Summary Of Significant Accounting Policies (Schedule Of Calculation Of Basic And Diluted 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, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Summary Of Significant Accounting Policies [Abstract]
Net income	$ 67,489	$ 23,726	$ 8,457	$ 11,487	$ 18,115	$ 19,314	$ 13,580	$ 5,598	$ 2,878	$ 19,867	$ 14,701	$ 14,513	$ 111,159	$ 56,607	$ 51,959
Denominator for basic earnings per share - weighted-average number of common shares outstanding during the period													54,213	56,320	59,284
Incremental common shares attributable to outstanding dilutive options													324	150	270
Incremental common shares attributable to outstanding restricted shares, restricted stock units and phantom stock													242	164	219
Denominator for diluted earnings per share													54,779	56,634	59,773
Basic earnings per share	$ 1.26	$ 0.44	$ 0.16	$ 0.21	$ 0.33	$ 0.35	$ 0.24	$ 0.10	$ 0.05	$ 0.34	$ 0.24	$ 0.24	$ 2.05	$ 1.01	$ 0.88
Diluted earnings per share	$ 1.24	$ 0.43	$ 0.16	$ 0.21	$ 0.33	$ 0.34	$ 0.24	$ 0.10	$ 0.05	$ 0.34	$ 0.24	$ 0.24	$ 2.03	$ 1.00	$ 0.87