Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Basic
Net income	$ 5,962	$ 5,739	$ 11,870	$ 11,458
Weighted-average common shares outstanding (in shares)	10,330,961	10,296,796	10,333,308	10,294,563
Basic earnings per share (in dollars per share)	$ 0.58	$ 0.56	$ 1.15	$ 1.11
Diluted
Net income	$ 5,962	$ 5,739	$ 11,870	$ 11,458
Weighted-average common shares outstanding (in shares)	10,330,961	10,296,796	10,333,308	10,294,563
Effect of dilutive restricted stock, stock options and stock appreciation rights (in shares)	167,057	142,314	163,345	140,923
Weighted-average common shares outstanding assuming dilution (in shares)	10,498,018	10,439,110	10,496,653	10,435,486
Diluted earnings per share (in dollars per share)	$ 0.57	$ 0.55	$ 1.13	$ 1.10