Loans and Allowance for Loan Losses - Composition of Loans, Net of Unearned income (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014		Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	$ 12,017,181	[1]	$ 10,906,386	[1]
Real estate secured loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	1,640,980		1,418,991
Software
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	4,503,369		4,102,636
Hardware
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	1,072,102		1,213,032
Venture capital/private equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	2,921,184		2,386,054
Life science
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	1,245,527		1,170,220
Premium wine
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	749,568		664,834
Premium wine | Non-real Estate Secured Commercial Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	186,675		149,841
Premium wine | Real Estate Secured Commercial Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	562,893	[2]	514,993	[2]
Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	352,069		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	241,815		288,904
Other | Construction loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	80,102		76,997
Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	10,843,819		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	10,170,672		9,310,687
Real estate secured loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	1,047,935		873,255
Real estate secured loans | Real estate secured loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	1,047,935	[3]	873,255	[3]
Other | Real Estate Secured Commercial Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	30,152		30,743
Consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	$ 125,427		$ 99,711

[1] Included within our total loan portfolio are credit card loans of $122 million and $85 million at September 30, 2014 and December 31, 2013, respectively.

[2] Included in our premium wine portfolio are gross construction loans of $111 million and $112 million at September 30, 2014 and December 31, 2013, respectively.

[3] Consumer loans secured by real estate at September 30, 2014 and December 31, 2013 were comprised of the following:(Dollars in thousands) September 30, 2014 December 31, 2013Loans for personal residence $860,024 $685,327Loans to eligible employees 129,979 121,548Home equity lines of credit 57,932 66,380Consumer loans secured by real estate $1,047,935 $873,255