Composition of Loans, Net of Unearned Income, Broken Out by Portfolio Segment and Class of Financing Receivable (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012		Dec. 31, 2011
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	$ 8,192,369	[1]	$ 6,970,082	[1]
Commercial Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	7,439,393		6,274,944
Commercial Portfolio Segment [Member] | Software
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	2,952,866		2,492,849
Commercial Portfolio Segment [Member] | Hardware
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	1,192,716		952,303
Commercial Portfolio Segment [Member] | Venture capital/private equity
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	1,393,943		1,117,419
Commercial Portfolio Segment [Member] | Life science
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	1,027,693		863,737
Commercial Portfolio Segment [Member] | Premium wine
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	513,647		476,233
Commercial Portfolio Segment [Member] | Commercial Other Financing Receivable
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	358,528		372,403
Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	752,976		695,138
Consumer Portfolio Segment [Member] | Real estate secured loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	609,370	[2]	534,001	[2]
Consumer Portfolio Segment [Member] | Consumer Other Financing Receivable
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	$ 143,606		$ 161,137

[1] Included within our total loan portfolio are credit card loans of $66.2 million and $49.7 million at September 30, 2012 and December 31, 2011, respectively.

[2] Consumer loans secured by real estate at September 30, 2012 and December 31, 2011 were comprised of the following: