Earnings Per Share (Computation Of Basic Earnings And Diluted Earnings Per Share Data) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	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, 2010	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Earnings Per Share [Abstract]
Numerator for basic and diluted earnings per share Net income	$ 9,376	$ 10,832	$ 7,105	$ 5,681	$ 8,699	$ 7,506	$ 5,624	$ 5,728	$ 32,994	$ 27,557	$ 25,054
Weighted-average basic common shares outstanding									30,327,000	31,267,000	34,075,000
Stock options									2,589,000	1,887,000	1,453,000
Denominator for diluted earnings per share - Adjusted weighted-average shares	33,421,000	32,986,000	32,769,000	32,530,000	32,031,000	32,960,000	33,848,000	33,720,000	32,916,000	33,154,000	35,528,000
Basic									$ 1.09	$ 0.88	$ 0.74
Diluted	$ 0.28	$ 0.33	$ 0.22	$ 0.17	$ 0.27	$ 0.23	$ 0.17	$ 0.17	$ 1.00	$ 0.83	$ 0.71
Antidilutive securities excluded from computation of earnings per share, amount									463,000	714,000	1,800,000