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, 2012	Dec. 31, 2011
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	$ 38,279	$ 36,617
Total unpaid principal of impaired loans	55,411	48,958
Commercial loans
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	34,939	15,201
Total unpaid principal of impaired loans	46,926	23,351
Commercial loans | Software
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	3,263	1,142
Total unpaid principal of impaired loans	4,475	1,540
Commercial loans | Hardware
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	21,863	5,183
Total unpaid principal of impaired loans	27,876	8,843
Commercial loans | Life science
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	0	311
Total unpaid principal of impaired loans	0	523
Commercial loans | Premium wine
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	4,398	3,212
Total unpaid principal of impaired loans	4,716	3,341
Commercial loans | Commercial Other Financing Receivable
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	5,415	5,353
Total unpaid principal of impaired loans	9,859	9,104
Consumer loans
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	3,340	21,416
Total unpaid principal of impaired loans	8,485	25,607
Consumer loans | Real estate secured loans
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	2,239	18,283
Total unpaid principal of impaired loans	7,185	22,410
Consumer loans | Consumer Other Financing Receivable
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	1,101	3,133
Total unpaid principal of impaired loans	1,300	3,197
Impaired loans for which there is no related allowance for loan losses
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	12,124	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	9,885	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	72	0
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	0	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	0	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	4,398	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	5,415	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	2,239	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	2,239	18,283
Impaired loans for which there is no related allowance for loan losses | Consumer loans | Consumer Other Financing Receivable
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	0	0
Impaired loans for which there is a related allowance for loan losses
Financing Receivable, Impaired [Line Items]
Carrying value of impaired loans	26,155	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	25,054	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	3,191	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	21,863	4,754
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	0	0
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	0	0
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	0	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	1,101	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	0	0
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	$ 1,101	$ 3,133