)		$ 0.97		$ (0.40)		$ 1.09		$ 3.80	$ 0.48	$ 4.08

[1] Due to the effect of rounding the basic earnings per share for the year’s four quarters does not equal annual earnings per share.