Composition of Loans, Net of Unearned Income, Broken Out by Portfolio Segment and Class of Financing Receivable (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012		Dec. 31, 2011
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	$ 7,789,752	[1]	$ 6,970,082	[1]
Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	7,058,956		6,274,944
Commercial loans | Software
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	2,752,500		2,492,849
Commercial loans | Hardware
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	1,086,973		952,303
Commercial loans | Venture capital/private equity
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	1,403,801		1,117,419
Commercial loans | Life science
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	917,723		863,737
Commercial loans | Premium wine
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	493,701		476,233
Commercial loans | Commercial Other Financing Receivable
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	404,258		372,403
Consumer loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	730,796		695,138
Consumer loans | Real estate secured loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	554,266		534,001
Consumer loans | Consumer Other Financing Receivable
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	$ 176,530		$ 161,137

[1] Included within our total loan portfolio are credit card loans of $58.3 million and $49.7 million at June 30, 2012 and December 31, 2011, respectively.