Quarterly report pursuant to Section 13 or 15(d)

Accumulated Other Comprehensive Income - Additional Information (Detail)

v3.10.0.1
Accumulated Other Comprehensive Income - Additional Information (Detail) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jan. 01, 2018
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Accumulated Other Comprehensive Income [Line Items]          
Net gain (loss) on sales of securities   $ 67 $ 938 $ (361) $ 1,206
Net unrealized gains (losses) recorded in comprehensive income   95 430 95 744
Accumulated Net Unrealized Investment Gain (Loss) [Member]          
Accumulated Other Comprehensive Income [Line Items]          
Reduction of unrealized losses related to securities $ 529     529  
AOCI Attributable to Parent [Member]          
Accumulated Other Comprehensive Income [Line Items]          
Adjustment to accumulated other comprehensive income related to adoption of ASU 2016-01 and 2018-02, net of tax 17     17  
Tax Expense Benefit [Member]          
Accumulated Other Comprehensive Income [Line Items]          
Reduction in tax benefits upon adoption of ASUs $ 546     546  
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]          
Accumulated Other Comprehensive Income [Line Items]          
Net gain (loss) on sales of securities   $ 67 $ 938 $ 67 $ 1,200