Earnings Per Share (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended						6 Months Ended
	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Jun. 30, 2012	Jun. 30, 2011
Computation of Earnings per Share
Net income	$ 5,321	$ 3,931	$ 6,549	$ 6,470	$ 2,771	$ 2,800	$ 9,252	$ 5,571
Average number of common shares outstanding	15,986				15,922		15,982	15,891
Effect of dilutive stock options	61				32		63	98
Average diluted common shares outstanding	16,047				15,954		16,045	15,989
Options excluded from diluted earnings per share because the effect of these options was antidilutive	1,020				826		944	795