Average Impaired Loans, Broken out by Portfolio Segment and Class of Financing Receivable (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Financing Receivable, Impaired [Line Items]
Average impaired loans	$ 35,300	$ 34,993	$ 36,569	$ 35,384
Commercial loans
Financing Receivable, Impaired [Line Items]
Average impaired loans	30,485	15,436	26,228	15,543
Commercial loans | Software
Financing Receivable, Impaired [Line Items]
Average impaired loans	1,896	2,620	1,716	2,697
Commercial loans | Hardware
Financing Receivable, Impaired [Line Items]
Average impaired loans	21,468	6,662	16,865	5,594
Commercial loans | Life science
Financing Receivable, Impaired [Line Items]
Average impaired loans	88	1,170	117	1,834
Commercial loans | Premium wine
Financing Receivable, Impaired [Line Items]
Average impaired loans	3,527	1,396	3,455	2,540
Commercial loans | Commercial Other Financing Receivable
Financing Receivable, Impaired [Line Items]
Average impaired loans	3,506	3,588	4,075	2,878
Consumer loans
Financing Receivable, Impaired [Line Items]
Average impaired loans	4,815	19,557	10,341	19,841
Consumer loans | Real estate secured loans
Financing Receivable, Impaired [Line Items]
Average impaired loans	2,645	19,557	7,746	19,841
Consumer loans | Consumer Other Financing Receivable
Financing Receivable, Impaired [Line Items]
Average impaired loans	$ 2,170		$ 2,595