Allowance for Loan Losses Individually and Collectively Evaluated for Impairment (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	$ 6,261	$ 3,707
Collectively Evaluated for Impairment	104,390	86,240
Commercial loans
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	6,013	2,967
Collectively Evaluated for Impairment	97,400	79,399
Commercial loans | Software
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	762	526
Collectively Evaluated for Impairment	41,886	37,737
Commercial loans | Hardware
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	5,251	1,261
Collectively Evaluated for Impairment	24,510	15,549
Commercial loans | Venture capital/private equity
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	0	0
Collectively Evaluated for Impairment	9,963	7,319
Commercial loans | Life science
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	0	0
Collectively Evaluated for Impairment	13,606	10,243
Commercial loans | Premium wine
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	0	0
Collectively Evaluated for Impairment	3,523	3,914
Commercial loans | Commercial Other Financing Receivable
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	0	1,180
Collectively Evaluated for Impairment	3,912	4,637
Consumer loans
Financing Receivable, Impaired [Line Items]
Individually Evaluated for Impairment	248	740
Collectively Evaluated for Impairment	$ 6,990	$ 6,841