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	Jun. 30, 2013	Dec. 31, 2012
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs	$ 34,280	$ 34,328
Commercial loans
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs	31,953	31,028
Commercial loans | Software
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs	2,251	2,021
Commercial loans | Hardware
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs	23,318	20,514
Commercial loans | Venture capital/private equity
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs	676	0
Commercial loans | Premium wine
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs	1,511	2,593
Commercial loans | Other
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs	4,197	5,900
Consumer loans
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs	2,327	3,300
Consumer loans | Real estate secured loans
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs	1,373	2,199
Consumer loans | Consumer loans
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs	$ 954	$ 1,101