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		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Financing Receivable, Impaired [Line Items]
Average impaired loans	$ 26,849	$ 41,459	$ 31,252	$ 41,441
Commercial loans
Financing Receivable, Impaired [Line Items]
Average impaired loans	26,251	36,319	30,590	36,968
Consumer loans
Financing Receivable, Impaired [Line Items]
Average impaired loans	598	5,140	662	4,473
Software
Financing Receivable, Impaired [Line Items]
Average impaired loans	15,742	5,473	15,210	4,794
Hardware
Financing Receivable, Impaired [Line Items]
Average impaired loans	6,860	24,519	11,440	24,076
Venture capital/private equity
Financing Receivable, Impaired [Line Items]
Average impaired loans	0	30	0	15
Life science
Financing Receivable, Impaired [Line Items]
Average impaired loans	552	596	787	455
Premium wine
Financing Receivable, Impaired [Line Items]
Average impaired loans	1,398	1,536	1,415	2,936
Other
Financing Receivable, Impaired [Line Items]
Average impaired loans	1,699	4,165	1,738	4,692
Real estate secured loans
Financing Receivable, Impaired [Line Items]
Average impaired loans	224	4,071	231	3,374
Consumer loans
Financing Receivable, Impaired [Line Items]
Average impaired loans	$ 374	$ 1,069	$ 431	$ 1,099