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	Mar. 31, 2014		Dec. 31, 2013
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	$ 10,833,908	[1]	$ 10,906,386	[1]
Commercial Portfolio Segment
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	9,815,444		9,933,420
Consumer Portfolio Segment
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	1,018,464		972,966
Software
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	4,125,823		4,102,636
Hardware
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	1,193,183		1,213,032
Venture capital/private equity
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	2,201,243		2,386,054
Life science
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	1,171,258		1,170,220
Premium wine
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	701,379		664,834
Other
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	422,558		396,644
Real estate secured loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	916,998		873,255
Consumer loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	$ 101,466		$ 99,711

[1] Included within our total loan portfolio are credit card loans of $105 million and $85 million at March 31, 2014 and December 31, 2013, respectively.