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, 2016	Dec. 31, 2015
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	$ 234,460	$ 182,684
Impaired Financing Receivable, Unpaid Principal Balance	250,692	213,190
Impaired Financing Receivables With Related Allowance
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	233,370	180,592
Impaired Financing Receivables With No Related Allowance
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	1,090	2,092
Commercial loans
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	230,558	182,541
Impaired Financing Receivable, Unpaid Principal Balance	245,515	211,797
Commercial loans | Software and internet
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	122,748	100,866
Impaired Financing Receivable, Unpaid Principal Balance	129,648	125,494
Commercial loans | Hardware
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	65,395	27,736
Impaired Financing Receivable, Unpaid Principal Balance	70,683	27,869
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	38,361	51,354
Impaired Financing Receivable, Unpaid Principal Balance	41,130	55,310
Commercial loans | Premium wine
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	3,187	2,065
Impaired Financing Receivable, Unpaid Principal Balance	3,187	2,604
Commercial loans | Other
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	867	520
Impaired Financing Receivable, Unpaid Principal Balance	867	520
Commercial loans | Impaired Financing Receivables With Related Allowance
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	229,468	180,449
Commercial loans | Impaired Financing Receivables With Related Allowance | Software and internet
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	121,658	100,866
Commercial loans | Impaired Financing Receivables With Related Allowance | Hardware
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	65,395	27,736
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	38,361	50,429
Commercial loans | Impaired Financing Receivables With Related Allowance | Premium wine
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	3,187	898
Commercial loans | Impaired Financing Receivables With Related Allowance | Other
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	867	520
Commercial loans | Impaired Financing Receivables With No Related Allowance
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	1,090	2,092
Commercial loans | Impaired Financing Receivables With No Related Allowance | Software and internet
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	1,090	0
Commercial loans | Impaired Financing Receivables With No Related Allowance | Hardware
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	0	0
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	0	925
Commercial loans | Impaired Financing Receivables With No Related Allowance | Premium wine
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	0	1,167
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	3,902	143
Impaired Financing Receivable, Unpaid Principal Balance	5,177	1,393
Consumer loans | Other
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	2,398	0
Consumer loans | Real estate secured consumer loans
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	1,504	143
Impaired Financing Receivable, Unpaid Principal Balance	2,779	1,393
Consumer loans | Other Loans
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Unpaid Principal Balance	2,398	0
Consumer loans | Impaired Financing Receivables With Related Allowance
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	3,902	143
Consumer loans | Impaired Financing Receivables With Related Allowance | Real estate secured consumer loans
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	1,504	143
Consumer loans | Impaired Financing Receivables With Related Allowance | Other Loans
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	2,398	0
Consumer loans | Impaired Financing Receivables With No Related Allowance
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	0
Consumer loans | Impaired Financing Receivables With No Related Allowance | Other Loans
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	$ 0	$ 0