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	Sep. 30, 2013		Dec. 31, 2012
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	$ 9,824,982	[1]	$ 8,946,933	[1]
Commercial Portfolio Segment
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	8,899,413		8,116,976
Consumer Portfolio Segment
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	925,569		829,957
Software
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	3,698,937		3,261,489
Hardware
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	1,141,297		1,118,370
Venture capital/private equity
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	1,932,822		1,732,699
Life science
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	1,096,440		1,066,199
Premium wine
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	641,934		557,024
Other
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	387,983		381,195
Real estate secured loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	831,644	[2]	685,300	[2]
Consumer loans
Financing Receivable, Recorded Investment [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