Loans and Allowance for Loan Losses - Allowance for Loan Losses Individually and Collectively Evaluated for Impairment (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	$ 10,353	$ 6,261
Collectively Evaluated for Impairment	109,218	104,390
Commercial loans
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	10,166	6,013
Collectively Evaluated for Impairment	102,601	97,400
Commercial loans | Software
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	1,365	762
Collectively Evaluated for Impairment	45,433	41,886
Commercial loans | Hardware
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	8,756	5,251
Collectively Evaluated for Impairment	24,432	24,510
Commercial loans | Venture capital/private equity
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	45	0
Collectively Evaluated for Impairment	13,548	9,963
Commercial loans | Life science
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	0	0
Collectively Evaluated for Impairment	11,741	13,606
Commercial loans | Premium wine
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	0	0
Collectively Evaluated for Impairment	3,793	3,523
Commercial loans | Other
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	0	0
Collectively Evaluated for Impairment	3,654	3,912
Consumer loans
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	187	248
Collectively Evaluated for Impairment	$ 6,617	$ 6,990