Impaired Loans and Allowance for Loan Losses, Broken out by Portfolio Segment and Class of Financing Receivable (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	$ 36,617	$ 39,426
Total unpaid principal of impaired loans	48,958	46,981
Commercial loans
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	15,201	18,867
Total unpaid principal of impaired loans	23,351	23,551
Commercial loans | Software
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	1,142	3,292
Total unpaid principal of impaired loans	1,540	5,332
Commercial loans | Hardware
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	5,183	3,824
Total unpaid principal of impaired loans	8,843	3,931
Commercial loans | Life science
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	311	3,412
Total unpaid principal of impaired loans	523	4,369
Commercial loans | Premium wine
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	3,212	6,162
Total unpaid principal of impaired loans	3,341	7,129
Commercial loans | Other
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	5,353	2,177
Total unpaid principal of impaired loans	9,104	2,790
Consumer loans
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	21,416	20,559
Total unpaid principal of impaired loans	25,607	23,430
Consumer loans | Other
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	3,133
Total unpaid principal of impaired loans	3,197
Consumer loans | Real estate secured loans
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	18,283	20,559
Total unpaid principal of impaired loans	22,410	23,430
Impaired loans for which there is no related allowance for loan losses
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	23,285	6,189
Impaired loans for which there is no related allowance for loan losses | Commercial loans
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	5,002	6,189
Impaired loans for which there is no related allowance for loan losses | Commercial loans | Software
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans		334
Impaired loans for which there is no related allowance for loan losses | Commercial loans | Hardware
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	429	307
Impaired loans for which there is no related allowance for loan losses | Commercial loans | Life science
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	311	1,362
Impaired loans for which there is no related allowance for loan losses | Commercial loans | Premium wine
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	3,212	3,167
Impaired loans for which there is no related allowance for loan losses | Commercial loans | Other
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	1,050	1,019
Impaired loans for which there is no related allowance for loan losses | Consumer loans
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	18,283
Impaired loans for which there is no related allowance for loan losses | Consumer loans | Real estate secured loans
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	18,283
Impaired loans for which there is a related allowance for loan losses
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	13,332	33,237
Impaired loans for which there is a related allowance for loan losses | Commercial loans
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	10,199	12,678
Impaired loans for which there is a related allowance for loan losses | Commercial loans | Software
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	1,142	2,958
Impaired loans for which there is a related allowance for loan losses | Commercial loans | Hardware
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	4,754	3,517
Impaired loans for which there is a related allowance for loan losses | Commercial loans | Life science
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans		2,050
Impaired loans for which there is a related allowance for loan losses | Commercial loans | Premium wine
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans		2,995
Impaired loans for which there is a related allowance for loan losses | Commercial loans | Other
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	4,303	1,158
Impaired loans for which there is a related allowance for loan losses | Consumer loans
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	3,133	20,559
Impaired loans for which there is a related allowance for loan losses | Consumer loans | Other
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	3,133
Impaired loans for which there is a related allowance for loan losses | Consumer loans | Real estate secured loans
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans		$ 20,559