Loans and Allowance for Loan Losses - Allowance for Loan Losses Individually and Collectively Evaluated for Impairment (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	$ 13,469	$ 6,261
Collectively Evaluated for Impairment	111,265	104,390
Commercial loans
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	13,282	6,013
Collectively Evaluated for Impairment	105,261	97,400
Consumer loans
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	187	248
Collectively Evaluated for Impairment	6,004	6,990
Software
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	705	762
Collectively Evaluated for Impairment	48,751	41,886
Hardware
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	12,392	5,251
Collectively Evaluated for Impairment	23,771	24,510
Venture capital/private equity
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	23	0
Collectively Evaluated for Impairment	14,187	9,963
Life science
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	0	0
Collectively Evaluated for Impairment	11,150	13,606
Premium wine
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	0	0
Collectively Evaluated for Impairment	3,878	3,523
Other
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	162	0
Collectively Evaluated for Impairment	$ 3,524	$ 3,912