Allowance for Loan Losses Individually and Collectively Evaluated for Impairment (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	$ 3,707	$ 6,936
Collectively Evaluated for Impairment	86,240	75,691
Commercial loans
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	2,967	3,240
Collectively Evaluated for Impairment	79,399	68,864
Commercial loans | Software
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	526	986
Collectively Evaluated for Impairment	37,737	28,302
Commercial loans | Hardware
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	1,261	1,348
Collectively Evaluated for Impairment	15,549	13,340
Commercial loans | Venture capital/private equity
Financing Receivable, Impaired [Line Items]
Collectively Evaluated for Impairment	7,319	8,241
Commercial loans | Life science
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment		346
Collectively Evaluated for Impairment	10,243	8,731
Commercial loans | Premium wine
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment		438
Collectively Evaluated for Impairment	3,914	5,054
Commercial loans | Other
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	1,180	122
Collectively Evaluated for Impairment	4,637	5,196
Consumer loans
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	740	3,696
Collectively Evaluated for Impairment	$ 6,841	$ 6,827