Composition of Loans, Net of Unearned Income, Broken out by Portfolio Segment and Class of Financing Receivable (Detail) (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	$ 6,328,588	$ 5,521,737
Software | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	2,299,022	1,820,680
Hardware | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	735,044	641,052
Venture capital/private equity | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	1,079,255	1,036,201
Life science | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	708,798	575,944
Premium wine | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	475,697	457,227
Other | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	351,227	436,106
Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	5,649,043	4,967,210
Other | Consumer loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	182,065	192,823
Consumer loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	679,545	554,527
Consumer loans | Real estate secured loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	$ 497,480	$ 361,704