Troubled Debt Restructured Loans for Specific Segments of the Loan Portfolio (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Financing Receivable, Modifications [Line Items]
Restructured accruing	$ 1,335	$ 3,614
Restructured non-accruing	221	1,304
Balance	1,556	4,918
Specific allowance	22	1,223
Restructured and subsequently defaulted	0	0
Commercial
Financing Receivable, Modifications [Line Items]
Restructured accruing	483	2,600
Restructured non-accruing	221	0
Balance	704	2,600
Specific allowance	22	552
Restructured and subsequently defaulted	0	0
All Other
Financing Receivable, Modifications [Line Items]
Restructured accruing	0	0
Restructured non-accruing	0	1,304
Balance	0	1,304
Specific allowance	0	467
Restructured and subsequently defaulted	0	0
Commercial Portfolio Segment | Commercial Acquisition, Development and Construction
Financing Receivable, Modifications [Line Items]
Restructured accruing	0	0
Restructured non-accruing	0	0
Balance	0	0
Specific allowance	0	0
Restructured and subsequently defaulted	0	0
Commercial Portfolio Segment | Commercial Investor Real Estate
Financing Receivable, Modifications [Line Items]
Restructured accruing	852	0
Restructured non-accruing	0	0
Balance	852	0
Specific allowance	0	0
Restructured and subsequently defaulted	0	0
Commercial Portfolio Segment | Commercial Owner Occupied Real Estate
Financing Receivable, Modifications [Line Items]
Restructured accruing	0	1,014
Restructured non-accruing	0	0
Balance	0	1,014
Specific allowance	0	204
Restructured and subsequently defaulted	$ 0	$ 0