Net Income Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Summary of net income per share
Net income	$ 3,934	$ 3,964	$ 11,400	$ 11,909
Weighted-average common shares outstanding	14,362,000	14,490,000	14,329,000	14,456,000
Basic earnings per share	$ 0.27	$ 0.27	$ 0.80	$ 0.82
Weighted-average common shares outstanding	14,362,375	14,489,740	14,329,149	14,455,677
Common stock equivalents due to effect of stock options	128,000	100,000	129,000	111,000
Total weighted-average common shares and equivalents	14,490,000	14,590,000	14,458,000	14,567,000
Diluted earnings per share	$ 0.27	$ 0.27	$ 0.79	$ 0.82