Loans and Loans Held for Sale - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014 SecurityLoan TDRs Property	Dec. 31, 2013 TDRs
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unearned Income On Loan	$ 2,100,000	$ 1,300,000
Percentage of commercial loans in total portfolio loans	75.00%	73.00%
Maximum concentration of commercial real estate and commercial construction portfolio in loans	9.00%	9.00%
Financial receivable trouble debt restructuring reclassified to accruing trouble debt restructuring status	1,900,000	6,900,000
Number of TDRs returned back to accruing status	9	6
Number of loan modified	6
Commitment to lend additional funds on TDRs	0
Minimum period of loan payment defaults following restructure for TDRs to be in default	90 days
Other real estate owned properties	5
CRE and Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Combined percentage of commercial real estate and commercial construction in total commercial loans	66.00%	68.00%
Combined percentage of commercial real estate and commercial construction in total portfolio loans	49.00%	49.00%
Out-of-state exposure of combined portfolio	8.00%	7.90%
Percentage of total loans out-of-state	3.90%	3.90%
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loan modified	4
Loans modified not considered to be troubled debt restructuring	3,200,000
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loan modified	2
Loans modified not considered to be troubled debt restructuring	$ 1,200,000
Residential Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loan modified	1