Credit Quality Indicators, Broken out by Portfolio Segment and Class of Financing Receivables (Detail) (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	$ 6,382,235	$ 5,567,205
Software | Pass | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	2,139,282	1,717,309
Hardware | Pass | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	677,590	575,401
Venture capital/private equity | Pass | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	1,084,298	1,031,373
Life science | Pass | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	609,348	520,596
Premium wine | Pass | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	432,698	400,519
Other | Pass | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	335,031	415,381
Other | Pass | Consumer loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	170,172	181,561
Pass
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	5,919,845	5,179,227
Pass | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	5,278,247	4,660,579
Pass | Consumer loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	641,598	518,648
Pass | Consumer loans | Real estate secured loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	471,426	337,087
Software | Performing (Criticized) | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	181,246	118,518
Hardware | Performing (Criticized) | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	59,749	68,320
Venture capital/private equity | Performing (Criticized) | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	6,254	15,323
Life science | Performing (Criticized) | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	106,236	57,769
Premium wine | Performing (Criticized) | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	39,446	50,487
Other | Performing (Criticized) | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	13,279	22,964
Other | Performing (Criticized) | Consumer loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	8,515	11,210
Performing (Criticized)
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	421,884	348,552
Performing (Criticized) | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	406,210	333,381
Performing (Criticized) | Consumer loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	15,674	15,171
Performing (Criticized) | Consumer loans | Real estate secured loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	7,159	3,961
Software | Impaired | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	2,559	3,292
Hardware | Impaired | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	5,398	3,824
Life science | Impaired | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	633	3,412
Premium wine | Impaired | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	3,257	6,162
Other | Impaired | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	6,593	2,177
Other | Impaired | Consumer loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	3,322
Impaired
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	40,506	39,426
Impaired | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	18,440	18,867
Impaired | Consumer loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	22,066	20,559
Impaired | Consumer loans | Real estate secured loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	18,744	20,559
Software | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	2,323,087	1,839,119
Hardware | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	742,737	647,545
Venture capital/private equity | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	1,090,552	1,046,696
Life science | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	716,217	581,777
Premium wine | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	475,401	457,168
Other | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	354,903	440,522
Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	5,702,897	5,012,827
Other | Consumer loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	182,009	192,771
Consumer loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	679,338	554,378
Consumer loans | Real estate secured loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	$ 497,329	$ 361,607