Credit Quality Indicators, Broken out by Portfolio Segment and Class of Financing Receivables (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	$ 7,857,468	$ 7,030,321
Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	7,126,746	6,335,392
Commercial loans | Software
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	2,780,006	2,517,890
Commercial loans | Hardware
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	1,097,835	961,869
Commercial loans | Venture capital/private equity
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	1,417,715	1,128,520
Commercial loans | Life science
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	926,894	872,413
Commercial loans | Premium wine
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	496,230	478,793
Commercial loans | Commercial Other Financing Receivable
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	408,066	375,907
Consumer loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	730,722	694,929
Consumer loans | Real estate secured loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	554,093	533,817
Consumer loans | Consumer Other Financing Receivable
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	176,629	161,112
Pass
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	7,313,297	6,434,133
Pass | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	6,619,890	5,785,972
Pass | Commercial loans | Software
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	2,573,437	2,290,497
Pass | Commercial loans | Hardware
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	951,026	839,230
Pass | Commercial loans | Venture capital/private equity
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	1,417,715	1,120,373
Pass | Commercial loans | Life science
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	820,392	748,129
Pass | Commercial loans | Premium wine
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	481,162	434,309
Pass | Commercial loans | Commercial Other Financing Receivable
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	376,158	353,434
Pass | Consumer loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	693,407	648,161
Pass | Consumer loans | Real estate secured loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	530,017	497,060
Pass | Consumer loans | Consumer Other Financing Receivable
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	163,390	151,101
Performing (Criticized)
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	517,100	559,571
Performing (Criticized) | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	483,628	534,219
Performing (Criticized) | Commercial loans | Software
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	203,593	226,251
Performing (Criticized) | Commercial loans | Hardware
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	132,636	117,456
Performing (Criticized) | Commercial loans | Venture capital/private equity
Financing Receivable, Recorded Investment [Line Items]
Financing receivable		8,147
Performing (Criticized) | Commercial loans | Life science
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	106,502	123,973
Performing (Criticized) | Commercial loans | Premium wine
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	11,945	41,272
Performing (Criticized) | Commercial loans | Commercial Other Financing Receivable
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	28,952	17,120
Performing (Criticized) | Consumer loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	33,472	25,352
Performing (Criticized) | Consumer loans | Real estate secured loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	21,522	18,474
Performing (Criticized) | Consumer loans | Consumer Other Financing Receivable
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	11,950	6,878
Impaired
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	27,071	36,617
Impaired | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	23,228	15,201
Impaired | Commercial loans | Software
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	2,976	1,142
Impaired | Commercial loans | Hardware
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	14,173	5,183
Impaired | Commercial loans | Life science
Financing Receivable, Recorded Investment [Line Items]
Financing receivable		311
Impaired | Commercial loans | Premium wine
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	3,123	3,212
Impaired | Commercial loans | Commercial Other Financing Receivable
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	2,956	5,353
Impaired | Consumer loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	3,843	21,416
Impaired | Consumer loans | Real estate secured loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	2,554	18,283
Impaired | Consumer loans | Consumer Other Financing Receivable
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	$ 1,289	$ 3,133