Loans and Allowance for Loan Losses - Recorded Investment in Loans Modified in TDRs (Detail) (USD $)	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	$ 12,133,000	[1]	$ 1,375,000	[1]
Loans classified as TDRs, charge-offs	0
Commercial loans
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	12,133,000		1,275,000
Consumer loans
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	0		100,000
Software
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	9,737,000		0
Venture capital/private equity
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	0		821,000
Life science
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	0		454,000
Premium wine
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	650,000		0
Other
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	1,746,000		0
Consumer loans
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	0		100,000
Payment Deferrals Granted
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	9,300,000		1,400,000
Forgiveness Of Principal
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	$ 2,800,000

[1] the three months ended March 31, 2014 or March 31, 2013.