Allowance for Loan Losses Individually and Collectively Evaluated for Impairment (Detail) (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	$ 5,979	$ 6,936
Collectively Evaluated for Impairment	79,267	75,691
Software | Commercial loans
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	595	986
Collectively Evaluated for Impairment	35,770	28,302
Hardware | Commercial loans
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	1,750	1,348
Collectively Evaluated for Impairment	11,827	13,340
Venture capital/private equity | Commercial loans
Financing Receivable, Impaired [Line Items]
Collectively Evaluated for Impairment	7,810	8,241
Life science | Commercial loans
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	52	346
Collectively Evaluated for Impairment	8,112	8,731
Premium wine | Commercial loans
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	3	438
Collectively Evaluated for Impairment	4,012	5,054
Other | Commercial loans
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	1,011	122
Collectively Evaluated for Impairment	4,563	5,196
Commercial loans
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	3,411	3,240
Collectively Evaluated for Impairment	72,094	68,864
Consumer loans
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	2,568	3,696
Collectively Evaluated for Impairment	$ 7,173	$ 6,827