Fair Value Measurements - Financial Instruments Measured at Fair Value on a Recurring and Non-recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	$ 448,390	$ 464,245
Fair Value Measurements, Level 1 Inputs [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	296	286
Fair Value Measurements, Level 2 Inputs [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	351,208	427,362
Fair Value Measurements, Level 3 Inputs [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	96,886	36,597
U.S. Treasury [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	2,000	1,998
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	1,998
U.S. Government Sponsored Enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS		10,004
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		10,004
SBA Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	6,717	7,302
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	6,717	7,302
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	337,093	403,190
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	337,093	403,189
Privately Issued Residential Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	1,874	2,277
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	1,874	2,277
Obligations Issued by States and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	96,784	36,723
Obligations Issued by States and Political Subdivisions [Member] | Fair Value Measurements, Level 2 Inputs [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS		416
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	96,784	36,307
Other Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	3,524	2,175
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	3,524	2,176
Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	398	576
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	296	286
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	102	290
Impaired Loans [Member] | Fair Value Measurements, Level 3 Inputs [Member]
Financial Instruments Measured at Fair Value on a Non-recurring Basis
Impaired Loans	3,410	1,747
Carrying Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	448,390	464,245
Carrying Value [Member] | U.S. Treasury [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	2,000	1,998
Carrying Value [Member] | U.S. Government Sponsored Enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS		10,004
Carrying Value [Member] | SBA Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	6,717	7,302
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	337,093	403,189
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	1,874	2,277
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	96,784	36,723
Carrying Value [Member] | Other Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	3,524	2,176
Carrying Value [Member] | Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	398	576
Carrying Value [Member] | Impaired Loans [Member]
Financial Instruments Measured at Fair Value on a Non-recurring Basis
Impaired Loans	$ 3,410	$ 1,747