Earnings Per Share (Reconciliation Of Denominator For Basic And Diluted Earnings (Loss) Per Share) (Details) (USD $)	3 Months Ended																12 Months Ended
	Dec. 31, 2012		Sep. 30, 2012		Jun. 30, 2012		Mar. 31, 2012		Dec. 31, 2011		Sep. 30, 2011		Jun. 30, 2011		Mar. 31, 2011		Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Earnings Per Share [Abstract]
Weighted average common shares - basic																	66,289,429	65,927,421	65,472,875
Plus incremental shares from: Assumed exercise of options																	352,066	372,737	203,789
Weighted average common shares - diluted																	66,641,495	66,300,158	65,676,664
Basic	$ 1.43	[1]	$ 1.30	[1]	$ 1.73	[1]	$ 1.32	[1]	$ 0.40	[1]	$ 1.02	[1]	$ 1.22	[1]	$ 1.26	[1]	$ 5.78	$ 3.89	$ 3.35
Diluted	$ 1.42	[1]	$ 1.30	[1]	$ 1.72	[1]	$ 1.31	[1]	$ 0.40	[1]	$ 1.01	[1]	$ 1.21	[1]	$ 1.25	[1]	$ 5.75	$ 3.87	$ 3.34

[1] Basic and diluted earnings per common share ("EPS") for each quarter is computed using the weighted average shares outstanding during that quarter, while EPS for the year is computed using the weighted average shares outstanding for the year. As a result, the sum of the EPS for each of the four quarters may not equal the EPS for the year.