Loans and Allowance for Loan Losses - Recorded Investment in Loans Modified in TDRs (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Financing Receivable, Modifications [Line Items]
Financing Receivable Modifications Recorded Investment Modified During Period	$ 11,359,000	$ 5,280,000
Loans classified as TDRs, charge-offs	3,800,000	0
Commercial Portfolio Segment
Financing Receivable, Modifications [Line Items]
Financing Receivable Modifications Recorded Investment Modified During Period	11,359,000	4,000,000
Commercial Portfolio Segment | Software and internet
Financing Receivable, Modifications [Line Items]
Financing Receivable Modifications Recorded Investment Modified During Period	10,854,000	0
Commercial Portfolio Segment | Hardware
Financing Receivable, Modifications [Line Items]
Financing Receivable Modifications Recorded Investment Modified During Period	0	4,000,000
Commercial Portfolio Segment | Premium wine
Financing Receivable, Modifications [Line Items]
Financing Receivable Modifications Recorded Investment Modified During Period	505,000	0
Consumer Portfolio Segment
Financing Receivable, Modifications [Line Items]
Financing Receivable Modifications Recorded Investment Modified During Period	0	1,280,000
Consumer Portfolio Segment | Real estate secured loans
Financing Receivable, Modifications [Line Items]
Financing Receivable Modifications Recorded Investment Modified During Period	0	$ 1,280,000
Payment Deferrals Granted [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable Modifications Recorded Investment Modified During Period	$ 2,400,000