Allowance for Loan Losses Individually and Collectively Evaluated for Impairment (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	$ 5,665	$ 3,707
Collectively Evaluated for Impairment	92,501	86,240
Commercial loans
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	5,117	2,967
Collectively Evaluated for Impairment	85,146	79,399
Commercial loans | Software
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	845	526
Collectively Evaluated for Impairment	37,136	37,737
Commercial loans | Hardware
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	4,225	1,261
Collectively Evaluated for Impairment	18,407	15,549
Commercial loans | Venture capital/private equity
Financing Receivable, Impaired [Line Items]
Collectively Evaluated for Impairment	9,652	7,319
Commercial loans | Life science
Financing Receivable, Impaired [Line Items]
Collectively Evaluated for Impairment	11,660	10,243
Commercial loans | Premium wine
Financing Receivable, Impaired [Line Items]
Collectively Evaluated for Impairment	3,396	3,914
Commercial loans | Commercial Other Financing Receivable
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	47	1,180
Collectively Evaluated for Impairment	4,895	4,637
Consumer loans
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	548	740
Collectively Evaluated for Impairment	$ 7,355	$ 6,841