Loans and Loans Held for Sale - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014 TDRs	Sep. 30, 2013 TDRs	Sep. 30, 2014 TDRs Property SecurityLoan	Sep. 30, 2013 TDRs	Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unearned income on loans	$ 2,000,000		$ 2,000,000		$ 1,300,000
Percentage of commercial loans in total portfolio loans	74.00%		74.00%		73.00%
Maximum concentration of commercial real estate and commercial construction portfolio in loans (in excess of)	9.00%		9.00%		9.00%
Number of TDRs returned back to accruing status	5	0	10	1
Financial receivable trouble debt restructuring reclassified to accruing trouble debt restructuring status	500,000		2,000,000	200,000
Number of loans modified not considered to be troubled debt restructuring			5
Commitment to lend additional funds on TDRs	0		0
Minimum period of loan payment defaults following restructure for TDRs to be in default			90 days
Other real estate owned properties			3
Commercial Real Estate 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%		66.00%		68.00%
Combined percentage of commercial real estate and commercial construction in total portfolio loans	49.00%		49.00%		49.00%
Out-of-state exposure of combined portfolio excluding contiguous states	7.70%		7.70%		7.90%
Percentage of total loans out-of-state excluding contiguous states	3.80%		3.80%		3.90%
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans modified not considered to be troubled debt restructuring	2		3
Loans modified not considered to be troubled debt restructuring	2,800,000		3,200,000
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans modified not considered to be troubled debt restructuring			2
Loans modified not considered to be troubled debt restructuring			$ 1,200,000