Loans and Allowance for Loan Losses Credit Quality Indicators, Broken out by Portfolio Segment and Class of Financing Receivables (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	$ 10,995,268	$ 9,024,248
Software
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	4,141,358	3,293,899
Hardware
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	1,224,480	1,129,484
Venture capital/private equity
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	2,408,426	1,749,903
Life science
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	1,181,266	1,076,792
Premium wine
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	667,197	559,284
Commercial, Other
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	399,828	384,314
Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	10,022,555	8,193,676
Real estate secured loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	873,070	685,493
Consumer, Other
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	99,643	145,079
Consumer loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	972,713	830,572
Pass
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	10,371,201	8,428,907
Pass | Software
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	3,875,043	3,050,449
Pass | Hardware
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	995,055	970,802
Pass | Venture capital/private equity
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	2,408,386	1,748,663
Pass | Life science
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	1,091,993	956,276
Pass | Premium wine
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	652,747	545,697
Pass | Commercial, Other
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	383,602	360,291
Pass | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	9,406,826	7,632,178
Pass | Real estate secured loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	868,789	663,911
Pass | Consumer, Other
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	95,586	132,818
Pass | Consumer loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	964,375	796,729
Performing (Criticized)
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	572,418	557,062
Performing (Criticized) | Software
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	238,697	240,187
Performing (Criticized) | Hardware
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	209,758	136,819
Performing (Criticized) | Venture capital/private equity
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	0	1,240
Performing (Criticized) | Life science
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	87,995	120,516
Performing (Criticized) | Premium wine
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	13,008	9,189
Performing (Criticized) | Commercial, Other
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	15,536	18,608
Performing (Criticized) | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	564,994	526,559
Performing (Criticized) | Real estate secured loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	4,037	19,343
Performing (Criticized) | Consumer, Other
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	3,387	11,160
Performing (Criticized) | Consumer loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	7,424	30,503
Impaired
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	51,649	38,279
Impaired | Software
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	27,618	3,263
Impaired | Hardware
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	19,667	21,863
Impaired | Venture capital/private equity
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	40	0
Impaired | Life science
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	1,278	0
Impaired | Premium wine
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	1,442	4,398
Impaired | Commercial, Other
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	690	5,415
Impaired | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	50,735	34,939
Impaired | Real estate secured loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	244	2,239
Impaired | Consumer, Other
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	670	1,101
Impaired | Consumer loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	$ 914	$ 3,340