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, 2014		Dec. 31, 2013
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	$ 12,017,181	[1]	$ 10,906,386	[1]
Software
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	4,503,369		4,102,636
Hardware
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	1,072,102		1,213,032
Venture capital/private equity
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	2,921,184		2,386,054
Life science
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	1,245,527		1,170,220
Premium wine
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	749,568		664,834
Other
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	352,069		396,644
Commercial Portfolio Segment
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	10,843,819		9,933,420
Real estate secured loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	1,047,935		873,255
Consumer loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	125,427		99,711
Consumer Portfolio Segment
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	$ 1,173,362		$ 972,966

[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.