Summarized Consolidated Quarterly Financial Data (Unaudited) (Details) - USD ($)
$ / shares in Units, $ in Thousands
 3 Months Ended 12 Months Ended
Dec. 31, 2016
Sep. 30, 2016
Jun. 30, 2016
Mar. 31, 2016
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, 2016
Dec. 31, 2015
Dec. 31, 2014
Quarterly Financial Data [Abstract]                              
Total interest income $ 11,409 $ 10,842 $ 9,896 $ 9,562 $ 9,464 $ 9,358 $ 9,221 $ 9,154 $ 9,606 $ 9,736 $ 9,695 $ 9,652 $ 41,709 $ 37,197 $ 38,689
Total interest expense 2,105 1,908 1,713 1,781 1,772 1,694 1,653 1,632 1,609 1,517 1,517 1,598 7,507 6,751 6,241
Net interest income 9,304 8,934 8,183 7,781 7,692 7,664 7,568 7,522 7,997 8,219 8,178 8,054 34,202 30,446 32,448
(Recapture of provision) provision for loan losses (100) 900 600 (100) (900) (700) (500) (100) (1,200) (300) (100) (500) 1,300 (2,200) (2,100)
Net interest income after recapture of provision for loan losses 9,404 8,034 7,583 7,881 8,592 8,364 8,068 7,622 9,197 8,519 8,278 8,554 32,902 32,646 34,548
Total noninterest income 790 673 708 480 384 447 357 91 156 186 88 68 2,651 1,279 498
Total noninterest expense 5,850 5,254 6,072 5,773 5,333 5,381 4,874 4,290 4,769 4,508 4,702 4,524 22,949 19,878 18,503
Income before provision for income taxes 4,344 3,453 2,219 2,588 3,643 3,430 3,551 3,423 4,584 4,197 3,664 4,098 12,604 14,047 16,543
Provision for federal income tax expense 1,323 847 779 763 1,526 984 1,183 1,194 1,644 1,462 1,297 1,453 3,712 4,887 5,856
Net income $ 3,021 $ 2,606 $ 1,440 $ 1,825 $ 2,117 $ 2,446 $ 2,368 $ 2,229 $ 2,940 $ 2,735 $ 2,367 $ 2,645 $ 8,892 $ 9,160 $ 10,687
Basic earnings (loss) per share (usd per share) $ 0.29 $ 0.22 $ 0.12 $ 0.14 $ 0.16 $ 0.18 $ 0.17 $ 0.16 $ 0.20 $ 0.19 $ 0.16 $ 0.17 $ 0.75 $ 0.67 $ 0.72
Diluted earnings (loss) per share (usd per share) $ 0.29 $ 0.22 $ 0.11 $ 0.14 $ 0.16 $ 0.18 $ 0.17 $ 0.16 $ 0.20 $ 0.19 $ 0.16 $ 0.17 $ 0.74 $ 0.67 $ 0.71