Credit Quality Indicators, Broken out by Portfolio Segment and Class of Financing Receivables (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	$ 7,030,321	$ 5,567,205
Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	6,335,392	5,012,827
Commercial loans | Software
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	2,517,890	1,839,119
Commercial loans | Hardware
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	961,869	647,545
Commercial loans | Venture capital/private equity
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	1,128,520	1,046,696
Commercial loans | Life science
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	872,413	581,777
Commercial loans | Premium wine
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	478,793	457,168
Commercial loans | Other
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	375,907	440,522
Consumer loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	694,929	554,378
Consumer loans | Real estate secured loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	533,817	361,607
Consumer loans | Other
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	161,112	192,771
Pass
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	6,434,133	5,179,227
Pass | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	5,785,972	4,660,579
Pass | Commercial loans | Software
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	2,290,497	1,717,309
Pass | Commercial loans | Hardware
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	839,230	575,401
Pass | Commercial loans | Venture capital/private equity
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	1,120,373	1,031,373
Pass | Commercial loans | Life science
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	748,129	520,596
Pass | Commercial loans | Premium wine
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	434,309	400,519
Pass | Commercial loans | Other
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	353,434	415,381
Pass | Consumer loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	648,161	518,648
Pass | Consumer loans | Real estate secured loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	497,060	337,087
Pass | Consumer loans | Other
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	151,101	181,561
Performing (Criticized)
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	559,571	348,552
Performing (Criticized) | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	534,219	333,381
Performing (Criticized) | Commercial loans | Software
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	226,251	118,518
Performing (Criticized) | Commercial loans | Hardware
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	117,456	68,320
Performing (Criticized) | Commercial loans | Venture capital/private equity
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	8,147	15,323
Performing (Criticized) | Commercial loans | Life science
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	123,973	57,769
Performing (Criticized) | Commercial loans | Premium wine
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	41,272	50,487
Performing (Criticized) | Commercial loans | Other
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	17,120	22,964
Performing (Criticized) | Consumer loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	25,352	15,171
Performing (Criticized) | Consumer loans | Real estate secured loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	18,474	3,961
Performing (Criticized) | Consumer loans | Other
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	6,878	11,210
Impaired
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	36,617	39,426
Impaired | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	15,201	18,867
Impaired | Commercial loans | Software
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	1,142	3,292
Impaired | Commercial loans | Hardware
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	5,183	3,824
Impaired | Commercial loans | Life science
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	311	3,412
Impaired | Commercial loans | Premium wine
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	3,212	6,162
Impaired | Commercial loans | Other
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	5,353	2,177
Impaired | Consumer loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	21,416	20,559
Impaired | Consumer loans | Real estate secured loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	18,283	20,559
Impaired | Consumer loans | Other
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	$ 3,133