Average Impaired Loans, Broken out by Portfolio Segment and Class of Financing Receivable (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Financing Receivable, Impaired [Line Items]
Average impaired loans	$ 37,229	$ 46,322
Commercial loans
Financing Receivable, Impaired [Line Items]
Average impaired loans	16,974	25,150
Commercial loans | Software
Financing Receivable, Impaired [Line Items]
Average impaired loans	2,575	6,153
Commercial loans | Hardware
Financing Receivable, Impaired [Line Items]
Average impaired loans	5,854	9,485
Commercial loans | Life science
Financing Receivable, Impaired [Line Items]
Average impaired loans	1,228	5,772
Commercial loans | Premium wine
Financing Receivable, Impaired [Line Items]
Average impaired loans	2,566	1,461
Commercial loans | Other
Financing Receivable, Impaired [Line Items]
Average impaired loans	4,751	2,279
Consumer loans
Financing Receivable, Impaired [Line Items]
Average impaired loans	20,255	21,172
Consumer loans | Other
Financing Receivable, Impaired [Line Items]
Average impaired loans	1,076	117
Consumer loans | Real estate secured loans
Financing Receivable, Impaired [Line Items]
Average impaired loans	$ 19,179	$ 21,055