Summarized Consolidated Quarterly Financial Data (Unaudited) (Details) - USD ($)
$ / shares in Units, $ in Thousands
 3 Months Ended 12 Months Ended
Dec. 31, 2015
Sep. 30, 2015
Jun. 30, 2015
Mar. 31, 2015
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, 2015
Dec. 31, 2014
Dec. 31, 2013
Quarterly Financial Data [Abstract]                              
Total interest income $ 9,464 $ 9,358 $ 9,221 $ 9,154 $ 9,606 $ 9,736 $ 9,695 $ 9,652 $ 9,768 $ 9,549 $ 9,684 $ 9,538 $ 37,197 $ 38,689 $ 38,539
Total interest expense 1,772 1,694 1,653 1,632 1,609 1,517 1,517 1,598 1,694 1,804 1,879 2,149 6,751 6,241 7,526
Net interest income 7,692 7,664 7,568 7,522 7,997 8,219 8,178 8,054 8,074 7,745 7,805 7,389 30,446 32,448 31,013
Recapture of provision for loan losses (900) (700) (500) (100) (1,200) (300) (100) (500) (200) 0 100 0 (2,200) (2,100) (100)
Net interest income after recapture of provision for loan losses 8,592 8,364 8,068 7,622 9,197 8,519 8,278 8,554 8,274 7,745 7,705 7,389 32,646 34,548 31,113
Total noninterest income 384 447 357 91 156 186 88 68 512 120 155 104 1,279 498 891
Total noninterest expense 5,333 5,381 4,874 4,290 4,769 4,508 4,702 4,524 4,510 5,388 5,306 5,878 19,878 18,503 21,082
Income before provision for income taxes 3,643 3,430 3,551 3,423 4,584 4,197 3,664 4,098 4,276 2,477 2,554 1,615 14,047 16,543 10,922
Provision for federal income tax expense 1,526 984 1,183 1,194 1,644 1,462 1,297 1,453 342 (135) (13,809) 59 4,887 5,856 (13,543)
Net income $ 2,117 $ 2,446 $ 2,368 $ 2,229 $ 2,940 $ 2,735 $ 2,367 $ 2,645 $ 3,934 $ 2,612 $ 16,363 $ 1,556 $ 9,160 $ 10,687 $ 24,465
Basic earnings (loss) per share (usd per share) $ 0.16 $ 0.18 $ 0.17 $ 0.16 $ 0.20 $ 0.19 $ 0.16 $ 0.17 $ 0.25 $ 0.16 $ 0.96 $ 0.09 $ 0.67 $ 0.72 $ 1.47
Diluted earnings (loss) per share (usd per share) $ 0.16 $ 0.18 $ 0.17 $ 0.16 $ 0.20 $ 0.19 $ 0.16 $ 0.17 $ 0.25 $ 0.16 $ 0.95 $ 0.09 $ 0.67 $ 0.71 $ 1.46