Allowance for Loan Losses - Allowance for Loan Losses and the Recorded Investment in Loans by Portfolio Segment (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Jun. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Dec. 31, 2011
Financing Receivable, Allowance for Credit Losses [Line Items]
Total ending allowance balance	$ 17,848	$ 18,880	$ 18,270	$ 18,568	$ 18,374	$ 18,882
Total ending loans balance	7,919			12,904
Allowance for Loan Losses [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance For Loan Losses, Individually evaluated for impairment	1,316		1,945
Allowance For Loan Losses, Collectively evaluated for impairment	16,532		16,325
Total ending allowance balance	17,848		18,270
Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans: Individually evaluated for impairment	7,919		10,597
Loans: Collectively evaluated for impairment	1,076,651		1,183,637
Total ending loans balance	1,084,570		1,194,234
Commercial [Member] | Allowance for Loan Losses [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance For Loan Losses, Individually evaluated for impairment	1,316		1,945
Allowance For Loan Losses, Collectively evaluated for impairment	6,347		5,826
Total ending allowance balance	7,663		7,771
Commercial [Member] | Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans: Individually evaluated for impairment	7,919		10,597
Loans: Collectively evaluated for impairment	492,837		451,243
Total ending loans balance	500,756		461,840
Real Estate [Member] | Allowance for Loan Losses [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance For Loan Losses, Individually evaluated for impairment
Allowance For Loan Losses, Collectively evaluated for impairment	3,238		3,204
Total ending allowance balance	3,238		3,204
Real Estate [Member] | Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans: Individually evaluated for impairment
Loans: Collectively evaluated for impairment	189,838		190,292
Total ending loans balance	189,838		190,292
Mortgage Warehousing [Member] | Allowance for Loan Losses [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance For Loan Losses, Individually evaluated for impairment
Allowance For Loan Losses, Collectively evaluated for impairment	1,686		1,705
Total ending allowance balance	1,686		1,705
Mortgage Warehousing [Member] | Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans: Individually evaluated for impairment
Loans: Collectively evaluated for impairment	114,071		251,928
Total ending loans balance	114,071		251,928
Consumer [Member] | Allowance for Loan Losses [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance For Loan Losses, Individually evaluated for impairment
Allowance For Loan Losses, Collectively evaluated for impairment	5,261		5,590
Total ending allowance balance	5,261		5,590
Consumer [Member] | Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans: Individually evaluated for impairment
Loans: Collectively evaluated for impairment	279,905		290,174
Total ending loans balance	$ 279,905		$ 290,174