Fair Value Measurements - Financial Instruments Measured at Fair Value on a Recurring and Non-recurring Basis (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	$ 526,132	$ 404,623
Fair Value Measurements, Level 1 Inputs [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	275	215
Fair Value Measurements, Level 2 Inputs [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	345,946	247,411
Fair Value Measurements, Level 3 Inputs [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	179,911	156,997
Financial Instruments Measured at Fair Value on a Non-recurring Basis
Impaired Loans	251	1,056
U.S. Treasury [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	2,000	1,989
U.S. Treasury [Member] | Fair Value Measurements, Level 2 Inputs [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	2,000	1,989
SBA Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	58,345	5,989
SBA Backed Securities [Member] | Fair Value Measurements, Level 2 Inputs [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	58,345	5,989
U.S. Government Agency and Sponsored Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	264,454	233,526
U.S. Government Agency and Sponsored Mortgage Backed Securities [Member] | Fair Value Measurements, Level 2 Inputs [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	264,454	233,526
Privately Issued Residential Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	1,177	1,434
Privately Issued Residential Mortgage Backed Securities [Member] | Fair Value Measurements, Level 2 Inputs [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	1,177	1,434
Obligations Issued by States and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	179,911	156,960
Obligations Issued by States and Political Subdivisions [Member] | Fair Value Measurements, Level 3 Inputs [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	179,911	156,960
Other Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	4,961	4,473
Other Debt Securities [Member] | Fair Value Measurements, Level 2 Inputs [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	4,961	4,473
Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	275	252
Equity Securities [Member] | Fair Value Measurements, Level 1 Inputs [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	275	215
Equity Securities [Member] | Fair Value Measurements, Level 3 Inputs [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS		37
U.S. Government Sponsored Enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	15,009
U.S. Government Sponsored Enterprises [Member] | Fair Value Measurements, Level 2 Inputs [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	15,009
Carrying Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	526,132	404,623
Financial Instruments Measured at Fair Value on a Non-recurring Basis
Impaired Loans	251	1,056
Carrying Value [Member] | U.S. Treasury [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	2,000	1,989
Carrying Value [Member] | SBA Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	58,345	5,989
Carrying Value [Member] | U.S. Government Agency and Sponsored Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	264,454	233,526
Carrying Value [Member] | Privately Issued Residential Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	1,177	1,434
Carrying Value [Member] | Obligations Issued by States and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	179,911	156,960
Carrying Value [Member] | Other Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	4,961	4,473
Carrying Value [Member] | Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	275	$ 252
Carrying Value [Member] | U.S. Government Sponsored Enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	$ 15,009