XML 97 R83.htm IDEA: XBRL DOCUMENT v3.8.0.1
Federal Income Taxes - Reconciliation of the Statutory Federal Income Tax Rate to the Effective Tax Rate (Detail) - USD ($)
$ in Thousands
3 Months Ended 12 Months Ended
Dec. 31, 2017
Sep. 30, 2017
Jun. 30, 2017
Mar. 31, 2017
Dec. 31, 2016
Sep. 30, 2016
Jun. 30, 2016
Mar. 31, 2016
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Effective Income Tax Rate Reconciliation, Amount [Abstract]                      
Income tax at statutory rates                 $ 6,045 $ 5,521 $ 4,792
Decrease resulting from:                      
Tax exempt interest                 (413) (468) (554)
Adjustment of deferred taxes for enacted changes in tax law                 (8)    
Section 831 deduction                 (318) (351) (351)
Change in other                 (123) (46) (68)
Total $ 1,583 $ 1,159 $ 1,298 $ 1,143 $ 1,307 $ 1,161 $ 1,254 $ 934 $ 5,183 $ 4,656 $ 3,819