Loans and Allowance for Loan Losses - Composition of Loans, Net of Unearned income (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	$ 10,833,908	[1]	$ 10,906,386	[1]
Real estate secured loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	1,487,739		1,418,991
CommercialOtherFinancingReceivableexcludingPremiumWineandConsumer [Member] | Real Estate Secured Commercial Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	30,548		30,743
Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	9,815,444		9,933,420
Commercial Portfolio Segment | Commercial Loans Receivable excluding Construction and Real Estate Secured
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	9,146,290		9,310,687
Consumer Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	1,018,464		972,966
Software
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	4,125,823		4,102,636
Hardware
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	1,193,183		1,213,032
Venture capital/private equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	2,201,243		2,386,054
Life science
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	1,171,258		1,170,220
Premium wine
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	701,379		664,834
Premium wine | Non-real Estate Secured Commercial Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	161,186		149,841
Premium wine | Real Estate Secured Commercial Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	540,193	[2]	514,993	[2]
Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	422,558		396,644
Other | Commercial Loans Receivable excluding Construction and Real Estate Secured
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	293,597		288,904
Other | Construction loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	98,413		76,997
Real estate secured loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	916,998		873,255
Real estate secured loans | Real estate secured loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	916,998	[3]	873,255	[3]
Consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	$ 101,466		$ 99,711

[1] Included within our total loan portfolio are credit card loans of $105 million and $85 million at March 31, 2014 and December 31, 2013, respectively.

[2] Included in our premium wine portfolio are gross construction loans of $112 million at both March 31, 2014 and December 31, 2013, respectively.

[3] Consumer loans secured by real estate at March 31, 2014 and December 31, 2013 were comprised of the following:(Dollars in thousands) March 31, 2014 December 31, 2013Loans for personal residence $724,797 $685,327Loans to eligible employees 123,062 121,548Home equity lines of credit 69,139 66,380Consumer loans secured by real estate $916,998 $873,255