Quarterly report pursuant to Section 13 or 15(d)

Accumulated Other Comprehensive Income - Activity in Accumulated Other Comprehensive Income (Detail)

v3.8.0.1
Accumulated Other Comprehensive Income - Activity in Accumulated Other Comprehensive Income (Detail) - USD ($)
$ in Thousands
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]    
AOCI before Tax, Attributable to Parent $ (11,523) $ (2,738)
Balance at beginning of period 562,477 531,025
OCI, before Reclassifications, Net of Tax, Attributable to Parent (6,321) 1,060
Reclassification from AOCI, Current Period, Net of Tax, Attributable to Parent (17) (269)
Change in unrealized gain (loss) on securities available for sale, net of income taxes (6,338)  
Change in unrealized gain (loss) on securities available for sale, net of income taxes (6,321) 791
Balance at end of period 564,278 539,542
Accumulated Net Unrealized Investment Gain (Loss) [Member]    
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]    
AOCI before Tax, Attributable to Parent (3,188) (4,089)
OCI, before Reclassifications, before Tax, Attributable to Parent (8,864) 1,620
Reclassification from AOCI, Current Period, before Tax, Attributable to Parent 529 (269)
Other Comprehensive Income (Loss), before Tax, Portion Attributable to Parent (8,335) 1,351
Tax Expense Benefit [Member]    
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]    
AOCI Tax, Attributable to Parent 1,319 1,695
Other comprehensive (loss) income before reclassification, tax 2,543 (560)
Reclassification from accumulated other comprehensive income, tax (546) 0
Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent 1,997 (560)
AOCI Tax, Attributable to Parent 3,316 1,135
AOCI Attributable to Parent [Member]    
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]    
Balance at beginning of period (1,869) (2,394)
Change in unrealized gain (loss) on securities available for sale, net of income taxes (6,321) 791
Balance at end of period $ (8,207) $ (1,603)