Loans and Allowance for Loan Losses Aging of Gross Loans, Broken out by Portfolio Segment and Class of Financing Receivable (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	$ 19,367	$ 10,563
60 - 89 Days Past Due	12,572	10,063
Greater Than 90 Days Past Due	4,438	2,288
Total Past Due	36,377	22,914
Current	10,958,891	9,001,334
Loans Past Due 90 Days or More Still Accruing Interest	99	19
Software
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	9,804	5,890
60 - 89 Days Past Due	1,291	238
Greater Than 90 Days Past Due	99	19
Total Past Due	11,194	6,147
Current	4,102,546	3,284,489
Loans Past Due 90 Days or More Still Accruing Interest	99	19
Hardware
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	2,679	167
60 - 89 Days Past Due	3,965	32
Greater Than 90 Days Past Due	0	0
Total Past Due	6,644	199
Current	1,198,169	1,107,422
Loans Past Due 90 Days or More Still Accruing Interest	0	0
Venture capital/private equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	4	7
60 - 89 Days Past Due	0	0
Greater Than 90 Days Past Due	0	0
Total Past Due	4	7
Current	2,408,382	1,749,896
Loans Past Due 90 Days or More Still Accruing Interest	0	0
Life science
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	395	207
60 - 89 Days Past Due	131	117
Greater Than 90 Days Past Due	0	0
Total Past Due	526	324
Current	1,179,462	1,076,468
Loans Past Due 90 Days or More Still Accruing Interest	0	0
Premium wine
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	0	0
60 - 89 Days Past Due	0	0
Greater Than 90 Days Past Due	0	0
Total Past Due	0	0
Current	665,755	554,886
Loans Past Due 90 Days or More Still Accruing Interest	0	0
Commercial, Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	1,580	280
60 - 89 Days Past Due	142	0
Greater Than 90 Days Past Due	0	0
Total Past Due	1,722	280
Current	397,416	378,619
Loans Past Due 90 Days or More Still Accruing Interest	0	0
Commercial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	14,462	6,551
60 - 89 Days Past Due	5,529	387
Greater Than 90 Days Past Due	99	19
Total Past Due	20,090	6,957
Current	9,951,730	8,151,780
Loans Past Due 90 Days or More Still Accruing Interest	99	19
Real estate secured loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	240	0
60 - 89 Days Past Due	0	0
Greater Than 90 Days Past Due	0	0
Total Past Due	240	0
Current	872,586	683,254
Loans Past Due 90 Days or More Still Accruing Interest	0	0
Consumer, Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	8	111
60 - 89 Days Past Due	0	0
Greater Than 90 Days Past Due	0	0
Total Past Due	8	111
Current	98,965	143,867
Loans Past Due 90 Days or More Still Accruing Interest	0	0
Consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	248	111
60 - 89 Days Past Due	0	0
Greater Than 90 Days Past Due	0	0
Total Past Due	248	111
Current	971,551	827,121
Loans Past Due 90 Days or More Still Accruing Interest	0	0
Total gross loans excluding impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	14,710	6,662
60 - 89 Days Past Due	5,529	387
Greater Than 90 Days Past Due	99	19
Total Past Due	20,338	7,068
Current	10,923,281	8,978,901
Loans Past Due 90 Days or More Still Accruing Interest	99	19
Impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	4,657	3,901
60 - 89 Days Past Due	7,043	9,676
Greater Than 90 Days Past Due	4,339	2,269
Total Past Due	16,039	15,846
Current	35,610	22,433
Loans Past Due 90 Days or More Still Accruing Interest	$ 0	$ 0