Loans and Allowance for Loan Losses - Composition of Loans, Net of Unearned income (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013		Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	$ 9,824,982	[1]	$ 8,946,933	[1]
Real estate secured loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	1,352,554		1,098,813
CommercialOtherFinancingReceivableexcludingPremiumWineandConsumer [Member] | Real Estate Secured Commercial Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	28,233	[2]	0	[2]
Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	8,899,413		8,116,976
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	8,306,105		7,637,721
Consumer Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	925,569		829,957
Software
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	3,698,937		3,261,489
Hardware
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	1,141,297		1,118,370
Venture capital/private equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	1,932,822		1,732,699
Life science
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	1,096,440		1,066,199
Premium wine
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	641,934		557,024
Premium wine | Non-real Estate Secured Commercial Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	149,257		143,511
Premium wine | Real Estate Secured Commercial Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	492,677	[3]	413,513	[3]
Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	387,983		381,195
Other | Commercial Loans Receivable excluding Construction and Real Estate Secured
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	287,352		315,453
Other | Construction loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	72,398		65,742
Real estate secured loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	831,644	[2]	685,300	[2]
Consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	$ 93,925		$ 144,657

[1] Included within our total loan portfolio are credit card loans of $85 million and $64 million at September 30, 2013 and December 31, 2012, respectively.

[2] Consumer loans secured by real estate at September 30, 2013 and December 31, 2012 were comprised of the following:(Dollars in thousands) September 30, 2013 December 31, 2012Loans for personal residence $643,345 $503,378Loans to eligible employees 119,371 110,584Home equity lines of credit 68,928 71,338Consumer loans secured by real estate $831,644 $685,300

[3] Included in our premium wine portfolio are gross construction loans of $132 million and $148 million at September 30, 2013 and December 31, 2012, respectively.