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, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	$ 191,587	$ 159,113
Current	33,136,117	28,352,199
Loans Past Due 90 Days or More Still Accruing Interest	3,515	1,964
Total gross loans excluding impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	167,213	129,997
Current	33,007,482	28,211,241
Loans Past Due 90 Days or More Still Accruing Interest	3,515	1,964
Impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	24,374	29,116
Current	128,635	140,958
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	137,375	121,143
30 - 59 Days Past Due | Total gross loans excluding impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	132,279	118,300
30 - 59 Days Past Due | Impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	5,096	2,843
60 - 89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	38,224	10,914
60 - 89 Days Past Due | Total gross loans excluding impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	31,419	9,733
60 - 89 Days Past Due | Impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	6,805	1,181
Equal to or Greater Than 90 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	15,988	27,056
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	3,515	1,964
Equal to or Greater Than 90 Days Past Due | Impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	12,473	25,092
Commercial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	160,119	122,726
Current	29,246,333	25,192,386
Loans Past Due 90 Days or More Still Accruing Interest	3,150	402
Commercial loans | Software/internet
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	24,064	35,456
Current	6,136,230	6,059,672
Loans Past Due 90 Days or More Still Accruing Interest	0	378
Commercial loans | Hardware
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	18,188	338
Current	1,357,379	1,233,956
Loans Past Due 90 Days or More Still Accruing Interest	0	4
Commercial loans | Private equity/venture capital
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	101,426	59,492
Current	17,715,964	14,054,940
Loans Past Due 90 Days or More Still Accruing Interest	3,150	0
Commercial loans | Life science/healthcare
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	8,865	16,918
Current	2,387,203	2,410,091
Loans Past Due 90 Days or More Still Accruing Interest	0	19
Commercial loans | Premium wine
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	7,543	2,967
Current	1,070,111	956,285
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	33	7,555
Current	579,446	477,442
Loans Past Due 90 Days or More Still Accruing Interest	0	1
Commercial loans | 30 - 59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	125,833	114,341
Commercial loans | 30 - 59 Days Past Due | Software/internet
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	19,839	28,134
Commercial loans | 30 - 59 Days Past Due | Hardware
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	104	300
Commercial loans | 30 - 59 Days Past Due | Private equity/venture capital
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	97,893	59,481
Commercial loans | 30 - 59 Days Past Due | Life science/healthcare
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	445	16,082
Commercial loans | 30 - 59 Days Past Due | Premium wine
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	7,543	2,953
Commercial loans | 30 - 59 Days Past Due | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	9	7,391
Commercial loans | 60 - 89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	31,136	7,983
Commercial loans | 60 - 89 Days Past Due | Software/internet
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	4,225	6,944
Commercial loans | 60 - 89 Days Past Due | Hardware
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	18,084	34
Commercial loans | 60 - 89 Days Past Due | Private equity/venture capital
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	383	11
Commercial loans | 60 - 89 Days Past Due | Life science/healthcare
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	8,420	817
Commercial loans | 60 - 89 Days Past Due | Premium wine
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	0	14
Commercial loans | 60 - 89 Days Past Due | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	24	163
Commercial loans | Equal to or Greater Than 90 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	3,150	402
Commercial loans | Equal to or Greater Than 90 Days Past Due | Software/internet
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	0	378
Commercial loans | Equal to or Greater Than 90 Days Past Due | Hardware
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	0	4
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	3,150	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	0	19
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	0	1
Consumer, Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	7,094	7,271
Current	3,761,149	3,018,855
Loans Past Due 90 Days or More Still Accruing Interest	365	1,562
Consumer, Other | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	447	361
Current	489,831	420,359
Loans Past Due 90 Days or More Still Accruing Interest	0	0
Consumer, Other | Real estate secured loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	6,647	6,910
Current	3,271,318	2,598,496
Loans Past Due 90 Days or More Still Accruing Interest	365	1,562
Consumer, Other | 30 - 59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	6,446	3,959
Consumer, Other | 30 - 59 Days Past Due | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	164	361
Consumer, Other | 30 - 59 Days Past Due | Real estate secured loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	6,282	3,598
Consumer, Other | 60 - 89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	283	1,750
Consumer, Other | 60 - 89 Days Past Due | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	283	0
Consumer, Other | 60 - 89 Days Past Due | Real estate secured loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	0	1,750
Consumer, Other | Equal to or Greater Than 90 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	365	1,562
Consumer, Other | Equal to or Greater Than 90 Days Past Due | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	0	0
Consumer, Other | Equal to or Greater Than 90 Days Past Due | Real estate secured loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	$ 365	$ 1,562