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	Sep. 30, 2013	Dec. 31, 2012
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs	$ 29,273	$ 34,328
Commercial loans
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs	27,336	31,028
Consumer loans
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs	1,937	3,300
Software
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs	2,205	2,021
Hardware
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs	21,284	20,514
Venture capital/private equity
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs	88	0
Premium wine
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs	1,476	2,593
Other
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs	2,283	5,900
Real estate secured loans
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs	1,126	2,199
Consumer loans
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs	$ 811	$ 1,101