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, 2012	Dec. 31, 2011	Dec. 31, 2010
Financing Receivable, Impaired [Line Items]
Average impaired loans	$ 35,814	$ 37,229	$ 46,322
Commercial loans
Financing Receivable, Impaired [Line Items]
Average impaired loans	28,881	16,974	25,150
Commercial loans | Software
Financing Receivable, Impaired [Line Items]
Average impaired loans	2,223	2,575	6,153
Commercial loans | Hardware
Financing Receivable, Impaired [Line Items]
Average impaired loans	19,242	5,854	9,485
Commercial loans | Life science
Financing Receivable, Impaired [Line Items]
Average impaired loans	345	1,228	5,772
Commercial loans | Premium wine
Financing Receivable, Impaired [Line Items]
Average impaired loans	3,513	2,566	1,461
Commercial loans | Commercial Other Financing Receivable
Financing Receivable, Impaired [Line Items]
Average impaired loans	3,558	4,751	2,279
Consumer loans
Financing Receivable, Impaired [Line Items]
Average impaired loans	6,933	20,255	21,172
Consumer loans | Real estate secured loans
Financing Receivable, Impaired [Line Items]
Average impaired loans	5,037	19,179	21,055
Consumer loans | Consumer Other Financing Receivable
Financing Receivable, Impaired [Line Items]
Average impaired loans	$ 1,896	$ 1,076	$ 117