Loans and Allowance for Loan Losses 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, 2013	Dec. 31, 2012	Dec. 31, 2011
Financing Receivable, Impaired [Line Items]
Average impaired loans	$ 40,846	$ 35,814	$ 37,229
Software
Financing Receivable, Impaired [Line Items]
Average impaired loans	6,254	2,223	2,575
Hardware
Financing Receivable, Impaired [Line Items]
Average impaired loans	24,508	19,242	5,854
Venture capital/private equity
Financing Receivable, Impaired [Line Items]
Average impaired loans	37	0	0
Life science
Financing Receivable, Impaired [Line Items]
Average impaired loans	334	345	1,228
Premium wine
Financing Receivable, Impaired [Line Items]
Average impaired loans	2,210	3,513	2,566
Commercial, Other
Financing Receivable, Impaired [Line Items]
Average impaired loans	3,601	3,558	4,751
Commercial loans
Financing Receivable, Impaired [Line Items]
Average impaired loans	36,944	28,881	16,974
Real estate secured loans
Financing Receivable, Impaired [Line Items]
Average impaired loans	2,957	5,037	19,179
Consumer, Other
Financing Receivable, Impaired [Line Items]
Average impaired loans	945	1,896	1,076
Consumer loans
Financing Receivable, Impaired [Line Items]
Average impaired loans	$ 3,902	$ 6,933	$ 20,255