Loans and Allowance for Loan Losses - Impaired Loans and Allowance for Loan Losses, Broken out by Portfolio Segment and Class of Financing Receivable (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	$ 182,684	$ 38,137
Impaired Financing Receivable, Unpaid Principal Balance	213,190	42,899
Impaired Financing Receivables With Related Allowance
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	180,592	35,523
Impaired Financing Receivables With No Related Allowance
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	2,092	2,614
Commercial loans
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	182,541	37,820
Impaired Financing Receivable, Unpaid Principal Balance	211,797	41,182
Commercial loans | Software and internet
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	100,866	33,287
Impaired Financing Receivable, Unpaid Principal Balance	125,494	34,218
Commercial loans | Hardware
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	27,736	2,521
Impaired Financing Receivable, Unpaid Principal Balance	27,869	2,535
Commercial loans | Private equity/venture capital
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	0	0
Impaired Financing Receivable, Unpaid Principal Balance	0	0
Commercial loans | Life science/healthcare
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	51,354	475
Impaired Financing Receivable, Unpaid Principal Balance	55,310	2,453
Commercial loans | Premium wine
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	2,065	1,304
Impaired Financing Receivable, Unpaid Principal Balance	2,604	1,743
Commercial loans | Other
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	520	233
Impaired Financing Receivable, Unpaid Principal Balance	520	233
Commercial loans | Impaired Financing Receivables With Related Allowance
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	180,449	35,398
Commercial loans | Impaired Financing Receivables With Related Allowance | Software and internet
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	100,866	33,287
Commercial loans | Impaired Financing Receivables With Related Allowance | Hardware
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	27,736	1,403
Commercial loans | Impaired Financing Receivables With Related Allowance | Private equity/venture capital
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	0	0
Commercial loans | Impaired Financing Receivables With Related Allowance | Life science/healthcare
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	50,429	475
Commercial loans | Impaired Financing Receivables With Related Allowance | Premium wine
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	898	0
Commercial loans | Impaired Financing Receivables With Related Allowance | Other
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	520	233
Commercial loans | Impaired Financing Receivables With No Related Allowance
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	2,092	2,422
Commercial loans | Impaired Financing Receivables With No Related Allowance | Software and internet
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	0	0
Commercial loans | Impaired Financing Receivables With No Related Allowance | Hardware
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	0	1,118
Commercial loans | Impaired Financing Receivables With No Related Allowance | Private equity/venture capital
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	0	0
Commercial loans | Impaired Financing Receivables With No Related Allowance | Life science/healthcare
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	925	0
Commercial loans | Impaired Financing Receivables With No Related Allowance | Premium wine
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	1,167	1,304
Commercial loans | Impaired Financing Receivables With No Related Allowance | Other
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	0	0
Consumer loans
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	143	317
Impaired Financing Receivable, Unpaid Principal Balance	1,393	1,717
Consumer loans | Other
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	0	125
Impaired Financing Receivable, Unpaid Principal Balance	0	305
Consumer loans | Real estate secured consumer loans
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	143	192
Impaired Financing Receivable, Unpaid Principal Balance	1,393	1,412
Consumer loans | Impaired Financing Receivables With Related Allowance
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	143	125
Consumer loans | Impaired Financing Receivables With Related Allowance | Other
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	0	125
Consumer loans | Impaired Financing Receivables With Related Allowance | Real estate secured consumer loans
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	143	0
Consumer loans | Impaired Financing Receivables With No Related Allowance
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	0	192
Consumer loans | Impaired Financing Receivables With No Related Allowance | Other
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	0	0
Consumer loans | Impaired Financing Receivables With No Related Allowance | Real estate secured consumer loans
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	$ 0	$ 192