Loans and Allowance for Loan Losses - Summary of Loans Modified in Troubled Debt Restructurings ("TDRs") by Portfolio Segment and Class of Financing Receivables (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015 troubled_debt_restructuring		Mar. 31, 2014		Dec. 31, 2014
Financing Receivable, Modifications [Line Items]
Number of troubled debt restructurings	9
Loans modified in TDRs	$ 10,588				$ 7,151
Loans modified in TDRs during the period	5,280	[1]	12,133	[1]
Software and internet
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs	2,707				3,784
Loans modified in TDRs during the period	0		9,737
Hardware
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs	4,510				1,118
Loans modified in TDRs during the period	4,000		0
Premium wine
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs	1,830				1,891
Loans modified in TDRs during the period	0		650
Other
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs	191				233
Loans modified in TDRs during the period	0		1,746
Commercial loans
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs	9,238				7,026
Loans modified in TDRs during the period	4,000		12,133
Real estate secured loans
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	1,280		0
Consumer loans
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs	1,350				125
Consumer loans
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs	1,350				125
Loans modified in TDRs during the period	1,280		0
Payment Deferrals Granted
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period			9,300
Forgiveness of Principal
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period			$ 2,800

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