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	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Financing Receivable, Impaired [Line Items]
Average impaired loans	$ 35,655	$ 41,419
Commercial loans
Financing Receivable, Impaired [Line Items]
Average impaired loans	34,929	37,614
Consumer loans
Financing Receivable, Impaired [Line Items]
Average impaired loans	726	3,805
Software
Financing Receivable, Impaired [Line Items]
Average impaired loans	14,677	4,114
Hardware
Financing Receivable, Impaired [Line Items]
Average impaired loans	16,020	23,632
Life science
Financing Receivable, Impaired [Line Items]
Average impaired loans	1,022	314
Premium wine
Financing Receivable, Impaired [Line Items]
Average impaired loans	1,433	4,336
Other
Financing Receivable, Impaired [Line Items]
Average impaired loans	1,777	5,218
Real estate secured loans
Financing Receivable, Impaired [Line Items]
Average impaired loans	237	2,676
Consumer loans
Financing Receivable, Impaired [Line Items]
Average impaired loans	$ 489	$ 1,129