Loans and Allowance for Loan Losses Composition of Loans, Net of Unearned income (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	$ 14,384,276	[1]	$ 10,906,386	[1]
Real estate secured loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	1,764,519		1,418,991
Software and internet
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	4,954,676		4,102,636
Hardware
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	1,131,006		1,213,032
Venture capital/private equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	4,582,906		2,386,054
Life science
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	1,289,904		1,170,220
Premium wine
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	794,321		664,834
Premium wine | Non-real Estate Secured Commercial Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	187,568		149,841
Premium wine | Real Estate Secured Commercial Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	606,753	[2]	514,993	[2]
Commercial, Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	352,828		396,644
Commercial, Other | Construction Loans Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	78,626		76,997
Commercial, Other | Commercial Loans Receivable excluding Construction and Real Estate Secured
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	234,551		288,904
Real estate, Other | Real Estate Secured Commercial Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	39,651		30,743
Consumer, Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	160,520		99,711
Real estate secured loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	1,118,115		873,255
Real estate secured loans | Real estate secured loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	1,118,115	[3]	873,255	[3]
Total consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	1,278,635		972,966
Total commercial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	13,105,641		9,933,420
Total commercial loans | Commercial Loans Receivable excluding Construction and Real Estate Secured
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	$ 12,380,611		$ 9,310,687

[1] Included within our total loan portfolio are credit card loans of $131 million and $85 million at December 31, 2014 and 2013, respectively.

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

[3] Consumer loans secured by real estate at December 31, 2014 and 2013 were comprised of the following: December 31,(Dollars in thousands) 2014 2013Loans for personal residence $918,629 $685,327Loans to eligible employees 133,568 121,548Home equity lines of credit 65,918 66,380Consumer loans secured by real estate $1,118,115 $873,255