Loans, Allowance for Loan Losses and Allowance for Unfunded Credit Commitments - Aging of Gross Loans, Broken out by Portfolio Segment and Class of Financing Receivable (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	$ 159,113	$ 199,927
Current	28,352,199	23,054,226
Loans Past Due 90 Days or More Still Accruing Interest	1,964	191
Total gross loans excluding impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	129,997	156,278
Current	28,211,241	22,923,014
Loans Past Due 90 Days or More Still Accruing Interest	1,964	191
Impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	29,116	43,649
Current	140,958	131,212
Loans Past Due 90 Days or More Still Accruing Interest	0	0
30 - 59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	121,143	111,525
30 - 59 Days Past Due | Total gross loans excluding impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	118,300	110,181
30 - 59 Days Past Due | Impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	2,843	1,344
60 - 89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	10,914	57,808
60 - 89 Days Past Due | Total gross loans excluding impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	9,733	45,906
60 - 89 Days Past Due | Impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	1,181	11,902
Equal to or Greater Than 90 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	27,056	30,594
Equal to or Greater Than 90 Days Past Due | Total gross loans excluding impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	1,964	191
Equal to or Greater Than 90 Days Past Due | Impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	25,092	30,403
Commercial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	122,726	152,786
Current	25,192,386	20,302,800
Loans Past Due 90 Days or More Still Accruing Interest	402	191
Commercial loans | Software and internet
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	35,456	20,924
Current	6,059,672	6,101,147
Loans Past Due 90 Days or More Still Accruing Interest	378	141
Commercial loans | Hardware
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	338	1,272
Current	1,233,956	1,163,278
Loans Past Due 90 Days or More Still Accruing Interest	4	50
Commercial loans | Private equity/venture capital
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	59,492	125,146
Current	14,054,940	9,835,317
Loans Past Due 90 Days or More Still Accruing Interest	0	0
Commercial loans | Life science/healthcare
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	16,918	4,581
Current	2,410,091	1,841,692
Loans Past Due 90 Days or More Still Accruing Interest	19	0
Commercial loans | Premium wine
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	2,967	418
Current	956,285	871,074
Loans Past Due 90 Days or More Still Accruing Interest	0	0
Commercial loans | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	7,555	445
Current	477,442	490,292
Loans Past Due 90 Days or More Still Accruing Interest	1	0
Commercial loans | 30 - 59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	114,341	107,221
Commercial loans | 30 - 59 Days Past Due | Software and internet
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	28,134	14,257
Commercial loans | 30 - 59 Days Past Due | Hardware
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	300	1,145
Commercial loans | 30 - 59 Days Past Due | Private equity/venture capital
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	59,481	86,566
Commercial loans | 30 - 59 Days Past Due | Life science/healthcare
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	16,082	4,390
Commercial loans | 30 - 59 Days Past Due | Premium wine
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	2,953	418
Commercial loans | 30 - 59 Days Past Due | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	7,391	445
Commercial loans | 60 - 89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	7,983	45,374
Commercial loans | 60 - 89 Days Past Due | Software and internet
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	6,944	6,526
Commercial loans | 60 - 89 Days Past Due | Hardware
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	34	77
Commercial loans | 60 - 89 Days Past Due | Private equity/venture capital
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	11	38,580
Commercial loans | 60 - 89 Days Past Due | Life science/healthcare
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	817	191
Commercial loans | 60 - 89 Days Past Due | Premium wine
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	14	0
Commercial loans | 60 - 89 Days Past Due | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	163	0
Commercial loans | Equal to or Greater Than 90 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	402	191
Commercial loans | Equal to or Greater Than 90 Days Past Due | Software and internet
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	378	141
Commercial loans | Equal to or Greater Than 90 Days Past Due | Hardware
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	4	50
Commercial loans | Equal to or Greater Than 90 Days Past Due | Private equity/venture capital
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	0	0
Commercial loans | Equal to or Greater Than 90 Days Past Due | Life science/healthcare
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	19	0
Commercial loans | Equal to or Greater Than 90 Days Past Due | Premium wine
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	0	0
Commercial loans | Equal to or Greater Than 90 Days Past Due | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	1	0
Consumer, Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	7,271	3,492
Current	3,018,855	2,620,214
Loans Past Due 90 Days or More Still Accruing Interest	1,562	0
Consumer, Other | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	361	796
Consumer, Other | Real estate secured consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	6,910	2,696
Current	2,598,496	2,292,980
Loans Past Due 90 Days or More Still Accruing Interest	1,562	0
Consumer, Other | Other Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	420,359	327,234
Loans Past Due 90 Days or More Still Accruing Interest	0	0
Consumer, Other | 30 - 59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	3,959	2,960
Consumer, Other | 30 - 59 Days Past Due | Real estate secured consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	3,598	2,164
Consumer, Other | 30 - 59 Days Past Due | Other Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	361	796
Consumer, Other | 60 - 89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	1,750	532
Consumer, Other | 60 - 89 Days Past Due | Real estate secured consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	1,750	532
Consumer, Other | 60 - 89 Days Past Due | Other Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	0	0
Consumer, Other | Equal to or Greater Than 90 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	1,562	0
Consumer, Other | Equal to or Greater Than 90 Days Past Due | Real estate secured consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	1,562	0
Consumer, Other | Equal to or Greater Than 90 Days Past Due | Other Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	$ 0	$ 0