Loans and Allowance for Loan Losses - Recorded Investment in Loans Modified in TDRs (Detail) (USD $)	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014
Financing Receivable, Modifications [Line Items]
TDRs modified within the previous 12 months that defaulted during the period	$ 30,000
Loans modified in TDRs during the period	5,280,000	[1]	12,133,000	[1]
Loans classified as TDRs, charge-offs	0
Software and internet
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	0		9,737,000
Hardware
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	4,000,000		0
Premium wine
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	0		650,000
Other
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	0		1,746,000
Commercial loans
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	4,000,000		12,133,000
Real estate secured loans
Financing Receivable, Modifications [Line Items]
TDRs modified within the previous 12 months that defaulted during the period	30,000
Loans modified in TDRs during the period	1,280,000		0
Consumer loans
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	1,280,000		0
Payment Deferrals Granted
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period			$ 9,300,000

[1] There were no partial charge-offs on loans classified as TDRs during the three months ended March 31, 2015 or March 31, 2014.