Average Impaired Loans, Broken out by Portfolio Segment and Class of Financing Receivable (Detail) (USD $) In Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Financing Receivable, Impaired [Line Items]
Average impaired loans	$ 39,871	$ 45,523	$ 36,879	$ 48,934
Software | Commercial loans
Financing Receivable, Impaired [Line Items]
Average impaired loans	2,562	5,583	2,652	6,521
Hardware | Commercial loans
Financing Receivable, Impaired [Line Items]
Average impaired loans	7,071	10,801	6,086	11,592
Life science | Commercial loans
Financing Receivable, Impaired [Line Items]
Average impaired loans	827	4,745	1,498	6,648
Premium wine | Commercial loans
Financing Receivable, Impaired [Line Items]
Average impaired loans	1,954	1,190	2,345	485
Other | Commercial loans
Financing Receivable, Impaired [Line Items]
Average impaired loans	7,604	2,212	4,453	2,312
Commercial loans
Financing Receivable, Impaired [Line Items]
Average impaired loans	20,018	24,531	17,034	27,558
Other | Consumer loans
Financing Receivable, Impaired [Line Items]
Average impaired loans	1,107	14	369	157
Consumer loans
Financing Receivable, Impaired [Line Items]
Average impaired loans	19,853	20,992	19,845	21,376
Consumer loans | Real estate secured loans
Financing Receivable, Impaired [Line Items]
Average impaired loans	$ 18,746	$ 20,978	$ 19,476	$ 21,219