XML 65 R51.htm IDEA: XBRL DOCUMENT v3.8.0.1
Securities - Gross Unrealized Losses, Aggregated by Investment Category and Length of Time (Detail) - USD ($)
$ in Thousands
Dec. 31, 2017
Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Losses, Less Than Twelve Months $ (625) $ (3,803)
Fair Value, Less Than Twelve Months 66,400 167,230
Gross Unrealized Losses, Twelve Months and Over (2,643) (7)
Fair Value, Twelve Months and Over 106,840 526
U.S. Treasury [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Losses, Less Than Twelve Months (36) (146)
Fair Value, Less Than Twelve Months 6,924 15,745
Gross Unrealized Losses, Twelve Months and Over (205)  
Fair Value, Twelve Months and Over 14,054  
U.S. Government Agencies [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Losses, Less Than Twelve Months (314) (1,795)
Fair Value, Less Than Twelve Months 27,328 77,471
Gross Unrealized Losses, Twelve Months and Over (1,418)  
Fair Value, Twelve Months and Over 53,139  
Mortgage-backed Securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Losses, Less Than Twelve Months (70) (879)
Fair Value, Less Than Twelve Months 7,149 36,474
Gross Unrealized Losses, Twelve Months and Over (720)  
Fair Value, Twelve Months and Over 28,080  
State and Local Governments [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Losses, Less Than Twelve Months (205) (983)
Fair Value, Less Than Twelve Months 24,999 37,540
Gross Unrealized Losses, Twelve Months and Over (300) (7)
Fair Value, Twelve Months and Over $ 11,567 $ 526