Impaired Loans and Allowance for Loan Losses, Broken out by Portfolio Segment and Class of Financing Receivable (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	$ 27,071	$ 36,617
Total unpaid principal of impaired loans	41,380	48,958
Commercial loans
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	23,228	15,201
Total unpaid principal of impaired loans	32,514	23,351
Commercial loans | Software
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	2,976	1,142
Total unpaid principal of impaired loans	4,749	1,540
Commercial loans | Hardware
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	14,173	5,183
Total unpaid principal of impaired loans	17,616	8,843
Commercial loans | Life science
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans		311
Total unpaid principal of impaired loans		523
Commercial loans | Premium wine
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	3,123	3,212
Total unpaid principal of impaired loans	3,325	3,341
Commercial loans | Commercial Other Financing Receivable
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	2,956	5,353
Total unpaid principal of impaired loans	6,824	9,104
Consumer loans
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	3,843	21,416
Total unpaid principal of impaired loans	8,866	25,607
Consumer loans | Real estate secured loans
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	2,554	18,283
Total unpaid principal of impaired loans	7,460	22,410
Consumer loans | Consumer Other Financing Receivable
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	1,289	3,133
Total unpaid principal of impaired loans	1,406	3,197
Impaired loans for which there is no related allowance for loan losses
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	8,123	23,285
Impaired loans for which there is no related allowance for loan losses | Commercial loans
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	5,691	5,002
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	418
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	1,099	429
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
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	3,123	3,212
Impaired loans for which there is no related allowance for loan losses | Commercial loans | Commercial Other Financing Receivable
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	1,051	1,050
Impaired loans for which there is no related allowance for loan losses | Consumer loans
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	2,432	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	2,432	18,283
Impaired loans for which there is a related allowance for loan losses
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	18,948	13,332
Impaired loans for which there is a related allowance for loan losses | Commercial loans
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	17,537	10,199
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	2,558	1,142
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	13,074	4,754
Impaired loans for which there is a related allowance for loan losses | Commercial loans | Commercial Other Financing Receivable
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	1,905	4,303
Impaired loans for which there is a related allowance for loan losses | Consumer loans
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	1,411	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	122
Impaired loans for which there is a related allowance for loan losses | Consumer loans | Consumer Other Financing Receivable
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	$ 1,289	$ 3,133