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, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Earnings Per Share [Abstract]
Numerator for basic and diluted earnings per share Net income	$ 8,699	$ 7,506	$ 5,624	$ 5,728	$ 7,210	$ 6,723	$ 6,249	$ 4,872	$ 27,557	$ 25,054	$ 27,010
Weighted-average basic common shares outstanding									31,267,000	34,075,000	35,240,000
Stock options									1,887,000	1,453,000	1,384,000
Denominator for diluted earnings per share - Adjusted weighted-average shares	32,031,000	32,960,000	33,848,000	33,720,000	33,895,000	35,410,000	36,203,000	36,655,000	33,154,000	35,528,000	36,624,000
Basic									$ 0.88	$ 0.74	$ 0.77
Diluted	$ 0.27	$ 0.23	$ 0.17	$ 0.17	$ 0.21	$ 0.19	$ 0.17	$ 0.13	$ 0.83	$ 0.71	$ 0.74
Antidilutive securities excluded from computation of earnings per share, amount									714,000	1,800,000	2,600,000