Aging of Gross Loans, Broken out by Portfolio Segment and Class of Financing Receivable (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	$ 10,563	$ 4,765
60 - 89 Days Past Due	10,063	3,097
Greater Than 90 Days Past Due	2,288	6,613
Total Past Due	22,914	14,475
Current	9,001,334	7,015,846
Loans Past Due 90 Days or More Still Accruing Interest	19	0
Commercial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	6,551	2,825
60 - 89 Days Past Due	387	1,303
Greater Than 90 Days Past Due	19	0
Total Past Due	6,957	4,128
Current	8,151,780	6,316,063
Loans Past Due 90 Days or More Still Accruing Interest	19	0
Commercial loans | Software
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	5,890	415
60 - 89 Days Past Due	238	1,006
Greater Than 90 Days Past Due	19	0
Total Past Due	6,147	1,421
Current	3,284,489	2,515,327
Loans Past Due 90 Days or More Still Accruing Interest	19	0
Commercial loans | Hardware
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	167	1,951
60 - 89 Days Past Due	32	45
Greater Than 90 Days Past Due	0	0
Total Past Due	199	1,996
Current	1,107,422	954,690
Loans Past Due 90 Days or More Still Accruing Interest	0	0
Commercial loans | Venture capital/private equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	7	45
60 - 89 Days Past Due	0	0
Greater Than 90 Days Past Due	0	0
Total Past Due	7	45
Current	1,749,896	1,128,475
Loans Past Due 90 Days or More Still Accruing Interest	0	0
Commercial loans | Life science
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	207	398
60 - 89 Days Past Due	117	78
Greater Than 90 Days Past Due	0	0
Total Past Due	324	476
Current	1,076,468	871,626
Loans Past Due 90 Days or More Still Accruing Interest	0	0
Commercial loans | Premium wine
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	0	1
60 - 89 Days Past Due	0	174
Greater Than 90 Days Past Due	0	0
Total Past Due	0	175
Current	554,886	475,406
Loans Past Due 90 Days or More Still Accruing Interest	0	0
Commercial loans | Commercial Other Financing Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	280	15
60 - 89 Days Past Due	0	0
Greater Than 90 Days Past Due	0	0
Total Past Due	280	15
Current	378,619	370,539
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	111	590
60 - 89 Days Past Due	0	0
Greater Than 90 Days Past Due	0	0
Total Past Due	111	590
Current	827,121	672,923
Loans Past Due 90 Days or More Still Accruing Interest	0	0
Consumer loans | Real estate secured loans
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	683,254	515,534
Loans Past Due 90 Days or More Still Accruing Interest	0	0
Consumer loans | Consumer Other Financing Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	111	590
60 - 89 Days Past Due	0	0
Greater Than 90 Days Past Due	0	0
Total Past Due	111	590
Current	143,867	157,389
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	6,662	3,415
60 - 89 Days Past Due	387	1,303
Greater Than 90 Days Past Due	19	0
Total Past Due	7,068	4,718
Current	8,978,901	6,988,986
Loans Past Due 90 Days or More Still Accruing Interest	19	0
Impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	3,901	1,350
60 - 89 Days Past Due	9,676	1,794
Greater Than 90 Days Past Due	2,269	6,613
Total Past Due	15,846	9,757
Current	22,433	26,860
Loans Past Due 90 Days or More Still Accruing Interest	$ 0	$ 0