Aging of Gross Loans, Broken out by Portfolio Segment and Class of Financing Receivable (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	$ 79,067	$ 4,765
60 - 89 Days Past Due	7,497	3,097
Greater Than 90 Days Past Due	3,749	6,613
Total Past Due	90,313	14,475
Current	7,767,155	7,015,846
Loans Past Due 90 Days or More Still Accruing Interest	25
Commercial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	79,030	2,825
60 - 89 Days Past Due	190	1,303
Greater Than 90 Days Past Due	25
Total Past Due	79,245	4,128
Current	7,024,273	6,316,063
Loans Past Due 90 Days or More Still Accruing Interest	25
Commercial loans | Software
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	3,541	415
60 - 89 Days Past Due	66	1,006
Greater Than 90 Days Past Due	25
Total Past Due	3,632	1,421
Current	2,773,398	2,515,327
Loans Past Due 90 Days or More Still Accruing Interest	25
Commercial loans | Hardware
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	32	1,951
60 - 89 Days Past Due		45
Total Past Due	32	1,996
Current	1,083,630	954,690
Commercial loans | Venture capital/private equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	75,349	45
Total Past Due	75,349	45
Current	1,342,366	1,128,475
Commercial loans | Life science
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	35	398
60 - 89 Days Past Due	124	78
Total Past Due	159	476
Current	926,735	871,626
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	493,107	475,406
Commercial loans | Commercial Other Financing Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	73	15
Total Past Due	73	15
Current	405,037	370,539
Consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	21	590
60 - 89 Days Past Due	5,896
Total Past Due	5,917	590
Current	720,962	672,923
Consumer loans | Real estate secured loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	551,539	515,534
Consumer loans | Consumer Other Financing Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	21	590
60 - 89 Days Past Due	5,896
Total Past Due	5,917	590
Current	169,423	157,389
Total gross loans excluding impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	79,051	3,415
60 - 89 Days Past Due	6,086	1,303
Greater Than 90 Days Past Due	25
Total Past Due	85,162	4,718
Current	7,745,235	6,988,986
Loans Past Due 90 Days or More Still Accruing Interest	25
Impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
30 - 59 Days Past Due	16	1,350
60 - 89 Days Past Due	1,411	1,794
Greater Than 90 Days Past Due	3,724	6,613
Total Past Due	5,151	9,757
Current	$ 21,920	$ 26,860