Loans and Allowance for Loan Losses - Recorded Investment in Loans Modified in TDRs (Detail) (USD $)	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	$ 7,337,000	[1]	$ 1,969,000	[1]	$ 9,653,000	[1]	$ 16,431,000	[1]
Loans classified as TDRs, charge-offs	1,200,000		1,100,000		2,400,000		11,000,000
Commercial loans
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	7,337,000		1,969,000		9,612,000		16,039,000
Consumer loans
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	0		0		41,000		392,000
Software
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	1,007,000		1,969,000		1,007,000		1,969,000
Hardware
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	6,330,000		0		7,783,000		11,677,000
Venture capital/private equity
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	0		0		88,000		0
Premium wine
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	0		0		0		156,000
Other
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	0		0		734,000		2,237,000
Real estate secured loans
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	0		0		0		392,000
Consumer loans
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	0		0		41,000		0
Payment Deferrals Granted
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	7,300,000		2,000,000		9,600,000		6,800,000
Forgiveness Of Principal
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period							$ 9,600,000

[1] the three and nine months ended September 30, 2013, respectively. There were partial charge-offs of $1.1 million and $11.0 million, respectively, on loans classified as TDRs during the three and nine months ended September 30, 2012.