Loans and Allowance for Loan Losses - 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, 2013		Dec. 31, 2012
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	$ 9,622,172	[1]	$ 8,946,933	[1]
Commercial Portfolio Segment
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	8,756,728		8,116,976
Commercial Portfolio Segment | Software
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	3,558,323		3,261,489
Commercial Portfolio Segment | Hardware
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	1,205,541		1,118,370
Commercial Portfolio Segment | Venture capital/private equity
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	1,923,516		1,732,699
Commercial Portfolio Segment | Life science
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	1,084,720		1,066,199
Commercial Portfolio Segment | Premium wine
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	608,524		557,024
Commercial Portfolio Segment | Other
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	376,104		381,195
Consumer Portfolio Segment
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	865,444		829,957
Consumer Portfolio Segment | Real estate secured loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	778,482	[2]	685,300	[2]
Consumer Portfolio Segment | Consumer loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	$ 86,962		$ 144,657

[1] Included within our total loan portfolio are credit card loans of $78 million and $64 million at June 30, 2013 and December 31, 2012, respectively.

[2] Consumer loans secured by real estate at June 30, 2013 and December 31, 2012 were comprised of the following:(Dollars in thousands) June 30, 2013 December 31, 2012Loans for personal residence $593,988 $503,378Loans to eligible employees 115,974 110,584Home equity lines of credit 68,520 71,338Consumer loans secured by real estate $778,482 $685,300