Quarterly Results of Operations (Unaudited) (Details) (USD $)
In Thousands, except Per Share data, unless otherwise specified
 3 Months Ended 12 Months Ended
Dec. 31, 2014
Sep. 30, 2014
Jun. 30, 2014
Mar. 31, 2014
Dec. 31, 2013
Sep. 30, 2013
Jun. 30, 2013
Mar. 31, 2013
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Quarterly Financial Information Disclosure [Abstract]                      
Interest income $ 22,317 $ 22,422 $ 22,289 $ 21,393 $ 21,419 $ 21,891 $ 22,481 $ 22,426 $ 88,421 $ 88,217 $ 90,947
Interest expense 3,056 3,048 3,041 2,983 3,069 3,184 3,231 3,258 12,128 12,742 17,202
Net interest income 19,261 19,374 19,248 18,410 18,350 18,707 19,250 19,168 76,293 75,475 73,745
Provision for credit losses 545 539 643 493 (6) 665 695 674 2,220 2,028 3,816
Non-interest income 6,196 5,949 6,504 5,685 8,614 6,475 6,376 6,336 24,334 27,801 23,412
Non-interest expense 16,301 15,179 15,792 15,125 18,986 15,199 15,648 16,500 62,397 66,333 59,031
Income before income tax 8,611 9,605 9,317 8,477 7,984 9,318 9,283 8,330 36,010 34,915 34,310
Income tax expense 2,523 3,154 3,001 2,762 3,560 2,952 2,952 2,668 11,440 12,132 10,882
Net income $ 6,088 $ 6,451 $ 6,316 $ 5,715 $ 4,424 $ 6,366 $ 6,331 $ 5,662 $ 24,570 $ 22,783 $ 23,428
Per common share:                      
Basic earnings per share $ 0.82 $ 0.87 $ 0.85 $ 0.76 $ 0.58 $ 0.83 $ 0.83 $ 0.74 $ 3.29 $ 2.98 $ 3.06
Diluted earnings per share $ 0.82 $ 0.86 $ 0.85 $ 0.75 $ 0.58 $ 0.83 $ 0.82 $ 0.74 $ 3.28 $ 2.97 $ 3.05