Aging of Gross Loans, Broken out by Portfolio Segment and Class of Financing Receivable (Detail) (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	$ 20,448	$ 1,243
60 - 89 Days Past Due	304	1,971
Greater Than 90 Days Past Due	2,783	7,849
Total Past Due	23,535	11,063
Current	6,358,700	5,556,142
Loans Past Due 90 Days or More Still Accruing Interest		44
Software | Commercial loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	496	674
60 - 89 Days Past Due	38	239
Greater Than 90 Days Past Due		17
Total Past Due	534	930
Current	2,319,994	1,834,897
Loans Past Due 90 Days or More Still Accruing Interest		17
Hardware | Commercial loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	7,793	89
60 - 89 Days Past Due	5	819
Greater Than 90 Days Past Due		27
Total Past Due	7,798	935
Current	729,541	642,786
Loans Past Due 90 Days or More Still Accruing Interest		27
Venture capital/private equity | Commercial loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	500
Total Past Due	500
Current	1,090,052	1,046,696
Life science | Commercial loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	125	157
60 - 89 Days Past Due	213
Total Past Due	338	157
Current	715,246	578,208
Premium wine | Commercial loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	21
Total Past Due	21
Current	472,123	451,006
Other | Commercial loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
60 - 89 Days Past Due	48
Total Past Due	48
Current	348,262	438,345
Commercial loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	8,935	920
60 - 89 Days Past Due	304	1,058
Greater Than 90 Days Past Due		44
Total Past Due	9,239	2,022
Current	5,675,218	4,991,938
Loans Past Due 90 Days or More Still Accruing Interest		44
Other | Consumer loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	9,768
Total Past Due	9,768
Current	168,919	192,771
Consumer loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	11,513
Total Past Due	11,513
Current	645,759	533,819
Consumer loans | Real estate secured loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	1,745
Total Past Due	1,745
Current	476,840	341,048
Total gross loans excluding impaired loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	20,448	920
60 - 89 Days Past Due	304	1,058
Greater Than 90 Days Past Due		44
Total Past Due	20,752	2,022
Current	6,320,977	5,525,757
Loans Past Due 90 Days or More Still Accruing Interest		44
Impaired loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due		323
60 - 89 Days Past Due		913
Greater Than 90 Days Past Due	2,783	7,805
Total Past Due	2,783	9,041
Current	$ 37,723	$ 30,385