Credit Quality Indicators, Broken out by Portfolio Segment and Class of Financing Receivables (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	$ 9,024,248	$ 7,030,321
Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	8,193,676	6,335,392
Commercial loans | Software
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	3,293,899	2,517,890
Commercial loans | Hardware
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	1,129,484	961,869
Commercial loans | Venture capital/private equity
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	1,749,903	1,128,520
Commercial loans | Life science
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	1,076,792	872,413
Commercial loans | Premium wine
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	559,284	478,793
Commercial loans | Commercial Other Financing Receivable
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	384,314	375,907
Consumer loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	830,572	694,929
Consumer loans | Real estate secured loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	685,493	533,817
Consumer loans | Consumer Other Financing Receivable
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	145,079	161,112
Pass
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	8,428,907	6,434,133
Pass | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	7,632,178	5,785,972
Pass | Commercial loans | Software
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	3,050,449	2,290,497
Pass | Commercial loans | Hardware
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	970,802	839,230
Pass | Commercial loans | Venture capital/private equity
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	1,748,663	1,120,373
Pass | Commercial loans | Life science
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	956,276	748,129
Pass | Commercial loans | Premium wine
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	545,697	434,309
Pass | Commercial loans | Commercial Other Financing Receivable
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	360,291	353,434
Pass | Consumer loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	796,729	648,161
Pass | Consumer loans | Real estate secured loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	663,911	497,060
Pass | Consumer loans | Consumer Other Financing Receivable
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	132,818	151,101
Performing (Criticized)
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	557,062	559,571
Performing (Criticized) | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	526,559	534,219
Performing (Criticized) | Commercial loans | Software
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	240,187	226,251
Performing (Criticized) | Commercial loans | Hardware
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	136,819	117,456
Performing (Criticized) | Commercial loans | Venture capital/private equity
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	1,240	8,147
Performing (Criticized) | Commercial loans | Life science
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	120,516	123,973
Performing (Criticized) | Commercial loans | Premium wine
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	9,189	41,272
Performing (Criticized) | Commercial loans | Commercial Other Financing Receivable
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	18,608	17,120
Performing (Criticized) | Consumer loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	30,503	25,352
Performing (Criticized) | Consumer loans | Real estate secured loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	19,343	18,474
Performing (Criticized) | Consumer loans | Consumer Other Financing Receivable
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	11,160	6,878
Impaired
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	38,279	36,617
Impaired | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	34,939	15,201
Impaired | Commercial loans | Software
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	3,263	1,142
Impaired | Commercial loans | Hardware
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	21,863	5,183
Impaired | Commercial loans | Venture capital/private equity
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	0	0
Impaired | Commercial loans | Life science
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	0	311
Impaired | Commercial loans | Premium wine
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	4,398	3,212
Impaired | Commercial loans | Commercial Other Financing Receivable
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	5,415	5,353
Impaired | Consumer loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	3,340	21,416
Impaired | Consumer loans | Real estate secured loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	2,239	18,283
Impaired | Consumer loans | Consumer Other Financing Receivable
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	$ 1,101	$ 3,133