Aging of Gross Loans, Broken out by Portfolio Segment and Class of Financing Receivable (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	$ 4,765	$ 1,243
60 - 89 Days Past Due	3,097	1,971
Greater Than 90 Days Past Due	6,613	7,849
Total Past Due	14,475	11,063
Current	7,015,846	5,556,142
Loans Past Due 90 Days or More Still Accruing Interest		44
Commercial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	2,825	920
60 - 89 Days Past Due	1,303	1,058
Greater Than 90 Days Past Due		44
Total Past Due	4,128	2,022
Current	6,316,063	4,991,938
Loans Past Due 90 Days or More Still Accruing Interest		44
Commercial loans | Software
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	415	674
60 - 89 Days Past Due	1,006	239
Greater Than 90 Days Past Due		17
Total Past Due	1,421	930
Current	2,515,327	1,834,897
Loans Past Due 90 Days or More Still Accruing Interest		17
Commercial loans | Hardware
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	1,951	89
60 - 89 Days Past Due	45	819
Greater Than 90 Days Past Due		27
Total Past Due	1,996	935
Current	954,690	642,786
Loans Past Due 90 Days or More Still Accruing Interest		27
Commercial loans | Venture capital/private equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	45
Total Past Due	45
Current	1,128,475	1,046,696
Commercial loans | Life science
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	398	157
60 - 89 Days Past Due	78
Total Past Due	476	157
Current	871,626	578,208
Commercial loans | Premium wine
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	1
60 - 89 Days Past Due	174
Total Past Due	175
Current	475,406	451,006
Commercial loans | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	15
Total Past Due	15
Current	370,539	438,345
Consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	590
Total Past Due	590
Current	672,923	533,819
Consumer loans | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	590
Total Past Due	590
Current	157,389	192,771
Consumer loans | Real estate secured loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	515,534	341,048
Total gross loans excluding impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	3,415	920
60 - 89 Days Past Due	1,303	1,058
Greater Than 90 Days Past Due		44
Total Past Due	4,718	2,022
Current	6,988,986	5,525,757
Loans Past Due 90 Days or More Still Accruing Interest		44
Impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	1,350	323
60 - 89 Days Past Due	1,794	913
Greater Than 90 Days Past Due	6,613	7,805
Total Past Due	9,757	9,041
Current	$ 26,860	$ 30,385