Quarterly report pursuant to Section 13 or 15(d)

Accumulated Other Comprehensive Income - Additional Information (Detail)

v3.8.0.1
Accumulated Other Comprehensive Income - Additional Information (Detail) - USD ($)
$ in Thousands
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Accumulated Other Comprehensive Income [Line Items]    
Net (loss) gain on sales of securities $ (428) $ 269
Net unrealized gains (losses) recorded in comprehensive income (529) 319
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]    
Accumulated Other Comprehensive Income [Line Items]    
Net (loss) gain on sales of securities   $ 269
ASU 2016-01 [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]    
Accumulated Other Comprehensive Income [Line Items]    
Reduction of unrealized losses related to securities 529  
ASU 2016-01 and ASU 2018-02 [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]    
Accumulated Other Comprehensive Income [Line Items]    
Net (loss) gain on sales of securities 17  
Reduction in tax benefits upon adoption of ASUs $ 546