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	Jun. 30, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	$ 61,867	$ 159,113
Current	29,308,536	28,352,199
Loans Past Due 90 Days or More Still Accruing Interest	111	1,964
Total gross loans excluding impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	40,581	129,997
Current	29,144,299	28,211,241
Loans Past Due 90 Days or More Still Accruing Interest	111	1,964
Impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	21,286	29,116
Current	164,237	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	15,760	121,143
30 - 59 Days Past Due | Total gross loans excluding impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	13,709	118,300
30 - 59 Days Past Due | Impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	2,051	2,843
60 - 89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	31,042	10,914
60 - 89 Days Past Due | Total gross loans excluding impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	26,761	9,733
60 - 89 Days Past Due | Impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	4,281	1,181
Greater Than 90 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	15,065	27,056
Greater Than 90 Days Past Due | Total gross loans excluding impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	111	1,964
Greater Than 90 Days Past Due | Impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	14,954	25,092
Commercial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	37,227	122,726
Current	25,883,734	25,192,386
Loans Past Due 90 Days or More Still Accruing Interest	111	402
Commercial loans | Software/internet
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	25,358	35,456
Current	5,909,916	6,059,672
Loans Past Due 90 Days or More Still Accruing Interest	97	378
Commercial loans | Hardware
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	2,857	338
Current	1,318,806	1,233,956
Loans Past Due 90 Days or More Still Accruing Interest	3	4
Commercial loans | Private equity/venture capital
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	5,540	59,492
Current	14,682,798	14,054,940
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	2,284	16,918
Current	2,394,468	2,410,091
Loans Past Due 90 Days or More Still Accruing Interest	11	19
Commercial loans | Premium wine
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	821	2,967
Current	988,290	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	367	7,555
Current	589,456	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	13,649	114,341
Commercial loans | 30 - 59 Days Past Due | Software/internet
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	4,693	28,134
Commercial loans | 30 - 59 Days Past Due | Hardware
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	347	300
Commercial loans | 30 - 59 Days Past Due | Private equity/venture capital
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	5,526	59,481
Commercial loans | 30 - 59 Days Past Due | Life science/healthcare
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	1,895	16,082
Commercial loans | 30 - 59 Days Past Due | Premium wine
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	821	2,953
Commercial loans | 30 - 59 Days Past Due | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	367	7,391
Commercial loans | 60 - 89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	23,467	7,983
Commercial loans | 60 - 89 Days Past Due | Software/internet
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	20,568	6,944
Commercial loans | 60 - 89 Days Past Due | Hardware
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	2,507	34
Commercial loans | 60 - 89 Days Past Due | Private equity/venture capital
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	14	11
Commercial loans | 60 - 89 Days Past Due | Life science/healthcare
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	378	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	0	163
Commercial loans | Greater Than 90 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	111	402
Commercial loans | Greater Than 90 Days Past Due | Software/internet
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	97	378
Commercial loans | Greater Than 90 Days Past Due | Hardware
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	3	4
Commercial loans | 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 | Greater Than 90 Days Past Due | Life science/healthcare
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	11	19
Commercial loans | Greater Than 90 Days Past Due | Premium wine
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	0	0
Commercial loans | Greater Than 90 Days Past Due | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	0	1
Consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	3,354	7,271
Current	3,260,565	3,018,855
Loans Past Due 90 Days or More Still Accruing Interest	0	1,562
Consumer loans | Real estate secured loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	3,294	6,910
Current	2,796,397	2,598,496
Loans Past Due 90 Days or More Still Accruing Interest	0	1,562
Consumer loans | Other consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	60	361
Current	464,168	420,359
Loans Past Due 90 Days or More Still Accruing Interest	0	0
Consumer loans | 30 - 59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	60	3,959
Consumer loans | 30 - 59 Days Past Due | Real estate secured loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	0	3,598
Consumer loans | 30 - 59 Days Past Due | Other consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	60	361
Consumer loans | 60 - 89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	3,294	1,750
Consumer loans | 60 - 89 Days Past Due | Real estate secured loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	3,294	1,750
Consumer loans | 60 - 89 Days Past Due | Other consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	0	0
Consumer loans | Greater Than 90 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	0	1,562
Consumer loans | Greater Than 90 Days Past Due | Real estate secured loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	0	1,562
Consumer loans | Greater Than 90 Days Past Due | Other consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	$ 0	$ 0